Prostate Cancer Risk Research Articles

Drug-target Mendelian randomization revealed a significant association of genetically proxied metformin effects with increased prostate cancer risk.

The association between metformin use and risk of prostate cancer remains controversial, while data from randomized trials is lacking. We aim to evaluate the association of genetically proxied metformin effects with prostate cancer risk using a drug-target Mendelian randomization (MR) approach. Summary statistics for prostate cancer were obtained from the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome Consortium (79,148 cases and 61,106 controls). Cis-expression quantitative trait loci (cis-eQTL) variants in the gene targets of metformin were identified in the GTEx project and eQTLGen consortium. We also obtained male-specific genome-wide association study data for type 2 diabetes, body mass index (BMI), total testosterone, bioavailable testosterone, estradiol, and sex hormone binding globulin for mediation analysis. Inverse-variance weighted (IVW) regression, weighted median, MR-Egger regression, and MR-PRESSO were performed in the main MR analysis. Multivariable MR was used to identify potential mediators and genetic colocalization analysis was performed to assess any shared genetic basis between two traits of interest. We found that genetically proxied metformin effects (1-SD HbA1creduction, equivalent to 6.75 mmol/mol) were associated with higher risk of prostate cancer (odds ratioIVW [ORIVW]: 1.55, 95% confidence interval,CI: 1.23-1.96, p = 3.0 × 10-3). Two metformin targets, mitochondrial complex I (ORIVW: 1.48, 95%CI: 1.07-2.03, p = 0.016) and gamma-secretase complex (ORIVW: 2.58, 95%CI:1.47-4.55, p = 0.001), showed robust associations with prostate cancer risk, and their effects were partly mediated through BMI (16.4%) and total testosterone levels (34.3%), respectively. These results were further supported by colocalization analysis that expressions of NDUFA13 and BMI, APH1A, and total testosterone may be influenced by shared genetic factors, respectively. In summary, our study indicated that genetically proxied metformin effects may be associated with an increased risk of prostate cancer. Repurposing metformin for prostate cancer prevention in general populations is not supported by our findings.

Abstract 2203: Dietary patterns and prostate cancer risk in the Multiethnic Cohort Study

Abstract Background: A growing body of research has shown the benefits of a healthy diet on a variety of cancer outcomes. Evidence is inconsistent for prostate cancer and research in diverse populations is limited. Methods: In the Multiethnic Cohort Study (MEC), we conducted a prospective cohort analysis to investigate the association of four diet quality indices (DQIs; AHEI-2010, aMED, HEI-2015, DASH; a higher score indicates healthier diet), three plant-based diet indices (PDI, hPDI, uPDI), two inflammatory (DII, EDIP), and two insulinemic dietary indices (EDIH, EDIR) (a higher score indicates more pro-inflammatory or pro-insulinemic diet) with incidence of prostate cancer (PCa) in 79,930 men from five racial/ethnic groups (White, African American, Japanese American, Latino, and Native Hawaiian). All dietary scores were constructed from a baseline quantitative food frequency questionnaire. Outcomes examined included total PCa, high-grade PCa (Gleason score > 7), advanced PCa (regional or distant), aggressive PCa (high-grade or advanced), and lethal PCa (distant or death due to PCa). Hazard ratios (HR) and 95% confidence intervals (CI) per one standard deviation (SD) increase in the dietary score were estimated from Cox proportional hazards models, overall and by race/ethnicity. Associations were considered nominally significant at P < 0.05. Results: During a mean follow-up of 18.9 years, a total of 9,759 incident PCa cases were identified, including 2,503 high-grade, 1,706 advanced, 3,430 aggressive, and 1,426 lethal PCa cases. None of the dietary scores was significantly associated with total PCa. We found a significant association between DII and advanced PCa (HR=1.08, 95% CI=1.01-1.15) overall and the association appeared to be the strongest in African Americans (HR=1.17, 95% CI=1.00-1.36) and Native Hawaiians (HR=1.29, 95% CI=0.98-1.68). We also observed weak associations of the four DQIs with advanced PCa (HR of 0.95-0.96, P of 0.07-0.10) in the overall population, among which a higher DASH score was significantly associated with a 15% (95% CI = 0.75-0.96) lower risk of advanced PCa in African Americans. In addition, we observed that several inflammatory (EDIP) and insulinemic (EDIH, EDIR) dietary scores were associated with lower incidence of advanced, aggressive, or lethal PCa (HR=0.89-0.95, P of 0.03-0.05), which requires further investigation. Conclusions: Our findings suggest that diets with high proinflammatory potential may increase risk of advanced PCa while following a healthy dietary pattern may reduce the risk of advanced PCa. Further studies are needed to better understand the inconsistent results across studies on diet and PCa risk and whether our findings can be replicated in other populations. Citation Format: Wei Xiong, Song-Yi Park, Anqi Wang, Peggy Wan, Lynne R. Wilkens, Loïc Le Marchand, Christopher A. Haiman, Fei Chen. Dietary patterns and prostate cancer risk in the Multiethnic Cohort Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2203.

Abstract 3430: Mosaic loss of the Y chromosome is associated with prostate cancer risk

Abstract Mosaic loss of the Y chromosome (mLOY), a type of clonal hematopoiesis, is the most frequent chromosomal alteration observed in leukocytes of aging men. mLOY is a putative biomarker of genomic instability with evidence of associations with risk of some solid tumors, but more studies are needed to refine associations and identify potential mechanisms for cancer risk. Prostate cancer (PCa), the most common non-cutaneous cancer in males, is also associated with aging. To further investigate potential relationships between mLOY and PCa, we examined DNA derived from leukocytes of male participants in two large biobanks: the UK Biobank (UKBB; N = 210,103) and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO, N = 26,795). Of the 236,898 male participants without previous cancer diagnosis, 14,253 (6.0%) were diagnosed with incident PCa after DNA collection. High-density genotyping array data collected during the studies were used to create virtual karyotypes for detecting mLOY in whole blood samples utilizing a phase-based detection method in MoChA software. Analyses were restricted to men without cancer at genotyping and multivariable regression models were adjusted for age, smoking status, and genetic similarity. Men with detectable mLOY were older (mean = 62 vs 56 years) and more likely to be smokers (14.8% vs 9.7%) than men without mLOY. A total of 3,848 (27.0%) men with PCa and 42,835 (19.2%) men free of PCa had detectable mLOY. mLOY clonal fraction ranged from 0.01% to 72.1% of total leukocytes. 18.7% of PCa cases and 13.6% of men free of PCa had high clonal fraction mLOY, defined as greater than 10% of leukocytes with mLOY. Fixed effect meta-analysis of multivariable models from UKBB and PLCO produced evidence for a positive association between mLOY in leukocytes and incident PCa; (Odds Ratio (OR) = 1.062, 95% Confidence Interval (CI) [1.020, 1.107], P-Value (p) = 0.004). The effect estimate was the same in men with low clonal fraction of mLOY (OR = 1.062, 95% CI [1.012, 1.113], p = 0.014) and men with high clonal fraction of mLOY (OR = 1.065, 95% CI [0.998, 1.137], p = 0.057). Age at PCa diagnosis was not associated with mLOY or the clonal fraction of mLOY. A sub-analysis of separate participants from PLCO with mLOY detected in buccal cells (n = 18,011) also showed a small positive effect between mLOY and PCa risk, but the relationship did not reach statistical significance (OR = 1.036, 95% CI [0.877, 1.224], p = 0.673)). Our investigation of the relationship between mLOY and PCa in two large prospective studies provides additional evidence for an association between mLOY detected in the blood and increased PCa risk, meriting additional studies of potential biologic mechanisms underlying the relationship. Citation Format: Rebecca L. Kelly, Weiyin Zhou, Kara M. Barnao, Corey D. Young, Aubrey K. Hubbard, Sairah M. Khan, Wen-Yi Huang, Stephen J. Chanock, Mitchell J. Machiela. Mosaic loss of the Y chromosome is associated with prostate cancer risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3430.

Abstract 7330: Identifying proteomic risk factors for overall, aggressive and early onset prostate cancer using mendelian randomization and tumor spatial transcriptomics

Abstract Background: Understanding the role of circulating proteins in prostate cancer risk can reveal key biological pathways and identify novel targets for cancer prevention. Methods: We investigated the association of 2,002 genetically predicted circulating protein levels with risk of prostate cancer overall, and of aggressive and early onset disease, using cis-pQTL Mendelian randomization (MR) and colocalization. Findings for proteins with support from both MR, after correction for multiple-testing, and colocalization were replicated using two independent cancer GWAS, one of European and one of African ancestry. Proteins with evidence of prostate-specific tissue expression were additionally investigated using spatial transcriptomic data in prostate tumor tissue to assess their role in tumor aggressiveness. Finally, we mapped risk proteins to drug and ongoing clinical trials targets. Results: We identified 20 proteins genetically linked to prostate cancer risk (14 for overall [8 specific], 7 for aggressive [3 specific], and 8 for early onset disease [2 specific]), of which a majority were novel and replicated. Among these were proteins associated with aggressive disease, such as PPA2 [Odds Ratio (OR) per 1 SD increment = 2.13, 95% CI: 1.54-2.93], PYY [OR = 1.87, 95% CI: 1.43-2.44] and PRSS3 [OR = 0.80, 95% CI: 0.73-0.89], and those associated with early onset disease, including EHPB1 [OR = 2.89, 95% CI: 1.99-4.21], POGLUT3 [OR = 0.76, 95% CI: 0.67-0.86] and TPM3 [OR = 0.47, 95% CI: 0.34-0.64]. We confirm an inverse association of MSMB with prostate cancer overall [OR = 0.81, 95% CI: 0.80-0.82], and also find an inverse association with both aggressive [OR = 0.84, 95% CI: 0.82-0.86] and early onset disease [OR = 0.71, 95% CI: 0.68-0.74]. Using spatial transcriptomics data, we identified MSMB as the genome-wide top-most predictive gene to distinguish benign regions from high grade cancer regions that had five-fold lower MSMB expression. Additionally, ten proteins that were associated with prostate cancer risk mapped to existing therapeutic interventions. Conclusion: Our findings emphasize the importance of proteomics for improving our understanding of prostate cancer etiology and of opportunities for novel therapeutic interventions. Additionally, we demonstrate the added benefit of in-depth functional analyses to triangulate the role of risk proteins in the clinical aggressiveness of prostate tumors. Using these integrated methods, we identify a subset of risk proteins associated with aggressive and early onset disease as priorities for investigation for the future prevention and treatment of prostate cancer. Citation Format: Trishna A. Desai, Asa K. Hedman, Marios Dimitriou, Mine Koprulu, Sandy Figiel, Wencheng Yin, Matthias Johansson, Eleanor L. Watts, Joshua R. Atkins, Aleksandr V. Sokolov, Helgi B. Schioth, Marc J. Gunter, Konstantinos K. Tsilidis, Richard M. Martin, Maik Pietzner, Claudia Langenberg, Ian G. Mills, Alastair D. Lamb, Anders Malarstig, Tim J. Key, The PRACTICAL Consortium, Ruth C. Travis, Karl Smith-Byrne. Identifying proteomic risk factors for overall, aggressive and early onset prostate cancer using mendelian randomization and tumor spatial transcriptomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7330.

Abstract 4443: Trans-population two-sample Mendelian randomization study of circulating metabolites and prostate cancer risk

Abstract While prostate cancer (PCa) is highly heritable, mechanisms underlying disease risk and PCa disparities are not well understood. Here, we conducted a two-sample Mendelian randomization (MR) to assess whether serum metabolites are causally associated with PCa risk in European, African, and Hispanic populations. MR analyses were performed on metabolite quantitative trait loci (mQTLs) for 250 metabolites quantified by untargeted mass spectroscopy via the Metabolon platform for 1,498 European and 1,740 African ancestry individuals from the Atherosclerosis Risk in Communities (ARIC) cohort and for 711 metabolites measured in 3,166 Hispanic individuals from the Hispanic Community Health Study/Study of Latinos (SOL). PCa GWAS summary statistics were obtained for men from European (122,188 cases, 604,640 controls), African (19,391 cases, 61,608 controls) and Hispanic (3,931 cases, 26,405 controls) populations from the PRACTICAL Consortium. Within each population, QTLs associated with metabolites at the genome-wide significance level (P<5x10-8) were included in instruments upon removing rare (minor allele frequency≤0.01) or correlated (R2≥0.2) SNPs calculated in ancestry-matched TOPMed populations. Inverse variance weighted (IVW) random effect models are presented as primary results. Sensitivity analyses were utilized to assess assumption violations (weighted mode, weighted median and MR egger). MR were conducted separately in each population, and fixed effect meta-analyses were conducted across population-specific MR results to identify trans-population associations. A false discovery rate was implemented to account for multiple testing. In total, 22, 4 and 1 metabolites significantly associated with PCa risk in Hispanic, European and African populations, respectively. Of these, 13 metabolites had a MR instrument in ≥1 population, 12 of which were significant following a trans-population meta-analysis, including 5 fatty acids, 3 lysophospholipids, 1 amino acid, 1 carbohydrate, 1 nucleotide and 1 xenobiotic. All fatty acids were associated with decreased PCa odds (2%-10%), as were 4 other metabolites (amino acid 3-methyoxytyrosine, nucleotide 5-methyluridine and lysophospholipids 1-archidonoyl-GPC (20:4n6) and 1-archidonoyl-GPE (20:4n6), 4%-9%). The 3 remaining metabolites, erythritol, 1-linoleoyl-GPE (18:2) and mannose, were found to increase PCa odds by 10%, 6% and 4%, respectively. Additional metabolite harmonization efforts are underway to conduct trans-population analyses metabolome-wide. This study provides evidence of associations between metabolites, such as fatty acids and lysophysopholipids, and PCa across diverse populations. These findings point to mechanisms that could inform preventive or therapeutic strategies pending functional investigations. Multivariable and bidirectional MR are ongoing to further assess findings. Citation Format: Harriett Fuller, Rebecca Rohde, Heather Highland, Jiayi Shen, Bing Yu, Eric Boerwinkle, Megan Grove, Kari E. North, David V. Conti, Christopher A. Haiman, Kristin Young, Burcu Darst. Trans-population two-sample Mendelian randomization study of circulating metabolites and prostate cancer risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4443.

Abstract 850: Androgenic alopecia and risks of overall and aggressive prostate cancer: An updated meta-analysis

Abstract Background: Androgenic alopecia, known as male pattern baldness (MPB), is a common hair loss disorder among men. MPB has similar risk factors with prostate cancer (PrCa) including advancing age, family history, and sex hormones. Several studies have examined the associations between MPB and PrCa but the evidence remains unclear. We carried out a meta-analysis of epidemiological studies that examined the relationship between patterns of baldness: frontal, vertex, or both and PrCa risk. Methods: A literature search was performed in October 2022 using PubMed and Web of Science databases for epidemiological studies published between 1/1/2000 and 10/31/2022, which examined the above hypothesis. From each eligible study, relevant data were extracted on study design, population, sample size, prevalence of MPB at various ages, and corresponding associations with risks of total and aggressive PrCa. Pooled relative risks (RR) and corresponding 95% confidence intervals (CI) were calculated using the DerSimonian and Laird random-effects models. Heterogeneity across studies was assessed by I2 statistic. Results: A total of 14 studies: 14,573 cases and 132,434 controls/non-cases were included. The prevalence of MPB increased from 5% to 70% with aging and varied across studies. Vertex MPB at ages 40 years or older was associated with a pooled RR of 1.08 (95%CI 1.00-1.17) of total PrCa, but there was no association with frontal MPB. The onset of MBP at younger ages was also associated with RR=1.10 (95% CI 0.93 - 1.29) of PrCa, although results were not statistically significant. Results were similar when data were stratified by clinical features of PrCa, although there was large heterogeneity in the definition of aggressive PrCa across studies. Conclusions: Men with vertex MPB may have modest increased risk of PrCa. However, the majority of studies were conducted in Caucasian men and they did not evaluate effect modifications by genetic variations in androgen metabolism pathway genes or changes in serum levels of androgens. Further, large well-designed prospective cohort studies are needed to better understand the complex relationship between genetic susceptibility, endogenous hormones, MBP and risk of PrCa. Citation Format: Sapir Amar, David Hanelin, Ilir Agalliu. Androgenic alopecia and risks of overall and aggressive prostate cancer: An updated meta-analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 850.

Abstract 3452: Senescence-associated secretory phenotype (SASP) aging index is associated with cancer risk in the Atherosclerosis Risk in Communities (ARIC) Study

Abstract Background: The accumulation of senescent cells, which release SASP proteins damaging neighboring cells, contributes to aging and age-related diseases, such as cancer. Therefore, SASP proteins could be used as biomarkers for individuals’ aging process, but no studies have tested if SASP protein-based aging index is associated with cancer risk. We created a SASP-aging index based on the 72 SASP proteins reported in Tanaka et al. [2018] and examined its association with cancer risk in the ARIC study. Methods: ARIC is an ongoing cohort of White and Black females and males initiated in 1987, followed for cancer until 2015 (median follow-up=17.3 yrs). At Visit 2 (1990-92), 5000 plasma proteins were measured using SomaScan – an aptamer-based assay in 10,834 participants (aged 46-70 yrs, 55% female, 76% White): 3,347 participants developed cancer during follow-up and 7,487 participants stayed cancer-free. In the training set of 67% randomly selected cancer-free participants, we constructed the SASP-aging index by applying Ridge regression to train the 72 SASP proteins against chronological age. The SASP-aging index was validated in the remaining 33% of cancer-free participants (test set). We calculated age acceleration as residuals after regressing the SASP-aging index on age in participants after excluding the training set. We used Cox proportional hazards regression to estimate hazard ratio (HR) and 95% confidence intervals (CI) for the risk of any type of cancer per 5 years increase in age acceleration, employing Barlow’s method [1994] to account for the exclusion of the training set. HR was adjusted for age, sex, race, center, education, BMI, smoking status, alcohol intake, aspirin use, diabetes, and eGFR. We also estimated HRs for obesity-related, smoking-related, and the most common cancers (breast, prostate, colorectal, and lung). Results: In the test set, Pearson correlation coefficient between the SASP-aging index and age was 0.50. Age acceleration was significantly associated with the risk of any type of cancer [HR (95% CI) per 5 years=1.21 (1.08-1.36)]. There was a suggestion of a higher HR for any type of cancer in females [1.26 (1.07-1.48)] than males [1.18 (1.00-1.39)] [p-interaction=0.08], but HRs were similar across race and smoking status [p-interaction>0.50]. Age acceleration was significantly associated with the risk of obesity-related cancers [1.36 (1.20-1.54)]. A significant association was also found with smoking-related cancers [1.43 (1.24-1.65)] and this association remained significant even among never smokers [1.39 (1.07- 1.82)]. Age acceleration was also significantly associated with colorectal [1.34 (1.03-1.75)] and lung cancer risk [1.63 (1.31-2.02)] but not with breast or prostate cancer risk. Conclusion: SASP protein-based aging index shows promise as a potential biomarker for cancer risk. Funding: NHLBI, NCI, NPCR Citation Format: Shuo Wang, Zexi Rao, Anne H. Blaes, Josef Coresh, Corinne E. Joshu, James S. Pankow, Bharat Thyagarajan, Peter Ganz, Elizabeth A. Platz, Weihua Guan, Anna Prizment. Senescence-associated secretory phenotype (SASP) aging index is associated with cancer risk in the Atherosclerosis Risk in Communities (ARIC) Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3452.

Abstract 3440: Etiology of prostate cancer with the TMPRSS2:ERG fusion: A systematic review of risk factors

Abstract Background: The TMPRSS2:ERG gene fusion is the most common somatic alteration in primary prostate cancer and an early event in carcinogenesis. There are emerging data highlighting etiologic differences in prostate cancer by TMPRSS2:ERG status. This systematic review synthesized evidence from epidemiologic studies on prostate cancer risk factors for tumors with and without the TMPRSS2:ERG fusion. Methods: A systematic literature search was performed in Ovid MEDLINE, EMBASE, and Web of Science without language restriction for studies published by September 27, 2022. Studies that assessed associations between epidemiologic and genetic factors and prostate cancer risk by tumor TMPRSS2:ERG (ERG) fusion status in human populations were included. Results: Of 3,071 records identified, 20 publications comprising prospective cohort and case-control studies from five study populations (published 2009-2022) were included. Risk factors included germline genetic variants, circulating hormones, diet, lifestyle factors, and medications. The included studies suggested that taller height and higher total and free circulating testosterone levels tended to be associated with higher risk of ERG-positive, but not ERG-negative prostate cancer. CAG repeat length in the androgen receptor (AR) gene, related inversely to transcriptional activity, appeared to be associated with a lower risk of ERG-positive, but not ERG-negative prostate cancer. There was statistical evidence for etiologic differences for several germline single nucleotide polymorphisms (SNPs) by ERG status. Excess body weight, greater vigorous physical activity, greater lycopene intake, and calcium channel blocker use appeared to specifically be associated with a lower risk of ERG-positive tumors. Associations of other potential etiologic factors, including diabetes mellitus, baldness, aspirin use, circulating antioxidant levels, and sex hormones other than testosterone, with ERG-positive prostate cancer were null or inconclusive. Most associations had low precision, and the results were based on few distinct study populations, highlighting a need for replication. Conclusions: Prostate cancer with the TMPRSS2:ERG fusion may be an etiologically distinct subtype impacted by certain modifiable and hormonally-acting risk factors that align with the established mechanistic role of this gene fusion in androgen, insulin, and growth factor pathways. The findings suggest a potentially distinct genetic predisposition to prostate cancer with or without the TMPRSS2:ERG fusion. More broadly, these findings suggest that considering molecular subtypes of prostate cancer, beyond TMPRSS2:ERG, may strengthen etiologic understanding of prostate cancer and evidence for prevention. Citation Format: Colleen B. McGrath, Alaina H. Shreves, Megan R. Shanahan, Hannah E. Guard, Manelisi V. Nhliziyo, Kathryn L. Penney, Tamara L. Lotan, Michelangelo Fiorentino, Konrad H. Stopsack, Lorelei A. Mucci. Etiology of prostate cancer with the TMPRSS2:ERG fusion: A systematic review of risk factors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3440.

Abstract 5603: Defining the functions of the BRCA2 BRC repeats in modulating RAD51 binding and activity

Abstract The BRCA2 (Breast Cancer Susceptibility 2) gene is critical for preserving genome integrity by regulating homology-directed repair (HDR) of DNA double-strand breaks (DSBs). Germline mutations in BRCA2 predispose individuals to a high risk for ovarian, breast, prostate, and pancreatic cancer. BRCA2 contains eight BRC repeats that mediate binding to RAD51. It remains unclear how exactly the different BRC repeats regulate RAD51 functions. In our study, we explore the importance of each BRC repeat, their interconnections, and their impact on RAD51 binding and filament stability. We engineered amino acid substitutions into the BRC FxTAS motif required for specific contacts within a hydrophobic binding pocket of RAD51 to disrupt BRC binding to RAD51. We further created mutations in RAD51 (F86E/A89E) that either prevent self-association but retain binding to the BRC repeats or a mutation (K133R) that results in a hyper-stable RAD51 nucleoprotein filament. Using both cell-based models and biochemical analyses, we have begun studies to parse out the specific functions of each BRC repeat. Our ultimate goal is to incorporate single amino acid changes into each BRC repeat within the context of the full-length BRCA2 protein to comprehensively characterize the contribution of each BRC repeat to HDR and response to chemotherapeutics such as PARP inhibitors. Citation Format: Julia R. Jensen, Ryan B. Jensen. Defining the functions of the BRCA2 BRC repeats in modulating RAD51 binding and activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5603.

Abstract 6117: Characterizing cancer patterns in Okinawan vs. mainland Japanese Americans: The Multiethnic Cohort

Abstract Differences in chronic disease rates have been documented in Japan between Okinawa and mainland Japan. Limited data exist on whether these differences are also present in Okinawans and mainland Japanese who have migrated to the US. We used genotyped genome-wide association study data from the Multiethnic Cohort Study (MEC) to identify Japanese Americans of Okinawan or mainland ancestral similarity, and to investigate these two groups for differences in baseline chronic disease risk factors and for incidence of the four most common cancers during follow-up after blood draw. Cancer cases were identified via linkage to state cancer registries. Principal component analysis followed by uniform manifold approximation and projection (UMAP) was run using 15,678 single nucleotide polymorphisms among the 24,484 MEC Japanese Americans with blood samples. The Okinawan cluster was confirmed by labeling male MEC participants with Okinawan surnames on UMAP plots. Hazard ratios (HR), 95% confidence intervals (CI), and two-sided p-values were reported for Cox proportional hazards models, comparing cancer incidence between Okinawan and mainland Japanese individuals. The Okinawan cluster included 3,649 individuals (15% of the MEC Japanese Americans) and the mainland Japanese cluster included 19,611 individuals (80% of the MEC Japanese Americans). Small clusters of part-Okinawan and/or part-mainland Japanese (5% of the MEC Japanese Americans) were not included in the analysis. Ninety-six percent of Okinawan Americans and 94% of mainland Japanese Americans in MEC were born in the US. Okinawans were more likely to have a higher body mass index and daily alcohol intake, and less likely to be a current or former smoker, compared to mainland Japanese (all p-values<0.05). Post-menopausal Okinawan women were significantly more likely to be diagnosed with breast cancer (age-adjusted HR=1.39, 95% CI=1.10-1.75) compared to post-menopausal mainland Japanese women. This association was not modified by adjusting for additional known breast cancer risk factors (HR=1.36, 95% CI=1.07-1.73). Okinawans were also less likely to be diagnosed with lung cancer (HR=0.75, 95% CI=0.58-0.98); however, this association was no longer significant when adjusting for known risk factors, including smoking history (HR=0.82, 95% CI=0.62-1.07). There were no significant differences in risk of colorectal or prostate cancer between Okinawan and mainland Japanese individuals. Our results in this US-based sample are consistent with recent trends of higher breast cancer and lower lung cancer age-adjusted incidence rates reported from Japan for the Okinawan prefecture compared to mainland prefectures. Investigating reasons for the observed breast cancer risk difference may identify new risk factors for this disease in the Okinawan and other populations. Citation Format: Samantha A. Streicher, Song-Yi Park, Charleston W. Chiang, Xin Sheng, David Bogumil, David V. Conti, Christopher A. Haiman, Lynne R. Wilkens, Loic Le Marchand. Characterizing cancer patterns in Okinawan vs. mainland Japanese Americans: The Multiethnic Cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6117.

Abstract 7056: The role of aggressive prostate cancer risk gene ANO7 in prostate metabolism

Abstract Prostate cancer (PCa), the most common male cancer worldwide, causes about 10% of cancer related deaths in Europe. It has a wide spectrum of clinical behavior that ranges from decades of indolence to rapid metastatic progression and lethality. However, the molecular mechanisms involved in aggressive PCa progression are still poorly understood. In PCa the expression of anoctamin 7 (ANO7) has been shown to diminish as the cancer progresses. We have previously linked single-nucleotide polymorphisms in the ANO7 gene to the risk of aggressive prostate cancer and shown that in homozygous carriers of rs77559646, the variant leads to a total loss of ANO7 protein. ANO7 is a prostate-specific gene and is highly expressed in the luminal cells of the human prostate. ANO7 belongs to a family of calcium-activated chloride channels and select members of the anoctamin family have phospholipid scramblase activity. To uncover the cellular functions of ANO7 has proven challenging because ANO7 is not expressed in commercially available cell lines. To study the cellular functions of ANO7, we have generated stable prostate cell lines overexpressing ANO7 using lentiviral transduction. To gain information into what pathways ANO7 is affecting, we performed RNA-sequencing and gene set enrichment analysis. Interestingly, we found enrichment and downregulation of mitochondrial genes participating in oxidative phosphorylation in ANO7 cells. We assessed the mitochondrial function by measuring the oxidative phosphorylation capability of the cells and showed that the basal and maximal respiratory capacity of ANO7 overexpressing cells is indeed reduced. We also analyzed which of the three major mitochondrial fuels (glucose, glutamine and fatty acids) are not used as efficiently for oxidative phosphorylation in ANO7 overexpressing cells. The result proves that ANO7 cells are not utilizing glucose as effectively as control cells. Furthermore, the glycolysis stress assay showed that glycolytic capacity is increased in ANO7 overexpressing cells. In addition, a targeted metabolite screening revealed that aspartate is decreased in ANO7 cells, which again points towards perturbed mitochondrial function as aspartate is produced from a tricarboxylic acid cycle intermediate. By inhibiting the uptake of extracellular aspartate, we measured slower proliferation of ANO7 expressing cells, while inhibiting aspartate had no effect on control cells. Interestingly, preliminary results also suggest ANO7's involvement in regulation of phospholipid acyl chain length and saturation, offering insights into altered signaling observed in ANO7 cells. Taken together, this study shows for the first time that ANO7 rewires prostate mitochondrial functions and thus cellular metabolism, which could explain why it is beneficial for cancer cells to lose ANO7 expression. Citation Format: Christoffer Löf, Nasrin Sultana, Neha Goel, Gudrun Wahlström, Johanna Schleutker. The role of aggressive prostate cancer risk gene ANO7 in prostate metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7056.

Abstract 6280: Vitamin D enhances luminal differentiation of prostate organoids more than androgens

Abstract Background: Prostate Cancer (PCa) is a prevalent disease affecting over two million men worldwide. Vitamin D is a fat-soluble hormone that is well-known for its role in the maintenance of strong bones and has anti-cancer effects in prostate cancer. Vitamin D is synthesized in the skin in response to sun exposure and may be supplemented with diet. However, since melanin hinders this synthesis many African Americans are deficient in vitamin D. Vitamin D circulates as 25-hydroxyvitamin D3 (25D) and 25-dihydroxyvitamin D3 (1,25D). Hydroxylation of 25D by the kidney or within tissues forms the active hormone 1,25D. 1,25D binds the vitamin D receptor (VDR), a steroid transcription factor. Androgens are the main regulatory hormones involved in prostate growth and differentiation. Epithelial differentiation is the process in which progenitor or stem cells become specialized cells, such as basal or luminal. In the prostate, luminal epithelial cells are the most differentiated and are the origin of PCa. We used mouse prostate organoids to replicate the differentiation process in vitro and to help identify the role of 1,25D on epithelial differentiation in the presence and absence of other androgens. Methods: Primary mouse prostate cells were isolated from dorsal lateral lobes and grown as organoids. Over two weeks, we treated these organoids with concentrations of 1,25D and androgen (dihydrotestosterone, DHT). The four treatment groups were control, 1,25D only, DHT only and 1,25D+DHT. Organoids were imaged and analyzed for number, size and phenotype. Phenotypes were identified as luminal, acinar, or solid. Results: Luminal phenotypes were more prevalent in 1,25D conditions compared to control or DHT alone. The number, size and percent of luminal organoids was highest in 1,25D + DHT compared to all other groups. Ongoing studies include examination of prostate organoids from mice with a vitamin D-deficient diet and staining of the organoids for differentiation markers. Conclusions/Significance: We observed that 1,25D enhanced luminal epithelial differentiation in mouse prostate organoids. These findings suggest that chronic vitamin D deficiency may increase risk of aggressive prostate cancer, due to decreased epithelial differentiation. This has implications for the disparity of aggressive PCa observed in African American men who have lower vitamin D levels compared to their white counterparts. Citation Format: Oscar Fernando Cerna, Larisa Nonn, Mike Schlicht, Kirty Krieger. Vitamin D enhances luminal differentiation of prostate organoids more than androgens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6280.

Abstract 3811: Impact of antiviral treatment status on risk of extrahepatic cancers in patients with chronic hepatitis C

Abstract Background: Eradiation of hepatitis C virus (HCV) infection has been shown to reduce risk of liver cancer among HCV patients; however, there has been spare data on the effect of antiviral treatment on the risk of extrahepatic cancers. Using data from the Chronic Hepatitis Cohort Study (CHeCS), we investigated whether antiviral therapy impacts the risk of extrahepatic cancers among patients with HCV. Methods: 17,485 HCV patients were included in the study, and they were followed until incidence of cancer including lung cancer, non-Hodgkin lymphoma (NHL), breast cancer or prostate cancer, death, or last follow-up. An extended landmark modeling approach was considered, which included time-varying covariates and propensity score justification for treatment selection bias and used generalized estimating equations (GEE) with a link function as multinominal distribution for a discrete time-to-event data. Death was considered a competing risk. Results: Compared to untreated patients, patients with HCV treatment had significantly lower risk of lung cancer for direct-acting antiviral (DAA) treatment (hazard ratio (HR) = 0.47, 95% CI, 0.30-0.72) and for interferon-based treatment (IFN) (HR = 0.33, 95% CI, 0.20-0.50). The risk of NHL was only reduced among patients receiving DAA treatment. There were no significant associations between HCV treatment and risks of breast and prostate cancer. Conclusion: Both DAA and IFN antiviral treatment independently reduce the risk of lung cancer, while the protective association with NHL was limited among HCV patients with DAA treatment. Our findings support the importance of timely initiation antiviral therapy in chronic HCV-infected patients. Citation Format: Menghua Tao, Jia Li, Trueman Wu, Stuart C. Gordon, Loralee B. Rupp, Sheri Trudeau, Scott D. Holmberg, Anne C. Moorman, Philip R. Spradling, Eyasu H. Teshale, Mark A. Schmidt, Yihe G. Daida, Mei Lu. Impact of antiviral treatment status on risk of extrahepatic cancers in patients with chronic hepatitis C [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3811.

Abstract 6144: A polymorphic TERT tandem repeat creating an expandable intronic G4 quadruplex is associated with TERT expression, relative leukocyte telomere length and cancer risk

Abstract A multi-cancer GWAS region at human chromosome 5p15 encodes telomerase reverse transcriptase (TERT). One of the GWAS signals is rs10069690-T, which creates an alternative intron 4 splicing site, co-producing full-length (FL) and truncated INS1b transcript for dominant-negative telomerase-nonfunctional TERT. A variable number tandem repeat (VNTR6-1, 38 bp repeat unit) within intron 6 remains uncharacterized in relation to GWAS signals and cancer risk. We hypothesized that VNTR6-1 might contribute to GWAS signals represented by rs10069690. We scored VNTR6-1 and rs10069690 in short-read WGS data (n=3,202) from the 1000 Genomes Project with a machine learning model using the GLMnet engine, and in phased long-read assemblies (n=544). We defined two VNTR6-1 groups: Short (24-27 copies) and Long (40.5-66.5 copies); the VNTR6-1-Long group was preferentially linked with rs10069690-T compared to C allele (p=2.53E-13). We show that haplotypes of rs56345976 and rs33961405 alleles can predict VNTR6-1 groups. We imputed VNTR6-1 in UK Biobank controls (n=351,634), PLCO cancer cases and controls (n=100,445), and African Burkitt lymphoma cases (aBL, n=79). Functional studies in aBL tumors revealed a suggestive association between reduced total TERT expression, rs10096690-T (p=0.035) and VNTR6-1-Long (p=0.053). VNTR6-1 forms a G4 quadruplex structure sensitive to G4 stabilizing ligands, altering the ratio between FL-TERT and a dominant-negative TERT-β isoform in isogenic cell lines with/without VNTR6-1. In GTEx and TCGA, several metrics related to cell proliferation and telomerase activity correlated positively with FL-TERT expression and negatively with TERT-β expression. We created a composite marker with 0, 1 or 2 copies of the FL-TERT-associated haplotype (VNTR6-1-Short/rs10069690-C) to capture the effects of these variants that negatively affect TERT expression and telomerase activity. The number of copies of the VNTR6-1/rs10069690 haplotype was associated with relative leukocyte telomere length in UK Biobank controlling for sex and age (β=0.049, p=8.75E-78). This marker was also associated with a reduced risk of bladder and prostate cancer but an increased risk of breast, endometrial, ovarian, thyroid cancer, and glioma in PLCO. Our findings reveal that germline variants VNTR6-1-Long/rs10069690-T underlie the multi-cancer GWAS signal and jointly decrease TERT expression and telomerase activity, potentially reducing the risk of some cancers by limiting cell growth. However, decreased telomerase activity could deregulate stem cell-driven tissue regeneration and genome integrity, increasing the risk of other cancers. Our findings unveil novel mechanisms of cancer susceptibility and propose therapeutic avenues for targeting TERT isoform ratios to modulate telomerase activity and its cellular effects. Citation Format: Oscar Florez-Vargas, Michelle Ho, Max Hogshead, Chia-Han Lee, Kaitlin Forsythe, Brenen Papenberg, Kristine Jones, Wen Luo, Kedest Teshome, Cornelis Blauwendraat, Mikhail Kolmogorov, Stephen J. Chanock, Mitchell J. Machiela, John Schneekloth, Shahinaz Gadalla, Sharon A. Savage, Sam M. Mbulaiteye, Ludmila Prokunina-Olsson. A polymorphic TERT tandem repeat creating an expandable intronic G4 quadruplex is associated with TERT expression, relative leukocyte telomere length and cancer risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6144.

Abstract 7320: Expression of circadian rhythm genes and lethal prostate cancer

Abstract Background: The circadian rhythm regulates diverse physiological and oncologic processes. We have previously shown in epidemiology studies that disruption of the circadian rhythm may be associated with increased risk of aggressive prostate cancer, including germline polymorphisms in certain circadian rhythm genes. This study sought to investigate the relationship between tumor circadian rhythm gene expression and lethal prostate cancer. Methods: We studied patients with primary prostate cancer in the Health Professionals Follow-up Study (HPFS) and Physicians’ Health Study (PHS). We created a composite score of mRNA expression using principal components that incorporated 11 circadian rhythm genes: AANAT, ARNTL, CLOCK, CRY1, CSNK1E, MTNR1A, MTNR1B, NPAS2, PER1, PER2, PER3. An age-stratified analysis was performed, and the mean differences of the score both by Gleason score and compared to normal tissue were calculated. The relationship between the score in prostate tumor tissue and lethal prostate cancer (metastases/prostate cancer-specific death) vs. indolent disease (no metastases after >8 years of follow-up) was assessed using logistic regression. The contribution of each gene was evaluated by leave-one-out analysis, generating scores leaving out one gene and assessing the relationship between the modified score and lethal disease. Results: Among 404 cancer patients in HPFS/PHS, there were 119 lethal events over 30 years of follow-up (median: 17 years). The circadian rhythm gene score was lower in tumor tissue compared to tumor-adjacent, histologically normal tissue (mean difference in units of standard deviation [SD] of gene score: -0.31, 95% confidence interval [CI]: -0.48 to -0.15). In addition, the score was lower in Gleason 9-10 compared to Gleason 6 tumors (mean difference in SD units: -1.05, 95% CI: -1.55 to -0.54). The three PER genes were the most strongly correlated with each other and with the score (Spearman correlation coefficients from 0.52-0.88 for the score and 0.31-0.63 between PER genes). Higher circadian rhythm gene scores were inversely associated with lethal prostate cancer (odds ratio [OR] for highest vs. lowest quartile: 0.43, 95% CI: 0.20 to 0.90) in a dose-response fashion and after adjusting for clinical and pathologic factors. The association appeared to be stronger in patients aged ≥65 years (OR for highest vs. lowest quartile: 0.21, 95% CI: 0.08 to 0.47) compared to <65 years at diagnosis (OR: 0.78, 95% CI: 0.29, 2.17). Results were consistent in the leave-one-out analysis for all genes except PER2 (OR for highest vs. lowest quartile: 1.00, 95% CI: 0.55 to 1.83) and PER1 (OR: 0.55, 95% CI: 0.30 to 1). Conclusion: This study examining intratumoral circadian rhythm gene expression contributes further evidence in support of the relationship between circadian rhythm disruption and aggressive prostate cancer. Tumor expression of PER1 and PER2 may be a predominant factor in the association. Citation Format: Jane Bailey Vaselkiv, Sarah C. Markt, Hannah E. Guard, Anqi Wang, Kathryn L. Penney, Konrad H. Stopsack, Lorelei A. Mucci. Expression of circadian rhythm genes and lethal prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7320.

Abstract 3751: Diagnostic assessment of Filamin A (FLNA) as a serum biomarker for identification of benign prostatic hyperplasia vs aggressive prostate cancer in a prospective Mexican cohort

Abstract Prostate cancer (PCa) exhibits a significant health risk to aging men, in which effective diagnosis of high gleason (Gleason >7) cancers is of critical need. Currently, the main screening tool utilized for detection of prostate cancer is prostate specific antigen (PSA), however, PSA exhibits limited utility in men with benign prostatic hyperplasia (BPH) due to inherent elevated PSA as the result of an enlarged prostate, resulting in increasing unnecessary biopsies. In Mexico, there is currently a higher incidence of aggressive PCa due to the risk within the overall population as well as the need for increased screening tools. Since, there is a critical unmet need to evaluate novel PCa diagnostic test that could serve as a reflex test within the screening paradigm, we evaluated the recently developed test, pSTATEdx, which measures the cleaved portion of Filamin A (FLNA) via IP-MRM mass spectrometry in conjunction with the patients age, to determine the overall risk of aggressive prostate cancer. In the current study, we analyzed a prospective cohort from Mexico City and Guadalajara evaluating 34 BPH and 44 PCa in men exhibiting symptoms with PSA levels between 4-10 ng/mL, who were all referred for 12 core prostate biopsies due to suspicion of prostate cancer. Additionally, we assessed 41 non-diseased men as controls who had PSA below 1.5 ng/mL, who were not assessed further. Comparison of non-diseased controls with BPH/PCa men exhibited an AUC of 0.99, PPV 0.96, NPV 0.89, OR 118, and P value 2 e-20, thus demonstrating that pSTATEdx had significant utility in assessing prostate health independent of PSA. In comparison with previously published data, FLNA mean levels were 24 ng/mL in previously published American study cohort and 55 ng/mL in the Mexican BPH/PCa cohort with a P value of <0.001. Assessment of patient populations revealed that there was superior diagnostic performance of FLNA for patients between PSA 4-7, which represents an increased unmet need for biopsy decision support. Analysis of BPH compared to all PCa exhibited a sensitivity of 0.94 and specificity of 0.53, PPV 0.64, NPV of 0.91, and OR of 16.4. Diagnostic analysis of BPH compared to high gleason PCa exhibited a sensitivity of 1, specificity of 0.21, PPV 0.38, NPV of 1, and OR of inf in this pilot study. This assessment revealed promising insight that aggressive PCa was not missed using pSTATEdx. pSTATEdx demonstrated diagnostic utility in prevention of unnecessary biopsies in the Mexican population as a reflex test to those patients with PSA levels between 4-7 as well as demonstrated that aggressive prostate cancers were not missed with the risk score. Additional studies are planned in the future to expand the utility of pSTATEdx in Latin America. Citation Format: Arturo Rodriguez, Arturo Mendoza, Matthew Rosenburg, José de J. Castaneda, Alejandro A. Melgar, Bernardo Ciseros, Adrian G. Gangemi, Nischal M. Chand, Poornima Tekumalla, Greg Miller, Anjan Thakurta, Diego Banuelos, Juan J. Real, Diego A. Joya, Alejandro Romero, Juan D. Farias, Eduardo Cabeza, Hector H. Remess, Julio J. Delgado, Hector M. Sanchez, Ignacio Barragan, Mabel Rodriguez, Barbara Garcia, David A. Sanchez, Juan Izquierdo, Elizabeth M. Lopez, Juan Hanao, Jeronimo G. Frusch, Niven R. Narain, Michael A. Kiebish. Diagnostic assessment of Filamin A (FLNA) as a serum biomarker for identification of benign prostatic hyperplasia vs aggressive prostate cancer in a prospective Mexican cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3751.

Abstract 253: Investigating key molecular players in putative stem cell subpopulations of prostate cancer

Abstract Background: Androgen deprivation therapy is the standard treatment for prostate cancer (PCa). Nevertheless, despite initial effectiveness, pre-existing cancer stem cell (CSC) populations invariably lead to incurable castration-resistant prostate cancer. CSCs are a subset of cancer cells possessing self-renewal properties, driving tumor progression and regrowth. CD44+ PCa cells exhibit more stemness features and are enriched in tumorigenic and metastatic progenitor cells. Here, we aim to explore different subpopulations in tumors based on levels of CD44 expression and investigate whether they have distinct molecular properties and functional characteristics. Material and Method: The number of CD44+ cells was evaluated in a tissue microarray from primary prostate cancer patient samples (EMPACT cohort) with clinical follow-up. Flow cytometry sorted the CRPC model LAPC9 tumor into CD44 high (CD44-H) and CD44 low (CD44-L) cells. RNA sequencing was performed on these subpopulations to explore their transcriptomic profiles. CD44 expression was validated at the cDNA and protein levels using qPCR and Western blot (WB) analysis. Sorted cells were maintained as organoids in vitro. To trace the dynamics of CD44-H and CD44-L subpopulations in vivo, LAPC9 tumor was labeled by fluorescent and luciferent markers. The CD44 status was determined by flow cytometry when tumor growth. Results: Patients with elevated expression of CD44 (higher number of CD44+ cells) at the time of surgery exhibited a greater propensity for clinic progression (5-year progression-free survival: 75% vs 95%, P=0.03). Furthermore, CD44-H cell ratio increased in the LAPC9 after castration, indicating that CD44-H cells can survive after treatment. Subsequent WB analysis confirmed that CD44 was highly expressed in sorted CD44-H cells, validating the flow cytometry results. Analysis of the CD44 RNA-seq data showed CD44 transcript variants CD44v10 (CD44-201) and CD44v7-10 (CD44-209) were notably upregulated in CD44-H cells. In organoid culture, sorted CD44-H cells displayed enhanced formation, indicating they possessed higher proliferative capacity and clonogenicity than CD44-L cells. Furthermore, when GFP-labeled CD44-H cells and RFP-labeled CD44-L cells were recombined in vivo, CD44-H cells exhibited robust proliferation, while CD44-L cells transitioned to a CD44hi state to facilitate tumor growth. Moreover, those GFP and RFP subpopulations displayed the same CD44hi cell ratio at the endpoint. Conclusion: Elevated CD44 expression is related to an increased risk in primary PCa. In addition, CD44-H cells exhibit high tumorigenicity in vitro and in vivo and can convert to each other. Moreover, the ratio of CD44-H cells in tumor at endpoint is consistent despite the starting CD44 expression status. Furthermore, the upregulation of CD44v10 and v7-10 in the CD44-H subpopulation may promote tumor formation and metastasis. Citation Format: Wanli Cheng, Marta De Menna, Francesco Bonollo, Panagiotis Chouvardas, George N. Thalmann, Sofia Karkampouna, Marianna Kruithof Julio. Investigating key molecular players in putative stem cell subpopulations of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 253.

Abstract 844: DNA methylation-derived immune cell profiles and risk of cancers in Black participants in the ARIC Study

Abstract Background: Prior cohort studies assessing cancer risk based on immune cell subtype profiles have predominantly focused on White populations. This limitation can obscure vital insights into how cancer risks vary across races, ethnicities, or exposures. This study was designed with the purpose of examining associations between pre-diagnostic immune cell profiles and cancer risk in Black participants. Methods: In this study, DNA methylation was measured in blood samples collected between 1993 and 1995 from a subset of 2,467 Black participants in the Atherosclerosis Risk in Communities (ARIC) prospective cohort study. Immune cell subtype proportions were estimated using deconvolution based on leukocyte DNA methylation markers. The analysis included 668 incident cancers ascertained between time of blood draw and 2015. Cox proportional hazards regression models were used to analyze the association between immune cell subtype proportions and cancer incidence (all cancers; lung, breast, and prostate cancers). Models controlled for age, sex, BMI, self-reported smoking status, self-reported and methylation-derived smoking pack-years, postmenopausal hormone use, and batch effect, along with other cancer-specific factors. Results: Increased T regulatory cell (Treg) proportions were associated with significantly higher risk of lung cancer (HR: 1.22, 95% CI = 1.06, 1.41 per percent increase; n = 84 cases) and suggestively higher risk of all cancers. Increased B memory cell proportions were associated with significantly higher risk of prostate cancer (HR: 1.17, 95% CI = 1.04, 1.33; n = 173 cases), all cancers (HR: 1.13, 95% CI = 1.05, 1.22), and suggestively higher risk of lung cancer. Increased CD8+ naïve cell proportions were associated with suggestively lower risk of lung cancer and all cancers, and significantly lower risk of all cancers in participants over the median age of 55 years (HR: 0.91, 95% CI = 0.83, 0.98). Cancer risks for other immune cell subtypes were null. Conclusions: These results in Black participants align closely with prior findings in largely White populations. Deconvolution allowed for the extension of work on cancer immunity (which has largely focused on major immune cell types) to immune cell subtypes like B memory cells and CD8+ naïve cells. The results are consistent with Tregs initiating and accelerating cancer development by impeding the usual protective immune response. A large reservoir of CD8+ naïve cells may allow for a more targeted and efficient elimination of malignant clones. Further studies should assess these relationships in other cancer types and better elucidate the interplay of B cells in theorized mechanistic processes. This study provides insight into the role of immune cell subtypes in cancer risk among Black men and women. Funding: NHLBI, NCR, NPCR Citation Format: Christopher S. Semancik, Naisi Zhao, Devin Koestler, Eric Boerwinkle, Jan Bressler, Karl Kelsey, Elizabeth A. Platz, Dominique S. Michaud. DNA methylation-derived immune cell profiles and risk of cancers in Black participants in the ARIC Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 844.

Abstract 1831: Reduction of PMN-MDSC level/activity following the consumption of white button mushroom in prostate cancer murine models and patients: A translational study to mitigate cancer progression

Abstract Frequent consumption of edible mushrooms, such as white button mushrooms (WBM), has been associated with a lower risk of prostate cancer [1]. Our laboratory at City of Hope has over 20 years of collective experience in defining the anticancer mechanisms of WBM [2, 3]. Previous studies have indicated that WBM consumption has anti-androgenic activities in prostate cancers in both preclinical models [4] and clinical trials [5]. In our first-in-human phase 1 trial on prostate cancer patients, we ensured the safety of consuming WBM in humans. In addition to observing a therapeutic-responsive decline in prostate-specific antigen (PSA), the levels of myeloid-derived suppressor cells (MDSCs) reduced in responders to WBM treatments [5]. These observations led us to hypothesize that WBM may mitigate the progression of prostate cancer in part by modulating the immune response. In the current study, we conducted translational research in syngeneic murine models and in prostate cancer patients from an ongoing phase 2 trial, aiming to define the immunomodulatory activity and mechanisms of WBM. We confirmed that WBM consumption in mouse models altered the number and function of immunosuppressive cells (MDSCs) and anti-tumor immune cells (T & NK cells), ultimately enhancing the intratumor and systemic immune responses. At a bulk-transcriptional level, we observed the elevated expression of programmed cell death protein 1 (PD-1) in xenograft tumors. In our single immune cell profiling of patients’ blood specimens following 3 months of WBM consumption in freeze-dried tablets form, we investigated the transcriptional landscape of circulating immune cells in response to WBM interventions. The level of circulating neutrophil-associated PMN-MDSCs decreased, and the remaining cells showed transcriptional profiles associated with "neutrophil chemotaxis", "leukocyte aggregation", and "regulation of inflammatory response", as functions associated with enhanced anti-tumor activity. Lastly, we also showed in a mouse model that WBM consumption synergistically enhances the anticancer activity of anti-PD1 drugs, indicating that WBM may be used as adjuvant therapy with immune checkpoint inhibitors. In summary, our results from prostate cancer patients and murine models show the immunomodulatory effects of WBM consumption and provide a scientific foundation for the application of WBM in alleviating prostate cancer progression. References 1, Zhang S., et al. Int. J. Cancer. 2019; 146:2712-2720. 2, Chen S., et al. Cancer Res. 2006; 66:12026-12034. 3, Adams L.S., et al. Nutr. Cancer. 2008; 60:744-756. 4, Wang X., et al. J. Nutr. Biochem. 2021; 89:108580.5, Twardowski P., et al. Cancer. 2015; 121:2942-2950. Citation Format: Xiaoqiang Wang, Shoubao Ma, Przemyslaw Twardowski, Clayton Lau, Yin Chan, Kelly Wong, Jinhui Wang, Xiwei Wu, Paul Frankel, Timothy G. Wilson, Timothy W. Synold, Cary Presant, Jianhua Yu, Shiuan Chen. Reduction of PMN-MDSC level/activity following the consumption of white button mushroom in prostate cancer murine models and patients: A translational study to mitigate cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1831.

Abstract 774: Genetic architecture, evolutionary genomics, and genomic risk of prostate cancer in sub-Saharan Africa

Abstract Men of African descent have the highest prostate cancer (CaP) incidence and mortality rates, yet the genetic basis of CaP in African men has been understudied. We performed the first large-scale genomic analysis of CaP across sub-Saharan Africa (SSA). We evaluated the evolutionary history of CaP-associated loci, generated a novel genomic risk score, inferred ancestry-specific genetic architectures, and fine-mapped disease associations using in 3,963 CaP cases and 3,509 controls recruited in Ghana, Nigeria, Senegal, South Africa, and Uganda through the Men of African Descent and Carcinoma of the Prostate (MADCaP) Network. Fifteen independent associations at 8q24.21, 6q22.1, and 11q13.3 reached genome-wide significance, including four novel associations. Multiple lead SNPs were private alleles in SSA, a pattern arising from recent mutations and the out-of-Africa bottleneck. These SSA-specific alleles contribute to haplotypes with odds ratios for CaP above 2.4. The genetic architecture of CaP differs across SSA, with effect size differences contributing more to this heterogeneity than allele frequency differences. Population genetic analyses reveal that SSA CaP associations are largely governed by neutral evolution, as opposed to natural selection. This finding is consistent with the late onset of this disease. Focusing on 2,502 age-matched cases and 2,222 non-cancer controls, we generated a novel genomic predictor of CaP. We then assessed the extent to which this polygenic risk score was correlated with age of onset, PSA levels, genetic ancestry, and family history of study participants. The performance of this novel polygenic risk score was tested on other populations of African descent, as well as populations with non-African ancestry. Our findings emphasize the utility of conducting genetic studies in diverse populations. Citation Format: Timothy R. Rebbeck, Rohini Janivara, Wenlong C. Chen, Ujani Hazra, MADCaP Network, Joseph Lachance. Genetic architecture, evolutionary genomics, and genomic risk of prostate cancer in sub-Saharan Africa [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 774.