TP53 Tumor Suppressor Research Articles

Abstract 1712: Targeting asparagine dependency as a therapy for TP53-mutated castration-resistant prostate cancer

Abstract Background: The TP53 tumor suppressor is frequently altered in lethal, castration-resistant prostate cancer (CRPC). However, to date there are no effective treatments that specifically target TP53 gain-of-function (GOF) mutants. Thus, there is an urgent need to identify and target vulnerabilities that perpetuate disease progression and treatment resistance resulting from TP53 GOF mutants. Methods: We performed RNA sequencing (RNA-seq) and liquid chromatography-mass spectrometry (LC-MS)-based metabolomics on GEM and PDX CRPC models with or without TP53 GOF mutations. Our findings were validated using genetic and pharmacologic approaches in relevant in vitro and in vivo models. We assessed the effect of L-asparaginase (ASNase) or/and glutaminase (GLS) inhibitor CB-839 in cell lines, organoids and PDX models. Tumors were characterized by histology and immunohistochemistry for relevant markers. Results: Using transcriptomic and metabolomic analyses, we show here that TP53-mutated prostate cancer (PCa) exhibits an increased dependency on asparagine and overexpresses asparagine synthetase (ASNS, the enzyme catalyzing the synthesis of asparagine). Mechanistically, TP53 GOF mutations transcriptionally activate ASNS expression, directly as well as via ATF4, driving de novo asparagine biosynthesis to support CRPC growth. TP53-mutated CRPC cells are sensitive to asparagine restriction by knockdown of ASNS and L-asparaginase treatment to deplete the intracellular and extracellular sources of asparagine respectively. This effect was rescued by asparagine addition. Notably, pharmacological inhibition of intracellular asparagine biosynthesis using a glutaminase (GLS) inhibitor and depletion of extracellular asparagine with L-asparaginase significantly reduced asparagine production and effectively impaired CRPC growth. Conclusions: This study highlights the significance of ASNS-mediated metabolic adaptation as a synthetic vulnerability in CRPC with TP53 GOF mutations, providing a rationale for co-targeting intracellular and extracellular asparagine production to treat these lethal prostate cancers. Citation Format: Young A Yoo. Targeting asparagine dependency as a therapy for TP53-mutated castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1712.

Abstract 3775: Multi-omic spatial analysis with simultaneous detection of small RNAs, mRNAs and proteins using the novel RNAscope™ Plus technology

Abstract Regulatory RNA molecules such as microRNAs (miRNA) and long non-coding RNAs play critical roles in regulating translation of mRNA to protein. Several miRNAs have been implicated in disease initiation and progression, especially in cancer. The regulatory mechanisms of miRNAs and other small RNAs such as antisense oligos (ASOs) and silencing RNAs (siRNA) have been exploited to develop oligonucleotide therapies for 1. undruggable targets, 2. achieving longer-term effects 3. rapid production of therapeutics and 4. lower drug development costs. These therapeutics have the promise to treat debilitating neurodegenerative diseases, rare and inherited disorders. RNA therapies are typically delivered as a part of nanoparticles or a viral vector. Regardless of the delivery mechanism, methods to understand the biodistribution of the vector, transgene expression and cell type identification in a spatial context is crucial to study the safety and efficacy of these therapies. Built on the flagship RNAscope technology, the RNAscope Plus assay can detect 1 small RNA and 3 mRNA targets using TSA-based fluorescent readouts and is compatible with the new fluorescent Vivid™ dyes. Fixed, fresh frozen samples and formalin fixed paraffin embedded (FFPE) tissues are supported by manual and automated workflows using the Leica Bond Rx system. We have leveraged this technology to investigate spatial expression profile of miRNA and associated RNA targets across different tissue types and applications. We can also combine protein detection using a target antibody to visualize cell-type specific markers. This assay was used to demonstrate expression of miRNAs and target genes implicated in tumor initiation, progression, and angiogenesis. Expression of miR-205, associated tumor target genes such as PanCK, PTEN and tumor suppressor TP53 was visualized in head and neck cancer tumors. Downregulation of tumor-suppressor, TP53 resulted in upregulation of miR-205 which downregulates PTEN expression. Pan-CK stained the tumor region in the tissue. Similarly, miR-155 expression was observed in niche areas within breast cancer, head and neck cancer and cervical cancer tumors. Expression of miR-155 demonstrated correlation with high VEGF expression suggesting its role in angiogenesis. This novel platform will enable researchers to visualize regulatory RNA simultaneously with target RNAs, cell-type and morphology markers in intact cells/tissues with single cell resolution. This technology can provide meaningful insights into disease pathology driven by miRNAs as well as assess biodistribution and efficacy of oligonucleotide therapeutics. Citation Format: Anushka Dikshit, Sayantani Basak, Sonali Deshpande, Manvir Sambhi, Li-Chong Wang, Maithreyan Srinivasan. Multi-omic spatial analysis with simultaneous detection of small RNAs, mRNAs and proteins using the novel RNAscope™ Plus technology. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3775.

Abstract 4749: Effects of miR-34a-5p and miR-181b-5p silencing and induction on their potential targets in uterine leiomyosarcoma cells

Abstract Background: Leiomyosarcoma (LMS) is a malignant tumor of the uterine body that represents 40-60% of all gynecological sarcomas. Up to now, there is no specific treatment or diagnostic biomarkers for this tumor. The identification and characterization of miRNAs signature could help to its management. In addition, miRNAs represent targets for therapies due to their ability to modulate various signaling pathways simultaneously. Thus, the present study aimed to evaluate the effects of genetic manipulation of miR-34a and miR-181b on their predicted target genes in LMS cells. Methods: SK-UT-1 cells from uterine LMS were transfected with synthetic miRNA mimics and inhibitors (siRNA) of miR-34a and miR-181b. The efficacy of transfection was assessed by miRNA expression (qRT-PCR) assays. In order to identify potential genetic interactions network of miR-34a and 181b, predicted target genes were selected by in silico analysis (miRTargetLink 2.0 and miRDB). After SK-UT-1 cells transfection, the expression of target genes was evaluated by qRT-PCR. Results: SK-UT-1 cells showed greater efficiency of mimics and siRNA transfections after 48h treatment for both miR-34a and 181b. MDM4, TP53, BCL2, KMT2D, NOTCH2, and CCND1 were identified as predicted target genes of miR-34a; and the TIMP3, FGFR1, BCL2, NOTCH2, ATM, and IRS1 target genes for miR-181b. Expression profile of selected target genes was assessed after each treatment. The miR-34a mimic significantly increased the expression of MDM4 after 96h of treatment, while the BCL2 and TP53 showed an increase in expression with siRNA after 48h of treatment. CCND1 showed a greater expression in both treatments at 48h. An increase in KMT2D and NOTCH2 expression was also observed after treatment, even though without statistically significant. Treatment with miR-181b mimic led to increased FGFR1 expression within 72h. Although some expression alterations were observed in TIMP3, BCL2, NOTCH2, ATM, and IRS1 genes after mimic and siRNA treatments, there was no statistical significance. Conclusion: The effect of miR-34a upregulation leads to induction MDM4 and CCND1 expression, the first being a TP53 inhibitor and the second, responsible for cell cycle maintenance. The miR-34a downregulation had an inductor effect on expression of MDM4, BCL2 (apoptosis regulator), TP53 (tumor suppressor), and CCND1. The miR-181b upregulation induced the expression of fibroblast growth factor receptor, FGFR1. In uterine LMS cells, miR-34a seems to exert an important role in regulating the expression of cell cycle and apoptosis-related genes. Citation Format: Bruna C. de Almeida, Laura G. dos Anjos, Katia C. Carvalho. Effects of miR-34a-5p and miR-181b-5p silencing and induction on their potential targets in uterine leiomyosarcoma cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4749.

Abstract 1563: Concomitant inhibition of Aurora kinase A and WEE1 kinases results in synergistic tumor control and heightens DNA replication stress in head and neck and lung carcinomas

Abstract Human papillomavirus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) and lung cancer mainly harbor disruptive mutations in TP53 and/or CDKN2A tumor suppressor genes, which are associated with refractoriness to treatment as well as poor prognosis and survival. Mutational loss of TP53 function fosters elevated expression of Aurora kinase A (AURKA) that plays a crucial role in mitotic progression at G2/M and stabilizes DNA replication forks at S phase. We have previously demonstrated that combined inhibition of AURKA and WEE1, a G2/M checkpoint kinase induced by replication stress, results in synergistic anti-tumor effects in HNSCC in vitro and in vivo. We have now further confirmed synergy using the highly selective AURKA inhibitor VIC1911 in HNSCC and lung cancers harboring TP53 mutations and explored mechanisms of cell death. VIC1911 and adavosertib combination synergistically suppressed cell growth and survival in both 2D- and 3D-culture systems relative to vehicle or single-agent treatment in TP53-mutated HNSCC FaDu and CAL27, and lung cancer A549 and NCI-H358 cells, with no observable toxicity in normal cells, predicting a favorable therapeutic index. Furthermore, combination treatment accelerated mitotic entry and resulted in accumulation of mitotic catastrophe, as demonstrated by time-lapse imaging, and apoptotic cell death as evidenced by cleaved PARP assays. Notably, we found that combination VIC1911 and adavosertib in HNSCC cells drastically slowed and stalled progression of replication forks in DNA fiber analysis (Mean: DMSO=3.117; adavosertib=1.495; VIC1911=0.9757; combination=0.5548 kb/min; P <0.0001) and amplified DNA damage as measured by γH2AX, indicating induction of severe replication stress. In vivo, this combination resulted in significant tumor regression in both HNSCC and lung adenocarcinoma patient-derived and cancer cell-derived xenografted mice compared with either vehicle or single-agent treatment. Taken together, these results suggest that AURKA inhibition increases dependency on WEE1 by enhancing replication stress and mitotic catastrophe, and support clinical evaluation of combined AURKA and WEE1 inhibition as a novel and effective treatment for HNSCC and lung cancer patients with elevated AURKA expression. Citation Format: Jong Woo Lee, Sundong Kim, Sebastian Cruz-Gomez, Jackie Shi, Cindy Yang, Barbara Burtness. Concomitant inhibition of Aurora kinase A and WEE1 kinases results in synergistic tumor control and heightens DNA replication stress in head and neck and lung carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1563.

Abstract 553: SKP2 knockout induces macrophage infiltration in p53/Rb1 null transgenic mouse models of osteosarcoma and drives gene expression correlated with improved survival in patients

Abstract Background: Osteosarcoma (OS) is an aggressive cancer of the bone with a poor prognosis. OS often involve mutations of tumor suppressors RB1 and TP53. One putative proto-oncogene in OS is SKP2, which codes for a substrate-recognition factor of the SCF E3 ubiquitin ligase. We have demonstrated that germline knockout of SKP2 in a pre-clinical transgenic mouse model of OS doubly deficient in Rb1 and Trp53 improved survival, delayed tumorigenesis, reduced malignant cell proliferation, slowed tumor growth, diminished stemness, and induced apoptosis. However, the role that SKP2 plays in OS progression remains unclear. Method: We performed bulk RNA-sequencing on pre-clinical transgenic mouse models of OS. To model OS in mice, we generated a conditional double-knockout line of Trp53 and Rb1 mutations induced in cells of the bone-forming osteoblast lineage via Cre-Lox recombination (“DKO”: Osx1-Cre;Rb1lox/lox;p53lox/lox). We compared this with a triple-knockout model, which additionally features a germline Skp2 knockout (“TKO”: Osx1-Cre;Rb1lox/lox;p53lox/lox;SKP2-/-). We compared tumors from the TKO and DKO models via bulk RNA-sequencing (n=3 per group) to study differential expression and immune infiltration. We used immunohistochemistry (IHC) and quantification to validate differences in immune markers between genotypes. Using the transcriptomic results from the mouse models, we analyzed a human OS patient cohort of 83 participants (NCI TARGET OS) with RNA-seq and clinical data via survival analysis to infer the impact of modulating SKP2 in OS patients. Result: We found a large difference in gene expression between the TKO and DKO models. Surprisingly, we observed a dramatic increase in the expression of genes related to immune microenvironment infiltration in TKO tumors compared to DKO. Macrophage transcriptomic signatures were the strongest signal detected (P<0.001), but significant increases in B cells, endothelial cells and T cell signatures were also observed. IHC also showed macrophage markers were higher in TKO (P = 0.08). In the NCI TARGET OS cohort, high expression of genes up-regulated in TKO was significantly correlated with 5-year overall survival (p=0.02). This effect was driven by macrophage transcriptomic signatures. This finding was supported by an immune microenvironment deconvolution analysis, which showed that macrophages and T cells were associated with improved overall survival in the patient cohort (p=0.01). We are currently performing single-cell RNA-sequencing analysis to study immune infiltration and cellular heterogeneity in more detail. Conclusion: Taken together, our new findings indicate that SKP2 modulation in OS may induce a vigorous anti-tumor immune activation especially in the form of macrophage and lymphocyte infiltration into the tumor microenvironment. Citation Format: Alexander Ferrena, Jichuan Wang, Ranxin Zhang, Rui Yang, David Geller, Bang Hoang, Deyou Zheng. SKP2 knockout induces macrophage infiltration in p53/Rb1 null transgenic mouse models of osteosarcoma and drives gene expression correlated with improved survival in patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 553.

Abstract 3950: Sensitizing oncogenic mutant p53-expressing non-small cell lung cancer to proteasome inhibitors

Abstract Background: Lung cancer is the leading cause of cancer deaths worldwide, with non-small cell lung cancer (NSCLC) accounting for ~80% of all lung cancers. Up to 69% of NSCLC are mutated for the tumor suppressor gene TP53, and of these, 84% are missense mutations, where wild-type (WT) TP53 tumor suppressor function is lost and in most cases, emergent cancer-promoting oncogenic activities are acquired. Due to the poor draggability of mutated p53 protein, the focus of therapeutics targeting NSCLC tumors with oncogenic missense mutant p53 has been on vulnerabilities that are not present in normal cells expressing WT p53. One such vulnerability involves oncogenic mutant p53-dependent attenuation of the oxidative stress response. The ability of cancer cells to survive oxidative stress depends on the regulated synthesis and activity of cellular antioxidants, including glutathione (GSH). Proteasome inhibitors (PIs) are known to induce cellular stress at multiple levels, including proteotoxic, autophagic, and oxidative stress, but the clinical utility of PIs has been limited by lack of efficacy in patients with solid tumors, including unselected lung cancer patients. Methods and Results: We now show bortezomib (BTZ) and other PIs are preferentially cytotoxic in oncogenic mutant p53-expressing lung cancer cells in culture. Furthermore, BTZ-treated oncogenic mutant p53-expressing cells display elevated levels of reactive oxygen species and BTZ’s cytotoxic effects were rescued by antioxidants such as N-acetyl cysteine, indicating that oxidative stress is the critical driver of BTZ cytotoxicity. Upon BTZ treatment of oncogenic mutant p53-expressing NSCLC cells, but not in WT p53 expressing NSCLC cells, we also observed the transcriptional induction of pro-apoptotic BH3-only BCL-2 family protein NOXA, consistent with an apoptotic mechanism of BTZ-induced cell death. Furthermore, in combination with BTZ, the use of BH3-mimetics such as venetoclax (ABT-199) or navitoclax (ABT-263) to inhibit the function of pro-survival proteins BCL-2/BCL-XL synergistically enhanced BTZ cytotoxicity, but only in oncogenic mutant p53-expressing NSCLC cells. In vivo mouse xenograft studies demonstrated that combination treatments of BTZ + venetoclax or BTZ + carboplatin (a standard of care chemotherapy for NSCLC) significantly attenuated oncogenic mutant p53-expressing tumor growth. Conclusions: Our data suggest that the preferential cytotoxicity of BTZ, and potentially other PIs, in oncogenic mutant p53-expressing NSCLC cells depends on the induction of toxic oxidative stress leading to NOXA-dependent apoptosis. Thus, combining PIs with drugs that limit antioxidant responses and/or sensitize cells to NOXA-induced apoptosis (e.g., BH3-mimetics) should synergistically and selectively kill NSCLC cells expressing oncogenic mutant p53 and open novel therapeutic avenues for the treatment of NSCLC. Citation Format: Kranthi Kumar Chougoni, Victoria L. Neely, Boxiao Ding, Eziafa Oduah, Khanh Nguyen, Bin Hu, Jennifer Koblinski, Bradford Windle, Hisashi Harada, Steven Grossman. Sensitizing oncogenic mutant p53-expressing non-small cell lung cancer to proteasome inhibitors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3950.

Abstract 53: Zebrafish tp53 mutants recapitulate Li-Fraumeni syndrome phenotypes and provide a preclinical platform for evaluating tumor preventive compounds

Abstract Background: Li-Fraumeni syndrome (LFS) is a hereditary cancer predisposition disorder associated with a highly penetrant and diverse tumor spectrum characterized by germline mutations in the TP53 tumor suppressor gene. Individuals with LFS experience early tumor onset, often during childhood, with a cumulative lifetime cancer risk of 68% in males and 93% in females. Being prone to multiple cancer diagnoses, individuals with LFS endure frequent long-term multi-modal cancer screening protocols, which have improved survival through early detection but are non-specific and can be very burdensome. Preclinical animal models recapitulating the genomic landscape observed in LFS offer the potential to define cancer-driving mechanisms in LFS to personalize tumor surveillance, while also providing a preclinical platform for testing molecularly targeted therapies. Zebrafish are a powerful cancer research tool due to their high degree of genetic conservation; histological/molecular similarities in tumor development with their human counterparts; optical clarity facilitating high-resolution imaging and non-invasive tumor screening. Experimental Design: We have generated two tp53 zebrafish point mutants, R217H and R242H, (representing commonly mutated human LFS and sporadic residues, R248 and R273H) and obtained tp53 null mutants (Langenau lab). The point mutants recapitulate LFS phenotypes, including partial-to-no expression of p53 target genes; resistance to p53-mediated apoptosis; dominant negative activity; and tp53 loss-of-heterozygosity in tumor tissue. These mutants develop tumors beginning at 6-9 months post-fertilization that histologically resemble human sarcomas. R242H mutants exhibit earlier tumor onset and higher life-time incidence than both R217H and null mutants, suggesting that this mutation is more aggressive. Additionally, R217H and R242H mutants each present with a distinctive anatomic tumor distribution and skewed sex ratios, indicating different tumor-driving mechanisms. Whole larvae RNA sequencing and DNA methylation analyses are in progress to reveal mutation-specific mechanisms and pathways, which may reveal novel molecular targets for therapeutic intervention. tp53 R217H and R242H mutants are currently being subjected to treatment with pCAPs (p53 conformation activating peptides) that restore p53 tumor-suppressive hallmarks and/or re-establish native p53 folding to potentially prevent tumor initiation. Significance: In sum, these zebrafish LFS models hold tremendous potential to unravel the pathogenesis of tumor formation in this cancer predisposition syndrome and facilitate a precision-medicine approach to cancer surveillance and prevention to increase survival and enhance quality of life for this vulnerable population. Citation Format: Kim Kobar, Erin Burnley, Lissandra Tuzi, Craig Midgen, Adam Shlien, David Malkin, Sergey V. Prykhozhij, Jason N. Berman. Zebrafish tp53 mutants recapitulate Li-Fraumeni syndrome phenotypes and provide a preclinical platform for evaluating tumor preventive compounds [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 53.

Abstract 6192: MSI2 regulates DNA damage response signaling and tumor progression in murine NSCLC

Abstract Lung cancer is one of the most frequently diagnosed cancers and is the leading cause of cancer-related death worldwide, accounting for >2.2 million of new cancer diagnoses and 1.8 million cancer-related deaths in 2020. Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, including adenocarcinomas and squamous cell carcinomas. Many lung adenocarcinomas have activating driver mutations in KRAS (~32% tumors), often co-occurring with mutations inactivating the TP53 tumor suppressor. Expression of the RNA-binding protein Musashi-2 (MSI2) MSI2 regulates target mRNA translation, and its expression is progressively elevated along with tumor stage in lung cancers. We previously showed that MSI2 actively promotes lung cancer growth, invasion, and metastasis, in part through promoting expression and activity of the TGFβR1/SMAD3 and EGFR signaling cascades. We now find that genetic MSI2 deficiency in a murine lung tumor model, Krasmut/Trp53KO/Msi2KO (KPM2) decreases both the total tumor number and tumor burden in comparison to control Krasmut/Trp53KO (KP) mice. Using a panel of KPM2 and KP cell lines we established from tumors from these mice, we found KPM2 cell lines demonstrate a significant decrease in proliferation compared to KP cell lines. Interestingly, reverse phase protein array (RPPA) comparison analysis of KPM2 and KP cell lines showed that MSI2 strongly and positively regulates expression of Ataxia-Telangiectasia Mutated (ATM) protein, with lower levels observed in KPM2 cells. The ATM serine/threonine protein kinase is a key transducer of DDR signaling in cases of double-strand breaks; ATM activation causes G1/S cell cycle arrest, contributes to efficiency of DNA repair, and triggers apoptosis in cases of repair failure. Notably, KPM2 cells showed significantly higher levels of γH2AX, suggesting inefficient DDR. Finally, untreated or cisplatin-treated KPM2 cells demonstrated G2/M arrest and had increased level of apoptosis as demonstrated by increase in caspase 3 cleavage, consistent with ATM loss and compensatory activation of Ataxia-telangiectasia and Rad3-related protein (ATR). Taken together, our data suggests that one of the consequences of MSI2 upregulation in NSCLC includes maintenance of an efficient DDR. Targeting MSI2 and its downstream signaling would be of therapeutic interest. Citation Format: Igor Bychkov, Alexander Deneka, Iuliia Topchu, Rajendra P. Pangeni, Christopher Lengner, Evgeny Izumchenko, Jyoti Patel, John Karanicolas, Petr Makhov, Yanis Boumber. MSI2 regulates DNA damage response signaling and tumor progression in murine NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6192.

The ubiquitin ligase TRIM21 regulates mutant p53 accumulation and gain of function in cancer.

The tumor suppressor TP53 is the most frequently mutated gene in human cancers. Mutant p53 (mutp53) proteins often accumulate to very high levels in human cancers to promote cancer progression through the gain-of-function (GOF) mechanism. Currently, the mechanism underlying mutp53 accumulation and GOF is incompletely understood. Here, we identified TRIM21 as a critical E3 ubiquitin ligase of mutp53 by screening for specific mutp53-interacting proteins. TRIM21 directly interacted with mutp53 but not WT p53, resulting in ubiquitination and degradation of mutp53 to suppress mutp53 GOF in tumorigenesis. TRIM21 deficiency in cancer cells promoted mutp53 accumulation and GOF in tumorigenesis. Compared with p53R172H knockin mice, which displayed mutp53 accumulation specifically in tumors but not normal tissues, TRIM21 deletion in p53R172H knockin mice resulted in mutp53 accumulation in normal tissues, an earlier tumor onset, and a shortened life span of mice. Furthermore, TRIM21 was frequently downregulated in some human cancers, including colorectal and breast cancers, and low TRIM21 expression was associated with poor prognosis in patients with cancers carrying mutp53. Our results revealed a critical mechanism underlying mutp53 accumulation in cancers and also uncovered an important tumor-suppressive function of TRIM21 and its mechanism in cancers carrying mutp53.

Abstract OT2-12-01: Clinical Application of LFSPRO: A Prospective Study

Abstract Background: Individuals with Li-Fraumeni Syndrome (LFS) have increased risk of developing cancers of several types, such as early-onset breast cancer, soft-tissue/bone sarcoma, leukemia, brain tumors, and more, throughout their lifetime. LFS is primarily caused by autosomal dominant germline mutations in the TP53 tumor suppressor gene. It is difficult to identify TP53 mutation carriers because of the overlap in the occurrence of multiple cancer types in LFS with other inherited cancer syndromes. In order to improve the accuracy of risk assessment for these families, the LFSPRO risk model was created to predict the likelihood of a proband having LFS based off detailed patient and family history information, as well as predict cancer-specific risks for patients who have already been identified as having LFS. Specific Aims: The primary aim of this study is to evaluate the concordance of LFSPRO and clinical criteria in predicting TP53 mutation status in patients undergoing germline TP53 testing. Trial Design: After receiving standard genetic counseling, patients identified as concerning for a potential TP53 mutation by a MD Anderson genetic counselor (GC) are run through LFSPRO. LFSPRO TP53 mutation carrier risk, whether the patient meets Chompret and/or Classic criteria, decision to test, and genetic test results are collected. Select GCs are then asked to complete a survey regarding their experience with LFSPRO. Eligibility Criteria: Through standard genetic counseling practice, MD Anderson GCs identify patients with a clinical suspicion for a TP53 germline mutation. All patients identified are run through LFSPRO. Out of these identified patients, select GCs that participated in the initial genetic counseling session are asked to complete a survey over their experience using the LFSPRO. Statistical methods: We will evaluate the concordance in the prediction of TP53 mutation carrier status between LFSPRO and current clinical criteria as compared to the outcome of genetic testing results. We will cross-tabulate the predicted TP53-mutation status (positive vs. negative) with the carrier status in a 2 × 2 table and calculate the sensitivity and specificity of each prediction tool separately (LFSPRO, clinical criteria), with 95% confidence interval. Accrual: Currently, 72 patients have been run through LFSPRO. Select GCs have completed the survey regarding their experience with LFSPRO on 20 of these patients. Data collection began in December 2021 and is currently ongoing. Funding: This research is supported by the Cancer Research and Prevention Institute of Texas. Contact: Jacynda Woodman-Ross, MS, CGC, The University of Texas MD Anderson Cancer Center, jawoodman@mdanderson.org Citation Format: Jacynda Woodman-Ross, Elissa Dodd-Eaton, Jessica Corredor, Sierra O. Green, Nam H. Nguyen, Nathaniel Hernandez, Courtney D. DiNardo, Wenyi Wang, Banu K. Arun. Clinical Application of LFSPRO: A Prospective Study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-12-01.

Abstract OT2-13-01: Willingness to Participate in a Trial Comparing Standard Genetic Counseling versus Genetic Counseling with Personalized Cancer Risks Estimates in Patients with Li-Fraumeni Syndrome

Abstract Background: Individuals with Li-Fraumeni Syndrome (LFS) have increased risk of developing breast cancer, sarcomas, brain tumors, leukemia, and other cancers throughout their lifetime. LFS is primarily caused by autosomal dominant germline mutations in the TP53 tumor suppressor gene. Due to the large number of cancers caused by LFS, and their variable age of presentation, each LFS family often presents very differently. Currently, standard genetic counseling for patients with LFS often involves general lifetime risk predictions for developing several primary cancers. At present, there are no standard tools available to help genetics providers obtain a personalized risk assessment for a patient with LFS based on their unique personal and family history data. To address this, the LFSPRO risk model was developed to estimate the likelihood of a proband having LFS, to provide cancer-specific risks of a first primary cancer, and to estimate risk of time to second primary cancer diagnosis by utilizing detailed personal and family history information. Specific Aims: This study aims to understand patients’ willingness to participate in a randomized trial comparing standard genetic counseling practice to personalized genetic counseling via LFSPRO risk estimates. Trial Design: Eligible patients or parents/guardians are invited via email to complete a survey assessing interest in a hypothetical clinical trial scenario where patients are randomized to receive one of two types of post-disclosure genetic counseling approaches: standard genetic counseling for TP53 results, involving generic risk predictions for developing cancers, or personalized risk information provided from LFSPRO. Following the hypothetical scenario, participants are asked about their perceived benefits and barriers to this research scenario and interest in receiving personalized risk results. Demographic information is also collected. Eligibility Criteria: Individuals who receive genetic counseling through MD Anderson Cancer Center genetics clinics specifically for TP53 genetic testing and who consent to undergo TP53 genetic testing or individuals who genetic testing already indicates a TP53 germline mutation are offered this survey. Patients must be 13 years or older to complete the survey, otherwise a parent/guardian may complete the survey on their behalf. Patients must have English fluency. Statistical methods: Descriptive statistics will be used to analyze the data and summarize the opinion of the participants. Accrual: Enrollment is set to open in July 2022. Currently, 157 patients have been identified to be invited to participate in the study. Funding: This research is supported by the Cancer Research and Prevention Institute of Texas. Contact: Jacynda Woodman-Ross, MS, CGC, The University of Texas MD Anderson Cancer Center, jawoodman@mdanderson.org Citation Format: Jacynda Woodman-Ross, Sierra O. Green, Jessica Corredor, Elissa Dodd-Eaton, Nathaniel Hernandez, Susan K. Peterson, Wenyi Wang, Banu K. Arun. Willingness to Participate in a Trial Comparing Standard Genetic Counseling versus Genetic Counseling with Personalized Cancer Risks Estimates in Patients with Li-Fraumeni Syndrome [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-13-01.

Altered HLA-A2-restricted TP53 epitope induces specific CTL cytotoxicity against hepatocellular carcinoma.

High-frequency mutation of the TP53 tumor suppressor gene is observed in multiple human cancers, which promotes cancer progression. However, the mutated gene-encoded protein may serve as a tumor antigen to elicit tumor-specific immune responses. In this study, we detected widespread expression of shared TP53-Y220C neoantigen in hepatocellular carcinoma with low affinity and low stability of binding to HLA-A0201 molecules. We substituted the amino acid sequences VVPCEPPEV with VLPCEPPEV in the TP53-Y220C neoantigen to yield a TP53-Y220C (L2) neoantigen. This altered neoantigen was found to increase affinity and stability and induce more cytotoxic T lymphocytes (CTLs), indicating improvements in immunogenicity. In vitro assays showed the cytotoxicity of CTLs stimulated by both TP53-Y220C and TP53-Y220C (L2) neoantigens against multiple HLA-A0201-positive cancer cells expressing TP53-Y220C neoantigens; however, the TP53-Y220C (L2) neoantigen showed higher cytotoxicity than the TP53-Y220C neoantigen against cancer cells. More importantly, in vivo assays demonstrated greater inhibition of hepatocellular carcinoma cell proliferation by TP53-Y220C (L2) neoantigen-specific CTLs relative to TP53-Y220C neoantigen in zebrafish and nonobese diabetic/severe combined immune deficiency mouse models. The results of this study demonstrate enhanced immunogenicity of the shared TP53-Y220C (L2) neoantigen, which has the potential as dendritic cells or peptide vaccines for multiple cancers.

Exploiting PRMT5 as a target for combination therapy in mantle cell lymphoma characterized by frequent ATM and TP53 mutations

Constant challenges for the treatment of mantle cell lymphoma (MCL) remain to be recurrent relapses and therapy resistance, especially in patients harboring somatic mutations in the tumor suppressors ATM and TP53, which are accumulated as therapy resistance emerges and the disease progresses, consistent with our OncoPrint results that ATM and TP53 alterations were most frequent in relapsed/refractory (R/R) MCL. We demonstrated that protein arginine methyltransferase-5 (PRMT5) was upregulated in R/R MCL, which predicted a poor prognosis. PRMT5 inhibitors displayed profound antitumor effects in the mouse models of MCL with mutated ATM and/or TP53, or refractory to CD19-targeted CAR T-cell therapy. Genetic knockout of PRMT5 robustly inhibited tumor growth in vivo. Co-targeting PRMT5, and ATR or CDK4 by using their inhibitors showed synergistic antitumor effects both in vitro and in vivo. Our results have provided a rational combination therapeutic strategy targeting multiple PRMT5-coordinated tumor-promoting processes for the treatment of R/R MCL with high mutation burdens.

Malathion alters the transcription of target genes of the tumour suppressor tp53 and cancerous processes in Colossoma macropomum: Mechanisms of DNA damage response, oxidative stress and apoptosis

Different classes of pesticides such as fungicides, herbicides, and insecticides, can induce differential expression of genes that are involved in tumorigenesis events in fish, including the expression of tumor suppressor tp53. The degree and duration of the stressful condition is decisive in defining which tp53-dependent pathway will be activated. Herein we evaluate the target genes expression that participates in the regulation pathway of the tumor suppressor tp53 and in the cancerous processes in tambaqui after exposure to malathion. Our hypothesis is that malathion promotes a gene response that is differentially regulated over time, with positive regulation of tp53 target genes related to the apoptotic pathway and a negative regulation of genes that promote antioxidant responses. The fish were exposed to a sublethal concentration of the insecticide for 6 and 48 h. Liver samples were used to analyze the expression of 11 genes using real-time PCR. Overall, the malathion promoted over time increases in tp53 expression and differential expression of tp53 related genes. The exposure resulted in the activation of damage response related genes, caused a positive expression of atm/atr genes. The pro-apoptotic gene bax was up-regulated and the anti-apoptotic bcl2 was down-regulated. Increased expression of mdm2 and sesn1 in the first hours of exposure and no effect on the antioxidant genes sod2 and gpx1 were also observed. We also witnessed an increase in the expression of the hif-1α gene, with no effect on ras proto-oncogene. The extension of this stressful condition accentuated tp53 transcription, and minimized the levels of mdm2, sens1 and bax; however, it down regulated the levels of bcl2 and the bcl2/bax ratio, which indicates the maintenance of the apoptotic response to the detriment of an antioxidant response.

Symphony in the crowd: Key genetic alterations in prostate cancer.

Androgen receptor (AR) signaling have been frequently targeted for treating prostate cancer (PCa). Even though primarily patients receive a good therapeutic outcome by targeting AR signaling axis, eventually it emerges resistance by altering the genetic makeup of prostate cells. However, to develop an effective therapeutic regime, it is essential to recognize key genetic alterations in PCa. The most common genetic alterations that give rise to distinct androgen different differentiation states are gene fusion of TMPRSS2 with ETS family genes, deletion, or mutation of tumor suppressor PTEN and TP53 gene, amplification or splicing of AR, altered DNA repair genes. In this review, we describe key genes and genetic changes that have been recognized to contribute to altered prostate environment.

The Relationship between Gene Polymorphisms od the XRCC1 and TP53 with the Gender of Children with Acute Leukemia.

The relevance of the study lies in the fact that although the role of polymorphism of some genes that are responsible for cell apoptosis and deoxyribonucleic acid repair in the development of acute leukemia has already been established, its relationship with the gender of patients has not been studied enough. This study was aimed at studying the relationship between the Arg399Gln polymorphism in the XRCC1 deoxyribonucleic acid repair gene and the Arg72Pro polymorphism in the TP53 tumor suppressor gene encoding the p53 protein with the gender of children with acute leukemia. The study included 100 newly diagnosed pediatric patients of Kyrgyz nationality (69 boys and 31 girls), among which there were 77 patients with acute lymphoblastic leukemia, 22 patients with acute myeloblastic leukemia and 1 patient with a biphenotypic variant. Determination of polymorphisms was carried out by PCR-RFLP analysis or polymerase chain reaction followed by an analysis of restriction fragment length polymorphism. The interrelation of the results obtained with the patients' gender was assessed using statistical methods. The study showed that there were no gender differences for all three genotypes of the Arg72Pro polymorphic marker of the tumor suppressor p53 (ТР53). Three Arg399Gln genotypes of the XRCC1 gene also did not depend on gender. However, with a separate analysis of each polymorphism, there was a tendency for a greater proportion of the Arg/Gln genotype in the group of boys compared to girls. The Gln/Gln polymorphism relationship requires further study due to insufficient data for analysis. The study has expanded the understanding of genetic changes and their relationship with gender, which have diagnostic, prognostic and therapeutic implications in acute leukemia. The conducted research of the relationship between individual phenotypes of acute lymphoblastic leukemia with risky polymorphisms in some genes contributes to the study of AL.

TP53 gain of function mutation as a prognostic factor in high-methylated metastatic colorectal cancer: Translational research of TRICOLORE study.

179 Background: TP53 tumor suppressor gene is frequently inactivated by loss-of-function mutations. Some of the mutations gain additional oncogenic functions and are known as gain-of-function (GOF) mutations. This study analyzed the association among primary tumor site (PS), genome-wide DNA methylation status (GWMS), and TP53 mutation subtypes about prognosis in metastatic colorectal cancer (mCRC). Methods: Tumor tissues of mCRC patients registered in the TRICOLORE Study (clinical trial number) were analyzed for GWMS and TP53 mutation as translational research and were classified into high-methylated colorectal cancer (HMCC) and low-methylated colorectal cancer (LMCC) for GWMS, and wild-type , GOF mutation and non-GOF mutation for TP53 mutation. Overall survival (OS) was compared between single or combined subgroups, and Cox regression analysis was performed to identify factors contributing to OS. Results: A total of 209 patients were analyzed, HMCC and LMCC were 60 (28.7%) and 149 (71.3%), respectively. TP53 wild-type , GOF mutation and non-GOF mutation were 35 (16.7%), 79 (37.8%) and 95 (45.5%), respectively. HMCC showed a significantly worse prognosis than LMCC (median OS 25.3 vs. 40.3 months, P < 0.01, hazard ratio 1.87). Combining GWMS and TP53 mutation subtypes about prognosis, the HMCC/GOF (n = 26) group had a significantly poorer prognosis than the other three groups including HMCC/non-GOF (n = 22), LMCC/GOF (n = 53), and LMCC/non-GOF groups (n = 73) (median OS 17.7, 35.3, 40.3, 41.2 months, p = 0.007, p < 0.001, p < 0.001, respectively). The HMCC/GOF group had a poorer prognosis than the other 3 groups regardless of the PS. In the multivariate analysis in the GOF mutation subgroup, HMCC (p < 0.01) was the only poor prognostic factor, while right-sided colon cancer (p = 0.03) and RAS mutations (p = 0.01) were significant poor prognostic factors in the multivariate analysis in the non-GOF mutation subgroup. Conclusions: TP53 gain of function mutations are independent poor prognostic factors in high-methylated metastatic colorectal cancer.

NEMO- and RelA-dependent NF-κB signaling promotes small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive type of lung cancer driven by combined loss of the tumor suppressors RB1 and TP53. SCLC is highly metastatic and despite good initial response to chemotherapy patients usually relapse, resulting in poor survival. Therefore, better understanding of the mechanisms driving SCLC pathogenesis is required to identify new therapeutic targets. Here we identified a critical role of the IKK/NF-κB signaling pathway in SCLC development. Using a relevant mouse model of SCLC, we found that ablation of NEMO/IKKγ, the regulatory subunit of the IKK complex that is essential for activation of canonical NF-κB signaling, strongly delayed the onset and growth of SCLC resulting in considerably prolonged survival. In addition, ablation of the main NF-κB family member p65/RelA also delayed the onset and growth of SCLC and prolonged survival, albeit to a lesser extent than NEMO. Interestingly, constitutive activation of IKK/NF-κB signaling within the tumor cells did not exacerbate the pathogenesis of SCLC, suggesting that endogenous NF-κB levels are sufficient to fully support tumor development. Moreover, TNFR1 deficiency did not affect the development of SCLC, showing that TNF signaling does not play an important role in this tumor type. Taken together, our results revealed that IKK/NF-κB signaling plays an important role in promoting SCLC, identifying the IKK/NF-κB pathway as a promising therapeutic target.

A t(4;13)(q21;q14) translocation in B-cell chronic lymphocytic leukemia causing concomitant homozygous DLEU2/miR15a/miR16-1 and heterozygous ARHGAP24 deletions

13q14 deletion is the most recurrent chromosomal aberration reported in B-CLL, having a favorable prognostic significance when occurring as the sole cytogenetic alteration. However, its clinical outcome is also related to the deletion size and number of cells with the del(13)(q14) deletion. In 10% of cases, 13q14 deletion arises following a translocation event with multiple partner chromosomes, whose oncogenic impact has not been investigated so far due to the assumption of a possible role as a passenger mutation.Here, we describe a t(4;13)(q21;q14) translocation occurring in a B-CLL case from the diagnosis to spontaneous regression. FISH and SNP-array analyses revealed a heterozygous deletion at 4q21, leading to the loss of the Rho GTPase Activating Protein 24 (ARHGAP24) tumor suppressor gene, down-regulated in the patient RNA, in addition to the homozygous deletion at 13q14 involving DLEU2/miR15a/miR16–1 genes. Interestingly, targeted Next Generation Sequencing analysis of 54 genes related to B-CLL indicated no additional somatic mutation in the patient, underlining the relevance of this t(4;13)(q21;q14) aberration in the leukemogenic process.In all tested RNA samples, RT-qPCR experiments assessed the downregulation of the PCNA, MKI67, and TOP2A proliferation factor genes, and the BCL2 anti-apoptotic gene as well as the up-regulation of TP53 and CDKN1A tumor suppressors, indicating a low proliferation potential of the cells harboring the aberration. In addition, RNA-seq analyses identified four chimeric transcripts (ATG4B::PTMA, OAZ1::PTMA, ZFP36::PTMA, and PIM3::BRD1), two of which (ATG4B::PTMA and ZFP36::PTMA) failed to be detected at the remission, suggesting a possible transcriptional remodeling during the disease course. Overall, our results indicate a favorable prognostic impact of the described chromosomal aberration, as it arises a permissive molecular landscape to the spontaneous B-CLL regression in the patient, highlighting ARHGAP24 as a potentially relevant concurrent alteration to the 13q14 deletion in delineating B-CLL disease evolution.

Effects of chloroquine and hydroxychloroquine on the sensitivity of pancreatic cancer cells to targeted therapies.

Approaches to improve pancreatic cancer therapy are essential as this disease has a very bleak outcome. Approximately 80% of pancreatic cancers are pancreatic ductal adenocarcinomas (PDAC). PDAC is a cancer which is difficult to effectively treat as it is often detected late in the disease process. Almost all PDACs (over 90%) have activating mutations in the GTPase gene KRAS. These mutations result in constitutive KRas activation and the mobilization of downstream pathways such as the Raf/MEK/ERK pathway. Small molecule inhibitors of key components of the KRas/Raf/MEK/ERK pathways as well as monoclonal antibodies (MoAbs) specific for upstream growth factor receptors such insulin like growth factor-1 receptor (IGF1-R) and epidermal growth factor receptors (EGFRs) have been developed and have been evaluated in clinical trials. An additional key regulatory gene frequently mutated (∼75%) in PDAC is the TP53 tumor suppressor gene which controls the transcription of multiple genes involved in cell cycle progression, apoptosis, metabolism, cancer progression and other growth regulatory processes. Small molecule mutant TP53 reactivators have been developed which alter the structure of mutant TP53 protein and restore some of its antiproliferative activities. Some mutant TP53 reactivators have been examined in clinical trials with patients with mutant TP53 genes. Inhibitors to the TP53 negative regulator Mouse Double Minute 2 (MDM2) have been developed and analyzed in clinical trials. Chloroquine and hydroxychloroquine are established anti-malarial and anti-inflammatory drugs that also prevent the induction of autophagy which can have effects on cancer survival. Chloroquine and hydroxychloroquine have also been examined in various clinical trials. Recent studies are suggesting effective treatment of PDAC patients may require chemotherapy as well as targeting multiple pathways and biochemical processes.