Homologous Recombination-related Genes Research Articles

UBAP2 contributes to radioresistance by enhancing homologous recombination through SLC27A5 ubiquitination in hepatocellular carcinoma

Radiotherapy stands as an effective method in the clinical treatment of hepatocellular carcinoma (HCC) patients. However, both primary and acquired radioresistance limit its clinical application in HCC. Therefore, investigating the mechanism of radioresistance may provide other options for treating HCC. Based on single-cell RNA sequencing (scRNA-seq) and HCC transcriptome datasets, 227 feature genes with prognostic value were selected to establish the tSNE score. The tSNE score emerged as an independent prognostic factor for HCC and correlated with cell proliferation and radioresistance-related biological functions. UBAP2 was identified as the most relevant gene with the tSNE score, consistently elevated in human HCC samples, and positively associated with patient prognosis. Functionally, UBAP2 knockdown impeded HCC development and reduced radiation resistance in vitro and in vivo. The ectopic expression of SLC27A5 reversed the effects of UBAP2. Mechanically, we uncovered that UBAP2, through the ubiquitin-proteasome system, decreased the homologous recombination-related gene RAD51, not the non-homologous end-joining (NHEJ)-related gene CTIP, by degrading the antioncogene SLC27A5, thereby generating radioresistance in HCC. The findings recapitulated that UBAP2 promoted HCC progression and radioresistance via SLC27A5 stability mediated by the ubiquitin-proteasome pathway. It was also suggested that targeting the UBAP2/SLC27A5 axis could be a valuable radiosensitization strategy in HCC.

APLF facilitates interstrand DNA crosslink repair and replication fork protection to confer cisplatin resistance.

Replication stress converts the stalled forks into reversed forks, which is an important protection mechanism to prevent fork degradation and collapse into poisonous DNA double-strand breaks (DSBs). Paradoxically, the mechanism also acts in cancer cells to contribute to chemoresistance against various DNA-damaging agents. PARP1 binds to and is activated by stalled forks to facilitate fork reversal. Aprataxin and polynucleotide kinase/phosphatase-like factor (APLF) binds to PARP1 through the poly(ADP-ribose) zinc finger (PBZ) domain and is known to be involved in non-homologous end joining (NHEJ). Here, we identify a novel function of APLF involved in interstrand DNA crosslink (ICL) repair and fork protection. We demonstrate that PARP1 activity facilitates the APLF recruitment to stalled forks, enabling the FANCD2 recruitment to stalled forks. The depletion of APLF sensitizes cells to cisplatin, impairs ICL repair, reduces the FANCD2 recruitment to stalled forks, and results in nascent DNA degradation by MRE11 nucleases. Additionally, cisplatin-resistant cancer cells show high levels of APLF and homologous recombination-related gene expression. The depletion of APLF sensitizes cells to cisplatin and results in fork instability. Our results reveal the novel function of APLF to facilitate ICL repair and fork protection, thereby contributing to cisplatin-resistant phenotypes of cancer cells.

Association between Homologous Recombination Repair Defect Status and Long-Term Prognosis of Early HER2-Low Breast Cancer: A Retrospective Cohort Study.

As a newly identified subtype of HER2-negative tumors associated with a less favorable prognosis, it remains crucial to evaluate potential prognostic and predictive factors, particularly non-invasive biomarkers, for individuals with human epidermal growth factor 2 (HER2) low early-stage breast cancer (EBC). Multiple investigations have highlighted that HER2-negative patients with EBC exhibiting high homologous recombination deficiency (HRD) scores display lower rates of pathological complete response (PCR) to neoadjuvant chemotherapy (NAC). Nevertheless, no study to date has explored the correlation between HRD and the long-term prognosis in HER2-low patients with EBC. This retrospective observational study focuses on primary EBC sourced from The Cancer Genome Atlas dataset (TCGA). It reveals the gene mutation landscape in EBC with low HER2 expression and elucidates the tumor immune landscape across different HRD states. Utilizing bioinformatics analysis and Cox proportional models, along with the Kaplan-Meier method, the study assesses the correlation between HRD status and disease-specific survival (DSS), disease-free interval (DFI), and progression-free interval (PFI). Subgroup analyses were conducted to identify potential variations in the association between HRD and prognosis. In the patients with HER2-low breast cancer, patients with homologous recombination related genes (HRRGs) defects had an HRD score about twice that of those without related genes mutations, and were at higher risk of acquiring ARID1A, ATM, and BRCA2 mutations. We also found that most immune cell abundances were significantly higher in EBC tumors with high HRD than in EBC tumors with low HRD or HRD-medium, particularly plasma B-cell abundance, CD8 T-cell abundance, and M1 macrophages. In addition, these tumors with HRD-high also appear to have significantly higher tumor immune scores and lower interstitial scores. Then, we analyzed the relationship between different HRD status and prognosis. There was statistical significance (P = .036 and P = .046, respectively) in DSS and PFI between the HRD-low and HRD-high groups, and patients with HRD-high EBC showed relatively poor survival outcomes. A medium HRD score (hazard ratio, HR = 2.15, 95% CI: 1.04-4.41, P = .038) was a significant risk factor for PFI. Hormone receptor positivity is an important factor in obtaining medium-high HRD score and poor prognosis. Higher HRD scores were associated with poorer PFI outcomes, particularly in people with HR+/HER2-low. Varied HRD states exhibited distinctions in HRRGs and the tumor immune landscape. These insights have the potential to assist clinicians in promptly identifying high-risk groups and tailoring personalized treatments for patients with HER2-low EBC, aiming to enhance long-term outcomes.

Homologous Recombination Deficiency Unrelated to Platinum and PARP Inhibitor Response in Cell Line Libraries

While large publicly available cancer cell line databases are invaluable for preclinical drug discovery and biomarker development, the association between homologous recombination deficiency (HRD) and drug sensitivity in these resources remains unclear. In this study, we comprehensively analyzed molecular profiles and drug screening data from the Cancer Cell Line Encyclopedia. Unexpectedly, gene alterations in BRCA1/2 or homologous recombination-related genes, HRD scores, or mutational signature 3 were not positively correlated with sensitivity to platinum agents or PARP inhibitors. Rather, higher HRD scores and mutational signature 3 were significantly associated with resistance to these agents in multiple assays. These findings were consistent when analyzing exclusively breast and ovarian cancer cell lines and when using data from the COSMIC Cell Line Project. Collectively, the existing data from established cancer cell lines do not reflect the expected association between HRD status and drug response to platinum agents and PARP inhibitors in clinical tumors. This discrepancy may extend to other tumor characteristics, highlighting the importance of recognizing potential limitations in cell line data for researchers.

Genomic profile and clinical features of MSI-H and TMB-high pancreatic cancers: real-world data from C-CAT database.

Microsatellite instability high (MSI-H) and tumor mutational burden high (TMB-high) pancreatic cancer are rare, and information is lacking. Based on the C-CAT database, we analyzed the clinical and genomic characteristics of patients with these subtypes. We retrospectively reviewed data on 2206 patients with unresectable pancreatic adenocarcinoma enrolled in C-CAT between July 2019 and January 2022. The clinical features, proportion of genomic variants classified as oncogenic/pathogenic in C-CAT, overall response rate (ORR), disease control rate (DCR), and time to treatment failure (TTF) of chemotherapy as first-line treatment were evaluated. Numbers of patients with MSI-H and TMB-high were 7 (0.3%) and 39 (1.8%), respectively. All MSI-H patients were TMB-high. MSI-H and TMB-high patients harbored more mismatch repair genes, such as MSH2, homologous recombination-related genes, such as ATR and BRCA2, and other genes including BRAF, KMT2D, and SMARCA4. None of the 6 MSI-H patients who received chemotherapy achieved a clinical response, including 4 patients treated with gemcitabine plus nab-paclitaxel (GnP) therapy, whose DCR was significantly lower than that of microsatellite stable (MSS) patients (0 vs. 67.0%, respectively, p = 0.01). Among the TMB-high and TMB-low groups, no significant differences were shown in ORR, DCR (17.1 vs. 23.1% and 57.1 vs. 63.1%, respectively), or median TTF (25.9 vs. 28.0weeks, respectively) of overall first-line chemotherapy. MSI-H and TMB-high pancreatic cancers showed some distinct genomic and clinical features from our real-world data. These results suggest the importance of adapting optimal treatment strategies according to the genomic alterations.

Differential expression of meiosis and homologous recombination-related genes in the life cycle of Trypanosoma cruzi.

Trypanosoma cruzi has a complex life cycle consisting of four morphological and distinct biological stages. Although some authors suggest that T. cruzi primarily follows clonal reproduction, recent genomic and transcriptomic studies indicate an unorthodox capacity for recombination. We aimed to estimate the differential gene expression of 10 meiosis/homologous recombination-related genes during the T. cruzi life cycle, including epimastigotes, under two different types of stress (oxidative stressand pH changes). We performed RT-qPCR tests using novel-designed primers to estimate the differential gene expression (∆Ct and ∆∆Ct) of nine genes (SPO11, HAP2, RAD50, MRN complex, BRCA2, DMC1, MND1, and RPA1) and RAD51, which was previously reported. Our results show basal expression of all genes during the life cycle, indicating their hypothetical role in several cellular processes but with specific signatures of differential gene expression during the life cycle (HAP2, RPA, RAD50, BRCA2, MND1, and DMC1) and oxidative stress (RPA, MRE11, NBS1, BRCA2, MND1, and RAD51). Additionally, we found that the MRN complex has an independent level of expression in T. cruzi, with profiles of MRE11 and NBS1 upregulated in some stages. Recent studies on other trypanosomatids have highlighted the influence of HAP2 and RPA in recombination and hybridization. If T. cruzi uses the same repertoire of genes, our findings could suggest that metacyclogenesis may be the putative step that the parasite uses to undergo recombination. Likewise, our study reveals the differential profiles of genes expressed in response to oxidative and pH stress. Further studies are necessary to confirm our findings and understand the recombination mechanism in T. cruzi.

Homologous recombination-related (HRR) gene mutation profiling and the association with TMB in Chinese patients with pancreatic cancer.

e16252 Background: Homologous recombination deficiency (HRD) is associated with tumorigenesis and could predict the response of PARP inhibitor (PARPi) therapy and immunotherapy. Loss of function or deleterious mutations in homologous recombination-related (HRR) genes contribute to HRD phenotype. Methods: Tumor tissue samples from 669 Chinese patients with pancreatic cancer were sequenced with 551 cancer-related genes. Based on the clinical evidence, 15 HRR genes ( ATM, BRCA1, BRCA2, BARD1, BRIP1, CDK12, CHEK1, CHEK2, FANCL, PALB2, RAD51B, RAD51C, RAD51D, RAD54L, PPP2R2A) were selected. 495 patients with WES data from the TCGA datasets were included for analysis. Results: In the Chinese cohort, 10.46% (70/669) patients exhibited somatic HRR (sHRR) gene mutations. ATM (4%) was the most common mutant gene, followed by BRCA2 (3%), BARD1 (1%), BRCA1 (1%), BRIP1 (1%), RAD51D (1%), CHEK2(1%). The germline HRR (gHRR) gene mutations were identified in 55.67% (118/245) patients. BRCA2 (23%) was the most common mutant gene, followed by ATM (10%), BRCA1 (9%), BRIP1 (9%), PALB2 (8%), BARD1 (7%), FANCL (3%). 1.49% (10/669) patients carried both germline and somatic HRR gene mutations. The sHRR-Mut patients had a higher median TMB compared to the sHRR-WT patients (3.97 vs 2.13, p<0.001). However, the median TMB was similar between the gHRR-Mut and the gHRR-WT patients (2.13 vs 2.13, p=0.49). In the TCGA cohort, 9.09% (45/495) patients exhibited sHRR gene mutations. The most common mutant gene was ATM (4%), followed by CDK12 (2%) BRCA2 (2%), BARD1 (1%). The sHRR-Mut patients had a higher median TMB compared to the sHRR-WT patients (1.03 vs 0.71, p<0.001). Totally, the somatic mutant frequency of HRR genes was similar between Chinese cohort and TCGA cohort (10.46% vs 9.09%, p = 0.113). For the TCGA cohort, the patients with sHRR-Mut had a similar median progression free survival compared to the ones with sHRR-WT (74.4 months vs not reached, p = 0.299). Conclusions: Our data reported the genetic landscape of HRR gene in Chinese pancreatic cancer patients. Patients with somatic HRR gene mutations had a significantly elevated TMB level. Our data suggest that patients with altered HRR genes may be rational candidates for precision oncology treatment and provide new opportunities to predict the tumor response to multiple treatments.

Homologous recombination-related (HRR) gene mutation profiling and the association with TMB in Chinese patients with urological cancer.

e16561 Background: Homologous recombination deficiency (HRD) is associated with tumorigenesis and could predict the response of PARP inhibitor (PARPi) therapy and immunotherapy. Loss of function or deleterious mutations in homologous recombination-related (HRR) genes contribute to HRD phenotype. Methods: Tumor tissue samples from 484 Chinese patients with urological cancer were sequenced with 551 cancer-related genes. 957 patients with WES data from the TCGA datasets were included for analysis. Results: In the Chinese cohort, 35.88% (47/131) bladder cancer (BCa) patients, 15.47% (28/181) renal cell carcinoma (RCC) and 37.21% (64/172) prostate cancer (PCa) patients exhibited somatic HRR (sHRR) gene mutations. The most frequently mutated genes were BRCA2 (12% in BCa, 5% in RCC) and CDK12 (17% in PCa), respectively. The germline HRR (gHRR) gene mutations were identified in 62.6% (82/131) BCa, 55.33% (96/180) RCC and 60.62% (97/160) PCa patients. The most frequently mutated gene was BRCA2 (24% in BC, 18% in RCC, 26% in PCa). 7.6% (10/131) BCa patients, 1.7% (3/181) RCC patients and 2.9% (5/173) Pca patients carried both germline and somatic HRR gene mutations. In the TCGA cohort, 38.69% (159/411) BCa patients, 11.62% (43/370) RCC and 6.25% (11/176) PCa patients exhibited somatic HRR (sHRR) gene mutations. The most frequently mutated gene was ATM (14% in BCa, 4% in RCC, 5% in PCa). Interestingly, for the patients with PCa, the somatic mutant frequency of HRR genes in Chinese cohort was higher than that in TCGA cohort (37.21% vs 6.25%, p < 0.001). The sHRR-Mut patients had a higher median TMB compared to the sHRR-WT patients (Chinese cohort: BCa 13.97 vs 4.96, p < 0.001; RCC, 4.96 vs 2.84, p < 0.001; PCa, 5.64 vs 2.84, p < 0.001, TCGA cohort: BCa, 7.21 vs 3.63, p < 0.001; RCC, 1.68 vs 1.42, p = 0.003; PCa, 1.03 vs 0.71, p < 0.001). However, the median TMB was similar between the gHRR-Mut and the gHRR-WT patients (Chinese cohort, BCa 6.38 vs 7.09 p = 0.646; RCC, 3.55 vs 2.84, p = 0.229; PCa, 3.55 vs 2.84, p = 0.111). Conclusions: Our data reported the genetic landscape of HRR gene in Chinese urological cancer patients and suggested that patients with altered HRR genes may be rational candidates for precision oncology treatment and provide new opportunities to predict the tumor response to multiple treatments.

Homologous recombination-related (HRR) gene mutation profiling and the association with TMB in Chinese patients with esophageal and gastric cancer.

e16000 Background: Homologous recombination deficiency (HRD) is associated with tumorigenesis and could predict the response of PARP inhibitor (PARPi) therapy and immunotherapy. Loss of function or deleterious mutations in homologous recombination-related (HRR) genes contribute to HRD phenotype. Methods: Tumor tissue samples from 1237 Chinese patients with esophageal and gastric cancer were sequenced with 551 cancer-related genes. Based on the clinical evidence, 15 HRR genes ( ATM, BRCA1, BRCA2, BARD1, BRIP1, CDK12, CHEK1, CHEK2, FANCL, PALB2, RAD51B, RAD51C, RAD51D, RAD54L, PPP2R2A) were selected. 623 patients with WES data from the TCGA datasets were included for analysis. Results: In the Chinese cohort, 25.1% (62/247) esophageal cancer (EC) patients and 20.71% (205/990) gastric cancer (GC) patients exhibited somatic HRR (sHRR) gene mutations. The most frequently mutated genes were CHEK2 (7%) in EC and ATM (8%) in GC. The germline HRR (gHRR) gene mutations were identified in 48.16% (118/245) EC patients and 50.66% (498/983) GC patients. BRCA2 was the most common mutant gene (22% in EC and 9% in GC). 4.84% EC patients and 4.14% GC patients carried both germline and somatic HRR gene mutations. The sHRR-Mut patients had a higher median TMB compared to the sHRR-WT patients (EC, 8.09 vs 4.41, p < 0.001; GC, 8.09 vs 4.26, p < 0.001). However, the median TMB was similar between the gHRR-Mut and the gHRR-WT patients (EC, 5.67 vs 5.67, p = 0.903; GC, 4.96 vs 4.41, p = 0.356). In the TCGA cohort, 15.68% (29/185) EC patients and 23.97% (105/438) GC patients exhibited sHRR gene mutations. The most common mutant gene was ATM (5% in EC and 10% in GC). The sHRR-Mut patients had a higher median TMB compared to the sHRR-WT patients (EC, 4.78 vs 2.75, p < 0.001; GC, 21.23 vs 2.65, p < 0.001). For the TCGA gastric cancer cohort, the patients with sHRR-Mut had a significantly better median overall survival compared to the ones with sHRR-WT (46.9 months vs 26.5 months, p = 0.043). Conclusions: Our data reported the genetic landscape of HRR genes in Chinese esophageal and gastric cancer patients. Patients with somatic HRR gene mutations had a significantly elevated TMB level. In gastric cancer, patients carried somatic HRR gene mutations had a significantly prolonged OS.

Genomic and molecular landscape of homologous recombination deficiency across multiple cancer types

Homologous recombination deficiency (HRD) causes faulty double-strand break repair and is a prevalent cause of tumorigenesis. However, the incidence of HRD and its clinical significance in pan-cancer patients remain unknown. Using computational analysis of Single-nucleotide polymorphism array data from 10,619 cancer patients, we demonstrate that HRD frequently occurs across multiple cancer types. Analysis of the pan-cancer cohort revealed that HRD is not only a biomarker for ovarian cancer and triple-negative breast cancer, but also has clinical prognostic value in numerous cancer types, including adrenocortical cancer and thymoma. We discovered that homologous recombination–related genes have a high mutation or deletion frequency. Pathway analysis shows HRD is positively correlated with the DNA damage response and the immune-related signaling pathways. Single cell RNA sequencing of tumor-infiltrating lymphocytes reveals a significantly higher proportion of exhausted T cells in HRD patients, indicating pre-existing immunity. Finally, HRD could be utilized to predict pan-cancer patients’ responses to Programmed cell death protein 1 immunotherapy. In summary, our work establishes a comprehensive map of HRD in pan-cancer. The findings have significant implications for expanding the scope of Poly ADP-ribose polymerase inhibitor therapy and, possibly, immunotherapy.

Potential therapeutic implications of next generation sequencing (NGS)-based molecular profiling in HR+/HER2- metastatic breast cancer (mBC).

e13079 Background: BC is the most frequent malignancy in women and is potentially sensitive to hormonal treatment (HR+, HER2+ or -) in approximately 70% of cases. PIK3CA is among the most frequently mutated genes in BC (approximately 40% of cases) and its mutations portend sensitivity to PI3K inhibitors, such as alpelisib, in combination with hormonal treatment in HR+/HER2- cases. However, extended NGS-based testing is not currently recommended by national and international guidelines. Methods: Women aged 18 years or older, with cytological or histological diagnosis of HR+/HER2- mBC, for whom suitable tissue samples were available, were subjected to extended NGS profiling using the FoundationOne, analyzing 324 genes and gene signatures, such as tumor mutational burden (TMB) and microsatellite instability (MSI); and Illumina TruSight Oncology 500, analyzing 500 genes. DNA was isolated from formalin-fixed, paraffin-embedded (FFPE) samples, from either the primary or metastatic site. Results: Patients (pts) were analyzed (ductal histology: 52%; lobular: 15%; mixed ductal-lobular: 12%; NOS: 21%), among which 7 (12%) had inadequate pathological material and were considered screening failures. A full molecular report was obtained in 53 patients. The most frequent pathogenic and likely pathogenic alterations (class 5 and 4), listed in descending order of prevalence, are: PIK3CA in 51% of pts (E545K>H1047R>N345K>E542K); CDH1 in 21% (prevalence in lobular carcinoma: 75%; in ductal carcinoma: 3,5%). CCND1 in 28% (all amplifications). FGFR1-2 in 21%, TP53 in 15%, WHSC1L1 and ZNF703 in 13%, RAD21 and TBX3 in 9%. Homologous recombination-related genes, such as BRCA1/2 and PALB2 were altered in <5% while ATM altered in 9% of cases. Many other pathogenic mutations (affecting 69 individual genes) were identified, all with a prevalence <10%. TMB was high (>17 mutations/Mb) in 13% of cases, in one of which MSI was also detected. Conclusions: In our analysis PIK3CA was confirmed to be the most frequently mutated gene (51% of cases); however, due to the specific European regulatory constraints, it was deemed to be actionable in a minority of cases, suggesting that NGS profiling should be performed early on after the diagnosis of metastatic disease, in order to inform the overall therapeutic strategy. Other potentially actionable alterations (FGFR1/2, AKT, HER2 ex 20 mutations) emerged from extended NGS profiling, suggesting its potential utility in selected HR+/HER2- mBC pts.

Germline variants in non-BRCA1/2 homologous recombination-related genes and ovarian cancer: Analysis of tumor phenotype and survival.

5565 Background: BRCA1/2-associated ovarian cancer (OC) exhibits homologous recombination (HR)-deficiency (HRD) and a better prognosis than BRCA1/2-wildtype (WT) OC. However, it is unclear if patients with germline pathogenic variants (gPV) in other HR-related genes have a similar tumor phenotype. We sought to define OC molecular features from patients with gPV in other HR genes and analyze survival compared to patients with BRCA1/2 and WT OC. Methods: We identified patients with OC treated at our institution who underwent tumor-normal sequencing using MSK-IMPACT targeting 341-505 cancer-related genes with germline analysis of ≥76 genes from 7/2015-12/2020. Biallelic inactivation was inferred via assessments of loss of heterozygosity (LOH) at gPV in non- BRCA1/2 HR-related genes ( ATM, BARD1, BRIP1, FANCA, FANCC, NBN, PALB2, RAD50, RAD51B, RAD51C, and RAD51D). Clinical characteristics were compared to patients with BRCA1/2-associated and WT OC using non-parametric tests. Progression-free (PFS) and overall-survival (OS) were calculated from date of pathologic diagnosis using the Kaplan-Meier method. Left truncation at date of MSK-IMPACT consent was applied. Whole-exome sequencing (WES) was performed in a subset of OCs. Results: Of 882 patients with OC, 56 (6.3%) had gPV in non- BRCA1/2 HR-related genes compared to 95 (10.8%) patients with BRCA1-associated OC (58 germline, 37 somatic) and 59 (6.7%) patients with BRCA2-associated OC (40 germline, 19 somatic). Patients with a deleterious genetic alteration were diagnosed with OC at younger age and more likely to have high-grade serous histology compared to the WT group (p < 0.01). High rates of biallelic alterations were observed amongst gPV in BRIP1 (11/13), PALB2 (3/4), RAD51B (3/4), RAD51C (3/4), and RAD51D (8/10), and WES was performed in a subset (n = 27) of tumors from these patients with adequate tumor purity (>30%). We observed a higher tumor mutational burden (TMB), median 2.5 (1.1-6.0) vs. 1.2 (0.6-2.6) mut/Mb, and enrichment of HRD mutational signatures in tumors associated with PALB2 and RAD51B/C/D compared with BRIP1 (p < 0.01), although markers of telomeric-allelic imbalance (TAI), large-scale state transitions (LST) and fraction of genome altered (FGA) were similar. PFS and OS varied by gene group with best survival in BRCA1/2-associated OC, even after adjustment for clinical covariates in multivariable models (p < 0.01). Although we observed heterogeneity in PFS and OS for those with gPV in other HR-related genes by biallelic status and HRD phenotype, none had significantly better survival than those with WT OC. Conclusions: OCs associated with gPV in non- BRCA1/2 HR-related genes represent a heterogenous group. OCs in those with gPV in PALB2 and RAD51B/C/D preferentially harbored biallelic alterations and displayed an HRD phenotype.

Homologous recombination-related (HRR) gene mutations in patients with glioma and their relevance to genomic characteristics, tumor mutation burden (TMB), and prognosis.

e14023 Background: Homologous Recombination Repair (HRR) is one of the core repair methods for DNA double strand damage and the mutations of HRR pathway gene may be the main cause of many cancers. However, there is little research on the potential correlation between the molecular characteristics of HRR pathway genes and glioma. Our study explored HRR gene mutations in glioma patients and its relevance to genomic characteristics, tumor mutation burden (TMB) and prognosis. Methods: Samples from 367 glioma patients with a median age of 46 were detected by 551-gene panel or whole-exome sequencing (WES), and the WES data of 894 glioma patients were extracted from TCGA database ( http://cancergenome.nih.gov ). Among 367 glioma patients, 151 patients occurred HRR somatic mutations. Among them, 47.68% (72/151) patients carried HRR related pathogenic mutation (P/LP), and 52.32% (79/151) patients carried HRR benign/likely benign/variant of uncertain significance mutations (B/LB/VUS). The patients were divided into two groups according to whether patients carried HRR related pathogenic mutation, HRR P/LP group (72) and Non-HRR P/LP group (295). The differences of genomic characteristics, TMB and prognosis between HRR P/LP group and Non-HRR P/LP group were analyzed. Results: In 151 glioma patients harboring HRR somatic mutations, PTEN had the highest mutation frequency (49%; 74/151), followed by CHEK2, DNMT3A, BRCA2 and ATM, with mutation frequency of 11% (17/151), 10% (15/151), 9% (14/151）and 9% (14/151). Patients of HRR P/LP group and HRR B/LB/UVS group showed a significant difference at HRR pathway genes, including PTEN, RAD50, MSH6 and RAD21. In addition, differences of non-HRR pathway genes in HRR P/LP group and Non-HRR P/LP group were found. The mutation frequency of these differential genes was generally high in HRR P/LP group. However, compared to Non-HRR P/LP group, the mutation frequency of IDH1 in HRR P/LP group was significantly higher (Non-HRR P/LP 32% VS HRR P/LP 10%; P＜0.0001). The TMB value in Non-HRR P/LP group was significantly higher than that in HRR P/LP group (P＜0.0001), and the same trend of TMB in two groups was discovered in TCGA cohort (P＜0.0001). Importantly, a significant difference of overall survival (OS) in TCGA database was found between HRR P/LP group and Non-HRR P/LP group (P＜0.0001, HR =2.17, 95%CI: 1.54-3.06), and the median OS were 17.6 and 34.9 months, respectively. Conclusions: This study showed HRR pathway genes status was significantly related to the genomic characteristics, TMB and prognosis of glioma patients. Compared to patients in HRR P/LP group, patients in Non-HRR P/LP group had higher mutation frequency of IDH1, lower TMB value and better prognosis. The relationship between HRR pathway genes and glioma needs to be further explored.

Talazoparib (Tala) in patients (pts) with solid tumors with BRCA1/2 mutation (mut): Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) study.

3115 Background: TAPUR is a phase II basket study evaluating antitumor activity of commercially available targeted agents in pts with advanced cancers with specific genomic alterations. Results in a cohort of pts with solid tumors with BRCA1/2 mut treated with Tala are reported. Methods: Eligible pts had measurable disease, ECOG performance status (PS) 0-2, adequate organ function, and no standard treatment (tx) options. Genomic testing was performed in CLIA-certified, CAP-accredited site selected labs. Pts received 1 mg of Tala orally daily until disease progression. Primary endpoint was disease control (DC) per investigator defined as complete (CR) or partial (PR) response or stable disease (SD) of at least 16+ weeks (wks) duration (SD16+) per RECIST v1.1. The hypothesized null DC rate of 15% was evaluated by a 1-sided exact binomial test (alpha 0.10; 82% power). Secondary endpoints were progression-free survival (PFS), overall survival (OS), duration of response (DOR) and SD, and safety. DOR is defined as time from pt’s first documented objective response (OR) to progressive disease (PD). Duration of SD is defined as time from tx start to PD. Results: 28 pts with 16 solid tumors (6/28 pts had lung cancer) with BRCA1 (n=9) , BRCA2 (n=16) , or BRCA1/2 (n=3) mut were enrolled from Dec 2019 to Sept 2021. All pts were included in efficacy analyses. Demographics and outcomes are shown. 1 CR, 9 PR and 6 SD16+ were observed for a DC rate of 57% (1-sided 90% CI: 43% to 100%) and an OR rate of 36% (95% CI: 19% to 56%); the null hypothesis of a 15% DC rate was rejected (p<0.001). 11/16 pts with OR or SD16+ had a BRCA2 mut, 4 had BRCA1 mut, and 1 had both. The pt with a CR (duration of 93 wks) had non-melanoma skin cancer, with BRCA2 and ATM muts, and was microsatellite instability high with 41 muts per megabase. Pts with PR had various solid tumors; 6/9 pts had BRCA2 mut, 2 had BRCA1 mut , 1 had both. Of pts with DC, 11 had tumor types for which PARP inhibitors are not yet FDA approved. Median duration of PR was 20 wks (range, 11-80). 10/16 pts with DC had a co-alteration in the 24 homologous recombination-related genes examined, mainly ATM (3) or ARID1A (2). 13 pts had ≥1 grade 3 tx-related adverse or serious adverse events including: anemia, AST or bilirubin increase, hyponatremia, nausea, vomiting, neutrophil, platelet, or white blood cell decrease. Conclusions: Tala demonstrated antitumor activity in heavily pretreated pts with advanced solid tumors with BRCA1/2 mut. Additional study is warranted to confirm the efficacy of Tala in non-breast, non-ovarian cancer pts with BRCA1/2 mut. Clinical trial information: NCT02693535 . [Table: see text]

Abstract P4-01-22: Clinical outcomes of metastatic breast cancer patients treated with poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi): the Mayo Clinic experience

Abstract Background: Two poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) are currently FDA-approved for the treatment of HER2-negative metastatic breast cancer (MBC) in carriers of germline pathogenic variants (PVs) in BRCA1 or BRCA2 (BRCA1/2). This study explores the clinical outcomes of MBC patients treated with a PARPi. Methods: In this retrospective study, we included MBC patients treated with a PARPi between January 2017 and February 2022 at Mayo Clinic (Minnesota, Arizona, Florida, and Mayo Clinic Health Systems). We used the Kaplan Meier method to estimate the time-to-treatment-failure (TTF) and the log-rank test to compare different subsets. In addition, predictors of TTF were identified in a multivariate cox-proportional hazard regression model, including age at PARPi initiation, race, ethnicity, histology, estrogen receptor (ER), progesterone receptor (PR), and HER2 expression of the tumor, the number of prior therapies, type of PARPi, and PV carrier status (germline BRCA1/2 or PALB2 vs. somatic BRCA1/2 vs. other). Results: Sixty-five patients treated with PARPi (olaparib: 51; talazoparib: 14) were included in the final analysis. Fifty-five patients were carriers of germline PVs in BRCA1 (n=24, 37%), BRCA2 (n=27, 42%) or PALB2 (n=4, 6%), whereas ten patients (15%) had no germline PVs but the tumor had a somatic mutation in the homologous recombination-related (HRR) genes (7 in BRCA1/2, 2 in ATM, and 1 in CDKN2A and CDH1). At the data cutoff, 48 (74%) patients had discontinued PARPi due to progression or death. Fifteen (23%) patients required a dose reduction due to side effects. Occurrence of grade ≥ 3 side effects: anemia in 8, fatigue in 4, neutropenia in 2, and thrombocytopenia in 2 patients. Eight (15.7%) patients in the olaparib group and seven (50%) patients in the talazoparib group required a dose reduction for side effects. No patient on olaparib required drug discontinuation due to side effects, whereas two patients on talazoparib were switched to olaparib due to cytopenias and could tolerate olaparib. Median TTF in the overall population was 8 months (95% confidence interval [CI]: 6.4 – 9.6), and there was no difference (p=0.64) in TTF between the olaparib and talazoparib groups. Median TTF in the germline BRCA1, BRCA2, and PALB2 PV carriers were 7, 8, and 11 months, respectively (p=0.57). Among patients with somatic BRCA1/2 mutations, the median TTF was 4 months. Numerically, patients with HER2-positive tumors (n=8) had a shorter TTF compared to HER2-negative tumors (Median TTF: 4 vs. 8 months, p=0.098). No significant difference in TTF was observed by ER or PR status of the tumor, age at initiation of PARPi, the number of prior therapies, and prior use of platinum-based chemotherapy or CDK4/6 inhibitors. In multivariate analysis, HER2 positivity (hazard ratio [HR]: 8.0, 95% CI: 2.2 – 29.4, p=0.002), somatic BRCA1/2 mutations (HR: 7.6, 95% CI: 1.2 – 50.0, p=0.03) and somatic mutations in other HRR genes (HR: 19.1, 95% CI: 3.1 – 118.6, p=0.002) were associated with worse TTF. Conclusions: In the real world, PARPi were well-tolerated with promising time-to-treatment-failure (TTF) benefits comparable to data from clinical trials. Notably, relatively shorter TTF was observed in patients with somatic BRCA1/2 and other HRR gene mutations and HER2-positive MBC. These findings improve our understanding of the role of PARPi in MBC and will help to guide treatment decisions with PARPi in the clinical setting. Citation Format: Nusrat Jahan, Jodi Taraba, Karthik V. Giridhar, Roberto A. Leon-Ferre, Amye J. Tevaarwerk, Elizabeth Cathcart-Rake, Ciara C. O’Sullivan, Prema Peethambaram, Timothy J. Hobday, Kathryn Ruddy, Lida A. Mina, Pooja Advani, Felipe Batalini, Matthew P. Goetz, Tufia C. Haddad, Fergus J. Couch, Siddhartha Yadav. Clinical outcomes of metastatic breast cancer patients treated with poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi): the Mayo Clinic experience [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 P4-01-22.

Comprehensive analysis of germline drivers in endometrial cancer.

We sought to determine the prevalence of germline pathogenic variants (gPVs) in unselected patients with endometrial cancer (EC), define biallelic gPVs within tumors, and describe their associations with clinicopathologic features. Germline assessment of at least 76 cancer predisposition genes was performed in patients with EC undergoing clinical tumor-normal Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) sequencing from January 1, 2015, to June 30, 2021. In patients with gPVs, biallelic alterations in ECs were identified through analysis of loss of heterozygosity and somatic PVs. Clinicopathologic variables were compared using nonparametric tests. Of 1625 patients with EC, 216 (13%) had gPVs, and 15 patients had 2 gPVs. There were 231 gPVs in 35 genes (75 [32%] high penetrance; 39 [17%] moderate penetrance; and 117 [51%] low, recessive, or uncertain penetrance). Compared with those without gPVs, patients with gPVs were younger (P = .002), more often White (P = .009), and less obese (P = .025) and had differences in distribution of tumor histology (P = .017) and molecular subtype (P < .001). Among 231 gPVs, 74 (32%) exhibited biallelic inactivation within tumors. For high-penetrance gPVs, 63% (47 of 75) of ECs had biallelic alterations, primarily affecting mismatch repair (MMR) and homologous recombination related genes, including BRCA1,BRCA2, RAD51D, and PALB2. Biallelic inactivation varied across molecular subtypes with highest rates in microsatellite instability-high (MSI-H) or copy-number (CN)-high subtypes (3 of 12 [25%] POLE, 30 of 77 [39%] MSI-H, 27 of 60 [45%] CN-high, 9 of 57 [16%] CN-low; P < .001). Of unselected patients with EC, 13% had gPVs, with 63% of gPVs in high-penetrance genes (MMR and homologous recombination) exhibiting biallelic inactivation, potentially driving cancer development. This supports germline assessment in EC given implications for treatment and cancer prevention.

Role of detection of mutations in the &lt;i&gt;BRСA1,2&lt;/i&gt;, &lt;i&gt;CHEK2&lt;/i&gt;, &lt;i&gt;PALB2&lt;/i&gt; genes in diagnosis of oncological diseases and determination of the therapy strategy

Breast cancer (BC) is the most common malignant neoplasm in women in the Russian Federation. Today, biological markers that characterize the individual characteristics of the tumor, such as the tendency to metastasize, hormonal sensitivity, are of great importance for the diagnosis and treatment of patients with breast cancer. Among the genes associated with hereditary breast cancer, there are genes with high penetrance (BRCA1, BRCA2, MLH1, MSH2, STK11, PTEN, TP53 and APC) and genes with moderate penetrance (CHEK2, ATM and PALB2). All of the listed above genes are responsible for DNA repair by homologous recombination, and they represent a group of HRR genes (homologous recombination-related genes). Mutations in the BRCA1 and BRCA2 genes can also initiate cancer of the ovaries, pancreas, and prostate. Understanding of the molecular and genetic nature of an oncological disease allows applying targeted drugs to therapy of a disease.

Olaparib (O) in patients (pts) with colorectal cancer (CRC) with ATM mutation (mut): Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) study.

122 Background: TAPUR is a phase II basket study evaluating antitumor activity of commercially available targeted agents in pts with advanced cancers with genomic alterations. Results in a cohort of pts with CRC with ATM mut treated with O are reported. Methods: Eligible pts had advanced CRC with ATM mut, no standard treatment (tx) options, measurable disease, ECOG Performance Status (PS) 0-2, and adequate organ function. Genomic testing was done in CLIA-certified, CAP-accredited labs. Recommended dosing for O was 300 mg twice daily (tablets) or 400 mg twice daily (capsules) until disease progression. Primary end point was disease control (DC), defined as complete or partial (PR) response per RECIST v. 1.1, or stable disease (SD) at 16+ weeks (wks) (SD16+). Simon 2-stage design tested the null DC rate of 15% vs. 35% (power = 0.85; α = 0.10). If ≥2 of 10 pts in stage 1 has DC, 18 more pts are enrolled; otherwise, cohort is closed for futility. If ≥7 of 28 pts has DC, the null DC rate is rejected. Secondary end points were progression-free survival (PFS), overall survival (OS), duration of response (DOR), duration of SD, and safety. DOR is defined as time from the pt’s first documented objective response (OR) until progressive disease (PD). Duration of SD is defined as time from start of tx to PD. Results: 30 pts with CRC and ATM mut were enrolled from Sept 2016 to Aug 2019. 3 pts were not included in efficacy outcomes: 2 pts had no post-baseline tumor evaluation; 1 pt was found to be ineligible after receiving 1 dose. 1 PR ( ATM P938fs*11 and RAD50 variant of unknown significance (VUS); DOR was 18.6 wks) and 3 SD16+ ( ATM R1875*, splice site 4237-11_4241del16, E522*; duration of SD was 19.7, 25.3 and 27.0 wks, respectively) were observed for DC rate of 23% (95% CI, 6% to 39%) and OR rate of 4% (95% CI, 0.1% to 19%). The null DC rate was not rejected (p=0.38). 6/30 pts had a BRCA2 co-alteration, but none of these pts achieved OR or SD16+; no pts had a BRCA1 co-alteration; aside from the pt with PR and RAD50 VUS, only 1 other pt who achieved OR or SD16+ had a co-alteration among the other homologous recombination-related genes examined ( ATR VUS). 7 pts had ≥1 Grade 3 adverse or serious adverse event (SAE) at least possibly related to O, including urinary tract infection, white blood cell decreased, febrile neutropenia (SAE), anemia (1 SAE), lung infection (SAE), fatigue (SAE), and nausea (SAE). Conclusions: Monotherapy O does not show sufficient antitumor activity in pts with advanced CRC with ATM mut to warrant further study. Clinical trial information: NCT02693535 . [Table: see text]

Hereditary cancer variants and homologous recombination deficiency in biliary tract cancer

The heritability and actionability of variants in homologous recombination-related genes in biliary tract cancers (BTCs) are uncertain. Although associations between BTC and BRCA germline variants have been reported, homologous recombination deficiency has not been investigated in BTCs. We sequenced germline variants in 27 cancer-predisposing genes in 1,292 BTC cases and 37,583 controls without a personal nor family history of cancer. We compared pathogenic germline variant frequencies between cases and controls and documented the demographic and clinical characteristics of carriers. In addition, whole-genome sequencing of 45 BTC tissues was performed to evaluate homologous recombination deficiency status. Targeted sequencing identified 5,018 germline variants, which were classified into 317 pathogenic, 3,611 variants of uncertain significance, and 1,090 benign variants. Seventy-one BTC cases (5.5%) had at least one pathogenic variant among 27 cancer-predisposing genes. Pathogenic germline variants enriched in BTCs were present in BRCA1, BRCA2, APC, and MSH6 (p<0.00185). PALB2 variants were marginally associated with BTC (p=0.01). APC variants were predominantly found in ampulla of Vater carcinomas. Whole-genome sequencing demonstrated that three BTCs with pathogenic germline variants in BRCA2 and PALB2, accompanied by loss of heterozygosity, displayed homologous recombination deficiency. Conversely, pathogenic germline variants without a second hit or variants of other homologous recombination-related genes such as ATM and BRIP1 showed homologous recombination-proficient phenotypes. In this study, we describe the heritability and actionability of variants in homologous recombination-related genes, which could be used to guide screening and therapeutic strategies for BTCs. We found that 5.5% of biliary tract cancers (BTCs) in a Japanese population possessed hereditary cancer-predisposing gene alterations, including in BRCA and genes associated with colorectal cancer. Two hits in homologous recombination-related genes were required to confer a homologous recombination-deficient phenotype. PARP inhibitors and DNA-damaging regimens may be effective strategies against BTCs exhibiting homologous recombination deficiency. Hence, in this study, genome-wide sequencing has revealed a potential new therapeutic strategy that could be applied to a subset of BTCs.

Alterations in Homologous Recombination-Related Genes and Distinct Platinum Response in Metastatic Triple-Negative Breast Cancers: A Subgroup Analysis of the ProfiLER-01 Trial.

Background: a specific subset of metastatic triple-negative breast cancers (mTNBC) is characterized by homologous recombination deficiency (HRD), leading to enhanced sensitivity to platinum-based chemotherapy. Apart from mutations in BRCA1/2 genes, the evaluation of other HRD-related alterations has been limited to date. As such, we analyzed data from mTNBC patients enrolled in the ProfiLER-01 study to determine the prevalence of alterations in homologous recombination-related (HRR) genes and their association with platinum sensitivity. Methods: next-generation sequencing and promoter methylation of BRCA1 and RAD51C were performed on tumors from patients with mTNBC, using a panel of 19 HRR genes. Tumors were separated into three groups based on their molecular status: mutations in BRCA1/2, mutations in other HRR genes (BRCA1/2 excluded) or BRCA1/RAD51C promoter methylation and the absence of molecular alterations in HRR genes (groups A, B and C, respectively). Sensitivity to platinum-based chemotherapy was evaluated through the radiological response. Results: mutations in BRCA1/2 were detected in seven (13.5%) patients, while alterations in other HRR genes or hypermethylation in BRCA1 or RAD51C were reported in 16 (30.7%) patients; furthermore, no alteration was found in the majority of patients (n = 29; 55.8%). Among 27 patients who received platinum-based chemotherapy, the disease control rate was 80%, 55% and 18% (groups A, B and C, respectively; p = 0.049). Regarding group B, patients with disease control exhibited mutations in FANCL, FANCA and the RAD51D genes or RAD51C methylation; Conclusion: mutations in HRR genes and epimutations in RAD51C were associated with disease control through platinum-based chemotherapy. As such, apart from well-characterized alterations in BRCA1/2, a more comprehensive evaluation of HRD should be considered in order to enlarge the selection of patients with mTNBC that could benefit from platinum-based chemotherapy.