DNA Damage Repair Gene Mutations Research Articles

Genomic Correlates of Prostate-Specific Membrane Antigen Expression and Response to 177Lu-PSMA-617: A Retrospective Multicenter Cohort Study.

While 177Lu-PSMA-617 (LuPSMA) is an effective therapy for many patients with metastatic castration-resistant prostate cancer (mCRPC), biomarkers associated with outcomes are not well defined. We hypothesized that prostate cancer mutational profile may associate with clinical activity of LuPSMA. We devised a study to evaluate associations between mCRPC mutational profile with LuPSMA clinical outcomes. This was a multicenter retrospective analysis of patients with mCRPC with next-generation sequencing (NGS) who received LuPSMA. PSA50 response (ie, ≥50% decline in prostate-specific antigen [PSA]) rate, PSA progression free survival (PSA PFS), and overall survival (OS) were compared between genetically defined subgroups. One hundred twenty-six patients with NGS results who received at least one cycle of LuPSMA were identified. The median age was 73 (IQR, 68-78) years, 124 (98.4%) received ≥1 prior androgen receptor-signaling inhibitor, and 121 (96%) received ≥1 taxane-based chemotherapy regimen. Fifty-eight (46%) patients with a DNA damage repair gene mutation (DNA damage response group) and 59 (46.8%) with a mutation in TP53, RB1, or PTEN tumor suppressor genes (TSG group) were identified. After adjusting for relevant confounders, the presence of ≥1 TSG mutation was associated with shorter PSA PFS (hazard ratio [HR], 1.93 [95% CI, 1.05 to 3.54]; P = .034) and OS (HR, 2.65 [95% CI, 1.15 to 6.11]; P = .023). There was improved OS favoring the DNA damage response group (HR, 0.37 [95% CI, 0.14 to 0.97]; P = .044) on multivariable analysis. Univariate analysis of patients with ATM mutations had significantly higher rates of PSA50 response, PSA PFS, and OS. Outcomes on LuPSMA varied on the basis of mutational profile. Prospective studies to define the clinical activity of LuPSMA in predefined genomic subgroups are justified.

Abstract 5559: The anti-tumor efficacy and immune effects of combining of ceralasertib, an oral ATR kinase inhibitor, with imipridones, in prostate cancer treatment in vitro and in vivo

Abstract Prostate cancer is the most common cancer and the second leading cause of cancer death among men in the United States. There is an estimated 10% to 50% of cases progress to metastatic castration resistant prostate cancer (mCRPC) state within 3 years of diagnosis. mCPRC remains lethal despite therapeutic advances. There is approximately 20% of mCRPC patients present somatic DNA damage repair (DDR) gene mutations. Ceralasertib, formerly known as AZD6738, is a potent and selective orally bioavailable inhibitor of the ataxia tenlangiectasia and Rad3-related (ATR) kinase, which is involved in DNA repair in response to DNA damage and replication stress. Preclinical studies have demonstrated ATRi sensitizing alterations in DNA damage response (DDR) genes. Ceralasertib’s antitumor activity as a monotherapy in treating prostate cancer is moderate. Thus, we combined ceralasertib with imipridones (ONC201 and ONC206), which target mitochondrial caseinolytic protease P (ClpP) and the integrated stress response, resulting in enhanced antitumor efficacy in vitro. Prior data have demonstrated sensitivity of 4 prostate cancer lines to ceralasertib and imipridones monotherapies, synergistic activities with the combination treatments, and immune enhancement effects with the combination treatments when co-cultured with NK92MI cell line. We proceeded to a short term in-vivo study validating the combination treatment efficacy. Preliminary results include cytokine profiling using the Luminex 200 technology to understand treatment induced changes in the tumor microenvironment (TME) from both in vitro and in vivo studies. Our results guide novel clinical trials for effective clinical responses in mCPRC patients. Citation Format: Yutong Linda Xia, Leiqing Zhang, Maryam Ghandali, Maximilian P. Schwermann, Wafik El-Deiry. The anti-tumor efficacy and immune effects of combining of ceralasertib, an oral ATR kinase inhibitor, with imipridones, in prostate cancer treatment in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5559.

CTNI-42. PHASE I CLINICAL TRIAL OF PEPOSERTIB PLUS RADIATION IN NEWLY DIAGNOSED MGMT-UNMETHYLATED GLIOBLASTOMA

Abstract BACKGROUND DNA-dependent protein kinase (DNA-PK) is a pivotal component of DNA damage repair (DDR) pathways and is an attractive target in glioblastoma because its expression renders tumors less vulnerable to radiotherapy. Peposertib is a small molecule DNA-PK inhibitor that has been shown to potentiate radiotherapy and regress glioblastoma tumors pre-clinically. We conducted a two-stage phase I trial of peposertib plus radiation in newly-diagnosed MGMT-unmethylated glioblastoma (NCT04555577). Method: In stage 1, patients received peposertib plus standard-of-care radiotherapy to determine the maximum-tolerated dose (MTD) based on the Bayesian Optimal Interval design (maximum n = 24). Stage 2 is a window-of-opportunity expansion cohort and will include 5 surgical patients to evaluate tumor drug concentration. Both groups receive adjuvant temozolomide for 6-cycles. RESULTS Fifteen completed the 10-week dose-limiting toxicity (DLT) period; 3-50mg, 3-100mg, 3-200mg, 6-300mg. One DLT (G3 radiation necrosis [RN] at 300mg) was observed. Most notable toxicity was 3 patients with transient G3 dermatitis of the scalp (not DLT per protocol) (2-200mg, 1-300mg). Therefore, radiation dose constrains to the skin were incorporated and subsequent patients did not experience this toxicity. Next-generation sequencing (NGS) was available for 13 archival tissue. Two patients had pathology-proven RN (one within and one outside of the DLT period). Both tumors had mutations in DDR genes (i.e. ATRX, DICER1). Recurrent tissue was available for one patient after treatment with peposertib showed gain of two ATM mutations. CONCLUSION The initial safety data of peposertib plus radiation in newly-diagnosed MGMT unmethylated glioblastoma is favorable. The cases with RN in tumors with DDR mutations, the gain of two ATM mutations in a recurrent tumor and the cases of scalp dermatitis suggest that peposertib is active and possibly potentiates the effect of radiation. Safety and survival data and correlations with genomics will be presented. The study was supported by EMD Serono (CrossRef Funder ID: 10.13039/100004755).

DNA damage response and repair gene mutations are associated with tumor mutational burden and outcomes to platinum-based chemotherapy/immunotherapy in advanced NSCLC patients

BackgroundDNA damage response and repair (DDR) genes are crucial for maintaining the integrity of the genome. This study aims to explore the correlation of DDR gene mutations with TMB, clinical characteristics, and outcomes to platinum-based chemotherapy and platinum-based chemotherapy/immunotherapy in non-small cell lung cancer (NSCLC) without EGFR and ALK alterations.MethodsTumor tissue from 49 patients with stage III or IV NSCLC who were without EGFR and ALK alterations were analyzed using targeted next-generation sequencing (NGS). Among them, 13 patients received first-line platinum-based chemotherapy, 32 patients received first-line platinum-based chemotherapy/immunotherapy.ResultsIn these NSCLC patients without EGFR and ALK alterations, the frequently mutated genes included TP53, KMT2D and KRAS, the most frequently mutated DDR gene was FANCG, DDR gene mutations were detected in 20 patients. The mutation frequency of homologous recombination (HR) pathway was significantly higher in lung squamous cell carcinoma (LUSC) than that in lung adenocarcinoma (LUAD) (30.8% vs. 5.7%). Among DDR positive patients, a lower percentage exhibited metastasis. Patients with DDR gene mutations, cell-cycle checkpoint pathway mutations, and BER pathway mutations had significantly higher TMB compared to those without corresponding mutations. In the patients receiving platinum-based chemotherapy/immunotherapy, the disease control rate was significantly lower in the DDR-positive group compared with that in the DDR-negative group (55.6% vs. 100.0%). Among LUAD patients receiving platinum-based chemotherapy/immunotherapy, we observed a worse overall survival (OS) in DDR-positive group, as well as poorer progression-free survival(PFS)and OS in BER-positive and FANCG mutated group.ConclusionsDDR gene mutations are associated with tumor metastasis, TMB, and outcomes to platinum-based chemotherapy/immunotherapy in advanced NSCLC patients.

The correlation between clinical outcomes and genomic analysis with high risk factors for the progression of osteosarcoma.

Osteosarcoma (OS) is a rare but aggressive malignancy. Despite previous reports, molecular characterization of this disease is not well understood, and little is known regarding OS in Chinese patients. Herein, we analyzed the genomic signatures of 73 Chinese OS cases. TP53, NCOR1, LRP1B, ATRX, RB1, and TFE3 were the most frequently mutated gene in our OS cohort. In addition, the genomic analysis of Western OS patients was performed. Notably, there were remarkable disparities in mutational landscape, base substitution pattern, and tumor mutational burden between the Chinese and Western OS cohorts. Specific molecular mechanisms, including DNA damage repair (DDR) gene mutations, copy number variation (CNV) presence, aneuploidy, and intratumoral heterogeneity, were associated with disease progression. Additionally, 30.1% of OS patients carried clinically actionable alterations, which were mainly enriched in PI3K, MAPK, DDR, and RTK signaling pathways. A specific molecular subtype incorporating DDR alterations and CNVs was significantly correlated with distant metastasis-free survival and event-free survival, and this correlation was observed in all subgroups with different characteristics. These findings comprehensively elucidated the genomic profile and revealed novel prognostic factors in OS, which would contribute to understanding this disease and promoting precision medicine of this population.

Application value of DNA damage repair variants in adjuvant therapy of triple negative breast cancer

Objective: To investigate the correlation between adjuvant chemotherapy with platinum-containing regimens and DNA damage repair (DDR) defects in early-stage triple negative breast cancer (TNBC), and to provide a basis for precise treatment of TNBC. Methods: Next-generation sequencing (NGS) testing was performed on postoperative breast cancer specimens selected from the Cancer Hospital of Chinese Academy of Medical Sciences from June 2009 to October 2015 to analyze the correlation between DDR gene variants and the efficacy of adjuvant chemotherapy with TNBC platinum-containing regimens, and thus to screen the superior population for adjuvant chemotherapy with TNBC platinum-containing regimens. The study used t-test, χ(2) test, Fisher's exact test, rank sum test and multifactorial logistic analysis to assess the associations between mutated genes and clinicopathological characteristics and prognosis, and Log-rank test and Cox proportional risk model were used for survival and correlation analysis. Results: NGS results were successfully obtained in 149 patients (74 in the platinum-containing group and 75 in the platinum-free group), with a 97.3% (145/149) DDR gene mutation rate and a median number of 4 mutations in all patients. 5-year disease-free survival (DFS) was 85.4% and 75.0% for patients with DDR gene mutations and DDR gene wild-type, respectively, without statistical difference (P=0.825). The 5-year DFS rates of patients with homologous recombination repair (HRR) pathway mutation were 84.6% in platinum-containing (TCb) group and 84.9% in platinum-free (EC-T) group (P=0.554), respectively. The 5-year DFS rates of patients with and without mutations in the platinite-containing HRR pathway were 84.9% and 85.0%, respectively (P=0.751). The number of DDR pathways with mutations and the number of DDR gene mutations were not associated with prognosis (both P>0.05). PIK3CA mutation patients in TCb group had a worse prognosis than wild-type patients (5-year DFS were 71.4% and 88.1%, P=0.037), and KMT2D mutation patients in EC-T group had a worse prognosis than wild-type patients (5-year DFS were 76.9% and 86.8%, P=0.039). Conclusions: DDR gene variation is common in TNBC, more clinical studies are needed to prove whether DDR variation can serve as effective biomarkers for treatment with platinum.

A Review of the Molecular Landscape of Adenoid Cystic Carcinoma of the Lacrimal Gland.

Adenoid cystic carcinoma (ACC) has a worldwide incidence of three to four cases per million population. Although more cases occur in the minor and major salivary glands, it is the most common lacrimal gland malignancy. ACC has a low-grade, indolent histological appearance, but is relentlessly progressive over time and has a strong proclivity to recur and/or metastasise. Current treatment options are limited to complete surgical excision and adjuvant radiotherapy. Intra-arterial systemic therapy is a recent innovation. Recurrent/metastatic disease is common due to perineural invasion, and it is largely untreatable as it is refractory to conventional chemotherapeutic agents. Given the rarity of this tumour, the molecular mechanisms that govern disease pathogenesis are poorly understood. There is an unmet, critical need to develop effective, personalised targeted therapies for the treatment of ACC in order to reduce morbidity and mortality associated with the disease. This review details the evidence relating to the molecular underpinnings of ACC of the lacrimal gland, including the MYB-NFIB chromosomal translocations, Notch-signalling pathway aberrations, DNA damage repair gene mutations and epigenetic modifications.

Abstract B054: Inherited mutations of DNA damage repair genes in a racially diverse cohort of men with prostate cancer

Abstract Introduction: DNA damage repair genes (DDRGs) play an important role in genomic stability and mutations in DDRGs contribute to clinically significant prostate cancer (PCa). However, the association of germline mutations in DDRGs with PCa progression and therapeutic stratification remain to be defined in African American (AA) men. Our objective was to genomically profile all known DDRGs and provide ancestry specific findings, focusing on PCa patients with African ancestry. Methods: Germline mutations in all DDRGs (N=276) was evaluated by whole genome sequence (WGS) analysis of archived blood DNA samples from 600 PCa patients (300 AA and 300 CA) who underwent primary treatment at Walter Reed National Military Medical Center. The WGS mean coverage exceeded 37x. Principal Component Analysis using the Peddy program was conducted, and ancestry prediction was based on a machine learning approach using 1000G as reference. Variant frequencies in CPDR PCa patients were compared to variant frequencies available from the Exome Aggregation Consortium (ExAC) controls with no PCa. Data analysis approaches included single variant association, gene-based total frequency test and clinico-pathological associations for germline mutations. All statistical tests were two-sided, and FDR adjusted. FDR < 0.05 was set as significance threshold. Results: Comprehensive analysis of 276 DDRGs revealed that germline mutation (Pathogenic/Likely Pathogenic; P/LP) carrier rate was 23.5%, which is three times higher than reported before in both AA and CA men, due to our unbiased WGS approach. We found that only 13 of the 46 DDRGs identified with P/LP mutations were common to AA and CA men, demonstrating clear disparity along ancestry lines. Importantly, RAD family genes (RAD54L, RAD54B, RAD51), which are potentially targetable, as well as PMS2 and BRCA1, were among the most frequently mutated DDRGs in AA, but not in CA men. Germline mutations in RAD51 and PMS2 were enriched in AA cohort as compared to CA men (P 0.01 and 0.03 respectively), while germline mutations in FANCA were significantly enriched in CA cohort (P < 0.01). Pathway analysis showed that the HR pathway (with 15 mutations) was associated with faster disease progression to biochemical recurrence (BCR) (P <0.05), while the NHEJ pathway (with three mutations) was found to be marginally associated with metastasis (p <0.05). Additionally, we found that germline mutations in DDRGs was associated with shorter time to BCR (P <0.05) in AA patients, but not in CA men. Conclusion: Our findings highlight distinct DDRG germline mutation profile across AA and CA prostate cancer men. This may help refine patient stratification for specific targeted therapeutic options especially for under-studied AA men. Future replication studies in an independent patient cohort are warranted to validate our findings. Citation Format: Indu Kohaar, Xijun Zhang, Gregory Chesnut, Clifton Dalgard, Matthew D. Wilkerson, Gyorgy Petrovics. Inherited mutations of DNA damage repair genes in a racially diverse cohort of men with prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B054.

Retrospective evaluation of the value of DNA damage repair gene signature in response to platinum-based chemotherapy in advanced pancreatic ductal adenocarcinoma.

4137 Background: Mutations affecting DNA Damage Repair (DDR) genes have been associated with clinical benefits from platinum-based chemotherapy (PBC) in ovarian and breast cancer. Mutations of DDR genes, including BRCA1/2, PALB2, ATM, ATR, CHK1, or RAD51, are found in around 15% of pancreatic ductal adenocarcinoma (PDAC). Nevertheless, whether advanced PDAC patients harboring DDR gene mutations could benefit more from PBC has not been well established. In this study, we aimed to compare the prevalence of DDR gene mutations between advanced PDAC patients who benefited from PBC and those who did not. Methods: We retrospectively analyzed samples from patients with advanced PDAC who received PBC at our institution from 2008 to 2022. Patients with partial response or progression-free survival (PFS) > 6 months were considered responders, and those with progression disease as the best response were considered non-responders. Tumor molecular profiling was performed on tumor samples by Next Generation Sequencing (NGS) of DNA. Fisher’s exact test was used to compare DDR genomic alterations in responders vs. non-responders. Overall survival (OS) was defined as the time from the start of PBC to the date of death. PFS was defined as the time between the start of PBC and the first date of documented progression or death, whichever occurs first. Survival outcomes were estimated using Kaplan-Meier curves, and differences were tested using the long-rank test. Results: A total of 132 patients with advanced PDAC treated with PBC were included in this study. The median age at diagnosis was 55 years (range 27-79 years), and 71 (53.79%) patients were male. In this cohort, 88 (66.67%) patients were identified as responders. Tumor molecular profiling showed that among responders, 42 patients (47.7%) had genomic alterations in BRCA1/2 or PALB2, and 10 patients (11.3%) had alterations in other DDR genes. In contrast, only 17 patients (38.64%) showed DDR gene alternations among non-responders. Importantly, mutations in DDR genes are significantly associated with the responder group (OR=2.28; 95% CI 1.03-5.17, p=0.04). In line with these findings, patients with DDR gene mutations showed significantly longer PFS (median PFS 9.95 months) compared with patients without DDR gene mutations (median PFS 6.51 months) (HR= 0.57; 95%CI 0.39-0.85; p=0.005). Moreover, significantly longer OS was found in patients with DDR gene mutations (median OS 20.5 months) compared with those without DDR gene mutations (median OS 16.8 months) (HR=0.67; 95%CI 0.45-1; p=0.05). Conclusions: Genomic alterations in DDR genes are significantly associated with the benefit of PBC treatment in advanced PDAC patients. Our results argue in favor of using DDR genes as a decision-making tool for advanced PDAC patient stratification even before the stand-of-care chemotherapies.

PSMA expression and response to 177Lu-PSMA-617 (LuPSMA) in men with vs. without DNA damage repair (DDR) mutations.

5055 Background: LuPSMA, a radioligand targeting the cell surface protein PSMA, is approved for men with PSMA-positive metastatic castration resistant prostate cancer (mCRPC) following an androgen receptor (AR)-signaling inhibitor (ARSI) and docetaxel. DNA damage repair gene (DDR) mutations are common in mCRPC, and given that ionizing radiation induces DNA damage, we hypothesized that the presence of these alterations could associate with improved clinical outcomes to LuPSMA. Data also suggests that the presence of DDR mutations may correlate with PSMA expression, providing further motivation to evaluate if DDR alterations are associated with the clinical activity of LuPSMA. Methods: We abstracted retrospective data from all patients at our center who received at least one cycle of LuPSMA per the FDA label and who had panel-based sequencing performed (e.g. UW-Oncoplex, Foundation One). Patients with somatic or germline alterations in a DDR gene were assigned to the DDR deficient cohort, while patients with somatic testing negative for a DDR gene mutation were assigned to the DDR intact cohort. Mutations in any DDR gene were considered for the purpose of stratifying between genomic subgroups. Differences in baseline PSMA SUVmean and PSA50 responses (i.e. ≥50% decline in PSA) were compared between cohorts. Results: Of 91 patients who received ≥1 cycle of LuPSMA, 54 had genetic testing. 35 (64%) received ≥2 lines of prior ARSI therapy, 30 (56%) received ≥2 lines of prior chemotherapy and 15 (28%) received prior PARP inhibitor. 21 patients had alterations in a DDR gene and the remaining 33 patients had somatic testing without an identifiable DDR mutation. PSMA SUVmean was similar between groups: 8.04 (95% CI: 6.95 - 9.12) (DDR intact) vs. 7.32 (95% CI: 6.23 – 8.41) (DDR deficient), p = 0.37. 7/33 (21%) patients in the DDR intact group achieved PSA50 response compared to 11/21 (52%) in the DDR group (p= 0.018). Survival data is immature but will be presented at the meeting. Rapid autopsy (RA) was performed in one subject with a BRCA2 mutation (baseline PSMA SUVmean 5.6) and immunohistochemistry analysis revealed profound loss of PSMA following progression on LuPSMA. Conclusions: Mutations in DDR genes were associated with a higher PSA50 response rate following LuPSMA compared to patients without a DDR mutation. There was no difference in baseline PSMA expression based on DDR mutational status, suggesting that higher response rates in the DDR cohort may have been mediated primarily by increased sensitivity to ionizing radiation. Evaluation for associations between DDR mutational status and survival endpoints is needed and will require a larger sample size and longer follow up. RA post-LuPSMA revealed loss of PSMA expression, suggesting that antigen loss may be a relevant resistance mechanism. [Table: see text]

The impact of DNA damage repair gene mutations on therapeutic response among Chinese patients diagnosed with advanced biliary tract cancer.

e16190 Background: Biliary tract cancer (BTC) is a fatal disease characterized by molecular heterogeneity, which results in variations in biological behavior. Despite this, the knowledge of pathogenic alterations in the Chinese BTC population using next-generation sequencing (NGS) profiles remains limited. Therefore, we performed a retrospective investigation to assess the predictive significance of DNA damage repair (DDR) mutations in facilitating precision medicine for this disease. Methods: NGS profiling was carried out on resected tissues obtained from Chinese patients diagnosed with advanced BTC. In addition, baseline clinical and genetic characteristics were collected, along with data on their survival outcomes. Results: A total of 68 Chinese patients with BTC who received first-line platinum-containing chemotherapies were enrolled in this study [intrahepatic cholangiocarcinoma (ICC), 33; extrahepatic cholangiocarcinoma (ECC), 13; gallbladder carcinoma (GBC), 22]. Genetic alterations were observed in 67 patients (98.5%), with TP53 (50.0%), KRAS (26.8%), ARID1A (16.2%), and CDKN2A (16.2%) being the most commonly mutated genes. Patients with TP53 mutations demonstrated a trend towards reduced median OS (16.6 vs. 20.1 months, P=0.145). Mutations in DDR genes were identified in 29 (42.6%) of overall patients, primarily involving ATM (11.8%) and BAP1 genes (8.8%), and were significantly associated with longer mPFS (6.4 vs. 4.8 months, P=0.022) and mOS (21.2 vs. 14.3 months, P=0.011) in patients who received first-line platinum-containing chemotherapies. DDR-mutated patients treated with PD-1 blockades showed a tendency towards improved overall survival compared to the DDR-naive group (20.8 vs. 14.3 months, P=0.297). Furthermore, tumor mutational burden (TMB) could be estimated in 63 cases and was significantly higher in those with DDR mutations (P=0.029). Conclusions: Genetic information can aid in identifying a subgroup of BTC patients who may benefit from targeted therapy, this retrospective study demonstrated the predictive significance of DDR mutations for platinum-based chemotherapy efficacy in Chinese patients. Nonetheless, additional research is necessary to explore the potential of DDR mutations in predicting sensitivity to PD-1 blockade.

Randomized phase 2 study of maintenance olaparib vs olaparib plus durvalumab for DNA damage repair (DDR) gene mutated unresectable or metastatic biliary tract cancer (BTC) with durable response to first-line platinum-based chemotherapy: OPTIMUM trial.

TPS4180 Background: BTC is rare and aggressive disease with heterogeneous genetic profiles. Gemcitabine plus cisplatin (GemCis) with or without durvalumab is the standard first-line therapy but further improvement in survival outcomes is needed. In a prior study (Chae HJ et al, Eur J Cancer 2019), germline or somatic mutations in DDR genes including BRCA are detected more than half of BTC patients and associated with better survival outcomes with platinum-based chemotherapy. As the potential efficacy of Olaparib in DDR-mutated cancers and synergism between PARP inhibitors and immune checkpoint inhibitors, we designed randomized phase 2 trial investigating the efficacy and safety of olaparib monotherapy vs olaparib plus durvalumab in BTC patients as maintenance therapy for BTC patients who showed durable response to first-line platinum-based chemotherapy. Methods: This is a randomized, open-label phase 2 study conducted in a single center (Asan Medical Center, Seoul, Korea). Key eligibility criteria include histologically documented locally advanced unresectable or metastatic BTC, no progression at least 16 weeks with first-line platinum-based chemotherapy, DDR mutations on targeted sequencing of tumor tissues and ctDNA, ECOG performance status 0–1, and adequate organ function. Eligible patients will be randomized 1:1 into olaparib monotherapy arm (300 mg twice daily, every 4 weeks) or olaparib plus durvalumab (1,500 mg intravenous, every 4 weeks) arm. Study treatment is continued until disease progression, unacceptable toxicity, withdrawal of consent, or death. Response evaluation is performed every 8 weeks (fixed). Stratification factors are tumor location (intrahepatic vs extrahepatic/gallbladder) and best response to platinum-based chemotherapy (CR/PR vs SD). The six-month progression-free survival rates are the primary endpoint and overall survival, progression-free survival, response rates, and safety profiles are secondary endpoints. A total of 62 patients (31 for each arm) are planned, and 23 (37%) patients (ATM [n=6], BRCA2 [n=7], CHEK2 [n=2], BRCA1 [n=1], RAD51C [n=1], and PBRM1 [n=1]) are enrolled as of Jan 2023. Clinical trial information: NCT05222971 .

Relations between mutant KRAS and TP53 subtypes and other co-mutations in pancreatic cancer.

e16294 Background: The most common mutations in pancreatic cancer are found in the KRAS, TP53, CDKN2A, or SMAD4 genes. Mutations in genes involved in the DNA damage repair (DDR) pathway are also frequently seen. Despite extensive research on the patho-genomic features of pancreatic cancer, the clinical significance of these recurring mutations remains poorly understood. Methods: We identified patients with pancreatic cancer treated at Yale Cancer Center between 2016 and 2021 who underwent Oncomine tumor profiling. The incidence and subtypes of KRAS and TP53, and their association with other genomic alterations and clinicopathological variables were measured. We compared the overall survival (OS) after the diagnosis of recurrent or metastatic disease using the Kaplan-Meier method and long-rank tests. Results: One hundred fifty-nine patients were identified and KRAS mutations were seen in 144 (90.6%) patients, including 64 G12D (44.4%), 48 G12V (33.3%), 19 G12R (13.2%), 6 Q61H (4.2%), and 7 others (4.9%). TP53 mutations were identified in 117 (73.6%) patients, including 80 loss-of-function (LOF) (68.4%), 24 gain-of-function (GOF) (20.5%), and 13 variants of unclear significance (VUS) (11.1%). TP53 LOF mutations were more common in tumors with KRAS WT (40.0%), G12D (56.3%), and G12V (56.3%), than in G12R (31.6%) and others KRAS mutation (30.1%). Conversely, TP53 GOF mutations were more common in tumors with G12R (26.3%) and other KRAS mutations (23.1%), than in KRAS WT (6.7%), G12D (14.1%), and G12V (12.5%). There was no difference in OS between KRAS subtypes (p=0.48) or TP53 subtypes (p=0.52). Patients with TP53 WT had a numerically longer but not statistically significant survival (median 1.65 years versus 1.16 years in patients with TP53 mutations, p=0.20). When each KRAS subtype was examined, patients with tumors with G12V but no TP53 mutation had longer OS (median 2.42 years) than those with WT KRAS or non-G12V mutation (median 1.38 years, p=0.02). Mutations in DDR genes were more frequently seen in the KRAS WT (33.3%) and G12D groups (15.6%), compared to that in the G12V (10.4%), G12R (10.5%) groups. Unique co-mutations were observed in certain KRAS subtypes but not others. Conclusions: In this retrospective study of comprehensive genomic and clinical data of pancreatic cancers, we found that KRAS or TP53 mutation subtypes had no significant impact on OS. Different KRAS subtypes have unique co-occurring genomic alterations, which may be clinically relevant as novel KRAS inhibitors continue clinical development.[Table: see text]

Roles of the PARP Inhibitor in BRCA1 and BRCA2 Pathogenic Mutated Metastatic Prostate Cancer: Direct Functions and Modification of the Tumor Microenvironment.

Cancer cells frequently exhibit defects in DNA damage repair (DDR), leading to genomic instability. Mutations in DDR genes or epigenetic alterations leading to the downregulation of DDR genes can result in increased dependency on other DDR pathways. Therefore, DDR pathways could be a treatment target for various cancers. In fact, polyadenosine diphosphatase ribose polymerase (PARP) inhibitors, such as olaparib (Lynparza®), have shown remarkable therapeutic efficacy against BRCA1/2-mutant cancers through synthetic lethality. Recent genomic analytical advancements have revealed that BRCA1/BRCA2 pathogenic variants are the most frequent mutations among DDR genes in prostate cancer. Currently, the PROfound randomized controlled trial is investigating the efficacy of a PARP inhibitor, olaparib (Lynparza®), in patients with metastatic castration-resistant prostate cancer (mCRPC). The efficacy of the drug is promising, especially in patients with BRCA1/BRCA2 pathogenic variants, even if they are in the advanced stage of the disease. However, olaparib (Lynparza®) is not effective in all BRCA1/2 mutant prostate cancer patients and inactivation of DDR genes elicits genomic instability, leading to alterations in multiple genes, which eventually leads to drug resistance. In this review, we summarize PARP inhibitors' basic and clinical mechanisms of action against prostate cancer cells and discuss their effects on the tumor microenvironment.

Analysis of Plasma Circulating Tumor DNA in Borderline Resectable Pancreatic Cancer Treated with Neoadjuvant Modified FOLFIRINOX: Clinical Relevance of DNA Damage Repair Gene Alteration Detection.

There are no reliable biomarkers to guide treatment for patients with borderline resectable pancreatic cancer (BRPC) in the neoadjuvant setting. We used plasma circulating tumor DNA (ctDNA) sequencing to search biomarkers for patients with BRPC receiving neoadjuvant mFOLFIRINOX in our phase 2 clinical trial (NCT02749136). Among the 44 patients enrolled in the trial, patients with plasma ctDNA sequencing at baseline or post-operation were included in this analysis. Plasma cell-free DNA isolation and sequencing were performed using the Guardant 360 assay. Detection of genomic alterations, including DNA damage repair (DDR) genes, were examined for correlations with survival. Among the 44 patients, 28 patients had ctDNA sequencing data qualified for the analysis and were included in this study. Among the 25 patients with baseline plasma ctDNA data, 10 patients (40%) had alterations of DDR genes detected at baseline, inclu-ding ATM, BRCA1, BRCA2 and MLH1, and showed significantly better progression-free survival than those without such DDR gene alterations detected (median, 26.6 vs. 13.5 months; log-rank p=0.004). Patients with somatic KRAS mutations detected at baseline (n=6) had significantly worse overall survival (median, 8.5 months vs. not applicable; log-rank p=0.003) than those without. Among 13 patients with post-operative plasma ctDNA data, eight patients (61.5%) had detectable somatic alterations. Detection of DDR gene mutations from plasma ctDNA at baseline was associated with better survival outcomes of pati-ents with borderline resectable pancreatic ductal adenocarcinoma treated with neoadjuvant mFOLFIRINOX and may be a prognostic biomarker.

Dual Biomarker Combining DNA Damage Repair Gene Mutations and PD-L1 Expression for Immune Checkpoint Inhibitors in Non-small Cell Lung Cancer.

Immune checkpoint inhibitors (ICIs) improve long-term survival in advanced non-small cell lung cancer (NSCLC) and require robust predictive biomarkers for the selection of responders. This study investigated the optimal implementation of DNA damage repair (DDR) gene mutations to predict response to ICIs in real-world NSCLC patients. We retrospectively reviewed 55 advanced NSCLC patients who had undergone targeted high-throughput sequencing and received ICIs. Patients with two or more DDR gene mutations were defined as DDR2 positive. The patients' median age was 68 (range=44-82) years, and 48 (87.3%) were men. Seventeen patients (30.9%) showed ≥50% high programmed death-ligand 1 (PD-L1) expression. Ten patients (18.2%) received an ICI-chemotherapy combination as first-line therapy, and 38 (69.1%) received ICI monotherapy as more than second-line therapy. Fourteen patients (25.5%) were DDR2-positive. The objective response rate of patients with DDR2-positive or PD-L1 ≥50% was 45.5%, and that of patients with DDR2-negative and PD-L1 <50% was 11.1% (p=0.007). In the PD-L1 low expression subgroup (<50%), patients with DDR2-positive had improved progression-free survival (PFS) and overall survival (OS) after ICIs compared to those with DDR2-negative (PFS: 5.8 vs. 1.9 months, p=0.026, OS: 14.4 vs. 7.2 months, p=0.078). DDR2-positive patients or those with PD-L1 ≥50% (24, 43.6%) had statistically significant improvement in PFS and OS after ICIs compared to DDR2-negative and those with PD-L1 <50% (PFS: 4.4 vs. 1.9 months, p=0.006, OS: 11.6 vs. 7.2 months, p=0.037). A dual biomarker combining DDR gene mutations and PD-L1 expression improves the prediction of response to ICIs in advanced NSCLC.

Differences in DNA damage repair gene mutations between left- and right-sided colorectal cancer.

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide. Studies have shown that the DNA damage response (DDR) mutation is strongly associated with microsatellite instability (MSI) status and is an indication for patients with CRCs receiving immune checkpoint inhibitor (ICI) treatment. However, DDR mutation in microsatellite stable (MSS) CRC remains unclear. In this study, Fisher's exact test, Student'st-test, Wilcoxon rank-sum test and Cox proportional hazards regression model were performed, and a p value of<0.05 was considered statistically significant. The most common gene alterations were APC (77%), TP53 (73%), KRAS (48%), and PIK3CA (25%). The mutationfrequency of APC and TP53 in left-sided CRC was significantly higher than that for right-sided CRC, while the mutation frequency of PIK3CA, ACVR2A, FAT4, and RNF43 in right-sided CRC was significantly higher than that for left-sided CRC. DDR mutations occurred in100% of MSI CRCs and in 83.77% of MSS CRCs, with the most frequently mutated DDR genes being ARID1A (7.5%), ATM (5.7%,) and BRCA2 (2.6%). When right- and left-sided CRCs were compared, no significant difference was observed for DDR genes and pathways. A survival analysis indicated that the DDR mutation was not associated with overall survival (OS) in MSS CRCs, while left-sided patients with homologous recombination repair (HRR) pathway mutations had a significantly prolonged OS compared with right-sided CRCs. Here, we found that stage and grade were statistically significant independent prognostic factors in the left-sided CRC and the right-sided CRC, recommending treatment for these patients stratified by stage. For the future, utilizing DDR gene defects for expanding treatment options and improving prognosis is an issue worth exploring.

Use of PARP inhibitors in prostate cancer: from specific to broader application.

Prostate cancer (PC) is one of the major health issues of elderly men in the word. It is showed that there were approximately 1.414 million patients with PC in 2020 worldwide, with a high mortality rate in metastatic cases. In the present choices of treatment in PC, androgen deprivation therapy has long been as a backbone of them. But the clinical outcomes of patients with metastatic castration-resistant prostate cancer (mCRPC) were not ideal because of their poor prognosis, more effective therapeutic approaches are still necessary to further improve this problem. Poly (ADP-ribose) polymerase (PARP) inhibitors lead to the single-strand DNA breaks and/or double-strand DNA breaks, and result in synthetic lethality in cancer cells with impaired homologous recombination genes. It is estimated that approximately 20~25% of patients with mCRPC have a somatic or germinal DNA damage repair gene mutation. Furthermore, in "BRCAness" cases, which has been used to describe as tumors that have not arisen from a germline BRCA1 or BRCA2 mutation, there were also a number of studies sought to extend these promising results of PARP inhibitors. It is worth noting that an interaction between androgen receptor signaling and synthetic lethality with PARP inhibitors has been proposed. In this review, we discussed the mechanism of action and clinical research of PARP inhibitors, which may benefit population from "specific" to the "all-comer" in patients with PC when combined with novel hormonal therapies.

Abstract LB339: PARP inhibition reprograms CD8 T cells, enhancing their function and generation of prolonged memory, leading to greater anti-tumor immune response

Abstract Olaparib is the most widely studied third-generation PARP inhibitor (PARPi) in clinical practice with a significant clinical outcome in BRCA deficient tumors such as breast and ovarian cancers. However, innate and adaptive resistance in patients with DNA damage repair (DDR) gene mutations were reported after treatment with PARPi, highlighting the potential implication of other compartments such as the role of immune cells in the mechanism of resistance. Importantly, PARPi is shown to have an immune-modulatory capacity within the tumor microenvironment (TME) by activating the STING pathway and increasing interferon gamma (INF-gamma) and chemokine secretion and hence increasing the recruitment and function of CD8 T cells. In addition, PARPi is shown to affect other cells within the TME such as, macrophages, myeloid-derived suppressor cells (MDSCs) and cancer associated fibroblasts (CAFs), promoting either an immune enhancement or immune suppressor milieu that could indirectly affect CD8 T cell function. However, little is known about the direct effect of PARPi on CD8 T cells. In this study using two cold tumor models, we show that PARPi controls the tumor growth and increases survival in tumor-bearing mice. This effect is due to the enhancement of number and cytotoxicity of antigen-specific CD8 T cells and the maintenance of memory population within the TME. In vitro study shows that PARPi activates the SIRT-1/FOXO1 pathway, leading to the modification of gene expression related to memory and fatty acid oxidation (FAO) metabolism in CD8 T cells. As a result, a unique subpopulation of superior central memory cells with high recall responses and anti-tumor effects are generated after PARPi treatment. Interestingly this unique subpopulation was also generated after PARPi in human cells. Together, our findings highlight the direct effect of PARP inhibition on CD8 T cells and its ability to modulate and reprogram CD8 T cells within the TME, leading to a greater anti-tumor immune response. Citation Format: Wael Traboulsi, Subhadip Kundu, Pankaj Gaur, Zainab Ramlaoui, Dareen Sarhan, Nour Shobaki, Jacob Lee, Nazli Jafarzadeh, Simon T. Barry, Viia E. Valge-Archer, Vivek Verma, Seema Gupta, Samir N. Khleif. PARP inhibition reprograms CD8 T cells, enhancing their function and generation of prolonged memory, leading to greater anti-tumor immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB339.

Abstract P5-12-06: Comprehensive analysis of DNA damage repair gene germline mutations in Chinese breast cancer patients

Abstract Background: Germline DNA damage repair (DDR) mutations has been associated with increased cancer risk, PARP inhibitor therapeutic opportunity for breast cancer (BC) patients. However, the profile of germline mutations in BC covering comprehensive DDR genes remains unclear. Methods: A total of 341 women with breast cancer who tested 102 germline related genes (including 50 DDR genes) between April 2021 to May 2022 in Guangdong Provincial People’s Hospital were identified. Variants were classified into pathogenic, likely pathogenic, variant of uncertain significance (VUS), likely benign and benign groups according to the ACMG/AMP Standards and Guidelines. We defined pathogenic and likely pathogenic variants as deleterious mutations. Results: The median age of 341 breast cancer patients was 48 (range, 20-89) at the first diagnosis of BC. A total of 47 patients (13.78%) carried 53 deleterious germline variants in 21 cancer predisposition genes, 16 of which were DDR genes. DDR deleterious mutations were detected in genes including BRCA2 (n=18), BRCA1(n=7), FANCA (n=4), PMS2 (n=4), PALB2(n=2), RECQL4(n=2), PALB2 (n=2), etc. The younger age at diagnosis (less than 40-year-old) were significantly associated with deleterious mutations in DDR pathway(P=0.02). At least one VUS was identified in 238 (69.79%) patients. The top 5 DDR VUS genes were FANCM (n=21), ATM (n=20), RAD54L (n=17), FANCD2 (n=15) and ATR (n=14). Breast or ovarian cancer family history were significantly correlated with VUS germline mutations in DDR pathway(P=0.039). Interesting, we found that patients with pCR efficacy of neoadjuvant therapy were more likely to have VUS mutations in DDR pathway (table 1). Conclusion: We provided a comprehensive view of germline DDR gene mutations in BC patients and also analyzed the association between clinical characteristics and germline DDR mutation status. DDR mutations are prevalent in Chinese BC patients. Patients with younger and breast or ovarian cancer family history were more likely to carry DDR alterations. Moreover, patients with higher frequency of DDR VUS mutations may benefit from neoadjuvant therapy. Table 1. Clinicopathological characteristics between germline mutation carriers and non-carriers Citation Format: Ning Liao, Li Cao, Guochun Zhang, Junyun Wang, Airong Yang, Yulei Wang, Kai Li, Lingzhu Wen, Chongyang Ren, Minghan Jia, Cheukfai Li, Hsiaopei Mok, Bo Chen, Jianguo Lai, Weikai Xiao. Comprehensive analysis of DNA damage repair gene germline mutations in Chinese breast cancer patients [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 P5-12-06.