Germline DNA Damage Research Articles

RDC complex executes a dynamic piRNA program during Drosophila spermatogenesis to safeguard male fertility.

piRNAs are small non-coding RNAs that guide the silencing of transposons and other targets in animal gonads. In Drosophila female germline, many piRNA source loci dubbed "piRNA clusters" lack hallmarks of active genes and exploit an alternative path for transcription, which relies on the Rhino-Deadlock-Cutoff (RDC) complex. RDC was thought to be absent in testis, so it remains to date unknown how piRNA cluster transcription is regulated in the male germline. We found that components of RDC complex are expressed in male germ cells during early spermatogenesis, from germline stem cells (GSCs) to early spermatocytes. RDC is essential for expression of dual-strand piRNA clusters and transposon silencing in testis; however, it is dispensable for expression of Y-linked Suppressor of Stellate piRNAs and therefore Stellate silencing. Despite intact Stellate repression, males lacking RDC exhibited compromised fertility accompanied by germline DNA damage and GSC loss. Thus, piRNA-guided repression is essential for normal spermatogenesis beyond Stellate silencing. While RDC associates with multiple piRNA clusters in GSCs and early spermatogonia, its localization changes in later stages as RDC concentrates on a single X-linked locus, AT-chX. Dynamic RDC localization is paralleled by changes in piRNA cluster expression, indicating that RDC executes a fluid piRNA program during different stages of spermatogenesis. These results disprove the common belief that RDC is dispensable for piRNA biogenesis in testis and uncover the unexpected, sexually dimorphic and dynamic behavior of a core piRNA pathway machinery.

Germline DNA damage repair gene mutations in pancreatic cancer patients with personal/family histories of pancreas/breast/ovarian/prostate cancer in a Japanese population.

AimCancer patients with personal/family histories of pancreatic/breast/ovarian/prostate cancer are associated with a higher likelihood of harboring DNA damage repair (DDR)‐related germline mutations. Here, we aimed to obtain a better understanding of DDR‐related germline mutations in Japanese pancreatic ductal adenocarcinoma (PDAC) patients with personal and/or family histories of BRCA‐related cancers of the pancreas, breast, ovary, and prostate.MethodsWe performed next‐generation sequencing (NGS) and evaluated germline mutations in nine DDR‐related genes (BRCA1, BRCA2, ATM, PALB2, CHEK2, MLH1, MSH2, MSH6, and PMS2) in PDAC patients with personal and/or family histories.ResultsOf 196 patients with PDAC, 39 (19.9%) fulfilled the criteria for at least one family history of pancreatic/breast/ovarian/prostate cancer in first‐degree relatives (sibling–sibling or parent‐child) or the personal history of these malignancies. Targeted NGS revealed that four (10.2%) of 39 patients with personal/family histories harbored deleterious germline mutations—two in BRCA2, one in ATM, and one in MLH1. Both the BRCA2 variants showed frameshift mutations due to short insertion/deletions. In the 39 patients undergoing NGS, a similar distribution of the clinicopathological characteristics was observed between those with deleterious mutations/variants of unknown significance (VUSs) and with benign/wild types. Patients with deleterious germline mutations/VUSs in DDR‐related genes showed a significantly more favorable prognosis than those with benign mutations/wild‐type genes (hazard ratio: 0.160, P = .040).ConclusionsA significant fraction of PDAC patients with personal/family histories of BRCA‐related cancers harbored deleterious germline mutations in DDR‐related genes. DDR‐related germline gene mutations might be a favorable prognostic factor in patients with pancreatic cancer.

Association between germline DNA damage repair-related genes mutation and tumor mutational burden in lung cancer patients.

e21163 Background: Deleterious somatic DNA damage repair (DDR) gene mutations are frequent in non-small cell lung cancer (NSCLC) and are associated with improved clinical outcomes of immunotherapy. DDR gene mutations are associated with higher tumor mutational burden (TMB) in cancer. However, the effect of germline DDR-related genes mutation with different functional annotations on TMB in NSCLC patients is still unclear. Methods: 1671 Chinese patients with NSCLC were enrolled in this study. Genomic profiling was performed on formalin-fixed paraffin-embedded tumor samples or peripheral blood by next generation sequencing (NGS) with 733 cancer-related genes panel. The germline mutation data were obtained. All annotations in clinical significance were according to the 2015 American College of Medical Genetics and Genomics-Association for Molecular Pathology (ACMG-AMP) guidelines. Results: 1076 patients (64.39%) had germline DDR-related gene mutations and 595 (35.61%) had no germline DDR-related gene mutations. Among patients with DDR-related gene mutations, 78 (7.25%) patients had the pathogenic (P) mutations or likely pathogenic (LP) mutations and 1056 (98.14%) had variants of unknown significance (VOUS) mutations. In total, the median TMB was 3.91 mutations/MB (range, 0-68.16) and 4.47 mutations/MB (range, 0-51.40) in patients with P, LP or VOUS mutations and no germline DDR-related gene mutations, respectively. To the further analysis, we divided patients with germline DDR-related gene mutations into three groups: only P or LP mutations (Group 1), only VOUS mutations (Group 2) and concurrence with P/LP/VOUS mutations (Group 3). Compare to the DDR-negative group, TMB was significantly lower in Group 2 (P < 0.001). No significant differences in Group 1 and Group 3 were observed. In addition, we found that mutations in different DDR pathway could not affect TMB value significantly. Conclusions: Germline DNA damage repair-related genes mutation may be not associated with TMB.

Impact of Pathogenic Germline DNA Damage Repair alterations on Response to Intense Neoadjuvant Androgen Deprivation Therapy in High-risk Localized Prostate Cancer

BackgroundIntense neoadjuvant androgen deprivation therapy (ADT) before radical prostatectomy (RP) is an investigational approach to reduce recurrence rates in men with high-risk localized prostate cancer (PCa). The impact of germline DNA damage repair (gDDR) gene alterations on response to intense neoadjuvant ADT is not known. ObjectiveTo evaluate the prevalence of gDDR alterations among men with localized PCa at high risk of recurrence and evaluate their impact on response to intense neoadjuvant ADT. Design, setting, and participantsWe performed germline panel sequencing for 201 men with intermediate- and high-risk localized PCa from five randomized multicenter clinical trials of intense neoadjuvant ADT before RP. InterventionIntense neoadjuvant ADT followed by RP. Outcome measurements and statistical analysisThe prevalence of pathogenic gDDR alterations and their association with exceptional pathologic response (complete response or minimal residual disease, defined as residual tumor with the largest cross-section dimension ≤5 mm) to intense neoadjuvant ADT and rates of post-RP biochemical recurrence. Results and limitationsPathogenic gDDR alterations were detected in 19 (9.5%) of the 201 PCa patients. The most frequently altered genes were BRCA2 (n = 6; 3.0%) and ATM (n = 4; 2.0%). Patients with gDDR alterations exhibited similar rates of exceptional pathologic response (26% vs 22%), pT3 disease (42% vs 53%), lymph node involvement (5.3% vs 10%), extraprostatic extension (35% vs 54%), and positive margins (5.3% vs 13%) to patients without gDDR alterations (all p > 0.05). The 3-yr biochemical recurrence–free survival was also similar at 45% (95% confidence interval 7.9–78%) for men with gDDR alterations and 55% (95% confidence interval 44–64%) for men without gDDR alterations. ConclusionsgDDR alterations are common among men with intermediate- and high-risk localized PCa. Men with gDDR alterations appear to have a comparable response to intense neoadjuvant ADT to that among men without gDDR alterations and should not be excluded from consideration for this treatment approach. Patient summaryIntense therapy to inhibit the production of androgen hormones (eg, testosterone) before surgery may minimize the risk of cancer recurrence for men with high-risk localized prostate cancer. Inherited mutations in certain DNA repair genes are associated with particularly high rates of recurrence. We found that men with these mutations respond equally well to this intense androgen inhibition before surgery as men without the mutations.

The contribution of germline DNA damage response mutations on prostate cancer risk and prognosis: A UK Biobank whole-exome analysis.

67 Background: Germline mutations in DNA Damage Response (DDR) genes such as BRCA2 and ATM have been associated with prostate cancer risk and aggressiveness. These associations are largely based on studies that ascertain for cancer diagnosis and family history and provide risk estimates with limited population-level accuracy. Here we evaluate the clinical significance of germline pathogenic variants in 20 DDR genes and a high-risk susceptibility coding variant in HOXB13 using whole exome sequences from (1) the UK Biobank (UKBB), a population-based cohort (300,000 participants) and (2) patients recruited in AZ clinical trials. Methods: Whole exomes from 6,987 prostate cancer patients (5,921 UKBB and 1,066 AZ) and 88,499 cancer-free males were analysed. Known and novel pathogenic variants were identified and associations with disease risk, age of onset, family history, response to hormonal therapy and overall survival were estimated (multiplicity corrected P value < 0.005). Results: HOXB13 G48E (1.36%), ATM (1.03%) and BRCA2 (0.99%) were the largest contributors to prostate cancer risk, each conferring an increase of ~4-fold, followed by CHEK2 with a moderate contribution (0.46%). No significant contributions to prostate cancer risk were observed for any of the other genes analysed. Family history of prostate cancer was not significantly enriched in any of the gene subpopulations of prostate cancer carriers and compared with non-carriers, there was no significant difference in the median age of disease onset. Analysis of clinical outcomes showed that BRCA2 carriers had a 4-fold increased risk of death (Cox PH HR p = 4.11E-12) and poorer overall survival (Log-Rank p = 4.60E-14), with 88% dying from prostate cancer compared to 49% of non- BRCA2 carriers (UKBB analysis). BRCA2 pathogenic mutations were also associated with early failure to hormonal therapy (Cox PH HR 2.38; p = 9.48E-04; AZ cohort analysis). HOXB13, ATM and CHEK2 mutations were not significantly associated with clinical outcomes. Conclusions: This is the largest study to date providing population-based estimates of prostate cancer risk and prognosis, highlighting BRCA2 carriers as a population in clinical need of early identification and targeted intervention. Updated analyses with data from the full 450,000 UKBB participants (9,000 prostate cancers) will be presented.

Pancreatic ductal adenocarcinoma in the era of precision medicine

The paradigm for treatment of PDAC is shifting from a “one size fits all” of cytotoxic therapy to a precision medicine approach based on specific predictive biomarkers for a subset of patients. As the genomic landscape of pancreatic carcinogenesis has become increasingly defined, several oncogenic alterations have emerged as actionable targets and their use has been validated in novel approaches such as targeting mutated germline DNA damage response genes (BRCA) and mismatch deficiency (dMMR/MSI-H) or blockade of rare somatic oncogenic fusions. Chemotherapy selection based on transcriptomic subtypes and developing stroma- and immune-modulating strategies have yielded encouraging results and may open therapeutic refinement to a broader PDAC population. Notwithstanding, a series of negative late-stage trials over the last year continue to underscore the inherent challenges in the treatment of PDAC. Multifactorial therapy resistance warrants further exploration in PDAC “omics” and tumor-stroma-immune cells crosstalk. Herein, we discuss precision medicine approaches applied to the treatment of PDAC, its current state and future perspective.

Prevalence of comprehensive DNA damage repair gene germline mutations in Chinese prostate cancer patients.

Germline DNA damage repair (DDR) deficiency has been associated with increased cancer risk, poor prognosis and therapeutic opportunity for prostate cancer (PCa) patients. However, the landscape of germline mutations in PCa covering comprehensive DDR genes has not been reported. We performed whole-exome sequencing in 246 patients who meet the National Cancer Center Network guidelines for genetic testing and analyzed variants in 276 DDR genes, which was from the Cancer Genome Atlas. A total of 79 deleterious germline alterations in 60 DDR genes were identified in 31% (76/246) patients. Mutations were found in nine DDR pathways, including 11.8% men in homologous recombination repair (HR) pathways, 2.4% men in mismatch repair (MMR) pathway and 16.7% (41/246) patients in non-HR/MMR pathways. In HRR and MMR pathways, mutations were mostly identified in BRCA2 (5.3%), HFM1 (0.8%), ZSWIM7 (0.8%), MSH2 (0.8%) and MSH3 (0.8%). When compared with the cancer-free cohort, POLN and POLG conferred high risk to PCa with odds ratio 6.9 and 20.5, respectively. We provided a comprehensive view of germline DDR gene mutations in PCa patients. We also identified two potential PCa predisposition genes: POLN and POLG, which have not been reported in the Western population, confirming the necessity of customizing a multigene panel for Chinese PCa patients.

Association of Germline Variants in Human DNA Damage Repair Genes and Response to Adjuvant Chemotherapy in Resected Pancreatic Ductal Adenocarcinoma

The frequency and significance of the germline variants in DNA damage repair genes still need to be elucidated in patients with sporadic pancreatic ductal adenocarcinoma (PDAC). Our purpose was to determine whether germline variants in DNA damage repair genes were associated with survival of patients with sporadic PDAC. We retrospectively identified 854 patients with sporadic PDAC with germline DNA sequenced in targeted 22 DNA damage repair genes by next-generation sequencing. Outcomes were compared in terms of clinicopathologic features, disease-free survival (DFS), and overall survival (OS). Nineteen patients had deleterious mutations; 103 had variant(s) of unknown significance (VUS). Germline DNA damage repair deleterious variant carriers had superior DFS (median, 19.1 months vs 11.9 months, p= 0.012) and OS (median, 29.7 months vs 20.2 months, p=0.034), as compared with wild-type patients. Germline DNA damage repair VUS variant carriers also had superior DFS when compared with wild-type patients. In subgroup analysis, this improved survival was limited to patients receiving adjuvant chemotherapy, deleterious variant carriers vs wild-type patients DFS (median 36.3 months vs 13.1 months, p= 0.006) and OS (median 43.7 months vs 24.3 months, p= 0.045), VUS variant carriers vs wild-type patients DFS (16.5 months vs 13.1 months, p= 0.007). Having a deleterious variant in a DNA damage repair gene is associated with improved survival after resection and adjuvant chemotherapy for pancreatic ductal adenocarcinoma.

PT343 - Germline DNA damage repair gene mutation landscape and clinical relevance in early-onset upper tract urothelial carcinoma patients

PT343 - Germline DNA damage repair gene mutation landscape and clinical relevance in early-onset upper tract urothelial carcinoma patients

Germline and somatic DNA damage repair gene mutations potentially predict the efficacy of relevant treatment in Chinese patients with pancreatic ductal adenocarcinoma.

e16732 Background: PDAC is a fatal disease with molecular heterogeneity, inducing differences in biological behaviour and therapeutic strategy. We conducted a study to reveal the mutation landscape of Chinese PDAC patients, and investigate the predictive role of germline and somatic DNA damage repair (DDR) status in precise treatment. Methods: 195 PDAC patients were enrolled from multiple medical centers of China between Jan 2016 to Nov 2019. Baseline clinical or genetic characteristics, and survival status were collected. NGS were performed on paraffin-embedded resected tissues or peripheral blood using a panel of 417 genes, including 50 DDR-related genes. Survival analysis was conducted using Kaplan-Meier, and Cox proportional hazard regression model. Results: The main driver genes were KRAS, TP53, CDKN2A, and SMAD4. Patients with KRAS mutation showed worse OS than those without (p = 0.048). DDR deficiency were identified in 15.38% of overall patients, mainly occurred in BRCA2 (4.62%), ATM (4.10%), RAD50 (1.54%) and MLH1 genes (1.03%). No significant improvement of OS existed between patients with or without DDR mutations (p = 0.88). Treatment with olaparib (adjusted HR, 0.2550; P = 0.0720) or platinum-based chemotherapy (adjusted HR, 0.1308; P = 0.0185) respectively decreased hazard of death in patients with DDR mutation. Besides BRCA gene, ATM mutant patients treated with olaparib harbored prolonged median OS than those without olaparib treatment (22.25 vs 15.2 month). Despite a little higher PD-L1 expression rate were seen in DDR mutant patients (29.17% vs 20.51%), no statistical correlation between tumor mutation burden level and DDR mutation was identified. And in patients treated with PD-1 blockade, 2 patients of DDR wild-type group both had SD, whereas of the remaining 5 patients with DDR deficiency, 1 was evaluated as PR, 3 as SD, and 1 as PD (ORR, 0 wt vs 20% mut). Conclusions: In this multi-center retrospective study, we deciphered the intra-tumoral genetic heterogeneity in Chinese PDAC population, which differs from western patients cohort to some extent. We found the potential role of germline and somatic DDR mutation status in predicting the response to olaparib and platinum-based chemotherapy, especially with BRCA or ATM mutation. However, DDR alteration was limited in prediction of hypermutational status and sensitivity to PD-1 blockade. Our study may provide a valuable evidence for clinical application of DDR mutation as a potential biomarker for precise treatment.

Exceptional sustained responses to ipilimumab/nivolumab (ipi/nivo) in patients (pts) with advanced pancreaticobiliary cancers and germline DNA damage repair (DDR) mutations.

e16757 Background: Immune checkpoint inhibitors (ICIs) have not shown meaningful clinical activity in unselected pts with pancreaticobiliary cancer. DDR-deficient tumors have increased genomic instability, including increased tumor mutation burden (TMB), more tumor-infiltrating immune cells, and enrichment of a T cell-inflamed signature. We hypothesized that pts with DDR deficiency may be sensitive to ICIs. Methods: Utilizing the IRB-approved database at the University of Miami, we identified pts with advanced pancreaticobiliary cancer with germline DDR mutations who were treated with dual ICI. Results: Eleven pts were identified (3 BRCA1, 4 BRCA2, 1 RAD51C, 1 RAD51D, 1 ATM, and 1 PALB2). There were two complete responses (CR), one partial response (PR), three stable disease (SD), two progressive disease (PD), and three pending evaluation. Evaluable responses are sustained for 22 months (m), 19m, and 7m, respectively. All pts had microsatellite stable tumors and none had high TMB. Among pts with responses, TMB was 4, 8, and 8 mut/Mb, respectively. One pt with a CR had gBRCA1 with pancreatic adenocarcinoma (PDAC) s/p distal pancreatectomy/splenectomy, adjuvant gemcitabine (gem)/capecitabine, biopsy-proven recurrence in lung and retroperitoneum 12m later, initiated ipi/nivo, and achieved a CR ongoing for 22m on nivo maintenance. Second pt with a CR had gBRCA1 and unresectable cholangiocarcinoma (CC), with disease progression after gem/cisplatin (cis), therapy switched to ipi/nivo. After 4 doses, an incidental cerebellar lesion was found which was biopsy-proven CC, therefore taken off treatment. Pt has been in CR for 19m without further therapy. The pt with a PR had RAD51C and metastatic PDAC s/p FOLFIRINOX for 6m, followed by olaparib for 12m. At progression, disease rapidly progressed through 5-fluorouracil/nanoliposomal irinotecan, gem/nab-paclitaxel/cis, and FOLFIRINOX. Pt was initiated on ipi/nivo with immediate improvement in pain and tumor markers; PR ongoing for 7m with continued clinical and tumor marker improvement on nivo maintenance. Additional correlative studies (RNA sequencing, Hyperion Imaging, mutation allele fraction analysis) among responders vs. nonresponders will be reported at the meeting. Conclusions: In this series, 6 out of 8 evaluable pts with advanced pancreaticobiliary cancers had disease control with ipi/nivo. This series suggests that tumors with germline DDR mutations may be responsive to ICIs. Further evaluation is warranted.

Prognostic Value of Germline DNA Repair Gene Mutations in De Novo Metastatic and Castration-Sensitive Prostate Cancer.

Germline DNA damage repair gene mutations (gDDRm) have been found in approximately 12% of patients with metastatic prostate cancer (mPCa). Previous studies of the clinical impact of gDDRm have mainly been in the setting of metastatic castration-resistant prostate cancer (mCRPC). This study aimed to determine the prognostic value of gDDRm in de novo metastatic and castration-sensitive prostate cancer (mCSPC). We retrospectively collected the records of 139 consecutive men with de novo mCSPC who initially received systemic therapies following guidelines. This included 128 patients who underwent genetic testing at our center and 11 patients referred to our center after being identified as gDDRm carriers. Time to mCRPC was collected. Kaplan-Meier and log-rank analysis were used to analyze the association between gDDRm and clinical outcomes. Survival outcomes were adjusted using multivariable Cox regression models. Of the 139 patients with de novo mCSPC, 28 gDDRm carriers were identified. Median time progressing to mCRPC was significantly shorter in patients carrying gDDRm than in those without mutations (8.3 vs 13.2 months; hazard ratio [HR], 2.37; p < .001). Moreover, median progression time was almost halved in BRCA2 carriers (6.3 vs. 13.2 months; HR, 3.73; p < .001). Subgroup analysis revealed that the presence of gDDRm indicated poor therapy response regardless of disease volume and prostate-specific antigen nadir within the first 7 months. Presence of gDDRm remained independently associated with increased risk of progression to mCRPC in multivariate analysis (adjusted HR, 1.98; p = .006). Our study suggested that positive gDDRm status predicted rapid progression to castration resistance in patients with de novo mCSPC. We propose identifying gDDRm status at the time of diagnosis for mCSPC patients, considering it is the first step of tailoring individualized treatment. In addition, DNA repair genes were a good therapeutic target for poly (ADP-ribose) polymerase inhibitors, and our results call for more frontline targeted therapy trials in gDDRm carriers to prolong the progression time. Results of this study suggested that positive germline DNA damage repair gene mutation (gDDRm) status predicted earlier progression to castration resistance in patients with de novo metastatic and castration-sensitive prostate cancer (mCSPC). These findings indicated the importance of intense therapy for some subgroups of mCSPC, especially for mCSPC harboring gDDRm with low-volume disease. Moreover, gDDRm was a good therapeutic target for poly (ADP-ribose) polymerase inhibitors, and these findings call for more molecular marker driven trials moving to the mTNPC setting.

Treatment response comparisons between ATM and BRCA2 germline carriers for mCRPC.

63 Background: Over 10% of men with metastatic prostate cancer (PC) have germline DNA damage response gene alterations; most studies have reported BRCA2 alone or an aggregate of BRCA1, BRCA2 and ATM. Emerging data suggest ATM mutations have distinct effects and warrant individual gene evaluation. We hypothesize that, compared to patients (pts) carrying germline BRCA2 mutations (g BRCA2mut), pts carrying germline ATM mutations (g ATMmut) may have different treatment response to androgen-receptor-targeted agents, docetaxel, platinum therapy and PARP inhibitors (PARPi). Methods: This is an international, multicenter, retrospective case-control study of pts with PC who underwent clinical germline genetic testing between 2014-2019. We identified pts with g ATMmut and matched pts with g BRCA2mut by stage at diagnosis and year of testing. IRB-approved medical records review, χ² and log rank tests were performed. Results: 39 g ATMmut cases and 39 matched g BRCA2mut cases were identified for total of 78. A third (13/39) of pts in each cohort had metastases at diagnosis. Of those diagnosed with localized stage, 81% (21/26) of gATMmut and 73% (19/26) of g BRCA2mut developed metastasis (median times to metastasis 69 vs 49 months, respectively (p=0.1)). Pts in g ATMmut and g BRCA2mut cohorts had similar age, Gleason grade, and PSA at diagnosis. We did not observe a difference in PSA50 response rates to abiraterone, enzalutamide, docetaxel, or carboplatin for mCRPC (Table). g BRCA2mut pts were more likely to respond to PARPi for mCRPC; where available, somatic loss of heterozygosity (LOH) data will be reported at final presentation. Conclusions: While response to standard therapies appears similar between g ATMmut and g BRCA2mut cohorts, response to PARPi in g ATMmut appears to be attenuated compared to g BRCA2mut. More studies are needed and pts with g ATMmut warrant prioritization for novel treatment strategies.[Table: see text]

Utilization of somatic comprehensive genomic profiling (CGP) to identify patients (pts) with pancreatic cancer (PC) that harbor germline DNA damage repair (DDR) gene alterations.

760 Background: Somatic and germline DDR gene alterations in PC have been postulated to positively predict response to DNA damaging cytotoxic agents. Due to the relatively high prevalence of germline DDR gene alterations, germline testing is recommended in all pts with PC. We examined whether somatic CGP can be used to reliably identify PC pts that merit germline testing. Methods: We retrospectively reviewed the electronic medical records of PC pts who underwent both somatic CGP (utilizing the Foundation One assay) and germline testing. DDR gene mutations were categorized as somatic-pathogenic, somatic-variant of uncertain significance (VUS), germline-pathogenic and germline-VUS. For somatic testing, DNA was extracted from formalin fixed paraffin embedded (FFPE) clinical specimens and CGP was done on hybrid-capture, adaptor ligation based libraries to a mean coverage depth of &gt; 600 for up to 315 genes plus 47 introns from 19 genes frequently rearranged in cancer. Germline genetic testing was performed on submitted blood or saliva samples, utilizing commercial assays; next generation or Sanger sequencing of all coding regions and adjacent intronic nucleotides were performed. Results: Ninety-three pts had somatic CGP data, 51 (55%) pts had both somatic CGP and germline data available. Among the 51 pts with both germline and somatic data available, DDR gene alterations that were somatic-pathogenic, germline-pathogenic, somatic-VUS and germline-VUS were present in 7 (13.7%), 7 (13.7%), 23 (45.1%) and 16 (31.4%) pts, respectively. Of the 7 pts with somatic-pathogenic alterations, 5 (71%) had a concordant germline alteration and of the 7 pts with germline-pathogenic alterations, 5 (71%) had a concordant somatic alteration. Of the 23 pts with somatic-VUSs, 12 (52%) had a concordant germline VUS and of the 16 pts with germline-VUSs, 12 (75%) had a concordant somatic VUS. Conclusions: Both somatic and germline DDR gene alterations are common in PC pts. Despite the relatively high concordance rate between somatic and germline pathogenic DDR gene alterations, somatic CGP will miss approximately one fourth of the germline DDR gene alterations.

Amino modification enhances reproductive toxicity of nanopolystyrene on gonad development and reproductive capacity in nematode Caenorhabditis elegans

Although amino modified nanopolystyrene could cause toxicity on environmental organisms, the effect of amino modification on nanopolystyrene toxicity is still largely unclear. We here employed Caenorhabditis elegans as an animal model to compare the effects between pristine and amino modified nanopolystyrene particles in inducing reproductive toxicity. Nanopolystyrene (35 nm) could cause the damage on gonad development as indicated by the endpoints of number of total germline cells, length of gonad arm, and relative area of gonad arm. Nanopolystyrene exposure also reduced the reproductive capacity as reflected by the endpoints of brood size and number of fertilized eggs in uterus. Moreover, amino modification enhanced nanopolystyrene toxicity on both the gonad development and the reproductive capacity. Additionally, induction of germline apoptosis and formation of germline DNA damage contributed to the enhancement of nanopolystyrene toxicity in reducing reproductive capacity by amino modification. Our results highlight the potential environmental risk of amino modified nanopolystyrene in inducing reproductive toxicity on gonad development and reproductive capacity of environmental organisms.

Genomic characterization of brain metastases (BM) in high-grade serous ovarian cancer (HGSOC).

e13580 Background: BM are a rare occurrence in ovarian cancer (OC) and their molecular characteristics is virtually unknown. DNA damage repair (DDR) deficiency is prevalent in OC, and co-mutated TP53 and any DDR denotes high tumor mutation burden (TMB). We genetically characterized a unique series of high-grade serous ovarian cancer (HGSOC) patients who developed BM to identify alterations of potential clinical relevance. Methods: Whole-exome sequencing (2x150bp, SureSelectXT Library Prep Kit, Illumina’s NovaSeq platform) was performed in matched BM, primary tumors (PT) and normal tissue. DNA was extracted from FFPE samples using QIAamp DNA FFPE Tissue Kit (Qiagen, Germany). All mutations were checked with Catalogue of Somatic Mutations in Cancer (COSMIC) and Integrative Genomics Viewer (IGV). Results: Study group included 10 HGSOC patients (International Federation of Gynecology and Obstetrics classification (FIGO) II-IV, mean age at diagnosis 48 years, range 35-59). Median time from primary HGSOC diagnosis to BM was 38 months (range, 18 to 149). TP53 somatic mutations were found in both primary tumor (PT) and BM in 8 patients. The other 2 cases harbored TP53 mutations not reported in COSMIC catalogue: p.S60L and intronic TP53 mutation preceding p.I322 (IGV). In 9 cases TP53 mutations coexisted with germline or somatic DNA damage repair deficiency. Four cases contained BRCA1 mutations (all germline), and none harbored germline BRCA2 mutation. Other mutated genes included MLH1 (2 somatic, 2 germline), ATR (4 germline, 1 somatic), AMT (1 somatic), RAD50 (1 somatic), ERCC4 (1 somatic), FANCD2 (1 somatic) and RPA1 (1 germline). Three mutation signatures defined in the COSMIC database were indentified in BM: 6, 20 and 30. In 6 cases these mutations were shared in PT, and in another 4 their presence in PT could not be determined due to technical reasons. Median survival from BM was 31 months (range, 5 to 184). Conclusions: Genomic analysis of BM provides an opportunity to identify potentially clinically informative alterations. Mutational profiles in PT are generally reflected in BM. Detected genetic alterations suggest their potential sensitivity to PARP inhibitors and immunotherapy.

Germline DNA damage repair gene alterations in Chinese prostate patients: More than HRR and MMR.

e13041 Background: Prostate cancer is a worldwide most occurred malignancy in male population. Genetic aberrations of homologous recombination repair (HRR) pathway were proved to be associated with aggressive disease and poorer outcome but may also lead cancer cells more vulnerable to PARP inhibitors. Other than HRR, germline variants in mismatch repair (MMR), nucleotide excision repair (NER) were also identified. Thus, it is important to clarify the distribution of germline alterations of DDR pathways in Chinese prostate cancer patients. Methods: Sixty-five prostate cancer patients unselected for family history, stage of disease, or age at diagnosis were collected. DNA from peripheral blood was extracted. Whole-exon was captured and sequenced subsequently using MGI-SEQ 2000 platform. A total of 229 DDR genes were selected for further analysis. Germline variants were determined to be deleterious according to the ACMG 2015 guidelines. Results: Ten of 65 patients (15.38%) had 7 pathogenic/likely pathogenic germline variants involving 5 different genes: FANCD2 (n = 5), BRCA2 (n = 3), CHEK2 (n = 1), ATM (n = 1) and RECQL (n = 1). Nine patients (13.84%) carried variants predicated to be deleterious via in silico predicators. Taken together, deleterious/potential deleterious germline variants were categorized into 5 DDR pathways which were Fanconi Anemia (9.2%), HRR (9.2%), MMR (4.6%), BER (4.6%) and NER (1.5%). Patients with pathogenic/likely pathogenic germline variants had tendency to be early-onset (mean age [range] at diagnosis, 52[43-67] versus 64[37-80] years, P = 0.001). PSA level at initial diagnosis and self-reported family history did not have significant difference between deleterious mutation carriers and non-carriers (P = 0.396 for PSA level, P = 0.753 for family history). Moreover, metastasis and Gleason score were not associated with deleterious germline variants. Conclusions: Our data showed approximately 52% DDR mutation occurred in other DNA repair pathways besides HRR and MMR, which was a unique spectrum of germline variants in Chinese prostate cancer patients. This indicated distinct genetic etiology and potential therapeutic targets of prostate cancer in Chinese population. Moreover, early-onset in patients with deleterious germline variants is an important clinical character. Whole DDR pathway genes’ testing and counseling should be considered for application for young individuals.

Predictors of germline DNA damage repair gene mutations (gDDRm) in patients (pts) with metastatic castration-resistant prostate cancer (CRPC).

159 Background: gDDRm are present in 6-12% of pts with CRPC and have implications for prognosis, treatment outcomes and familial screening. This study's aim was to identify clinical/pathologic characteristics associated with a higher risk of a pt harboring a gDDRm. Methods: 631 consecutive pts with metastatic prostate cancer were screened for germline mutations in 22 DNA repair genes (including ATM, BRCA1/2, MSH2/6, FANC/ERCC members). Clinical/pathologic characteristics (age at diagnosis, visceral metastases (mets) at time of CRPC, Gleason score, intraductal/cribriform histology (I/C) at diagnosis, family history (FHx) of prostate, breast, ovarian, or pancreatic cancer, time from androgen deprivation therapy initiation to CRPC) were compared between gDDRm+ and gDDRm- cases. A multivariate logistic model of gDDRm status was constructed using purposeful selection of covariates where clinical judgement was employed in addition to statistical significance. A weighted scoring system was created by multiplying each risk factor (RF) by its estimated β coefficient. A pt’s total score was calculated by the sum of each weighted RF. Results: gDDRm+ were identified in 38/631 pts (6.0%, BRCA2 = 28, ATM = 4, BRCA1 = 2, PALB2 = 2, MSH2 = 1, ERCC3 = 1). 29 gDDRm+ and 128 gDDRm- cases with complete clinical/pathologic information were included in the model. Multivariate modeling revealed that visceral mets, FHx and I/C were statistically significantly associated with gDDRm+; age ≤ 65 was included in the model because it was considered clinically relevant (Table). Based on the model results, the weights of each RF are: visceral mets (2), FHx (1), I/C (2), age ≤ 65 (1). Using a total score cut-off ≥ 1, the model achieves a sensitivity, specificity, positive predictive value, and negative predictive value of 97%, 31%, 24%, and 98%, respectively. Conclusions: In this cohort, visceral mets, FHx and I/C were independently associated with a higher risk of harboring a gDDRm. The predictive model may aid in selecting pts for gDDRm screening. Model validation is required. [Table: see text]

Tumor testing in men with prostate cancer to predict for germline DNA-damage repair mutations.

229 Background: Current guidelines recommend genetic testing for patients (pts) who have BRCA1/2 mutations on tumor-only testing, where germline is not subtracted. The clinical utility of this approach, and possible inclusion of other DDR genes associated with cancer susceptibility, has not been examined in men with prostate cancer. Methods: Pts with mostly advanced prostate cancer were prospectively enrolled to a matched tumor-germline DNA sequencing protocol and consented for disclosure of germline results. Germline analysis was done with an institutional, CLIA-certified next generation sequencing (NGS) platform (MSK-IMPACT) and analyzed for likely pathogenic or pathogenic germline mutations in at least 76 cancer susceptibility genes. Clinical data was retrieved from the medical record. We report on the frequencies in the germline and in the tumor of a subset of DDR genes. Results: 1243 men had analysis of both germline and tumor. Median age 64 (range 35-90). 12% had a second malignancy and 40% reported a relative with prostate cancer. 19% were of Ashkenazi Jewish (AJ) descent. 330 (27%) had any mutation in BRCA1/2, ATM, CHEK2, PALB2, RAD51C, RAD51D, MSH2, MSH6, MLH1, PMS2. 127 (10%) had a germline mutation, of which 36% were AJ founder mutations. For each gene, the percentage of mutations found in germline and tumor is shown in the table. Conclusions: Of prostate cancer pts found to have any DDR mutation on tumor-germline testing, 29% had a germline mutation. Proportion of germline mutations was highest for PALB2, CHEK2 and BRCA2. These findings not only support germline testing when BRCA1/2 mutations are found tumor-only sequencing, but also support germline testing when other DDR mutations are seen. Clinical trial information: NCT01775072. [Table: see text]

Germline and Somatic DNA Damage Repair Gene Mutations and Overall Survival in Metastatic Pancreatic Adenocarcinoma Patients Treated with FOLFIRINOX.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with lack of predictive biomarkers. We conducted a study to assess DNA damage repair (DDR) gene mutations as a predictive biomarker in PDAC patients treated with FOLFIRINOX. Indiana University Simon Cancer Center pancreatic cancer database was used to identify patients with metastatic PDAC, treated with FOLFIRINOX and had tissue available for DNA sequencing. Baseline demographic, clinical, and pathologic information was gathered. DNA isolation and targeted sequencing was performed using the Ion AmpliSeq protocol. Overall survival (OS) analysis was conducted using Kaplan-Meier, logistic regression and Cox proportional hazard methods. Multivariate models were adjusted for age, gender, margin status, CA 19-9, adjuvant chemotherapy, tumor and nodal stage. Overall, 36 patients were sequenced. DDR gene mutations were found in 12 patients. Mutations were seen in BRCA1 (N = 7), BRCA2 (N = 5), PALB2 (N = 3), MSH2 (N = 1), and FANCF (N = 1) of all the DDR genes sequenced. Median age was 65.5 years, 58% were male, 97.2% were Caucasian and 51.4% had any family history of cancer. The median OS was near significantly superior in those with DDR gene mutations present vs. absent [14 vs. 5 months; HR, 0.58; 95% confidence interval (CI), 0.29-1.14; log-rank P = 0.08]. Multivariate logistic (OR, 1.47; 95% CI, 1.04-2.06; P = 0.04) and Cox regression (HR, 0.37; 95% CI, 0.15-0.94; P = 0.04) showed presence of DDR gene mutations was associated with improved OS. In a single institution, retrospective study, we found that the presence of DDR gene mutations are associated with improved OS in PDAC patients treated with FOLFIRINOX.