Common Germline Mutations Research Articles

Research progress on pathogenic germline mutations in malignant tumors

Malignant tumors are closely related to various genetic and environmental factors. Pathogenic germline gene mutations play a key role in the occurrence and development of some malignant tumors. Some germline mutations can increase the risk of malignant tumors. For example, those with homologous recombination repair gene BRCA1/2 mutations are prone to breast cancer, ovarian cancer, etc., and some germline mutations are associated with genetic syndromes. For instance, 80% of hereditary non-polyposis colon cancers are associated with mutations in mismatch repair genes such as MLH1 and MLH2. In addition, 70% of Li-Fraumeni syndrome patients have harbored germline TP53 mutations. With the development of next-generation sequencing technology, more and more germline gene mutations have been discovered recently, which is of great significance for the prevention, screening, and treatment of tumors. This article has provided a review for common germline mutations, detection methods, and advances in drug therapy.

Germline EGFR mutations in lung cancer (Review).

Lung cancer is the leading cause of cancer-related death and familial lung cancer is a potential contributing factor. Epidermal growth factor receptor (EGFR) mutations are important events in carcinogenesis. The present study summarized the common germline mutations of EGFR, including T790M, V843I, R776H and P848L, and provided detailed information regarding each mutation site and potential treatment strategies. Individuals with germline mutations may develop lung cancer upon exposure to environmental stimuli such as smoking, air pollution or radiological contamination, or due to the occurrence of another somatic mutation. The present study recommends regular physical examinations as well as population-wide germline mutation screening for early detection and diagnosis of lung cancer.

Abstract 4512: My Pediatric and Adult Rare Tumor Network (MyPART): integrating longitudinal, clinical, molecular, and patient-reported outcomes for rare tumors

Abstract Background: Rare tumors are defined as <15 cases/100,000 people/year and present an unmet need due to lack of effective medical treatments, paucity of biospecimens and research models, and difficulty accruing to clinical trials. MyPART (My Pediatric and Adult Rare Tumor Network) was established to: 1) engage patients/advocates as partners in rare tumor research, 2) provide expertise and personalized health care to children and young adults with rare tumors, and 3) build databases and tools to advance research on new treatments for rare tumors. We have developed a natural history and biospecimen acquisition study (NCT03739827), enrolling patients with rare solid tumors, their family members, and participants with germline mutations at increased rare tumor risk. Method: Participants in our natural history study enroll remotely or come to the National Institutes of Health Clinical Center. Participants complete medical and family history forms, patient reported outcomes (PROs), and provide tumor samples and blood and/or saliva for DNA/RNA analysis. For patients coming to the Clinical Center, blood samples are collected for immune phenotyping and cytokine analysis. Clinical staff extract medical records for downstream analyses. Tumors are analyzed using a 500+ gene panel and genomic analysis. Participants are followed yearly to collect data on recurrence, progression, PROs, development of additional tumors, and response to treatments such as standard of care and any treatment trials they may join. Results: We report a clinical and molecular summary of the first 200 participants (66% female, 35% male), with neuroendocrine neoplasms (NEN), adrenocortical cancer (ACC), SDH-deficient gastrointestinal stromal tumor (sdGIST), chordoma, medullary thyroid cancer (MTC), and other less commonly enrolled tumors totaling 35 different tumor types. Participants come from 46 US states and 9 countries. Early results show tumor-specific differences in mutations, treatment/management, PROs, and self-reported non-tumor health issues. The most common pathogenic germline mutations are SDHA/SDHB/SDHC in sdGIST and RET in MTC and other tumors. The most common pathogenic tumor mutations are TP53 and CTNNB1 in ACC, SDHA/B and TP53 in sdGIST, MEN1 in NEN, RET and HRAS in MTC, and SMARCB1 in chordoma. Clinically significant levels of anxiety and pain are more frequent in ACC, NEN, and sdGIST. Conclusions: By developing methods to provide value to rare tumor patients, using a large catchment area and opportunity for remote participation, and collecting data in a tumor-agnostic way, we can learn about multiple rare tumors and share findings more quickly than if each rare tumor was studied alone. We describe the MyPART cohort and challenges to overcome for successful longitudinal rare tumor natural history studies. Citation Format: Shadin Ahmed, Margarita Raygada, Robin Lockridge, Mary Frances Wedekind Malone, Jaydira Del Rivero, John W. Glod, Barbara J. Thomas, Donna Bernstein, Markku M. Miettinen, Liqiang Xi, Jung Kim, Manoj Tygagi, Mark Raffeld, Kenneth Aldape, Ashkan A. Malayeri, Abby B. Sandler, Brigitte C. Widemann, Karlyne M. Reilly. My Pediatric and Adult Rare Tumor Network (MyPART): integrating longitudinal, clinical, molecular, and patient-reported outcomes for rare tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4512.

Genomic alterations in patients with prostate cancer with liver metastases.

248 Background: mCRPC patients with liver metastases have a poor prognosis and often progress rapidly on a variety of treatments. Previously, preliminary ctDNA analyses of mCRPC patients with liver metastases showed a range of commonly altered genes in patients with liver metastases (Ranasinghe et al; 2019). In this follow-up, we evaluated ctDNA alterations in an expanded cohort of mCRPC patients with liver metastases. Methods: From Tulane Cancer Center, retrospective review of mCRPC patients was used to identify patients with confirmed liver metastasis. All liver metastases were confirmed based on imaging data. All patients included had ctDNA evaluated with a multi-gene cancer panel via Guardant 360 assay (Guardant Health, Inc). Additional clinical annotation including family history, germline testing, staging, imaging, and laboratory values. Statistical analyses were performed with Fisher’s Exact and Wilcoxon Rank Sum tests. Results: 158 mCRPC patients with appropriate diagnostic imaging as well as ctDNA testing. From this group, 8% (n= 12) had confirmed liver metastases. Among the patients with liver metastasis, the most common alterations detected were in AR (50%; 6/12) and PIK3CA (25%; 3/12). Patients with liver metastasis were more likely to have amplifications in FGFR1 detected in their ctDNA (OR= 14.40; 95% C.I. (1.83, 113.22); p= 0.03). In addition to ctDNA, germline data was assessed, and it was found that patients with liver metastasis were more likely to have a pathogenic germline mutation (OR= 7.61; 95% C.I. (2.85, 20.31); p<.0001). The most common germline mutations detected in patients with liver metastasis were in BRCA2 (n= 3) and TP53 (n= 2). Conclusions: Though liver metastasis are less common in prostate cancer, it often occurs following extensive treatment and results in a poor prognosis for patients. In patients with liver metastasis, FGFR1 amplification was more often detected in ctDNA. Importantly, patients with liver metastasis were significantly more likely to have a pathogenic germline alteration.

CNSC-37. ATYPICAL GERMLINE MUTATIONS AND PRIMARY CNS TUMORS: A SINGLE-CENTER CASE SERIES AND LITERATURE REVIEW

Abstract A growing spectrum of germline mutations and their association with primary CNS tumors has been described over the last decade. These germline mutations are implicated in regulation of DNA integrity and repair, telomere maintenance, and cell cycle regulation resulting in aberrant cellular proliferation and immune surveillance evasion. To date, there are no well-defined guidelines for primary CNS tumor surveillance for these patients. Moreover, the exact role of traditional chemotherapy, immunotherapy, and radiation is unclear. We present a single-institution case series of adult patients with primary CNS tumors with atypical germline mutations and literature review. The most common germline mutations encountered involved heterozygous mutations of one of the mismatch repair (MMR) genes (MSH2, PMS2, MLH1). All patients developed high-grade gliomas defined as astrocytoma or glioblastoma WHO grade 4 based on the WHO 2021 classification. Germline mutations involving RAD51C, POT1, IDH1/2, MutyH, NTHL1, PALB2, and CHEK2 were associated with gliomas of variable grades and molecular subtypes. Non-glial tumors, including atypical rhabdoid tumors, medulloblastomas, hemangioblastomas, and meningiomas were found in association with germline SMARCB1, ATM, BRCA1, and CHEK2 mutations respectively. Review of the existing literature and knowledge obtained from our case series suggests several important concepts: (1) there is an increased risk of both glioma and non-glial tumor types in several atypical germline mutations, (2) multiple risk genes or variants of unknown significance likely contribute to primary brain tumor formation, (3) germline MMR mutations associated with high-grade glioma may be MMR gene-specific with potential increased risk of resistance and/or disease progression in the presence of alkylating agents such as temozolomide, (4) several germline mutations may increase risk of secondary tumor development after radiation, and (5) the role of screening for atypical germline mutations and subsequent disease surveillance remain unanswered.

Clinical significance of next generation sequencing (NGS) in Chinese patients with relapsed/refractory Wilm’s tumor.

e22014 Background: Medical advances have been greatly improved in the five-year survival rate for Wilms’ tumor, but the survival is still dismal for relapsed/refractory (R/R) patients. In the present study, we aimed to investigate the genomic profiling and the incidence of germline cancer susceptibility mutationsof Chinese patients with R/R WT. Methods: Next-generation sequencing (NGS) of tumor specimens with matched blood samples obtained from R/R pediatric WT in Sun Yat-Sen University Cancer Center were used in a CAP-certified laboratory (Simcere Diagnostic Co, Ltd). Clinical information including age, gender and tumor histology were collected. Somatic and germline mutations including single nucleotide variants (SNV), insertion-deletion variants (Indels), copy number variations (CNVs) and fusion, as well as tumor mutational burden (TMB) were analyzed. Results: Nineteen patients with R/R WT were enrolled in this study, including 10 males and 9 females, with a median age of 4 years old (range, 0-14). All of the pathology was identified as favorable histology WT (FHWT). Somatic mutations were detected in 84.21% (16/19) of patients, and CNVs accounted for the majority of the total somatic aberrations, followed by SNVs. The most common somatic mutations were identified in the following genes, CTNNB1 , ERBB2, MCL1 , CDK2 and MDM4. Of the top 3 frequently mutated genes, the mutation frequency and their most common mutation type were CTNNB1, 26%, in-frame deletion, missense mutation; ERBB2 21%, missense mutation, amplification; MCL1 21%, amplification. It is worth noting that MCL1 mutation has never been reported in Chinese R/R WT patients before, which may be a potential valuable mechanism. Germline mutations were detected in 89.47% (17/19) of patients, and CNVs accounted for the majority of the total germline aberrations, followed by SNVs. The most common germline mutations were identified in the following genes, MCL1, RET, ALK, EPCAM, and FANCA. Of the top frequently mutated genes frequency and most common mutation type were MCL1 21%, amplification; RET 21% missense mutation, multiple mutations. There are also some suspected clinically pathogenic germline mutation of genes CDK4 , ERBB2, and MDM4 . All the mutation type were amplification. Notable cancer driver mutations were also characterized, such as the amplifications of ERBB2 / MET/EGFR / FGFR1, and the point mutations of CHEK2/FBXW7/NF1. The median TMB was 1.47 (range, 0-7.8). Conclusions: Overall, clinical and new results were detected in 14 (73.68%) in Chinese R/R WT patients. We discovered some driver genes mutations which potentially sensitive to the corresponding targeted drugs in Chinese R/R WT patients. Large sample size was needed to provide a better understanding of molecular features in R/R WT patients to achieve precision medicine.

Longitudinal ctDNA alterations in germline positive CRPC patients.

275 Background: Circulating tumor-derived DNA (ctDNA) is an accessible method for characterizing somatic alterations. We report longitudinal ctDNA screenings of mCRPC patients (pts) who have had germline testing. Methods: Patients with both germline testing and ctDNA assessment were included. Germline testing was performed with a multi-gene cancer panel from Invitae (50-83 genes) and somatic alterations in ctDNA were identified by testing with Guardant 360 (70-83 genes). ctDNA alterations were characterized as deletions, frameshift, missense, nonsense, and other mutations. A total of 177 patients in various stages of therapy had both ctDNA and germline DNA tested. Results: From 2015-2021, 177 mCRPC patients were included and had an average of 3 ctDNA tests. 11.3% (20/177) had pathogenic or likely-pathogenic germline mutations. The common pathogenic germline mutations were in BRCA2 (25%; 5/20), ATM (10%; 2/20), and MSH2 (10%; 2/20). In ctDNA, missense mutations were the most prevalent type of gene alteration in germline negative (n = 539/790, 68%) and germline positive (n = 124/218, 57%) followed by frameshift mutations at 22% (n = 48/218) in germline positive and 10% (n = 80/790) in germline negative patients. Germline positive patients were more likely to have somatic frameshift mutations (OR = 2.09, 95% C.I. (1.3792, 3.1618), p = 0.001) and less likely to have missense mutations (OR = 0.61, 95% C.I. (0.4519, 0.8351), p = 0.002). Other alterations including deletions, nonsense, and other mutations were not significantly different. Of the germline positive pts, BRCA2 mutation was associated with the highest number of somatic alterations. Conclusions: Germline positive CRPC patients were more likely to have frameshift mutations and less likely to missense mutations compared to germline negative CRPC patients. Patients with germline mutations in BRCA2 and TP53 had the highest number of somatic alterations detected in ctDNA over the course of ctDNA evaluation.

The Mutational Landscape of Early-Onset Breast Cancer: A Next-Generation Sequencing Analysis.

BackgroundAround 5%–7% of breast cancer cases are diagnosed in women younger than 40, making it the leading cause of female cancer in the 25- to 39-year-old age group. Unfortunately, young age at diagnosis is linked to a more aggressive tumor biology and a worse clinical outcome. The identification of the mutational landscape of breast cancer in this age group could optimize the management.MethodsWe performed NGS analysis in paraffin blocks and blood samples of 32 young patients with breast cancer [<40 years] and 90 older patients during the period 2019 through 2021. All patients were treated in a single institution at the Oncology Department of “Alexandra” Hospital, Medical School, University of Athens, Greece.ResultsBreast tumors were characterized more frequently by HER2 overexpression [25% vs 18.9%], higher ki67 levels [75% vs 61%] and lower differentiation [71.9% vs 60%] in the younger group. PIK3CA [6/20; 30%] and TP53 [6/20; 30%] were the most frequent pathogenic somatic mutations identified in young patients, while one case of BRCA2 somatic mutation [1/20; 5%] and one case of PTEN somatic mutation [1/20; 5%] were also identified. PIK3CA mutations [16/50; 32%] and TP53 mutations [20/50; 40%] were the most common somatic mutations identified in older patients, however other somatic mutations were also reported (ATM, AKT, CHEK2, NRAS, CDKN2A, PTEN, NF1, RB1, FGFR1, ERBB2). As for germline mutations, CHEK2 [3/25; 12%] was the most common pathogenic germline mutation in younger patients followed by BRCA1 [2/25; 8%]. Of note, CHEK2 germline mutations were identified less frequently in older patients [2/61; 3%] among others [BRCA1 (2/61; 3%), ATM (2/61; 3%), APC (1/61; 1,6%) and BRCA2 (1/61; 1,6%)].ConclusionWe here report the mutational profile identified via NGS in patients with early-onset breast cancer compared to their older counterparts. Although the sample size is small and no statistically significant differences were detected, we highlight the need of genetic testing to most patients in this subgroup.

Germline DDX41 mutations cause ineffective hematopoiesis and myelodysplasia.

DDX41 mutations are the most common germline alterations in adult myelodysplastic syndromes (MDSs). The majority of affected individuals harbor germline monoallelic frameshift DDX41 mutations and subsequently acquire somatic mutations in their other DDX41 allele, typically missense R525H. Hematopoietic progenitor cells (HPCs) with biallelic frameshift and R525H mutations undergo cell cycle arrest and apoptosis, causing bone marrow failure in mice. Mechanistically, DDX41 is essential for small nucleolar RNA (snoRNA) processing, ribosome assembly, and protein synthesis. Although monoallelic DDX41 mutations do not affect hematopoiesis in young mice, a subset of aged mice develops features of MDS. Biallelic mutations in DDX41 are observed at a low frequency in non-dominant hematopoietic stem cell clones in bone marrow (BM) from individuals with MDS. Mice chimeric for monoallelic DDX41 mutant BM cells and a minor population of biallelic mutant BM cells develop hematopoietic defects at a younger age, suggesting that biallelic DDX41 mutant cells are disease modifying in the context of monoallelic DDX41 mutant BM.

Detection and analysis of common pathogenic germline mutations in Peutz-Jeghers syndrome.

BACKGROUNDDifferent types of pathogenic mutations may produce different clinical phenotypes, but a correlation between Peutz-Jeghers syndrome (PJS) genotype and clinical phenotype has not been found. Not all patients with PJS have detectable mutations of the STK11/LKB1 gene, what is the genetic basis of clinical phenotypic heterogeneity of PJS? Do PJS cases without STK11/LKB1 mutations have other pathogenic genes? Those are clinical problems that perplex doctors.AIMThe aim was to investigate the specific gene mutation of PJS, and the correlation between the genotype and clinical phenotype of PJS.METHODSA total of 24 patients with PJS admitted to the Air Force Medical Center, PLA (formerly the Air Force General Hospital, PLA) from November 1994 to January 2020 were randomly selected for inclusion in the study. One hundred thirty-nine common hereditary tumor-related genes including STK11/LKB1 were screened and analyzed for pathogenic germline mutations by high-throughput next-generation sequencing (NGS). The mutation status of the genes and their relationship with clinical phenotypes of PJS were explored.RESULTSTwenty of the 24 PJS patients in this group (83.3%) had STK11/LKB1 gene mutations, 90% of which were pathogenic mutations, and ten had new mutation sites. Pathogenic mutations in exon 7 of STK11/LKB1 gene were significantly lower than in other exons. Truncation mutations are more common in exons 1 and 4 of STK11/LKB1, and their pathogenicity was significantly higher than that of missense mutations. We also found SLX4 gene mutations in PJS patients.CONCLUSIONPJS has a relatively complicated genetic background. Changes in the sites responsible for coding functional proteins in exon 1 and exon 4 of STK11/LKB1 may be one of the main causes of PJS. Mutation of the SLX4 gene may be a cause of genetic heterogeneity in PJS.

Comprehensive Study of Germline Mutations and Double-Hit Events in Esophageal Squamous Cell Cancer.

Esophageal squamous cell cancer (ESCC) is the eighth most common cancer around the world. Several reports have focused on somatic mutations and common germline mutations in ESCC. However, the contributions of pathogenic germline alterations in cancer susceptibility genes (CSGs), highly frequently mutated CSGs, and pathogenically mutated CSG-related pathways in ESCC remain unclear. We obtained data on 571 ESCC cases from public databases and East Asian from the 1000 Genomes Project database and the China Metabolic Analytics Project database to characterize pathogenic mutations. We detected 157 mutations in 75 CSGs, accounting for 25.0% (143/571) of ESCC cases. Six genes had more than five mutations: TP53 (n = 15 mutations), GJB2 (n = 8), BRCA2 (n = 6), RECQL4 (n = 6), MUTYH (n = 6), and PMS2 (n = 5). Our results identified significant differences in pathogenic germline mutations of TP53, BRCA2, and RECQL4 between the ESCC and control cohorts. Moreover, we identified 84 double-hit events (16 germline/somatic double-hit events and 68 somatic/somatic double-hit events) occurring in 18 tumor suppressor genes from 83 patients. Patients who had ESCC with germline/somatic double-hit events were diagnosed at younger ages than patients with the somatic/somatic double-hit events, though the correlation was not significant. Fanconi anemia was the most enriched pathway of pathogenically mutated CSGs, and it appeared to be a primary pathway for ESCC predisposition. The results of this study identified the underlying roles that pathogenic germline mutations in CSGs play in ESCC pathogenesis, increased our awareness about the genetic basis of ESCC, and provided suggestions for using highly mutated CSGs and double-hit features in the early discovery, prevention, and genetic counseling of ESCC.

Evaluating the clinical, environmental, genetic, and genomic profile of men with early-onset aggressive prostate cancer (PCa).

e17517 Background: Although PCa incidence has stabilized/decreased in most age groups, the incidence of metastatic disease has increased among men 50-69 years-old. The incidence of fatal PCa has decreased for most age groups, it has remained unchanged in men under 55 years-old. Studies have described genetic abnormalities in aggressive localized or end-stage PCa, but early-onset cases are not included or are under-represented. The primary objective of this study is to characterize the clinical, environmental, genetic and genomic features of high-risk advanced PCa. Methods: Study cohort includes men with PCa ≤ 60 years old with N1 or M1 stage at diagnosis or who develop metastases in 5-years after local therapy. Clinical (race, family history (Hx), environmental exposure), laboratory,/pathology, cell-free DNA germline analysis were collected. Primary/metastatic tumor tissue tested via the Tempus-Xe platform (DNA sequencing, whole transcriptome expression profiling, copy number analysis, comprehensive fusion gene analysis and calculation of tumor mutational burden). We report interim analysis. Results: Study completed accrual with 30 pts. Median age 55 years (41-60), 87% are white, 13% are black, 77% had a family Hx of malignancy in 1-6 family members, including 40% with family hx of PCa. Only 33% had Hx of smoking. Median Gleason score 9. Only 27% had nodal disease, and 73% had metastatic disease at diagnosis. Molecular data are available in 25 pts. Most common germline mutations: BRCA2 (12%), ATM (12%), RB1 (8%), MSH3 (8%) and MYBPC3 (8%). Most common somatic mutations:TP53 (40%), TMPRSS2-ERG fusion (32%), MUC4 (16%), PTEN (12%), C2CD4D (12%), SPOP (12%), OBSCN (12%), MXRA5 (12%), and MYO15A (12%). Microsatellite stability status was available in 15 pts and all were stable. Tumor mutational burden was low in all pts, ranging between 0.7 to 2.7 mutations/megabase. Conclusions: Our preliminary data suggest high rates of germline mutations in early onset lethal PCa. This aggressive subset of disease requires further studying to better characterize the underlying clinical/genomic factors driving this disease.

Hereditary Syndromes in Neuroendocrine Tumors.

Oncologists should be able to discern the salient clinical features of the most common germline mutations that give rise to neuroendocrine tumors. Astute recognition of an index patient affected by a hereditary syndrome can lead to a "tip-of-the-iceberg" phenomenon whereby their entire kindred can then be proactively monitored and managed potentially with substantial reduction of morbidity and mortality. Through careful history-taking, as well as thoughtful assimilation of findings from the physical exam, biochemical laboratories, scans, and pathology reports, the clinician can spot phenotypic clues that distinguish these familial patterns from sporadic cases of tumorigenesis.

Low Rates of Cascade Genetic Testing Among Families With Hereditary Gynecologic Cancer: An Opportunity to Improve Cancer Prevention

(Abstracted from Gynecol Oncol 2020;156:140–146) The 2 most common germline mutations causing cancer in the United States are BRCA1/2 mutations associated with hereditary breast and ovarian cancer (HBOC) and mismatch repair (MMR) gene mutations associated with Lynch syndrome (LS). A first-degree relative of a patient with one of these mutations incurs a 50% chance of inheriting the same mutation, and early detection can inform treatment and preventive procedures.

Changing the landscape of germline testing in patients with pancreatic adenocarcinoma.

676 Background: Results from the POLO trial demonstrated the benefits of PARP inhibition in patients (pts) with germline BRCA-mutated metastatic pancreatic cancer (PC). In 2018, ASCO and NCCN updated their guidelines to recommend that pts with a personal history of PC undergo germline testing. We examined referral patterns and frequency of germline pathogenic variants in pts with PC. Methods: A retrospective review was performed of PC pts seen at the Levine Cancer Institute (LCI) Center for Genetics between January 2010 and September 2019. Descriptive analyses were completed on demographics and appointment outcomes. Results: A total of 201 PC pts were referred; 20 canceled and 14 no-showed their appointment. The remaining 167 were seen and included in this analysis. Most pts (59%) were referred after July 2018. The median age was 65 years (range 32-90) and 19% were &lt; 50 years. The majority of pts were female (61%). Race was most often reported as white (72%) followed by black (20%). Reported family histories were as follows: 28 (17%) claimed at least one first-degree relative with PC; 54 (32%) claimed a first, second, or third-degree relative with PC; 24 (14%) had no known family history of PC; and 95 (57%) claimed a first-degree relative with another cancer (breast [37], prostate [25], colon [18], ovarian [9], uterine [6], and gastric [2]). Germline testing was pursued by 138 (83%) pts: 25 (18%) were found to have a pathogenic variant and 50 (36%) a variant of uncertain significance. Pathogenic variants were most commonly identified in ATM (24%), BRCA2 (20%), PALB2 (12%), and CDKN2A (8%). Variants were also observed in DIS3L2, HOXB13, MITF, MUTYH (heterozygote), NTHL1 (compound heterozygote), RAD50, PRSS1, and SDHA. Among pts that had a pathogenic variant, cascade testing was performed in 11 families (44%) for 29 individuals. Conclusions: Our data suggest that the referral of PC pts to genetics has increased following updated ASCO/NCCN guidelines. However, improved adherence to genetic counseling is needed. ATM and BRCA2 were the most common germline mutations observed. More effort to increase awareness of genetic testing and its potential implications for pts and their families is warranted and might reduce cancellations and missed visits.

An Integrative Genomic Approach to Examine Mutations and Biological Pathways Associated with Hematological Malignancy Development in DDX41 Mutated Families

DEAD-Box helicase 41 (DDX41) is one of the most commonly reported familial hematological malignancy (HM) genes, first reported in 2015. Mutated, it predisposes to both MDS/AML and lymphoma with an age of diagnosis similar to that of sporadic cases. Consequently, unrecognized DDX41 mutated cases are present in 'sporadic' cohorts with families often identified this way. Individuals with DDX41 mutation or deficiency have generally poor outcome with no effective targeted therapies available. The biological mechanism by which mutant DDX41 predisposes to HM is poorly understood making risk assessment for asymptomatic carriers difficult. In over 50% of HM affected individuals with germline DDX41 mutations, an acquired somatic mutation is identified on the other DDX41 allele with R525H being most common. Analysis of other somatic mutations in germline DDX41 mutation carriers reveals a minimal fingerprint of acquired somatic alterations in known myeloid malignancy driver genes with an absence of NPM1 and FLT3 mutations and an under-representation of mutations in DNMT3A, TET2, IDH1/2 and RUNX1. This may indicate a mechanism of leukemia development unique to germline DDX41 cases. Through an integrative combinatorial genomics approach of whole exome sequencing, leukemic panel sequencing and RNA-sequencing, we are in the process of comprehensively assessing six independent DDX41 germline mutated families. We and others have identified that DDX41 mutations are recurrently associated with MDS with erythroid dysplasia and erythroid subtype leukemia consistent with functional in vitro experiments showing that DDX41 mutations including loss-of-function can impact erythroid differentiation. Our preliminary RNA-Seq analysis on peripheral blood mononuclear cells of DDX41 carriers with HM reveals altered expression of genes involved in hemoglobin complex and innate immunity. DDX41 is reported to bind RNA splicing components such as SF3B1 and PRPF8 which are recurrently mutated in MDS/AML and intriguingly, the R525H mutation disrupts this interaction. Further analysis of our RNA-Seq data interrogating alternative splicing, gene expression analysis and biological pathways to uncover mechanisms for mutant DDX41 oncogenicity is currently ongoing. We have used CRISPR-Cas9 technology to generate Ddx41M1I mice as a model for one of the most common germline mutations in familial HM to investigate the direct effect of DDX41 mutation on hematopoiesis. Preliminary results indicate a sub-clinical reduction in hemoglobin levels in mice carrying the M1I mutation in heterozygosity when compared to their wildtype littermates. We are further investigating these mice with particular emphasis on characterizing hematopoiesis longitudinally to better understand mechanisms of disease onset and progression. This integrative genomic and functional approach to evaluate both mutations and biological pathways affected in DDX41 mutated malignancies will provide biological insight facilitating advancement in diagnosis, risk assessment, monitoring and personalized treatment. Disclosures Scott: Celgene: Honoraria.

826P - Identification of a spectrum of germline mutations for hereditary diffuse gastric cancer in the Russian population by next-generation sequencing

BackgroundGastric cancer is the fifth most common malignancy in the world and the third leading cause of cancer death. Approximately 1–3% of gastric cancers are hereditary. Mutations of CDH1,the gene encoding E-cadherin, are the most common germline mutations detected in gastric cancer and cause hereditary diffuse gastric cancer (HDGC) syndrome. However, there has been no research previously conducted to identify candidate genes for predisposition to hereditary gastric cancer in the Russian population. The purpose of our research was to fill this gap. MethodsFor this study, we collected specimens of the venous blood of 40 patients (age up to 50 years) diagnosed with diffuse gastric cancer, and 80 gastric cancer tumor samples. To define the mutation in these patients we have used NGS with two panels -an Ion AmpliSeq Cancer Hot spot Panel v2, widely used for the analysis of «hot spots» in cancer related genes, and an in-house panel developed for sequencing the genes involved in gastric carcinogenesis (BMPR1A, SMAD4, CDH1, TP53, STK11, PTEN). All found mutations were verified in DNA obtained from peripheral blood lymphocytes, using polymerase chain reaction followed by Sanger sequencing. ResultsIn total, with two panels, we have identified 16 genetic germline variants with exceptionally low general population frequencies (no higher than 0.00004 according to the gnomAD database), and 4 genetic variants that have never been reported previously. We detected 6 deleterious mutations in CDH1 gene. All found mutations were missense mutations (A2512G:p.S838G, c.G1234A:p.V412I,.G2635A:p.G879S, c.C8G:p.P3R, c.C670T:p.R224C). Among these 6 mutations, one (c.A907c:pT303P) was newly discovered in this study. Other deleterious germline variants were found in APC,CDKN2B, STK11, MET, SMO and two in RB1 genes. The mean age at diagnosis of gastric cancer patients with mutation was 46,1. ConclusionsIdentifying mutation carriers in families is extremely important. The identification of germline CDH1 mutations offers the opportunity for potentially lifesaving prophylactic gastrectomy, which is the standard of care for these individuals. Legal entity responsible for the studyThe authors. FundingRussian Foundation for Basic Research (project No. 18-015-00333), Russian Foundation for Basic Research (project No. 18-29-09020). DisclosureAll authors have declared no conflicts of interest.

MicroRNA-210 May Be a Preoperative Biomarker of Malignant Pheochromocytomas and Paragangliomas

BackgroundCurrently, no reliable predictive clinical or laboratory tests exist that can accurately distinguish between benign and malignant pheochromocytomas or paragangliomas (PPGLs). The aim of this study was to investigate if serum microRNA-210 (miR-210) levels could be a marker of malignancy in patients with PPGLs. MethodsPreoperative serum from patients with PPGLs was collected on the day of surgery. Clinical demographics, germline mutation status, primary tumor size, postoperative biochemical response, and the development of malignant disease were prospectively collected. Total microRNA was extracted from preoperative serum samples, and miR-210 levels were measured by quantitative real-time reverse transcription-polymerase chain reaction and normalized to miR-16. Prognostic variables were compared using univariable and multivariable analyses. ResultsOf the 35 patients, 10 (29%) were diagnosed with malignant PPGLs and 25 patients (71%) were diagnosed with benign PPGLs (median follow-up 72.5 mo). Sixty-nine percent of patients had a pheochromocytoma (n = 24/35) compared with 31% of patients with paraganglioma (n = 11/35). The most common germline mutation was succinate dehydrogenase complex subunit B (SDHB) (n = 10). On univariable analysis, lower serum miR-210 expression level (2.3 ± 0.5 versus 3.1 ± 1.2, P = 0.013) and larger primary tumor size (6.7 ± 5.0 cm versus 4.1 ± 2.3 cm, P = 0.043) were significantly associated with malignant disease. No significant prognostic variables were found on multivariable analysis. ConclusionsIn this pilot study, low serum miR-210 expression levels and large primary tumors were identified to be markers of PPGL malignancy on univariable analysis. Given the initial encouraging results in a small cohort, further investigation is warranted to determine if serum miR-210 levels are prognostic.

BRCA1/2 germline mutations and response to PARP inhibitor treatment in lung cancer.

e13007 Background: Germline mutations in BRCA1/2 (BReast CAncer genes 1 and 2), which are targets for PARP inhibitors in breast and ovarian cancer, have been previously identified in patients with non-small cell lung cancer (NSCLC). However, its prevalence and clinical outcomes to targeted therapy in NSCLC still remains unknown. Methods: We conducted a retrospective review of 9,324 Chinese NSCLC patients who underwent targeted next-generation sequencing (NGS) during 2015/11/01 and 2018/10/31. Patients with BRCA1/2 somatic and germline mutations were identified. We summarized their prevalence and explored their co-existing driver mutations. Then we initially reviewed the response to PARP-inhibitor targeted therapy in patient with BRCA2 germline mutation. Results: 459 (4.9%) patients are BRCA1/2 positive (germline/somatic mutation). Most patients are diagnosed with LUAD (372, 81.1%), with a median age of 63 years (range: 2-101). Slightly more male patients were carrying BRCA1/2 mutations (59.9%, 275 out of 459). The prevalence of BRCA1 and BRCA2 somatic mutations was similar (145, 1.56% vs. 169, 1.81%, p = 0.19). BRCA2 germline mutation was more common in lung cancer than BRCA1 germline mutation (148, 1.59% vs. 20, 0.21%, p &lt; 0.0001). When specified to the common driver gene mutation subgroups, the prevalence of BRCA2 germline mutation is similar to the entire population (EGFR 1.79%; ALK 1.74%; KRAS 2.05%; BRAF 2.86%; ERBB2 0.93%; p &gt; 0.05). K2729N is the most common BRCA2 germline mutation (41, 27.7%), followed by C315S (26, 17.6%), V2109I (12, 8.1%), R2108C (11, 7.4%), I2490T (10, 6.8%), T582P (5, 3.4%). About 20% patients with BRCA2 germline mutation carried at least one concomitant mutations of DNA repair genes, including MLH1, MLH3, MSH6, CHEK2, BARD1, BLM, BRCA1, MUTYH, RAD50, RECQL4 and XRCC1. One 56-year-old male LUAS patient, with germline BRCA2 rs80359490 frameshift deletion mutation (p.S1722Yfs*4), received the targeted therapy with PARP inhibitor Olaparib after multi lines therapies. This patient showed a great PR response to Olaparib, with a PFS of at least 6 months. Conclusions: BRCA1/2 germline mutations were rare in Chinese NSCLC patients. Patients with BRCA2 germline mutations might benefit from PARP-inhibitor treatment.

Evaluation of circulating tumor DNA (ctDNA) with respect to germline alterations in metastatic castrate resistant prostate cancer patients.

254 Background: Circulating tumor-derived DNA (ctDNA) is an accessible method for characterizing tumoral alterations. We report ctDNA screenings of mCRPC patients (pts) who have had germline testing. Methods: Guardant360 (Guardant Health, Inc.) assesses ctDNA using sequencing to identify genomic alterations in 73 cancer-related genes. Alterations were categorized by type which included amplifications, deletions, frameshift mutations, insertions, missense mutations, splice mutations, truncations, and other. A total of 186 PCa pts in various stages of therapy had both ctDNA and germline DNA tested. Results: Of the 186 pts tested for germline mutations, 26 (14%) were germline positive. The most common germline mutation was BRCA2 with 12 (46%) pts, followed by ATM with 3 (11%). Of the total gene alterations were detected on ctDNA analysis of germline positive pts, with the most common genes being TP53 (n = 14/73, 19%), NF1 (n = 6/73, 8%), PIK3CA (n = 6/73, 8%), and BRCA2 (n = 5/73, 7%). Of the total gene alteration were detected on ctDNA analysis of germline negative pts, with the most common genes being TP53 (n = 94/588, 16%), AR (n = 90/588, 15%), EGFR (n = 31/588, 5%), and BRAF (n = 29/588, 5%). Germline negative pts showed had more amplifications (p = 0.008) while germline positive patients had more frameshift mutations (p = 0.025). Other alterations (deletion, missense, insertion, other, splicing, and truncating) were not significantly different. Missense mutations were the most prevalent type of gene alteration in germline negative (n = 306/609, 44%) and germline positive (n = 45/77, 48%), followed by amplifications (n = 210/609, 25% germline negative and n = 15/45, 18% germline positive). The median percent ctDNA values for missense mutations in germline negative and positive patients were 0.5% and 0.3% respectively. Of the germline positive pts, BRCA2 mutation was associated with the highest number of genes with alterations (n = 39), followed by RECQL4 (n = 8), ATM (n = 5), and MSH2 (n = 5). Conclusions: Germline positive pts had a higher number of frameshift mutations compared to germline negative pts. Additionally, pts with BRCA2 had the highest number of genes altered in ctDNA.