Background: This study is a first attempt to determine frequency of gBRCAm and share of sBRCAm in Russian ovarian cancer (OC) cancer patients (pts) using next-generation sequencing (NGS) and multiplex ligation-dependent probe amplification (MLPA). Russian population is known to have a sizable proportion of “frequent” germline mutations in BRCA genes, with occurrence in >2% of all BRCAm cases. Methods: 498 pts with primary serous and endometrioid OC were enrolled in noninterventional study OVATAR (NCT02122588). NGS testing of BRCAm in genomic DNA (gDNA) from leukocytes and primary tumor tissue was performed. MLPA assay for large rearrangements (LGR) was used on gDNA from leukocytes. Results: Interim analysis includes pairs of tumor and blood samples from 400 pts. The total rate of BRCA1/2 mutations was 35% (140/400 pts) including 29.8% (119/400) of germline mutations (gBRCAm) and 5.2% (21/400) of somatic mutations. Alterations reported hereby were either classified as deleterious/pathogenic in public databases, or identified as “likely pathogenic” (e.g., loss-of-function). VUS were not included. Frequent gBRCAm were detected in 49.3% of gBRCAm cases (69/140). BRCAm were counted as rare: in 30.7% (43/140) pts, including LGR in 3.6% (5/140) pts. sBRCAm: in 15% (21/140) pts. Although previously counted as frequent, 6174delT in BRCA2 was not detected. 4 pts carried pathogenic germline BRCA2 c.T5286G:p.Y1762* nonsense mutation, with prevalence 2.9% among BRCAm carriers, which makes it the new and only potential “hot-spot” in BRCA2 gene. Large deletions comprise 5% of all BRCAm and mostly occur in BRCA1 gene. Conclusion: The overall rate of both somatic and germline BRCA variations in Russian OC population is in line with global data, with high percent of 8 frequent gBRCAm (49.3%). Use of MLPA is limited by blood samples with low rate of germline LGR. NGS is becoming a method of choice to hit both small variations and LGR in BRCA genes. gene/mutation# of pts (n=140) and % of BRCAmgBRCAmFrequent mutations n=69 (49,3%)BRCA15382insC3726,4%4154delA75,0%2080delA64,3%C61G53,6%185delAG42,9%3819del532,1%3875del432,1%BRCA2T5286G (c.T5286G:p.Y1762*)42,9%Rare mutations n=43 (30,7%)BRCA12417,1%BRCA21913,6%Exons deletions n=7 (5%)BRCA164,3%BRCA210,7%sBRCAmn=21 (15%)BRCA1139,3%BRCA285,7% Citation Format: Alexandra Tyulyandina, Vera Gorbunova, Svetlana Khokhlova, Larisa Kolomiets, Maksim Filipenko, Evgeny Imyanitov, Irina Demidova, Yuri Moliaka, Nadezhda Cherdyntseva, Dmitriy Vodolajskiy, Ludmila Lyubchenko, Sergei Tjulandin, Ilya Tsimafeyeu, Olga Vedrova, Vera Karaseva, Sergei Andreev, Tatiana Kekeeva. Profile of BRCA1/BRCA2 mutations in Russian ovarian cancer population detected by NGS and MLPA analysis: Interim results of OVATAR study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1241.

SUMMARY Microenvironmental factors modulating age-related DNA damage are unclear. Non-pituitary growth hormone (npGH) is induced in human colon, non-transformed human colon cells, and fibroblasts, and in 3-dimensional intestinal organoids with age-associated DNA damage. Autocrine/paracrine npGH suppresses p53 and attenuates DNA damage response (DDR) by inducing TRIM29 and reducing ATM phosphorylation, leading to reduced DNA repair and DNA damage accumulation. Organoids cultured up to 4 months exhibit aging markers, p16, and SA-β-galactosidase and decreased telomere length, as well as DNA damage accumulation, with increased npGH, suppressed p53, and attenuated DDR. Suppressing GH in aged organoids increases p53 and decreases DNA damage. WT mice exhibit age-dependent colon DNA damage accumulation, while in aged mice devoid of colon GH signaling, DNA damage remains low, with elevated p53. As age-associated npGH induction enables a pro-proliferative microenvironment, abrogating npGH signaling could be targeted as anti-aging therapy by impeding DNA damage and age-related pathologies.

Deregulation of receptor tyrosine kinase (RTK)-signaling is frequently observed in many human malignancies, making activated RTKs the promising therapeutic targets. In particular, activated RTK-signaling has a strong impact on tumor resistance to various DNA damaging agents, e.g., ionizing radiation and chemotherapeutic drugs. We showed recently that fibroblast growth factor receptor (FGFR)-signaling might be hyperactivated in imatinib (IM)-resistant gastrointestinal stromal tumors (GIST) and inhibition of this pathway sensitized tumor cells to the low doses of chemotherapeutic agents, such as topoisomerase II inhibitors. Here, we report that inhibition of FGFR-signaling in GISTs attenuates the repair of DNA double-strand breaks (DSBs), which was evidenced by the delay in γ-H2AX decline after doxorubicin (Dox)-induced DNA damage. A single-cell gel electrophoresis (Comet assay) data showed an increase of tail moment in Dox-treated GIST cells cultured in presence of BGJ398, a selective FGFR1-4 inhibitor, thereby revealing the attenuated DNA repair. By utilizing GFP-based reporter constructs to assess the efficiency of DSBs repair via homologous recombination (HR) and non-homologous end-joining (NHEJ), we found for the first time that FGFR inhibition in GISTs attenuated the homology-mediated DNA repair. Of note, FGFR inhibition/depletion did not reduce the number of BrdU and phospho-RPA foci in Dox-treated cells, suggesting that inhibition of FGFR-signaling has no impact on the processing of DSBs. In contrast, the number of Dox-induced Rad51 foci were decreased when FGFR2-mediated signaling was interrupted/inhibited by siRNA FGFR2 or BGJ398. Moreover, Rad51 and -H2AX foci were mislocalized in FGFR-inhibited GIST and the amount of Rad51 was substantially decreased in -H2AX-immunoprecipitated complexes, thereby illustrating the defect of Rad51 recombinase loading to the Dox-induced DSBs. Finally, as a result of the impaired homology-mediated DNA repair, the increased numbers of hypodiploid (i.e., apoptotic) cells were observed in FGFR2-inhibited GISTs after Dox treatment. Collectively, our data illustrates for the first time that inhibition of FGF-signaling in IM-resistant GIST interferes with the efficiency of DDR signaling and attenuates the homology-mediated DNA repair, thus providing the molecular mechanism of GIST’s sensitization to DNA damaging agents, e.g., DNA-topoisomerase II inhibitors.

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e13111 Background: First large Russian ovarian cancer observational study was conducted in 2014-2018. Methods: A total of 500 patients in 29 sites in Russia with newly diagnosed ovarian, peritoneal and fallopian tube cancer was enrolled (NCT02122588). The primary objective was to describe treatment approaches in the first line treatment. 141 patients (pts) with BRCA1/2 mutations (BRCA1/2mt) detected by NGS in blood and tissue were observed prospectively during at least 2 years. Results: Rate of BRCA1/2 mutations in Russian population is high – 28.4% (141 from 496 available for any testing). 77.6% (388/500) underwent biomarkers blood testing prior to treatment. CA-125 was positive in 99.7% (387/388), 15.2% (59/388) of pts had positive CA19-9, CA72-4 - in 2.3% (9/388). Positive CEA was presented in 15.2% (59/388). This marker was detected more frequently in BRCA2mt pts subgroup (28.0% (7/25)) than in BRCA1mt pts: 9.0% (8/90) (p = 0.05). 26.6% (133/500) of all study population had an oncology family history; 44.0% (62/141) BRCA1/2mt pts had relatives with oncological diseases and 19.7% (70/355) in BRCA wild type pts (p = 0.0001). 98.6% (139/141) of BRCA1/2mt pts received first line therapy. Objective response rate was registered in 79.8% (111/139) pts. Progression after platinum based regimens was observed in 53.6% (59/110) BRCA1mt pts and 44.8% (13/29) BRCA2mt pts. 35.6 % (21/59) of BRCA1mt pts had platinum-refractory and platinum-resistant relapses, while 15.4% in BRCA2mt subgroup (2/13) (p = 0.64). Platinum-sensitive relapses were in 64.4% (38/59) BRCA1mt pts and 84.6% BRCA2mt (11/13) (p = 0,64). Median PFS in BRCA1/2mt pts was 25.5 months. Among BRCA1/2mt pts underwent cytoreduction median PFS in subgroup without visible residual tumor was 36.4 months and in subgroup with residual tumor < 1 cm 15.3 months. Conclusions: In this large-scale prospective non-interventional study diagnostics and treatment approaches in Russian ovarian cancer pts were evaluated and high frequency of BRCA1/2mt was observed. Pts with BRCA1/2mt had better prognosis and most of them had platinum-sensitive relapses after first line chemotherapy that allowed platinum-based regimen rechallenge.