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Genetic information, both inherited and tumor-specific, is becoming an increasingly important factor in the implementation of therapeutic strategies in oncology, providing an individual approach to each patient. Every year, an increasing number of achievements in medical genetics are introduced into oncological practice in the form of laboratory tests, diagnostic panels and practical recommendations. The article provides a brief overview of the results of genetic studies performed at the Federal National Medical Research Centre for Oncology of the Ministry of Health of the Russian Federation from the beginning of their implementation in 2013 to the present day. We have demonstrated not only testing data within the framework of clinical recommendations, but also an analysis of the search for new genetic, epigenetic and proteomic markers, which seem promising for the development of new target drugs, diagnostic and prognostic test systems. We believe that the model of interaction between a researcher and an oncologist used in our center allows us to shorten the path from a scientific hypothesis to the creation and implementation of innovative technologies.

Glial tumors, in particular those composed of astrocytes, are the most common group of primary brain tumors. The most common glial tumor is astrocytoma. The biology of glial tumors was routinely studied on immortalized cell lines. However, multiple passages result in a loss of cellular heterogeneity. Therefore, more and more scientific laboratories in their research are beginning to use primary cell lines obtained directly from the patient’s native postoperative material. The question of the timing of the genetic stability of primary cell lines remains open. A special type of genetic instability is microsatellite instability, which affects microsatellites found throughout the genome. Microsatellites have several alleles, which are determined by changes in the number of repetitions of a motif unit. Microsatellite instability is of great importance in the oncogenesis of malignant neoplasms. The aim of this work was to study the microsatellite instability of primary cell lines of poorly differentiated glial tumors at different passages in comparison with the patient’s primary tumor material. Tumor cells of primary cultures of anaplastic astrocytoma and glioblastoma at different passages were used as material for the study. Formalin-fixed paraffin wax (FFPE) slides were used as a microsatellite control. Microsatellite analysis was performed on primary cultures of anaplastic astrocytoma and glioblastoma using the following markers: D17S250, D2S123, D5S346, NR21, NR24, NR27, BAT25, BAT26 by PCR. Microsatellite analysis has shown that primary glioblastoma cell lines are genetically more stable than primary anaplastic astrocytoma cell lines.

Neuroendocrine tumors (NETs) account for less than 3% of primary neoplasias of the pancreas. Despite success of the classification, the discovery of new methods of treatment, and innovations in the field of visualization, non-aeroendocrine neoplasms remain a clinically complex object, which is associated, among other things, with the lack of effective biomarkers for early diagnosis and monitoring of the course of the disease. This review is devoted to the analysis of current data on the molecular genetic features of pancreatic neuroendocrine tumors, taking into account the current WHO classification. The signaling pathways and individual markers that are being developed for the typing of NETs, the prognosis of the course of the disease, and the identification of potential targets for targeted therapy are discussed. The molecular bases of hereditary syndromes, which are associated with the development of NETs, are considered.

The association of genetic driver changes in gastrointestinal stromal tumors (GIST) with clinical implications is the most studied aspect in all solid tumors. Genotyping of particular exons c-KIT and PDGFRA included in the standard practice of diagnosis and treatment of GIST. The review analyzes the current understanding of the molecular-genetic mechanisms and markers that underlie the GIST profiling. Of particular interest are wild-type tumors of c-KIT and PDGFRA, in which activating mutations of the RAS, BRAF and EGFR oncogenes are found, associated with the early stages of disease progression. The data of studies of genetic and epigenetic changes in GIST, which revealed the prognostic value of inactivation of CDKN2A and p53, deletions of 22q, 1p and 15q, CpG hypermethylation are presented. New factors that determine a high risk of progression of GISTs are described: inactivation of dystrophin, DNA hypomethylation, increased expression of miRNAs and HOTAIR. The progress achieved in understanding the molecular mechanisms of GISTs give the opportunity of developing and effectively applying new therapeutic approaches, expanding the range of molecular genetic markers that determine patient surveillance.

Poor resource support of the pathoanatomical service, a lack of training of medical and nursing staff, poor results of pathological and anatomical research, and personnel shortage in some territories and republics of the country have been observed for more than 30 years. The reference centers organized in 2019 will contribute to the centralization of the pathoanatomical service and improve its work in general, which will lead to more efficient use of medical personnel due to the load streamlining, interchangeability, automation of manual labor, and complete and rational use of equipment, as well as will shorten the time for surgical and biopsy material testing.

e19580 Background: Many studies have been devoted to the molecular profile of diffuse large B-cell lymphoma; however, a clear molecular and genetic picture of primary mediastinal large B-cell lymphoma (PMBLC) has not yet been described. Studies have reported various signaling pathways involved in PMBCL pathogenesis, with the best known JAK-STAT and NF-kB. This study was aimed at the detection of previously undescribed mutations, as well as the identification of signaling pathways that may be of interest in the search for new therapeutic targets for PMBCL. Methods: Tumor biopsy specimens from 23 PMBCL patients were examined by next-generation sequencing (NGS) on the Illumina NextSeq 550 system with an average coverage of at least 100x using the AVENIO Tumor Expanded Panel (Roche, USA) containing 77 genes. Analytical sensitivity of mutation detection was 5%. The pathogenicity of the identified nucleotide substitutions was assessed according to ACMG (American College of Medical Genetics and Genomics) and AMP (Association of Molecular Pathology) recommendations. Genomic DNAs were extracted from FFPE blocks using the Gene Read DNA FFPE Kit panel (Qiagen, USA) according to the standard protocol. DNA concentrations were measured fluorimetrically on the Qubit 2.0 fluorometer (Life Technologies, USA). The AVENIO Oncology Analysis Software was used to process the data and to search for clinically significant mutations. The genetic material was analyzed for clinically significant mutations among well-known databases: COSMIC: V83, TCGA 9.0, Exac: 1.0, DBSNP: 150, 1000 Genomes: phase_3_v5b, Snpeff: 4.2. Results: The targeted high-performance sequencing of PMBLC samples showed a newly revealed range of polymorphisms in 9 genes in patients with PMBLC (Alk, TP53, CCND3, RNF43, PIK3CA, FGFR3, SMO, MET, EZH2), previously not described for this cancer. We also interpreted signal pathways related to the mutated genes. Conclusions: The identified polymorphisms and the relationship of mutated genes with PMBLC signaling paths can serve as new therapeutic targets for patients with PMBLC.

12076 Background: Numerous pharmacogenetic studies have identified genetic polymorphisms (SNPs) associated with an increased risk of anthracycline-mediated cardiotoxicity (AMC). The purpose was to search for SNP-SNP interactions associated with the risk of cardiotoxic manifestations caused by anthracycline therapy in breast cancer patients. Methods: The study included 256 Caucasian patients (median age - 55 years) with a diagnosis of breast cancer with normal cardiovascular system parameters at baseline, who were treated with anthracyclines in 2019-2020. For SNP genotyping of c.4544G > A rs8187710 (ABCC2), c.1744C > T rs11549465 ( HIF1A), g.22125504G > C rs1333049 ( CDKN2A/ B) and c.214T > C rs4673 ( CYBA). DNA was extracted from blood by using DNA-sorb-B (AmpliSens, Russia). HRM-PCR was performed on a CFX96 amplifier (Bio-Rad, USA). The presence of polymorphism was confirmed by the Sanger method on a Genetic Analyzer 3500 (ABI, USA). Results: During the follow-up period 21 (8.2%) patients developed signs of subacute (changes developed within several weeks after the last course of therapy) or early chronic anthracycline mediated cardiotoxicity (changes developed within a year after completion of anthracycline therapy). Using the multifactorial dimension reduction method. We obtained a 4-locus model of SNP-SNP interactions c.4544G > A rs8187710 ( ABCC2) x g.22125504G > C rs1333049 ( CDKN2A/B) x c.214T > C rs4673 ( CYBA) x g.23708527G > A rs28714259 which has high prognostic properties. The specificity of the test based on the 4-locus model was 68%, the sensitivity was 100%, and the overall accuracy was 71%. The results of the analysis of SNP-SNP interactions indicate the greatest contribution of rs4673 and rs28714259 to the predisposition to AMC. The first ones yet into antagonistic interactions with rs28714259, rs1333049 and rs11549465, the second with rs8187710, rs11549465 and rs4673. On the contrary rs11549465 and rs1333049 contribute to a synergistic effect. Conclusions: The 4-locus model discovered in this study can form the basis of prognostic tests that predict early the risks of developing AMC in cancer patients, which in the future allow to personalize and select the most optimal treatment regimen.

e20514 Background: Non-small cell lung cancer (NSCLC) accounts for 85% of all lung cancers and remains the most commonly diagnosed human neoplasm with a poor prognosis. Significantly improving the clinical course of NSCLC, EGFR tyrosine kinase inhibitors are effective only against tumors carrying activating mutations in the EGFR gene, and their frequency varies depending on the patient population. The aim of the study was to analyze a retrospective group of Crimean patients with advanced NSCLC for the presence of EGFR gene aberrations and association with clinical outcome. Methods: We used DNA samples from FFPE blocks of tumor and non-tumor tissues of 72 European-type patients (aged 46-78 years, median 64 years, 82% - men, 18% - women) diagnosed with lung cancer (T1-1aN0-2M0-1, stage I-IV). The relative copy number of the EGFR gene was assessed by RT-qPCR using GAPDH and B2M as reference genes. Mutations (9 deletions in exon 19, L858R, T790M, L861Q, G719S/A/C, 3 insertions in exon 20, S768I) in the EGFR gene were determined using the Therascreen EGFR RGQ PCR Kit (Qiagen, Germany). Results: For Crimean population patients, the squamous subtype of NSCLC was more common (57%). EGFR copy number evaluation in patients with adenocarcinoma showed locus amplification in 9 patients (30%), no loss of copy number was recorded. In the squamous cell carcinoma group, locus amplification prevailed in 25 of 42 samples (59.6%) and a decrease in copy number was noted in 4 samples (9.5%). Differences in the frequency of aberrant changes in the relative copy number of EGFR in adenocarcinoma and squamous cell lung cancer groups were statistically significant (χ2 = 11.04 at p = 0.003). The activating mutation frequency in adenocarcinoma samples was 9.7% (ex19del), which was lower than the frequency recorded in European adenocarcinoma patient populations (14.4%, p = 0.036). No EGFR mutations were found in cases of squamous cell lung cancer. The presence of mutations and/or changes in EGFR copy number were associated with shorter overall survival in patients who did not receive targeted and immune therapy (p = 0.034). Conclusions: The ex19del activating mutation of the EGFR gene frequency in adenocarcinoma samples was 9.7%. A more frequent EGFR alteration was detected when assessing the locus copy number in the tumor relative to the non-tumor tissue: changes were recorded for 30% of adenocarcinoma cases and 69.1% of squamous cell lung cancer.

12077 Background: Anthracyclines are highly effective chemotherapeutic agents, used for a wide variety of malignancies. Despite their antitumor efficacy there is a risk of cardiotoxic manifestations that reduce the time and quality of life of patients. The purpose was to study the effectiveness of molecular genetic tests based on rs4673 CYBA genotyping (c.242C > T) and measurement of plasma paraoxonase 1 (PON1) level in patients with breast cancer (BC) for predicting and diagnosing anthracycline-mediated cardiotoxicity (AMC). Methods: The study included 256 Caucasian patients (median age - 55 years) with a diagnosis of breast cancer normal cardiovascular system parameters at baseline, who were treated with anthracyclines in 2019-2020. For rs4673 genotyping, DNA was extracted from the blood by using DNA-sorb-B (AmpliSens, Russia). HRM-PCR was performed on a CFX96 amplifier (Bio-Rad, USA). The presence of polymorphism was confirmed by the Sanger method on a Genetic Analyzer 3500 (ABI, USA). The concentration of PON1 in blood plasma was measured at baseline and after 4 course of chemotherapy with anthracyclines using ELISA kits (Cloud-Clone Corp., China/USA). Results: During the follow-up period 21 (8.2%) patients developed signs of subacute (changes developed within several weeks after the last course of therapy) or early chronic AMC (changes developed within a year after completion of anthracycline therapy). In the group of patients without AMC the frequency of the minor allele rs4673 (c.214C > T CYBA) was 0.38, the frequency of genotypes C/C was 0.4, C/T - 0.43, and T/T - 0.17. The risk of AMC increased by 6.49 times in the presence of the rs4673 polymorphic allele (p = 0.002). The area under the ROC curve of the test based on rs4673 genotyping was 71.9%. The concentration of PON1 after the 4 courses of chemotherapy increased by 19.57% in the group of patients without cardiotoxic manifestations (p = 0.018) and in the group of patients with AMC by 20.23% (p = 0.007) as compared to the initial level. Besides, after 4 courses of chemotherapy the PON1 level was higher in patients with AMC by 25.08% (p = 0.026) than in patients without cardiovascular complications. The sensitivity of the test based on the measurement of the PON1 level in the blood plasma after 4 courses of chemotherapy was 100%, the specificity was 70.8% with a cut-off value of 2.9 ng/ml. Conclusions: This study has showed that genotyping of patients for the rs4673 polymorphism allows pre-stratification of the risk group white determination of the PON1 level in blood plasma after 4 courses of chemotherapy gives the opportunity to identify patients with AMC and promptly correct the chosen treatment.

e17548 Background: About 10-15% of malignant ovarian tumors (OC) are associated with hereditary diseases, and about 65-85% of hereditary OC have a mutation in BRCA1/2 genes. The aim of the study was to analyze BRCA1/2 genes hereditary mutation spectrum in patients in the South of Russia diagnosed with OC. Methods: We used EDTA venous blood and FFPE-blocks of 324 patients with histologically verified epithelial OC (T1-3cNx-1Mx-1, stage I-IV). BRCA1 gene mutations (185delAG, 300T > C, 2080delA, 4153delA, 5382insC, 3819delGTAAA, 3875delGTCT) and BRCA2 gene mutations (6174delT) were determined by real-time PCR. Results: The most common types of OC were poorly differentiated serous carcinoma (high degree of malignancy) - 75.6%, well-differentiated serous carcinoma (low degree of malignancy) - 13%, mucinous tumors - 2.8%, endometrioid tumors - 4.3%, clear cell adenocarcinomas - 4.3%. BRCA1/2 genes mutations were found in 52 (16%) patients with OC. The frequency of detected BRCA1/2 genes mutations was: 5382insC - 53.8%, 4153 delA - 9.6%, 300T > G - 21.2%, 2080delA - 7.7%, 185delAG - 3.8%, 6174delT - 3.8%. 3819delGTAAA and 3875delGTCT mutations were not found in the BRCA1 gene. All carriers were confirmed to have the same mutations in the tumor. There were no cases of sporadic changes in BRCA1/2. BRCA1 mutation carriers prevailed in the group of high-grade serous carcinoma patients (11.1%), where all cases of BRCA2 gene mutations were identified. In the group of low-grade serous carcinoma patients, the mutation rate was 1.5%, in the endometrioid adenocarcinomas group - 0.6%, in the mixed epithelial tumors group - 2.8%. In the group of patients with mucinous tumors, mutations were not detected. Conclusions: Thus, frequency of BRCA1/2 gene mutations in OC patients living in the South of Russia was 16.0%. Distribution of mutation types in the BRCA1 gene, with a predominance of 5382insC (53.8%) and 300T > G (21.2%), corresponded to their occurrence ratio in the European populations. BRCA1/2 gene mutations were registered more often in the group of high-grade serous carcinoma patients.

e15500 Background: The immune response plays a key role in the oncogenesis of colorectal cancer. The heterogeneity of the tumor environment determines the need for immunogenetic profiling to identify associations with the implementation of tumor-specific immune responses in colorectal cancer. The purpose of our study was to describe the expression profiles of miRNAs and genes involved in the regulation of the immune response in colorectal cancer. Methods: The study included 18 patients (median age 66 years) diagnosed with colorectal cancer who were treated at the National Medical Research Centre for Oncology in 2018-2019. Total RNA was isolated using TRIzol (Thermo Fisher, USA) followed by treatment with DNase 1 (ThermoFisher, USA). Sequencing of RNA samples was performed using two approaches: AmpliSeq for Illumina Immune Response Panel (Illumina, USA) and TruSeq Small RNA Library Prep Kit -Set A (Illumina, USA) according to the manufacturer's instructions on a NextSeq 550 device (llumina, USA). Results: The study revealed 168 differentially expressed genes and 46 differentially expressed miRNAs (p < 0.05). 29 miRNA-mRNA pairs were identified. It has been established that the key signaling mechanism involved in the regulation of the tumor-specific immune response is chemokine signaling pathway (hsa04062). Expression of the CXCL1 and CXCL10 genes encoding the chemokines of the same name is increased in tumor cells (logFC = 1.51, p = 0.006 and logFC = 2.67, p < 0.001, respectively). At the same time, the level of hsa-miR-30a-5p and hsa-miR-99b-5p, which negatively regulate the expression of CXCL1 and CXCL10, is decreased (logFC = -2.26, p < 0.001 and logFC = -1.57, p < 0.001). Conclusions: Activation of expression CXCL1 and CXCL10 with simultaneous loss of negative regulators hsa-miR-30a-5p and hsa-miR-99b-5p was determined in colorectal tumors by NGS-sequencing, which seems promising for the development of personalized therapy, based on the immunogenetic features of colon tumors.

e16196 Background: Microsatellite instability (MSI), as an acquired feature of malignant tumors, is a predictive and prognostic marker. The less aggressive nature of MSI-positive tumors has been associated with high immunogenicity. In the present study, MSI was assessed in NET samples of different localizations. Methods: The sample included 50 patients with a diagnosis of pancreatic NET (G1-G3) and NET of colon (G2-G3). MSI was analyzed by fragment analysis of five microsatellite loci (Bat25, Bat26, NR21, NR24, NR27). The level of MLH1 methylation was detected by pyrosequencing. Results: MSI was noted in 25.8% cases of the NET of colon and in 13.3% cases of the NET of the pancreas. In the case of pancreatic NET, only MSI low level was identified (instability at 1/5 loci), while in the case of NET of colon, most cases were classified as MSI high level. The incidence of MSI of pancreatic NET was consistent with literature data for small intestinal NET (14%), unlike MSI NET and BRAF V600 mutated adenocarcinomas of colon, MSI-positive pancreatic NET were not associated with hypermethylation of the MLH1 promoter. MSI was more often detected in women over 60 years old, at stages of the tumor process without distant metastases (p = 0.49). The sample size did not allow us to determine significant differences in the studied clinical and pathological groups of NETs, however, we note that in all cases of an unfavorable course of the disease (progression, death), was noted MSS status of tumors. Conclusions: Thus, MSI-positive NET of colon resembles MSI-positive adenocarcinomas of colon in frequency and pathogenetic mechanisms, while in terms of the identified frequency of MSI in pancreatic NET resembles the NET of the small intestine.

e14027 Background: The existing modern standards of combination treatment of HGG patients do not provide recovery and a long-term favorable prognosis, and the increasong incidence of HGG determines the need for additional effective technologies for anticancer and decongestant therapy. One of such methods involves TMS, and we have reported its preliminary assessment earlier (DOI: 10.1200/JCO.2020.38.15_suppl.2545). In this study, we continued the observation to examine the survival of patients. Methods: Patients with HGG received combination treatment: stage 1 – surgical removal of tumors within visible unaltered tissues; stage 2 – radiation therapy (the Varian Novalis linear accelerator) to the bed of the removed tumor, single boost dose 2 Gy, total boost dose 60 Gy; stage 3 – multi-course chemotherapy: temozolomide 150 mg/m² on days 1-5 with a 23-day interval. Starting from the second day after surgery, patients of group 1 (n = 25) received 10 TMS sessions, and during radiotherapy – 15 TMS sessions. Patients of group 2 (n = 25) received combination treatment without TMS. 6 and 12 months after the surgery, survival of patients was assessed with the Kaplan-Meier method and the Log-Rank test. Results: After 6 months of the follow-up, the survival of patients in group 1 remained at 100%, while in the control group it decreased to 88.8±8.7%. The difference in the 1-year overall survival was even more pronounced: in group 1, it was 68.5±10.4%, exceeding the value in group 2 (52.0±7.5%.) The differences were statistically significant (Log-Rank test p = 0.001). Conclusions: The results confirm the effectiveness of accompanying TMS in the early postoperative period, as well as at the stage of radiation therapy. The undoubted effectiveness of the considered techniques makes it expedient to include this type of treatment in the combination therapy for HGG patients. The reported study was funded by RFBR, project number № 19-315-90082\19.

e15549 Background: Role of metastasectomy in pts with mBRAF metastatic CRC is still controversial. We performed analysis of prospective multicentric database of pts with mBRAF mCRC to evaluate the efficacy of metastasectomy in such group of pts in the real clinical practice. Methods: We analyzed a database of pts with mCRC in 7 cancer clinics in Russia and chose pts with metastasectomy with different mutational status. The primary endpoints were disease free survival (DFS) and overall survival (OS), which were calculated from the time of metastasectomy. Analysis was performed with the SPSS v.20 software package. Results: The study included 126 pts: 26 pts with mBRAF, 57 pts with mRAS and 43 pts with wtRAS/BRAF. Pts with mBRAF more often had synchronous metastases (50%/19,3/11,6%, p

e16197 Background: Aberrant DNA methylation is a characteristic feature of cancer, affecting gene expression and tumor phenotype. In this study, we quantified the methylation of promoters of eight tumor suppressor genes in pancreatic neuroendocrine tumors (Pan-NET). Methods: The method of pyrosequencing was used to quantity level (Met,%) of methylation of gene promoters - tumor suppressors AHRR, APC1A, DAPK, MGMT, MLH1, P16, RASSF1A, RUNX3 in tumor samples from 55 patients with pancreatic NET (G1-G3) and in the blood of 10 healthy donors. Met for each sample was calculated as the median methylation of CpG sites in triplicate. Results: Hypermethylation was observed for AHRR (75%), APC1A (25%), RASSF1A (30%). In contrast, DAPK, MGMT, MLH1, P16, RUNX3 had low methylation levels ( < 20%). The median of methylation in the blood of healthy donors for AHRR was 91% (76-98); for all other loci it did not exceed 6%. A high incidence of methylation in excess of blood levels in healthy donors was identified for RASSF1A (0.96); AHRR (0.75); MGMT (0.65); RUNX3 (0.41), APC1A (0.25). For tumor suppressor P16, only one case of increased methylation was recorded (Met = 15%), despite the fact that this phenomenon is not uncommon for NETs of other localizations. In 66% of pancreatic NET cases, hypermethylation of more than two promoters of tumor suppressor genes was noted. An association tendency was found between the presence of MEN1 mutations and the RASSF1A methylation level (p = 0.08). Correlation analysis revealed a significant level of negative association between changes in methylation of MLH1 and AHRR (p < 0.01); for the latter, the prognostic value of a high methylation status and a better prognosis for many malignant neoplasms were described. Conclusions: In the present study, significant methylation of the promoters of the APC1A, DAPK, MGMT, RASSF1A, and RUNX3 genes in well-differentiated pancreatic NETs was identified with a high frequency. At the same time, isolated cases of hypermethylation were noted for the well-known tumor suppressors MLH1 and P16.

12005 Background: Numerous pharmacogenetic studies have led to the identification of genetic polymorphisms associated not only with the development of cardiovascular disease, but also increase the risk of complications due to the use of anthracycline drugs, widely used in the treatment of cancer. The purpose of this study was to study the frequency of rs4673 and rs28714259 and possible associations with the risk of cardiovascular changes in patients with breast cancer during anthracycline therapy (anthracycline-mediated cardiotoxicity — AMC). Methods: The study included 256 Caucasian patients (median age - 55 years) with a diagnosis of breast cancer without diagnosed cardiovascular changes, who were treated with anthracyclines at the National Medical Research Center of Oncology in 2019-2020. For genotyping of rs4673 and rs28714259, DNA was extracted from blood using DNA-sorb-B (AmpliSens, Russia) and HRM-PCR was performed on a CFX96 amplifier (Bio-Rad, USA). The presence of polymorphisms was confirmed by Sanger sequencing on a Genetic Analyzer 3500 (ABI, USA). Results: During the follow-up period 21 (8.2%) patients were diagnosed with signs of subacute (changes developed within several weeks after the last course of therapy) or early chronic AMC (changes developed within a year after completion of anthracycline therapy). In the group of patients without AOC the allelic frequency of rs4673 (c.214T > C CYBA) was 0.38, the frequency of genotypes C/C – 0.4, C/T – 0.43, and T/T – 0.17. In the same group, the frequency of the A allele rs28714259 was 0.07, the frequency of the G/G genotypes – 0.87, G/A – 0.13, and A/A – 0. The prevalence of genotypes T/T rs4673 and allele G rs28714259 in a cohort of Russian patients differed from the European population (p = 0.014 and p = 0.05, respectively). The risk of cardiovascular changes on the background of anthracycline therapy increased in the presence of the rs4673 polymorphic allele by 6.49 times, in the case of the G/A and A/A rs28714259 genotypes - by 3.27 times. The results of the ROC-analysis suggested high quality of the tests based on the dominant models rs4673 and rs28714259 (AUC was 71.9% and 76.3% correspondingly). Conclusions: In this study the prognostic efficiency of the genetic markers rs4673 and rs28714259 was shown for the prompt detection of the risks of AMC development in the management of cancer patients. However, population characteristics should be taken into consideration for risk assessment.

e13518 Background: With the advent of deep sequencing, enormous variability in miRNA biogenesis was detected, which means that many different sequences can potentially be generated from the same miRNA precursor, potentially having different targets and opposite changes in expression. These variable forms of micro-RNA that differ from the reference sequence are called iso-miR. To date, features of iso-miR expression have not been studied in patients with colorectal cancer (CRC). The aim of the study was to analyze the differential expression of iso-miR in the tumor and normal tissues of patients with CRC. Methods: For iso-miR identification by method of multiple parallel sequencing, 18 patients with CRC (colon adenocarcinoma, G2-3) were selected. The mirVana miRNA Isolation Kit protocol (Ambion, Life Science Technologies, USA) was used to isolate small RNA fractions. The library was prepared using the TruSeq Small RNASample Preparation Kit (Illumina, USA). Sequencing of the nucleotide sequences of cDNA libraries was performed using a MiSeq (Illumina, USA). The determination of iso-miR expression was carried out by comparing the nucleotide sequence of the sequenced molecules in each sample with the known nucleotide sequences of micro-RNA presented in the databases. When analyzing the iso-miR differential expression, the DESeq method implemented in R medium was used. Results: Several iso-miR classes were found (exact, lv3p, mv (multiple variant), nta#T#1 (non-templated T addition)). The most represented is the exact class (corresponding to the canonical miRBase sequence) and lv3pE (3 'extended: it starts from the same position as the canonical sequence, but is longer than the canonical sequence). Statistically significant (p < 0.001) differences in the expression of tumor tissue relative to normal were found for hsa-miR-143 (exact), hsa-miR-26a (exact) and hsa-miR-27b (exact) - a decrease in expression in 3, 32 and 6 times respectively, for hsa-miR-10a (lv3p), hsa-miR-10b (lv3p), hsa-miR-10b (mv) - a decrease of 2 times, for hsa-miR-143 (lv3p) - an increase of 2 times, hsa-miR-143 (nta # T # 1) - a decrease of 5 times, for hsa-miR-192 (lv3p) and (nta # T # 1) - a decrease of 16 and 3 times, respectively. Conclusions: Differential expression of 4 iso-miR classes (exact, lv3p, mv, nta # T) hsa-miR-26a, hsa-miR-27b, hsa-miR-10a, hsa-miR-10b, hsa-miR-143 and hsa-miR-192 was found in patients with CRC, which probably can affect the transcriptional activity of the genes they target. These iso-miRs are also likely to act as potential tumor markers.

e14549 Background: Gliomas are the most common type of primary brain tumors characterized by pronounced proliferation and aggressive infiltration. The purpose of the study was to analyze the expression of genes participating in the EGFR, TGF-B, HH/GLI, NOTCH and HIF1-alpha signaling pathways, transcription factors HBP1, MSI1/2 and demethylating agents in samples of various glioma types. Methods: The study included paired samples (tumor and physiologically unchanged neural tissue) obtained from 75 patients with histologically verified glial tumors of various grades (G2 - 21, G3 - 11, G4 - 43 patients). Relative expression of 15 genetic loci (EGFR, SMAD4, SMAD7, SMO, NOTCH1, NOTCH2, HBP1, HIF1A, EGLN1, EGLIN3, KDM1B, KDM1A, MSI1, MSI2, TET1) was measured by RT-qPCR. The PSMC, TBP and RPLO genes were used as the reference sequences. The 2−ΔΔ Сt method was used to analyze the qPCR data. Statisical processing of the results was performed with the Statistica 10 program (StatSoft Inc., USA). Results: G2 gliomas showed a significant change in the relative expression of the KDM1A gene (p = 0.00572); G3 - a significant change in the relative expression of the HIF1A gene (p = 0.012726); G4 - significant changes in the relative expression of the EGFR (p = 0.021324), SMAD4 (p = 0.016534), SMAD7 (p = 0.000003), HBP1 (p = 0.003264), HIF1A (p = 0.007612), EGLN1 (p = 0.001623), EGLN3 (p = 0.004231) genes. Registered changes in the expression of the KDM1A and SMAD7 genes in the studied sample significantly differentiated the G2 and G4 glial tumors (p = 0.013 and p = 0.049, respectively). G2 tumors were characterized with increased expression of the KDM1A gene and decreased by more than 1.1 times in 95% of patients. 88% of patients with G4 tumors demonstrated no changes or a decrease in the KDM1A gene expression and decreased SMAD7 expression by more than 1.5 times. Conclusions: The established significant change in the expression of the KDM1A and SMAD7 genes depending on the tumor grade can be used for the differential diagnosis of gliomas.

e18029 Background: Numerous studies on cervical cancer confirm an important role of specific genomic changes in the onset and development of cervical intraepithelial neoplasia and their effect on the progression of cervical cancer. Solid tumors are characterized by genomic changes leading to a change in the DNA sequence copy number. The purpose of the study was to reveal changes in the relative copy number of the ESR1, ESR2, GPER1, STS, SULT1A1, SULT1E1, CYP1A1, CYP1A2 genes responsible for the reception and metabolism of estrogens in cervical tissues in endophytic and exophytic patterns of tumor growth in order to find predictive markers of malignancy. Methods: The study included 40 patients aged 28-65 years with cervical cancer of endophytic (n = 20) and exophytic (n = 20) growth patterns. Eligibility criteria included a morphologically confirmed cervical squamous cell cancer T1b-2aN0M0, stage I-II. The Thermo Scientific GeneJET FFPE DNA Purification Kit was used for the DNA extraction from FFPE blocks of tumor and healthy tissues. DNA concentrations were measured on the Qubit 2.0 fluorimeter (Invitrogen, USA) using the Quant-iT dsDNA High-Sensitivity (HS) Assay Kit (Invitrogen, USA). Results: The relative copy number of the GPER1, SULT1A1, CYP1A1 genes in tumor samples increased (p < 0.05) compared with normal tissues in the total sample of patients diagnosed with cervical cancer. In contrast to the total sample, an increase in the SULT1A1 gene dosage did not reach a statistically significant level in any group (p = 0.242 and p = 0.157); the copy number of the GPER1 locus significantly increased only in the group with the endophytic growth pattern (p = 0.040), as well as the CYP1A2 gene dosage (p = 0.025). Patients of 36-55 years with endophytic tumors showed a statistically significant (p < 0.05) increase in the GPER1 and CYP1A1 gene copy numbers with the rates of 41.7% and 66.7%, respectively, as well as an increased amplification of the CYP1A2 gene in 41.67% of patients. In women of 56-75 years with endophytic tumors, an increase in the copy numbers of the ESR2, GPER1, SULT1A1 genes was observed with a frequency of 50%, 100% and 75%, respectively. Patients aged 20-35 and 36-55 years with exophytic tumors showed a statistically significant (p < 0.05) increase in the CYP1A1 gene copy numbers in 33.33% and 45.45%, respectively. Conclusions: The results suggest the use of the GPER1, SULT1A1 and CYP1A1 gene copy numbers as biomarkers of cervical tumors.

e13504 Background: Numerous pharmacogenetic studies have led to the identification of genetic polymorphisms associated not only with the development of cardiovascular disease, but also increase the risk of complications due to the use of anthracycline drugs, widely used in the treatment of cancer. The purpose of this study was to assess the prevalence of rs28714259 polymorphism and to study possible correlation with anthracycline-mediated cardiotoxicity (AMC). Methods: The study included 173 Caucasian patients (median age 55 years) with a diagnosis of breast cancer without diagnosed cardiovascular pathology who underwent treatment in the RRIO, Rostov-on-Don in 2019. For genotyping of SNP rs28714259, DNA was extracted from blood using DNA-sorb-B (AmpliSens, Russia) and HRM-PCR was performed on a CFX96 amplifier (Bio-Rad, USA). The presence of polymorphism was confirmed by Sanger sequencing with a Genetic Analyzer 3500 (ABI, USA). The obtained results were compared with European population (1000 Genome). Results: 13 patients (7.5%) with an early-onset of chronic AMC were founded after three courses of chemotherapy. The allelic frequency rs28714259 was 0.079, the frequency of AG genotypes was 0.135, and AA was 0.012. It was shown that the presence of this SNP leads to an increase risk of cardiovascular pathology at an early stage by more than 4 times (OR = 4.186, p = 0.006). In addition, when comparing with the European population, the highest probability of developing early-onset chronic AMC was determined for patients with the AA genotype (more than 22 times, p = 0.001). Conclusions: In this study, a statistically significant association of rs28714259 presence with developing early-onset chronic AMC was revealed, which seems promising for the early determination of the risk group in the management of cancer patients.

e13649 Background: The survival of patients with esophageal squamous cell carcinoma depends not only on clinical signs (TNM, tumor site), but also on the molecular genetic subtype of the tumor. Identification of the molecular genetic subtype and the presence/absence of clinically significant mutations is an important step towards finding new effective drugs and choosing the most appropriate therapeutic strategies. A patient-derived xenograft (PDX) model is a valuable resource to solving the problem, provided that the model accurately reproduces the basic clinical and molecular genetic characteristics of a human tumor. Our purpose was to create a PDX model of a human tumor and to study 7 polymorphisms of the xenograft tissue and tissues of a donor tumor. Methods: PDX models of esophageal cancer were produced by transplanting a tumor fragment from a patient with esophageal squamous cell carcinoma to the BALB/c Nude athymic mice (n = 10 for one PDX generation). 5 PDX were generated. 7 polymorphisms (NFE2L2 (c.85G > A), NOTCH1 (c.1379C > T), NOTCH1 (c.1451G > T), ZNF750 (c.414C > A), ZNF750 (c.1621G > A), SMARCA4 (c.2272C > T), KMT2D (c.15508C > T)) were determined by the HRM analysis in tissues of each PDX generation and in the donor tumor. Results: All examined samples demonstrated the absence of ZNF750 (c.1621G > A) and NOTCH1 (c.1379C > T) polymorphisms and the presence of ZNF750 (c.414C > A), SMARCA4 (c.2272C > T) and KMT2D (c.15508C > T) polymorphisms. Polymorphisms in the NFE2L2 (c.85G > A) gene and in the NOTCH1 (c.1451G > T) gene were found in the F3, F4 and F5 PDX generations, but were absent in the donor tumor and the F1 and F2 generations. Conclusions: Molecular and genetic characteristics of the donor tumor change through several PDX generations. Early PDX generations are recommended for the studies as they better reproduce molecular and genetic characteristics of the original tumors.

e13648 Background: Patient-derived tumor xenograft (PDX) models are a valuable resource for studying cancer biology and antitumor drug evaluation. The suitability of tumor models in vivo depends on how accurately they mimic a human disease and reproduce the histotype and molecular genetic features of a human tumor. The purpose of the study was to create a PDX model of human cancer and analyze its characteristics. Methods: PDX models of esophageal cancer were obtained by transplanting a tumor fragment from a patient with esophageal squamous cell carcinoma to the BALB/c Nude athymic mice (n = 10 for one PDX generation). Preservation of the tumor histotype was confirmed histologically (hematoxylin and eosin staining). 5 PDX were generated. An analysis of the relative copy number of the YAP1 and KDM6A genes (Real-Time qPCR) in xenograft and donor tumor tissues was performed in each generation. Results: A decrease in the copy numbers of the YAP1 and KDM6A genes by 3.8 and 2.2 times, respectively, was observed in PDX tumor samples (F3 generation) compared to normal donor tissues (p < 0.05). This trend maintained in F4 and F5 generation PDX samples. No changes in the copy numbers of the YAP1 and KDM6A genes were detected in PDX tumor samples in F1 and F2 generations. A cluster analysis (Hierarchical Clustering, Euclidean distance) demonstrated that samples of the first and second generations of esophageal cancer PDX models were closest to the patient tumor tissues in gene copy numbers. Conclusions: Later generations of esophageal cancer PDX models are characterized by changes in the genes copy numbers due to changes in the tumor and clonal selection. Early PDX generations better reproduce genetic, molecular and morphological features of tumors.

e13516 Background: The colorectal cancer (CRC) incidence is steadily increasing. Moreover, the problem of its early diagnosis remains unresolved due to the low specificity of known tumor markers, and the problem of creating new therapeutic approaches is due to the lack of a complete understanding of the mechanisms of regulation of gene expression in this oncopathology. The study of micro-RNAs (short non-coding RNAs that regulate gene expression) can be the solution to both problems. The aim of the study was to analyze micro-RNA differential expression in the tumor and non-tumor tissues of CRC patients. Methods: 5 patients with CRC (colon adenocarcinoma, G2) were selected for the multiple parallel micro-RNA sequencing. The mirVana miRNA Isolation Kit protocol was used to isolate small RNA fractions. The miRNA library was prepared using the TruSeq Small RNASample Preparation Kit. Sequencing of the nucleotide sequences of cDNA libraries was performed using a MiSeq (Illumina, USA). The copy numbers of micro-RNA were determined by comparing the nucleotide sequence of the sequenced molecules in each sample with the known nucleotide sequences of micro-RNA presented in the databases. When analyzing the differential expression of micro-RNA, the DESeq2 method implemented in R medium was used. Results: Six differentially expressed micro-RNAs were detected (p < 0.05): 2 that decrease expression (hsa-miR-143-3p,hsa-miR-26a-5p) and 4 increase expression in the tumor relative to non-tumor (hsa-miR-25-3p, hsa-miR-92a-3p, hsa-miR-21-5p, hsa-let-7i-5p). The highest level of expression in both tumor and non-tumor tissue was observed for hsa-miR-143-3p, the lowest one for hsa-let-7i-5p. Moreover, the largest difference in micro-RNA expression in tumor tissue relative to non-tumor was shown for hsa-miR-92a-3p (4.5 times, p = 0.02), the smallest for hsa-miR-143-3p (2.4 times, p = 0.04). For miRNAs that differentially changed their expression, a search was made for target genes using the miRWalk 3.0 database. 14573 target genes were found, of which 3346 were for hypo-expressed micro-RNAs and 11228 for hyper-expressed micro-RNAs. Conclusions: Sequencing revealed 6 differentially expressed micro-RNAs (hsa-miR-143-3p, hsa-miR-26a-5p, hsa-miR-25-3p, hsa-miR-92a-3p, hsa-miR-21-5p, hsa-let-7i-5p) in the tumor tissue is relatively non-tumor tissues of the colon. The data obtained expand the understanding of the mechanisms of gene regulation in the context of this oncopathology and may possibly become the basis for highly specific tumor markers panel.

e16699 Background: Pancreatic neuroendocrine tumors (panNETs) are a heterogeneous, relatively rare type of neoplasm which distinguishes a long clinical course in a large number of cases, that leads to the fact that the prevalence rate of NETs is one of the highest. The purpose of this study was a research the mutational profiles of panNETs of various grades of malignancy and to search for new candidate genes involved in the oncogenic processes of this pathology. Methods: The study included a retrospective group of 24 patients (10 men, 14 women, median age - 60 years old) with a diagnosis of panNET, treated in the RRIO from 2011 to 2018. Comprehensive cancer panel (409 genes) were used for NGS procedure on the NextSeq 550 platform(Illumina, USA). To work with raw data, we used the standard pipeline proposed by BaseSpace (Illumina, USA). Interpretation of the identified variants was carried out in accordance with the recommendations of the Association for Molecular Pathology, American Society of Clinical Oncology and College of American Pathologists. Results: 119 mutations in 54 genes were detected in samples of panNETs. 26 genetic variations were characterized as new, not previously described for panNETs. 18% of the mutations were activating, 35% of the variants led to a loss of function of the encoded protein, 52% were not classified. Candidate genes that have not been previously described in the literature and which are potentially involved in pancreatic oncogenesis are identified: CREB1, TCF12, PRKAR1A, BCL11A and BUB1B. The largest number of mutational events occurred in the genes responsible for histone methylation; in addition, 38% described genetic alterations in the regulation of the SMAD2/3 signaling pathway. Conclusions: According to the NGS study of panNETs of low and moderate malignancy in the Russian cohort, a unique spectrum of 119 mutations was obtained, of which 26 were not previously described. The discovered molecular genetic changes in the signaling pathways underline the importance of impaired epigenetic control of transcription in pancreatic oncogenesis and open up new prospects for targeted therapy.

e13088 Background: The development of breast cancer (BC) and ovarian cancer (OC), as well as their chemoresistance may be due to the presence of mutations in many genes, but most often in BRCA1/2 and CHEK2. Early diagnosis and subsequent preventive interventions improve the survival of patients with mutations in the BRCA1/2 genes. Genotyping of the gene inactivation events predicts a high sensitivity of BC and OC to platinum-containing cytostatics. Our purpose was to study the spectrum of germline mutations in the BRCA1/2 and CHEK2 genes in BC and/or OC patients in the South of Russia. Methods: The study included 622 patients of 10 nationalities with BC and/or OC from the South of Russia. Genomic DNA was isolated from peripheral blood leukocytes; mutations were detected by Real-Time PCR in the BRCA1 (185delAG, 300T > C, 2080delA, 4154delA, 5382insC, 3819delGTAAA, 3875delGTCT), BRCA2 (6174delT), CHEK2 (1100delC, IVS2+1G > A, 470T > C) genes. Results: Mutations in the BRCA1/2 gene were found in 13.5% of cases, in CHEK2 – 6.2%. In the BRCA1/2 gene, the frequency of 5382insC mutation was 76.2%; 4153 delA – 9.5%; 300T > G – 7.1%; 2080delA – 3.6%; 185delAG, 3875delGTCT, 6174delT - 1.2% each. In the CHEK2 gene: 470Т > C – 73.1%; IVS2+1G > A – 23.1%; 1100delC – 3.8%. Two patients showed a combination of 5382insC mutation in the BRCA1 gene and 470T > C mutation in the CHEK2 gene. The observed prevalence of mutations in BRCA1 was generally consistent with that for European countries (p = 0.062). Identification of 470T > C mutation in CHEK2 in two cases confirmed the final diagnosis of Li-Fraumeni syndrome (OMIM: 609265); however, we failed to establish a family history of cancer in one patient. A high-risk cancer group was formed for prophylactic purposes based on the data of genotyping for major mutations in the BRCA1/2 and CHEK2 genes in patients with BC/OC and their healthy relatives. Conclusions: The frequency of BRCA1/2 and CHEK2 mutations in the studied multinational population of Caucasian patients with BC and/or OC was 17.2%. The 5382insC BRCA1/2 (76.2%) and 470Т > C CHEK2 (73.1%) mutations were the most frequent which corresponded to the occurrence of these SNPs in populations of European countries.

e23525 Background: Gastrointestinal stromal tumors (GIST) are rare malignant mesenchymal neoplasms of the gastrointestinal tract, the diagnosis and treatment of which is associated with the presence of mutations in the c-KIT and PDGFRA genes. Purpose of this study was molecular genetic genotyping of GIST according to clinically significant exons of the c-KIT and PDGFRA genes. Methods: The study included patients with an immunohistochemically confirmed diagnosis of GIST who underwent treatment in the RRIO, Rostov-on-Don, for the period 2018-2019 (n = 20, median age 63.5 years, men/women–10 people each, gastric tumors). DNA was isolated from FFPE tissue using the GeneJET FFPE DNA Purification Kit, USA. The presence of mutations in exons 9, 11, 13 and 17 of c-KIT and exon 18 of PDGFRA was detected by Sanger sequencing. Results: Activating mutations in exon c-KIT were detected in 10 ps, including one substitution p.V560E and 4 deletions – p.V559_E561del, p.M552_V555delMYEV, p.W557_V559 > F and p.W557_V559 > C. These mutations cause sensitivity to imatinib. Pathogenic mutations were detected in PDGFRA exon 18: an activating deletion p.I843_D846delIMHD (2 ps) and a substitution p.D842Y, which determines imatinib resistance (2 ps). Thus, 20% of GIST cases are promising for obtaining avapritinib, the first FDA approved drug in 2020 for patients with GIST with a mutation in PDGFRA exon 18. In addition, neutral genetic variants were revealed: in 17 exon c-KIT in 16 patients, benign rs1008658, in PDGFRA 18 exon – rs3830355 (3 ps) and silent mutation p.V824V (3 ps). Conclusions: Genotyping of c-KIT and PDGFRA identified 12 types of clinically significant mutations and, in 80% of cases, the carriage of benign polymorphisms and / or SNPs of unknown clinical significance. As a result, 70% of patients from the South of Russia with GIST may be sensitive to treatment with imatinib and/or avapritinib.

e13525 Background: Cancer is a disease characterized by uncontrolled cell proliferation. DNA replication is the main driving force behind cell proliferation in both normal development and cancer. Non-coding Y-RNAs are important factors in initiating DNA replication in the nuclei of human cells. Excessive expression of Y-RNA is characteristic of tumors of the bladder, cervix, kidney, lung and prostate. It has also been shown that the level of small RNAs formed from the 3'- and 5'-ends of Y-RNA is significantly higher in patients with certain types of cancer compared to healthy people, therefore, these RNAs may have diagnostic value. However, for colon tumors, data on the expression of Y-RNA/YsRNA obtained in previous studies are ambiguous. The aim of the study was to analyze the differential expression of YsRNA in the tumor and non-tumor tissue of patients with CRC using next generation sequencing (NGS). Methods: For NGS, 10 patients with CRC (colon adenocarcinoma, G2). were selected. Small RNA fractions were isolated using the mirVana miRNA Isolation Kit protocol (Ambion, Life Science Technologies, USA). The library was prepared for sequencing using the TruSeq Small RNASample Preparation Kit (Illumina, USA). Sequencing of the nucleotide sequences of cDNA libraries was performed using a MiSeq (Illumina, USA). The determination of the copy number of Y-RNA fragments (YsRNA, 19-34 bp) was carried out by comparing the nucleotide sequence of the sequenced molecules in each sample with the known nucleotide sequences presented in the databases. In the analysis of differential expression, the edgeR method, implemented in the R language, was used. Results: Several different fractions of YsRNA were detected in tumor and non-tumor tissues: hY3sRNA (the most represented fraction, more than 70%), hY5sRNA and hY1sRNA. In tumor tissue relatively non-tumor, a statistically significant (p < 0.001) increase of 4 and 6 times the number of copies of hY3sRNA and hY5sRNA, respectively, was detected. The function of YsRNA in tumor and normal cells has not yet been established. Conclusions: Thus, in the tumor colon tissue differential expression of 2 YsRNA fractions - hY3sRNA and hY5sRNA, was detected. These YsRNAs can become promising tumor markers and targets for the treatment of CRC, as well as make certain contributions to understanding the mechanisms of carcinogenesis in this nosology.

e22517 Background: Neuro- and nephroblastoma are the most common pediatric solid tumors. Their varying clinical behavior determines challenging prognosis and choice of treatment tactics. Along with many clinical parameters, the genetic characteristics of tumor cells appear promising. Methods: The study included patients diagnosed with neuroblastoma (n = 10) and nephroblastoma (n = 10) (median age from 2 months to 8 years; 10 boys and 10 girls). Total RNA was extracted from paired tumor/normal samples using the miRNeasy Mini Kit (Qiagen, USA) and cDNA libraries obtained with the Reverta-L kit. Expression of the CRABP1, CRABP2, FABP4, FABP5, RAR, RXRA, RXRB, and PPARD genes was evaluated by RT-PCR on the CFX96 amplifier (Bio-Rad, USA). GAPDH and B2M were reference loci. Relative expression (Exp) was calculated by the 2-ΔCt method. Results: The qPCR-RT showed a significant increase in the transcriptional activity in both tumors, compared to normal tissues, for the FABP4, FABP5, and RXRA loci (p < 0.01). Interestingly, we observed multidirectional changes in mRNA levels in neuroblastomas and nephroblastomas for the CRABP1, RAR, and PPARD loci. Unlike solid tumors of adult patients, the expression activity of the CRABP1 gene either did not differ from the conditional norm (in nephroblastoma), or significantly dropped to 70% (in neuroblastoma). In contrast to adult solid tumors, the CRABP1 gene expression activity in children was normal (in nephroblastoma) or decreased significantly up to 70% (in neuroblastoma). Conclusions: The pilot study revealed differentiating aberrant expression of genes encoding the family of retinoic acid transporters and receptors in pediatric neuroblastomas and nephroblastomas. This may be essential for choosing the optimal treatment volume and establishing a prognosis and resistance to chemotherapy in patients with these tumors.

e14550 Background: HIF1-alfa is a powerful regulator of angiogenesis and cell invasion activating a wide range of oncogenes. Control of the HIF1-alpha transcription is strictly regulated by many molecular pathways, including miRNAs which can become targets for gene therapy of cancer. Methods: The study included 30 patients with histologically verified high-grade gliomas. RNAs were isolated from 30 paired (tumor and control) samples using the TRIzol reagent (Thermo Fisher, USA). The cDNA synthesis was performed using the Reverta MMLV kit (Sintol, Russia). Expression of miRNAs and HIF1A was evaluated by RT-PCR using the CFX96 system (Bio-Rad, USA). The 2−ΔΔ Сt method was used to analyze the qPCR data. Statisical processing of the results was performed with the Statistica 10 program (StatSoft Inc., USA). Results: Using analysis of TargetScan and miRTarBase databases and appropriate literature, miRNAs (miR-122-5p, miR-107, miR-22-5p and miR-330-3p) able to regulate HIF1A expression were selected. The HIF1A expression in the tumor was 1.8 times higher, compared to normal tissue (p = 0.0031). The 2−ΔΔ Сt value for miR-122-5p, miR-107, miR-22-3p and miR-330-3p decreased by 40%, 45%, 36%, and 91.5%, respectively, in tumor samples relative to the control point (p < 0.05 in all cases). A correlation was found between the expression of miRNA 122-5p and HIF1A (Spearman’s r = -0.46 at p < 0.05). Conclusions: An increase in the HIF1A miRNA level was found, together with a decrease in the expression of four potentially targeting miRNAs in high-grade gliomas. A negative correlation between the expression of miR-122-5p and HIF1A in high-grade gliomas was revealed, which can be used for the development of new therapy options.

90 Background: Complete or partial deficiency of the DPD enzyme due to genetic polymorphisms of the DPYD gene causes acute toxicity of fluoropyrimidines, which are widely used in combination chemotherapy regimens for various malignant neoplasms. The purpose of the study: to identify polymorphisms of the DPYD gene significant for 5-fluorouracil-induced toxicity. Methods: Venous blood samples from Caucasian patients were used to identify alleles of *2А rs3918290, 5* rs1801159, *13 rs55886062 and rs67376798 DPYD by RT-PCR and direct sequencing. Inclusion criteria were: verified diagnosis of gastrointestinal tumors, age>18 years old, fluoropyrimidine-containing regimes of treatment. Results: 104 pts were included, 54% were female. Mean age-61 years. Colorectal cancer was found in 80.7% pts, non-colorectal in 19.3% pts. Hematological and non-hematological toxicity Gd.3-4 was found in 24% pts. Allele * 5rs18011595, which causes enzyme deficiency was found in 28% of patients, (frequency was 0.281) which is significantly higher than the population frequency of the allele charactering for Caucasoid population (p

e22517 Background: Soft tissue sarcomas (STS) are relatively rare malignant tumors of mesenchymal origin, constituting about 1% of all solid human tumors. About 11% of STS cannot be classified. The relapses of STS are difficult to predict. So, the studying of molecular origin of STS remains to be an actual issue. We analyzed copy number variations (CNVs) of apoptosis-regulating genes and MKI67 gene in primary and recurrent STS. Methods: 32 patients with primary STS and 26 patients with relapses were investigated. Relative CNVs of bax, bcl2, casp3, casp8, casp9, p53, mdm2 and M kI67 were detected with the use of RT–qPCR in fresh frozen tumor and normal tissues obtained while surgical access. Relative Copy Quantitation (RCQ) was accounted with GAPDH and ACTB as reference genes. Results: The frequencies of CNVs of the studied genes in groups of primary and recurrent STS are presented in the table below. A significant change only in the group of primary STS sarcomas was observed for CNV of MDM2, whereas the amplification of the CASP3 and MKI67 genes was characteristic of recurrent sarcomas. CNVs of BAX and CASP8 were significantly more frequent in primary STS. Increased amplification of MDM2 gene, was observed only for liposarcomas among all the others STS. The literature describes amplification of chromosome 12q13-15 where MDM2 gene is localized as a diagnostic feature of liposarcoma which is consistent with our observations [Todorov SS, Kit OI Modern understanding of the morphogenetic features of liposarcomas // Archives of Pathology. 2012. T. 74. №6. p.59-61]. Conclusions: The study showed the potential role of CNV of the BAX, CASP3, CASP8 and MKI67 genes to develop an approach to predicting the course of STS and the effectiveness of the MDM2 gene amplification as an additional marker for liposarcoma molecular classification.[Table: see text]

e20542 Background: Lung cancer is the most common malignant tumor after breast cancer and is the main cause of cancer mortality. Mutations in the EGFR gene typical of lung cancer lead to constitutive activation of the epidermal growth factor receptor and malignant cell transformation. The purpose of this study was to identify associations between double and triple mutations in EGFR and clinical and pathological characteristics of patients in the South of Russia diagnosed with lung cancer. Methods: DNA was extracted from FFPE samples of 240 patients. Mutations in EGFR were detected using Cobas EGFR Mutation Test detection kit (Roche). Results: The mutant type of EGFR was identified in 24.6% of cases, and the most common activating mutations were ex19del (47.5%) and L858R (30.5%). Insertion in exon 20 was detected in 5.1% of mutation cases, G719X - in 3.4%. We also registered cases of identification of two or three mutations in one tumor: ex19del - L858R, ex19del - T790M, L858R - T790M with a frequency of 3.4% and G719X - ex20ins, ex19del - L858R - ex20ins with a frequency of 1.7%. Similar frequency is characteristic of the Caucasoid population of the USA. Multiple mutations in EGFR are associated with early manifestations of lung cancer and rapid progression of the disease. Two patients with two mutations EGFR T790M and L858R were of particular interest. According to the literature data, T790M is the most common somatic mutation that causes resistance to targeted therapy; however, rare cases could be associated with germinal variation of T790M. The primary T790M mutation is more common in patients with two or three mutations in EGFR. Conclusions: Mutations in the EGFR gene were detected in 24.6% of lung cancer cases in a patient population in the South of Russia. The frequency of two or three mutations in the EGFR gene was 0.33%. The timely detection of these mutations is particularly important for family cases when the risk group can be determined.

e17524 Background: Mutations in KRAS are known to be predictors of anti-EGFR therapy efficacy. Besides the mutation status of the treatment-naive tumors the changes in the level of mutant DNA during medical treatment are also of clinical interest for the individualization of the treatment. The purpose of the study was to detect somatic single nucleotide polymorphism (SNP) activating mutations in KRAS exon 2 in patients (pts) with OMTC undergoing chemotherapy (CT)±Cetuximab (Cet). Methods: Extracellular DNA samples were obtained from plasma of pts with OMTC (T3-4No-1Mo) undergoing CT (CDDP+5FU)+Cet (group A) before treatment and in 2 weeks after. Patients undergoing CT (CDDP+5FU, no Cet) were included in Group B. 7 activating mutations in KRAS exon 2 were detected by Droplet Digital PCR method (DD PCR) with "KRAS Screening Multiplex Kit" (BioRad, USA). Results: Samples from 28 pts were included. The frequency of SNP activating in KRAS exon 2 before treatment was 25%. In the group A (n = 12) KRAS mutations were not found or the level of mutant DNA did not exceed 1%. No significant changes were found in this group after treatment. The group B (n = 16) had some KRAS variations the majority of which did not change after treatment. However, 2 pts had a sharp increase in mutant DNA: from 0.03% before CT in both cases to 17.04% and 56.38% -after treatment (p < 0.01). Conclusions: Medical treatment, especially CT, could cause the changes in activating mutations in KRAS exon 2 in pts with OMTC. Revealing of these changes is of great importance for the following treatment options. Detection of mutant extracellular DNA by DD PCR could be valuable to monitor their status during the treatment.

e13511 Background: Development of alternative methods of non-invasive therapy in neurooncology is determined by the need to prevent the continued growth of glioblastoma and radiation-induced complications. Usage of electromagnetic influence for these reasons is determined by the oscillatory nature of intracellular processes and results of previous studies on the effect of weak electromagnetic radiation in tumor growth. The purpose of the study was to reveal the effect of a pulsed magnetic field (PMF) and ionizing radiation (IR) on human T98G glioblastoma cells. Methods: Human T98G glioblastoma cells were cultured in the RPMI-1640 medium (Biolot, Russia) supplemented with 10% fetal bovine serum (Thermo Scientific HyClone, USA). The culture was seeded in the Biofil plates (at least 8x105 cells per 3 mL of the medium), incubated (CB 150 Binder, Germany) and exposed to IR 10 Gy (TheratronEquinox-BestTheratronics) for 11.7 min. and/or PMF 15 mT or 300 mT with a sequence of frequencies 0.3-3.0-9.0 Hz for 7 min. (Neiro-MS/D by Neirosoft, Russia). The efficiency criteria were lethality and the mitotic activity of human T98G glioblastoma cells. Results: The highest cellular lethality was registered 3 hours (18.7 vs. 5.2% in controls, p≤0.05) and a day after IR exposure. PMF 15 or 300 mT alone increased lethality by 2.5-2.8 times compared to controls (p < 0.05). IR plus PMF (15 mT) did not caused increased lethality. At the same time, the most pronounced decrease in the mitotic activity a day after exposure (by 4.7 times, p < 0.05) was registered in PMF alone (15 mT). Conclusions: The inhibitory effect of PMF on the viability of human glioblastoma cells indicates the prospects for its use as an accompanying treatment in neurooncology.

e13008 Background: The new 2016 WHO classification of tumors of the central nervous system takes into consideration mutational status of IDH genes. Research of molecular changes in gliomas remain to be an actual issue. We analyzed the gene expression of some significant pathways in gliomas. Methods: 27 patients (12 females, 15 males) aged from 27 to 76 years with verified brain tumors (glioblastomas (G4) – 67%, anaplastic astrocytomas and oligoastrocytomas (G3) – 11%, astrocytomas (G2) – 22%) were investigated. 7 mutations in the IDH1 gene and 5 ones in IDH2 in fresh frozen tumor tissues were detected by RT-qPCR with Therascreen IDH1/2 RGQPCR kit (Qiagen). The expressions of EGFR, SMAD4, SMAD7, SMO, NOTCH1, NOTCH2, HBP1, HIF1A, EGLN1, EGLIN3, KDM1B, KDM1A, MSI1, MSI2, TET1 genes in tumor and normal brain tissue obtained while surgical access were assessed with RT-qPCR. PSMC, TBP and RPLO were used as reference genes. Results: Analysis of IDH1/2 status revealed only R132H mutation of IDH1 in 6 patients. The ratio of the relative expression of genes in tumor tissue with mutation and wild-type and the significance of the differences in the Mann-Whitney test are presented in the table below . Conclusions: Expression of SMAD7, EGLN1, EGLN3 as an activating factor of TGF-b-signaling pathway potentially may be used as an additional prognostic marker of gliomas progression.[Table: see text]

Uniqueness and high commercial value of relic group of sturgeon fishes stimulated researches of their genetic polymorphism. In the review the basic molekular-genetic markers used for an estimation of genetic variability are considered; their merits and demerits are discussed, examples of their application, basically, on Acipenseriformes Eurasia are resulted. Problems of the genetic analysis polyploid kinds are is short covered.

588 Background: Global hypomethylation of the genome is one of the causes of chromosomal instability and aneuploidy and is associated with an increased risk of colorectal cancer (CRC). The long interspersed nucleotide element-1 (LINE-1) is the main part of the mobile repeated elements of the genome, and the level of its methylation is concordant with genome-wide methylation. The aim of the study was to assess the methylation of LINE-1, as well as methylation of the promoter of six cancer-associated genes adjusting for the clinical and pathological characteristics in colorectal cancer (CRC). Methods: Using pyrosequencing (PyroMark Q24 analysis system, Qiagen, Germany) DNA methylation levels of LINE-1 and 6 genes ( APC, CDH13, MLH1, MGMT, P16 and RASSF1A) were measured in tumoral and normal tissues of 50 patients with CRC. Results: The level of LINE-1 methylation was 66.8 ± 0.89% in tumors, 72.5 ± 0.45% in normal tissues ( p = 0.0013). The differences in LINE-1 methylation level were not associated with age, differentiation grade, tumor localization, and the presence of activating mutation within the KRAS gene. At the same time, the MGMT methylation was positively associated with age ( p = 0.04), and the hypermethylation of the CDH13 gene was more common in tumors of the proximal colon ( p = 0.004). Methylation of the CDH13 promoter negatively correlated with methylation level of LINE1 ( r = -0.427, p < 0.05). Hypomethylation of LINE-1 was associated with progression of TNM-stages of the tumors ( r = +0.606, p < 0.001). The cancer-associated genes were hypermethylated in 70% of CRC cases when compared with normal epithelium, and hypomethylation of LINE-1 was observed in 90% of CRC cases. Conclusions: The present study demonstrated the association of LINE-1 methylation with the TNM tumor stage, which may be used as a biomarker for early diagnosis and prognosis of sporadic CRC, together with assessment of hypermethylation of tumor suppressors.

e15066Background: Aberrant methylation of CpG sites within promoter regions of cancer-related genes is an important epigenetic event in carcinogenesis. The frequency of methylation changes of diffe...

2545 Background: The standard treatment of malignant brain gliomas, including surgical and radiation therapies, does not provide recovery and a long-time favorable prognosis. The development of technologies and international guidelines on the introduction of electric (TTF) and electromagnetic (TMS) fields in combination treatment for glioblastomas aims to improve immediate results, as shown in experiments on human glioblastoma cell culture. The TMS protocol requires further refinement in parameters of frequency, intensity, and exposure with an assessment of the immediate results of combined treatment. Methods: The study included 60 patients diagnosed with MBG receiving osteoplastic craniotomy with radical (within visible unchanged tissues) tumor removal. Starting from the second day after the surgery, patients of group 1 (n = 30) received 10 sessions of magnetotherapy in the double exposure mode. For the first morning exposure, we used an ultra-low-frequency magnetic field (ULFMF) (0.03 to 9.0 Hz) on the hypothalamus projection area to induce a general antistress reaction. After 2.5-3 hours, local (on the surgical site) TMS exposure with the Neuro-MSD system (Russia) was applied in the pulse algorithm, up to 1 GHz and 5 Hz, 15 mT, 3 min. The induction was reduced exponentially (C = 0.8). The control group 2 (n = 30) did not receive ULFMF or TMS. Magnetic resonance imaging (MRI) was used to determine the volume of tumors (Vt, cm3) and perifocal edema (Ve, cm3) calculated according to the Shrek’s formula for an ellipsoid (V = a×b×c×π/6). Results: Before surgery, Vt = 54.7±5.7cm3 in group 1, in group 2 - Vt = 60.9±8.5cm3 (no statistical differences). After surgery and the subsequent course of ULFMF and TMS, residual tumor volumes in group 1 were 2.5 times lower than in controls (p < 0.05). The difference between Ve values before and after treatment was on average 80.7 cm3 in group 1 and 41.8 cm3 in group 2 (p < 0.05). Conclusions: The inclusion of sequential ULFMF and TMS exposures into postoperative therapy for gliomas, taking into account various vectors of the influence on the projection of centers of homeostasis regulation and the surgical field, as well as the development of programmed modes of biotropic exposure parameters, improves antitumor and anti-edematous effects.