The melanoma origin of cell lines obtained from the axillary lymph node (mel Kas, mel Pet, and mel Lap from patients with a verified diagnosis) was confirmed by the detection of the Melan A melanocyte marker expression. A hyperdiploid (2n+) for the mel Kas line; near-diploid (2n), and in some cells near-tertaploid (4n), and even hypo-octaploid (8n) set (172–179 chromosomes) in the mel Pet cell line; and a hypotetraploid (4n−) for the mel Lap line were detected by karyotypic analysis. All three cell lines are tumorigenic; however, mel Pet demonstrates tumor growth in Balb/c nude mice only in the presence of matrigel. All three lines showed a high expression of TUBB3 and PD-L1 markers, while ERa was low (minimum for mel Pet). Significant differences in the expression level were shown for the Cyt molecular marker. In the transplantation of cells to Balb/c nude mice, a stable expression level is observed only for TUBB3. For the rest of the markers, a decrease in their expression level of varying degrees was noted when the cells were growing in solid tumors in vivo. Mutations were detected in oncogenes (BRAF, EZH2, KIT, KRAS, NRAS, ROS1) and tumor suppressor genes (CDKN2A, FAT4, KMT2C, LRP1B, PTEN, PTPRB, TP53). The detailed characterization of the cell lines makes them valuable for various scientific and regulatory experiments, particularly those involving preclinical data on antiproliferative drugs for malignant melanoma or investigations into melanoma cell properties and progression.

Bioresource collection of the N. N. Blokhin National Medical Research Center of Oncology is a unique structured biobank that combines different types of primary and subsidiary samples and ensures its comprehensive characterization, including both generally accepted indicators and specific types of research. Samples of paraffin blocks, frozen material, blood and its derivatives are deposited in the clinical department of the center. The research institute of the center has collected commercial and unique human cell lines and transplantable strains obtained from clinical material, as well as cells from laboratory animals, mainly of mouse origin. The provided cell lines undergo multi- stage quality control, including confirmation of authenticity, assessment of viability and determination of optimal cultivation conditions, analysis of interspecific and intraspecific contamination, study of tumorigenicity and reproducibility in athymic Balb/ c-nude mice, etc. In addition, the Bioresource Collection has hybridoma clones that produce antibodies to a wide range of targets. The Center provides the opportunity to conduct preclinical research using samples from the Bioresource Collection to obtain scientific and regulatory data on the antiproliferative activity of new agents or methods for cancer treatment.

Aim . To approve the COrDIS kit (Gordiz, Russia) for the authenticity of cell lines from the Bioresource Collection of the N.N. Blokhin National Medical Research Center of Oncology by the short tandem repeat (STR) profiling. Material and methods . The chosen method proved to be a reliable and reproducible option. With this approach, a number of polymorphic STR loci are amplified using commercially available primer sets. Polymerase chain reaction (PCR) products are analyzed simultaneously with size standards using automated fluorescent detection methods. The results are presented as a simple number code corresponding to the lengths of the PCR products amplified at each locus. By applying this method to cell lines, the laboratory can both authenticate commercial cell lines and build a database of their lines. In the work, we used the COrDIS EXPERT 26 kit (Gordiz, Russia), validated for molecular genetic identification of personality based on multiplex PCR analysis of 26 highly polymorphic loci of human genomic deoxyribonucleic acid. PCR results were analyzed by capillary electrophoresis using an automatic genetic analyzer with laser-induced fluorescence detection (Applied Biosystems 3500xL). Results . When testing the method, profiling of 37 cell lines was carried out, of which 18 were announced in international databases and 19 were unique, obtained at the N. N. Blokhin National Medical Research Center of Oncology, as well as a cell line mixture in order to determine the limits of contamination detection. The obtained results showed the correspondence of commercial cell lines with the data in international databases. Within the framework of this work, profiles of unique lines were obtained and the foundation of own genetic database was laid. Studies to identify the limit of contamination detection by another line have shown that even 4% of the contaminant culture in the total pool can be used to identify its individual alleles. Conclusion . The results obtained indicate the possibility of using the method to identify samples of the collection and detect intraspecific contamination.

Background. Plasma circulating tumor DNA (ctDNA) is a potential marker for tumor process monitoring. However, the feasibility of using mouse syngeneic subcutaneous melanoma model to assess ctDNA levels remains unclear.Aim. To evaluate the feasibility of ctDNA detection in mouse B16-F10 melanoma model using droplet digital polymerase chain reaction (ddPCR).Materials and methods. We developed and validated a ddPCR assay to quantify plasma ctDNA from B16-F10 cells. To form experimental tumors, C57Bl6 mice were inoculated with B16-F10 cells. On the first, 7th, 14th , 21st days after tumor inoculation blood was collected by retroorbital sinus puncture. ctDNA was extracted from blood plasma. On the 21st day after tumor inoculation mice were sacrificed.Results. We validated a ddPCR assay to quantify plasma ctDNA in B16-F10 melanoma syngeneic model in C57Bl6 mice. The assay linear range was 0.5–32 copies/ul, R2 = 0.997. The empirical limit of detection of ctDNA was 1 copy/ul in 5 ng normal tissue genomic DNA background. The coefficient of variation values ranged from 44.5 % (1 copy/ul) to 16.6 % (16 copies/ul). Plasma ctDNA was detected on 21st day after tumor inoculation in B16-F10 melanoma syngeneic subcutaneous model (p = 0.004). ctDNA concentration positively correlated with tumor volume (ρ = 0.95, p = 0.05) and total circulating DNA concentration (ρ = 1, p = 0.0).Conclusion. B16-F10 melanoma syngeneic subcutaneous model in C57Bl6 mice can be used to monitor cDNA in studies of new approaches for melanoma treatment.