e15508 Background: The most important stages of metastatic cascade are extravasation and invasion of malignant cells and their surviving in blood. The vast majority of circulating tumor cells (CTC) is destroyed by immune cells. The role of immune system which is able to play not only antitumor but also prooncogenic role is manifested both on local and systemic levels. We studied correlations between lymphocyte subsets` content in blood and in tumor of colorectal cancer patients (II, III, IV stages) with and without CTC. Methods: 60 colorectal cancer patients with II (n = 20), III (n = 20) and IV (n = 20) stages underwent surgery without previous chemotherapy. CTC were measured in blood by CellSearchSystem™ (JanssenDiagnostics, LLC), cell-mediated immunity was assessed in blood by flow cytometry (BD Canto II) and in tissue after surgery by immunohistochemistry; some markers of proliferation and epithelial-mesenchimal transition (EMT) in tumor cells (Ki-67, E- and N-cadherins) were also studied. Criteria of CTC-positive and CTC-negative samples were > 3 and ≤3 respectively. Correlative analysis was performed between the data of the patients with and without CTC in each stage, r was counted. Results: In CTC-positive patients with all the stages the number of strong and moderate correlations between system immunologic factors involving CD8+ appeared to be fewer than in CTC-negative ones (7 vs 19). On the contrary, the number of correlations with T regs in CTC-positive was increased: 5 vs 3 in CTC-negative patients. In patients with CTC > 3 fewer correlations were noted between factors of local and systemic immunity than in CTC-negative ones (9 vs 4 in II stage) and total disruption of all the correlations between system immunologic factors and proliferating tumor cells in III and IV stages was established. Some pathologic correlations appeared in CTC-positive patients like moderate direct one between activated T-lymphocytes` amount and Ki-67+ tumor cells. The number of correlations between intratumoral lymphocytes and tumor cells expressing proliferation and EMT markers in CTC-positive patients was decreased in comparison with CTC-negative ones (4 vs 10 in II stage, 1 vs 9 in III, 2 vs 9 in IV stage). Conclusions: The presence of CTC in colorectal cancer patients rather than tumor stage is associated with imbalance of their systemic and local immunologic factors. This provides some evidence that disruption of interactions in the immune system is at least partly due to CTC.

The classifications of the World Health Organization, the European Society of Car­-diology and the American Heart Association indicate the existence of several pheno­types of myocardial non-compaction (MnC) with specific structural and func­tional abnormalities. The MnC+dilated cardiomyopathy (DCM) phenotype is considered one of the most severe variants. Disputes continue about whether to regard MnC as an independent disease or as a consequence of DCM and heart failure. In other words, MnC remains one of the most mysterious heart diseases. As an illustration of MnC+DCM phenotype, the authors offer a case of a patient with cardiovascular disease from her youth, but maintained a satisfactory state of health and performance until her old age. Symptoms of arrhythmia and heart failure with massive pericardial effusion were first described in her at the age of 66, which is uncharacteristic for this MnC phenotype. Attention is drawn to the difficulties of differential diagnosis of MnC due to the non-specificity of clinical performance, the role of echocardiography in the recognition of the disease and predictors of its unfavorable outcome. The fact that the patient, even when typical signs of MnC were detected during echocardiography, initially had coronary artery disease as the main diagnosis, indicates the relevance of publishing another case report on this rare pathology in order to improve the awareness of cardiologists and general practitioners.

3522 Background: Cancer stem cells (CSCs) capable of self-sustaining and multipotent differentiation are considered among the most important factors limiting treatment effectiveness. ALDH1 is a marker of colorectal cancer (CRC) CSCs; it is involved in cell differentiation and proliferation, determines resistance to alkylating chemotherapeutic agents, and also induces epithelial-mesenchymal transition (EMT), which increases the invasive and metastatic potential of tumors. The purpose of the study was to assess the association between the expression of the ALDH1 CSC marker in tissues of CRC of different stages and clinical and morphological factors of the disease prognosis. Methods: The study included 299 patients (aged 42-86 years, mean age 64.2±1.7) with stage II-IV CRC T1-4N0-2M0-1; histologically verified G1-G3 adenocarcinoma in all patients. Tissues of surgically removed tumors were studied with IHC analysis using mouse monoclonal anti-ALDH1 antibodies (clone B-5, Santa Cruz Biotechnology) diluted 1:1800 and the Reveal Polyvalent HRP-DAB Detection System. The percentage of cells positively stained for ALDH1 among all tumor cells was assessed. Statistical analysis was performed using the STATISTICA 13.0 program (StatSoftInc., USA). Results: Positive ALDH1+ expression was registered in 52.5% of all patients, negative expression – in 47.5%. Statistically significant association was observed between the ALDH1 expression and the CRC stage, since the ALDH1+ expression increased from stage II to stage IV (p = 0.003). The ALDH1 expression was statistically significantly associated with the depth of tumor invasion (p = 0.018) and the presence of distant metastases (p < 0.001). No significant relationship was observed between the ALDH1 expression and regional lymph node metastasis (p = 0.788). Statistically significant association was registered between the ALDH1 expression and the tumor grade (p < 0.001), perineural invasion (p = 0.010) and lymphocytic infiltration (p < 0.001). No significant relationship was observed between the tumor histological structure (p = 0.979), lymphovascular invasion (p = 0.772) and ALDH1 expression. Tumor site was not statistically significantly associated with ALDH1 expression (p = 0.349). Conclusions: The study demonstrated statistically significant association between the ALDH1 expression and clinical and morphological characteristics of CRC, determining invasive and metastatic potential of the tumor, and ALDH1 may be an independent prognostic factor and a new therapeutic target for the regulation of the progression process.

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.

e15503 Background: The purpose of this study was to analyze the effect of the CD44+ and CD133+ co-expression in cancer stem cells (CSCs) on lymphocytic microenvironment of colon cancer (CC). Methods: 200 CC patients received surgery as the first stage of treatment. The percentage of CSCs with the expression of CD44+ and/or CD133+ markers was studied in the tumor homogenates by flow cytometry, as well as some indicators of local immunity (CD3+, CD4+, CD8+, T regs (CD4+CD25+CD127dim), CD19+, PD-1, PD-L1, Th0, Tm, CD16/56+ and immunophenotypic characteristics of tumor cells (PD-L1, MHC-ABC). Results: Gradation depending on the absence or presence of co-expression of CSC markers on tumor cells allowed identification of 11 statistically significant differences out of 17 studied parameters of tumor cells and their lymphocytic microenvironment. Co-expression of CSC markers was accompanied by higher percentage of T regs (7.3±0.4 versus 5.3±0.5%), together with lower levels of CD4+ cells. At the same time, a higher content of the total number of T-lymphocytes was noted due to CD8+ with an increase in the percentage of memory T cells and a decline in naive T lymphocytes within this subpopulation. In addition, the co-expression of CSC markers was accompanied by a lower content of PD-L1 (34.3±3.0 vs. 42.9±2.5%) on lymphocytes and its higher content on tumor cells (10.6±1.5 vs. 4.1±0.8%), while the PD-1 expression on lymphocytes was higher (38.4±3.7 versus 22.3±2.9%). The presence of CD44+CD133+ CSCs was also accompanied by lower percentage of tumor cells expressing MHC class I (60.4±4.9 vs. 79.3±7.6%), which characterized the inhibition of recognition processes, and increased levels of CD8+, perhaps, should be considered as compensatory. Conclusions: The lymphocytic microenvironment of CC in the presence of CSCs with the CD44+CD133+ immunophenotype seems to be more immunosuppressive, according to the increase in the local content of T regs and the decrease in MHC-ABC expression. Higher expression of PD-L1 on tumor cells and PD-1 on lymphocytes allows activation of the PD-1/PD-L1 interaction, which enhances the immunosuppressive and growth-stimulating properties of the tumor microenvironment, but at the same time, makes tumor cells adequate targets for immunotherapy with immune checkpoint inhibitors.