Amount of cancer stem cells in tumors of patients with ovarian cancer with different responses to platinum-containing chemotherapy.

e17527 Background: Resistance to chemotherapy is a complex problem in the treatment of patients with ovarian cancer (OC), and this phenomenon is associated, among other things, with the presence of cancer stem cells (CSCs). The purpose of the study was to determine the amount of CSCs in tumors of OC patients with different responses to chemotherapy they receive. Methods: Samples of ovarian tumors were obtained from 100 patients (aged 29-79 years) with advanced ovarian cancer stage IIIC-IV with/without ascites. All patients recruited in 2016-2020 received standard combination treatment with surgery and platinum-containing polychemotherapy (Pt CT). Based on the results of neoadjuvant Pt CT, patients were divided into groups: patients with stabilization or progression–group 1 “without effect”; patients with complete/partial regression–group 2 with positive effect. All patients gave their informed consent for the study. Cell suspension obtained from the tumor fragments was processed using monoclonal antibodies labeled with various fluorochromes: CD45-APC-Cy7, CD44-FITС, CD133–РЕ according to the manufacturer's instructions (BD, USA). The percentage of CSCs was determined using the FACS Canto II flow cytometer (BD, USA). The amount of cells with CSC markers (CD44 + , CD133 + , CD44 + CD133 + ) was calculated as a percentage from the total amount of CD45 - -cells. Statistics: STATISTICA 13 (StatSoftInc., USA). Results were presented as Me (LQ; UQ). The significance of differences was assessed using the Mann-Whitney test (the differences were considered significant at p<0.05). Results: The amount of CD45 - _ cells, as well as CD45 - CD44 + cells, in OC tumors did not differ between patients of groups 1 and 2: 79.0 (72.1; 85.9) vs. 82.8 (76.7; 89.0), and 6.2 (3.3; 9.1) vs. 6.6 (3.5; 9.8), respectively. The percentage of cancer cells with the CD45 - CD133 + phenotype in group 2 was significantly lower than in group 1: by 52% (p≤0.05), 3.2 (2.4; 3.9) vs. 6.7 (3.8; 9.6), respectively. The amount of CD45 - CD44 + CD133 - CSCs in tumors in group 1 was lower than in group 2: by 82% (p≤0.05), 0.6 (0.3; 0.7) vs. 3.3 (1.8; 4.7), respectively. Conclusions: The results demonstrated certain differences in the distribution of CSCs in tumors of OC patients with different sensitivity to chemotherapy, which may be one of the factors determining the treatment outcomes.