Relationship between circulating tumor cells and ZEB1 expression in tumor cells in colorectal cancer.

e15509 Background: Intravasation and circulation of tumor cells involves active invasion of cells with an enhanced migration potential as a result of the epithelial-mesenchymal transition (EMT). The ZEB1 protein is one of the key regulators of this process. Our purpose was to evaluate the association between the amount of circulating tumor cells (CTCs) in the peripheral blood of patients with different stages of colorectal cancer and the expression of ZEB1 by tumor cells. 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. The numbers of CTCs were measured in the peripheral blood before surgery using the Veridex CellSearch system (Janssen). CTCs were registered taking into account morphological characteristics and expression of epithelial cell adhesion markers EpCAM, CD45, cytokeratins 8,18,19. The blood sample was evaluated according to the following criteria: 0 CTCs, 1-3 CTCs, and more than 3 CTCs. Tissues of surgically removed tumors were studied with IHC analysis using rabbit polyclonal anti-ZEB1 antibodies (Biorbyt Ltd.) diluted 1:200 and the Reveal Polyvalent HRP-DAB Detection System. The percentage and the intensity of staining were assessed: 0, 1+ weak, 2+ moderate, 3+ strong. ZEB1 expression was considered positive when staining was detected in more than 10% (cut-off) tumor cells with intensities of 2+ and 3+. Statistical analysis of results was performed in the Statistica 13.0 program (StatSoftInc., USA). Results: From 1 to 402 CTCs were determined in 62.9% cases (in 188 of 299 patients); CTCs were not registered in 37.1% cases (111 of 299). Positive ZEB1 expression was observed in 80.6% (241 of 299 patients), while the negative one was much more rare – 19.4% (58 of 299 patients). The rates of CTC detection significantly increased with the positive ZEB1+ expression, compared to the negative expression (75.1% vs. 12.1%). CTCs >3 were detected in the blood in 39.0% in ZEB1+ tumors, but not in ZEB1- tumors. 1-3 CTCs were observed 3 times more often in ZEB1+ tumors (36.1% vs. 12.1; p≤0.05). Conclusions: Statistically significant association was revealed between the epithelial-mesenchymal transition marker ZEB1 expression by tumor cells and the amount of CTCs in the peripheral blood (p < 0.001).