Effects of Chemotherapy for Metastatic Colorectal Cancer on the TGF-β Signaling and Related miRNAs hsa-miR-17-5p, hsa-miR-21-5p and hsa-miR-93-5p.

Metastatic colorectal cancer (mCRC) patients are treated with standard chemotherapeutic drugs in the form of FOLFOX and FOLFIRI regimens. There are no reliable markers that could predict response to chemotherapy for mCRC. TGF-β signaling which interacts with microRNA (miRNA) network has important roles in tumor progression and chemotherapy resistance, thus the interplay between TGF-β signaling and miRNAs could be crucial for treatment response. The aim of this study was to analyze the effect of chemotherapy for mCRC on TGF-β signaling and related miRNAs. Hsa-miR-17-5p, hsa-miR-21-5p and hsa-miR-93-5p were selected out of 316 miRNAs with multiple targets within the TGF-β signaling by in silico analysis. SW620 cells were treated with chemotherapeutic drugs for mCRC for 1, 3 and 6 days and expression of selected miRNAs, PAI-1, CDH1 and VIM was measured. Expression of TGF-β signaling-related hsa-miR-17-5p, hsa-miR-21-5p and hsa-miR-93-5p was time-dependently altered in SW620 cells treated with chemotherapeutics for mCRC. The expression of hsa-miR-93-5p remained downregulated after 6 days under combined treatments FOX and FIRI as well as the hsa-miR-17-5p expression under FIRI. Chemotherapy regimens for mCRC increased expression of a major TGF-β signaling target gene PAI-1, independently of the selected miRNAs expression. These treatments also increased the expression of epithelial-mesenchymal transition (EMT) markers CDH1 and VIM on day 3 resulting in decrease of mesenchymal-like characteristics. However, their expression returned close to basal level on day 6. In conclusion, after initial response to chemotherapeutic drugs SW620 cells start to return close to the basal mesenchymal state while the long-term downregulated expression pattern of hsa-miR-93-5p and hsa-miR-17-5p makes them candidates worth testing as biomarkers for monitoring combined chemotherapeutic treatments therapy response in mCRC patients.