MicroRNAs (miRNAs) have recently taken center stage in the field of human molecular oncology. Most of the chemotherapeutics are able to interfere with nucleic acid metabolism and gene expression. The purpose of this study was to determine how 5-fluorouracil (5-FU) and oxaliplatin (L-OHP) modify the expression profiles of miRNAs in HCT-8 and HCT-116 colon cancer cells and whether the pharmacodynamic mechanisms of the chemotherapeutics could rely in part on their influence on miRNA expression. The expression profiles of miRNAs were determined using a miRNA microarray containing 856 human miRNA probes. The expression of selected miRNAs was then validated by real-time RT-PCR. Fifty-six up- and 50 down-regulations of miRNA expression with statistical significance were identified in colon cancer cells following exposure to 5-FU or L-OHP compared to matched control cells. The down-regulations of miR-197, miR-191, miR-92a, miR-93, miR-222 and miR-1826, whose expression was significantly down-regulated in both cell lines after the treatment of one drug or in one cell line following exposure to either drug, were further validated. Analysis of the relevant literature indicated that, in line with the tumor suppressive activity of 5-FU and L-OHP, the six down-regulated miRNAs might function as oncogenes due to their overexpression in cancers, and some of them correlated with the poor prognosis and treatment-resistance of cancer. In conclusion, we identify the modification of miRNA expression profiles in colon cancer cells following exposure to 5-FU and L-OHP, and our results indicate that their pharmacodynamic mechanisms could rely in part on their influence on the down-regulated miRNA expression. Further studies are needed to determine whether these miRNAs and their target genes might potentially provide for novel molecular markers and act as novel targets for treatment by interference.

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