Anti-cancer drugs reactivate tumor suppressor miR-375 expression in tongue cancer cells.

Head and neck cancer is one of the deadliest malignant diseases and chemotherapy is a common treatment option. Despite the development of chemotherapies for several decades, how these drugs affect the dynamics of gene regulation is still largely unknown. In our previous study, miR-375 was shown to be underexpressed in oral cancers and thus unable to serve as a tumor suppressor microRNA to regulate certain putative oncogenes. In this study, we found that common anti-cancer drugs reactivated miR-375 in tongue cancer cells. Incubation of tongue cancer cells CAL 27 and SCC-25 in medium containing doxorubicin, 5-fluorouracil, trichostatin A, or etoposide significantly increased the expression of miR-375 and its primary transcript pri-miR-375. The dose- and time-dependent effects of doxorubicin in CAL 27 were demonstrated by miR-375 increases in response to the drug. Significant suppression of pri-miR-375 expression was observed in human tongue cancer specimens and this decrease was more prominent in advanced stage tumors. Bioinformatics from four publicly available mRNA microarray data sets suggested that these candidate miR-375 targets are mainly involved in cancer biology, indicating that these targets are likely to be suppressed via miR-375 due to the treatment with these drugs. Together, our data suggest that the four anti-cancer drugs examined in this study induce the expression of tumor suppressor miR-375 in tongue cancer.