Aberrant miRNA expression response to UV irradiation in human liver cancer cells

microRNAs (miRNAs) are small, highly conserved, non-coding RNAs that regulate gene expression at the post‑transcriptional level. The expression of these small RNA genes is tightly regulated during development, differentiation and apoptosis of normal cells, however, they are often deregulated in various types of cancer. miRNA expression is also affected by cellular stress, including radiation and chemotherapy. The present study monitored the expression levels of several miRNAs by using the stem-loop real-time polymerase chain reaction (PCR) in HepG2 cells following ultraviolet (UV) radiation. Our data demonstrated that UV irradiation is able to induce alterations in miRNA expression levels in HepG2 cells. Among them, miR-26a, miR-34a and miR-146a were significantly upregulated, while the expression of miR-21 was significantly downregulated. Bioinformatics analysis of these significantly regulated miRNAs was discussed. The results also indicated that miRNAs may be part of the innate response mechanism of the cells to radiation injury, which provides a rationale for miRNA replacement therapy by using specific miRNAs that may function as tumor suppressor genes in several types of cancer.