microRNA-155 promotes the proliferation of prostate cancer cells by targeting annexin 7

Micro (mi)RNAs are a group of small non-coding RNA molecules that have been demonstrated to regulate the expression of genes involved in tumorigenesis. The relevance of microRNAs in the development, progression and prognosis of prostate cancer is not fully understood. miR-155 has been implicated in the induction of breast, lung and liver cancer, but its role in prostate cancer has not been investigated. In the present study, the biological function of miR-155 was investigated in prostate cancer for the first time, to the best of our knowledge. It was demonstrated that the expression of miR-155 was upregulated in prostate cancer tissues and cell lines as determined by quantitative reverse transcription-polymerase chain reaction. Furthermore, overexpression of miR-155 promoted cell proliferation, as indicated by MTT assay. Flow cytometric analysis demonstrated that inhibition of miR-155 induced cell cycle arrest and promoted apoptosis in prostate cancer cells. In addition, western blot analysis indicated that annexin (ANX)7 was significantly downregulated in prostate cancer tissues and cells. A luciferase reporter assay indicated that ANX7 was a target of miR-155, which suggested that miRNA-155 promoted the proliferation of prostate cancer cells by regulating ANX7 expression levels.