MicroRNA-335 inhibits bladder cancer cell growth and migration by targeting mitogen-activated protein kinase 1

The abnormal expression of microRNAs (miRs) as oncogenes or tumor-suppressor genes has been widely investigated in various tumor types. However, the roles of miR-335 in bladder cancer cells have remained elusive. The aim of the present study was to assess the expression of miR-335 in bladder cancer as well as the effects of miR-335 on bladder cancer cell proliferation, metastasis and apoptosis. PCR and western blot analyses revealed that miR-335 was significantly downregulated in bladder cancer tissues, and low levels of miR-335 were associated with more aggressive phenotypes of bladder cancer. Overexpression of miR-335 in T24 cells inhibited cell proliferation and induced apoptosis as indicated by an MTT assay and flow cytometric analysis, respectively. Furthermore, overexpression of miR-335 significantly suppressed cell migration, as indicated by a Transwell assay. The expression of mitogen-activated protein kinase (MAPK) 1 was decreased after overexpression of miR-335, indicating that MAPK1 may be a target gene of miR-335. In addition, silencing of MAPK1 inhibited the proliferation and migration of bladder cancer cells. In conclusion, the results of the present study demonstrated that miR-335 was significantly downregulated in bladder cancer, and may act as a tumor suppressor through repression of MAPK1.