miR‐135b promotes proliferation and metastasis by targeting APC in triple‐negative breast cancer

Abstract Triple‐negative breast cancer (TNBC) is the most aggressive breast cancer subtype. The aim of our study was to investigate the functional role of microRNA‐135b (miR‐135b) in TNBC. A real‐time polymerase chain reaction assay was used to quantify miR‐135b expression levels in 90 paired TNBC tissue and adjacent normal tissue samples. Wound‐healing and transwell assays were performed to evaluate the effects of miR‐135b expression on the migration and invasion of TNBC cells. Luciferase reporter and western blot analyses were used to verify whether the mRNA encoding APC is a major target of miR‐135b. In the current study, we found that miR‐135b was highly expressed in TNBC tissue and cells, and the expression levels were correlated with lymph node status and TNM stage. In TNBC cells, the ectopic expression of miR‐135b promoted cell proliferation and invasion in vitro. In addition, our study proved that the overexpression of miR‐135b significantly suppressed APC expression by targeting the 3′‐untranslated region of APC, whereas enhanced APC expression could partially abrogate the miR‐135b‐mediated promotion of carcinogenic traits in TNBC cells. Taken together, our study demonstrated that miR‐135b expression promoted the proliferation and invasion of TNBC by downregulating APC expression, indicating that miR‐135b may serve as a promising target for the treatment of TNBC patients.