Downregulation of MiR-302b is Associated with Poor Prognosis and Tumor Progression of Breast Cancer

Background: MicroRNAs (miRNAs) are well known to play crucial role in various types of cancers, including breast cancer (BC).

Methods: The present study aimed to investigate the expression, clinical value, and functional role of miR-302b in BC. The expression level of miR-302b was determined by quantitative real-time polymerase chain reaction (qRT-PCR). The clinical value of miR-302b in BC prognosis was calculated via Kaplan-Meier survival analysis and Cox regression analysis. Cell experiments were applied to investigate the functional role of miR-302b in BC.

Results: miR-302b was significantly downregulated in BC tissues and cell lines compared to the corresponding controls (all P < 0.01). Notably, the expression of miR-302b was significantly associated with lymph node metastasis and TNM stage (all P < 0.05). Patients with lower miR-302b expression had shorter survival time than those with higher miR-302b expression (log-rank P = 0.002). Furthermore, miR-302b expression and TNM stage were proven to be independent prognostic factors for BC. Overexpression of miR-302b inhibited BC cell proliferation, migration, and invasion in BT549 and MCF-7 cell lines, while silence of miR-302b exhibited an opposite effects on BC cells (all P < 0.05). RUNX2 was determined to be the target gene of miR-302b.

Conclusions: The present study suggests that miR-302b functions as a tumor suppressor in BC and inhibits the tumor progression of BC via targeting RUNX2. Downregulation of miR-302b might be a significant prognostic factor for poor survival in BC patients.