LAUSR

OBJECTIVE Breast cancer (BC) is one of the primary causes of tumor-related female mortalities. Although in recent years, we have made great progress in the systemic therapy and earlier diagnosis for BC patients, recurrence or distant metastasis remains leading obstacles for the successful therapy of BC. Therefore, a comprehensive understanding of the molecular mechanism underlying the progression may be crucial in developing an effective strategy against BC. The current research aimed to explore the expressions, functions and molecular mechanism of microRNA-491 (miR-491) in BC. PATIENTS AND METHODS Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was performed to examine the level of miR-491 expression in 52 pairs of BC tissues and para-cancerous specimens, and the relation between miR-491 level and the clinical features of BC patient prognosis was analyzed. Transwell invasion and migration assays were conducted to determine whether miR-491 had effects on the regulation of BC metastasis. Potential target genes of miR-491 were found out using TargetScan to explore the molecular functions of miR-491 in inhibiting breast cancer cell invasion and migration. To elucidate the mechanism of TPX2 in suppressing cell invasion and migration medicated by miR-491in breast cancer, we further transfected TPX2 siRNAs into MCF-7 cells to delete endogenous TPX2, along with the transfections with miR-491 inhibitor into MCF-7 cell lines. RESULTS The findings demonstrated that miR-491 expressions were significantly decreased in BC tissues and cells. The miR-491 restoration suppressed the invasion and migration of BC cells. In addition, we identified the targeting protein for Xklp2 (TPX2) as a direct target of miR-491 in BC. The knockdown of TPX2 markedly reversed miR-491-medicated inhibition of cell invasion and migration in BC cell lines. CONCLUSIONS In short, all the results suggested that miR-491 functioned as a tumor suppressor by targeting TPX2 in BC and the miR-491 restoration may be an effective therapy for the BC treatment in the future.