MicroRNA-496 inhibits triple negative breast cancer cell proliferation by targeting Del-1

Del-1 has been linked to the pathogenesis of various cancers, including breast cancer. However, the regulation of Del-1 expression remains unclear. We previously reported the interaction between microRNA-137 (miR-137) and the Del-1 gene. In this study, we investigated miR-496 and miR-137 as regulators of Del-1 expression in triple negative breast cancer (TNBC). Del-1 mRNA and miR-496 were measured by quantitative PCR in breast cancer cells (MDA-MB-231, MCF7, SK-BR3, and T-47D) and tissues from 30 patients with TNBC. The effects of miR-496 on cell proliferation, migration, and invasion were determined with MTT, wound healing, and Matrigel transwell assays, respectively. In MDA-MB-231 cells, miR-496 levels were remarkably low and Del-1 mRNA levels were higher than in other breast cancer cell lines. Luciferase reporter assays revealed that miR-496 binds the 3'-UTR of Del-1 and Del-1 expression is downregulated by miR-496 mimics. Furthermore, miR-496 inhibited the proliferation, migration, and invasion of MDA-MB-231 cells. The effects of miR-496 on cell proliferation were additive with those of miR-137, another miRNA that regulates Del-1 expression. Moreover, in the 30 TNBC specimens, miR-496 was downregulated (P < .005) and the levels of Del-1 in the plasma were significantly elevated as compared with in normal controls (P = .0142). The Cancer Genome Atlas (TCGA) data showed the correlation of miR-496 expression with better overall survival in patients with early TNBC. In in silico and in vitro analyses, we showed that Del-1 is a target of miR-496 in TNBC and thereby affects cancer progression. Our findings suggest that miR-496 and miR-137 additively target Del-1 and act as modulating factors in TNBC. They are potentially new biomarkers for patients with TNBC.