Effect of MiR-137 and MiR-496 on Del-1 and triple negative breast cancer progression.

e23058 Background: Although Del-1 was recently proposed as a new biomarker for early breast cancer in our previous studies, the mechanisms of Del-1 expression are barely understood. In the current study, we selected two microRNAs (miR-137 and - 496), potentially affecting Del-1 expression in breast cancer and examined their impact on Del-1 expression in a variety of breast cancer cell lines to identify their potential role in Del-1 expression and thereby breast cancer development or progression. . Methods: Del-1 mRNA and miR-137/– 496 levels were measured by qRT-PCR among breast epithelial (MCF10A) and cancer cells (MDA-MB-231, MCF7, SK-BR3 and T-47D). The effects of miR-137/– 496 on cell proliferation and invasion were detected using MTT, wound healing and Transwell assays. Furthermore, luciferase reporter assay was used to identify the direct regulation of Del-1 by miR-137 or – 496 in MDA-MB-231 cells. Plus, we analyzed the expressions of miR-137 or – 496 and Del-1 mRNA from 20 patients with triple negative early breast cancer. Results: miR-137 and – 496 levels were low in all breast cancer cell lines. As Del-1 mRNA expression was remarkably higher in MDA-MB-231 compared to the other breast cancer cell lines, further functional analyses were done with MDA-MB-231 representing triple negative breast cancer subtype. Both miR-137 and miR-496 were revealed to directly bind at the 3’-UTR of Del-1. Del-1 by Luciferase reporter assay and Del-1 expression was upregulated by inhibitors and reversed by both mimics of both miR-137 and miR-496. Furthermore, both miR-137 and miR-496 were also demonstrated to inhibit cell proliferation, migration and invasion of MDA-MB-231, suggesting that these miRNAs affect cancer progression via Del-1. MiR-137 and miR-496 were remarkably down-regulated in 7 out of 12 triple negative breast cancer tissues, in particular with high Ki67 and high histologic grade. Conclusions: Although Del-1 was recently introduced as a new biomarker for triple negative breast cancer, the mechanisms of Del-1 expression were barely identified. The current study firstly demonstrated that microRNA 137 and 496 are involved in Del-1 regulation by binding at Del-1 gene, affecting cancer progression by altering Del-1 expression.