VIRMA Facilitates Triple-Negative Breast Cancer Progression via Increasing m6A-Dependent KIF15 Expression.

Abstract

Vir like N6-methyladenosine (m6A) methyltransferase associated protein (VIRMA) is associated with various tumors, but the specific role of VIRMA in triple-negative breast cancer (TNBC) and the mechanisms are still unclear. Thus, in this study, in addition to the effect of VIRMA on TNBC, the underlying mechanisms were also explored. In vitro, VIRMA expression was detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot; VIRMA lentiviral overexpression vector (LV-VIRMA) and lentiviral vector connected with the shRNA targeting VIRMA (LV-shVIRMA) were constructed to explore the functional role of VIRMA; RNA immunoprecipitation and qRT-PCR were performed to assess the relationship between VIRMA and kinesin family 15 (KIF15). In vivo, female Balb/C mice (n = 6) were subcutaneously injected with TNBC cells transfected with LV-shRNA + LV-NC (negative control), LV-shVIRMA + LV-NC, and LV-shVIRMA + LV-KIF15, tumor volume, weight and immunohistochemistry staining of Ki-67 were employed to assess breast tumor growth; immunohistochemistry of VIRMA and KIF15 were performed to examine VIRMA and KIF15 expression in breast tumor tissues. Compared to normal breast epithelial cells, VIRMA was increased in TNBC cells (p < 0.01 and p < 0.001). LV-VIRMA elevated proliferation, metastasis and invasion of TNBC cells in comparison with LV-NC (p < 0.001), while VIRMA knockdown resulted in the opposite effects in comparison with LV-shRNA NC (p < 0.01 and p < 0.001). Also, compared to LV-shRNA NC, LV-shVIRMA downregulated KIF15 expression by reducing KIF15 mRNA stability (p < 0.05 and p < 0.001), which was dependent on m6A. Furthermore, compared to LV-shVIRMA + LV-NC, LV-shVIRMA + LV-KIF15 not only reversed the reduced proliferation, metastasis and invasion of TNBC cells (p < 0.05, p < 0.01, and p < 0.001), but also reversed the decreased tumor weight and volume (p < 0.05, p < 0.01, and p < 0.001). The above results indicated that VIRMA promoted TNBC progression by upregulating m6A-dependent KIF15 expression, providing a better understanding of the pathogenesis of TNBC.