Background: 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.
Methods: 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.
Results: 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).
Conclusions: The above results indicated that VIRMA promoted TNBC progression by upregulating m6A-dependent KIF15 expression, providing a better understanding of the pathogenesis of TNBC.
Keywords: KIF15; TNBC; VIRMA; m6A.