Vascular endothelial growth factor promotes cancer stemness of triple-negative breast cancer via MAPK/ERK pathway

Abstract

To investigate the role of vascular endothelial growth factor (VEGF) in regulating triple-negative breast cancer (TNBC) stem cells and the possible pathways involved in this regulatory mechanism. The Oncomine database, UALCAN database and Human Protein Atlas (HPA) database were used to analyze the expression of VEGF in breast cancer and its association with the molecular subtypes and prognosis of breast cancer. Sphere formation assay was carried out to examine the effects of hVEGF165 on sphere formation ability of TNBC MDA-MB-231 cell line; Western blotting and RT-qPCR were performed to detect the expression of the tumor stem cell markers including CD44, c-Myc, Nanog, and ALDH1 and the activation of the related pathways. Data from the online databases all showed a significant increase of VEGF expression in breast cancer tissues than in the adjacent tissues (P < 0.0001), and its expression level was associated with the molecular subtypes of breast cancer. Specifically, the expression of VEGF was markedly higher in TNBC than in other subtypes of breast cancer. Survival analysis showed that breast cancer patients with a high VEGF expression had a significantly shortened overall survival (P < 0.0001). In the cell experiments, the sphere formation ability of MDA-MB-231 cells was significantly enhanced after treatment with hVEGF165 (P=0.0029). Compared with the monolayer cells, MDA-MB-231 spheres showed significantly increased expressions of VEGF, NRP-1, CD44, Nanog and c-Myc. Treatment with hVEGF165 resulted in significant time-dependent up-regulation of the expressions of CD44, c-Myc, Nanog and ALDH1 and down-regulation of CD24 expression in the cells. The results of Western blotting demonstrated that treatment with hVEGF165 caused significant activation of the ERK/MAPK pathway in MDA-MB-231 cells. VEGF promotes cancer stemness of triple-negative breast cancer possibly through the ERK/MAPK pathway.