THBS1 promotes angiogenesis and accelerates ESCC malignant progression by the HIF‐1/VEGF signaling pathway

Abstract Previously, we demonstrated that the expression of THBS1 is increased in esophageal squamous cell carcinoma (ESCC) tissues and is correlated with lymph node metastasis and poor prognosis, indicating that THBS1 might be a candidate oncogene in ESCC. In this study, we future studied the specific role of THBS1 in ESCC and its molecular mechanism. Silencing THBS1 expression resulted in inhibition of cell migration and cell invasion of ESCC cells, the decrease of colony formation and proliferation. Tube formation of human umbilical vein endothelial cells (HUVECs) in vitro was decreased when cultured with conditioned medium from THBS1‐silenced cells. The expression of CD31, a marker for blood vessel endothelial cells, was decreased in tumor tissues derived from THBS1‐silenced tumors in vivo. Silencing THBS1 leaded the decreased of hypoxia‐inducible factor‐1α (HIF‐1α), HIF‐1β, and VEGFA protein. The expression of p‐ERK and p‐AKT were declined in HUVECs following incubation with conditioned medium from THBS1‐silenced ESCC cells compared conditioned medium from control cells. Furthermore, the treatment with bevacizumab boosted the decrease of the p‐ERK and p‐AKT levels in HUVECs incubated with the conditioned medium from THBS1‐silenced ESCC cells. THBS1 silencing combined with bevacizumab blocked VEGF, inhibited to the tube formation, colony formation and migration of HUVECs, which were superior to that of bevacizumab alone. We presumed that THBS1 can enhance HIF‐1/VEGF signaling and subsequently induce angiogenesis by activating the AKT and ERK pathways in HUVECs, resulting in bevacizumab resistance. THBS1 would be a potential target in tumor antiangiogenesis therapies.