Effect of connective tissue growth factor on hypoxia-inducible factor 1α degradation and tumor angiogenesis

Abstract

Background: Connective tissue growth factor (CTGF) inhibits the metastatic activity of human lung cancer cells in a mouse model; however, the mechanism of this modulation is unclear. We investigated the role of angiogenesis in this process. Methods: CL1-5 and A549 human lung adenocarcinoma cells were stably transfected with vectors containing CTGF or hypoxia-inducible factor (HIF) 1α or with vector controls. Transfected cells were injected into nude mice (n = 10 per group), and tumor growth, metastasis, and mouse survival were measured. Excised xenograft tumors and primary human lung adenocarcinomas (n = 24) were subjected to immunohistochemistry with antibodies to the endothelial cell marker CD31 and to CTGF. Expression of HIF-1α and vascular endothelial growth factor (VEGF) A was assessed in vitro by using reporter gene assays. Cells were transiently transfected with HIF-1α mutant and antisense arrest-defective 1 protein (ARD-1), and HIF-1α acetylation was assayed by immunoprecipitation. All statistical tests were two-sided. Results: Xenograft tumors derived from CTGF transfectants grew more slowly than those from control-transfected cells and had reduced expression of HIF-1α and VEGF-A, vascularization (as assessed by CD31 expression), and metastasis (all P