Abstract
Although death receptor 6 (DR6) is aberrantly expressed in certain cancer cell lines, its function, signaling pathway and potential clinical significance in tumor progression are not well characterized. We report here that knocking down DR6 in the mouse B16 cell line has no effect on B16 cell death in vitro but suppresses xenograft B16 tumor growth by preventing tumor blood vessel formation in vivo. Deficiency of DR6 changes cytokine expression and secretion; in particular, it inhibits the proinflammatory cytokine interleukin-6 (IL-6), which is able to induce the expression of the angiogenesis-related factors: vascular endothelial growth factor-A, platelet-derived growth factor-β, vascular endothelial growth factor-D and platelet-derived growth factor receptor-α. Further experiments demonstrate that DR6-dependent angiogenesis is involved in the IL-6/P38 MAPK and IL-6/STAT3 pathways. Our novel findings demonstrate for the first time that DR6 expression in B16 cells facilitates tumor growth by accelerating tumor angiogenesis. Moreover, these results suggest that DR6 is involved in three important intracellular pathways that lead to homeostatic angiogenesis in tumor growth.