Vitamin D3 upregulated protein 1 suppresses TNF-α–induced NF-κB activation in hepatocarcinogenesis

Abstract

Vitamin D(3) upregulated protein 1 (VDUP1) is a candidate tumor suppressor, the expression of which is dramatically reduced in various tumor tissues. In this study, we found that VDUP1 expression is suppressed during human hepatic carcinogenesis, and mice lacking VDUP1 are much more susceptible to diethylnitrosamine-induced hepatocarcinogenesis compared with wild type mice. VDUP1-deficient tumors proliferated significantly more than wild type tumors and had corresponding changes in the expression of key cell cycle regulatory proteins. In addition, the hepatomitogen-induced response was associated with a considerable increase in the release of TNF-alpha and subsequent enhancement of NF-kappaB activation in VDUP1-deficient mice. When cells were treated with TNF-alpha, the VDUP1 level was markedly reduced, concomitant with elevated NF-kappaB activation. Furthermore, the overexpression of VDUP1 resulted in the robust suppression of TNF-alpha-activated NF-kappaB activity via association with HDAC1 and HDAC3. These results indicate that VDUP1 negatively regulates hepatocarcinogenesis by suppressing TNF-alpha-induced NF-kappaB activation.