Human papillomavirus type 16 E6 and E7 proteins inhibit differentiation-dependent expression of transforming growth factor-beta 2 in cervical keratinocytes

Infection with high-risk human papillomaviruses (HPVs) represents a major r isk factor for the development of cervical cancer. The HPV-16 E6 and E7 pro teins are highly expressed in differentiating keratinocytes, where they ina ctivate the p53 and retinoblastoma (pRb) proteins, two important transcript ional regulators. We have used cDNA expression arrays to identify global al terations in gene expression induced by E6 and E7 in differentiating cultur es of human cervical keratinocytes. We show that E6 and E7 decrease express ion of TGF-beta 2 mRNA and alter expression of multiple TGF-beta-responsive genes involved in cell cycle regulation, apoptosis, and tissue remodeling. E6 and E7 inhibited expression of TGF-beta 2 RNA 7-fold (relative effectiv eness, E6/E7 > E6 > E7 > control) and decreased secretion of biologically a ctive TGF-beta 2 by 70-80% (reduced from 70 to 10 pg/10(6) cells/24 h), Dow nregulation occurred through p53- and pRb-dependent pathways. In contrast, E6 and E7 did not alter expression of TGF-beta 1 and TGF-beta 3. Down-regul ation of TGP-PZ was biologically relevant because the addition of recombina nt cytokine (10-200 pg/ml) to E6/E7-expressing cells restored expression of TGF-beta-responsive genes, inhibited growth of keratinocytes, and decrease d immortalization by E6 and E7, These results suggest that TGF-beta 2- and TGF-beta-responsive genes are important targets for the HPV-16 E6 and E7 on coproteins in differentiating cervical keratinocytes.