The epidemiologic association of human papillomavirus (HPV) infection with dysplasia and cervical cancer is well established. Transforming growth factor beta 1 (TGF beta 1) has regulatory effects on a broad spectrum of cell types and is a growth inhibitory protein for epithelial cells. To examine the phenotype of experimentally generated, HPV-11 transformed human tissues, we looked at expression of TGF beta 1 and a number of proliferation-enhancing molecules which are known to be regulated by TGF beta 1, including bcl-2, c-myc, c-Ha-ras, c-jun and NFkB. HPV-11 transformed xenografts showed up-regulation of TGF beta 1 expression and down-regulation of the expression levels of bcl-2, c-myc, c-Ha-ras, c-jun and NFkB. These results suggest that TGF beta 1 may exert antiproliferative effects on HPV-11 transformed papillomas by down-regulating different proliferation-enhancing molecules.