The epidemiologic association of human papillomavirus (HPV) infection with dysplasia and cervical cancer is well established. Transforming growth factor beta 1 (TGF beta 1) is a growth inhibitory protein for epithelial cells. To examine the phenotype of HPV-transformed cells, we examined expression of TGF beta 1 and a number of cellular proliferation-enhancing molecules which are known to be regulated by TGF beta 1, including bcl-2, c-jun and NFkB. Previous studies had identified significant induction of TGF beta 1 and concomitant down-regulation of other growth stimulatory molecules in experimental papillomas. We used HPV-16 and -18 transformed cell lines. The HPV-16 transformed cells showed down-regulation of bcl-2 and NFkB as well as NFkB function upon TGF beta 1 treatment. The results suggest that TGF beta 1 may exert antiproliferative effects on some HPV-transformed cells by down-regulating expression and function of different proliferation-enhancing molecules. It is uncertain if this function is virus type specific and/or related to state of tumor cell progression.