In this study we separated weakly acidic phenolic components from other neutral, acidic and basic components of tobacco smoke condensate (TSC) and observed that phenolic fraction of TSC significantly increased the number of colonies of promotion-sensitive JB6 Cl41 cells that showed anchorage-independent growth on soft agar in response to BPDE (an ultimate carcinogen produced by metabolic activation of the PAH benzo[a]pyrene). Anchorage-independent cell growth is indicative of cell transformation resulting in acquisition of tumorigenic potential. In order to understand the underlying mechanism by which TSC phenolic fraction potentiates BPDE-induced tumorigenicity, we examined its effect on the activation of two transcription factors AP-1 and NF-κB which are known to be influenced by established tumor promoter TPA. BPDE treatment caused induction of both AP-1 and NF-κB activity as determined by luciferase reporter assay and only NF-κB induction in response to BPDE was significantly attenuated by TSC phenolic fraction whereas AP-1 induction remains unaltered. Attenuation of NF-κB activation by TSC phenolic fraction was associated with significant decrease of intracellular PKC substrate phosphorylation in BPDE treated cells. Non-specific PKC inhibitors staurosporine and bisindolylmaleimide II as well as inhibitors specific to conventional PKCs (Go6976) and PKC-δ (rottlerin) attenuated NF-κB activation in BPDE treated cells to a varying degree indicating a possible link between PKC down-regulation and the attenuation of NF-κB activity by TSC phenolic fraction. Treatment of cells with PKC inhibitors also potentiated anchorage-independent growth of BPDE treated cells on soft agar. Our data suggest a possible role of PKC down-regulation in potentiation of BPDE-induced tumorogenicity by TSC phenolic fraction.