The growth characteristics of a newly established cell line, Hep40, derived from a human hepatoma are described. An absolute requirement was found for serum to mediate cell growth. Neither EGF, TGF-α, nor HGF altered cell growth in the presence or absence of serum. A partial suppression of cell growth was achieved by several TGF-β family proteins. Affinity crosslinking gels using 125I-labeled TGF-β showed a significant decrease in the TGF-β cell-surface type II receptor in Hep40 cells, compared to the TGF-β-sensitive Hep3B cell line. However, growth could be completely suppressed by addition of vitamins K to the culture medium in both Hep40 and several other hepatoma cell lines. Growth suppression by vitamins K was accompanied by an increased level of transcripts for c-myc, c-jun, and prothrombin genes, in contrast to the actions of TGF-β1 protein, which caused a decrease in the level of c-myc transcripts. These data show that this new human hepatoma cell line has partial resistance to growth inhibition by TGF-β with a unique TGF-β receptor defect. However, growth was completely suppressed by vitamins K. The differing gene expression patterns in response to TGF-β as compared to vitamin K suggest that these two growth inhibitors act through differing pathways. © 1995 Wiley-Liss Inc.