it is interesting that HuH 6 cells miss inside the anti apoptotic factor Bcl 2, while HepG2 cells have a low level of this factor. The finding that z VAD fmk, an over-all inhibitor of caspases, completely suppressed the effect of butyrate on unphospho pRb clearly suggests that the decrease in the amount of this form is set by the cleavage of the protein by caspases. Based on Chau and Wang, we advance the theory that the cleavage of pRb could cause the activation of apoptotic genes and, therefore, the speed of apoptosis observed throughout the second day of treatment. Our results suggest that the dephosphorylation of pRb might partly be caused natural product library by the decrease in the amounts of cyclins D and E, two factors required for the activity of CDK4 and CDK2, respectively, that take part in the phosphorylation of pRb during the cell cycle 29]. Also, the fall in cyclin contents appeared to be a consequence of the activation of caspases, because the addition of z VAD fmk or z DEVD fmk avoided the effect of butyrate on cyclins D and E. But, on the phosphorylated form of pRb since z VAD fmk only partially paid down the influence of butyrate, we conclude that other components different from the activation of caspases may exert a task in the dephosphorylation of pRb. It’s well known that the proteins of Bcl Metastatic carcinoma 2 family use significant role in the fate of cells, since some members of this family favor cell success while others take part in the induction of apoptosis. Survival-of hepatoma cells is most probably assured by the pres-ence in both HuH 6 cells and HepG2 cells of large amounts of Bcl XL, a strong anti apoptotic factor, as the professional apoptotic factor Bcl Xs, one other isoform developed from your Bcl X gene, is undetectable in both cell lines. Our results show that treatment of HuH 6 cells with butyrate triggers remarkable MAPK activity modifications in the amounts of Bcl X isoforms. Bcl XL was substantially reduced, an effect that was clearly observed during the second day of therapy. This event was a consequence of activation of caspases and particularly of caspase 3, since the addition of caspase inhibitors prevented the effect of butyrate on Bcl XL. Differently, in handled cells we observed during the second day of treatment-a remarkable upsurge in the power of the 21 kDa group, that has been identified as Bcl XS, an effective apoptotic issue. Since examination of Bcl X mRNA species by RT PCR showed that butyrate increased Bcl Xs transcripts, this effect almost certainly depended on the increased expression of the Bcl X gene. The contemporaneous increase in the Bcl XL transcript can be viewed as a compensatory response to the influence induced by butyrate.