Persistent and remodeling hepatic preneoplastic lesions present differences in cell proliferation and apoptosis, as well as in p53, Bcl‐2 and NF‐κB pathways

Abstract

During rat hepatocarcinogenesis preneoplastic lesions (PNL) emerge which may persist (pPNL) and be sites of progress to cancer or suffer remodeling (rPNL) tending to disappear. Cellular and molecular mechanisms involved in both phenotypes are not sufficiently elucidated. pPNL and rPNL cellular proliferation and apoptosis were evaluated in rats submitted to the resistant hepatocyte (RH) model, and an adjusted growth index (AGI) was established. p53, Bcl-2, and NF-kappaB p65 subunit expression was evaluated by immunohistochemistry in pPNL and rPNL. p65 expression and NF-kappaB activation was evaluated by Western blot assays in whole livers. A lower number of BrdU-stained hepatocyte nuclei/mm(2) and higher number of apoptotic bodies (AB) per mm(2) were observed in remodeling compared to pPNL. Cytoplasmic p53 accumulation is related to increased hepatocarcinoma malignancy. We observed that 71.3% pPNL and 25.4% rPNL (P < 0.05) presented p53 staining in the cytoplasm. Similarly, 67.7% pPNL and 23.1 % rPNL (P < 0.05) presented increased Bcl-2 staining. Thirty-two percent pPNL and 15.6% rPNL (P < 0.05) presented p65 staining. Compared to normal rats, increase (P < 0.05) of hepatic p65 expression and NF-kappaB activation in rats submitted to the RH model was observed. In agreement to previous studies hepatic pPNL and rPNL differ regarding cell proliferation and apoptosis. Moreover, persistence and remodeling involve differences in p53, Bcl-2, and NF-kappaB pathways. These data point to molecular pathways that may direct preneoplastic lesions to spontaneously regress or to progress to cancer. J. Cell. Biochem. 103: 538-546, 2008. (c) 2007 Wiley-Liss, Inc.

Chemoprevention of rat hepatocarcinogenesis with histone deacetylase inhibitors: Efficacy of tributyrin, a butyric acid prodrug

“…30 In addition, a lower labeling index and higher apoptotic index were observed in rPNL compared to pPNL. 20,31,32 Interestingly, in the present study TB inhibited the development of persistent GST-P positive PNL, considered to be precursors of HCC. 33 In addition, increased % remodeling in TB group indicates that this compound modulates remodeling of GST-P positive PNL.…”

“…52 In our study we confirmed our previous results showing that cytoplasmic p53 accumulation is more frequent in pPNL than in rPNL. 20 TB reduced the percentage of pPNL with cytoplasmic p53 accumulation. This suggests that it acted on PNL with a more aggressive phenotype and higher probability to progress to HCC.…”

“…In hepatocarcinogenesis, alterations in p53 pathways have been reported. 20 Acetylation has been shown to be an important element in p53 functionality. 51 It will be important to determine if TB affects p53 acetylation in the RH model.…”

“…Results were expressed as % of tPNL, pPNL and rPNL positive for cytoplasmic p53 staining. 20 Specificity of staining was controlled by subtracting the primary antibody or by substituting it for nonimmunized goat serum. In all cases this resulted in absence of staining.…”

“…For equal loading control of the relative amount of the protein of interest, western blots were normalized with previous staining of the nitrocellulose membrane with Coomassie blue. 20,22,26 P21 western blot analysis Samples of total protein extracts (50 lg) were separated by electrophoresis in 15% denaturing polyacrylamide gel (SDS-PAGE). Proteins were then transferred from the gel onto a nitrocellulose membrane.…”