title: Different levels of p53 induced either apoptosis or cell cycle arrest in a doxycycline-regulated hepatocellular carcinoma cell line in vitro.
abstract: Induction of p53 gene expression in cancer cells can lead to both cell cycle arrest and apoptosis. To clarify whether the level of p53 expression determines the apoptotic response of hepatocellular carcinoma (HCC) cells, we assessed the effect of various levels of expression of p53 gene on a p53-deficient HCC cell line, Hep3B, utilizing a doxycycline (Dox)-regulated inducible p53 expression system. Our results showed that apoptosis was induced in HCC cells with high levels of p53 expression. However, lower level of p53 expression induced only cell cycle arrest but not apoptosis. Bax expression was up-regulated following high levels of p53 expression, while bcl-2 expression was not altered by the level of p53 expression. Moreover, p21 expression was observed in both high and low expression of p53. These results suggest the level of p53 expression could determine if the HCC cells would go into cell cycle arrest or apoptosis. Bax may participate, at least in part, in inducing p53-dependent apoptosis and the induction of p21 alone was able to cause cell cycle arrest but not apoptosis.
authors.affiliation: Department of Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China. paullai@cuhk.edu.hk
authors.forename: Paul B S
authors.initials: PB
authors.lastname: Lai
authors.forename: Tian-Yi
authors.initials: TY
authors.lastname: Chi
authors.forename: George G
authors.initials: GG
authors.lastname: Chen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D002999:Clone Cells; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004318:Doxycycline / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000473:pathology*; D013752:Tetracycline; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D013752:Tetracycline; D004318:Doxycycline