Retinoblastoma and p 53 tumor suppressor genes in human hepatoma cell lines

Abstract

We analyzed the status of retinoblastoma and p53 genes in 10 human hepatoma cell lines. Polyclonal anti-peptide antibodies generated against peptides homologous to COOH-terminal and leucine-zipper domains of the retinoblastoma protein allowed us to identify two cell lines (Hep 3B and FOCUS) with abnormal expression. The same cell lines have both lacked p53 expression. In contrast to the retinoblastoma gene, the expression of the p53 gene was abnormal in six additional cell lines. Indeed, only the Hep G2 hepatoblastoma cell line (and its derivative Hep G2/2215) appeared to have normal p53 and retinoblastoma gene expression. Our studies indicate that p53 abnormalities are common but retinoblastoma gene aberrations are rare in human hepatoma cell lines.

FOXO transcription factor-dependent p15INK4b and p19INK4d expression

“…Actually, LY294002 slightly arrested cell cycle at G 1 phase in 293T cells (Figure 1e). In contrast, LY294002 drastically induced G 1 arrest in HepG2, Raji and WT MEF cells (Figures 1e and 6), which contain normal Rb as a tumor suppressor gene product (Puisieux et al, 1993;Wells et al, 2003). These findings suggest that LY294002-mediated G 1 arrest is induced by Rb-dependent and -independent pathways.…”

Expression of human p53 requires synergistic activation of transcription from the p53 promoter by AP-1, NF-κB and Myc/Max

“…To con®rm our results in cells that are free from viral sequences and express p53 wt, we examined transcription from the hp53-promoter in exponentially growing HepG2 hepatoma cells (Bressac et al, 1990;Puisieux et al, 1993;Ho et al, 1996;Jiang et al, 1996). As for HeLa cells, transcription from the hp53 promoter was suppressed to nearly control levels when the AP-1 or the NF-kB motif was mutated (M1 and M3, respectively; Figure 2c) and reduced about threefold upon mutation of the Myc/Max/USF motif (M4, Figure 2c).…”

“…E cient transcription from the hp53 promoter was independent from the presence of a functional p53-protein: Transcription from the hp53 promoter was as e cient in Hep3B cells (data not shown) that do not express p53 (Farshid and Tabor, 1992) as in HepG2 cells that contain unaltered and functionally active p53 (Farshid and Tabor, 1992;Bressac et al, 1990;Puisieux et al, 1993;Ho et al, 1996;Jiang et al, 1996). In addition, treatment of growing cells with a functional antisense p53 oligonucleotide did not alter transcription as compared with the control level.…”

“…via c-Fos-or p50 NF-kB1 -transactivated proteins, mandatory for the e cient transcription from the hp53 promoter. Second, the hp53 promoter does not seem to be autoregulated, since a reduction of transcription after pretreatment of the cells with p53 antisense oligonucleotides was not detected in HepG2 cells that express p53 wt (Bressac et al, 1990;Puisieux et al, 1993;Ho et al, 1996;Jiang et al, 1996).…”

New p73 variants with altered C-terminal structures have varied transcriptional activities

“…To determine whether p73 in¯uences endogenous p53 activity, HepG2 and MCF-7 cells, which are known to produce wild-type p53 protein (Bartek et al, 1990;Puisieux et al, 1993;Tominaga et al, 1993), were used for reporter gene assay (Figure 4). Cotransfection of negative control vector with the reporter plasmid resulted in marked elevation of luciferase activity possibly by endogenous wild-type p53.…”