Resistance to p53-mediated growth arrest and apoptosis in Hep 3B hepatoma cells

S. L. Friedman*, E. Shaulian, T. Littlewood, D. Resnitzky, M. Oren

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Mutations in the tumor suppressor p53 are a common event in hepatocellular carcinoma (HCC). Because HCCs typically occur in livers with chronic injury and impaired function, we have explored the role of wild-type p53 in regulating the growth and differentiation of Hep 3B hepatoma cells, a p53-negative line derived from a liver cancer. Stable Hep 3B cell lines were generated in which inducible p53 was introduced using either a temperature-sensitive mutant (p53val135) or a tamoxifen-regulated p53-estrogen receptor chimera (p53-mER(tm)-pBabepuro). In both cell lines, induction of transcriptionally active p53 was confirmed by assessing several p53 targets: Mdm2 protein, p21(waf1) mRNA and protein, and the cyclin G promoter. Despite marked induction of p21(waf1), cells with active p53 failed to undergo growth arrest, which is probably due to the presence of a non-functional retinoblastoma protein (pRb) in these cells. Apoptosis also was not observed, even after prolonged (48 h) serum starvation or exposure to cisplatinum. Lack of apoptosis was correlated with unchanged bax mRNA levels following p53 induction. Additionally, albumin mRNA levels remained unchanged, and there was no change in basal transactivation of a reporter containing the promoter of the haptoglobin gene, encoding an acute phase protein. This suggests that growth arrest may be required to promote liver-specific gene expression. Overall, our data demonstrated that introduction of transcriptionally active p53 does not alter the malignant, dedifferentiated phenotype of Hep 3B hepatoma cells. Hence, not all cancer cells are equally responsive to the re-activation of wild-type 53. The ability of a cancer cell to undergo p53-mediated phenotypic alterations may depend on the retention of functional downstream effector pathways.

Original languageAmerican English
Pages (from-to)63-70
Number of pages8
JournalOncogene
Volume15
Issue number1
DOIs
StatePublished - 1997
Externally publishedYes

Bibliographical note

Funding Information:
We thank S Wilder for expert technical assistance and Dr Ygal Haupt for H1299/p53val135 cell extracts. The work has been supported by the following sources: NIH RO1 DK37340 (to SLF), NIH RO1 CA40099 (to MO), a Fulbright Scholar Award (to SLF), the Imperial Cancer Research Fund (to TDL) and the Leo and Julia Forcheimer Center for Molecular Genetics (to MO).

Keywords

  • Apoptosis
  • Differentiation
  • Hepatocellular carcinoma
  • p53 tumor suppressor
  • pRb

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