Differences in mutant p53 protein stability and functional activity in teniposide-sensitive and -resistant human leukemic CEM cells (original) (raw)

Oncogene volume 19, pages 5010–5019 (2000)Cite this article

Abstract

We examined p53 protein stability and DNA damage-induced p53-dependent responses in a human leukemic CEM cell line and two teniposide-resistant sublines, CEM/VM-1 and CEM/VM-1-5 (∼40 and 400-fold resistant to teniposide, respectively). Although all cell lines contain the same p53 mutations at codons 175 (Arg→His) and 248 (Arg→Gln), the constitutive levels of p53 were progressively increased with the resistance of the cells to teniposide. By pulse-chase experiments, we found that the half-lives of mutant p53 protein were approximately 12, 17, and >30 h in CEM, CEM/VM-1, and CEM/VM-1-5 cells, respectively. The prolonged half-lives of p53 in these cells is consistent with the fact that the protein harbors the indicated mutations. Of note, however, is the fact that the increased p53 protein half-lives in the two drug-resistant cell lines corresponds to a proportional decrease in MDM2 protein levels but an increase in p53-MDM2 binding interactions. This suggests that MDM2-mediated p53 degradation may be altered in our leukemic cell lines. The DNA damage-induced p53 response is fully functional in the drug-sensitive CEM cells containing a mutant p53, but this pathway is attenuated in the drug-resistant cells. Specifically, while the mutant p53 was phosphorylated at serine-15 in response to ionizing radiation in all these cell lines, mutant p53 induction in response to teniposide or ionizing radiation and induction of the p53-target genes, p21 and GADD45 only occurred in the drug-sensitive CEM cells. As assessed by MTT cytotoxicity assay, CEM cells were also significantly more sensitive to ionizing radiation, compared to the drug-resistant cell lines, and this correlated with p53 induction. Collectively, these results suggest that changes in constitutive mutant p53 protein levels, p53-MDM2 binding interactions, and altered regulation of the DNA damage-inducible p53-dependent pathway may play a role in drug- and radiation-responsiveness in these cells.

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Acknowledgements

We are grateful to Linda Rawlinson and the Biomedical Communications Department at St. Jude Children's Research Hospital for preparation of some of the artwork. This work was supported in part by Research Grants CA40570 and CA30103 (to WT Beck) from the National Cancer Institute, DHHS, Bethesda, MD, and in part by the University of Illinois at Chicago.

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  1. Susan E Morgan
    Present address: HPD Biologics Development, Abbott Laboratories, Abbott Park, 60064, Illinois, IL, USA

Authors and Affiliations

  1. Division of Molecular Pharmacology, Department of Molecular Genetics, University of Illinois at Chicago, Chicago, 60607, Illinois, IL, USA
    Susan E Morgan, Pu Chen Wang, Uppoor G Bhat & William T Beck
  2. Department of Surgical Oncology, Hiroshima University, Kasumi, Minami-ku, Hiroshima, 734-8553, Japan
    Ryungsa Kim
  3. Department of General Surgery, Fukuoka Dental College Hospital, Fukuoka, 814-01, Japan
    Hiroki Kusumoto
  4. Department of Cell and Gene Therapy, St. Jude Children's Research Hospital, Memphis, 38101, Tennessee, TN, USA
    Taihe Lu
  5. Department of Pharmaceutics and Pharmacodynamics, University of Illinois at Chicago, Chicago, 60607, Illinois, IL, USA
    William T Beck

Authors

  1. Susan E Morgan
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  2. Ryungsa Kim
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  3. Pu Chen Wang
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  4. Uppoor G Bhat
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  5. Hiroki Kusumoto
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  6. Taihe Lu
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  7. William T Beck
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Morgan, S., Kim, R., Wang, P. et al. Differences in mutant p53 protein stability and functional activity in teniposide-sensitive and -resistant human leukemic CEM cells.Oncogene 19, 5010–5019 (2000). https://doi.org/10.1038/sj.onc.1203865

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