Differential activation of the Fas/CD95 pathway by Ad-p53 in human gliomas

  • Authors:
    • Julie A. Cerrato
    • Tahira Khan
    • Dimpy Koul
    • Frederick F. Lang
    • Charles A. Conrad
    • W. K.A. Yung
    • Ta-Jen Liu
  • View Affiliations

  • Published online on: February 1, 2004     https://doi.org/10.3892/ijo.24.2.409
  • Pages: 409-417
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Abstract

Adenoviral p53 gene transfer (Ad-p53) induces apoptosis in glioma cells expressing mutant p53, but fails in cells with wild-type p53. Endogenously, gliomas express varied levels of Fas/CD95, yet constitutively high levels of Fas/CD95 ligand. Because the mechanism behind the differential apoptotic response to Ad-p53 infection remains elusive, we examined how the Fas/CD95 pathway is involved in U87MG (wt-p53), D54 (wt-p53), U251MG (mutant-p53), and U373MG (mutant-p53) glioma cell lines. Ad-p53 infection did not alter the levels of Fas/CD95 ligand in either wild-type or mutant p53-expressing cell lines. In contrast, Ad-p53 infection led to an ~3-fold increase in Fas/CD95 mRNA expression in mutant p53-bearing cell lines but not in their wild-type (wt) counterparts, as assessed in an RNase protection assay. Fas/CD95 mRNA induction appeared to be regulated at the transcriptional level because Ad-p53 infection resulted in up to a 4-fold increase in Fas/CD95 promoter reporter activity. Subsequently, flow cytometric analysis revealed a 2- to 4-fold increase in surface Fas/CD95 expression following Ad-p53 infection in mutant-p53-containing cell lines. Use of the protein transport inhibitor Brefeldin A significantly inhibited Ad-p53-induced surface Fas/CD95 expression, but only partially inhibited apoptosis in mutant-p53 cell lines. These results suggest that p53 regulates Fas/CD95 expression at the transcriptional level and through protein trafficking in mutant-p53 cell lines. Fluorogenic activity assays demonstrated that induction of caspase-8 activity following Ad-p53 infection correlated with increases in Fas/CD95 expression. Incubating cells with a caspase-8-specific inhibitor Ac-IETD-CHO prior to Ad-p53 infection inhibited caspase-8 activity and apoptosis. Together, our results suggest that regulation of the Fas/CD95 pathway is partly responsible for Ad-p53-induced apoptosis in glioma cells, which depends on the p53 status of the involved cells. Additionally, the inability of Ad-p53 to activate the Fas/CD95 pathway in wt-p53 glioma cells coincides with their apoptotic-resistant phenotype. Further elucidation of the nature of this resistance could ultimately augment the efficacy of Ad-p53 gene therapy.

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February 2004
Volume 24 Issue 2

Print ISSN: 1019-6439
Online ISSN:1791-2423

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Spandidos Publications style
Cerrato JA, Khan T, Koul D, Lang FF, Conrad CA, Yung WK and Liu T: Differential activation of the Fas/CD95 pathway by Ad-p53 in human gliomas. Int J Oncol 24: 409-417, 2004.
APA
Cerrato, J.A., Khan, T., Koul, D., Lang, F.F., Conrad, C.A., Yung, W.K., & Liu, T. (2004). Differential activation of the Fas/CD95 pathway by Ad-p53 in human gliomas. International Journal of Oncology, 24, 409-417. https://doi.org/10.3892/ijo.24.2.409
MLA
Cerrato, J. A., Khan, T., Koul, D., Lang, F. F., Conrad, C. A., Yung, W. K., Liu, T."Differential activation of the Fas/CD95 pathway by Ad-p53 in human gliomas". International Journal of Oncology 24.2 (2004): 409-417.
Chicago
Cerrato, J. A., Khan, T., Koul, D., Lang, F. F., Conrad, C. A., Yung, W. K., Liu, T."Differential activation of the Fas/CD95 pathway by Ad-p53 in human gliomas". International Journal of Oncology 24, no. 2 (2004): 409-417. https://doi.org/10.3892/ijo.24.2.409