The role of p53 in the apoptosis induced by anticancer drugs in bladder cancer cells
| Autor: | Fu-Lin Chang, 張福林 |
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| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 Many antitumor agents may kill cells by induction of apoptosis. However, the relationship between the status of p53 and the sensitivity of tumors to anticancer treatment is somewhat more complex. Clinical studies showed that, in patients with bladder tumors that did not demonstrate p53 alterations, adjuvant chemotherapy conferred no recurrence or survival benefit. In contrast, in patients with p53-altered tumors, adjuvant chemotherapy resulted in a decreased risk of recurrence and a increased chance of surviving. These data imply that bladder tumor cells harboring mutant p53 are possibly prone to death during drug treatment. In our in vitro studies, we found that anticancer drugs-induced apoptosis in bladder cancer cells is independent of the presence of wild-type p53. Indeed, tumor cells harboring heterozygous mutant p53 seem to be most susceptible to undergo apoptosis. When the various p53 mutants (V143A, V173L, H179Q, N247I, and R273L) were stably transfected into the TCCSUP bladder carcinoma cell line (no endogenous full-length mutant p53), almost all mutant p53 transfectants were more sensitive to adriamycin and cisplatin except for the p53Leu273 mutant. Adriamycin and cisplatin induced cell death was assayed by TUNEL, annexin-Ⅴ and Hoechst staining. Our results show that cisplatin-induced cell death is mediated mainly through apoptosis, while adriamycin-induced cell death probably occurs through a non- apoptotic pathway. In order to understand how mutant p53 promotes apoptosis in bladder cancer cells？We investigate the mechanism of the enhancement of cisplatin-induced apoptosis by exogenous mutant p53. We found that both wild-type and mutant p53 was phosphorylated at serine15 in response to cisplatin. However, the acetylation of mutant p53 decreased, in contrast to the acetylation of wild-type p53 increased during the treatment of cisplatin. Besides that, mutant p53 did not alter surface Fas and Fas-L expression. They amplified cisplatin-induced apoptosis mainly through activation of caspase-9 but not caspase-8. On the other hand, several p53-inducible genes (Noxa, p53R2 and PIDD) were not activated during cisplatin treatment. Down-regulation of Bcl-2 was observed, it could be reversed by the addition of histone deacetylase inhibitor trichostatin A (TSA), but the apoptosis proceeds as usual. Transcriptional inhibitor actinomycin D and translational inhibitor cycloheximide were unable to impede the apoptosis induced by cisplatin in these transfectants. These results indicated that enhanced apoptosis by mutant p53 was independent of transcriptional activation and translation of p53-related target genes. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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