| Summary: | 碩士 === 國立陽明大學 === 醫學生物技術研究所 === 94 === Previous studies have shown that chemotherapy causes deamidation of the protein Bcl-xL in tumor cells. This Bcl-xL deamidation inhibits its antiapoptotic ability and sensitizes tumor cells to cisplatin treatment. Surprisingly, Rb inhibits this process. To test this model, we have shown recently that E1A-mediated Rb inactivation in an ovarian cancer cell line (SKOV3.ip1) leads to Bcl-xL deamidation which contributes to cisplatin-induced apoptosis. Furthermore, ectopic expression of deamidated form of Bcl-xL (N52/66D) enhances cell death, whereas the nondeamidated Bcl-xL (N52/66A) protects E1A-mediated apoptosis. In this follow-up studies, we showed that BH3 protein bad interacts equally well with all three forms of Bcl-xL protein. In addition, ectopic expression of p53 did not enhance cell death or Bcl-xL deamidation in SKOV3.ip1. To test whether Bcl-xL deamidation occurs in other cancer cells, we selected four cancer cell lines with various Rb and p53 status. Our data show that the cell lines sensitive to cisplatin correlated with induction of Bcl-xL deamidation, whereas the cell lines resistant to cisplatin exhibited no induction of Bcl-xL deamidation. Interestingly, expression of E1A did not sensitize the cisplatin-resistant cell lines or Bcl-xL deamidation. Both the cisplatin-resistant cell lines are Rb wt. Furthermore, In vitro alkaline treatment induced Bcl-xL deamidation in these cell lines, suggesting that no induction of Bcl-xL deamidation in the cisplatin- resistant cell lines is not due to mutation of Bcl-xL at 55 and 66 residues. We also noticed that level of Bcl-2 was higher in the cisplatin-resistant cells than in the cisplatin-sensitive cells. Moreover, we found that N-acetylcysteine protected cells from cisplatin induced apoptosis and repressed Bcl-xL deamidation. This suggested that reactive oxygen species (ROS) may be involved in the induction of Bcl-xL deamidation by cisplatin.
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