Related Experiment Videos
p53-dependent apoptosis in melanoma cells after treatment with camptothecin
1Department of Medicine, Division of Dermatology, Vancouver Hospital and Health Sciences Center, The University of British Columbia, Vancouver, British Columbia, Canada. gangli@unixg.ubc.ca
Abstract:
Cutaneous malignant melanoma is a life-threatening cancer with poor prognosis due to a high metastasis potential. The main obstacle in treatment of metastatic melanoma is the resistance to chemotherapy. Recent studies indicated that apoptosis is a common mechanism of action for various cytotoxic agents. As p53 plays an important part in apoptosis, we investigated the role of p53 in chemosensitivity of melanoma cells. Previously, we found that melanoma cell lines containing wild-type p53 have significantly higher response rates to chemotherapy than cell lines with a mutant p53 gene. To confirm the role of p53 in melanoma chemosensitivity further, we transfected an expression vector, pED1, which carries a mutant p53 gene, into a wild-type p53 melanoma cell line, MMAN. We examined the effect of mutant p53 on camptothecin-induced apoptosis and the expression of genes which are known to be involved in apoptosis or drug resistance, such as bcl-2, bax, bak, p21waf1, and P-glycoprotein. Our results indicate that overexpression of the mutant p53 increased the growth rate of MMAN cells, reduced the sensitivity to camptothecin, and lowered drug-induced apoptosis by 2-3-fold. Flow cytometry indicated that the camptothecin-induced apoptosis is not associated with G1 arrest. Furthermore, camptothecin treatment reduced bcl-2 and P-glycoprotein expression in wild-type p53 MMAN cells, but not cells overexpressing mutant p53. These results demonstrate that p53 mutational status is a determinant of melanoma chemosensitivity. p53 may downregulate bcl-2 and P-glycoprotein to induce apoptosis in melanoma cells after chemotherapy.
Insights
The p53 tumor suppressor gene
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Cutaneous malignant melanoma is a dangerous cancer with a high risk of metastasis and poor prognosis.
- Chemotherapy resistance is a major challenge in treating metastatic melanoma.
- Apoptosis, or programmed cell death, is a key mechanism for many chemotherapy drugs.
Purpose of the Study:
- To investigate the role of the p53 tumor suppressor gene in the chemosensitivity of melanoma cells.
- To confirm previous findings that wild-type p53 melanoma cells are more responsive to chemotherapy than mutant p53 cells.
- To examine how mutant p53 affects camptothecin-induced apoptosis and related gene expression in melanoma.
Main Methods:
- A wild-type p53 melanoma cell line (MMAN) was transfected with an expression vector (pED1) carrying a mutant p53 gene.
- The effect of mutant p53 overexpression on camptothecin-induced apoptosis was assessed.
- Expression levels of apoptosis-related genes (bcl-2, bax, bak, p21waf1) and drug resistance gene (P-glycoprotein) were analyzed.
Main Results:
- Overexpression of mutant p53 in MMAN cells increased cell growth rate and reduced sensitivity to camptothecin by 2-3 fold.
- Drug-induced apoptosis was significantly lowered in cells with mutant p53.
- Camptothecin treatment reduced bcl-2 and P-glycoprotein expression in wild-type p53 cells, but not in cells overexpressing mutant p53.
Conclusions:
- The mutational status of the p53 gene is a critical factor determining melanoma chemosensitivity.
- Mutant p53 can confer resistance to chemotherapy by potentially upregulating anti-apoptotic factors like bcl-2 and P-glycoprotein.
- Understanding the role of p53 in apoptosis pathways could lead to improved melanoma treatment strategies.