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hMSH3 overexpression and cellular response to cytotoxic anticancer agents
R Pepponi1, G Graziani, S Falcinelli
1Laboratory of Pharmacology, Istituto Dermopatico Dell'Immacolata (IDI-IRCCS), Via dei Monti di Creta 104, 00167 Rome, Italy.
Abstract:
Mutations or transcriptional silencing of mismatch repair genes have been linked with tumour cell resistance to O(6)-guanine methylating agents, 6-thioguanine, cisplatin, doxorubicin and etoposide. Recently, it has been demonstrated that overexpression of the MSH3 protein is associated with depletion of the mismatch binding factor MutSalpha, and then with a marked reduction in the efficiency of base/base mismatch repair. In the present study we evaluated sensitivity of the HL-60 cell line and its methotrexate-resistant subline HL-60R, which overexpresses the hMSH3 gene, to a panel of chemotherapeutic agents. Cell growth inhibition induced by temozolomide, 6-thioguanine and N-methyl-N'-nitro-N-nitrosoguanidine was significantly lower in the hMSH3-overexpressing HL-60R cell line as compared with the HL-60 parental line. Moreover, HL-60R cells were more resistant than HL-60 cells to chromosome aberrations induced by either N-methyl-N'-nitro-N-nitrosoguanidine or temozolomide, and to apoptosis triggered by the latter drug. Both cell lines were equally susceptible to growth inhibition induced by cisplatin, etoposide or doxorubicin. In addition, HL-60 and HL-60R cells showed comparable sensitivity to the clastogenic and apoptotic effects of cisplatin and etoposide. These results further confirm that loss of base/base mismatch repair is the most important molecular mechanism involved in cell resistance to O(6)-guanine methylating agents and 6-thioguanine. However, the status of the mismatch repair system could still influence tumour cell sensitivity to cisplatin, etoposide and doxorubicin, depending on the specific component of the system that is lost, and on the genetic background of the cell.
Insights
Overexpression of the MSH3 gene reduces cancer cell sensitivity to temozolomide and 6-thioguanine by impairing mismatch repair. This suggests MSH3 levels impact resistance to specific chemotherapy drugs.
Area of Science:
- Molecular biology
- Cancer research
- Genetics
Background:
- Mismatch repair gene mutations are linked to tumor resistance against various chemotherapeutic agents.
- MSH3 protein overexpression can deplete MutSalpha, reducing base/base mismatch repair efficiency.
- Understanding MSH3's role is crucial for predicting and overcoming chemotherapy resistance.
Purpose of the Study:
- To evaluate the sensitivity of HL-60 and HL-60R cell lines, differing in hMSH3 gene expression, to a panel of chemotherapeutic agents.
- To investigate the impact of MSH3 overexpression on resistance to DNA-damaging agents and induction of chromosomal aberrations and apoptosis.
Main Methods:
- Comparison of cell growth inhibition, chromosomal aberrations, and apoptosis induction between HL-60 and hMSH3-overexpressing HL-60R cells.
- Treatment with temozolomide, 6-thioguanine, N-methyl-N'-nitro-N-nitrosoguanidine, cisplatin, etoposide, and doxorubicin.
Main Results:
- HL-60R cells showed significantly lower sensitivity to temozolomide, 6-thioguanine, and N-methyl-N'-nitro-N-nitrosoguanidine compared to HL-60 cells.
- HL-60R cells exhibited increased resistance to N-methyl-N'-nitro-N-nitrosoguanidine and temozolomide-induced chromosomal aberrations and apoptosis.
- Both cell lines displayed similar sensitivity to cisplatin, etoposide, and doxorubicin regarding growth inhibition, clastogenicity, and apoptosis.
Conclusions:
- Loss of base/base mismatch repair is a key mechanism for resistance to O(6)-guanine methylating agents and 6-thioguanine.
- MSH3 overexpression contributes to resistance against specific chemotherapeutic agents like temozolomide and 6-thioguanine.
- The influence of mismatch repair status on sensitivity to cisplatin, etoposide, and doxorubicin may depend on the specific gene affected and cellular context.