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N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea sensitivity in mismatch repair-defective human cells
G Aquilina1, S Ceccotti, S Martinelli
1Istituto Superiore di Sanità, Rome, Italy.
Abstract:
To determine whether loss of mismatch repair (MMR) confers sensitivity to N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU), the sensitivity of MMR-defective (MMR-) variants was compared to that of their parental cells. Loss of MMR confers between 2- and 5-fold hypersensitivity to CCNU on HeLa, Raji, or Chinese hamster ovary cells. We also examined whether the sensitivity to CCNU is a general feature of MMR-human tumor cells. The majority expressed O6-methylguanine-DNA-methyltransferase (MGMT; Mex+ phenotype) that confers resistance to CCNU independent of their MMR status. The single Mex- MMR- SW48 cells were 4-fold more sensitive to CCNU than the Mex- MMR+ SW620 cells. CCNU sensitivity of the Mex+ cells was analyzed after treatment with the MGMT inhibitor O6-benzylguanine. The MMR- AN3CA, LS174T, LoVo, and DU145 cells were 1.4-4.3-fold more sensitive to CCNU than the MMR+ HeLaS3, HT29, and A2780 cells. Hypersensitivity to CCNU was not seen in the MMR- cell lines DLD1, HEC1A, and HCT116, suggesting that other parameters, besides the MGMT and MMR defects, affect the cell's response to this drug. In contrast, loss of MMR was always associated with tolerance to the methylating agent N-methyl-N-nitrosourea. The sensitivity to CCNU in MMR- cells suggests a possible involvement of this repair pathway in repairing interstrand cross-links and may have implications for clinical treatment of MMR- tumors.
Insights
Loss of mismatch repair (MMR) increases sensitivity to CCNU chemotherapy in some cancer cells. This suggests MMR
Area of Science:
- DNA repair mechanisms
- Cancer chemotherapy
- Genomic instability
Background:
- Mismatch repair (MMR) is crucial for correcting DNA replication errors.
- N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU) is a chemotherapeutic agent.
- The relationship between MMR deficiency and CCNU sensitivity is not fully understood.
Purpose of the Study:
- To investigate if loss of MMR function leads to increased sensitivity to CCNU.
- To determine if this sensitivity is a general characteristic of MMR-deficient human tumor cells.
- To explore the implications for treating MMR-deficient tumors.
Main Methods:
- Compared the sensitivity of MMR-defective (MMR-) cell variants to their parental MMR-proficient (MMR+) counterparts.
- Utilized various human tumor cell lines with different MMR and O6-methylguanine-DNA-methyltransferase (MGMT) statuses.
- Administered CCNU and MGMT inhibitor O6-benzylguanine to assess drug response.
Main Results:
- Loss of MMR conferred 2- to 5-fold hypersensitivity to CCNU in HeLa, Raji, and Chinese hamster ovary cells.
- MMR-deficient tumor cells (AN3CA, LS174T, LoVo, DU145) showed 1.4- to 4.3-fold increased sensitivity to CCNU compared to MMR-proficient cells, particularly when MGMT was inhibited.
- Hypersensitivity to CCNU was not observed in all MMR-deficient cell lines (DLD1, HEC1A, HCT116), indicating other factors influence drug response.
- Loss of MMR was associated with tolerance to N-methyl-N-nitrosourea, a different type of DNA damaging agent.
Conclusions:
- MMR deficiency can lead to hypersensitivity to CCNU, suggesting MMR's role in repairing CCNU-induced DNA damage, possibly interstrand cross-links.
- The presence of MGMT significantly impacts CCNU resistance, independent of MMR status.
- Further research is needed to understand the complex factors influencing CCNU sensitivity in MMR-deficient cells.
- Findings may inform clinical strategies for treating MMR-deficient tumors with CCNU-based therapies.
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