Toxicity, mutation frequency and mutation spectrum induced by dacarbazine in CHO cells expressing different levels of O(6)-methylguanine-DNA methyltransferase
- PMID: 10751609
- DOI: 10.1016/s0027-5107(99)00220-1
Toxicity, mutation frequency and mutation spectrum induced by dacarbazine in CHO cells expressing different levels of O(6)-methylguanine-DNA methyltransferase
Abstract
The toxicity and mutagenicity (including the mutation spectrum induced) of dacarbazine, a methylating cytostatic drug, was examined in CHO cells expressing different levels of the repair enzyme O(6)-methylguanine-DNA methyltransferase (MGMT). Expression of low or high levels of a transfected human MGMT gene under the control of the metallothionein promoter protected the cells against dacarbazine-induced toxicity and mutagenesis. In the absence of MGMT expression, the mutation spectrum in the HPRT locus was dominated by GC-->AT transitions (mostly found at 5'Pu-G sequences), while there were also a few AT-->GC transitions. Expression MGMT was associated with a substantial decrease of GC-->AT mutations, suggesting that these mutations arose primarily via O(6)-methylguanine. These data illustrate the important role of the latter lesion in the drug's mutagenic and cytotoxic activity.
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