Repair and removal of azoxymethane-induced O6-methylguanine in rat colon by O6-methylguanine DNA methyltransferase and apoptosis.

•Sequential cellular events occur rapidly in rat colons following AOM.•The sequence of events is AOM-dose and O6meG adduct-load dependent.•Apoptosis is an early response and follows a close relationship to O6meG.•Higher O6meG and completion of MGMT activity is required for inducing apoptosis.•Apoptosis may be triggered by O6meG and act as a complementary mechanism to MGMT.