Elevated DNA polymerase beta activity in a cis-diamminedichloroplatinum(II) resistant P388 murine leukemia cell line

The activity of DNA polymerase beta, which is an enzyme involved in repair of DNA damage, was assessed in P388 murine leukemia cell lines sensitive and resistant to cis-diamminedichloroplatinum(II) (cis-Pt). The resistant line was selected with cis-Pt and showed cross-resistance to a number of alkylating agents, but not to an anthracycline. The DNA polymerase beta activity was found to be elevated 5-fold in the resistant line based upon activity per mg cell protein and elevated 4-fold based upon activity per 10(7) cells. The characterization of elevated activity of an enzyme active in DNA repair in a cell line resistant to DNA damaging agents describes a possible mechanism of resistance in addition to those previously found.