Differential Activation of p53 by the Various Adducts of Mitomycin C

Tarek Abbas,Magali Olivier,Jaqueline Lopez,Sandra Houser,Gu Xiao,Gopinatha Suresh Kumar,Maria Tomasz,Jill Bargonetti

doi:10.1074/jbc.m205495200

Abstract

Mitomycin C (MC) is a cytotoxic chemotherapeutic agent that causes DNA damage in the form of DNA cross-links as well as a variety of DNA monoadducts and is known to induce p53. The various DNA adducts formed upon treatment of mouse mammary tumor cells with MC as well as 10-decarbamoyl MC (DMC) and 2,7-diaminomitosene (2,7-DAM), the major MC metabolite, have been elucidated. The cytotoxicity of DMC parallels closely that of MC in a number of rodent cell lines tested, whereas 2,7-DAM is relatively noncytotoxic. In this study, we investigate the ability of MC, DMC, and 2,7-DAM to activate p53 at equidose concentrations by treating tissue culture cell lines with the three mitomycins. Whereas MC and DMC induced p53 protein levels and increased the levels of p21 and Gadd45 mRNA, 2,7-DAM did not. Furthermore, MC and DMC, but not 2,7-DAM, were able to induce apoptosis efficiently in ML-1 cells. Therefore the 2,7-DAM monoadducts were unable to activate the p53 pathway. Interestingly, DMC was able to initiate apoptosis via a p53-independent pathway whereas MC was not. This is the first finding that adducts of a multiadduct type DNA-damaging agent are differentially recognized by DNA damage sensor pathways.

Highlights

Mitomycin C (MC) is a cytotoxic chemotherapeutic agent that causes DNA damage in the form of DNA crosslinks as well as a variety of DNA monoadducts and is known to induce p53
MC and decarbamoyl MC (DMC) but Not 2,7-DAM Can Induce p53 Nuclear Accumulation—The noncytotoxic effect of 2,7-DAM suggested that the DNA monoadducts produced in cells after treatment with this compound were unable to induce a signal transduction pathway that culminated in the induction of p53
We tested this hypothesis by treating the ML-1 cell line with MC, DMC, and 2,7-DAM, as well as with two other drugs shown previously to induce p53 [17]

Summary

Monoadduct frequency

Ϫ a From data in Ref. 9; error limits are omitted. b From data in Ref. 11; linearly extrapolated from treatment with 40 ␮M 2,7-DAM to that with 10 ␮M 2,7-DAM. B From data in Ref. 11; linearly extrapolated from treatment with 40 ␮M 2,7-DAM to that with 10 ␮M 2,7-DAM. The lack of cytotoxicity of 2,7-DAM in contrast to MC and DMC may be explained by the hypothesis that 2,7-DAM-DNA monoadducts are unable to induce a signal transduction pathway that culminates in the induction of p53. We tested this hypothesis by comparing the induction of p53 in a wild-type p53 containing myeloid leukemia cell line (ML-1) by MC, DMC, and 2,7-DAM. We further show that a human myeloid leukemia cell line (K562), lacking functional p53 is resistant to MC but not DMC cytotoxic effects

MATERIALS AND METHODS

RESULTS

DISCUSSION