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Differential activation of p53 by the various adducts of mitomycin C
Tarek Abbas1, Magali Olivier, Jaqueline Lopez
1Department of Biological Sciences, Institute for Biomolecular Structure and Function, Hunter College and Graduate School, CUNY, New York, NY 10021, USA.
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.
Insights
Mitomycin C (MC) and its metabolite DMC induce DNA damage and activate p53, leading to apoptosis. However, the metabolite 2,7-DAM does not activate p53, showing differential DNA damage response pathways.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Mitomycin C (MC) is a chemotherapeutic agent causing DNA damage.
- MC induces p53, a tumor suppressor protein.
- MC forms DNA cross-links and monoadducts.
Purpose of the Study:
- Investigate the p53 activation potential of MC, DMC, and 2,7-DAM.
- Determine if DNA adducts differentially activate DNA damage sensor pathways.
- Explore p53-dependent and independent apoptosis induction.
Main Methods:
- Treating tissue culture cell lines with MC, DMC, and 2,7-DAM.
- Measuring p53 protein levels.
- Quantifying p21 and Gadd45 mRNA levels.
- Assessing apoptosis induction in ML-1 cells.
Main Results:
- MC and DMC induced p53, p21, and Gadd45 mRNA.
- 2,7-DAM did not induce p53 or related mRNA.
- MC and DMC induced apoptosis, while 2,7-DAM did not.
- DMC induced apoptosis via a p53-independent pathway.
Conclusions:
- 2,7-DAM monoadducts do not activate the p53 pathway.
- MC and DMC adducts are differentially recognized by DNA damage sensors.
- DMC initiates apoptosis through both p53-dependent and independent routes.