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pH dependence of mitomycin C-induced cross-linking activity in EMT6 tumor cells
Abstract:
Mitomycin C (MC), a quinone-containing bioreductive alkylating agent, is cytotoxic to aerobic EMT6 tumor cells despite the fact that little bioactivation of MC occurs in EMT6 cell homogenates in the presence of O2. Because spontaneous activation of MC at acidic pH has been reported in chemical systems, aerobic EMT6 tumor cells were incubated in serum-free 2-(N-morpholino)ethanesulfonic acid or N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer at pH 5.7, 6.4, and 7.5 and exposed to MC for 2 h. As the extracellular pH was lowered, MC-induced DNA-DNA cross-linking, as measured by alkaline elution techniques, was enhanced. This effect was dose dependent at the three pH values tested. Measurement of intracellular pH by flow cytometric analysis indicated that the decrease in extracellular pH was paralleled by a fall in intracellular pH. The alteration of the extracellular pH had no effect on the colony-forming ability of control cells. The survival of cells treated with MC, however, was decreased as the pH was lowered. These data suggest that the intracellular and/or the extracellular pH is an important determinant of MC activity in aerobic EMT6 tumor cells.
Insights
Mitomycin C (MC) shows increased DNA damage and reduced cancer cell survival in acidic environments. Lowering pH enhances MC
Area of Science:
- Biochemistry
- Cell Biology
- Oncology
Background:
- Mitomycin C (MC) is a bioreductive alkylating agent with known cytotoxicity.
- MC bioactivation is limited in aerobic EMT6 tumor cells under normal oxygen conditions.
- Acidic pH has been shown to promote spontaneous activation of MC in chemical systems.
Purpose of the Study:
- To investigate the effect of extracellular pH on Mitomycin C activity in aerobic EMT6 tumor cells.
- To determine if pH influences MC-induced DNA damage and cell survival.
- To explore the relationship between extracellular and intracellular pH in modulating MC's cytotoxic effects.
Main Methods:
- Aerobic EMT6 tumor cells were incubated in buffers at varying pH levels (5.7, 6.4, 7.5).
- Cells were exposed to Mitomycin C (MC) for 2 hours.
- DNA-DNA cross-linking was assessed using alkaline elution.
- Intracellular pH was measured by flow cytometry.
- Cell survival was evaluated by colony formation assays.
Main Results:
- Lowering extracellular pH significantly enhanced MC-induced DNA-DNA cross-linking in a dose-dependent manner.
- A decrease in extracellular pH led to a corresponding decrease in intracellular pH.
- Reduced extracellular pH resulted in decreased survival of MC-treated cells.
- Control cells (without MC) showed no change in colony-forming ability across different pH levels.
Conclusions:
- Extracellular and intracellular pH are critical determinants of Mitomycin C's activity in aerobic EMT6 tumor cells.
- Acidic conditions potentiate MC's DNA-damaging effects and enhance its cytotoxicity.
- These findings suggest pH modulation could be a strategy to improve MC efficacy in cancer therapy.