Effects of mitomycin C on nuclear and mitochondrial gene expression under hypoxic and normoxic conditions

Mitomycin C (MMC) is the prototype bioreductive anticancer agent requiring biological activation to exert its anticancer activity. Although DNA binding has been demonstrated, alternative nucleic acid targets may also be important for MMC induced toxicity. Using real-time RT-PCR, we investigated the effects of MMC on nuclear and mitochondrial gene expression under hypoxic and normoxic conditions from 15 minutes to 5.5 hours. Hypoxia caused up-regulation of nuclear gene RNA (18S and GAPD) more than mitochondrial genes, which showed no consistent changes, although some significant fluctuations in mtRNA were observed. However, MMC significantly decreased GAPD mRNA and 18S rRNA relative to hypoxia, with 18S rRNA being most affected. These experiments demonstrate that MMC decreases nuclear mRNA and rRNA but not mitochondrial mRNA levels. This decrease is through direct MMC-RNA interaction and not transcription, as the short exposure times for these experiments precluded transcriptional effects. Decreases in intracellular 18S rRNA likely cause less cellular translation leading to cell death.