Role of uncoupling protein 2 in ovarian carcinoma Free

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Mitochondrial dysfunction and oxidative stress are important factors that contribute to cancer development. Elevated levels of mitochondrial derived reactive oxygen species (ROS) can stimulate cancer cell growth and proliferation. However, excessive accumulation of ROS can also lead to oxidative damage and apoptosis activation. Under these harsh conditions, cancer cells develop a variety of adaptive and cytoprotective mechanisms to survive. One potential mechanism could be the upregulation of an inner mitochondrial membrane protein called uncoupling protein 2 (UCP2). Although the physiological function of UCP2 is not fully understood, recent evidence has suggested that UCP2 may help protect cancer cells from oxidative stress by acting as a negative regulator of mitochondrial ROS production. To further test this possibility, we examined the potential relationship between UCP2 expression and ROS production within ovarian cancer cells. Here we show through real time RT-PCR analysis that UCP2 mRNA expression is increased approximately 8.3 fold in human SKOV-3 ovarian carcinoma cells in comparison to the less aggressive 2008 ovarian carcinoma cells. Furthermore, the basal rate of extracellular hydrogen peroxide production in SKOV-3 cells is nearly 10 fold higher than in 2008 cells, as determined using the A6550 fluorescent dye-based assay system. Examination of the corresponding UCP2 protein expression has been limited by the availability of high quality and specific commercial antibodies. To overcome this, we have generated and isolated a large quantity of His-tagged full length human UCP2 recombinant protein from E. coli. This is currently being used as an immunogen to generate a custom polyclonal antibody. These reagents will help facilitate protein expression studies through western blotting and immunohistochemistry and to validate the mRNA expression studies. Overall, these preliminary results show a correlation between UCP2 mRNA expression and endogenous ROS production within ovarian carcinoma cells. Furthermore, this data suggests that UCP2 may function by modulating ROS levels within the mitochondria of cancer cells that are subject to increased oxidative stress. Inhibition of this protective mechanism may serve as a novel target for anti-cancer therapy. (This research was supported by a Canadian Institutes of Health Research grant to G. Singh)