Abstract 2079: The role of TRPM2 splice variants in enhanced cell proliferation and sensitivity to oxidative-stress mediated apoptosis in neuroblastoma
Authors: Chen Shu-Jen , Tong Qin , Conrad Kathleen , Zhang Wenyi , Miller Barbara A. 
Published: July 2012

Neuroblastoma is the most frequent and deadly solid tumors of childhood. The cure rate for advanced disease is only 30%. Understanding the mechanisms of cell proliferation and apoptosis in neuroblastoma is desperately needed in order to develop new anti-cancer drugs. The transient receptor potential channel TRPM2 is an ion channel which regulates critical cellular processes and survival in response to oxidative stress in many cell types. Isoforms include TRPM2-L (full length or wild type) and TRPM2-S (short, containing only the first two transmembrane domains and no pore) and they are expressed in primary neuroblastoma. In this study, we investigated the expression and function of TRPM2-L and -S isoforms in cell proliferation and sensitivity to apoptosis induced by oxidative-stress in neuroblastoma. Three neuroblastoma cell lines which stably express TRPM2-L, TRPM2-S or vector were established by G418 selection. Cell proliferation and viability were measured by XTT assay. Mechanisms of enhanced proliferation and apoptosis were studied by western blotting, subcellular fractionation and treatment with inhibitors. [Ca2+]i was evaluated by digital video image analysis of single cells. Our data demonstrated that TRPM2-S-expressing cells have significantly enhanced proliferation compared to TRPM2-L- or vector-expressing cells. TRPM2-S expressing cells showed increased Akt phosphorylation which correlated with increased proliferation. LY294002, a PI3K inhibitor, abolished the enhanced cell proliferation in TRPM2-S-expressing cells, demonstrating that enhanced proliferation involved PI3K/Akt activation. Consisted with activation of Akt, glucose transporter 1 (GLUT1) expression was elevated on the membrane of TRPM2-S expressing cells and correlated with increased cell growth. The viability and apoptosis of all three cell lines was reduced in response to H2O2 or doxorubicin in a time- and dose- dependent manner. However, TRPM2-S-expressing cells were the most sensitive and demonstrated the greatest cleavage and activation of apoptotic molecules. Akt is a major mediator in neuroblastoma proliferation and apoptosis. After treatment with physiological concentrations H2O2 (100 µM) or doxorubicin (0.1 μM), pAkt decreased in TRPM2-S-expressing cells, but increased in TRPM2-L-expressing cells. These results demonstrate that differential expression of TRPM2 isoforms influences a cell's proliferative potential and responsiveness to oxidative stress and chemotherapy. The increased growth of TRPM2-S expressing cells and sensitivity to chemotherapy involves the PI3K/Akt signaling pathway. TRPM2 isoforms may be future therapeutic targets for selective cell killing in cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2079. doi:10.1158/1538-7445.AM2011-2079