A Splice Variant of the Human Ion Channel TRPM2 Modulates Neuroblastoma Tumor Growth through Hypoxia-inducible Factor (HIF)-1/2 alpha

作者：Chen Shu jen; Hoffman Nicholas E; Shanmughapriya Santhanam; Bao Lei; Keefer Kerry; Conrad Kathleen; Merali Salim; Takahashi Yoshinori; Abraham Thomas; Hirschler Laszkiewicz Iwona; Wang JuFang; Zhang Xue Qian; Song Jianliang; Barrero Carlos; Shi Yuguang; Kawasawa Yuka Imamura; Bayerl Michael; Sun Tianyu; Barbour Mustafa; Wang Hong Gang; Madesh Muniswamy; Cheung Joseph Y; Miller Barbara A^*

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2014, 289(52): 36284-36302.

DOI：10.1074/jbc.M114.620922

The calcium-permeable ion channel TRPM2 is highly expressed in a number of cancers. In neuroblastoma, full-length TRPM2 (TRPM2-L) protected cells from moderate oxidative stress through increased levels of forkhead box transcription factor 3a (FOXO3a) and superoxide dismutase 2. Cells expressing the dominant negative short isoform (TRPM2-S) had reduced FOXO3a and superoxide dismutase 2 levels, reduced calcium influx in response to oxidative stress, and enhanced reactive oxygen species, leading to decreased cell viability. Here, in xenografts generated with SH-SY5Y neuroblastoma cells stably expressing TRPM2 isoforms, growth of tumors expressing TRPM2-S was significantly reduced compared with tumors expressing TRPM2-L. Expression of hypoxia-inducible factor (HIF)-1/2 alpha was significantly reduced in TRPM2-S-expressing tumor cells as was expression of target proteins regulated by HIF-1/2 alpha including those involved in glycolysis (lactate dehydrogenase A and enolase 2), oxidant stress (FOXO3a), angiogenesis (VEGF), mitophagy and mitochondrial BNIP3 and NDUFA4L2), and mitochondrial electron transport chain activity (cytochrome oxidase 4.1/4.2 in complex IV). The reduction in HIF-1/2 alpha was mediated through both significantly reduced HIF-1/2 alpha mRNA levels and increased levels of von Hippel-Lindau E3 ligase in TRPM2-S-expressing cells. Inhibition of TRPM2-L by pretreatment with clotrimazole or expression of TRPM2-S significantly increased sensitivity of cells to doxorubicin. Reduced survival of TRPM2-S-expressing cells after doxorubicin treatment was rescued by gain of HIF-1 or -2 alpha function. These data suggest that TRPM2 activity is important for tumor growth and for cell viability and survival following doxorubicin treatment and that interference with TRPM2-L function may be a novel approach to reduce tumor growth through modulation of HIF-1/2 alpha, mitochondrial function, and mitophagy.

• 出版日期2014-12-26