CACNA2D3 is downregulated in gliomas and functions as a tumor suppressor

CACNA2D3, an auxiliary member of the alpha-2/delta subunit three family of the voltage-dependent calcium channel complex, plays a critical role in tumor suppression. However, its role in glioma carcinogenesis remains largely unknown. Here, we investigated the putative tumor suppressive role of CACNA2D3 in gliomas. Downregulation of CACNA2D3 was frequently detected in glioma tissues and cells compared with their non-tumorigenic counterparts, and correlated with poor survival. To investigate the underlying mechanism of CACNA2D3 in the development and progression of glioma, we performed CACNA2D3 ectopic expression in glioma cells (U87 and U251) and knockdown of CACNA2D3 in LN229 cells and conducted in vitro and in vivo functional assays. Our findings showed that increased intracellular calcium (Ca²⁺ ) mediated by overexpression of CACNA2D3 induced mitochondrial-mediated apoptosis, upregulation of NLK (through the Wnt/Ca²⁺ pathway) and inhibition of the epithelial-to-mesenchymal transition. Ectopic expression of CACNA2D3 inhibited cell proliferation, migration, invasion, and tumor growth in vitro and in vivo, whereas CACNA2D3 depletion inhibited cell viability and invasion. Furthermore, we confirmed that CACNA2D3 increased NLK expression in vitro by immunostaining and found that downregulation of CACNA2D3 in glioma cells and high-grade glioma tissue was accompanied by increased methylation. A reporter assay showed increased luciferase activity in NLK knockdown glioma cells and transcriptional activity of β-cantenin/TCF was remarkably enhanced, which further confirmed that NLK antagonizes Wnt signaling-mediated anchorage-dependent and independent cell proliferation and invasion. This mechanism may contribute to a better understanding of glioma cancer pathogenesis and facilitate the development of new therapeutic strategies for the treatment of this disease. © 2016 Wiley Periodicals, Inc.