Apart from β-
catenin accumulation, loss of 3p21 is one of the most frequent genetic alterations in numerous
malignancies including
nasopharyngeal carcinoma (NPC). Herein, we characterized a novel candidate tumor suppressor gene (TSG) CACNA2D3, a voltage-dependent subunit alpha 2 delta 3 of a
calcium channel complex. Downregulation of CACNA2D3 was frequently detected in primary NPCs and NPC cell lines compared with their nontumorigenic counterparts. Attenuated CACNA2D3 expression may be associated with loss of heterozygosity (LOH) at intragenic single-nucleotide polymorphism sites (rs589281, rs1449325 and rs6797113) and/or epigenetic silencing by methylation and
histone deacetylation. Given the extensive effects of
calcium in
cancer, we then investigated the
tumor suppressive role and underlying mechanism of CACNA2D3 in the development and progression of NPC. CACNA2D3 was stably transfected into NPC cell lines (C666 and SUNE1) at levels comparative with the normal nasopharynx, alongside
siRNA-mediated silencing in an immortalized nasopharyngeal epithelial cell line (NP69) to conduct in vivo and in vitro functional assays. Our findings show that CACNA2D3-mediated increase in intracellular
calcium (Ca2+) can induce mitochondrial-mediated apoptosis and activation of NLK (through the Wnt/Ca2+ pathway) to antagonize Wnt signaling-mediated anchorage-dependent and independent cell proliferation (via CCND1 and CMYC), invasion (via MMP7) and epithelial-to-mesynchemal transition (via SNAIL). As the expression pattern of
calcium channels and their degree of functionality can change with the progression of
cancer, CACNA2D3 may indeed be a promising
biomarker for NPC. Our study also warrants further exploration in the potential
therapeutic use of existing epigenetic targeting drugs (e.g.,
5-azacytidine, SAHA) to reconstitute CACNA2D3-associated
tumor suppression in NPC.