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Objective Evidence suggests that calcium release from the endoplasmic reticulum (ER) can be induced to cause calcium overload, which in turn can trigger mitochondrial-dependent apoptosis. Dysregulation of systemic calcium homeostasis and changing levels of calcium-binding proteins have been shown to be associated with the malignant behavior of tumors. However, the precise molecular mechanism underlying Nasopharyngeal carcinoma (NPC) remains uncertain. Methods Reticulocalbin (RCN2) expression in NPC was assessed using GEO database, western blot analysis and qRT-PCR. Apoptosis was assessed using flow cytometric analysis and the expression levels of apoptosis-related proteins were determined using western blot analysis. Intracellular calcium ion concentrations were measured using fluorescence imaging. The findings from these analyses were validated in vitro using nude mice models. Luciferase and ChIP assays were used to measure transcriptional regulation. Clinical significance was evaluated using tissue microarray analysis (n=150). Results Our results showed that RCN2 promotes malignancy by causing Ca2+ flow imbalance, which leads to the initiation of the stress-mediated mitochondrial apoptosis pathway. We demonstrate that calreticulin (CALR) resides primarily in the endoplasmic reticulum and interacts with RCN2. Moreover, the transcription factors YY1 and homeobox protein goosecoid (GSC) both contribute to the initiation of RCN2 transcription by directly binding to the predicted promoter region of RCN2. Finally, high expression of RCN2 combined with high expression of GSC and YY1 may serve as an important clinical biomarker of poor prognosis in patients with NPC. Conclusion YY1 and GSC are upstream regulators of RCN2, involved in mitochondrial calcium overload and stress-induced mitochondrial apoptosis. Thus, they can play significant role in the malignant development of NPCs.

Background Cluster of differentiation (CD) 73, encoded by the NT5E gene, plays important enzymatic and non-enzymatic roles in cells. There is growing evidence show that CD73 is a key regulator in the development of tumor. Nasopharyngeal carcinoma (NPC) is one of the most common cancers in east and southeast Asia. It is urgent to know more about the mechanism of NPC development and find diagnose markers for the patients.Methods and Results Western blot, IHC and qRT-PCR were used to investigate the expression level of CD73 in NPC and we found NPC tissues had higher expression of CD73 than normal tissues. We also detected the relationship between its expression level with the clinicopathology and prognosis of NPC patients. The results showed CD73 expression was related to the clinical stages, lymph node metastasis and survival state of NPC patients. More importantly, patients with higher expression of CD73 had poorer prognosis. Then, CD73 was knocked down in NPC cells (CNE2 and CNE1), and the effects of CD73 on cell proliferation and migration were investigated by CCK8, colony formation, Transwell and wound-healing assays. We found knocking down the expression of CD73 in NPC cells could inhibit cells malignant phenotype.Conclusion CD73 plays important roles in NPC malignant behavior and might be used as a novel target for the diagnose and treatment of NPC.

Dysregulated microRNAs (miRNAs) are involved in carcinoma progression, metastasis, and poor prognosis. We demonstrated that in nasopharyngeal carcinoma (NPC), transactivated MIR106A-5p promotes a malignant phenotype by functioning as a macroautophagy/autophagy suppressor by targeting BTG3 (BTG anti-proliferation factor 3) and activating autophagy-regulating MAPK signaling. MIR106A-5p expression was markedly increased in NPC cases based on quantitative real-time PCR, miRNA microarray, and TCGA database analysis findings. Moreover, MIR106A-5p was correlated with advanced stage, recurrence, and poor clinical outcomes in NPC patients. In addition to three-dimensional cell culture assays, zebrafish and BALB/c mouse tumor models revealed that overexpressed MIR106A-5p targeted BTG3 and accelerated the NPC malignant phenotype by inhibiting autophagy. BTG3 promoted autophagy, and its expression was correlated with poor prognosis in NPC. Attenuation of autophagy, mediated by the MIR106A-5p-BTG3 axis, occurred because of MAPK pathway activation. MIR106A-5p overexpression in NPC was due to increased transactivation by EGR1 and SOX9. Our findings may lead to novel insights into the pathogenesis of NPC. Abbreviations: ACTB: actin beta; ATG: autophagy-related; ATG5: autophagy related 5; BLI: bioluminescence; BTG3: BTG anti-proliferation factor 3; CASP3: caspase 3; ChIP: chromatin immunoprecipitation; CQ: chloroquine; Ct: threshold cycle; DAPI: 4��,6-diamidino-2-phenylindole; DiL: 1,1��-dioctadecyl-3,3,3��,3��-tetramethylindocarbocyanine perchlorate; EBSS: Earle���s balanced salt solution; EGR1: early growth response 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GEO: Gene Expression Omnibus; GFP: green fluorescent protein; IF: immunofluorescence; IHC: immunohistochemistry; ISH: in situ hybridization; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MIR106A-5p: microRNA 106a-5p; miRNAs: microRNAs; MKI67: marker of proliferation ki-67; mRNA: messenger RNA; MTOR: mechanistic target of rapamycin kinase; NPC: nasopharyngeal carcinoma; qRT-PCR: quantitative real-time PCR; siRNA: small interfering RNA; SOX9: SRY-box transcription factor 9; SQSTM1: sequestosome 1; TCGA: The Cancer Genome Atlas; WB: western blot.