Although dietary calcium intake has long been recommended for disease prevention, the influence of calcium in development of cancer in the upper gastrointestinal tract has not been explored. Here, we assess the roles of calcium and calcium-sensing receptor (CaSR) in gastric cancer development. CaSR expression was enhanced in gastric cancer specimens, which positively correlated with serum calcium concentrations, tumor progression, poor survival, and male gender in gastric cancer patients. CaSR and transient receptor potential cation channel subfamily V member 4 (TRPV4) were colocalized in gastric cancer cells, and CaSR activation evoked TRPV4-mediated Ca 2þ entry. Both CaSR and TRPV4 were involved in Ca 2þ -induced proliferation, migration, and invasion of gastric cancer cells through a Ca 2þ /AKT/b-catenin relay, which occurred only in gastric cancer cells or normal cells overexpressing CaSR. Tumor growth and metastasis of gastric cancer depended on CaSR in nude mice. Overall, our findings indicate that calcium may enhance expression and function of CaSR to potentially promote gastric cancer, and that targeting the novel CaSR/TRPV4/Ca 2þ pathway might serve as preventive or therapeutic strategies for gastric cancer.

Purinergic signaling is important for many biological processes in humans. Purinoceptors P2Y are widely distributed in human digestive system and different subtypes of P2Y receptors mediate different physiological functions from metabolism, proliferation, differentiation to apoptosis etc. The P2Y receptors are essential in many gastrointestinal functions and also involve in the occurrence of some digestive diseases. Since different subtypes of P2Y receptors are present on the same cell of digestive organs, varying subtypes of P2Y receptors may have opposite or synergetic functions on the same cell. Recently, growing lines of evidence strongly suggest the involvement of P2Y receptors in the pathogenesis of several digestive diseases. In this review, we will focus on their important roles in the development of digestive inflammation and cancer. We anticipate that as the special subtypes of P2Y receptors are studied in depth, specific modulators for them will have good potentials to become promising new drugs to treat human digestive diseases in the near future.

Background Although the aberrant expression and function of most Ca2+-permeable channels are known to promote gastrointestinal tumors, the association between transient receptor potential vanilloid receptor 1 (TRPV1) channels and gastric cancer (GC) has not yet been explored. Herein, we sought to determine the role of TRPV1 channels in the development of GC and to elucidate the underlying molecular mechanisms involved therein. Methods Immunohistochemistry, qPCR, Western blot, immunofluorescence assays were used to detect the mRNA and protein expression of TRPV1 in GC cells and tissues, and the clinical significance of TRPV1 in GC was also studied by clinicopathologic analysis. CCK8, colony formation, flow cytometry assays were used to detect the proliferation and survival of GC cells, while transwell assay was used to detect migration and invasion of GC cells in vitro. Tumor xenograft and peritoneal dissemination assays in nude mice were used to examine the role of TRPV1 in GC development in vivo. Results TRPV1 expression was significantly downregulated in human primary GC tissues compared to their adjacent tissues. The decreased expression of TRPV1 proteins in GC tissues was positively correlated with tumor size, histological grade, lymphatic metastasis, clinical stage, and was strongly correlated with poor prognosis of GC patients. Moreover, the expression of TRPV1 was closely correlated with Ki67, VEGFR, and E-cadherin, all of which are the well-known cancer markers for proliferation and metastasis. TRPV1 proteins were predominately expressed on the plasma membrane in several GC cell lines. TRPV1 overexpression blocked cell cycle at G1 phase to inhibit GC cell proliferation and attenuated migration and invasion of GC cells in vitro, but TRPV1 knockdown increased these parameters. TRPV1 significantly reduced gastric tumor size, number and peritoneal dissemination in vivo. Mechanistically, TRPV1 overexpression in GC cells increased [Ca2+]i, activated CaMKKβ and AMPK phosphorylation, and decreased expression of cyclin D1 and MMP2, while TRPV1 knockdown induced the opposite effects. Conclusions TRPV1 uniquely suppresses GC development through a novel Ca2+/CaMKKβ/AMPK pathway and its downregulation is correlated with poor survival of human GC patients. Thus, TRPV1 upregulation and its downstream signaling may represent a promising target for GC prevention and therapy.

Background and Purpose: As little is known about the effect of caffeine, one of the most widely consumed substances worldwide, on intestinal function, we aimed to study its action on intestinal anion secretion and the underlying molecular mechanisms. Experimental Approach: Anion secretion and channel expression were examined in mouse duodenal epithelium by Ussing chambers and immunocytochemistry. Ca 2+ imaging was also performed in intestinal epithelial cells (IECs). Key Results: Caffeine (10 mM) markedly increased mouse duodenal short-circuit current (I sc), which was attenuated by a removal of either Cl − or HCO 3 − , Ca 2+-free serosal solutions and selective blockers of store-operated Ca 2+ channels (SOC/Ca 2+ release-activated Ca 2+ channels), and knockdown of Orai1 channels on the serosal side of duodenal tissues. Caffeine induced SOC entry in IEC, which was inhibited by ruthenium red and selective blockers of SOC. Caffeine-stimulated duodenal I sc was inhibited by the endoplasmic reticulum Ca 2+ chelator (N,N,N′,N′-tetrakis(2-pyridylmethyl) ethylenediamine), selective blockers (ruthenium red and dantrolene) of ryanodine receptors (RyR), and of Ca 2+-activated Cl − channels (niflumic acid and T16A). There was synergism between cAMP and Ca 2+ signalling, in which cAMP/PKA promoted caffeine/Ca 2+-mediated anion secretion. Expression of STIM1 and Orai1 was detected in mouse duodenal mucosa and human IECs. The Orai1 proteins were primarily colocated with the basolateral marker Na + , K +-ATPase. Conclusions and Implications: Caffeine stimulated intestinal anion secretion mainly through the RyR/Orai1/Ca 2+ signalling pathway. There is synergism between cAMP/PKA and caffeine/Ca 2+-mediated anion secretion. Our findings suggest that a caffeine-mediated RyR/Orai1/Ca 2+ pathway could provide novel potential drug targets to control intestinal anion secretion. 1 | INTRODUCTION Caffeine is a well-known constituent of coffee, cacao, and tea, and one of the most widely consumed substances in the world. In 2014, about 85% of American adults ingested, on average, 164-mg caffeine daily (Mitchell, Knight, Hockenberry, Teplansky, & Hartman, 2014). Caffeine intake induces several physiological effects, including stimulation of nervous and musculoskeletal systems, relaxation of bronchial Abbreviations: [Ca 2+ ]cyt, cytosolic Ca 2+ concentration; 2-APB, 2-aminoethoxydiphenyl borate; CaCC, Ca 2+-activated Cl − channels; CFTR, cystic fibrosis transmembrane conductance regulator; CRAC, Ca 2+ release-activated Ca 2+ channels; DNDS

Although purinegic signaling is important in regulating gastric physiological functions, it is currently unknown for its role in gastric cancer (GC). We demonstrate for the first time that the expression of P2Y6 receptors was markedly down-regulated in human GC cells and primary GC tissues compared to normal tissues, while the expression of P2Y2 and P2Y4 receptors was up-regulated in GC cells. Moreover, the expression levels of P2Y6 receptors in GC tissues were correlated to tumor size, differentiation, metastasis to lymph nodes, and the survival rate of the patients with GC. Ncleotides activated P2Y6 receptors to raise cytosolic Ca2+ concentrations in GC cells through store-operated calcium entry (SOCE), and then mediated Ca2+-dependent inhibition of β-catenin and proliferation, eventually leading to GC suppression. Furthermore, UTP particularly blocked the G1/S transition of GC cells but did not induce apoptosis. Collectively, we conclude that nucleotides activate P2Y6 receptors to suppress GC growth through a novel SOCE/Ca2+/β-catenin-mediated anti-proliferation of GC cells, which is different from the canonical SOCE/Ca2+-induced apoptosis in other tumors.