PRKAR2A deficiency protects mice from experimental colitis by increasing IFN-stimulated gene expression and modulating the intestinal microbiota.

Protein kinase A (PKA) plays an important role in regulating inflammation via its catalytic subunits. Recently, PKA regulatory subunits have been reported to directly modulate some signaling pathways and alleviate inflammation. However, the role of PKA regulatory subunits in colonic inflammation remains unclear. Therefore, we conducted this study to investigate the role of the PKA regulatory subunit PRKAR2A in colitis. We observed that PRKAR2A deficiency protected mice from dextran sulfate sodium (DSS)-induced experimental colitis. Our experiments revealed that the intestinal epithelial cell-specific deletion of Prkar2a contributed to this protection. Mechanistically, the loss of PRKAR2A in Prkar2a-/- mice resulted in an increased IFN-stimulated gene (ISG) expression and altered gut microbiota. Inhibition of ISGs partially reversed the protective effects against DSS-induced colitis in Prkar2a-/- mice. Antibiotic treatment and cross-fostering experiments demonstrated that the protection against DSS-induced colitis in Prkar2a-/- mice was largely dependent on the gut microflora. Altogether, our work demonstrates a previously unidentified function of PRKAR2A in promoting DSS-induced colitis.

DEPDC1B promotes migration and invasion in pancreatic ductal adenocarcinoma by activating the Akt/GSK3ß/Snail pathway.

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease, which frequently presents with distant metastasis. Further understanding of the molecular mechanism of PDAC is helpful to uncover novel and effective therapeutic strategies. DEP domain containing 1B (DEPDC1B) is known to play a role in the carcinogenesis and metastasis of several common types of cancer; however, its biological function and molecular mechanism in PDAC progression remain unclear. In the present study, the expression levels of DEPDC1B were detected in 79 pairs of PDAC and adjacent non-cancerous tissues. Patients with PDAC that exhibited higher DEPDC1B expression levels, were shown to have a poorer prognosis. Functional studies showed that knocking down DEPDC1B inhibited PDAC cell migration and invasion, while overexpressing DEPDC1B promoted these processes. Western blotting analysis and immunofluorescence demonstrated that DEPDC1B overexpression induced the epithelial-to-mesenchymal transition (EMT). Further mechanistic studies revealed that DEPDC1B was able to activate the Akt/glycogen synthase kinase-3ß (GSK3ß)/Snail signaling pathway. In conclusion, the results of the present study showed that DEPDC1B may serve as an oncogene that contributes to PDAC cell migration and invasion by inducing EMT via Akt/GSK3ß/Snail pathway activation.

SKA1 regulates actin cytoskeleton remodelling via activating Cdc42 and influences the migration of pancreatic ductal adenocarcinoma cells.

OBJECTIVES: Spindle and kinetochore-associated protein 1(SKA1), originally identified as a protein essential for proper chromosome segregation, has been recently linked to multiple malignancies. This study aimed to explore the biological, clinical role and molecular mechanism of SKA1 in pancreatic carcinogenesis. MATERIALS AND METHODS: SKA1 expression was detected in 145 pancreatic ductal adenocarcinoma (PDAC) specimens by immunohistochemistry. Biological behaviour assays were used to determine the role of SKA1 in PDAC progression in vitro and in vivo. Using isobaric tags for relative and absolute quantitation (iTRAQ), SKA1's downstream proteins were examined. Moreover, cytochalasin B and ZCL278 were used to explore the changes of SKA1-induced signalling and cell morphology, with further confirmation by immunoblotting and immunofluorescence assays. RESULTS: Increased SKA1 expression was significantly correlated with tumour size and cellular differentiation degree in PDAC tissues. Furthermore, elevated levels of SKA1 reflected shorter overall survival (P = .019). As for biological behaviour, SKA1 acted as a tumour promotor in PDAC, overexpression of SKA1 facilitates cell proliferation, migration and invasion in vitro and in vivo. Mechanistically, we demonstrated that SKA1 enhanced pancreatic cancer aggressiveness by inhibiting G2/M arrest and regulating actin cytoskeleton organization via activating Cdc42. CONCLUSIONS: This study revealed novel roles for SKA1 as an important regulator of actin cytoskeleton organization and an oncogene in PDAC cells, which may provide insights into developing novel therapeutics.

Lemur tyrosine kinase 2 acts as a positive regulator of NF-κB activation and colon cancer cell proliferation.

Lemur tyrosine kinase 2 (LMTK2) belongs to both protein kinase and tyrosine kinase families. LMTK2 is less studied and little is known about its function. Here we demonstrate that LMTK2 modulates NF-κB activity and functions to promote colonic tumorigenesis. We found that LMTK2 protein was abundant in colon cancer cells and LMTK2 knockdown (LMTK2-KD) inhibited proliferation of colon cancer cells through inactivating NF-κB. In unstimulated condition, LMTK2 modulated NF-κB through inhibiting phosphorylation of p65 at Ser468. Mechanistically, LMTK2 phosphorylated protein phosphatase 1A (PP1A) to prevent PP1A from dephosphorylating p-GSK3ß(Ser9). The p-GSK3ß(Ser9) could not phosphorylate p65 at Ser468, which maintained the basal NF-κB activity. LMTK2 also modulated TNFα-activated NF-κB. LMTK2-KD repressed TNFα-induced IKKß phosphorylation, IκBα degradation and NF-κB activation, implying that LMTK2 modulates TNFα-activated NF-κB via IKK. These results suggest that LMTK2 modulates basal and TNFα-induced NF-κB activities in different mechanisms. Animal studies show that LMTK2-KD suppressed colon cancer cell xenograft growth, decreased PP1A phosphorylation and increased p-p65(Ser468). Our results reveal the role and underlying mechanism of LMTK2 in colonic tumorigenesis and suggest that LMTK2 may serve as a potential target for chemotherapy of colon cancer.

EI24 Suppresses Tumorigenesis in Pancreatic Cancer via Regulating c-Myc.

The EI24 autophagy-associated transmembrane protein is frequently associated with tumor growth and patient survival. In the present study, we found that EI24 was downregulated in pancreatic ductal adenocarcinoma (PDAC) tissues compared with adjacent normal tissues and was associated with cancer cell differentiation. Overexpression of EI24 suppressed cancer cell growth in vitro and in vivo and induced cell cycle S phase arrest, with no impact on caspase-dependent apoptosis. EI24 overexpression also resulted in reduced c-Myc expression, an oncogene in PDAC, accompanied with increased LC3B-II formation, increased Beclin-1, and diminished p62. Together, we propose that EI24 suppresses cell proliferation and prompts cell cycle arrest in pancreatic cancer cells by activating the autophagic lysosomal degradation of c-Myc. Our results suggest a potential mechanism underlying the antitumor effects of EI24 in PDAC and provide insight into the crosstalk between autophagy and cell proliferation involving a possible EI24/Beclin-1/p62/c-Myc signaling pathway.

Tp53 Mutation Inhibits Ubiquitination and Degradation of WISP1 via Down-Regulation of Siah1 in Pancreatic Carcinogenesis.

Wnt1 inducible signaling pathway protein-1 (WISP1) may play an important role in promoting carcinogenesis. However, the biological function and underlying mechanism of WISP1 in pancreatic carcinogenesis still remains enigmatic. In this study, immunochemistry staining showed that protein levels of WISP1 were more significantly upregulated in pancreatic ductal adenocarcinoma (PDAC) tissues with Tp53 mutation than in PDAC tissues with Tp53 wild-type. In addition, a significant correlation was observed between increased malignant phenotype of tumors from well-differentiated adenocarcinoma tissues to moderately- or poorly-differentiated adenocarcinoma tissues shifting from cytoplasmic expression to nuclear accumulation of WISP1. Interestingly, WISP1 expression was correlated with the poor prognosis in PDAC patients with Tp53 mutation. Also, the biological function analysis showed that WISP1 may act as a potential oncogene in PDAC cells. In addition, immunofluorescence analysis showed that Tp53 mutation promoted WISP1 expression in PanIN and PDAC cells, while Siah E3 Ubiquitin Protein Ligase 1 (Siah1) inhibited WISP1 expression in PDAC cells. Moreover, through immunoprecipitation, immunoblotting analysis, in vitro binding assay, and ubiquitination assay, we found that Tp53 mutation inhibited ubiquitination and degradation of Siah1-dependent WISP1. Therefore, Tp53 mutation-Siah1-WISP1 is a new signaling pathway, playing an important role in pancreatic carcinogenesis.

Niacin ameliorates ulcerative colitis via prostaglandin D2-mediated D prostanoid receptor 1 activation.

Niacin, as an antidyslipidemic drug, elicits a strong flushing response by release of prostaglandin (PG) D2 However, whether niacin is beneficial for inflammatory bowel disease (IBD) remains unclear. Here, we observed niacin administration-enhanced PGD2 production in colon tissues in dextran sulfate sodium (DSS)-challenged mice, and protected mice against DSS or 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in D prostanoid receptor 1 (DP1)-dependent manner. Specific ablation of DP1 receptor in vascular endothelial cells, colonic epithelium, and myeloid cells augmented DSS/TNBS-induced colitis in mice through increasing vascular permeability, promoting apoptosis of epithelial cells, and stimulating pro-inflammatory cytokine secretion of macrophages, respectively. Niacin treatment improved vascular permeability, reduced apoptotic epithelial cells, promoted epithelial cell update, and suppressed pro-inflammatory gene expression of macrophages. Moreover, treatment with niacin-containing retention enema effectively promoted UC clinical remission and mucosal healing in patients with moderately active disease. Therefore, niacin displayed multiple beneficial effects on DSS/TNBS-induced colitis in mice by activation of PGD2/DP1 axis. The potential efficacy of niacin in management of IBD warrants further investigation.

Combination of Five Body Positions Can Effectively Improve the Rate of Gastric Mucosa's Complete Visualization by Applying Magnetic-Guided Capsule Endoscopy.

Objectives. Achieving a comprehensive view of gastric mucosa has been a challenge for magnetic-guided capsule endoscopy (MGCE) for years. This study works on optimizing the performance of MGCE by changing the conventional positions to the five body positions. Methods. Sixty patients were enrolled in the study and underwent MGCE. All patients were asked to adopt five body positions (left lateral, supine, right lateral, knee-chest, and sitting). In each position, the ability to visualize the six gastric landmarks (cardia, fundus, body, angulus, antrum, and pylorus) was assessed. Rates of complete visualization were calculated for different position combinations. Results. Supine position was the best for cardia and body visualization (91.7% and 86.7%, resp., p < 0.001). Left lateral position was the best for fundus visualization (91.7%, p < 0.001). Knee-chest position was the best for angulus observation (80.0%, p < 0.001). Right lateral and sitting positions were the best for antrum observation (88.3% and 90.0%, resp., p < 0.001). Right lateral position was the best for pylorus observation (81.7%, p < 0.001). The supine + right lateral + knee-chest combination achieved better angulus visualization than conventional 3-position combination (93.3% versus 63.3%, p < 0.001). Five-position combination significantly improved the comprehensive gastric landmark visualization (93.3%, p < 0.001). Conclusion. Compared with 3-position combination, 5-position combination should be adopted for gastric mucosal visualization by MGCE.

Smad4-dependent suppressor pituitary homeobox 2 promotes PPP2R2A-mediated inhibition of Akt pathway in pancreatic cancer.

The importance of Pituitary homeobox 2 (Pitx2) in malignancy remains enigmatic, and Pitx2 has not been previously implicated in pancreatic ductal adenocarcinoma (PDAC). In this study, we performed gene expression profiling of human PDAC tissues and identified Pitx2 as a promising candidate. Pitx2 expression was decreased from 2.6- to 19-fold in human PDAC tissues from microarray units. Immunochemistry staining showed that Pitx2 expression was moderate to intense in normal pancreatic and pancreatic intraepithelial neoplastic lesions, whereas low in human PDAC tissues. The Pitx2 levels correlated with overall patient survival post-operatively in PDAC. Induction of Pitx2 expression partly inhibited the malignant phenotype of PDAC cells. Interestingly, low Pitx2 expression was correlated with Smad4 mutant inactivation, but not with Pitx2 DNA-methylation. Furthermore, Smad4 protein bound to Pitx2 promoter and stimulated Pitx2 expression in PDAC. In addition, Pitx2 protein bound to the promoter of the protein phosphatase 2A regulatory subunit B55α (PPP2R2A) and upregulated PPP2R2A expression, which may activate dephosphorylation of Akt in PDAC. These findings provide new mechanistic insights into Pitx2 as a tumor suppressor in the downstream of Smad4. And Pitx2 protein promotes PPP2R2A expression which may inhibit Akt pathway. Therefore, we propose that the Smad4-Pitx2-PPP2R2A axis, a new signaling pathway, suppresses the pancreatic carcinogenesis.

Overexpression of CX3CR1 is associated with cellular metastasis, proliferation and survival in gastric cancer.

The CX3CR1/CX3CL1 axis is involved in the metastasis and prognosis of many types of cancer; however, whether CX3CR1 is expressed in gastric cancer cells and whether it participates in gastric cancer metastasis remain unknown. We investigated the expression of CX3CR1 in gastric cancer tissues and non­neoplastic gastric tissues in vivo and in gastric cancer cell lines and a gastric epithelial cell line in vitro, and then the functional roles of CX3CR1 in cellular metastasis, proliferation and survival were explored. We observed that CX3CR1 was highly expressed in gastric cancer tissues in vivo and was related to lymph node metastasis, higher clinical TNM stage and larger tumor size. In vitro, CX3CR1 overexpression promoted gastric cancer cell migration, invasion, proliferation and survival. Additionally, different from several chemokine receptors, CX3CR1 was also expressed in non-neoplastic gastric tissues and in gastric epithelial cells and played a functional role in vitro. Notably, gastric cancer tissues expressed higher CX3CR1 compared with that in the non-neoplastic gastric tissues in vivo, while in vitro, CX3CR1 expresssion in the gastric cancer cell lines was equivalent or significantly lower than that in the gastric epithelial cell line, which suggests that the high expression of CX3CR1 in gastric cancer in vivo might be induced, not constitutive. Altogether, our findings suggest that on the one hand overexpression of CX3CR1 promoted gastric cancer metastasis, proliferation and survival; on the other hand, appropriate expression of CX3CR1 in normal gastric tissues may play a physiological role in tissue remodeling after injury and/or epithelial renewal. Additionally, the tumor microenvironment may play an important role in the high expression of CX3CR1 in gastric cancer cells.

Prior to Foxp3⁺ regulatory T-cell induction, interleukin-10-producing B cells expand after Helicobacter pylori infection.

Regulatory T (Treg) cells play a critical role in Helicobacter pylori immune evasion and persistent infection. In addition to Treg cells, it is still unknown whether a newly defined B-cell subset, interleukin (IL)-10-producing B cells, is involved. Using a mouse model of H. pylori infection, we investigated the dynamic changes of IL-10-producing B cells and Foxp3(+) Treg cells in gastrointestinal mucosa, spleen and mesenteric lymph nodes following H. pylori infection. We observed that in addition to Foxp3(+) Treg cells, IL-10-producing B cells could also be induced after H. pylori infection and they expanded earlier than Foxp3(+) Treg cells did. Moreover, the regulatory immune responses induced by H. pylori were not limited to gastric mucosa. Our findings may provide new clues for further research on H. pylori immune evasion and diseases associated with H. pylori infection.