Activation of Signal Transduction and Activator of Transcription 3 Signaling Contributes to Helicobacter-Associated Gastric Epithelial Proliferation and Inflammation.

BACKGROUND/AIM: Although IL-6-mediated activation of the signal transduction and activator of transcription 3 (STAT3) axis is involved in inflammation and cancer, the role of STAT3 in Helicobacter-associated gastric inflammation and carcinogenesis is unclear. This study investigated the role of STAT3 in gastric inflammation and carcinogenesis and examined the molecular mechanism of Helicobacter-induced gastric phenotypes. METHODS: To evaluate the contribution of STAT3 to gastric inflammation and carcinogenesis, we used wild-type (WT) and gastric epithelial conditional Stat3-knockout (Stat3Δgec ) mice. Mice were infected with Helicobacter felis and euthanized at 18 months postinfection. Mouse gastric organoids were treated with recombinant IL-6 (rIL-6) or rIL-11 and a JAK inhibitor (JAKi) to assess the role of IL-6/STAT3 signaling in vitro. RESULTS: Inflammation and mucous metaplasia were more severe in WT mice than in Stat3Δgec mice. The epithelial cell proliferation rate and STAT3 activation were increased in WT mice. Application of rIL-6 and rIL-11 induced expression of intestinal metaplasia-associated genes, such as Tff2; this induction was suppressed by JAKi administration. CONCLUSIONS: Loss of STAT3 signaling in the gastric mucosa leads to decreased epithelial cell proliferation, atrophy, and metaplasia in the setting of Helicobacter infection. Therefore, activation of STAT3 signaling may play a key role in Helicobacter-associated gastric carcinogenesis.

Helicobacter-induced gastric inflammation alters the properties of gastric tissue stem/progenitor cells.

BACKGROUND: Although Helicobacter-induced gastric inflammation is the major predisposing factor for gastric carcinogenesis, the precise mechanism by which chronic gastritis causes gastric cancer remains unclear. Intestinal and spasmolytic polypeptide-expressing metaplasia (SPEM) is considered as precancerous lesions, changes in epithelial tissue stem/progenitor cells after chronic inflammation has not been clarified yet. In this study, we utilized three-dimensional gastric epithelial cell culture systems that could form organoids, mimicking gastric epithelial layer, and characterized the changes in epithelial cells after chronic Helicobacter felis infection. METHODS: We used three mice model; 1) long-term H. felis infection, 2) H. felis eradication, and 3) MNU chemical carcinogenesis model. We performed cRNA microarray analysis after organoid culture, and analyzed the effects of chronic gastric inflammation on tissue stem cells, by the size of organoid, mRNA expression profile and immunohistochemical analysis. RESULTS: The number of organoids cultured from gastric epithelial cells was significantly higher in organoids isolated from H. felis-infected mice compared with those from uninfected gastric mucosa. Based on the mRNA expression profile, we found that possible stem cell markers such as Cd44, Dclk1, and genes associated with the intestinal phenotype, such as Villin, were increased in organoids isolated from H. felis-infected mucosa compared with the control. The upregulation of these genes were cancelled after H. felis eradication. In a xenograft model, tumors were generated only from organoids cultured from carcinogen-treated gastric mucosa, not from H. felis infected mucosa or control organoids. CONCLUSIONS: Our results suggested that, as a possible mechanism of gastric carcinogenesis, chronic inflammation induced by H. felis infection increased the number of tissue stem/progenitor cells and the expression of stem cell markers. These findings suggest that chronic inflammation may alter the direction of differentiation toward undifferentiated state and that drawbacks may enable cells to redifferentiate to intestinal metaplasia or neoplasia.

c-Jun N-terminal kinase in pancreatic tumor stroma augments tumor development in mice.

Pancreatic ductal adenocarcinoma (PDAC) is a life-threatening disease and there is an urgent need to develop improved therapeutic approaches. The role of c-Jun N-terminal kinase (JNK) in PDAC stroma is not well defined even though dense desmoplastic reactions are characteristic of PDAC histology. We aimed to explore the role of JNK in PDAC stroma in mice. We crossed Ptf1aCre/+ ;KrasG12D/+ mice with JNK1-/- mice to generate Ptf1aCre/+ ;KrasG12D/+ ;JNK1-/- (Kras;JNK1-/- ) mice. Tumor weight was significantly lower in Kras;JNK1-/- mice than in Kras;JNK1+/- mice, whereas histopathological features were similar. We also transplanted a murine PDAC cell line (mPC) with intact JNK1 s.c. into WT and JNK1-/- mice. Tumor diameters were significantly smaller in JNK1-/- mice. Phosphorylated JNK (p-JNK) was activated in α-smooth muscle actin (SMA)-positive cells in tumor stroma, and mPC-conditioned medium activated p-JNK in tumor-associated fibroblasts (TAF) in vitro. Relative expression of Ccl20 was downregulated in stimulated TAF. Ccl20 is an important chemokine that promotes CD8+ T-cell infiltration by recruitment of dendritic cells, and the number of CD8+ T cells was decreased in Kras;JNK1+/- mice compared with Kras;JNK1-/- mice. These results suggest that the cancer secretome decreases Ccl20 secretion from TAF by activation of JNK, and downregulation of Ccl20 secretion might be correlated with reduction of infiltrating CD8+ T cells. Therefore, we concluded that inhibition of activated JNK in pancreatic tumor stroma could be a potential therapeutic target to increase Ccl20 secretion from TAF and induce accumulation of CD8+ T cells, which would be expected to enhance antitumor immunity.

Diagnosis of pancreatic lesions collected by endoscopic ultrasound-guided fine-needle aspiration using next-generation sequencing.

Endoscopic ultrasound-guided fine-needle aspiration (EUF-FNA) has improved the diagnosis of pancreatic lesions. Next-generation sequencing (NGS) facilitates the production of millions of sequences concurrently. Therefore, in the current study, to improve the detectability of oncogenic mutations in pancreatic lesions, an NGS system was used to diagnose EUS-FNA samples. A total of 38 patients with clinically diagnosed EUS-FNA specimens were analyzed; 27 patients had pancreatic ductal adenocarcinoma (PDAC) and 11 had non-PDAC lesions. DNA samples were isolated and sequenced by NGS using an Ion Personal Genome Machine system. The Cancer Hotspot Panel v2, which includes 50 cancer-related genes and 2,790 COSMIC mutations, was used. A >2% mutation frequency was defined as positive. KRAS mutations were detected in 26 of 27 PDAC aspirates (96%) and 0 of 11 non-PDAC lesions (0%). The G12, G13, and Q61 KRAS mutations were found in 25, 0, and 1 of the 27 PDAC samples, respectively. Mutations were confirmed by TaqMan® polymerase chain reaction analysis. TP53 mutations were detected in 12 of 27 PDAC aspirates (44%). SMAD4 was observed in 3 PDAC lesions and cyclin-dependent kinase inhibitor 2A in 4 PDAC lesions. Therefore, the current study was successfully able to develop an NGS assay with high clinical sensitivity for EUS-FNA samples.

Intestine-specific homeobox (ISX) induces intestinal metaplasia and cell proliferation to contribute to gastric carcinogenesis.

BACKGROUND: Helicobacter pylori induces chronic inflammation and intestinal metaplasia (IM) through genetic and epigenetic changes and activation of intracellular signaling pathways that contribute to gastric carcinogenesis. However, the precise mechanism of IM in gastric carcinogenesis has not been fully elucidated. We previously found that intestine-specific homeobox (ISX) mRNA expression increased in organoids cultured from Helicobacter-infected mouse mucosa. In this study, we elucidate the role of ISX in the development of IM and gastric carcinogenesis. METHODS: ISX expression was assessed in Helicobacter-infected mouse and human gastric mucosa. MKN45 gastric cancer cells were co-cultured with H. pylori to determine whether Helicobacter infection induced ISX expression. We established stable MKN45 transfected cells expressing ISX (Stable-ISX MKN45) and performed a spheroid colony formation assay and a xenograft model. We performed ISX immunohistochemistry in cancer and adjacent gastric tissues. RESULTS: ISX expression was increased in mouse and human gastric mucosa infected with Helicobacter. The presence of IM and H. pylori infection in human stomach was correlated with ISX expression. H. pylori induced ISX mRNA and protein expression. CDX1/2, cyclinD1, and MUC2 were upregulated in Stable-ISX MKN45, whereas MUC5AC was downregulated. Stable-ISX MKN45 cells formed more spheroid colonies, and had high tumorigenic ability. ISX expression in gastric cancer and adjacent mucosa were correlated. CONCLUSIONS: ISX expression induced by H. pylori infection may lead to IM and hyperproliferation of gastric mucosa through CDX1/2 and cyclinD1 expression, contributing to gastric carcinogenesis.

Efficacy of plastic stent placement inside bile ducts for the treatment of unresectable malignant hilar obstruction (with videos).

BACKGROUND: Recent reports have addressed the utility of plastic stent (PS) placement inside bile ducts for treating biliary obstructions. Here, we evaluated the utility and safety of PS placement inside bile ducts for treating unresectable malignant hilar biliary obstruction. METHODS: We conducted a retrospective study of 27 patients with unresectable malignant hilar biliary obstruction who underwent intraductal modified PS placement. We modified the PS, by cutting off the distal end to facilitate insertion through the papilla of Vater, and attached a nylon thread to the distal end for removal. We evaluated complications, the time to recurrent biliary obstruction (TRBO), and removability. RESULTS: Bilateral stenting was performed in nine of the 27 patients. Mild acute pancreatitis occurred in one patient (4%). Recurrent biliary obstruction (RBO) occurred in 16 patients (59%), with a median TRBO of 190 days (95% confidence interval: 174-205 days). Reintervention was necessary in 13 of the 16 patients (81%) with RBO, and we were able to remove the initial stents in all the patients who required reintervention. CONCLUSIONS: A relatively long stent patency period (>6 months) and removability make placement of a modified PS inside bile ducts a viable treatment for unresectable malignant hilar biliary obstruction.