Yoshito Uenoyama

STAT3 is constitutively activated and supports cell survival in association with survivin expression in gastric cancer cells

Signal transduction and activator of transcription 3(STAT3) signaling is constitutively activated in various tumors, and is involved in cell survival and proliferation during oncogenesis. There are few reports, however, on the role of STAT3 signaling in gastric cancer. The aim of the present study was to clarify the role of STAT3 signaling in apoptosis and cellular proliferation in gastric cancer. Here we reported that STAT3 was constitutively activated in various human gastric cancer cells and its inhibition by ectopic dominant-negative STAT3 or Janus kinase inhibitor, tyrphostin AG490, induced apoptosis. Furthermore, STAT3 inhibition markedly decreased survivin expression, and forced expression of survivin rescued AGS cells from apoptosis induced by STAT3 inhibition. Although some reports demonstrated that the PI3K/Akt pathway regulates survivin expression, inhibition of the PI3K/Akt pathway did not affect survivin expression in AGS and MKN1 cells. Finally, activated form of STAT3, Tyr-705 phospho-stat3, was found in the nucleus of cancer cells in 11 of 40 (27.5%) human gastric cancer specimens. These findings suggest that constitutively activated STAT3 signaling supports gastric cancer cell survival in association with survivin expression.

Growth arrest‐specific gene 6 and Axl signaling enhances gastric cancer cell survival via Akt pathway

Activation of tyrosine kinases is an important factor during cancer development. Axl, one of the receptor tyrosine kinases, binds to the specific ligand growth arrest‐specific gene 6 (Gas6), which encodes a vitamin K‐dependent γ‐carboxyglutamyl protein. Although many receptor tyrosine kinases and their ligands are involved in gastric carcinogenesis, whether Gas6‐Axl signaling is involved in gastric carcinogenesis has not been elucidated. The aim of this study was to investigate the expression of Gas6 and Axl in gastric cancer and also their roles during gastric carcinogenesis. mRNA and protein of Gas6 and Axl were highly expressed in a substantial proportion of human gastric cancer tissue and cell lines, and Gas6 expression was significantly associated with lymph node metastasis. With recombinant Gas6 and a decoy‐receptor of Axl in vitro, we demonstrated that Gas6‐Axl signaling pathway enhanced cellular survival and invasion and suppressed apoptosis via Akt pathway. Our results suggests that Gas6‐Axl signaling plays a role during gastric carcinogenesis, and that targeting Gas6‐Axl signaling could be a novel therapeutic for gastric cancer.

Possible role of REG Iα protein in ulcerative colitis and colitic cancer

Background and aims: Although regenerating gene (REG) Iα protein may be involved in the inflammation and carcinogenesis in the gastrointestinal tract, its pathophysiological role in ulcerative colitis (UC) and the resulting colitic cancer remains unclear. We investigated expression of the REG Iα gene and its protein in UC and colitic cancer tissues. We examined whether cytokines are responsible for REG Iα gene expression and whether REG Iα protein has a trophic and/or an antiapoptotic effect on colon cancer cells. Methods: Expression of REG Iα mRNA and its gene product in UC tissues was analysed by real time reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. The effects of cytokines on REG Iα promoter activity were examined in LoVo cells by luciferase reporter assay. The effects of REG Iα protein on growth and H2O2 induced apoptosis were examined in LoVo cells by MTT and TUNEL assays, respectively. Results: REG Iα protein was strongly expressed in inflamed epithelium and in dysplasias and cancerous lesions in UC tissues. The level of REG Iα mRNA expression in UC tissues correlated significantly with severity of inflammation and disease duration. REG Iα promoter activity was enhanced by stimulation with interferon γ or interleukin 6. REG Iα protein promoted cell growth and conferred resistance to H2O2 induced apoptosis in LoVo cells. REG Iα protein promoted Akt phosphorylation and enhanced Bcl-xL and Bcl-2 expression in LoVo cells. Conclusions: The REG Iα gene is inducible by cytokines and its gene product may function as a mitogenic and/or an antiapoptotic factor in the UC-colitic cancer sequence.

Signal transducers and activators of transcription 3 activation is involved in nuclear accumulation of β-catenin in colorectal cancer

Nuclear accumulation of beta-catenin is a key event for the development of colorectal cancer. Little is known, however, about the mechanisms underlying translocation of beta-catenin from the cytoplasm or the membrane to the nucleus. The present study examined whether signal transducers and activators of transcription 3 (STAT3) activation is involved in the nuclear accumulation of beta-catenin in colorectal cancer cells. Of the 90 primary colorectal cancer tissues, 40 (44.4%) were positive for nuclear staining of p-STAT3 and 63 (70.0%) were positive for nuclear staining of beta-catenin. The nuclear staining of both p-STAT3 and beta-catenin were observed predominantly in the periphery of the cancer tissues. Importantly, of the 40 tumors with p-STAT3 nuclear staining, 37 (92.5%) were also positive for nuclear beta-catenin staining and there was a significant correlation between p-STAT3 and beta-catenin nuclear staining (P < 0.01). Coexpression of nuclear p-STAT3 and beta-catenin was associated with lower patient survival (P < 0.01). In an in vitro study using a human colon cancer cell line, SW480, inhibition of STAT3 by dominant negative STAT3 or the Janus kinase inhibitor, AG490, induced translocation of beta-catenin from the nucleus to the cytoplasm or membrane. Luciferase assays revealed that STAT3 inhibition resulted in significant suppression of beta-catenin/T-cell factor transcription in association with significant inhibition of cell proliferation (P < 0.05). These findings suggest that in colorectal cancer, STAT3 activation is involved in the nuclear accumulation of beta-catenin, resulting in poor patient survival.

Hypoxia induced by benign intestinal epithelial cells is associated with cyclooxygenase-2 expression in stromal cells through AP-1-dependent pathway

Cyclooxygenase-2 (COX-2) plays important roles in tumor development. Especially in the early-stage colorectal tumors, COX-2 expression is often observed in the tumor stroma. However, the mechanism regulating such stromal expression of COX-2 remains unknown. In the present study, we simulated the indirect interaction between epithelial cells and stromal cells in the process of colorectal tumor development using an in vitro co-culture model in which NIH3T3 fibroblasts were co-cultured with ‘sparsely’ or ‘densely’ populated intestinal epithelial cells, Intestine-407 as a model of premalignant or benign intestinal epithelial cells, and DLD-1 and Caco-2 as models of malignant epithelial cells. COX-2 expression in NIH3T3 fibroblasts was upregulated when co-cultured with the ‘dense’ epithelial cells regardless of their character. Interestingly, there was pericellular hypoxia in the vicinity of NIH3T3 fibroblasts when co-cultured with ‘dense’ epithelial cells, and the recovery of the partial pressure of oxygen level resulted in the reduction of enhanced COX-2 expression only in NIH3T3 fibroblasts co-cultured with ‘dense’ Intestine-407 cells. Furthermore, COX-2 expression was also reduced by the inhibition of transcription factor AP-1. Thus, pericellular hypoxia of the stromal cells caused by densely populated epithelial cells may be one of the potent COX-2 enhancers before completion of malignant transformation during intestinal tumor development.

Pulmonary embolism after arterial chemoembolization for hepatocellular carcinoma: an autopsy case report.

We report an extremely rare case of pulmonary lipiodol embolism with acute respiratory distress syndrome (ARDS) after transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC). A 77-year-old man who was diagnosed with a huge HCC was admitted for TACE. Immediately after the procedure, this patient experienced severe dyspnea. We suspected that his symptoms were associated with a pulmonary lipiodol embolism after TACE, and we began intensive treatment. However, his condition did not improve, and he died on the following day. A subsequent autopsy revealed that the cause of death was ARDS due to pulmonary lipiodol embolism. No cases have been previously reported for which an autopsy was performed to explain the most probable mechanism of pulmonary lipiodol embolism; thus, ours is the first report for such a rare case.

Ileus caused by cholesterol crystal embolization: A case report

Cholesterol crystal embolization (CCE) is a rare systemic embolism caused by formation of cholesterol crystals from atherosclerotic plaques. CCE usually occurs during vascular manipulation, such as vascular surgery or endovascular catheter manipulation, or due to anticoagulation or thrombolytic therapy. We report a rare case of intestinal obstruction caused by spontaneous CCE. An 81-year-old man with a history of hypertension was admitted for complaints of abdominal pain, bloating, and anorexia persisting for 4 mo. An abdominal computed tomography revealed intestinal ileus. His symptoms were immediately relieved by an ileus tube insertion, and he was discharged 6 d later. However, these symptoms immediately reappeared and persisted, and partial resection of the small intestine was performed. A histopathological examination indicated that small intestine obstruction was caused by CCE. At the 12-mo follow-up, the patient showed no evidence of CCE recurrence. Thus, in cases of intestinal obstruction, CCE should also be considered.

A Foreign Body in the Appendix

A 77-year-old man was referred to our hospital following ingestion of a dental drill bit. He was asymptomatic and had no abnormal findings on physical assessment or blood tests. We performed esophagogastroduodenoscopy but could not locate the drill bit. The next day, an abdominal radiograph showed the drill bit in the right lower abdominal quadrant. Two days later, we performed colonoscopy because the drill bit had not moved on the radiograph. However, we could not locate the drill bit. Subsequent CT examination revealed the drill bit within the appendix (Figure 1). Colonoscopy under fluoroscopic guidance showed the drill bit in the appendix, which was crookedly oriented (Figure 2). We unsuccessfully attempted to straighten the appendix with an endoscopic retrograde cholangiopancreatography catheter and endoscopically remove the drill bit. Although the patient was asymptomatic, laparoscopic appendectomy was performed. Pathological examination showed a 35-mm drill bit within the appendix (Figure 3), and histological examination showed only mild inflammation. The patient was discharged with no postoperative complications.