Characteristics of gastric cancer in Asia

Obesity and related risk factors in gastric cardia adenocarcinoma

Over recent decades, the incidence of cancers of the gastroesophageal junction, including gastric cardia tumors, has increased markedly. This is a trend that has been well documented, especially in studies from the USA and northern Europe that have also demonstrated a concomitant rise in the ratio of cardia to distal gastric cancers. The rise in the prevalence of gastric cardia adenocarcinoma has been paralleled by the worldwide obesity epidemic, with almost all epidemiological studies reporting increased body mass index and obesity increase the risk of cardia cancer development. However, the strength of this association is less marked than the link between obesity and esophageal adenocarcinoma, and the mechanisms remain poorly understood. Other possible confounders of the relationship between obesity and cardia cancer include the decline in Helicobacter pylori infection and the widespread use of proton pump inhibitors, although these have rarely been controlled for in case-control and cohort studies investigating associations between obesity and cardia cancer. We review these epidemiological trends and discuss proposed mechanisms for the association, drawing attention to controversies over the difficulty of defining cardia cancer. The relative paucity of high-quality epidemiological studies from other regions of the world should prompt further investigation of this issue, especially in populations undergoing rapid socioeconomic change.

Training in early gastric cancer diagnosis improves the detection rate of early gastric cancer: an observational study in China

Few studies have analyzed the training of endoscopists in the diagnosis of early gastric cancer (EGC). This study assessed whether specific training of endoscopists improves the detection rate of EGC. The rates of detection of EGC by endoscopists at the Digestive Endoscopy Center of the Affiliated Nanfang Hospital of China Southern Medical University between January 2013 and May 2014 were retrospectively analyzed. Because some endoscopists received training in the diagnosis of EGC, beginning in September 2013, the study was divided into 3 time periods: January to September 2013 (period 1), September 2013 to January 2014 (period 2), and January to May 2014 (period 3). The rates of EGC detection during these 3 periods were analyzed. From January 2013 to May 2014, a total of 25,314 gastroscopy examinations were performed at our center, with 48 of these examinations (0.2%) detecting EGCs, accounting for 12.1% (48/396) of the total number of gastric cancers detected. The EGC detection rates by trained endoscopists during periods 1, 2, and 3 were 0.3%, 0.6%, and 1.5%, respectively, accounting for 22.0%, 39.0%, and 60.0%, respectively, of the gastric cancers detected during these time periods. In comparison, the EGC detection rates by untrained endoscopists during periods 1, 2, and 3 were 0.05%, 0.08%, and 0.10%, respectively, accounting for 3.1%, 6.0%, and 5.7%, respectively, of the gastric cancers detected during these times. After training, the detection rate by some trained endoscopists markedly increased from 0.2% during period 1 to 2.3% during period 3. Further, the use of magnifying endoscopy with narrow-band imaging (M-NBI) (odds ratio = 3.1, 95% confidence interval 2.4-4.1, P < 0.001) contributed to the diagnosis of EGC. In conclusion, specific training could improve the endoscopic detection rate of EGC. M-NBI contributed to the diagnosis of EGC.

Arsenic sulfide, the main component of realgar, a traditional Chinese medicine, induces apoptosis of gastric cancer cells in vitro and in vivo

Background

Arsenic sulfide (As₄S₄), the main component of realgar, a traditional Chinese medicine, has shown antitumor efficacy in several tumor types, especially for acute promyelocytic leukemia. In this study, we aimed to explore the efficacy and mechanism of As₄S₄ in gastric cancer.

Methods

The effect of As₄S₄ on cell proliferation and apoptosis of gastric cancer cells was investigated by MTT assay, 4′,6-diamidino-2-phenylindole (DAPI) staining, and annexin V–fluorescein isothiocyanate/propidium iodide staining using gastric cancer cell lines AGS (harboring wild-type p53) and MGC803 (harboring mutant p53) in vitro. The expression of apoptosis-related proteins was measured by Western blotting, real-time polymerase chain reaction, and immunohistochemistry analysis. Mouse xenograft models were established by inoculation with MGC803 cells, and the morphology and the proportion of apoptotic cells in tumor tissues were detected by hematoxylin and eosin staining and TdT-mediated dUTP nick end labeling (TUNEL) assay, respectively.

Results

As₄S₄ inhibited the proliferation and induced apoptosis of AGS and MGC803 cells in a time- and dose-dependent manner. As₄S₄ upregulated the expression of Bax and MDM2 while downregulated the expression of Bcl-2. The expression of p53 increased significantly in the AGS cells but did not readily increase in the MGC803 cells, which harbored mutant p53. Pifithrin-α, a p53 inhibitor, blocked the modulation of As₄S₄ on AGS cells, but not on MGC803 cells. Using xenograft as a model, we showed that As₄S₄ suppressed tumor growth and induced apoptosis in vivo and that the expression of p53 increased accordingly.

Conclusion

As₄S₄ is a potent cytotoxic agent for gastric cancer cells, as it induced apoptosis both in vitro and in vivo through a p53-dependent pathway. Our data indicate that As₄S₄ may have therapeutic potential in gastric cancer.

Prognostic value of LAMP3 and TP53 overexpression in benign and malignant gastrointestinal tissues

Lysosomal associated membrane protein 3 (LAMP3) is a newly identified tumor-specific protein. It is a downstream target gene of tumor suppressor TP53 and its expression has been associated with hypoxia-induced metastasis and poor overall survival in cervical and breast cancers. However, little is known of LAMP3 protein expression in gastrointestinal cancer and its prognostic value. We determined protein expression of LAMP3 and TP53 in both gastric (n=750) and colorectal (n=479) tissues by immunohistochemistry analysis on tissue microarray (TMA), their expression was correlated with patients' clinical parameters. LAMP3 and TP53 protein expression was significantly higher in cancerous tissues compared to normal and benign tissues. In both gastric and colorectal cancers, high LAMP3 protein expression (LAMP3+) was significantly associated with tumor stage (P=0.014 and P<0.001). No correlation between LAMP3 and TP53 expression was observed. Patients with high LAMP3 expression but not high TP53 expression had a poor overall survival (for gastric cancer P<0.001, CI: 1.762-4.567; for colorectal cancer P=0.036, CI: 1.062-5.980). Our data suggest that epithelial LAMP3 expression is an independent prognostic marker for gastrointestinal cancer.