Diabetes mellitus and the risk of gastric cancer: a meta-analysis of cohort studies

Smoking is one of the well-established risk factors for gastric cancer incidence, yet whether men are more or equally susceptible to gastric cancer due to smoking compared with women is a matter of controversy. The aim of this study was to investigate and compare the effect of sex on gastric cancer risk associated with smoking. We conducted a systemic literature search in MEDLINE, EMBASE, and the Cochrane CENTRAL databases to identify studies published from inception to December 2018. We included prospective observational studies which reported effect estimates with 95% confidence intervals (CIs) for associations of current or former smokers with the incidence of gastric cancer by sex. We calculated the ratio of relative risk (RRR) with corresponding 95% CI based on sex-specific effect estimates for current or former smokers versus non-smokers on the risk of gastric cancer. We included 10 prospective studies with 3,381,345 participants in our analysis. Overall, the summary RRR (male to female) for gastric cancer risk in current smokers was significantly increased compared with non-smokers (RRR: 1.30; 95% CI: 1.05–1.63; P = 0.019). Furthermore, there was no significant sex difference for the association between former smokers and gastric cancer risk (RRR: 1.20; 95% CI: 0.92–1.55; P = 0.178). However, the result of sensitivity analysis indicated the pooled result was not stable, which was altered by excluding a nested case-control study (RRR: 1.31; 95% CI: 1.10–1.57; P = 0.002). This systematic review showed a potential sex difference association between current smokers and the risk of gastric cancer. The sex differential in smokers can give important clues for the etiology of gastric cancers and should be examined in further studies.

The brain is a common site for metastasis in non-small-cell lung cancer (NSCLC). This study was designed to evaluate the relationship between the mutational of the epidermal growth factor receptor (EGFR) and overall survival (OS) in NSCLC patients with brain metastases. Searches were performed in PubMed, EmBase, and the Cochrane Library to identify studies evaluating the association of EGFR mutation with OS in NSCLC patients through September 2017. 4373 NSCLC patients with brain metastases in 18 studies were involved. Mutated EGFR associated with significantly improved OS compared with wild type. Subgroup analyses suggested that this relationship persisted in studies conducted in Eastern, with retrospective design, with sample size ≥500, mean age of patients ≥65.0 years, percentage male < 50.0%, percentage of patients receiving tyrosine kinase inhibitor ≥30.0%. Finally, although significant publication bias was observed using the Egger test, the results were not changed after adjustment using the trim and fill method. This meta-analysis suggests that EGFR mutation is an important predictive factor linked to improved OS for NSCLC patients with brain metastases. It can serve as a useful index in the prognostic assessment of NSCLC patients with brain metastases.

Neoadjuvant chemotherapy (NAC) is extensively used in the treatment of patients with gastric cancer (GC), particularly in high risk, advanced gastric cancer. Previous trials testing the efficacy of NAC have reported inconsistent results. This study compares the combined use of NAC and surgery with surgery alone for GC by using a meta-analytic approach. We performed an electronic search of PubMed, EmBase, and the Cochrane Library to identify randomized controlled trials (RCTs) on NAC published before Oct 2015. The primary outcome of the studies was data on survival rates for patients with GC. The summary results were pooled using the random-effects model. We included 12 prospective RCTs reporting data on 1538 GC patients. Patients who received NAC were associated with significant improvement of OS (P = 0.001) and PFS (P < 0.001). Furthermore, NAC therapy significantly increased the incidence of 1-year survival rate (SR) (P = 0.020), 3-year SR (P = 0.011), and 4-year SR (P = 0.001). Similarly, NAC therapy was associated with a lower incidence of 1-year (P < 0.001), 2-year (P < 0.001), 3-year (P < 0.001), 4-year (P = 0.001), and 5-year recurrence rate (P = 0.002). Conversely, patients who received NAC also experienced a significantly increased risk of lymphocytopenia (P = 0.003), and hemoglobinopathy (P = 0.021). The findings of this study suggested that NAC is associated with significant improvement in the outcomes of survival and disease progression for GC patients while also increasing some toxicity.

Peritoneal dissemination is the most common cause of death in gastric cancer patients. The hypoxic microenvironment plays a major role in controlling the tumor stem cell phenotype and is associated with patients' prognosis through hypoxia-inducible factor-1α (HIF-1α), a key transcriptional factor that responds to hypoxic stimuli. During the peritoneal dissemination process, gastric cancer stem/progenitor cells (GCSPCs) are thought to enter into and maintained in peritoneal milky spots (PMSs), which have hypoxic microenvironments. However, the mechanism through which the hypoxic environment of PMSs regulated GCSPC maintenance is still poorly understood. Here, we investigated whether hypoxic PMSs were an ideal cancer stem cell niche suitable for GCSPC engraftment. We also evaluated the mechanisms through which the HIF-1α-mediated hypoxic microenvironment regulated GCSPC fate. We observed a positive correlation between HIF-1α expression and gastric cancer peritoneal dissemination (GCPD) in gastric cancer patients. Furthermore, the GCSPC population expanded in primary gastric cancer cells under hypoxic condition in vitro, and hypoxic GCSPCs showed enhanced self-renewal ability, but reduced differentiation capacity, mediated by HIF-1α. In an animal model, GCSPCs preferentially resided in the hypoxic zone of PMSs; moreover, when the hypoxic microenvironment in PMSs was destroyed, GCPD was significantly alleviated. In conclusion, our results demonstrated that PMSs served as a hypoxic niche and favored GCSPCs peritoneal dissemination through HIF-1α both in vitro and in vivo. These results provided new insights into the GCPD process and may lead to advancements in the clinical treatment of gastric cancer. Stem Cells 2014;32:3062–3074