Statins' Regulation of the Virulence Factors of Helicobacter pylori and the Production of ROS May Inhibit the Development of Gastric Cancer

Conventionally, statins are used to treat high cholesterol levels. They exhibit pleiotropic effects, such as the prevention of cardiovascular disease and decreased cancer mortality. Gastric cancer (GC) is one of the most common cancers, ranking as the third leading global cause of cancer-related deaths, and is mainly attributed to chronic Helicobacter pylori infection. During their co-evolution with hosts, H. pylori has developed the ability to use the cellular components of the host to evade the immune system and multiply in intracellular niches. Certain H. pylori virulence factors, including cytotoxin-associated gene A (CagA), vacuolating cytotoxin A (VacA), and cholesterol-α-glucosyltransferase (CGT), have been shown to exploit host cholesterol during pathogenesis. Therefore, using statins to antagonize cholesterol synthesis might prove to be an ideal strategy for reducing the occurrence of H. pylori-related GC. This review discusses the current understanding of the interplay of H. pylori virulence factors with cholesterol and reactive oxygen species (ROS) production, which may prove to be novel therapeutic targets for the development of effective treatment strategies against H. pylori-associated GC. We also summarize the findings of several clinical studies on the association between statin therapy and the development of GC, especially in terms of cancer risk and mortality.

Circulating cytokines and gastric cancer risk

PURPOSE

Chronic inflammation has been hypothesized to play a significant role in the aetiology of cancer, including gastric cancer. In the present study, we sought to examine pre-diagnostic systemic cytokine levels in plasma, which can be seen as markers of aggregate inflammation, and risk of distal gastric cancer in a case-control study nested within the prospective Shanghai Men's Health Study.

METHODS

Circulating levels of eight inflammation-related cytokines were measured in the plasma collected at baseline for 180 incident cases of distal gastric cancer and 358 matched controls. Helicobacter pylori sero-positivity was assessed using multiplex serology. Conditional logistic regression was used to calculate odds ratios (ORs) and 95 % confidence intervals (CI).

RESULTS

Individuals with IL-8 levels above the lowest quartile were at twofold increased odds of gastric cancer [OR 1.91 (95 % CI 1.05-3.46), OR 2.10 (95 % CI 1.19-3.74), and OR 2.30 (95 % CI 1.26-4.19), for the second through fourth quartiles, respectively]. While there were suggestions of an increase in risk with increased level of many of the other cytokines measured (IL-1β, IL-2, IL-4, IL-6, IL-10, TNF-α, and IFN-γ), no significant associations were found at the p < 0.05 level. Infection with CagA-positive H. pylori did not modify these associations.

CONCLUSIONS

In a population with high gastric cancer incidence and high H. pylori prevalence, increased circulating levels of IL-8 may indicate increased risk of gastric cancer. These findings add to our understanding of the disease and further efforts to uncover biomarkers of disease risk.

Mesenchymal stem cells utilize CXCR4-SDF-1 signaling for acute, but not chronic, trafficking to gastric mucosal inflammation

BACKGROUND

Helicobacter infection is the main risk factor in developing gastric cancer. Mesenchymal stem cells (MSCs) are non-hematopoietic stromal cells, which are able to differentiate into different cell lineages. MSC contribute to cancer development by forming the tumor directly, contributing to the microenvironment, or by promoting angiogenesis and metastasis. CXCR4/SDF-1 axis is used by MSC in trafficking, homing, and engraftment at chronic inflammation sites, and plays an important role in tumorigenesis.

AIM

To determine if CXCR4 receptor has a role in MSC contribution to the development of Helicobacter-mediated gastric cancer.

METHODS

SDF-1 and CXCR4 expression in mouse gastric mucosa in the setting of acute and chronic inflammation was measured using RT-PCR. Mouse culture-adapted MSC express CXCR4. Wild-type C57BL/6 mice infected with Helicobacter felis for 6 months or controls were given IV injections of CXCR4 knock-down MSC. Animals were followed for another 4 months. Homing of MSC in the stomach was quantified using RT-PCR. MSC differentiation into gastric epithelia lineages was analyzed using immunohistochemistry and fluorescent in situ hybridization.

RESULTS

CXCR4 and SDF-1 are both upregulated in the settings of Helicobacter-induced chronic gastric inflammation. CXCR4 is fully required for homing of MSC to the stomach in acute gastric inflammation, but only partially in Helicobacter-induced gastric cancer. MSC lead to gastric intraepithelial neoplasia as early as 10 months of Helicobacter infection.

CONCLUSIONS

Our results show that MSC have a tumorigenic effect by promoting an accelerated form of gastric cancer in mice. The engraftment of MSC in chronic inflammation is only partially CXCR4-dependent.

Variation in human genetic polymorphisms, their association with Helicobacter pylori acquisition and gastric cancer in a multi-ethnic country

BACKGROUND AND AIM

The contribution of human genetic polymorphisms to Helicobacter pylori infection and gastric cancer (GC) development remains unclear due to geographic variation in the association between specific host genetic polymorphisms and GC. In the current study we investigated the association between polymorphisms related to immune and cancer-related pathways and H. pylori infection among the major ethnicities, Chinese, Malay and Indian, resident in Singapore and Malaysia as well as the association between these polymorphisms and GC development in ethnic Chinese patients.

METHODS

Thirty-four polymorphisms in 26 genes were typed by mass spectrometry in 422 patients undergoing endoscopy (162 Chinese, 113 Indian and 87 Malay controls and 60 Chinese GC cases). Patients were assessed for evidence of H. pylori infection. Odds ratios (OR) and confidence intervals (CI) were obtained using logistic regression models.

RESULT

The prevalence of 16 polymorphisms varied significantly among the ethnicities. In the Chinese subgroup, nominally significant associations were shown between (i) EBBR2+1963G (rs1801200) and H. pylori infection (per-allele OR: 0.48, 95% CI 0.23, 0.98, P = 0.04), (ii) PTGS2-1195G (rs689466) and an increased risk of GC on adjusting for H. pylori status (OR: 1.53, 95% CI 0.99, 2.37, P = 0.05), and (iii) IL1B-1473C (rs1143623) and a decreased risk of GC (OR: 0.64, 95% CI 0.41, 0.99, P = 0.05). Borderline significant associations were seen between IL2-330G (rs2069762) (OR 1.45, 95% CI 0.95, 2.15, P = 0.06) and IL13-1111T (rs1800925) (OR 0.65, 95% CI 0.42, 1.01, P = 0.06) and H. pylori infection.

CONCLUSION

These findings contribute to the understanding of the genetic variation between ethnicities, which may influence H. pylori susceptibility and the outcome of infection.