Helicobacter pylori and hepatocellular carcinoma: correlated or uncorrelated?

Helicobacter pylori Outer Membrane Proteins and Virulence Factors: Potential Targets for Novel Therapies and Vaccines

Helicobacter pylori is a gastric oncopathogen that infects over half of the world's human population. It is a Gram-negative, microaerophilic, helix-shaped bacterium that is equipped with flagella, which provide high motility. Colonization of the stomach is asymptomatic in up to 90% of people but is a recognized risk factor for developing various gastric disorders such as gastric ulcers, gastric cancer and gastritis. Invasion of the human stomach occurs via numerous virulence factors such as CagA and VacA. Similarly, outer membrane proteins (OMPs) play an important role in H. pylori pathogenicity as a means to adapt to the epithelial environment and thereby facilitate infection. While some OMPs are porins, others are adhesins. The epithelial cell receptors SabA, BabA, AlpA, OipA, HopQ and HopZ have been extensively researched to evaluate their epidemiology, structure, role and genes. Moreover, numerous studies have been performed to seek to understand the complex relationship between these factors and gastric diseases. Associations exist between different H. pylori virulence factors, the co-expression of which appears to boost the pathogenicity of the bacterium. Improved knowledge of OMPs is a major step towards combatting this global disease. Here, we provide a current overview of different H. pylori OMPs and discuss their pathogenicity, epidemiology and correlation with various gastric diseases.

Decreased risk of liver and intrahepatic cancer in non-H. pylori-infected perforated peptic ulcer patients with truncal vagotomy: a nationwide study

The vagal nervous system is central to the physiological responses and systemic diseases of the liver. We evaluated the subsequent risk of liver and intrahepatic cancer (HCC/ICC) in non-H. pylori (HP)-infected perforated peptic ulcer (PPU) patients with and without vagotomy. Hospitalized PPU patients who underwent simple closure or truncal vagotomy/pyloroplasty (TVP) in the National Health Insurance Research Database from 2000 to 2008 were enrolled. The exclusion criteria included: (1) Multiple surgeries for PPU were received at the same admission; (2) Any cancer history; (3) Previous peptic ulcer-associated surgery; (4) HP infection history; (5) Viral hepatitis infection history; (6) Follow-up duration < 1 year; and (7) Age < 18 years. The risks of developing HCC/ICC in PPU patients with and without vagotomy were assessed at the end of 2013. To balance the baseline condition between groups, we used the propensity score matched method to select study subjects. Cox proportional hazard regression was used to estimate the hazard ratio and 95% confidence interval (CI) of HCC/ICC. Before propensity score matching, 675 simple suture patients and 54 TVP patients had HCC/ICC, which corresponded to incidences of 2.11 and 0.88 per 1000 person-years, respectively. After propensity score matching, 145 simple suture patients and 54 TVP patients experienced HCC/ICC, which corresponded to incidences of 1.45 and 0.88 per 1000 person-years, respectively. The TVP patients had a 0.71 (95% CI 0.54-0.95)- and 0.69 (95% CI 0.49-0.97)-fold risk of developing HCC/ICC compared to simple suture patients before and after propensity score matching. Our findings reported that, in the Asian population, TVP decreases the risk of HCC/ICC in non-HP-infected PPU patients compared to simple closure patients. However, further studies are warranted.

Association Between Acid-Suppressive Agents’ Use and Risk of Hepatocellular Carcinoma

Background:

Acid-suppressive agents (ASAs), which are mostly used in patients with upper gastrointestinal diseases (UGIDs), may influence the risk of hepatocellular carcinoma (HCC).

Methods:

A population-based retrospective cohort study was conducted. Patients with UGID who used ASAs and those who did not receive ASAs were identified. Patients without UGIDs were randomly selected and matched (comparison group). All groups were followed up for 6 years. A Cox proportional hazard model was used to estimate the risk of HCC among the different groups.

Results:

Patients with UGID who used ASAs had a significantly elevated HCC risk (adjusted hazard ratio [HR] 1.53; 95% confidence interval [CI], 1.32-1.76] compared to those who did not use ASAs. Patients with UGID who used more than 540 defined daily doses of ASAs had a significantly higher risk of HCC (adjusted HR 2.04; 95% CI, 1.62-2.58). Moreover, the dose effect on HCC risk exhibited a significant increasing trend ( P < .01). Furthermore, patients with UGID who did not use ASAs had a significantly elevated HCC risk (adjusted HR 1.94; 95% CI, 1.59-2.36) compared to the comparison group.

Conclusion:

The use of ASAs increased the risk of HCC in patients with UGIDs, and the effect of ASAs was dose dependent. In addition, UGIDs alone increased the risk of HCC.

The Association between Helicobacter pylori Infection and Chronic Hepatitis C: A Meta-Analysis and Trial Sequential Analysis

Purpose. Helicobacter pylori is a common gastric disease-inducing pathogen. Although an increasing number of recent studies have shown that H. pylori is a risk factor for liver disease, the potential association between H. pylori infection and chronic hepatitis C still remains controversial. The aim of our meta-analysis was to evaluate a potential association between H. pylori infection and chronic hepatitis C. Methods. We searched the PubMed, Embase, CNKI, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) databases between January 1, 1994, and May 1, 2015. Results. This study included a total of 1449 patients with chronic hepatitis C and 2377 control cases. The prevalence of H. pylori was significantly higher in patients with chronic hepatitis C than in those without chronic hepatitis C. The pooled odds ratio was 2.93. In a subgroup analysis, the odds ratios were 4.48 for hepatitis C virus- (HCV-) related cirrhosis and 5.45 for hepatocellular carcinoma. Conclusion. Our study found a strong association between H. pylori and chronic hepatitis C, particularly during the HCV progression stage; thus, we recommend active screening for H. pylori in patients with chronic hepatitis C.

Bone marrow-derived mesenchymal stem cell therapy for decompensated liver cirrhosis: A meta-analysis

AIM: To assess the efficacy and safety of bone marrow-derived mesenchymal stem cell (BM-MSC) in the treatment of decompensated liver cirrhosis.

METHODS: The search terms “bone marrow stem cell”“chronic liver disease”“transfusion” and “injection” were used in the Cochrane Library, Med-Line (Pub-Med) and Embase without any limitations with respect to publication date or language. Journals were also hand-searched and experts in the field were contacted. The studies which used BM-MSC in the treatment of any chronic liver disease were included. Comprehensive Review Manager and Meta-Analyst software were used for statistical analysis. Publication bias was evaluated using Begg’s test.

RESULTS: Out of 78 studies identified, five studies were included in the final analysis. The studies were conducted in China, Iran, Egypt and Brazil. Analysis of pooled data of two controlled studies by Review Manager showed that the mean decline in scores for the model for end-stage liver disease (MELD) was -1.23 [95%CI: -2.45-(-0.01)], -1.87 [95%CI: -3.16-(-0.58)], -2.01 [95%CI: -3.35-(-0.68)] at 2, 4 and 24 wk, respectively after transfusion. Meta-analysis of the 5 studies showed that the mean improvement in albumin levels was -0.28, 2.60, 5.28, 4.39 g/L at the end of 8, 16, 24, and 48 wk, respectively, after transfusion. MELD scores, alanine aminotransferase, total bilirubin levels and prothrombin times improved to some extent. BM-MSC injections resulted in no serious adverse events or complications.

CONCLUSION: BM-MSC infusion in the treatment of decompensated liver cirrhosis improved liver function. At the end of year 1, there were no serious side effects or complications.

Association between the presence of H pylori in the liver and hepatocellular carcinoma: a meta-analysis

AIM

To evaluate the arguments for and against the possible roles of H pylori in hepatocellular carcinoma (HCC).

METHODS

We performed a systematic review of all relevant studies published in the literature. A total of 103 clinical trials and reports were identified, but only 10 trials qualified under our selection criteria. A meta-analysis was carried out by a biostatistician according to the Cochrane Reviewers' Handbook recommended by The Cochrane Collaboration.

RESULTS

Nine case-control studies and one retrospective cross sectional study were included in the final analysis. Overall the prevalence of H pylori infection was 53.3% (129 of 242) in cases and 10.4% (29 of 280) in controls, and the summary odds ratio for the association of H pylori infection with the risk for HCC (using the fixed-effects model, which accounted for the homogeneity across the 10 studies) was determined to be 13.63 (95% CI, 7.90-23.49).

CONCLUSION

Our analysis showed a positive association between H pylori infection and the risk of HCC, with an indication of possible publication bias and possible confounders due to study designs that showed results of less pronounced associations.

Association between the presence of H pylori in the liver and hepatocellular carcinoma: a meta-analysis

AIM

To evaluate the arguments for and against the possible roles of H pylori in hepatocellular carcinoma (HCC).

METHODS

We performed a systematic review of all relevant studies published in the literature. A total of 103 clinical trials and reports were identified, but only 10 trials qualified under our selection criteria. A meta-analysis was carried out by a biostatistician according to the Cochrane Reviewers' Handbook recommended by The Cochrane Collaboration.

RESULTS

Nine case-control studies and one retrospective cross sectional study were included in the final analysis. Overall the prevalence of H pylori infection was 53.3% (129 of 242) in cases and 10.4% (29 of 280) in controls, and the summary odds ratio for the association of H pylori infection with the risk for HCC (using the fixed-effects model, which accounted for the homogeneity across the 10 studies) was determined to be 13.63 (95% CI, 7.90-23.49).

CONCLUSION

Our analysis showed a positive association between H pylori infection and the risk of HCC, with an indication of possible publication bias and possible confounders due to study designs that showed results of less pronounced associations.

Identification of Helicobacter species by 16S rDNA PCR and sequence analysis in human liver samples from patients with various etiologies of benign liver diseases

BACKGROUND/AIMS

Several reports indicated an increased prevalence of the Helicobacter species in hepatocellular cancer tissue and in liver samples infected with hepatitis viruses. The frequency of Helicobacter spp. in benign liver diseases was, however, not thoroughly investigated.

METHODS

Seventy-five consecutive patients with suspected liver disease were enrolled. The indications were hepatitis B virus (n=30), C virus (n=8), B and C dual infection (n=1), nonalcoholic steatohepatitis (n=27), autoimmune hepatitis (n=3), primary biliary cirrhosis (n=1) and idiopathic elevation of liver enzymes (n=5). PCR detection of 16S recombinant RNA gene of Helicobacter spp. was performed on liver samples. PCR products of positive samples were further identified by DNA sequencing. The patients also had upper gastrointestinal endoscopy and gastric biopsy for the detection of H. pylori using histopathology and PCR.

RESULTS

Helicobacter spp. DNA was detected in two out of 75 liver biopsy samples (2.6%), which were typed as H. pylori by DNA sequencing. One of these patients had chronic hepatitis C infection (man, 51 years old) and the other had nonalcoholic steatohepatitis (woman, 44 years old). Fifty-two out of 75 of the patients (69.3%) had H. pylori infection in their stomachs.

CONCLUSION

We have found that H. pylori infection is much less prevalent in benign liver diseases. The presence of H. pylori in nonalcoholic steatohepatitis (NASH) patients is a novel finding and this finding should be confirmed in a larger series.

Low frequency of Helicobacter DNA in benign and malignant liver tissues from Baltimore, United States

Helicobacter DNA has been reported in hepatocellular carcinoma tissues in several studies from varying geographic locations, raising the possibility that Helicobacter infection may contribute to the pathogenesis of hepatocellular carcinoma. Other known risk factors for hepatocellular carcinoma show significant geographic variability, but whether the same holds for Helicobacter is unknown. We studied the prevalence of Helicobacter DNA in a US cohort of hepatocellular carcinoma, where the prevalence of Helicobacter infection is low in the general population. Liver tissues from 57 individuals were examined. Thirty-five individuals had paired tumor/nontumor samples, including 21 cases of hepatocellular carcinoma, for a total of 92 samples studied. Both Helicobacter genus and Helicobacter pylori species-specific polymerase chain reaction was performed. Helicobacter DNA was detected in 5 (9%) of 57 cases, all in nonneoplastic cirrhotic liver tissues from individuals with hepatitis C infection (n = 4) or alcohol liver disease (n = 1). Tissues from 22 hepatocellular carcinomas and 10 cholangiocarcinomas were all negative as were tissues from 8 benign primary hepatic tumors. In conclusion, Helicobacter DNA was detectable in 9% of liver tissues in this cohort but was not found in primary benign or malignant liver tumors. These findings indicate that Helicobacter infection is unlikely to be etiologically associated with hepatocellular carcinoma in this cohort. If Helicobacter infection does contribute to the development of hepatocellular carcinoma in general, then significant regional variability must exist.

Bone marrow cells: the source of hepatocellular carcinoma?

Whether the stem cells or the mature cells are the origination of hepatocellular carcinoma is uncertain. Recently, researches have shown that some cancer stem cells could derive from adult stem cells. Moreover, gastric cancer could originate from bone marrow stem cells. Hematopoiesis and the hepatic environment are known to have a close relationship at the time of hepatic development and systemic diseases. Here we propose a new carcinogenetic model of hepatocellular carcinoma. Chronic liver injury could recruit bone marrow stem cells to the liver. Bone marrow cells take part in liver regeneration by differentiating to oval cells and hepatocytes. Persistent regeneration results in hyperproliferation, an increased rate of transforming mutations. Extracellular matrix remodeling triggers a cascade of events that inhibits the transactivation potential of liver-specific transcription factors, blocks the maturation of stem cells, and then results in hepatocellular carcinoma.

Helicobacter and digestive malignancies

Important new data were published during the past year on the relationship of Helicobacter infection and gastric neoplasias. In the pathogenesis of gastric cancer, a thrilling new hypothesis was put forward based on animal experiments. Helicobacter infection induces gastric mucosal damage and bone marrow-derived cells (mobilized into peripheral blood and attracted to the inflamed mucosa) replace the areas of damaged gastric tissue and turn into neoplastic proliferation. Several studies focused on mechanisms related to the development of gastric malignancy in infected individuals with particular attention to inflammatory cytokine gene polymorphisms. Some new evidence is also reported to suggest that Helicobacter infection increases the risk of neoplasias outside the stomach in the liver and colon.

Origin of hepatocellular carcinoma: role of stem cells

The question of whether hepatocellular carcinoma (HCC) arises from the differentiation block of stem cells or dedifferentiation of mature cells remains controversial. Recently, researchers suggested that HCC may originate from the transdifferentiation of bone marrow cells. Interestingly, there are four levels of cells in the hepatic stem cell lineage: bone marrow cells, hepato-pancreas stem cells, oval cells and hepatocytes. Hematopoietic stem cells and the liver are known to have a close relationship in early development. Bone marrow stem cells could differentiate into oval cells, which could differentiate into hepatocytes and duct cells. The development of pancreatic and liver buds in embryogenesis suggests the existence of a common progenitor cell to both the pancreas and liver. Cellular events during hepatocarcinogenesis illustrate that HCC may arise from cells at various stages of differentiation in the hepatic stem cell lineage.