Identification of helicobacter species in human liver samples from patients with primary hepatocellular carcinoma

Geographical conservation of short inserts in the signal and middle regions of the Helicobacter pylori vacuolating cytotoxin gene

Short nucleotide sequence inserts within the signal (s) and mid (m) regions of the vacuolating cytotoxin gene (vacA) of Helicobacter pylori provide the basis for defining the allelic forms widely used for strain typing and as markers for toxin functionality and severity of interactions with host gastric epithelial cells. Here 484 signal region and 411 mid-region sequences (new and from public databases) from 32 countries were analysed to determine the effect of geographical location on insert diversity, which is currently undefined. Short (27 bp) inserts of 52 mol% G+C from 201 sequences (98 %) of the s2 allelic family encoded a highly conserved nine amino acid sequence irrespective of geographical origin. The longer (75 bp) mid-region insert of 38 mol% G+C in 255 sequences of the m2 allelic family was more diverse and represented by 23 peptide variants, with one predominant sequence (MRI type 4) representing 62 % of inserts. Mid-region inserts were widespread throughout European/North American (Western) sequences in the dataset whereas a lower insert frequency was a geographical feature of East Asian sequences. Each insert was preceded by an associated conserved motif that provided a marker of the insertion sites within vacA, and facilitated identification of the Chinese m2b genotype. It is concluded that the observed sequence conservation supports the continued global use of vacA genotyping, and that inserts could have a functional significance in the mature protein, particularly the s2 form of the toxin, as the same combination of signal and mid-region insert type and preinsert motif was highly conserved.

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.

Relationship between the severity of hepatitis C virus-related liver disease and the presence of Helicobacter species in the liver: A prospective study

AIM: To determine the presence of Helicobacter species DNA in the liver of chronic hepatitis C (CHC) patients with and without cirrhosis as compared to controls, and to identify the bacterial species involved.

METHODS: Seventy-nine consecutive patients (HBV and HIV negative) with a liver sample obtained after liver biopsy or hepatic resection were studied: 41 with CHC without cirrhosis, 12 with CHC and cirrhosis, and 26 controls (HCV negative). Polymerase chain reactions (PCRs) targeting Helicobacter 16S rDNA and species-specific were performed on DNA extracted from the liver. A gastric infection with H pylori was determined by serology and confirmed by ¹³C-urea breath test.

RESULTS: Overall, Helicobacter 16S rDNA was found in 16 patients (20.2%). Although positive cases tended to be higher in CHC patients with cirrhosis (41.6%) than in those without cirrhosis (17.0%) or in controls (15.4%), the difference was not statistically significant (P = 0.08). H pylori-like DNA was identified in 12 cases and H. pullorum DNA in 2, while 2 cases remained unidenti-fied. Gastric infection with H pylori was found in only 2 of these patients.

CONCLUSION: Our results do not confirm the associ-ation of Helicobacter species DNA in the liver of CHC patients with advanced liver disease. The lack of correlation between positive H pylori serology and the presence of H pylori-like DNA in the liver may indicate the presence of a variant of this species.

Detection ofHelicobacter pyloriDNA in peripheral blood from patients with peptic ulcer or gastritis

Cases of Helicobacter bacteremia have been reported from time to time. Helicobacter pylori is the most important representative of Helicobacterium, yet whether it can result in bacteremia has rarely been studied. In this study, we examined H. pylori DNA in peripheral blood and gastric mucosa of patients with peptic ulcer or chronic gastritis by polymerase chain reaction (PCR). We found H. pylori DNA in 15 of 20 gastric samples, and 9 of these specimens were positive for H. pylori culture. H. pylori DNA amplified by PCR was positive in the peripheral blood of three patients, who all had duodenal ulcers. Gastric biopsy specimens from these three patients were all positive for H. pylori genes and H. pylori was isolated from these specimens. After the 16S rRNA gene sequences of three specimens from the same patient were obtained, we found that they were identical, which suggested that they are the same strain. Our findings suggest that H. pylori exists not only in gastric mucosa but also in peripheral blood, and it is possible that H. pylori can result in bacteremia.

In vitro and in vivo characterization of alkyl hydroperoxide reductase mutant strains of Helicobacter hepaticus

Mutant strains in the tsaA gene encoding alkyl hydroperoxide reductase were more sensitive to O(2) and to oxidizing agents (paraquat, cumene hydroperoxide and t-butylhydroperoxide) than the wild type, but were markedly more resistant to hydrogen peroxide. The mutant strains resistance phenotype could be attributed to a 4-fold and 3-fold increase in the catalase protein amount and activity, respectively compared to the parent strain. The wild type did not show an increase in catalase expression in response to sequential increases in O(2) exposure or to oxidative stress reagents, so an adaptive compensatory mutation has probably occurred in the mutants. In support of this, chromosomal complementation of tsaA mutants restored alkyl hydroperoxide reductase, but catalase was still up-expressed in all complemented strains. The katA promoter sequence was the same in all mutant strains and the wild type. Like its Helicobacter pylori counterpart strain, a H. hepaticus tsaA mutant contained more lipid hydroperoxides than the wild type strain. Hepatic tissue from mice inoculated with a tsaA mutant had lesions similar to those inoculated with the wild type, and included coagulative necrosis of hepatocytes. The liver and cecum colonizing abilities of the wild type and tsaA mutant were comparable. Up-expression of catalase in the tsaA mutants likely permits the bacterium to compensate (in colonization and virulence attributes) for the loss of an otherwise important oxidative stress-combating enzyme, alkyl hydroperoxide reductase. The use of erythromycin resistance insertion as a facile way to screen for gene-targeted mutants, and the chromosomal complementation of those mutants are new genetic procedures for studying H. hepaticus.

Helicobacter infection in hepatocellular carcinoma tissue

AIM: To investigate whether Helicobacter species (Helicobacter spp.) could be detected in hepatocellular carcinoma (HCC) tissue.

METHODS: Liver samples from 28 patients with hepatocellular carcinoma (HCC) diagnosed by histopa-thology were studied. Twenty-two patients with other liver diseases (5 with liver trauma, 7 with cavernous liver hemangioma, 6 with liver cyst and 4 with hepatolithiasis), 25 patients with gastric cancer, 15 with colonic cancer and 15 with myoma of uterus served as controls. Two pieces of biopsy were obtained from each patient. One was cultured for Helicobacter spp. and extraction of DNA, the other was prepared for scanning electron microscopy (SEM) and in situ hybridization. The samples were cultured on Columbia agar plates with microaerobic techniques. Helicobacter spp. in biopsy from the studied subjects was detected by polymerase chain reaction (PCR) with Helicobacter spp. 16S rRNA primers. Amplified products were identified by Southern hybridization and sequenced further. Besides, other genes (vacA, cagA) specific for Helicobacter pylori (H pylori) were also detected by PCR. Helicobacter spp. in biopsies was observed by SEM. Transmission electron microscopy (TEM) was performed to identify the cultured positive Helicobacter spp. The presence of Helicobacter spp. was detected by in situ hybridization to confirm the type of Helicobacter.

RESULTS: The positive rate of Helicobacter cultured in HCC and gastric cancer tissue was 10.7% (3/28) and 24%(6/25), respectively. Helicobacter microorganisms were identified further by typical appearance on Gram staining, positive urease test and characteristic colony morphology on TEM. The bacterium was observed in adjacent hepatocytes of the two HCC samples by SEM. The number of cocci was greater than that of bacilli. The bacterium was also found in four gastric cancer samples. PCR showed that the positive rate of HCC and gastric cancer samples was 60.7% and 72% respectively, while the controls were negative (P < 0.01). The PCR-amplified products were identified by Southern hybridization and sequenced. The homology to 16S rRNA of H pylori was 97.80%. The samples were verified by in situ hybridization for Helicobacter spp. 16S rRNA-mRNA and proved to be H pylori positive. There was no statistical significance between HCC and gastric cancer (P > 0.05), but the positive rate of HCC and controls had statistical significance (P < 0.01). Only 3 HCC samples and 2 gastric cancer samples of the cagA genes were detected. None of the samples reacted with primers for vacA in the two groups. As for the genotype of H pylori, type II had preference over type I.

CONCLUSION: Helicobacter infection exists in liver tissues of HCC patients. Helicobacter spp. infection is related with HCC, which needs further research.

Helicobacter pylori and hepatocellular carcinoma: correlated or uncorrelated?

Helicobacter pylori can be detected in liver tissue resected from patients with hepatocellular carcinoma. Conflicting reports regarding the relationship between H. pylori and hepatocellular carcinoma mean it is uncertain whether H. pylori acts as a troublemaker, co-risk factor or innocent bystander to the development of hepatocellular carcinoma. Clinical studies in patients without known causes of hepatocellular carcinoma are important to discover whether H. pylori is involved in the carcinogenesis of hepatocellular carcinoma. High quality prospective studies in patients with hepatocellular carcinoma, hepatitis C virus infection and no cirrhosis are needed to determine whether H. pylori is a co-risk factor for hepatocellular carcinoma.

Helicobacter hepaticus hydrogenase mutants are deficient in hydrogen-supported amino acid uptake and in causing liver lesions in A/J mice

Helicobacter hepaticus, a causative agent of chronic hepatitis and hepatocellular carcinoma in mice, expresses a nickel-containing hydrogen-oxidizing hydrogenase enzyme. Growth of a hyaB gene-targeted mutant was unaffected by the presence of hydrogen, unlike the wild-type strain, which showed an enhanced growth rate when supplied with H(2). Hydrogenase activities in H. hepaticus were constitutive and not dependent on the inclusion of H(2) during growth. Addition of nickel during growth significantly stimulated both urease (for wild-type and hyaB) and hydrogenase (for wild-type) activities. In a 5-h period, the extent of (14)C-labeled amino acid uptake by the wild type was markedly enhanced in the presence of hydrogen and was >5-fold greater than that of the hyaB mutant strain. In the presence of H(2), the short-term whole-cell amino acid uptake V(max) of the parent strain was about 2.2-fold greater than for the mutant, but the half-saturation affinity for amino acid transport was the same for the parent and mutant strain. The liver- and cecum-colonizing abilities of the strains was estimated by real-time PCR quantitation of the H. hepaticus-specific cytolethal distending toxin gene and showed similar animal colonization for the hyaB mutant and the wild type. However, at 21 weeks postinoculation, the livers from mice inoculated with wild type exhibited moderate lobular lymphoplasmacytic hepatitis with hepatocytic coagulative necrosis, but the hydrogenase mutants exhibited no histological evidence of lobular inflammation or necrosis.

Helicobacter pylori and extragastric diseases--other Helicobacters

The involvement of Helicobacter pylori in the pathogenesis of extragastric diseases continues to be an interesting topic in the field of Helicobacter-related pathology. Although conflicting findings have been reported for most of the disorders, a role of H. pylori seems to be important especially for the development of cardiovascular and hematologic disorders. Previously isolated human and animal Helicobacter sp. flexispira and "Helicobacter heilmannii" strains have been validated using polyphasic taxonomy. A novel enterohepatic Helicobacter has been isolated from mastomys and mice, adding to the list of helicobacters that colonize the liver. Genetic targets that may aid the classification of novel Helicobacter species have emerged. Animal models of Helicobacter-induced gastric and hepatobiliary diseases have offered insights to the mechanisms associated with premalignant transformation.