TAS2R38 polymorphisms, Helicobacter pylori infection and susceptibility to gastric cancer and premalignant gastric lesions

BACKGROUND

Gastric cancer is worldwide the fourth more common cancer type by incidence, and the third by mortality. We analyzed three missense variants of TAS2R38 gene: rs713598 (A49P), rs1726866 (V262A), and rs10246939 (I296V). These variants and their combination in haplotypes (proline, alanine and valine/tasters or alanine, valine and isoleucine/nontasters) and diplotypes are responsible for individual differences in bitter perception. The single-nucleotide polymorphisms and the related phenotypes are known to be associated with susceptibility to Gram-negative bacterial infections, such as Helicobacter pylori , and with risk of various cancer types. An association between intermediate tasters (as defined by TAS2R38 diplotypes) and increased risk of gastric cancer was reported in a Korean population.

METHODS

We analyzed 2616 individuals of Latin American origin, representing the whole spectrum of lesions from gastritis to gastric cancer.

RESULTS

Comparing cancer cases vs. noncancers we observed a decrease in risk associated with heterozygous carriers of rs10246939 ( P  = 0.006) and rs1726866 ( P  = 0.003) when compared with homozygotes of the more common allele. Also, the analysis of diplotypes/phenotypes reflected the same association, with super-tasters showing a borderline increased risk of developing gastric cancer compared to medium-tasters [odds ratio (OR) = 1.63; 95% confidence interval (CI), 1.04-2.56; P  = 0.033]. Also, nontasters showed an increased risk when compared to medium-tasters although not reaching statistical significance (OR = 1.58; 95% CI, 0.80-2.87; P  = 0.203). We also tested the interactions between the TAS2R38 genotypes and H. pylori cagA status in a subset of samples and found no interaction.

CONCLUSION

In conclusion, our results suggest only a modest contribution of TAS2R38 gene genetic variability in gastric cancer etiology.

Genetic polymorphisms in the cag pathogenicity island of Helicobacter pylori and risk of stomach cancer and high-grade premalignant gastric lesions

Helicobacter pylori (Hp) infects the stomach of about half of the human population and is strongly associated with the risk of gastric cancer (GC) and its premalignant precursors. The cag pathogenicity island (cagPAI) is a region of the Hp genome encoding for key molecular machinery involved in the infection process. Following a sequencing study, we selected 50 genetic polymorphisms located in seven cagPAI genes and tested their associations with the risk of advanced gastric premalignant lesions and GC in 1220 subjects from various Latin American populations showing the whole spectrum of phenotypes from gastritis to GC. We found that three polymorphisms of cagA are associated with the risk of advanced gastric premalignant lesions (incomplete intestinal metaplasia [ie, Type 2 and 3] or dysplasia), and that six polymorphisms located in cagA, cagL and cagI were associated with risk of GC. When corrected for multiple testing none of the associations were statistically significant. However, scores built by integrating the individual polymorphisms were significantly associated with the risk of advanced gastric premalignant lesions and GC. These results have the potential of establishing markers for risk stratification in the general population, in view of targeting Hp eradication to high-risk population groups.

Variations in cag pathogenicity island genes of Helicobacter pylori from Latin American groups may influence neoplastic progression to gastric cancer

Helicobacter pylori (HP) colonizes the human stomach and induces acute gastritis, peptic ulcer disease, atrophic gastritis, and gastric adenocarcinoma. Increased virulence in HP isolates derives from harboring the cag (cytotoxin-associated genes) pathogenicity island (cagPAI). We analyzed the microvariants in cagPAI genes with the hypothesis that they may play an important role in determining HP virulence. We tested DNAs from cagA positive patients HP isolates; a total of 74 patients with chronic gastritis (CG, N = 37), intestinal metaplasia (IM, N = 21) or gastric cancer (GC, N = 16) from Mexico and Colombia. We selected 520 non-synonymous variants with at least 7.5% frequency in the original sequence outputs or with a minimum of 5 isolates with minor allele. After adjustment for multiple comparisons, no variants were statistically significantly associated with IM or GC. However, 19 non-synonymous showed conventional P-values < 0.05 comparing the frequency of the alleles between the isolates from subjects with gastritis and isolates from subjects with IM or GC; 12 of these showed a significant correlation with the severity of the disease. The present study revealed that several cagPAI genes from Latin American Western HP strains contains a number of non-synonymous variants in relatively high frequencies which could influence on the clinical outcome. However, none of the associations remained statistically significant after adjustment for multiple comparison.

Risk factors for gastric precancerous and cancers lesions in Latin American counties with difference gastric cancer risk

OBJECTIVE

To evaluate the risk factors associated with pre-neoplastic lesions and gastric cancer in countries with different cancer risk in Latin America.

METHODS

1222 questionnaires of risk factors related to pre-neoplastic lesions and gastric cancer were obtained from patients from Mexico (N = 559), Colombia (N = 461) and Paraguay (N = 202), who were treated at the gastroenterology or oncology service of participant hospitals. In addition, biopsies specimens to establish histological diagnosis and blood to detect IgG antibodies against Helicobacter-pylori (H. pylori) whole-cell antigens and CagA protein using an ELISA were collected. These consisted of 205 gastric cancer, 379 pre-neoplastic (intestinal metaplasia (IM) / atrophic gastritis) and 638 control (normal /non-atrophic gastritis) cases. The odds ratio (OR) and 95% confidence intervals (CI) associated with potential risk factors were estimated by polynomial logistic regression model.

RESULTS

Seropositivity to H. pylori was associated with risk of pre-neoplastic lesions, with OR = 1.9 (CI 95% 1.2-2.9; p = 0.006). Grain / cereal intake (OR = 1.6, 95% CI 1.0-2.5 ; p = 0.049) and egg intake (OR = 1.7 95% CI 1.1-2.6 ; p = 0.021) were related to gastric cancer. Among, people who did not developed gastric cancer, smoking more than five cigarette per day had the highest risk of being infected by H. pylori (OR = 1.9; CI 95% 1.1-3.3 ; p = 0.028).

CONCLUSION

The present study in Latin American countries confirmed that similar environmental factors such as smoking and grain/cereal consumption were associated with H. pylori infection and its induced gastric lesions as reported in other regions where dominant H. pylori strains differ.

Potential Role of Biofilm Formation in the Development of Digestive Tract Cancer With Special Reference to Helicobacter pylori Infection

Bacteria are highly social organisms that communicate via signaling molecules and can assume a multicellular lifestyle to build biofilm communities. Until recently, complications from biofilm-associated infection have been primarily ascribed to increased bacterial resistance to antibiotics and host immune evasion, leading to persistent infection. In this theory and hypothesis article we present a relatively new argument that biofilm formation has potential etiological role in the development of digestive tract cancer. First, we summarize recent new findings suggesting the potential link between bacterial biofilm and various types of cancer to build the foundation of our hypothesis. To date, evidence has been particularly convincing for colorectal cancer and its precursor, i.e., polyps, pointing to several key individual bacterial species, such as Bacteroides fragilis, Fusobacterium nucleatum, and Streptococcus gallolyticus subsp. Gallolyticus. Then, we further extend this hypothesis to one of the most common bacterial infection in humans, Helicobacter pylori (Hp), which is considered a major cause of gastric cancer. Thus far, there has been no direct evidence linking in vivo Hp gastric biofilm formation to gastric carcinogenesis. Yet, we synthesize the information to support an argument that biofilm associated-Hp is potentially more carcinogenic, summarizing biological characteristics of biofilm-associated bacteria. We also discuss mechanistic pathways as to how Hp or other biofilm-associated bacteria control biofilm formation and highlight recent findings on Hp genes that influence biofilm formation, which may lead to strain variability in biofilm formation. This knowledge may open a possibility of developing targeted intervention. We conclude, however, that this field is still in its infancy. To test the hypothesis rigorously and to link it ultimately to gastric pathologies (e.g., premalignant lesions and cancer), studies are needed to learn more about Hp biofilms, such as compositions and biological properties of extracellular polymeric substance (EPS), presence of non-Hp microbiome and geographical distribution of biofilms in relation to gastric gland types and structures. Identification of specific Hp strains with enhanced biofilm formation would be helpful not only for screening patients at high risk for sequelae from Hp infection, but also for development of new antibiotics to avoid resistance, regardless of its association with gastric cancer.

Rapid evolution of the Helicobacter pylori AlpA adhesin in a high gastric cancer risk region from Colombia

To be able to survive, Helicobacter pylori must adhere to the gastric epithelial cells of its human host. For this purpose, the bacterium employs an array of adhesins, for example, AlpA. The adhesin AlpA has been proposed as a major adhesin because of its critical role in human stomach colonization. Therefore, understanding how AlpA evolved could be important for the development of new diagnostic strategies. However, the genetic variation and microevolutionary patterns of alpA have not been described in Colombia. The study aim was to describe the variation patterns and microevolutionary process of alpA in Colombian clinical isolates of H. pylori. The existing polymorphisms, which are deviations from the neutral model of molecular evolution, and the genetic differentiation of the alpA gene from Colombian clinical isolates of H. pylori were determined. The analysis shows that gene conversion and purifying selection have shaped the evolution of three different variants of alpA in Colombia.

Helicobacter pylori strain genotyping based on the amplification and sequencing of cagA gene

Relevance: H. pylori presence has been described as a high risk factor of suffering gastric cancer, which is the fourth most common cancer in Colombia. Some studies [1, 2]; point out that when a genotypic characterization of different strains of this microorganism is carried out, more than one genotype can be found in the same patient can be found.

Purpose: To characterize different H.pylori cagA genotypes that occur in the same patient sample (biopsy) applying molecular and bioinformatic techniques.

Methods: cagA positive strains (n=35) from Instituto Nacional de Cancerología (Bogotá-Colombia), bank s samples were included as study material. Tissue DNA was extracted and used to amplify the 3’ region of the cagA gene by PCR [3]. The NTC11637 H. pylori strain was included as a positive control. PCR products were visualized in 2% agarose gels and the amplified fragments were purified using a commercial kit. As a final stage, a precipitation based on ethanol and EDTA was done and reaction products were sequenced. The obtained sequences were edited and submitted to a bioinformatic analysis using AASA, a program designed to characterize the EPIYA phosphorylation motifs localized in the C-terminal of the CagA protein by Rothstain, Yañez and Vivas (Los Andes University Thesis, 2008).

Results: The molecular and bioinformatic approach described allowed strain characterization. The applied strategy leads to verify the presence of the A, B and C EPIYA motifs in different combinations. ABC group was the most frequent motif found (48%). These results match those of previous reports in Colombia, nevertheless it is important to remark that amplicons with different molecular sizes can have the same EPIYA motif and that amplicons with similar sizes can have different EPIYA motifs.

Conclusions: The current strategy demonstrated to be useful in the identification and posterior characterization of more than one genotype of the different H. pylori strains present in the same biopsy sample. This molecular and bioinformatics approach combined with other techniques seems to be a good alternative to establish if an infection by H. pylori is the result of a coinfection or a microevolution process.

References: 1. Aras, R.A., et al., Natural variation in populations of persistently colonizing bacteria affect human host cell phenotype. The Journal of infectious diseases, 2003. 188(4): p. 486-496. 2. Panayotopoulou, E., et al., Strategy to characterize the number and type of repeating EPIYA phosphorylation motifs in the carboxyl terminus of CagA protein in Helicobacter pylori clinical isolates?†. Journal of Clinical Microbiology, 2007. 45(2): p. 488-495. 3. Yamaoka, Y., et al., Relationship between the cagA 3'repeat region of Helicobacter pylori, gastric histology, and susceptibility to low pH. Gastroenterology, 1999. 117(2): p. 342-349.

Abstract C22: Telomerase activity and HR-HPV infection frequently are present before detection of high grade cervical lesions

Telomerase activation have been considered as a fundamental step in the immortalization process because majority nonmalignant somatic tissue shows undetectable or no telomerase activity. A few numbers of studies in cervical cancer have showed an increase in the telomerase activity with grade of lesion, and Human Papillomavirus (HPV) infection has been associated in some studies with telomerase activation. However until now there are not follow up studies that measure the telomerase activity along the time. We describe here results about telomerase activity and HPV infection during 7 years of follow up in women that belong to the Bogotá cohort.

Samples were obtained every six months during follow up and we had in average four samples by woman. Telomerase activity was analyzed in 58 samples of 17 women that during follow up developed High Grade Squamous Intraepithelial Lesions (HGSIL) and 149 samples of 34 women that during follow up had normal cytology using a TeloTAGGG Telomerase PCR ELISA kit (Roche Applied Science). The HPV infection was previously tested using a GP5+/GP6+mediated PCR-EIA and typing using a Reverse Line Blot assay (RLB).

Of the 17 women that developed HGSIL along follow up; 12 (70.5%) had HPV infection and telomerase activity at the same time of HGSIL diagnosis or in a previous visit, these women had infections with high risk types (HR) principally with those belong to the alpha 9 specie, 2 (17.7%) showed only transitory events of HPV infection and 2 (11.8%) had normal cytology without HPV infection or telomerase activity. Average time to develop HGSIL was 13.5 months. In normal women we observed diverse results. Of the 34 women; 21 (61.8%) had HPV transitory infections with high risk and/or low risk types sometime during follow up and only 12 (35.2%) of them were positive for telomerase activity sometime in follow up independently of HPV infection. Interestingly, 8 (23.5%) women had HPV-HR infection during follow up and they were never positive for telomerase activity and 5 (14.7%) women didn't have HPV infection and telomerase activity.

Detection of HR-HPV infection and telomerase activity at the same time likes to predict the risk of HGSIL. Our results support the idea that telomerase activity and HR-HPV infection can be used as progression markers for the development of HGSIL.

Citation Information: Cancer Res 2009;69(23 Suppl):C22.

Two L1-peptides are excellent tools for serological detection of HPV-associated cervical carcinoma lesions

A persistent high risk human papillomavirus (HR-HPV) infection causes cervical intraepithelial lesions and cervical carcinoma. There is evidence that detecting anti-L1 antibodies could be successfully used for discriminating between cervical lesion patients and women having normal cytology. It was found that peptides 18283 (55PNNNKILVPKVSGLQYRVFR74) and 18294 (284LYIKGSGSTANLASSNYFPT300) from the L1-surface exposed regions were specifically recognised by antibodies from the cervical lesion patient sera. These peptides were tested against 165 womens' normal cytology sera and 148 cervical lesion or cervical cancer patients' sera. Less than 3.6% of women's normal cytology sera recognised peptides 18283 or 18294; on the contrary, 91% to 96% of the cervical lesion (CIN I to CIN III) or cervical cancer patient sera recognised peptides 18283 and 18294. These data show that anti-peptide 18283 and 18294 antibodies in the patients' sera are strongly associated with the presence of HR-HPV associated cervical lesions, showing 92-97% sensitivity and 89-95% specificity in recognising precancerous and cervical cancer patients. These two peptides could be excellent tools for use in large-scale serological screening of women populations at risk of developing cervical carcinoma.

Changes in tyrosine phosphorylation associated with true capacitation and capacitation-like state in boar spermatozoa

Capacitation is defined as a series of events that render boar sperm competent to fertilize, either in vivo or in vitro. Moreover, preliminary stages of cryopreservation of spermatozoa involving cooling to 5 degrees C have been shown to induce capacitation-like changes in boar spermatozoa. Capacitation of boar spermatozoa is accompanied by protein phosphorylation, however the relationship between both processes is poorly understood. Capacitation status was assessed by chlortetracycline (CTC) staining. Changes in protein tyrosine phosphorylation were examined in pre-cleared whole cell lysates using a specific anti-phosphotyrosine monoclonal antibody. Our results in boar spermatozoa show a significant positive correlation between p32 tyrosine phosphorylation levels and percentage of capacitated (CTC pattern B) spermatozoa. Moreover, incubation of boar spermatozoa with two unrelated tyrosine kinase inhibitors induces a significant reduction in the percentages of capacitated and acrosome-reacted (AR) boar spermatozoa and a reduction in the p32 tyrosine phosphorylation. In our conditions, cooling boar spermatozoa to 5 degrees C and rewarming to 39 degrees C in a noncapacitating medium results in similar CTC staining patterns to those obtained after incubation of boar sperm for 1 or 4 hr at 39 degrees C in a capacitating medium. However, cooled-rewarmed fails to induce an increase in p32 tyrosine phosphorylation in boar spermatozoa. Moreover, CTC staining patterns of cooled-rewarmed spermatozoa do not change after incubation with a tyrosine kinase inhibitor. In conclusion, our results show a direct relationship between capacitation and tyrosine phosphorylation and suggest that p32 tyrosine phosphorylation levels could be used as a marker of the true capacitation changes observed in boar spermatozoa. Moreover, our results show that true capacitation and capacitation-like changes induced after cooling involve alternative intracellular tyrosine phosphorylation pathways in boar spermatozoa.