Interleukin polymorphisms and differential methylation status in gastric cancer: an association with Helicobacter pylori infection

AIM

Interleukin polymorphisms and Helicobacter pylori infection are believed to play critical roles in DNA methylation, a process frequently associated with carcinogenesis. The aim of this study was to determine the associations between interleukin polymorphisms and methylation status of three genes related to gastric cancer. Furthermore, the influence of the H. pylori strains was evaluated.

MATERIALS & METHODS

75 gastric tumor samples had the DNA extracted for interleukin polymorphisms genotyping by PCR-RFLP, promoter methylation by MS-PCR and detection and subtyping of H. pylori by PCR.

RESULTS

In the cardia tumors, methylation in the COX-2 promoter was associated with IL1RN*2 (p = 0.015), and the associated genotypes IL1B511T + IL1RN*2 seem to be important in the methylation of COX-2 (p = 0.013), especially in the presence of cagA(+) (p = 0.026) and vacAs1 (p = 0.025) H. pylori strains. The associated genotypes IL6 CC+TNF GG seem to be involved in the unmethylation of CDKN2A (p = 0.046), along with H. pylori cagA(+) infection.

CONCLUSION

DNA methylation in gastric cancer seems to be influenced by the presence of interleukin polymorphisms and by the H. pylori cagA/vacAs1m1 strains.

CDKN2A promoter hypermethylation in astrocytomas is associated with age and sex

CDKN2A promoter hypermethylation has been widely related to many cancers. In astrocytomas, although CDKN2A (p16(INK4A) protein) is often inactivated, there are still some controversial issues regarding the mechanism by which this alteration occurs. Thus, we analyzed a series of astrocytomas to assess the association between CDKN2A expression and methylation of grade I-IV tumors (WHO) and clinicopathological parameters. DNA extracted from formalin-fixed paraffin-embedded material of 93 astrocytic tumors was available for CDKN2A promoter methylation analysis and p16(INK4A) expression by methylation-specific PCR and immunohistochemistry, respectively. A strong negative correlation between nuclear and cytoplasmic immunostaining and CDKN2A promoter methylation was found. Additionally, a significant negative correlation between CDKN2A promoter methylation and age was observed; also, female patients had statistically more CDKN2A methylated promoters (p = 0.036) than men. In conclusion, CDKN2A inactivation by promoter methylation is a frequent event in astrocytomas and it is related to the age and sex of patients.

Inactivation of COX-2, HMLH1 and CDKN2A gene by promoter methylation in gastric cancer: relationship with histological subtype, tumor location and Helicobacter pylori genotype

OBJECTIVE

We aimed to evaluate the inactivation of COX-2, HMLH1 and CDKN2A by promoter methylation and its relationship with the infection by different Helicobacter pylori strains in gastric cancer.

METHODS

DNA extracted from 76 H. pylori-positive gastric tumor samples was available for promoter methylation identification by methylation-specific PCR and H. pylori subtyping by PCR. Immunohistochemistry was used to determine COX-2, p16(INK4A) and HMLH1 expression.

RESULTS

A strong negative correlation was found between the expression of these markers and the presence of promoter methylation in their genes. Among cardia tumors, negativity of p16(INK4A) was a significant finding. On the other hand, in noncardia tumors, the histological subtypes had different gene expression patterns. In the intestinal subtype, a significant finding was HMLH1 inactivation by methylation, while in the diffuse subtype, CDKN2A inactivation by methylation was the significant finding. Tumors with methylated COX-2 and HMLH1 genes were associated with H. pylori vacA s1 (p = 0.025 and 0.047, respectively), and the nonmethylated tumors were associated with the presence of the gene flaA.

CONCLUSIONS

These data suggest that the inactivation of these genes by methylation occurs by distinct pathways according to the histological subtype and tumor location and depends on the H. pylori genotype.

Differential expression of MYC in H. pylori-related intestinal and diffuse gastric tumors

Evidence suggests that the carcinogenic process guided by Helicobacter pylori is related to the expression of cell cycle and apoptosis proteins as BCL-2, BAX, and MYC. However, the literature is conflicting regarding the expression frequency in the histological subtypes and did not consider cagA gene presence. To investigate the expression of these proteins considering the histological subtypes of gastric cancer associated with H. pylori (cagA), a total of 89 cases were used. H. pylori infection and cagA status were determined by PCR. Immunodetection was performed for MYC, BCL-2, and BAX proteins. H. pylori was found in 95.5% of the patients, among them, 65.8% were cagA(+). Nuclear MYC was detected in 36.4%, BAX in 55.7%, while BCl-2 in just 5%. Nuclear MYC staining was significantly lower in the intestinal than diffuse subtype (p = 0.008) and was related with the presence of H. pylori cagA(+). Additionally, most of the few cases cytoplasmic MYC positive were in the intestinal subtype. In diffuse tumors, although most nuclear MYC positive cases were cagA(+), it was not significant. No difference was observed between BCL-2 or BAX expression considering the presence of cagA gene in the histological subtypes. It seems that MYC could be relevant for the diffuse tumorigenic pathway associated with H. pylori and possibly influenced by the presence of cagA gene, while in intestinal tumors, the tumorigenic pathway does not occur through the MYC expression.

CDKN2A promoter methylation is related to the tumor location and histological subtype and associated with Helicobacter pylori flaA(+) strains in gastric adenocarcinomas

Promoter hypermethylation of CDKN2A (p16INK4A protein) is the main mechanism of gene inactivation. However, its association with Helicobacter pylori infection is a controversial issue. Therefore, we examined a series of gastric adenocarcinomas to assess the association between p16INK4A inactivation and H. pylori genotype (vacA, cagA, cagE, virB11 and flaA) according to the location and histological subtype of the tumors. p16INK4A expression and CDKN2A promoter methylation were found in 77 gastric adenocarcinoma samples by immunohistochemistry and methylation-specific PCR, respectively. Helicobacter pylori infection and genotype were determined by PCR. A strong negative correlation between immunostaining and CDKN2A promoter region methylation was found. In diffuse subtype tumors, the inactivation of p16INK4A by promoter methylation was unique in noncardia tumors (p=0.022). In addition, H. pylori-bearing flaA was associated with non-methylation tumors (p=0.008) and H. pylori strain bearing cagA or vacAs1m1 genes but without flaA was associated with methylated tumors (p=0.022 and 0.003, respectively). Inactivation of p16INK4A in intestinal and diffuse subtypes showed distinct carcinogenic pathways, depending on the tumor location. Moreover, the process of methylation of the CDKN2A promoter seems to depend on the H. pylori genotype. The present data suggest that there is a differential influence and relevance of H. pylori genotype in gastric cancer development.

p27KIP1 expression in gastric cancer: differential pathways in the histological subtypes associated with Helicobacter pylori infection

OBJECTIVE

Decreases in p27(KIP1) and C-MYC expression have been associated with Helicobacter pylori infection. Furthermore, C-MYC seems to be a transcriptional repressor of p27(KIP1). Therefore, in a series of gastric adenocarcinomas we studied the association of p27(KIP1) expression with H. pylori genotype (vacA, cagA, cagE and virB11) and the involvement of C-MYC in this process.

MATERIAL AND METHODS

Expression of p27(KIP1) and C-MYC was determined by immunohistochemistry in 84 gastric adenocarcinoma samples and H. pylori infection and genotype were determined by polymerase chain reaction.

RESULTS

Most p27(KIP1)-negative cases (94.0%) were H. pylori-positive and 44.8% were C-MYC-positive. In the diffuse gastric cancer subtype, p27-negative-C-MYC-positive was the most frequent combination (cluster II), and was associated with the more pathogenic H. pylori strains. Although an association with p27(KIP1) and H. pylori strain was found in the intestinal gastric cancer subtype, negativity for p27(KIP1) and C-MYC markers was the most frequent cluster, followed by cluster II, and both were present, independent of the H. pylori genotype.

CONCLUSIONS

Reduced expression of p27(KIP1) was closely linked to H. pylori infection, and was dependent on the more pathogenic strains. Moreover, intestinal and diffuse subtypes showed distinct carcinogenic pathways influenced by H. pylori strains. These data add insight to the differential influence and relevance of H. pylori genotype in gastric cancer development.

[Social representations of generic drugs by pharmacists: determination of the central and peripheral representational systems]

This article aimed to identify the central and peripheral systems in social representations of generic drugs by pharmacists, as well as their social and economic profile, thereby establishing potential mechanisms for improving policies for generic drugs in Brazil. The data collection instruments were a questionnaire and a word association test, the inductive cue of which was the term "generic drug". Data collected through the questionnaire produced a profile of pharmacists in the city of Natal, Rio Grande do Norte State, and key information related to the theme. Data analysis for the word association test used Evoc 99 software while content analysis used Bardin, thereby identifying the central system in social representations of generic drugs, consisting of the categories price, quality, and credibility, while the peripheral system consisted of the categories pharmaceutical care, social impact, novelty, accessibility, options, and interchangeability.