Candidate gene polymorphisms in solid cancers

The role of genetic polymorphisms for inducing genotoxicity in workers occupationally exposed to benzene: a systematic review

Benzene is used worldwide as a major raw material in a number of industrial processes and also a potent airborne pollutant emitted from traffic exhaust fume. The present systematic review aimed to identify potential associations between genetic polymorphisms and occupational benzene-induced genotoxicity. For this purpose, a total of 22 selected studies were carefully analysed. Our results revealed a positive relation between gene polymorphism and genotoxicity in individuals exposed to benzene, since 17 studies (out of 22) observed positive relations between genotoxicity and polymorphisms in xenobiotics metabolizing genes influencing, therefore, individuals' susceptibility to genomic damage induced by benzene. In other words, individuals with some genotypes may show increase or decrease DNA damage and/or higher or lower DNA-repair potential. As for the quality assessment, 17 studies (out of 22) were categorized as Strong or Moderate and, therefore, we consider our findings to be trustworthy. Taken together, such findings are consistent with the notion that benzene induces genotoxicity in mammalian cells being strongly dependent on the genetic polymorphism. Certainly, such findings are important for clarifying the role of biomarkers related to genotoxicity in human biomonitoring studies.

The impact of genetic polymorphisms on genotoxicity in workers occupationally exposed to pesticides: a systematic review

In a world with a rising use of pesticides, these chemicals, although designed to effectively control pests, pose potential threats to the environment and non-target organisms, including humans. Thus, this systematic review aims to investigate a possible association between genetic polymorphisms and susceptibility and genotoxicity in individuals occupationally exposed to pesticides. This review was conducted following the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. A total of 14 carefully selected studies were thoroughly analyzed by two reviewers, who assigned scores based on previously set evaluation criteria. This study classified over half of the chosen studies as having moderate or strong quality, observing a correlation between certain genetic polymorphisms involved in xenobiotic metabolism and genotoxicity in workers exposed to pesticides. Results suggest that the genes associated with xenobiotic metabolism play a substantial role in determining individuals' susceptibility to genomic damage due to pesticide exposure, affecting both their peripheral blood and oral mucosa. This implies that individuals with specific genotypes may experience increased or decreased levels of DNA damage when exposed to these chemicals.

Genetic polymorphism of interleukins 6 and 17 correlated with apical periodontitis: A Cross-sectional study

Interleukins 6 and 17 act in bone resorption in the presence of infections of endodontic origin for host defense. Genetic polymorphisms may be associated with increased bone loss, represented by areas of large periapical lesions. This study aimed to verify the frequency of interleukin 6 and 17 gene polymorphism in patients with asymptomatic apical periodontitis or chronic apical abscess and to verify the existence of correlations between periapical lesion area with age, gender, and presence of the polymorphism, in the studied population, in the state of Pernambuco. A population consisting of thirty diagnosed individuals was included. The area of the lesions was measured in mm². Genomic DNA was extracted and genotyping was performed by Polymerase Chain Reaction Restriction Fragment Length Polymorphism for interleukin 6 (rs 1800795) and interleukin 17 (rs 2275913). Fisher's exact, chi-square, and odds ratio tests were used. A logistic regression analysis was also performed using sex, age, and the presence of polymorphism as covariates, in addition to linear regression to test the relationship between age and lesion area. All tests used a significance level of 0.05% (p ≤0.05%). There was no statistical significance in the occurrence of large areas of periapical lesions correlated with age, sex, and diagnosis, nor in the distribution of alleles in the polymorphism of interleukins 6 and 17 in the studied groups. The frequency of homozygous and heterozygous polymorphism was high. The polymorphism of these interleukins is not correlated with the increase in the areas of asymptomatic periapical inflammatory lesions.

Genetic, Cellular and Molecular Aspects involved in Apical Periodontitis

The development, establishment and repair of apical periodontitis (AP) is dependent of several factors, which include host susceptibility, microbial infection, immune response, quality of root canal treatment and organism's ability to repair. The understanding of genetic contributions to the risk of developing AP and presenting persistent AP has been extensively explored in modern Endodontics. Thus, this article aims to provide a review of the literature regarding the biochemical mediators involved in immune response signaling, osteoclastogenesis and bone neoformation, as the genetic components involved in the development and repair of AP. A narrative review of the literature was performed through a PUBMED/MEDLINE search and a hand search of the major AP textbooks. The knowledge regarding the cells, receptors and molecules involved in the host's immune-inflammatory response during the progression of AP added to the knowledge of bone biology allows the identification of factors inherent to the host that can interfere both in the progression and in the repair of these lesions. The main outcomes of studies evaluated in the review that investigated the correlation between genetic polymorphisms and AP in the last five years, demonstrate that genetic factors of the individual are involved in the success of root canal treatment. The discussion of this review gives subsides that may help to glimpse the development of new therapies based on the identification of therapeutic targets and the development of materials and techniques aimed at acting at the molecular level for clinical, radiographic and histological success of root canal treatment.

Polymorphism of Sooty-fronted Spinetail (Synallaxis frontalis Aves: Furnariidae): Evidence of chromosomal rearrangements by pericentric inversion in autosomal macrochromosomes

The Passeriformes is the most diverse and cytogenetically well-known clade of birds, comprising approximately 5,000 species. The sooty-fronted spinetail (Synallaxis frontalis Aves: Furnariidae) species, which belongs to the order Passeriformes, is typically found in South America, where it is widely distributed. Polymorphisms provide genetic variability, important for several evolutionary processes, including speciation and adaptation to the environment. The aim of this work was to analyze the possible cytotypes and systemic events involved in the species polymorphism. Of the sampled 19 individuals, two thirds were polymorphic, an event supposedly linked to mutations resulting from genomic evolution that can be transmitted hereditarily. A chromosomal polymorphism was detected between the 1st and 3rdpairs of autosomal macrochromosomes. This type of polymorphism is related to a pericentric inversion in regions involving chromosomal rearrangements. Differently from other polymorphism studies that report a link between polymorphic chromosomes and phenotypic changes, S. frontalis did not present any morphological variation in the sampled individuals.

SMAD2 and the Relationship of Colorectal Cancer to Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) affecting the colon [Crohn's disease (CD) and ulcerative colitis (UC)] are associated with an increased risk of colorectal cancer (CRC). Our previous work using oligonucleotide array data indicated that SMAD2 was significantly underexpressed in UC dysplastic tissue compared to benign UC. The aim of this current study was to determine whether single nucleotide polymorphisms (SNPs) within the SMAD2 gene are associated with IBD dysplasia/cancer. We performed an SNP haplotype-based case-control association study. Leukocyte DNA was obtained from 489 unrelated Caucasians (158 UC, 175 CD, 71 CRC, 85 controls). Eleven SNPs were genotyped. All 11 SNPs were in Hardy-Weinberg equilibrium in the control population. Strong linkage disequilibrium was observed among nearly all SMAD2 SNPs. There were no significant associations between SMAD2 allele or haplotype frequencies. Power calculations indicated good power for single-marker analysis (>0.8) and reasonably good power against effects of 0.1–0.15 for haplotype analysis. SMAD2 SNPs were not associated with the development of IBD dysplasia/cancer. This incongruity between our previous microarray data and the findings from this genotype study may be attributed to mechanisms such as alternative splicing of pre-mRNA SMAD2 and/or cross talk with other cellular pathways.

Association between genetic polymorphisms in cortactin and susceptibility to gastric cancer

PURPOSE

Overexpression of cortactin (CTTN) in human tumors has been proposed to result in increased cell migration and metastatic potential. Here, we determined the frequencies of CTTN g.-9101C>T, g.-8748C>T, and g.72C>T polymorphisms in apparently healthy subjects and gastric cancer patients, respectively, and the influence of the CTTN polymorphisms on gastric cancer susceptibility.

METHODS

Blood samples were collected from 267 patients and 533 controls. CTTN g.-8748C>T and g.-9101C>T polymorphisms were determined using polymerase chain reaction-restriction fragment length polymorphism; the g.72C>T polymorphism was determined using the TaqMan method.

RESULTS

Genotype frequencies of the CTTN g.-9101C>T polymorphism were 97.5% (TT), 2.5% (TC), and 0% (CC) in the patient group, and 98.6% (TT), 1.4% (TC), and 0% (CC) in the control group. Genotype frequencies of the CTTN g.-8748C>T polymorphism were 93.3% (TT), 6.8% (TC), and 0% (CC) in the patient group, and 94.2% (TT), 5.8% (TC), and 0% (CC) in the control group. Genotype frequencies of the CTTN g.72C>T polymorphism were 82.4% (CC), 17.2% (CT), and 0.4% (TT) in the patient group, and 78.0% (CC), 20.1% (CT), and 1.9% (TT) in the control group. Genotype and allele frequencies of the CTTN g.-9101C>T polymorphism differed significantly between the advanced gastric cancer and control groups. Patients with advanced gastric cancer, possessing the TC genotype, had a significantly poorer prognosis than the group with the TT genotype.

CONCLUSION

The CTTN g.-9101C>T polymorphism might influence advanced gastric cancer susceptibility. However, the role of the CTTN g.-9101C>T, g.-8748C>T, and g.72C>T polymorphisms requires careful interpretation and confirmation through larger studies.

C936T polymorphism of the VEGF gene in relation to the risk and the clinical and biological characteristics of sporadic colorectal adenocarcinoma

Background

One of the main glycoproteins responsible for angiogenesis is the vascular endothelial growth factor. It is believed that C936T polymorphism, located in the VEGF gene, is correlated with susceptibility towards development of sporadic colorectal adenocarcinoma. The aim of this study was to identify the frequencies of the genotypes of C936T polymorphism of the VEGF gene in patients with sporadic colorectal adenocarcinoma, in comparison with controls, and whether this correlates with the degree of tumor invasion, lymph node involvement and occurrence of metastases at the time of the diagnosis. The analysis was done on 261 patients with sporadic colorectal adenocarcinoma and 261 controls. The genotypes of C936T polymorphism were evaluated by means of the polymerase chain reaction and enzyme digestion, using peripheral blood samples.

Results

The occurrences of genotype 936CC were similar in the two groups (80.5% versus 78.5%, p = 0.2288). In relation to tumor location, lymph node involvement, infiltration and tumor metastasis, no statistically significant results were obtained (p = 0.3116, p = 0.8485, p = 0.9408 and p = 0.2861, respectively).

Conclusion

C936T polymorphism of the VEGF gene did not influence the occurrence of sporadic colorectal adenocarcinoma development and did not correlated with the degree of tumor invasion, lymph node involvement and occurrence of metastases.

Polimorfismos genéticos: implicações na patogênese do carcinoma medular de tireóide

O carcinoma medular de tireóide (CMT) é uma neoplasia maligna rara, ocorrendo na forma esporádica ou hereditária. Mutações germinativas no proto-oncogene RET são responsáveis pelo CMT hereditário. No entanto, a maioria dos casos de CMT ocorre em indivíduos sem história familiar, na qual a patogênese da doença ainda é pouco compreendida. Os polimorfismos do gene RET são descritos na população geral assim como em pacientes com CMT. Embora estas variações alélicas aparentemente não confiram qualquer atividade transformadora no receptor RET, estudos sugerem que essas alterações genéticas podem modificar a suscetibilidade à doença e o fenótipo clínico em pacientes com CMT esporádico ou hereditário. Uma maior freqüência dos polimorfismos localizados nos exons 11 (G691S), 13 (L769L), 14 (S836S) e 15 (S904) é descrita em pacientes com CMT provenientes de países americanos e europeus. Na presente revisão, analisamos criticamente os resultados obtidos nos diferentes estudos e descrevemos a freqüência dos polimorfismos do RET em pacientes brasileiros com CMT esporádico.

Polymorphisms of short tandem repeat of genes and breast cancer susceptibility

AIM

To explore the relationship of short tandem repeat polymorphisms and breast cancer susceptibility.

METHODS

We searched the MEDLINE database (up to June 2006) with the keywords of tandem repeat sequences, gene polymorphisms, breast cancer, cancer susceptibility and microsatellite instability. We reviewed the literature on gene polymorphisms, especially the relationship of short tandem repeat and breast cancer risk.

RESULTS

We focused on the candidate genes sex hormones, steroid hormone and receptors, carcinogen metabolism, cell proliferation regulation and other genes.

CONCLUSIONS

The functional effects of short tandem repeat polymorphisms on cancer susceptibility, especially on breast cancer risk, are identified. The importance of short tandem repeat polymorphisms on development and progression of breast cancer are discussed.

Which gene is a dominant predictor of response during FOLFOX chemotherapy for the treatment of metastatic colorectal cancer, the MTHFR or XRCC1 gene?

BACKGROUND

Combination chemotherapy using oxaliplatin, 5-fluorouracil and folinic acid (FOLFOX) is known to be effective in the treatment of metastatic colon cancer. Genes regulating the actions of 5-fluorouracil and oxaliplatin have been identified, but precisely which gene is dominant has not yet been determined. The aim of the investigation reported here was to identify which gene polymorphism is a dominant factor in FOLFOX chemotherapy-the methylenetetrahydrofolate reductase (MTHFR) gene for 5-fluorouracil or the X-ray cross-complementing1 (XRCC1) gene for oxaliplatin.

METHODS

Paraffin-embedded tissues from 54 patients with unresectable metastases from colorectal cancer who had undergone chemotherapy with the FOLFOX regimen were analyzed for MTHFR polymorphisms in the MTHFR gene (677C-->T, Ala-->Val mutation) and XRCC1 gene (Arg-->Gln substitution in exon 10). Response rates and survivals were compared by types of polymorphism.

RESULTS

Analyses of the patterns of MTHFR polymorphism revealed that 29.6% of the patients showed no mutation, 51.6% showed heterozygous mutations, and 11.8% showed homozygous mutations. Analyses of the XRCC1 polymorphism revealed that 60.8% of the patients showed no mutation, 31.4% showed heterozygous mutations, and 7.8% showed homozygous mutations. After four cycles of chemotherapy, 3.7% showed a complete response, 57.4% showed a partial response (PD) or stable disease, and 38.9% showed PD. The MTHFR polymorphism was not significant in predicting response and 30-month-survival (P > .1), whereas the XRCC1 polymorphism was a significant prognostic factor for both response (P = .038) and survival (P = .011).

CONCLUSIONS

We found a higher rate of mutations in the MTHFR gene than in the XRCC1 gene in Korean colorectal cancer patients. Response to FOLFOX was better in the patient group with mutations for MTHFR and worse in the patient group with mutations for XRCC1. However, only the XRCC1 polymorphism was a significant prognostic factor for the response to FOLFOX chemotherapy and short-term survival.