XRCC1 R194W and R399Q Polymorphisms and Colorectal Cancer Risk in a Northeastern Mexican Population

Colorectal cancer (CRC) is one of the most common cancers worldwide. Its etiopathogenesis is complex, mainly influenced by genetic instability caused by the accumulation of mutations. The XRCC1 gene, which is involved in DNA repair, has been associated with CRC through the R194W (C194T) and R399Q (G399A) polymorphisms, but the results are inconsistent. Here, we analyzed the association of these polymorphisms with sporadic CRC in a northeastern Mexican population, including 155 male CRC patients and 155 male controls. Genotyping was performed using the RFLP method. An association with CRC was found for the 399A allele (G vs A; OR = 1.48 (1.03-2.13), P=0.034) and for the 399AA genotype in a codominant model (AA vs GG; OR = 3.11 (1.06-9.10), P=0.031). In contrast, there were no significant differences between CRC patients and controls for the C194T polymorphism (C vs T; OR = 0.82 (0.52-1.31), P=0.41). These results are consistent with many similar studies, but further research is needed to verify whether the XRCC1 R194W and R399Q polymorphisms play a role in CRC etiology. The functional significance of these polymorphisms is unclear, but some studies suggest that they influence DNA repair capacity and, thus, cancer risk.

Association of the rs8720 and rs12587 KRAS Gene Variants with Colorectal Cancer in a Mexican Population and Their Analysis In Silico

Colorectal cancer (CRC) is a major global health challenge and one of the top 10 cancers in Mexico. Lifestyle and genetic factors influence CRC development, prognosis, and therapeutic response; identifying risk factors, such as the genes involved, is critical to understanding its behavior, mechanisms, and prognosis. The association between KRAS gene variants (rs8720 and rs12587) and CRC in the Mexican population was analyzed. We performed in silico analysis and analyzed 310 healthy individuals and 385 CRC patients using TaqMan assays and real-time PCR. The CC and GG genotypes of rs8720 and rs12587 were identified as CRC risk factors (p < 0.05). The CC and TC genotypes of the rs8720 were associated with rectal cancer, age over 50 years, moderately differentiated histology, and advanced cancer stage. TG and GG genotypes of the rs12587 variant were a risk factor in the CRC group, in patients with stage I-II, males, and stage III-IV non-chemotherapy response. The TG haplotype is protected against CRC. The combined CCGG genotype was linked to CRC risk. In silico analysis revealed that the rs12587 and rs8720 variants could influence KRAS gene regulation via miRNAs. In conclusion, rs8720 and rs12587 variants of the KRAS gene were associated with CRC risk and could influence KRAS regulation via miRNAs.

A novel mutation in the TSC2 gene protects against colorectal cancer in the Mexican population

INTRODUCTION

Colorectal cancer (CRC) is a complex disease due to the large number of factors that influence its development, including variants in tumor suppressor genes.

OBJECTIVE

To estimate allelic and genotypic frequencies of c.3915G>A and c.5371G>A variants of the TSC2 gene in a Mexican population with CRC, as well as to analyze their association with the development of CRC.

METHODS

126 peripheral blood samples from patients diagnosed with sporadic CRC and 134 from healthy individuals, regarded as the control group, were included. Identification of genotypes was carried out using traditional PCR and enzymatic digestion. All individuals signed an informed consent letter.

RESULTS

The A allele of the c.3915G>A variant (OR = 0.31, 95% CI = 0.15-0.69, p = 0.004), as well as A/G haplotype of the c.3915G>A and c.5371G>A variants (OR = 0.28, 95% CI = 0.12-0.68, p = 0.005) showed a possible protective effect against sporadic CRC. In silico analysis indicated that both variants generate modifications in the splicing process.

CONCLUSION

The presence of TSC2 gene c.3915G>A variant suggests a possible protective effect against sporadic CRC in the Mexican population; however, no association was observed with the c.5371G>A variant.

Association of the 5HTTLPR Polymorphism with Obesity in Mexican Women with High Native American Ancestry

Aims: The 5HTT gene has been associated with obesity; this study aimed to determine the association between L- and S-alleles at the 5HTTLPR polymorphism with obesity in indigenous Mexican populations. Materials and Methods: A total of 362 individuals, 289 belonging to eight Native American (NA) groups; 40 Mexican mestizos; and 33 Caucasian Mennonites were enrolled in a cross-sectional study. High (≥90%) and low (<90%) NA ancestry was molecularly determined. A body mass index >30 kg/m² was considered as obese. The L- and S-alleles of the 5HTTLPR locus were identified by PCR; the association between alleles and obesity was performed by logistic regression analysis. Results: A significantly lower prevalence of obesity (35%) was observed in participants from communities with high NA ancestry (p < 0.005). Under a dominant heritance model the L-allele was associated with obesity in women with high NA ancestry (odds ratio [OR] 7.27; 95% confidence interval [CI] 1.6-32.5; p = 0.009) but not in women with low NA ancestry (OR 0.83; 95% CI 0.3-2.2; p = 0.71); no association was observed in men. Conclusion: Our results suggest that the 5HTTLPR L-allele is a risk factor for developing obesity in Mexican women with high NA ancestry (≥90%).

Association of the MTHFR 677C>T Polymorphism with Obesity and Biochemical Variables in a Young Population of Mexico

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms have been associated with overweight people and obesity. The goal of this study was to investigate the relationship of the MTHFR 677C>T polymorphism with obesity and biochemical variables in young individuals of Mexico.

METHODS

A total of 316 young individuals were included in the study, 172 with normal weight (NW) and 144 with over weight/obesity. Body mass index (BMI) was classified as NW, overweight, and obesity. Also, waist circumference was measured. Moreover, glucose, total cholesterol, and triglycerides were determined. Genotyping for MTHFR 677C>T polymorphism was performed by the PCR-RFLP method.

RESULTS

There was no difference in the distribution of the MTHFR 677C>T polymorphism between individuals with NW and overweight/obesity; neither when they were divided by overweight vs NW, nor when we contrasted obese vs NW. However, an analysis stratified by gender showed a significant protector effect of the TT genotype against obesity in males and elevated waist circumference in females. Also, overweight/obese individuals with TT genotype had less risk of high cholesterol or triglycerides than overweight/obese subjects with the other genotypes.

CONCLUSIONS

These results suggest that the MTHFR 677T polymorphism might not be a risk factor for being overweight/obesity. Rather, on the basis of our results, this variant could be a protector effect. However, further large-scale population-based studies are still necessary to clarify the role of the MTHFR 677C>T polymorphism in overweight, obesity, and lipid profile level.

TYMS 2R3R polymorphism and DPYD [IVS]14+1G>A gene mutation in Mexican colorectal cancer patients

OBJECTIVE

To examine the association between TYMS 2R3R polymorphism and DPYD [IVS]14+1G>A mutation by comparing healthy subjects with colorectal cancer (CRC) patients in the Mexican population.

METHOD

Genotyping of the 2R/3R was performed by polymerase chain reaction (PCR) and [IVS]14+1G>A mutation by real-time PCR analysis.

RESULTS

The observed frequencies of the TYMS 2R3R polymorphism and the -[IVS]14+1G>A mutation in DPYD did not indicate an increased risk for CRC (p>0.05). However we observed an association of the 2R/2R (OR 3.08, 95% CI 1.66-6.08, p=0.0017) and heterozygous (OR 1.98, 95% CI 1.32-2.97, p=0.0012) genotypes as risk factors when comparing controls and CRC patients that were also tobacco consumers. An association between the genotype and the disease was evident. The distribution of the 2R/2R genotype and hematological toxicity (adjusted OR 2.26, 95% CI 1.54-4.45, p=0.0259), heterozygous (2R/3R) with tumor stage III-IV (OR 1.81, 95% CI 1.11-2.94, p=0.020) and 2R/2R-2R/3R in non-chemotherapy response CRC patients with hematological (OR 2.3, 95% CI 1.21-4.4, p=0.014) and gastric toxicities (OR 3.11, 95% CI 1.18-8.2, p=0.035) confirmed that this factor may significantly contribute to the CRC susceptibility.

CONCLUSION

TYMS 2R3R polymorphism and the -[IVS]14+1G>A mutation in DPYD was not associated with susceptibility to CRC. However, the 2R/2R and 2R/3R genotypes of TYMS polymorphism could significantly contribute to hematological and gastric toxicity in CRC patients in this sample population.

Calpain-10 gene polymorphisms and risk of type 2 diabetes mellitus in Mexican mestizos

The calpain-10 gene is expressed primarily in tissues important in glucose metabolism; thus, some of its polymorphisms have been associated with type 2 diabetes. In this study, we examined the association between the calpain-10 single-nucleotide polymorphism (SNP)-43, SNP-19, and SNP-63 and type 2 diabetes in Mexican mestizos. We included 211 patients and 152 non-diabetic subjects. Polymerase chain reaction was used to identify alleles. We compared allele, genotype, haplotype, and diplotype frequencies between both groups and used the chi-square test to calculate the risk. The allele frequency of SNP-43 allele 1 was 70% in controls and 72% in patients; the GG, GA, and AA genotype frequencies were 48.7, 42.8, and 8.5% in controls and 51.2, 41.7, and 7.1% in patients, respectively. For SNP- 19, the prevalence of allele 1 (2R) was 32% in controls and 39% in patients. In controls, homozygosity (2R/2R) was 10.5%, heterozygosity was 42.8%, and 3R/3R was 46.7%; in cases, these values were 13.3, 50.7, and 36.0%, respectively. For SNP-63, the frequency of allele 1 was 87% in controls and 83% in patients; genotype frequencies in controls were 75.7% (CC), 23% (CT), and 1.3% (TT), and were 69.7, 27.5, and 2.8%, respectively for the cases. Genotype distributions were consistent with Hardy-Weinberg equilibrium. No significant intergroup differences for allele, genotype, haplotype, or diplotype frequencies were observed. We found no association between these polymorphisms and diabetes. However, our sample size was small, so the role of calpain-10 risk alleles should be further examined.

The association between the 844ins68 polymorphism in the CBS gene and breast cancer

INTRODUCTION

The cystathionine beta synthase (CBS) gene plays an important role in homocysteine metabolism because it catalyzes the first step of the transsulfuration pathway, during which homocysteine is converted to cystathionine. Polymorphisms of CBS have been associated with cancer.

MATERIAL AND METHODS

We examined the role of the 844ins68 polymorphism by comparing the genotypes of 371 healthy Mexican women with the genotypes of 323 Mexican women with breast cancer (BC).

RESULTS

The observed genotype frequencies for controls and BC patients were 1% and 2% for Ins/Ins, 13% and 26% for W/Ins, and 86% and 72% for W/W, respectively. We found that the odds ratio (OR) was 2.2, with a 95% confidence interval (95% CI) of 1.5-3.3, p = 0.0001. The association was also evident when comparing the distribution of the W/Ins-Ins/Ins genotypes in patients in the following categories: 1) menopause and high γ-glutamyltransferase (GGT) levels (OR of 2.17, 95% CI: 1.17-4.26, p = 0.02), 2) chemotherapy response and high lactate dehydrogenase (LDH) levels (OR 2.2, 95% CI: 1.08-4.4, p = 0.027), 3) chemotherapy response and high GGT levels (OR 2.46, 95% CI: 1.2-4.8, p = 0.007), and 4) body mass index (BMI) and III-IV tumor stage (OR 3.2, 95% CI: 1.2-8.3, p = 0.013).

CONCLUSIONS

We conclude that the genotypes W/Ins-Ins/Ins of the 844ins68 polymorphism in the CBS gene contribute significantly to BC susceptibility in the analyzed sample from the Mexican population.

[Enviromental factors related to depressive disorders]

BACKGROUND

As a result of their high prevalence, mayor depressive disorder single episode (MDDSE); major depressive disorder recurrent episodes (MDDREC); and dysthymia are considered an important public health problem. The objective of this paper was to identify and correlate environmental factors in patients with MDDSE, MDDREC and dysthymia.

METHODS

121 patients from the Instituto Mexicano del Seguro Social's Subzone General Hospital of San Andres Tuxtla, at Veracruz, were questioned by history with the risk variables.

RESULTS

16 of them were diagnosed with MDDREC, 72 with MDD and 33 with dysthymia; in all of those cases, females prevailed. Depressive disorders were observed more frequently in people over 40 years, married, with medium or low educational level, with dysfunctional family environment, victims of family violence and who were the middle siblings. The main comorbidities that arose were gastrointestinal disorders, obesity and hypertension.

RESULTS

16 of them were diagnosed with MDDREC, 72 with MDD and 33 with dysthymia; in all of those cases, females prevailed. Depressive disorders were observed more frequently in people over 40 years, married, with medium or low educational level, with dysfunctional family environment, victims of family violence and who were the middle siblings. The main comorbidities that arose were gastrointestinal disorders, obesity and hypertension.

CONCLUSIONS

The main risk factors identified for developing depressive disorders were: being female, over 40 years old and being married. The differences obtained in this study, if it is compared with others, are probably due to sample size, selection criteria and ethnic origin.

MLH1 and XRCC1 polymorphisms in Mexican patients with colorectal cancer

DNA repair proteins maintain DNA integrity; polymorphisms in genes coding for these proteins can increase susceptibility to colorectal cancer (CRC) development. We analyzed a possible association of MLH1 -93G>A and 655A>G and XRCC1 Arg194Trp and Arg399Gln polymorphisms with CRC in Mexican patients. Genomic DNA samples were obtained from peripheral blood of 108 individuals with CRC (study group) at diagnosis and 120 blood donors (control group) from Western Mexico; both groups were mestizos. The polymorphisms were detected by PCR-RFLP. Association was estimated by calculating the odds ratio (OR). We found that the MLH1 and XRCC1 polymorphisms were in Hardy- Weinberg equilibrium. The MLH1 655A>G polymorphism in the 655G allele was associated with a 2-fold increase risk for CRC (OR = 2.04 and 95% confidence interval (95%CI) = 1.12-3.69; P < 0.01), while the MLH1 -93G>A polymorphism allele was associated with a protective effect (OR = 0.60, 95%CI = 0.40-0.89; P = 0.01 in the -93A allele and OR = 0.32, 95%CI = 0.13-0.79; P = 0.01 in the AA genotype). The XRCC1 Arg194Trp and Arg399Gln polymorphisms did not show any significant associations. In conclusion, we found that MLH1 -93G>A and 655A>G polymorphisms are associated with CRC in Mexican patients.

Association of a serotonin transporter gene (SLC6A4) 5-HTTLPR polymorphism with body mass index categories but not type 2 diabetes mellitus in Mexicans

The serotonergic system has been hypothesized to contribute to the biological susceptibility to type 2 diabetes mellitus (T2DM) and body-mass index (BMI) categories. We investigate a possible association of 5-HTTLPR polymorphism (L and S alleles) in the promoter region of the serotonin transporter gene (SLC6A4) with the development of T2DM and/or higher BMI by analyzing a sample of 138 individuals diagnosed with T2DM and 172 unrelated controls from the Mexican general population. In the total sample genotypes were distributed according to Hardy-Weinberg equilibrium, and S allele frequency was 0.58. There was no statistical association between 5-HTTLPR polymorphism and the development of T2DM in this Mexican population sample (p = 0.12). Nevertheless, logistic regression analysis of the L allele and increased BMI disclosed an association, after adjusting for age, sex and T2DM (p = 0.02, OR 1.74, 95% CI: 1.079–2.808).

MTHFR C677T, MTHFR A1298C, and OPG A163G polymorphisms in Mexican patients with rheumatoid arthritis and osteoporosis

MTHFR polymorphisms C677T and A1298C are associated with reduced MTHFR enzyme activity and hyperhomocysteinemia, which has been associated with osteoporosis. The A163G polymorphism in osteoprotegerin (OPG) has been studied in osteoporosis with controversial results. The objective of the present study was to investigate the association(s) among MTHFR C677T, MTHFR A1298C, and OPG A163G polymorphisms in Mexican patients with rheumatoid arthritis and osteoporosis. The femoral neck and lumbar spine bone mineral densities (BMDs) were measured in 71 RA patients, and genotyping for the three polymorphisms was performed via restriction fragment length polymorphism analysis. Patients with osteoporosis/osteopenia exhibited statistically significant differences in the genotype frequencies of MTHFR C677T as well as an association with femoral neck BMD; TT homozygotes had lower BMDs than patients with the CT genotype, and both of these groups had lower BMDs than patients with the CC genotype. The associations of the MTHFR C677T polymorphism with osteoporosis/osteopenia and femoral neck BMD suggest that these polymorphisms confer a risk of developing osteoporosis in patients with rheumatoid arthritis, a risk that may be reduced with folate and B complex supplementation.

XRCC1 polymorphisms and haplotypes in Mexican patients with acute lymphoblastic leukemia

We examined the influence of the Arg194Trp, Arg280His, and Arg399Gln polymorphisms of XRCC1 (X-ray repair cross-complementing group 1) on the development of childhood acute lymphoblastic leukemia (ALL) in 120 ALL patients and 120 controls in Mexico. All of them were genotyped for these polymorphisms, using polymerase chain reaction. No significant differences in allele and genotype frequencies for any polymorphism were observed between patients and controls. Estimation of haplotypes showed the eight expected haplotypes (A-H), seven of which were found in both patients and controls; haplotype A (Arg-Arg-Arg) was the most common, whereas haplotypes F and G were absent in patients and controls, respectively. Haplotype B (Trp-Arg-Arg) was found to be associated with an increased risk of ALL (odds ratio (OR) = 1.95, 95% confidence interval (CI) = 1.13-3.37; P = 0.016), particularly in males (OR = 2.65, 95%CI = 1.25-5.63; P = 0.01). Individually, the 194Trp, 280His, and 399Gln alleles were not associated with significantly increased risk for ALL in these Mexican children.

[Non-syndromic cleft lip/cleft palate and C677T methylene-tetrahydrofolate reductase variant in Mexican children]

BACKGROUND

Non-syndromic cleft lip with or without cleft palate (NSCLP) is a common malformation. The aetiology is multifactorial. An incidence of 1.1-1.39 per 1000 new births had been reported in Mexico. The folic acid intake in preconceptional stage has been reported to prevent malformations such as neural tube defects (NTD) and NSCLP. The C677T variant of the methylene-tetrahydrofolate reductase (MTHFR) gene is responsible of a thermolabile form, related to decrease of folate and increase homocysteine. This variant has been associated with CLP, in different populations, but results are still controversial. Our objective was to determine the allelic (AF) and genotypic frequency (GF) of the MTHFR-C677T variant in Mexican children with NSCLP.

METHODS

Transverse comparative study in 67 Mexican children with NSCLP and a control group with 70 unrelated Mexican individuals without NSCLP.

RESULTS

The AF in NSCLP was 39 %. There was no statistical difference between AF in the two groups (39 versus 41).

CONCLUSIONS

In this population, genotype C677T was not a major risk factor for this malformation, however, sample size, other genes implicated and genes-environment interactions must be considered.

MDR1 C3435T polymorphism in Mexican children with acute lymphoblastic leukemia and in healthy individuals

To determine the influence of the MDR1 C3435T polymorphism on the development of childhood acute lymphoblastic leukemia (ALL), we studied 107 children with ALL and 111 healthy subjects. All subjects were genotyped for the C3435T polymorphism using the polymerase chain reaction-restriction fragment length polymorphism method. The genotype frequencies in the patients were 17% homozygous CC, 61% heterozygous CT, and 22% homozygous TT; in healthy individuals the genotype frequencies were 14% CC, 53% CT, and 33% TT. In patients with ALL the allele frequencies were 0.47 for the C allele and 0.53 for the T allele; in the healthy group these allele frequencies were 0.40 and 0.60 for the C and T alleles, respectively. No significant differences in allele frequency (p > 0.176) and genotype frequency (p > 0.255) were detected between the two groups. These findings suggest that the CT or TT genotype does not increase the risk for childhood ALL in Mexican patients. On the other hand, significant differences in allele frequencies were detected in the comparison of Mexican healthy subjects with other populations. Whether these differences are fortuitous or related to diverse genetic backgrounds remains to be elucidated.

[Mutations in the arginine vasopressin neurophysin-II gene in familial neurohypophyseal diabetes insipidus patients]

Neurogenic diabetes insipidus (NDI) is a rare condition characterized by polyuria and polydipsia caused by deficient arginine vasopressin hormone production. More than a 50 mutations have been identified for familial autosomic dominant neurogenic diabetes insipidus (FadNDI). These mutations can cause citotoxicity and lead to the degeneration of magnocellular neurons of the hipofisis by aberrant protein accumulation. The NDI diagnosis is based on the water deprivation test, quantification of AVP hormone and Magnetic Resonance Image (MRI), and in families with history of FadNDI has been suggested the molecular analysis of mutation in the arginine vasopressin neurophisin II gene before the signs and symptoms development, with the purpose of offering a suitable diagnosis, clinical follow up and treatment. The treatment with a synthetic analogue of AVP hormone allows the remission of the signs and symptoms in NDI patients and the advances in gene therapy in animal models has been promising, as much for NDI as for other diseases in which the mutant protein production has been involved.

[Frequency of TS1494del6 polymorphism in colorectal patients from west of Mexico]

Thymidylate synthase (TYMS) converts dUMP to dTMP, the rate-limiting nucleotide in DNA synthesis. It is also the target for 5-flurouracil, the most common chemotherapy agent for treatment of colorectal cancer (CRC). We designed a case-control study to investigate the frequency of TS 1494del6 polymorphism in patients with CRC and controls from Mexican population. The study consists of 253 patients with CRC and 200 control subjects. Risk of CRC was estimated by use of Odds ratio (95% CI) analysis. The genotype 6bp-/6bp- in CRC patients was 18% (45/253) and in controls was 11% (22/200) with Odds ratio of 1.8 (1 - 4) with P = 0.059. When stratifying the training groups by age (< 50 years), male gender, stage III-IV and presence of metastasis, the genotype 6bp-/6bp- was as risk (p < 0.05). The genotype 6bp-/6bp- in the region untranslated 3' of TS gene, in the analyzed sample participates in important way in the development of CRC of the Mexican population.

Cytochrome P4501A1 polymorphism is associated with susceptibility to acute lymphoblastic leukemia in adult Mexican patients

We studied the role of cytochrome P4501A1 (CYP1A1 Val/Val) genotypes in the etiology of acute lymphoblastic leukemia (ALL) in adult Mexican patients. Distributions of CYP1A1 Val/Val genotypes in peripheral blood DNA samples from 136 healthy controls and 136 adult patients with ALL were evaluated. There was an increased frequency of the CYP1A1 Val/Val genotype among ALL patients, showing a significant association between this genotype and the risk of developing ALL.