Andrés López-Cortés

Genetic polymorphisms in MTHFR (C677T, A1298C), MTR (A2756G) and MTRR (A66G) genes associated with pathological characteristics of prostate cancer in the Ecuadorian population.

Introduction:The methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR) and MTR reductase (MTRR) enzymes act in the folate metabolism, which is essential in methylation and synthesis of nucleic acids. The single nucleotide polymorphisms, MTHFR C677T, A1298C, MTR A2756G and MTRR A66G, cause alteration in the homocysteine levels and reduced enzymatic activity that generates deficiency in the assimilation of folates associated with DNA damage; that is, why it is important to know if the single nucleotide polymorphisms are associated with the pathological characteristics and development of prostate cancer, through a case-control retrospective study. Methods:DNA was extracted from 110 healthy and 104 affected men. The genotypes were determined by means of the polymerase chain reaction-restriction fragment length polymorphism and confirmed with genomic sequencing. Results:We found significant association between the genotypes of the MTHFR C677T polymorphism: C/T (odds ratio [OR] = 2.2; 95% confidence interval [CI] = 1.3–3.9; P = 0.008) and C/T + T/T (OR = 2.2; 95% CI = 1.3–3.9; P = 0.009) with the risk of prostate cancer development, and a slight association with MTRR A66G. Regarding pathological characteristics, we found significant risk between the C/T + T/T genotypes and the Gleason score (7–10) of poorly differentiated carcinoma (OR = 5.2; 95% CI = 1.7–16.2; P = 0.007). On the other hand, a significant association between A1298C, A66G, and A2756G with the pathological characteristics was not found (P > 0.05). Conclusions:The MTHFR C677T polymorphism has significant effects on susceptibility to prostate cancer in Ecuadorian population, especially with the Gleason grade.

Genetic Polymorphisms in Apolipoprotein E and Glutathione Peroxidase 1 Genes in the Ecuadorian Population Affected With Alzheimer’s Disease

Introduction:The main objective of this study is to determine the prevalence of apolipoprotein E (Apo E) and glutathione peroxidase 1 (GPX1) polymorphisms and their influence on the development of Alzheimer disease (AD) in the Ecuadorian population. Methods:The authors performed an analytic transversal case-control study. The study group (n = 39) consisted of patients with AD and dementia. The control group (n = 39) comprised elderly adults who have not been diagnosed with dementia and have the same age and education as the study group. Their inclusion period was from 2007 to 2008. Later on, after obtaining informed consent and after finishing a structural interview; the next step forward was to collect blood and extract DNA by standardized protocols. Besides, the authors performed polymerase chain reaction-restriction fragment length polymorphism technique to determine the genotype of each individual. Results:The authors found a positive association between ϵ4 and ϵ2 alleles of Apo E. The GPX1 gene shows an association of leu allele, whereas pro allele shows a negative association. The odds ratio test shows no significant relative risk. Conclusions:Apo E is not a risk factor, nor a protective one for AD, whereas the leu allele of GPX1 is a possible risk factor for the disease.

Relationship of an hRAD54 gene polymorphism (2290 C/T) in an Ecuadorian population with chronic myelogenous leukemia

The hRAD54 gene is a key member of the RAD52 epistasis group involved in repair of double-strand breaks (DSB) by homologous recombination (HR). Thus, alterations of the normal function of these genes could generate genetic instability, shifting the normal process of the cell cycle, leading the cells to develop into cancer. In this work we analyzed exon 18 of the hRAD54 gene, which has been previously reported by our group to carry a silent polymorphism, 2290 C/T (Ala730Ala), associated to meningiomas. We performed a PCR-SSCP method to detect the polymorphism in 239 samples including leukemia and normal control population. The results revealed that the 2290 C/T polymorphism has frequencies of 0.1 for the leukemia and 0.1 for the control group. These frequencies show no statistical differences. Additionally, we dissected the leukemia group in chronic myelogenous leukemia (CML) and acute lymphoblastic leukemia (ALL) to evaluate the polymorphism. The frequencies found in these subgroups were 0.14 for CML and 0.05 for ALL. We found statistically significant differences between CML patients and the control group (p < 0.05) but we did not find significant differences between ALL and the control group (p > 0.05). These results suggest a possible link between the 2290 C/T polymorphism of the hRAD54 gene and CML.

Positive Association of the Cathepsin D Ala224Val Gene Polymorphism With the Risk of Alzheimer's Disease

Background:Alzheimers disease (AD) is the most common cause of senile dementia. In Ecuador, the number of deaths caused by AD increases each year. Epidemiologically, the Ecuadorian population is composed of a mixture of several genetic backgrounds along with environmental factors, that make it unique and ideal for population studies. The main objective of this study was to determine the prevalence of Cystatin C (CST3), Cathepsin D (CTSD) and Manganese superoxide dismutase (MnSOD) amino acid-altering polymorphisms and their influence on the development of AD in the Ecuadorian population. Methods:This is a case-control study consisting of 56 patients with AD, from the Department of Neurology at Carlos Andrade Marín Hospital. The control group (n = 55) comprised healthy elderly adults. The inclusion period was from January to August of 2012. Peripheral blood was collected from both groups for DNA extraction, polymerase chain reaction and capillary sequencing. Results:There was a positive association between a CTSD polymorphism (Ala224Val) and the development of AD (odds ratio = 8.1, 95% confidence interval: 0.9–85.7; P < 0.025). However, the 3 other polymorphisms investigated did not show significant associations with AD. Conclusions:Variations in CTSD and MnSOD showed no association with the development of AD, whereas the presence of the Ala224Val polymorphism in CTSD had a positive association with the development of AD.

Incidence of the L858R and G719S mutations of the epidermal growth factor receptor oncogene in an Ecuadorian population with lung cancer

The World Health Organization indicates that lung cancer (LC) represents the main cause of death in many developed countries. In Ecuador, according to the National Cancer Registry, LC is the fourth cause of death among malignant tumors, followed by gastric, pancreatic, and breast cancer [1]. Moreover, three provinces present the highest percentages of the disease d Guayas (32.8%), Pichincha (20.7%), and Manabı́ (7.5%) [1]. It is estimated that this tendency will increase in the next years, and would place this disease as the principal cause of death by neoplasia. Therefore, it is important to perform the first mutation research in relation to the tyrosine kinase domain (TKD) of the EGFR gene in Ecuador. The ERBB family is one of the receptor systems located in the cytoplasmatic membrane that presents intrinsic tyrosine kinase activity (TKA). The epidermal growth factor receptor (EGFR) is located in 7p12.1wp12.3 and encodes a precursor protein of 1,210 amino acids [2]. This integral membrane glycoprotein of 170 kDa is formed by the extracellular membrane receptor domain, the lipophilic transmembrane domain, and the intracellular domain [2]. The phosphorylation of the cytosolic TKD initializes the downstream of intracellular signal transduction that regulates cell proliferation, cell differentiation, and angiogenesis [3]. The somatic mutations of the EGFR gene are grouped in the ATP kinase domain. These precise mutations constitute one of the most common genetic anomalies found in this gene, due to the fact that these variants correlate themselves with the presence of oncogenic factors and apoptotic mechanisms [4]. The population studied consisted of 189 male and female Ecuadorians. A total of 80 tumor samples were obtained through the Department of Pathology at Hospital Carlos Andrade Marin, and the control group included 109 healthy volunteers who were selected randomly. Genotype was determined through the polymerase chain reaction restriction fragment length polymorphism technique. The SacI restriction enzyme (New England BioLabs, Ipswich, MA) was used to identify the presence of G719S, which consists of the exchange of glycine (G) for serine (S) in the 719 codon, while the Sau96I enzyme allows for the detection of L858R, which consists of the exchange of leucine (L) for arginine (R) in the 858 codon.

Frequency of GJB2 and del(GJB6-D13S1830) mutations among an Ecuadorian mestizo population.

OBJECTIVE The frequency of GJB2 mutations and of the del(GJB6-D13S1830) mutation has not been established among the Ecuadorian mestizo population diagnosed with autosomal recessive non-syndromic hearing loss. A genetic analysis was therefore designed in order to do so. METHODS The sample population included 111 subjects of which 26 were autosomal recessive non-syndromic hearing loss probands. Posterior to PCR amplification, sequencing analysis of exon 2 was used for mutational detection of the GJB2 gene; a multiplex PCR method was used for detection of the del(GJB6-D13S1830) mutation. The ratio of subjects with a certain state of the mutation (heterozygous/homozygous) is expressed as a percentage and significant differences between probands and controls were calculated using Fishers exact test; P<0.05 was considered significant. RESULTS A total of 104 mutations belonging to 8 allelic variations were identified. The most common being the V27I (58.9%); however, as this variation is a non-pathogenic polymorphism, Q7X, with a total of 19 mutated alleles, was the most frequent mutation (18.3%). The V27I polymorphism was the only variation distributed homogenously among probands and controls (P=0.351). Based on physical analyses of multiple patients we confirm that Q7X causes a non-syndromic form of hearing loss and propose that it is a possible predominant mutation in the Ecuadorian population. CONCLUSIONS This is the first study of its kind among the Ecuadorian population and a preliminary step in establishing GJB2 and del(GJB6-D13S1830) mutational frequencies in this population; it is also the first to report of such a high frequency of the Q7X mutation. The data presented here brings Ecuador a step closer to providing more efficient treatment for a broader number of patients; additionally, it contributes to a better understanding of the relationship between autosomal recessive non-syndromic hearing loss and mutations on the GJB2 gene.

Association of genetic variants of membrane receptors related to recognition and induction of immune response with Helicobacter pylori infection in Ecuadorian individuals.

Helicobacter pylori (Hp) has a worldwide distribution showing its higher prevalence of infection in developing countries. Toll‐like receptors (TLRs) and C‐type lectin receptors (CLRs) are proteins that recognize pathogen‐associated molecular patterns (PAMPs) and initiate an innate immune response by promoting growth and differentiation of specialized hematopoietic cells for host defense. Gastric infections led by Hp induce a Th‐1 cellular immune response, regulated mainly by the expression of IFN‐γ. In this retrospective case‐control study, we evaluated the TLR1 1805T/G, TLR2 2029C/T, TLR4 896A/G, CD209 ‐336A/G and IFNGR1 ‐56C/T polymorphisms and their relationship with susceptibility to Hp infection. TLR1 1805T/G showed statistical differences when the control (Hp‐) and infected (Hp+) groups (P = 0.041*) were compared; the TLR1 1805G allele had a protective effect towards infection (OR = 0.1; 95% CI = 0.01‐0.88, P = 0.033*). Similarly, the IFNGR1 ‐56C/T polymorphism showed statistical differences between Hp+ and Hp– (P = 0.018*), and the IFNGR1 ‐56TT genotype exhibited significant risk to Hp infection (OR = 2.9, 95% CI = 1.27‐6.54, P = 0.018*). In conclusion, the pro‐inflammatory TLR1 1805T and IFNGR1 ‐56T alleles are related with susceptibility to Hp infection in Ecuadorian individuals. The presence of these polymorphisms in individuals with chronic infection increases the risk of cellular damage and diminishes the cellular immune response efficiency towards colonizing agents.

A study of the molecular variants associated with lactase persistence in different Ecuadorian ethnic groups

Lactase persistence (LP) is an adaptive trait that certain human populations have acquired in response to lactose consumption in adulthood. The T‐13910 variant has been reported as a causal polymorphism in Europeans. The Ecuadorian population has been described as multicultural and multiethnic, comprised of three main ethnic groups (Mestizo, Native Amerindian, and Afro‐Ecuadorian). The aim of the study was to identify the molecular basis of LP in these admixed populations for the first time and determine the association between the T‐13910 marker and the European ancestry proportion of each ethnic group.