Paola E. Leone

NF2 gene mutations and allelic status of 1p, 14q and 22q in sporadic meningiomas

Formation of meningiomas and their progression to malignancy may be a multi-step process, implying accumulation of genetic mutations at specific loci. To determine the relationship between early NF2 gene inactivation and the molecular mechanisms that may contribute to meningioma tumor progression, we have performed deletion mapping analysis at chromosomes 1, 14 and 22 in a series of 81 sporadic meningiomas (54 grade I (typical), 25 grade II (atypical) and two grade III (anaplastic)), which were also studied for NF2 gene mutations. Single-strand conformational polymorphism analysis was used to identify 11 mutations in five of the eight exons of the NF2 gene studied. All 11 tumors displayed loss of heterozygosity (LOH) for chromosome 22 markers; this anomaly was also detected in 33 additional tumors. Twenty-nine and 23 cases were characterized by LOH at 1p and 14q, respectively, mostly corresponding to aggressive tumors that also generally displayed LOH 22. All three alterations were detected in association in seven grade II and two grade III meningiomas, corroborating the hypothesis that the formation of aggressive meningiomas follows a multi-step tumor progression model.

Cytogenetic monitoring in a population occupationally exposed to pesticides in Ecuador.

We analyzed the incidence of structural and numerical chromosomal aberrations (CAs) in workers of a plantation of flowers located in Quito, Ecuador, in South America. This study included 41 individuals occupationally exposed to 27 pesticides, some of which are restricted in many countries and are classified as extremely toxic by the World Health Organization; among these are aldicarb and fenamiphos. The same number of individuals of the same age, sex, and geographic area were selected as controls. Workers exposed to these pesticides showed an increased frequency of CA compared with control group (20.59% vs. 2.73%; p < 0.001). We conclude that screening for CA is an adequate biomarker for evaluating and detecting genotoxicity resulting from exposure to pesticides. Levels of erythrocyte acetylcholinesterase were also determined as a complementary metabolic study. Levels below the optimal (> 28 U/mL blood) were found in 88% of exposed individuals; this clearly shows the effect of organophosphate pesticides. When comparing the levels of acetylcholinesterase and structural CA frequencies, there was a negative linear correlation (r = 0.416; p < 0.01). We conclude that by using both analyses it may be possible to estimate damage produced by exposure to organophosphate pesticides.

Should gaps be included in chromosomal aberration analysis? Evidence based on the comet assay

This study evaluated DNA damage in human lymphocytes due to occupational exposure to low levels of ionizing radiation using two assays: the comet assay and chromosomal aberration (CA) analysis including and excluding gaps. The results obtained reveal a higher correlation between both methods when chromatid and chromosome gaps were included in the correlation analysis (r=0.78 versus r=0.50). This increased correlation support the hypothesis that the gaps constitute a type of chromosome aberration, and suggest that these events should be scored in this type of analysis.

Search for mutations of the hRAD54 gene in sporadic meningiomas with deletion at 1p32.

The hRAD54 gene is related to a family of genes involved in DNA recombination and repair and encodes a protein with DNA helicase activity. hRAD54 has been mapped to 1p32, a region frequently involved in deletions in a variety of tumor types, including atypical and anaplastic meningiomas. To determine whether alterations of hRAD54 are a common event in meningeal tumors, by means of polymerase chain reaction–single‐stranded conformation analysis we examined 29 tumor samples characterized by 1p deletions for hRAD54 mutations. Although 18 tumors displayed allelic loss at the gene region (1p32) as determined by microsatellite marker analysis, the sole coding‐sequence alteration detected corresponded to a T → C transition, with no amino‐acid change. The genotype distribution was 10.34% TT, 44.8% TC, and 44.8% CC, whereas in the normal controls it was 3.77% TT, 13.2% TC, and 83.01% CC, and most meningiomas with 1p32 deletion retained allele C. Another polymorphism due to a T → C change was evidenced at nt 3008, in the 3′ untranslated region. This change was evidenced in all cases we sequenced. These results appear to exclude the involvement of the hRAD54 gene in the pathogenesis of the nontypical meningiomas, although a detrimental effect of the hRAD54 polymorphisms cannot be ruled out. Mol. Carcinog. 24:300–304, 1999.

Evaluation of DNA damage in an Ecuadorian population exposed to glyphosate

We analyzed the consequences of aerial spraying with glyphosate added to a surfactant solution in the northern part of Ecuador. A total of 24 exposed and 21 unexposed control individuals were investigated using the comet assay. The results showed a higher degree of DNA damage in the exposed group (comet length = 35.5 µm) compared to the control group (comet length = 25.94 µm). These results suggest that in the formulation used during aerial spraying glyphosate had a genotoxic effect on the exposed individuals.

A polymorphism in the hMSH2 gene (gIVS12-6T>C) associated with non-Hodgkin lymphomas

DNA common variants may significantly contribute to genetic risk for common diseases. Because of its biological function in DNA repair, hMSH2 gene polymorphisms are candidates for influencing cancer susceptibility and overall genetic stability. Twenty-two individuals with non-Hodgkin lymphomas (NHL) and 50 normal individuals were screened for polymorphic variants in exon 13 of the hMSH2 mismatch repair gene in order to determine if there is any association with development of lymphomas. The polymorphism screening was carried out by single strand conformation polymorphism analysis and DNA sequencing. We found a single nucleotide polymorphism: a T to C substitution at the -6 intronic splice acceptor site of exon 13 (gIVS12-6T>C). This polymorphism was present in 7.5% of normal individuals (allele frequency = 0.05) and in 22.73% of lymphomas (allele frequency = 0.11) (P<0.01). These results suggest that the polymorphism may be associated with an increased risk to develop NHL and that probably there are differences in the effect of the polymorphisms among populations.

Follow up study of chromosome aberrations in lymphocytes in hospital workers occupationally exposed to low levels of ionizing radiation

In the present study we analyzed and followed up on the cytogenetic effects of low levels of ionizing X-radiation on hospital workers at 72 h cultures. Samples of peripheral blood were collected from 10 hospital workers exposed to 1.84 mSv/year, and from 10 non exposed individuals, who were screened simultaneously and used as controls. The chromosomes were prepared using standard techniques. After 12 months, we undertook a second evaluation, this time with exposure to the same workers of 1.67 mSv/year. We observed 100 metaphases per subject, and there was a high percentage of altered metaphases (29.2% in the first sample and 26% in the second samples) The chromosome analysis in the second mitotic division, show aberrations such as gaps, breaks and acentric fragments, as well as other alterations such as dicentrics and rings, as well as chromosome variants (double minutes) in the exposed workers vs. the controls, and the difference was statistically highly significant (p < 0.001). There is no statistically significant difference between the first sample of exposed workers with the second one (p > 0.05). The findings in this study are interesting, because the workers were exposed to doses well below the accepted standards for exposure to radiations. Because of these unusual findings, our results could have potentially major consequences on our views on standards of exposure to radiation.

BCR-ABL rearrangement frequencies in chronic myeloid leukemia and acute lymphoblastic leukemia in Ecuador, South America.

Different BCR-ABL transcript variants occur more or less frequently, according to the leukemia type. We report the frequencies of BCR-ABL transcript variants studied in chronic myeloid leukemia (CML) and acute lymphoblastic leukemia (ALL) patients in the Ecuadorian population. The frequencies found for CML patients in this study were 94.6% for the b2/a2 rearrangement and 5.4% for the b3/a2 rearrangement; whereas in ALL, all cases (100%) that presented the BCR-ABL rearrangement had the e1/a2 junction. Since our results differ from the frequencies previously reported, we suggest that this may be due to a different genetic background in the population involved in this study when compared to the populations analyzed in prior studies. Furthermore, we recommend a survey of the BCR-ABL transcript variants and their frequencies in different ethnic groups.

Analysis of HFE gene mutations (C282Y, H63D, and S65C) in the Ecuadorian population.

Type 1 hemochromatosis is a disorder of iron metabolism mostly related to the HFE gene mutations. In the present study, we performed a mutation analysis to determine the frequencies of the HFE gene mutations (C282Y, H63D, and S65C) in DNA samples of 100 healthy Ecuadorian individuals. We used the polymerase chain reaction (PCR) to amplify exons 2 and 4 of the HFE gene and then the restriction fragment length polymorphism (RFLP) method to detect the mutations. The results revealed that the mutations in the normal Ecuadorian population have frequencies of 0.0, 0.035, and 0.04 for C282Y, H63D, and S65C, respectively. We also searched for these mutations in 12 hemochromatosis patients, and the frequencies that we found were 0.0 for C282Y, 0.167 for H63D, and 0.042 for S65C. We found differences [using the chi-square (χ2) test] in the frequency of the H63D mutation between the control group and the group of hemochromatosis patients (p<0.01). This suggests that in Ecuador, type 1 hemochromatosis is more influenced by the H63D mutation than the other two mutations that we analyzed. Given that in a Caucasian population hereditary hemochromatosis is mostly related to the C282Y mutation, it is possible that the findings for the Ecuadorian population are due to geographical differences between the populations.

The ?F508 mutation in Ecuador, South America

There are few reports about the incidence of the ΔF508 mutation in Latin American countries. We show the study of the ΔF508 mutation and the seven most common “European” mutations in 10 Ecuadorian CF affecteds. The incidence of ΔF508 mutation found was 25% and none of the other seven was detected in our population, which indicates that at least 60% of the mutations in the studied population are different from most common in Europe. Similar data have been reported in other Amerindian populations, therefore it is suggested that Cystic Fibrosis in Ecuador—and other Amerindian countries in Latin America—have a different ethiology than that of Caucasian populations. Hum Mutat 14:348–350, 1999.