Polymorphic variants of GSTM1, GSTT1, and GSTP1 genes in childhood acute leukemias: A preliminary study in Argentina.

BACKGROUND AND AIM: Despite recent major advances in leukemia research, the etiopathogenesis of childhood leukemias remains far elusive. Individual predisposing factors, including polymorphisms in detoxification enzymes, have been implicated in the molecular pathogenesis and heterogeneity of the disease. Genetic polymorphisms of glutathione S-transferases (GSTs) that alter enzyme activity could be an additional factor that increases the risk of acute leukemia, but data are lacking in Argentina. We assessed the association of GST polymorphisms and the susceptibility to childhood leukemia in Argentina by conducting an exploratory case-control study and correlated patients' genotype to clinical and biological features. METHODS: Deletion polymorphisms in GSTM1 and GSTT1 genes and the single nucleotide polymorphism in GSTP1 c.313A>G (rs1695; p.105Ile>Val) were genotyped by PCR-RFLP in 36 patients and 133 healthy individuals. RESULTS: GSTM1-null genotype was associated with a lower risk of developing acute leukemia (P = 0.013; OR: 0.31; CI: 0.12-0.80), while GSTP1-GG variants displayed an increased risk (P = 0.01; OR: 3.9; CI: 1.85-8.2). However, no differences were found for GSTT1 gene. Conclusion These preliminary results, to be validated in a larger population from Argentina, suggest that the development of pediatric leukemia may be differentially influenced by polymorphic variants in GST genes.

Evidence of chromosome instability in chronic pancreatitis.

In the current study we analyzed chromosome instability on peripheral blood lymphocytes cultured from 7 untreated patients with chronic pancreatitis (CP) by assessing telomeric associations (TAS), chromosome aberrations (CA) and sister chromatid exchanges (SCE). Seven healthy individuals were also analyzed. Mean frequencies of TAS were significantly higher in CP patients (X +/- SE: 11.00 +/- 2.37) compared to controls (1.00 +/- 0.30) (p<0.001). Chromosomes preferentially involved in TAS were: 9, 20, 16 and 21, being the most affected arms: 9p, 20q, 16p, 9q and 21q. All these terminal bands were coincident with cancer breakpoints (p<0.03), two of them (40%) were specifically associated to pancreatic carcinoma rearrangements. Three bands (60%) were coincident with oncogene location. The mean frequency of CA was significantly higher in patients (3.88 +/- 0.80) compared to controls (0.63 +/- 0.49) (p<0.001). Chromosomes 1, 2 and 13 were the most damaged. No specifically affected breakpoints were found. SCE analysis showed higher levels in patients (8.33 +/- 0.70) than in controls (6.62 +/- 0.34) (p<0.025), but no differences were observed in cell cycle kinetics. Our results clearly indicate that CP patients exhibit chromosome instability, showing the presence of an unstable genome that could be related to the cancer development observed in this disease.

Chromosome instability in lymphocytes from patients with celiac disease.

Cytogenetic studies were performed in celiac disease (CD) patients to determine if the presence of chromosome instability is related to the predisposition to cancer. Chromosome aberrations (CA) and sister chromatid exchange (SCE) frequencies in peripheral blood lymphocyte cultures from untreated CD patients and healthy controls were analyzed. Patients showed aberrations in 23% of cells, while only 3% were detected in the control group (p < 0.0001). The mean frequencies of gaps, breaks and total CA were found to be higher in CD patients compared to controls (p < 0.0001). Breakpoint distribution was nonrandom among chromosomes from celiac patients (p = 0.01), but not among controls (p = 0.04). The frequency of SCE/cell showed a mean value of 6.9 +/- 0.6 in CD patients and 7.3 +/- 0.2 in controls. No statistical differences were found. Breakpoints involved in CD patients presented a strong coincidence with the location of fragile sites (78.6%) and sites of cancer chromosome rearrangements (57.1%), most of them (75%) associated with malignant non-Hodgkin lymphomas. These results suggest that CD is a condition with increased chromosome instability characterized by a high level of CA and normal SCE frequencies, probably related to the increased incidence of cancer.

Increased expression of 5q31 fragile site in a Bloom syndrome family.

In this work, we report spontaneous chromosomal breakpoints and fragile site expression induced by 5-fluorodeoxyuridine (FdUrd) and FdUrd plus caffeine in a family with Bloom's syndrome (BS) and 2 healthy donors. Standard and G-banded metaphases from each individual and each treatment were analyzed. Among the 59 common fragile sites (c-fra) identified in this work, only the frequency of 5q31 was significantly increased in the BS family with respect to healthy donors (P less than 0.005). A remarkable coincidence between the breakpoints involved in spontaneous chromosome aberrations and induced c-fra was found in BS homozygote patients. The importance of the interaction between fragile sites and chromosome rearrangements in cancer is discussed.

[Induction of fragile sites by chemical and physical agents]. / Inducción de sitios frágiles por agentes químicos y físicos.

Many human malignancies are thought to be caused in large part by environmental agents. Studies indicate that ionizing radiation and many chemical mutagens/carcinogens appear to induce chromosomal mutations. Recently, it was suggested that chromosome aberrations (CA) might be produced by breakage at specific chromosomal points known as fragile sites (FS). FS induced by different chemical agents has been widely analyzed in lymphocytes cultures, but very little is known of the environmental factors that may influence on FS expression. No studies exist about FS expression induced with X-rays or about the interaction between radiation and chemical FS inducers. In this work FS expression induced by X-rays and 3 known FS inducers such as: BUDR, FUDR and aphidicolin, is analyzed. It was found that 17 chromosomal bands were significantly damaged (p < 0.001), thus being defined as FS. FS 3p14 and 16q23 were the more frequently observed. CA and FS levels from cultures exposed to X-rays and to FUDR plus X-rays were significantly increased (p < 0.01), suggesting that it would be convenient to use other radiosensitizer. These results suggest that FS could be induced by environmental factors such as chemical or physical agents. Finally, the correlation between FS and radiation induced CA, cancer CA and oncogene localization was established, showing the importance of the interaction between FS, CA and oncogenes in cancer development.

Inducción de sitios frágiles por agentes químicos y físicos. / [Induction of fragile sites by chemical and physical agents]

Many human malignancies are thought to be caused in large part by environmental agents. Studies indicate that ionizing radiation and many chemical mutagens/carcinogens appear to induce chromosomal mutations. Recently, it was suggested that chromosome aberrations (CA) might be produced by breakage at specific chromosomal points known as fragile sites (FS). FS induced by different chemical agents has been widely analyzed in lymphocytes cultures, but very little is known of the environmental factors that may influence on FS expression. No studies exist about FS expression induced with X-rays or about the interaction between radiation and chemical FS inducers. In this work FS expression induced by X-rays and 3 known FS inducers such as: BUDR, FUDR and aphidicolin, is analyzed. It was found that 17 chromosomal bands were significantly damaged (p < 0.001), thus being defined as FS. FS 3p14 and 16q23 were the more frequently observed. CA and FS levels from cultures exposed to X-rays and to FUDR plus X-rays were significantly increased (p < 0.01), suggesting that it would be convenient to use other radiosensitizer. These results suggest that FS could be induced by environmental factors such as chemical or physical agents. Finally, the correlation between FS and radiation induced CA, cancer CA and oncogene localization was established, showing the importance of the interaction between FS, CA and oncogenes in cancer development.

Inducción de sitios frágiles por agentes químicos y físicos. / [Induction of fragile sites by chemical and physical agents]

Many human malignancies are thought to be caused in large part by environmental agents. Studies indicate that ionizing radiation and many chemical mutagens/carcinogens appear to induce chromosomal mutations. Recently, it was suggested that chromosome aberrations (CA) might be produced by breakage at specific chromosomal points known as fragile sites (FS). FS induced by different chemical agents has been widely analyzed in lymphocytes cultures, but very little is known of the environmental factors that may influence on FS expression. No studies exist about FS expression induced with X-rays or about the interaction between radiation and chemical FS inducers. In this work FS expression induced by X-rays and 3 known FS inducers such as: BUDR, FUDR and aphidicolin, is analyzed. It was found that 17 chromosomal bands were significantly damaged (p < 0.001), thus being defined as FS. FS 3p14 and 16q23 were the more frequently observed. CA and FS levels from cultures exposed to X-rays and to FUDR plus X-rays were significantly increased (p < 0.01), suggesting that it would be convenient to use other radiosensitizer. These results suggest that FS could be induced by environmental factors such as chemical or physical agents. Finally, the correlation between FS and radiation induced CA, cancer CA and oncogene localization was established, showing the importance of the interaction between FS, CA and oncogenes in cancer development.

[Expression of new fragile sites detected in lymphoproliferative processes]. / Expresión de sitios frágiles nuevos detectados en procesos linfoproliferativos.

Fragile sites are specific chromosomal sites prone to breakage and rearrangements and they are probably related with cancer development. Fragile sites expression induced by 5-fluorodeoxyuridine (FudR) or 5-bromodeoxyuridine (BrdU) was analyzed in 4 healthy individuals and 4 patients affected with lymphoproliferative disorders: one Hodgkin's disease, one mycosis fungoides and two chronic lymphoproliferative disorders. Three standard peripheral lymphocyte cultures with F-10 medium and 5% of fetal calf serum were set up for each individual. For fragile sites induction, 10 micrograms/mL FudR or 50 micrograms/mL BrdU were added 24 hr or 6 hr before harvest. Standard and sequential G banded metaphases were studied for each individual and treatment. Quantitative analysis showed a low incidence of acentric fragments, dicentric, tri- or quadriradials, while gaps and breaks were more frequently observed. Chromosome or chromatid type aberrations were compared, showing similar values in all non-treated cultures. Chromosome type aberrations were increased in patients and controls treated cultures. Patient cultures treated by FudR presented a threefold increase of chromosome type alterations respect to chromatid ones. Moreover, chromosome breaks showed a twofold increase in patient treated cultures respect to control ones. The high number of chromosome breaks detected in these cases could be associated with an increased chromosome instability in cancer patients. Twenty common fragile sites (c-fra) were identified with sequential G banding. Patients and controls individuals have expressed 14 c-fra. Eleven of them were induced, in different proportions, by both chemical agents, showing that fragile sites share a structural homology in DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Coincidence in fragile site expression with fluorodeoxyuridine and bromodeoxyuridine.

Fragile site expression induced by 10 micrograms/ml or 20 micrograms/ml fluorodeoxyuridine (FudR) and 25 micrograms/ml or 50 micrograms/ml bromodeoxyuridine (BrdU) was studied in lymphocyte cultures of six healthy individuals. A significant decrease in mitotic indexes in respect to control cultures was observed with both FudR concentrations used. The cells showing chromosome aberrations and the total number of cytogenetic alterations were significantly increased both in FudR (p less than 0.001) and BrdU (25 micrograms/ml) (p less than 0.05) treated cultures with respect to the control culture. A site showing a gap or a break was defined as fragile if it appeared in 1% of the cells analyzed and in at least three of the six individuals studied with the same culture treatment. Using these criteria, fragile sites 4q31, 5q15, 6p22, 7p13, 7q32, 13q21, and 14q24 were induced in different proportions by both chemical agents. Although these drugs act via different mechanisms, they both substitute for thymidine in DNA. Our findings suggest that FudR is a more potent common fragile site inducer than BrdU.