Single nucleotide polymorphism in PTEN-Long gene: A risk factor in chronic myeloid leukemia.

The BCR-ABL1 oncogene is associated with chronic myeloid leukemia (CML) pathogenesis, but the molecular mechanisms that initiate leukemogenesis are still unclear. Cancer pathogenesis has been associated with genetic alterations that may lead to inactivation of tumor suppressor genes. Phosphatase and tensin homolog (PTEN) is frequently deleted or inactivated in various tumors. A recently discovered variant of PTEN, PTEN-Long (PTEN-L), results from an alternative translation initiation site located upstream of the canonic AUG and generates a protein of 576 amino acids instead the expected protein of 403 amino acids. A 16 bp perfect palindromic motif centered on the PTEN-L CUG513 start codon is required for translation initiation. A single nucleotide polymorphism (SNP) of PTEN-L gene rs12573787 is located on the first exon respect to the CUG initiation site. In this case-control study we evaluated the association of genetic variants in PTEN-L with CML risk and therapy response in the Argentine population. The allele A of SNP rs12573787 was found to be associated with CML risk OR (95% CI) 1.71 (1.11-2.63) p = 0.016, which resulted consistent by multivariate analysis adjusted by gender and age. According to previous evidence that CML is more frequent in males, we found that the genetic risk of CML was confined to this gender. Unexpectedly, we also found this association confined to CML patients older than 45 years old. To our knowledge, this is the first time that PTEN-L rs1257378 was studied in CML suggesting that the variant A allele is a risk factor for CML development but, no association with the failure to TKIs treatment was found.

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.

High frequencies of telomeric associations, chromosome aberrations, and sister chromatid exchanges in ulcerative colitis.

OBJECTIVE: Chromosome instability provides a predisposing background to malignancy, contributing to the crucial genetic changes in multistep carcinogenesis. The aim of this work was to analyze chromosome instability in patients with ulcerative colitis (UC) to achieve a better understanding of the increased risk for colorectal cancer. METHODS: Peripheral blood lymphocyte cultures from 20 untreated UC patients and 24 controls were used to study chromosome instability by assessing telomeric associations (TAS), chromosome aberrations (CA), and sister chromatid exchanges (SCE). RESULTS: Mean frequencies of TAS and CA were significantly increased in UC patients compared to controls (p < 0.001). Chromosomes 10, 11, 21, 16, and 19 were the most frequently involved in TAS. A total of 104 CA clustered in 66 breakpoints could be exactly localized. Seven nonrandom bands significantly affected in UC patients were found (p < 0.004), showing a significant correlation with the location of cancer breakpoints (p < 0.003), particularly with colorectal carcinoma rearrangements. SCE analysis showed higher levels in patients compared to controls (p < 0.006), but no differences were observed in cell cycle kinetics. CONCLUSIONS: Our results demonstrate the presence of an unstable genome in UC patients that could be related to the cancer development observed in this disease.

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.

Expression of common fragile sites in two Ceboidea species: Saimiri boliviensis and Alouatta caraya (Primates: Platyrrhini).

Fragile sites are points of preferential breakage that may be involved in chromosome rearrangements. Induction of common fragile sites (c-fra) and spontaneous breakage were analyzed in two New World Monkeys species: Saimiri boliviensis (SBO) and Alouatta caraya (ACA). Spontaneous chromosome aberrations were analyzed on untreated lymphocyte cultures with Brögger's formula (1977). SBO presented a low level of spontaneous breakage, while higher frequencies were detected in ACA in which bands 1q23; 2q13 and 11q19 were significantly affected (p<0.01). The populational distribution of c-fra was analyzed by the Chi2 test in FUdR plus caffeine treated cultures. A total of 21 c-fra was identified in SBO and 24 in ACA. Fragile sites A1q33, B1p21, B4p14, C3q23 and C5q22 were identified in all analyzed SBO specimens. The most frequent c-fra identified in ACA specimens were 1q23, 1q31, 1q33, 2q22, 8q14, 12q31, 13q22, 14q15 and Xq22. Fragile sites A1q31, A1q33, B1q14, B3q13, B4q21 and Xq22 identified in SBO and 1q31, 1q33, 2q22, 4q21, 6q13, 13q22 and Xq22 from ACA were the most conserved sites. A low coincidence between the location of c-fra and that of heterochromatin and breakpoints involved in euchromatic rearrangements known for these genera, was established.

Spontaneous breakage and fragile site expression in chronic lymphocytic leukemia.

It has been suggested that genetic predisposition to cancer might be related to spontaneous chromosome instability or to fragile site expression. Therefore, spontaneous breakage and fragile sites were analyzed in nine untreated chronic lymphocytic leukemia (CLL) patients to determine their relation to cancer rearrangements. Five cases presented spontaneous gaps and breaks with a random distribution of breakpoints. In cultures treated with fluorodeoxyuridine or aphidicolin, 29 specific bands could be defined as fragile sites. A significant clustering of these sites was found with known common fragile sites (c-fra) and cancer breakpoints described in the literature. Most of these cancer breakpoints were involved in structural abnormalities associated with CLL (p < 0.00001). These data suggest that the expression of specific fragile sites might be related to structural chromosomal aberrations in CLL.

Chromosome instability in untreated adult celiac disease patients.

Spontaneous chromosome aberrations (CAs) and induced fragile sites (FSs) were analysed in 12 untreated adult coeliac disease (CD) patients and 8 healthy controls. Blood lymphocytes from each individual were cultured for 72 h at 37 degrees C in F-10 medium with 5% fetal calf serum and 0.1 ml phytohemagglutinine. FSs were induced by FudR (10 micrograms/ml, 24 h before harvesting) and caffeine (2.2 mM. 6 h before harvest). Spontaneous CAs and FSs were analysed on 30-50 Giemsa-stained and G-banded metaphases. The mean frequencies of spontaneous CAs (abnormal cells, gaps/cell and breaks/cell) of CD patients (0.24 +/- 0.02, 0.21 +/- 0.02 and 0.13 +/- 0.02, respectively) were significantly higher than those of controls (0.04 +/- 0.01, 0.02 +/- 0.01 and 0.02 +/- 0.01, respectively) (p < 0.001). Fourteen spontaneous CAs and 5 FSs specific for CD patients presented a strong coincidence (70%) with bands involved in T- and B-cell malignant lymphoma rearrangements. These findings suggest that CD has chromosome instability affecting specific points that could be related to the high prevalence of malignancies in this disorder.

[Participation of fragile sites in cancer]. / Participación de los sitios frágiles en cáncer.

Structural and numerical chromosomal abnormalities are frequent findings in neoplastic cells. The origin of structural rearrangements is probably due to the existence of specific labile areas on human chromosomes. These areas, named fragile sites (FS), are prone to chromosomal breakage and rearrangements, playing an important role in the first steps of carcinogenesis. The classification of FS, the mechanisms involved in FS induction and their biological significance, specially their relationship with cancer development, are discussed.

Non-random distribution of spontaneous chromosome aberrations in two Bloom Syndrome patients.

The distribution of breakpoints involved in spontaneous chromosome aberrations (CA) was analyzed in lymphocytes from a family with Bloom's Syndrome (BS) and 9 healthy individuals. Standard and G-banded metaphases from each individual were analyzed to allow the identification of the breakpoints involved in spontaneously occurring chromosome aberrations. A total of 85 breakpoints in BS patients, 17 in their parents and 35 in controls, could be exactly localized to specific chromosome bands. Breakpoint distribution was statistically analyzed considering the formula proposed by Brøgger (1977), showing a non-random pattern in BS patients. Thirteen bands non-randomly involved in spontaneous CA (p < 0.005) were recognized in BS, located at 1p36, 1q21, 1q32, 2q33, 3p24, 3p14, 3q27, 5q31, 6p21, 7q22, 9q13, 11q13, and 17q23. Only 1 band (1q21) was significantly implicated in both parents (p < 0.005), while controls showed a random distribution. BS non-random bands were correlated with the chromosomal location of fragile sites, oncogenes, and breakpoints involved in cancer rearrangements. A significant correlation with the location of fragile sites and cancer-breakpoints (p < 0.005), particularly with acute myeloid leukemia and malignant lymphomas rearrangements was found. These findings demonstrate that constitutional chromosome instability in BS might involve specific points, such as fragile sites and cancer breakpoints, suggesting an association with the increased incidence of cancer.

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.

Spontaneous chromosome aberrations in Fanconi's anemia patients are located at fragile sites and acute myeloid leukemia breakpoints.

Spontaneous chromosome aberrations (CA) were analyzed in 3 Fanconi's anemia (FA) patients, 8 family members, and 9 healthy individuals. Peripheral blood lymphocytes obtained from each individual were cultured and cytogenetic analysis was performed on standard and sequential G-banded metaphases. The numbers of abnormal cells and breaks were found to be higher in AF patients compared to the other groups (p < 0.0001). Breakpoint distribution was statistically analyzed considering the formula proposed by Brøgger (1977), showing a non-random pattern among FA patients but not among controls or relatives (p < 0.001). Five chromosomal bands located at 1p36, 1p22, 1q21, 3p14, and 3q21 were non-randomly involved in spontaneous CA in FA patients. These bands were correlated with the chromosomal location of fragile sites, oncogenes, and breakpoints involved in cancer-rearrangements. A significant correlation with the location of fragile sites (p < 0.03) and breakpoints involved in cancer-rearrangements (p < 0.001), particularly with AML chromosome anomalies (p < 0.03) was found, suggesting a possible relationship with the high predisposition to cancer observed in this disease.

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)