RESUMEN
Genome-wide association studies (GWAS) have identified several single nucleotide polymorphisms (SNPs) that mildly predict prostate cancer risk. These SNPs are local tagging markers for causal gene alterations. Consideration of candidate genes in the tagged regions would be facilitated by additional information on the particular pathomechanisms which contribute to the observed risk increase. In this study we test for an association of prostate cancer tagging SNPs with alterations in DNA repair capacity, a phenotype that is frequently involved in cancer predisposition. DNA repair capacity was assessed on blood lymphocytes from 128 healthy probands after ionizing irradiation. We used the micronucleus (MN) assay to determine the cellular DNA double-strand break repair capacity and flow cytometry to measure damage induced mitotic delay (MD). Probands were genotyped for a panel of 14 SNPs, each representing an independent prostate cancer risk locus previously identified by GWAS. Associations between germline variants and DNA repair capacity were found for the SNPs rs1512268 (8p21), rs6983267 (8q24) and rs10993994 (10q11). The most significant finding was an association of homozygous rs10993994 T-allele carriers with a lower MN frequency (p=0.0003) and also a decreased MD index (p=0.0353). Cells with prostate cancer risk alleles at rs10993994 seem to cope more efficiently with DNA double strand breaks (less MN) in a shorter time (decreased MD index). This intriguing finding imposes concern about the accuracy of repair, with respect to the cancer risk that is mediated by T genotypes. To date, MSMB (microseminoprotein ß) is favored as the causal gene at the 10q11 risk locus, since it was the first candidate gene known to be expressionally altered by rs10993994. Based on the present observation, candidate genes from the contexts of DNA repair and apoptosis may be more promising targets for expression studies with respect to the rs10993994 genotype.
Asunto(s)
Cromosomas Humanos Par 10/genética , Reparación del ADN/genética , Sitios Genéticos , Predisposición Genética a la Enfermedad , Neoplasias de la Próstata/genética , Adolescente , Adulto , Cromosomas Humanos Par 10/efectos de la radiación , Roturas del ADN de Doble Cadena , Femenino , Rayos gamma/efectos adversos , Estudio de Asociación del Genoma Completo , Humanos , Linfocitos/efectos de la radiación , Masculino , Pruebas de Micronúcleos , Índice Mitótico , Polimorfismo de Nucleótido Simple/genética , Adulto JovenRESUMEN
PURPOSE: To evaluate the chromosome symmetric or asymmetric rearrangement (CR) frequency for chromosome 10 compared to chromosomes 1 and 3 induced in vitro in human lymphocytes by low doses of X-rays. MATERIALS AND METHODS: Blood samples obtained from three young and healthy volunteers were irradiated in G0 with 0.25, 0.50 and 1 Gy X-rays. Chromosome painting analysis was used on preparations of peripheral lymphocytes for the identification of CR. RESULTS: It was found that radiation-induced CR levels were nonrandomly distributed among the three painted chromosomes. Chromosome 10 CR frequencies were significantly greater than those involving chromosomes 1 (at all the doses tested) or 3 (at 0.25 and 1 Gy), with frequency ratios ranging from 2.2 to 5.2. CONCLUSIONS: In comparison to chromosomes 1 and 3, chromosome 10 appeared to be involved in exchanging at a significantly greater extent than expected according to its DNA content.
Asunto(s)
Aberraciones Cromosómicas , Cromosomas Humanos Par 10/genética , Cromosomas Humanos Par 10/efectos de la radiación , Análisis de Varianza , Cromosomas Humanos Par 1/genética , Cromosomas Humanos Par 1/efectos de la radiación , Cromosomas Humanos Par 3/genética , Cromosomas Humanos Par 3/efectos de la radiación , Relación Dosis-Respuesta en la Radiación , Humanos , Hibridación Fluorescente in Situ , Linfocitos/efectos de la radiación , Masculino , Rayos XAsunto(s)
Aberraciones Cromosómicas , Cromosomas Humanos/efectos de la radiación , Daño del ADN , Proteínas de Drosophila , Neoplasias Inducidas por Radiación/genética , Diferenciación Celular , División Celular , Rotura Cromosómica , Inversión Cromosómica , Cromosomas Humanos/genética , Cromosomas Humanos/fisiología , Cromosomas Humanos Par 10/genética , Cromosomas Humanos Par 10/fisiología , Cromosomas Humanos Par 10/efectos de la radiación , Proteínas del Citoesqueleto , Humanos , Hibridación Fluorescente in Situ , Interfase , Proteínas/genética , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas c-ret , Proteínas Tirosina Quinasas Receptoras/genética , Glándula Tiroides/citología , Glándula Tiroides/efectos de la radiación , Neoplasias de la Tiroides/genéticaRESUMEN
The RET/PTC3 rearrangement is formed by fusion of the ELE1 and RET genes, and is highly prevalent in radiation-induced post-Chernobyl papillary thyroid carcinomas. We characterized the breakpoints in the ELE1 and RET genes in 12 post-Chernobyl pediatric papillary carcinomas with known RET/PTC3 rearrangement. We found that the breakpoints within each intron were distributed in a relatively random fashion, except for clustering in the Alu regions of ELE1. None of the breakpoints occurred at the same base or within a similar sequence. There was also no evidence of preferential cleavage in AT-rich regions or other target DNA sites implicated in illegitimate recombination in mammalian cells. Modification of sequences at the cleavage sites was minimal, typically involving a 1-3 nucleotide deletion and/or duplication. Surprisingly, the alignment of ELE1 and RET introns in opposite orientation revealed that in each tumor the position of the break in one gene corresponded to the position of the break in the other gene. This tendency suggests that the two genes may lie next to each other but point in opposite directions in the nucleus. Such a structure would facilitate formation of RET/PTC3 rearrangements because a single radiation track could produce concerted breaks in both genes, leading to inversion due to reciprocal exchange via end-joining.
Asunto(s)
Biomarcadores de Tumor/genética , Carcinoma Papilar/genética , Cromosomas Humanos Par 10/efectos de la radiación , Cromosomas Humanos Par 18/efectos de la radiación , Proteínas de Neoplasias/genética , Neoplasias Inducidas por Radiación/genética , Proteínas Oncogénicas/genética , Oncogenes , Centrales Eléctricas , Liberación de Radiactividad Peligrosa , Neoplasias de la Tiroides/genética , Factores de Transcripción , Translocación Genética , Adolescente , Secuencia de Bases , Carcinoma Papilar/diagnóstico , Carcinoma Papilar/patología , Niño , Preescolar , Cromosomas Humanos Par 10/genética , Cromosomas Humanos Par 18/genética , ADN/efectos de la radiación , Daño del ADN , Reparación del ADN , Diagnóstico Diferencial , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Intrones , Masculino , Neoplasias Inducidas por Radiación/diagnóstico , Coactivadores de Receptor Nuclear , Recombinación Genética , Eliminación de Secuencia , Neoplasias de la Tiroides/diagnóstico , Neoplasias de la Tiroides/patología , UcraniaRESUMEN
Using whole-chromosome painting probes, we have analyzed the frequency of translocations of chromosomes 1, 3, and 10 in peripheral lymphocytes of 20 Gomel (Belarus) children, including both thyroid tumor affected and healthy individuals. Gomel was one of the most heavily radiocontaminated areas due to fallout from the Chernobyl nuclear power plant disaster. As controls, 14 healthy children from Pisa (Italy) were investigated simultaneously. Translocation rates were significantly higher in the tumor affected (1.71 +/- 0.68) and healthy Gomel children (2.69 +/- 0.50) than in the Italian controls (0.79 +/- 0.24). We also observed, in healthy Gomel children, an approximately three-fold higher frequency of chromosome 10 translocations compared to translocations affecting chromosomes 1 or 3 (P = 0.0096), a difference that was made even larger (about four fold) after correcting for chromosome size (P = 0.0009). This finding suggests a preferential involvement of chromosome 10 in translocations induced in vivo by low levels of ionizing radiation.
Asunto(s)
Cromosomas Humanos Par 10/efectos de la radiación , Linfocitos/efectos de la radiación , Ceniza Radiactiva , Translocación Genética/efectos de la radiación , Adolescente , Niño , Preescolar , Femenino , Humanos , Hibridación Fluorescente in Situ , Masculino , Centrales Eléctricas , República de BelarúsRESUMEN
We have used X-ray irradiation and cell fusion to generate somatic cell hybrids containing fragments of human chromosome 10. Our experiments were directed towards isolating the region of the MEN2A gene in hybrids and to use those as the source of DNA for cloning and mapping new markers from near the MEN2A locus. A number of hybrid clones containing human sequences that are tightly linked to the MEN2A gene were identified. Some 25% of our hybrids, however, proved to contain more than one human chromosome 10-derived fragment or showed evidence of deletions and/or rearrangements. A detailed analysis of the human content of X-ray irradiation hybrids is required to assess the integrity and number of human fragments retained. Despite retention of multiple human-derived fragments, these hybrids will prove useful as cloning and mapping resources.