Risk of colorectal cancer associated with BRCA1 and/or BRCA2 mutation carriers: systematic review and meta-analysis.

BACKGROUND: Carriers of the BRCA1 and/or BRCA2 mutation incur a lifetime risk of up to 85 per cent for breast cancer, and between 20 and 40 per cent for ovarian cancer. Efforts to estimate the lifetime risk of developing colorectal cancer for BRCA mutation carriers have produced conflicting results. Consequently, there are no formal guidelines regarding the need for bowel screening for individuals with BRCA1 and/or BRCA2 mutations. This systematic review and meta-analysis determined the risk of colorectal cancer associated with BRCA carrier mutations. METHODS: The primary outcome was incidence of colorectal cancer in BRCA mutation carriers. Secondary outcomes were the incidence in BRCA1 and BRCA2 carriers, Ashkenazi Jews, and age- and sex-matched cohorts. RESULTS: Eleven studies were included in the review, with an overall population of 14 252 and 4831 colorectal cancers identified. Nine studies were included in the meta-analysis. There was no increase in colorectal cancer among patients carrying a BRCA mutation (odds ratio 1·03, 95 per cent c.i. 0·80 to 1·32; P = 0·82). After adjustment for Ashkenazi heritage, and age and sex estimates, there was no increased odds of developing colorectal cancer (with no heterogeneity, I2  = 0 per cent). CONCLUSION: BRCA1 and/or BRCA2 mutation carriers are not at a higher risk of colorectal cancer.

ANTECEDENTES: Las portadoras de la mutación BRCA1 y/o BRCA2 presentan un riesgo a lo largo de la vida de hasta un 85% para presentar un cáncer de mama y entre 20-40% para el cáncer de ovario. Los esfuerzos para estimar el riesgo de desarrollar cáncer colorrectal (colorectal cancer, CCR) a lo largo de la vida en portadoras de mutaciones BRCA han dado resultados contradictorios. En consecuencia, no existen pautas formales con respecto a la necesidad de realizar el cribado de CRC en personas portadoras de mutaciones BRCA1 y/o BRCA2. Esta revisión sistemática y metaanálisis analiza el riesgo de CRC asociado en pacientes portadoras de mutaciones BRCA. MÉTODOS: Se incluyeron nueve estudios en el metaanálisis. La población general del estudio fue de 18.839 pacientes, con 4.978 con CRC identificado. La variable principal fue la incidencia de cáncer colorrectal en portadoras de mutaciones BRCA. Las variables secundarias incluyeron el análisis de la incidencia de subgrupos en BRCA 1, BRCA 2, etnia judía Ashkenazi y cohortes emparejadas por edad y sexo. RESULTADOS: No hubo un aumento de CRC en pacientes con una mutación BRCA (razón de oportunidades, odds ratio, OR 1,03; i.c. del 95% 0,80-1,32; P = 0,82). Cuando se ajustó de acuerdo con la ascendencia Ashkenazi y las estimaciones de edad y sexo, no hubo mayores probabilidades de desarrollar cáncer colorrectal (sin heterogeneidad en los estudios (I2 = 0)). CONCLUSIÓN: Este metaanálisis concluye que el riesgo de cáncer colorrectal no fue significativamente mayor en las portadoras de mutaciones BRCA1 y/o BRCA2. Sin embargo, se requiere más evidencia antes de no recomendar la colonoscopia de cribado a las portadoras de la mutación BRCA1/2. Las pruebas de inmunoquímica fecal pueden ser una alternativa apropiada en esta población.

Nuclear and mitochondrial distribution of organoamidoplatinum(II) lesions in cisplatin-sensitive and -resistant adenocarcinoma cells.

The DNA binding pattern of the organoamidoplatinum(II) compound 1a is of considerable interest because of its known activity against cisplatin-resistant cells. The activity of 1a appears to be due at least in part to a greater cellular uptake than cisplatin into cisplatin-resistant cells, but little is known of the DNA reactions of the organoamidoplatinum(II) compounds. In this study the level of DNA cross-linking and total DNA lesions formed by 1 a were measured by gene-specific Southern hybridization cross-linking assays and by quantitative PCR in cisplatin-sensitive (2008) and in cisplatin-resistant 2008/R human adenocarcinoma cell lines. The surprising result was that the major difference between cisplatin and 1a was that the number of interstrand cross-links induced by 1a were approximately 5-fold greater than that induced by cisplatin in the nuclear (but not mitochondrial) DNA of resistant cells, even though the total number of lesions were essentially the same in both sensitive and resistant cells. This result suggests that the extent of interstrand cross-linking is a critical determinant of the cellular response to 1a and that the enhanced uptake of 1a into resistant cells results in this elevated level of cross-linking, leading to good activity of 1a against cisplatin-resistant cells. It remains unclear as to why 1a exhibits such selective damage to nuclear DNA, and insight into the molecular aspects of this selectivity will provide new opportunities for the further development of new platinum-based agents with activity against cisplatin-resistant cells.

An in vitro transcription assay for probing drug-DNA interactions at individual drug sites.

An in vitro transcription assay of drug-DNA interactions has been described and is based largely on the stable lac UV5-initiated transcription complex. This system utilizes a synchronized population of radiolabeled nascent RNA 10 nucleotides long. Reaction of this initiated transcription complex with drug and subsequent elongation of the nascent RNA by Escherichia coli RNA polymerase, reveals blockages at drug binding sites. From these blockages it is possible to obtain four features of the drug-DNA interaction: the sequence of preferred drug binding sites, the relative drug occupancy at each binding site, the drug dissociation rate at each site, and the probability of drug-induced termination of transcription at each site. The unidirectional transcription assay has been extended to a two-promoter, counter-directed system, which yields a bidirectional transcription footprint of drug sites.