RESUMO
The preservation of pathogenic BRCA1/2 germline mutations in tumor tissues is usually not questioned, while it remains unknown whether these interact with somatic genotypes for patient outcome. Herein we compared germline and tumor genotypes in operable triple-negative breast cancer (TNBC) and evaluated their combined effects on prognosis. We analyzed baseline germline and primary tumor genotype data obtained by Sanger and Next Generation Sequencing in 194 TNBC patients. We also performed multiple tests interrogating the preservation of germline mutations in matched tumors and breast tissue from carriers with available material. Patients had been treated within clinical trials with adjuvant anthracyclines-taxanes based chemotherapy. We identified 50 (26%) germline mutation carriers (78% in BRCA1) and 136 (71%) tumors with somatic mutations (83% in TP53). Tumor mutation patterns differed between carriers and non-carriers (P<0.001); PIK3CA mutations were exclusively present in non-carriers (P=0.007). Germline BRCA1/2 mutations were not detected in matched tumors and breast tissues from 14 out of 33 (42%) evaluable carriers. Microsatellite markers revealed tumor loss of the germline mutant allele in one case only. Tumors that had lost the germline mutation demonstrated a higher incidence of somatic TP53 mutations as compared to tumors with preserved germline mutations (P=0.036). Germline mutation status significantly interacted with tumor TP53 mutations for patient disease-free survival (interaction P=0.026): In non-carriers, tumor TP53 mutations did not affect outcome; In carriers, those with mutated TP53 tumors experienced more relapses compared to those with wild-type TP53 tumors (36% vs. 9% relapse rate, respectively). In conclusion, we show that loss of germline BRCA1/2 mutations is not a rare event in TNBC. This finding, the observed differences in tumor genotypes with respect to germline status and the prognostic interaction between germline BRCA1-related and tumor TP53 mutation status prompt for combined germline and tumor genotyping for the classification of TNBC, particularly in the context of clinical trials evaluating synthetic lethality drugs.
RESUMO
We have compared the toxicity, mutagenicity and transport in Saccharomyces cerevisiae of three DNA-intercalating fluorescent dyes widely used to stain DNA in gels. Safety data about ethidium bromide (EtBr) are contradictory, and two compounds of undisclosed structure (Redsafe and Gelred) have been proposed as safe alternatives. Our results indicate that all three compounds inhibit yeast growth, with Gelred being the most inhibitory and also the only one causing cell death. EtBr and Gelred, but not Redsafe, induce massive formation of petite (non-respiratory) mutants, but only EtBr induces massive loss of mitochondrial DNA. All three compounds increase reversion of a chromosomal point mutation (lys2-801(amber) ), with Gelred being the most mutagenic and Redsafe the least. These dyes are all cationic and are probably taken by cells through non-selective cation channels. We could measure the glucose-energized transport of EtBr and Gelred inside the cells, while uptake of Redsafe was below our detection limit. We conclude that although all three compounds are toxic and mutagenic in the yeast system, Redsafe is the safest for yeast, probably because of very limited uptake by these cells.