title: Genomic signature of BRCA1 deficiency in sporadic basal-like breast tumors.
abstract: About 10-20% of all breast carcinomas show a basal-like phenotype, while ∼ 90% of breast tumors from BRCA1-mutation carriers are of this subtype. There is growing evidence that BRCA1-mutated tumors are not just a specific subset of the basal-like tumors, but that (the majority of) basal-like tumors show a dysfunctional BRCA1 pathway. This has major treatment implications, because emerging regimens specifically targeting DNA repair mechanisms would then be most effective against these tumors. To further understand the involvement of BRCA1 deficiency in sporadic basal-like tumors, we investigated 41 basal-like tumors for BRCA1 mRNA expression by quantitative real-time polymerase chain reaction, BRCA1 promoter methylation, their genomic profile by array-CGH, and gene expression levels by whole genome expression arrays. Array-CGH results were compared to those of 34 proven BRCA1-mutated tumors. Basal-like tumors were subdivided into two equal groups: deficient and proficient in BRCA1 gene expression. The chromosomal makeup of BRCA1 deficient sporadic basal-like tumors was similar to that of BRCA1-mutated tumors. BRCA1 proficient sporadic basal-like tumors were more similar to nonbasal-like tumors. Only half of the basal-like breast tumors are actually deficient in BRCA1 expression. Gain of chromosome arm 3q is a marker for BRCA1 deficiency in hereditary and sporadic breast tumors.
authors.affiliation: Division of Experimental Therapy, The Netherlands Cancer Institute NKI/AvL, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands. s.joosse@in-silico.net
authors.forename: Simon A
authors.initials: SA
authors.lastname: Joosse
authors.forename: Kim I M
authors.initials: KI
authors.lastname: Brandwijk
authors.forename: Lennart
authors.initials: L
authors.lastname: Mulder
authors.forename: Jelle
authors.initials: J
authors.lastname: Wesseling
authors.forename: Juliane
authors.initials: J
authors.lastname: Hannemann
authors.forename: Petra M
authors.initials: PM
authors.lastname: Nederlof
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019313:BRCA1 Protein / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics*; D002869:Chromosome Aberrations; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics; D056915:DNA Copy Number Variations / Q000235:genetics; D019175:DNA Methylation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000235:genetics; D006801:Humans; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D018295:Neoplasms, Basal Cell / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics
chemical_list: D019313:BRCA1 Protein; D006657:Histones; C411762:RASSF1 protein, human; D025521:Tumor Suppressor Proteins