IntroductionMost breast cancers that occur in women with germline BRCA1 mutations are estrogen receptor-negative (ER-) and also typically lack expression of progesterone receptor (PR) and HER2 overexpression. We undertook a study to assess the clinical factors that predict for an estrogen receptor positive (ER+) breast cancer in BRCA1 mutation carriers and to characterize the pathologic features of these tumors.MethodsClinical characteristics of BRCA1 carriers with 58 ER+ and 114 ER- first invasive breast cancers were compared. Pathologic features of BRCA1 ER+ cancers were compared to those of BRCA1 ER- cancers and to age-matched ER+ sporadic cancers.ResultsBRCA1 carriers aged ≥ 50 at diagnosis of first invasive breast cancer were more likely to have an ER+ cancer compared to those aged < 50 (57% vs 29%, P = 0.005). ER+ BRCA1 cancers were less likely than ER- BRCA1 cancers to have "BRCA-associated" features such as high mitotic activity, geographic necrosis/fibrotic focus, and pushing margins (RR 0.06, 0.22, 0.24; P < 0.001, 0.02, 0.03 respectively). When compared to sporadic ER+ cancers, ER+ BRCA1 cancers were more often of invasive ductal type (RR 2.4, P = 0.03), with a high mitotic rate (RR 5.0, P = 0.006) and absent or mild lymphocytic infiltrate (RR 10.2, P = 0.04).ConclusionsBRCA1 carriers who are older at first breast cancer diagnosis are more likely to have ER+ tumors than younger BRCA1 carriers. These ER+ cancers appear pathologically "intermediate" between ER- BRCA1 cancers and ER+ sporadic breast cancers raising the possibility that either some ER+ BRCA1 cancers are incidental or that there is a unique mechanism by which these cancers develop.

BACKGROUND Women with BRCA1 mutations develop breast cancer with similar pathologic features to sporadic triple negative (TN) breast cancer, a subtype associated with early disease relapse and poor outcome. We compared the clinical outcome of women with and without BRCA1 mutations who had TN breast cancer treated with conventional chemotherapy. METHODS Women with stage I-III TN breast cancer who had BRCA1 testing within 36 months of diagnosis and received alkylating chemotherapy were identified from clinical databases and a SPORE specimen bank. BRCA2 mutation carriers were excluded, resulting in a study cohort of 46 BRCA1 carriers and 71 non-carriers. Sites of metastasis, relapse rates and survival were compared among carriers and non-carriers. The median follow-up was 75 months. RESULTS BRCA1 carriers were younger at diagnosis (p<0.001) and had smaller tumors (p=0.03) than non-carriers. Freedom from distant metastasis at 5 years was 76% for carriers and 70% for non-carriers (HR 0.79, p=0.5). Sites of distant recurrence did not differ significantly (p=0.15), although BRCA1 carriers had a propensity for brain relapse (58% vs. 24%, p=0.06). Overall survival at 5 years was 82% for carriers and 74% for non-carriers (HR 0.64, p=0.25). Adjusting for age and stage, BRCA1 mutation status was not an independent predictor of survival (HR 0.73, p=0.48). CONCLUSION BRCA1 mutation carriers with TN disease have similar survival rates to non-carriers when treated with alkylating chemotherapy. Women with BRCA1-related breast cancer may benefit from novel therapies that target DNA repair, and further study is needed to identify sporadic TN breast cancers with a BRCA-deficient phenotype.

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Peripherin-2, the product of the rds gene, is a tetraspanin protein. In this study, we show that peripherin-2 forms a complex with melanoregulin (MREG), the product of the Mreg locus. Genetic studies suggest that MREG is involved in organelle biogenesis. In this study, we explore the role of this protein in processes associated with the formation of disk membranes, specialized organelles of photoreceptor rod cells. MREG antibodies were generated and found to be immunoreactive with a 28 kDa protein in retinal extracts, bovine OS, ARPE-19 cells, and rat RPE. MREG colocalized with peripherin-2 in WT (CB6F1/J) and in rds+/- retinas. Western blots of serial tangential sections confirmed the close association of these two proteins within the IS and basal outer segment of rods. Immunoprecipitation (IP) of OS extracts showed formation of a complex between MREG and peripherin-2-ROM-1 hetero-oligomers. This interaction was confirmed with pulldown analyses in which the GST-PerCter protein selectively pulled down His-MREG and His-MREG selectively pulled down PerCter. Biacore analysis using peptide inhibitors and per-2 truncation mutant studies allowed us to map the MREG binding site on per-2 to the last five residues of the C-terminus (Gln341-Gly346), and kinetic data predicted a KD of 80 nM for PerCter-MREG binding. Finally, the effect of MREG on photoreceptor specific membrane fusion was assayed using a disk-plasma membrane cell free assay. Preincubation of target membranes with MREG resulted in a dose-dependent inhibition of fusion with an IC50 in the submicromolar range. Collectively, these results suggest that this newly identified protein regulates peripherin-2 function.