Purpose: Triple-negative (TN; estrogen receptor, progesterone receptor, and HER-2 negative) cancer and basal-like breast cancer (BLBC) are associated with poor outcome and lack the benefit of targeted therapy. It is widely perceived that BLBC and TN tumors are synonymous and BLBC can be defined using a TN definition without the need for the expression of basal markers. Experimental Design: We have used two well-defined cohorts of breast cancers with a large panel of biomarkers, BRCA1 mutation status, and follow-up data to compare the clinicopathologic and immunohistochemical features of TN tumors expressing one or more of the specific basal markers (CK5/6, CK17, CK14, and epidermal growth factor receptor; BLBC) with those TN tumors that express none of these markers (TN3BKE-).Results: Here, we show that although the morphologic features of BLBC are not significantly different from that of TN3BKE-tumors, BLBC showed distinct clinical and immunophenotypic differences. BLBC showed a statistically significant association with the expression of the hypoxia-associated factor (CA9), neuroendocrine markers, and other markers of poor prognosis such as p53. A difference in the expression of cell cycle-associated proteins and biomarkers involved in the immunologic portrait of tumors was seen. Compared with TN3BKE-tumors, BLBC was positively associated with BRCA1 mutation status and showed a unique pattern of distant metastasis, better response to chemotherapy, and shorter survival. Conclusion: TN breast cancers encompass a remarkably heterogeneous group of tumors. Expression of basal markers identifies a biologically and clinically distinct subgroup of TN tumors, justifying the use of basal markers (inTN tumors) to define BLBC.

International audienceTransferrin receptor (CD71) is involved in the cellular uptake of iron and is expressed on cells with high proliferation. It may be implicated in promoting the growth of endocrine resistant phenotypes within ER+/luminal-like breast cancer. We used a panel of in vitro cell models of acquired resistance to tamoxifen (TAMR), Faslodex (FASR) or severe oestrogen deprivation (MCF-7X) and the ER+ luminal MCF-7 parental line to determine CD71 mRNA expression and to study transferrin (Tf) effects on in vitro tumour growth and its inhibition. Furthermore, CD71 protein expression was assessed in a well-characterized series of patients with invasive breast carcinoma using tissue microarrays. Our results demonstrated a striking elevation of CD71 in all cell models of acquired resistance. Exogenous Tf significantly promoted growth in MCF-7-X and MCF-7 cells but more so in MCF-7-X; this growth was significantly reduced by Faslodex (FAS) or a phosphoinositide-3 kinase inhibitor (LY294002). Increased CD71 expression was associated with poor NPI score, tumour proliferation, basal CKs, p53, EGFR, HER2, steroid receptor negativity and shortened breast cancer specific survival ( < 0.001). On multivariate analysis, CD71 was found to be an independent prognostic factor in the ER+ cohort of patients. In conclusion, therapies of current interest in breast cancer (e.g. FAS, PI3K-inhibitors) appear able to partially impact on transferrin/CD71-promoted growth, but further investigation of this important mitogenic mechanism may assist in designing new therapeutic strategies to target highly proliferative, endocrine resistant breast cancers. CD71 appears to be a candidate marker of a subgroup of ER+/luminal-like breast cancer characterised by poor outcome and resistance to tamoxifen

Our results demonstrate a strong correlation between CCND1 amplification and its protein expression in breast cancer. However, protein expression is more pervasive than gene amplification and associated with ER expression.