Although it is increasingly evident that cancer is influenced by signals emanating from tumor stroma, little is known regarding how changes in stromal gene expression affect epithelial tumor progression. We used laser capture microdissection to compare gene expression profiles of tumor stroma from 53 primary breast tumors and derived signatures strongly associated with clinical outcome. We present a new stroma-derived prognostic predictor (SDPP) that stratifies disease outcome independently of standard clinical prognostic factors and published expression-based predictors. The SDPP predicts outcome in several published whole tumor-derived expression data sets, identifies poor-outcome individuals from multiple clinical subtypes, including lymph node-negative tumors, and shows increased accuracy with respect to previously published predictors, especially for HER2-positive tumors. Prognostic power increases substantially when the predictor is combined with existing outcome predictors. Genes represented in the SDPP reveal the strong prognostic capacity of differential immune responses as well as angiogenic and hypoxic responses, highlighting the importance of stromal biology in tumor progression.

In biopsy-proven node-positive breast cancer after NAC, a low SNB FNR (8.4%) can be achieved with mandatory use of IHC. SN metastases of any size should be considered positive. The SNB IR was 87.6%, and in the presence of a technical failure, axillary node dissection should be performed. We recommend that SN evaluation with IHC be further evaluated before being included in future guidelines on the use of SNB after NAC in this setting.

Metabolic reprogramming is a hallmark of cellular transformation, yet little is known about metabolic changes that accompany tumor metastasis. Here we show that primary breast cancer cells display extensive metabolic heterogeneity and engage distinct metabolic programs depending on their site of metastasis. Liver-metastatic breast cancer cells exhibit a unique metabolic program compared to bone- or lung-metastatic cells, characterized by increased conversion of glucose-derived pyruvate into lactate and a concomitant reduction in mitochondrial metabolism. Liver-metastatic cells displayed increased HIF-1α activity and expression of the HIF-1α target Pyruvate dehydrogenase kinase-1 (PDK1). Silencing HIF-1α reversed the glycolytic phenotype of liver-metastatic cells, while PDK1 was specifically required for metabolic adaptation to nutrient limitation and hypoxia. Finally, we demonstrate that PDK1 is required for efficient liver metastasis, and its expression is elevated in liver metastases from breast cancer patients. Our data implicate PDK1 as a key regulator of metabolism and metastatic potential in breast cancer.

Understanding the tumor immune microenvironment (TIME) promises to be key for optimal cancer therapy, especially in triple-negative breast cancer (TNBC). Integrating spatial resolution of immune cells with laser capture microdissection gene expression profiles, we defined distinct TIME stratification in TNBC, with implications for current therapies including immune checkpoint blockade. TNBCs with an immunoreactive microenvironment exhibited tumoral infiltration of granzyme B + CD8 + T cells (GzmB + CD8 + T cells), a type 1 IFN signature, and elevated expression of multiple immune inhibitory molecules including indoleamine 2,3-dioxygenase (IDO) and programmed cell death ligand 1 (PD-L1), and resulted in good outcomes. An "immune-cold" microenvironment with an absence of tumoral CD8 + T cells was defined by elevated expression of the immunosuppressive marker B7-H4, signatures of fibrotic stroma, and poor outcomes. A distinct poor-outcome immunomodulatory microenvironment, hitherto poorly characterized, exhibited stromal restriction of CD8 + T cells, stromal expression of PD-L1, and enrichment for signatures of cholesterol biosynthesis. Metasignatures defining these TIME subtypes allowed us to stratify TNBCs, predict outcomes, and identify potential therapeutic targets for TNBC.

No more than Ϸ30% of hereditary breast cancer has been accounted for by mutations in known genes. Most of these genes, such as BRCA1, BRCA2, TP53, CHEK2, ATM, and FANCJ/BRIP1, function in DNA repair, raising the possibility that germ line mutations in other genes that contribute to this process also predispose to breast cancer. Given its close relationship with BRCA2, PALB2 was sequenced in affected probands from 68 BRCA1/BRCA2-negative breast cancer families of Ashkenazi Jewish, French Canadian, or mixed ethnic descent. The average BRCAPRO score was 0.58. A truncating mutation (229delT) was identified in one family with a strong history of breast cancer (seven breast cancers in three female mutation carriers). This mutation and its associated breast cancers were characterized with another recently reported but unstudied mutation (2521delA) that is also associated with a strong family history of breast cancer. There was no loss of heterozygosity in tumors with either mutation. Moreover, comparative genomic hybridization analysis showed major similarities to that of BRCA2 tumors but with some notable differences, especially loss of 18q, a change that was previously unknown in BRCA2 tumors and less common in sporadic breast cancer. This study supports recent observations that PALB2 mutations are present, albeit not frequently, in breast cancer families. The apparently high penetrance noted in this study suggests that at least some PALB2 mutations are associated with a substantially increased risk for the disease.DNA repair ͉ FANCN ͉ Fanconi anemia ͉ hereditary predisposition T he presence of a family history is the most important predisposing factor for development of breast cancer. Among the genes known to be linked to familial breast cancer, BRCA1, BRCA2, CHK2, TP53, and ATM all participate in DNA damage responses (1), suggesting that familial breast cancer is, at least partly, a consequence of impaired genome stability control. PALB2 is a recently identified BRCA2-interacting protein, and a high fraction of each protein interacts with the other (2). Their association is essential for BRCA2 anchorage to nuclear structures and for its function in double strand break repair (DSBR) by homologous recombination (HR). Furthermore, introduction of PALB2 siRNAs sensitized cells to mitomycin C like BRCA2 siRNA (2). PALB2-depleted cells, therefore, display a Fanconi anemia (FA)/ BRCA2-deficient phenotype (3).Recent evidence shows that PALB2 is, in fact, another FA gene (known as FANCN), and that FANCN disease resembles FA arising from biallelic BRCA2 mutations in that the affected children are prone to develop embryonal tumors (medulloblastoma, Wilms tumor) and experience early bone marrow failure (4, 5). In other respects, FA-N cases have a typical FA phenotype. Their cells reveal increased chromosome breakage after interstrand cross-linking agent exposure, and these patients reveal growth retardation and various congenital malformations (4, 5). It is unclear why a different cancer predisposition phenotype exists in FA c...

Elevated MET receptor tyrosine kinase correlates with poor outcome in breast cancer, yet the reasons for this are poorly understood. We thus generated a transgenic mouse model targeting expression of an oncogenic Met receptor (Met mt ) to the mammary epithelium. We show that Met mt induces mammary tumors with multiple phenotypes. These reflect tumor subtypes with gene expression and immunostaining profiles sharing similarities to human basal and luminal breast cancers. Within the basal subtype, Met mt induces tumors with signatures of WNT and epithelial to mesenchymal transition (EMT). Among human breast cancers, MET is primarily elevated in basal and ERBB2-positive subtypes with poor prognosis, and we show that MET, together with EMT marker, SNAIL, are highly predictive of poor prognosis in lymph nodenegative patients. By generating a unique mouse model in which the Met receptor tyrosine kinase is expressed in the mammary epithelium, along with the examination of MET expression in human breast cancer, we have established a specific link between MET and basal breast cancer. This work identifies basal breast cancers and, additionally, poor-outcome breast cancers, as those that may benefit from anti-MET receptor therapies.gene expression profiling ͉ mouse models ͉ epithelial to mesenchymal transition B reast cancer is a heterogeneous disease that comprises distinct biological entities that are correlated with diverse clinical outcomes and responses to treatment. Gene expression profiling and molecular pathology have revealed that breast cancers naturally divide into the luminal, ERBB2-positive, and basal-like subtypes (1, 2). These subtypes were named to reflect gene expression patterns of the 2 principal cell types of the differentiated breast, luminal epithelial cells lining the duct and lobule, and myoepithelial cells that form a single layer surrounding the luminal cells. The luminal subtype comprises ϳ60% of breast cancers, is estrogen receptor (ESR1)-positive, and expresses ESR1-responsive genes and luminal markers such as keratin 8/18. Up to 25% of breast cancers are identified with overexpression/amplification of the ERBB2 receptor tyrosine kinase, and these tumors are generally ESR1/ progesterone receptor (PGR)-negative. The basal group is characterized as ESR1/PGR/ERBB2-negative and is frequently positive for basal keratins 5/6 (3, 4). Breast cancers within the luminal subtype receive antiestrogen therapies and tend to have a good prognosis. Because of the lack of treatment options, patients within the basal subtype historically have a poor prognosis (1). Hence, an understanding of the signaling pathways active in these tumors is crucial for the generation of targeted therapies.The MET receptor tyrosine kinase, which is the receptor for hepatocyte growth factor/scatter factor (HGF/SF), is expressed at elevated levels in 15-20% of human breast cancers (5), and is a prognostic factor for poor outcome (6, 7). High levels of the MET receptor ligand HGF/SF in the serum of breast cancer patients is also correl...

The liver represents the third most frequent site of metastasis in patients with breast cancer. We performed in vivo selection using 4T1 breast cancer cells to identify genes associated with the liver metastatic phenotype. Coincident with the loss of numerous tight-junctional proteins, we observe claudin-2 overexpression, specifically in liver-aggressive breast cancer cells. We further demonstrate that claudin-2 is both necessary and sufficient for the ability of 4T1 breast cancer cells to colonize and grow in the liver. The liver-aggressive breast cancer cells display a claudin-2-mediated increase in their ability to adhere to extracellular matrix (ECM) components, such as fibronectin and type IV collagen. Claudin-2 facilitates these cell/matrix interactions by increasing the cell surface expression of a 2 b 1 -and a 5 b 1 -integrin complexes in breast cancer cells. Indeed, claudin-2-mediated adhesion to fibronectin and type IV collagen can be blocked with neutralizing antibodies that target a 5 b 1 and a 2 b 1 complexes, respectively. Immunohistochemical analyses reveal that claudin-2, although weakly expressed in primary human breast cancers, is readily detected in all liver metastasis samples examined to date. Together, these results uncover novel roles for claudin-2 in promoting breast cancer adhesion to the ECM and define its importance during breast cancer metastasis to the liver.

Introduction The role of the cellular microenvironment in breast tumorigenesis has become an important research area. However, little is known about gene expression in histologically normal tissue adjacent to breast tumor, if this is influenced by the tumor, and how this compares with non-tumor-bearing breast tissue.