CCN6 knockdown disrupts acinar organization of breast cells in three-dimensional cultures through up-regulation of type III TGF-β receptor

Directed differentiation of human pluripotent stem cells into articular cartilage reveals effects caused by absence of WISP3, the gene responsible for progressive pseudorheumatoid arthropathy of childhood

OBJECTIVES

Progressive pseudorheumatoid arthropathy of childhood (PPAC), caused by deficiency of WNT1 inducible signalling pathway protein 3 (WISP3), has been challenging to study because no animal model of the disease exists and cartilage recovered from affected patients is indistinguishable from common end-stage osteoarthritis. Therefore, to gain insights into why precocious articular cartilage failure occurs in this disease, we made in vitro derived articular cartilage using isogenic WISP3-deficient and WISP3-sufficient human pluripotent stem cells (hPSCs).

METHODS

We generated articular cartilage-like tissues from induced-(i) PSCs from two patients with PPAC and one wild-type human embryonic stem cell line in which we knocked out WISP3. We compared these tissues to in vitro-derived articular cartilage tissues from two isogenic WISP3-sufficient control lines using histology, bulk RNA sequencing, single cell RNA sequencing and in situ hybridisation.

RESULTS

WISP3-deficient and WISP3-sufficient hPSCs both differentiated into articular cartilage-like tissues that appeared histologically similar. However, the transcriptomes of WISP3-deficient tissues differed significantly from WISP3-sufficient tissues and pointed to increased TGFβ, TNFα/NFκB, and IL-2/STAT5 signalling and decreased oxidative phosphorylation. Single cell sequencing and in situ hybridisation revealed that WISP3-deficient cartilage contained a significantly higher fraction (~4 fold increase, p<0.001) of superficial zone chondrocytes compared with deeper zone chondrocytes than did WISP3-sufficient cartilage.

CONCLUSIONS

WISP3-deficient and WISP3-sufficient hPSCs can be differentiated into articular cartilage-like tissues, but these tissues differ in their transcriptomes and in the relative abundances of chondrocyte subtypes they contain. These findings provide important starting points for in vivo studies when an animal model of PPAC or presymptomatic patient-derived articular cartilage becomes available.

Directed differentiation of human pluripotent stem cells into articular cartilage reveals effects caused by absence of WISP3 , the gene responsible for Progressive Pseudorheumatoid Arthropathy of Childhood

Objectives

Progressive Pseudorheumatoid Arthropathy of Childhood (PPAC), caused by deficiency of WNT1 inducible signaling pathway protein 3 ( WISP3 ), has been challenging to study because no animal model of the disease exists and cartilage recovered from affected patients is indistinguishable from common end-stage osteoarthritis. Therefore, to gain insights into why precocious articular cartilage failure occurs in this disease, we made in vitro derived articular cartilage using isogenic WISP3 -deficient and WISP3 -sufficient human pluripotent stem cells (hPSCs).

Methods

We generated articular cartilage-like tissues from induced-(i)PSCs from 2 patients with PPAC and 1 wild-type human embryonic stem cell line in which we knocked out WISP3. We compared these tissues to in vitro -derived articular cartilage tissues from 2 isogenic WISP3 -sufficient control lines using histology, bulk RNA sequencing, single cell RNA sequencing, and in situ hybridization.

Results

WISP3 -deficient and WISP3 -sufficient hPSCs both differentiated into articular cartilage-like tissues that appeared histologically similar. However, the transcriptomes of WISP3 -deficient tissues differed significantly from WISP3 -sufficient tissues and pointed to increased TGFβ, TNFα/NFkB, and IL-2/STAT5 signaling and decreased oxidative phosphorylation. Single cell sequencing and in situ hybridization revealed that WISP3 -deficient cartilage contained a significantly higher fraction (∼ 4-fold increase, p < 0.001) of superficial zone chondrocytes compared to deeper zone chondrocytes than did WISP3 -sufficient cartilage. Conclusions WISP3 -deficient and WISP3 -sufficient hPSCs can be differentiated into articular cartilage-like tissues, but these tissues differ in their transcriptomes and in the relative abundances of chondrocyte sub-types they contain. These findings provide important starting points for in vivo studies when an animal model of PPAC or presymptomtic patient-derived articular cartilage becomes available.

KEY MESSAGES

What is already known on this topic: Loss-of-function mutations in WISP3 cause Progressive Pseudorheumatoid Arthropathy of Childhood (PPAC), yet the precise function of WISP3 in cartilage is unknown due to the absence of cartilage disease Wisp3 knockout mice and the lack of available PPAC patient cartilage that is not end-stage. Thus, most functional studies of WISP3 have been performed in vitro using WISP3 over-expressing cell lines (i.e., not wild-type) and WISP3 -deficient chondrocytes. What this study adds: We describe 3 new WISP3 -deficient human pluripotent stem cell (hPSC) lines and show they can be differentiated into articular cartilage-like tissue. We compare in vitro -derived articular cartilage made from WISP3 -deficient and isogenic WISP3 - sufficient hPSCs using bulk RNA sequencing, single cell RNA sequencing, and in situ hybridization. We observe significant differences in the expression of genes previously associated with cartilage formation and homeostasis in the TGFβ, TNFα/NFkB, and IL-2/STAT5 signaling pathways. We also observe that WISP3-deficient cartilage-like tissues contain significantly higher fractions of chondrocytes that express superficial zone transcripts. These data suggest precocious cartilage failure in PPAC is the result of abnormal articular cartilage formation, dysregulated homeostatic signaling, or both.How this study might affect research, practice or policy: This study uses in vitro -derived articular cartilage to generate hypotheses for why cartilage fails in children with PPAC. This work prioritizes downstream studies to be performed when pre-symptomatic patient-derived cartilage samples or animal model of PPAC becomes available. It is essential to know how WISP3 functions in cartilage to develop therapies that benefit patients with PPAC and other degenerative joint diseases.

The matricellular protein CCN6 differentially regulates mitochondrial metabolism in normal epithelium and in metaplastic breast carcinomas

Metaplastic breast carcinoma (MBC) is an aggressive subtype of triple negative breast cancer with undefined precursors, limited response to chemotherapy, and frequent distant metastasis. Our laboratory has reported that CCN6/WISP3, a secreted protein that regulates growth factor signaling, is downregulated in over 85% of MBCs. Through generation of a mammary epithelial cell-specific Ccn6 knockout mouse model (MMTV-cre;Ccn6^fl/fl) we have demonstrated that CCN6 is a tumor suppressor for MBC; MMTV-cre;Ccn6^fl/fl mice develop tumors recapitulating the histopathology and proteogenomic landscape of human MBC, but the mechanisms need further investigation. In this study, we report that preneoplastic mammary glands of 8-week-old MMTV-Cre;Ccn6^fl/fl female mice show significant downregulation of mitochondrial respiratory chain genes compared to controls, which are further downregulated in MBCs of MMTV-Cre;Ccn6^fl/fl mice and humans. We found that CCN6 downregulation in non-tumorigenic breast cells reduces mitochondrial respiration and increases resistance to stress-induced apoptosis compared to controls. Intracellular ectopic CCN6 protein localizes to the mitochondria in MDA-MB-231 mesenchymal-like breast cancer cells, increases mitochondrial respiration and generation of reactive oxygen species, and reverses doxorubicin resistance of MBC cells. Our data highlight a novel function of CCN6 in the regulation of redox states in preneoplastic progression and suggest potential preventative and treatment strategies against MBC based on CCN6 upregulation.

A reproducible scaffold-free 3D organoid model to study neoplastic progression in breast cancer

While 3D cellular models are useful to study biological processes, gel-embedded organoids have large variability. This paper describes high-yield production of large (~1 mm diameter), scaffold-free, highly-spherical organoids in a one drop-one organoid format using MCF10A cells, a non-tumorigenic breast cell line. These organoids display a hollow lumen and secondary acini, and express mammary gland-specific and progenitor markers, resembling normal human breast acini. When subjected to treatment with TGF-β, the hypoxia-mimetic reagent CoCl2, or co-culture with mesenchymal stem/stromal cells (MSC), the organoids increase collagen I production and undergo large phenotypic and morphological changes of neoplastic progression, which were reproducible and quantifiable. Advantages of this scaffold-free, 3D breast organoid model include high consistency and reproducibility, ability to measure cellular collagen I production without noise from exogenous collagen, and capacity to subject the organoid to various stimuli from the microenvironment and exogenous treatments with precise timing without concern of matrix binding. Using this system, we generated organoids from primary metaplastic mammary carcinomas of MMTV-Cre;Ccn6fl/fl mice, which retained the high grade spindle cell morphology of the primary tumors. The platform is envisioned to be useful as a standardized 3D cellular model to study how microenvironmental factors influence breast tumorigenesis, and to potential therapeutics.

The emerging role of WISP proteins in tumorigenesis and cancer therapy

Accumulated evidence has demonstrated that WNT1 inducible signaling pathway protein (WISP) genes, which belong to members of the CCN growth factor family, play a pivotal role in tumorigenesis and progression of a broad spectrum of human cancers. Mounting studies have identified that WISP proteins (WISP1-3) exert different biological functions in various human malignancies. Emerging evidence indicates that WISP proteins are critically involved in cell proliferation, apoptosis, invasion and metastasis in cancers. Because the understanding of a direct function of WISP proteins in cancer development and progression has begun to emerge, in this review article, we describe the physiological function of WISP proteins in a variety of human cancers. Moreover, we highlight the current understanding of how the WISP protein is involved in tumorigenesis and cancer progression. Furthermore, we discuss that targeting WISP proteins could be a promising strategy for the treatment of human cancers. Hence, the regulation of WISP proteins could improve treatments for cancer patients.

H19 long noncoding RNA alters trophoblast cell migration and invasion by regulating TβR3 in placentae with fetal growth restriction

Fetal growth restriction (FGR) is a well-recognized risk factor for perinatal mortality and morbidity, as well as neurodevelopmental impairment and adulthood onset disorders. Here we report that the H19 long noncoding RNA (lncRNA) is significantly decreased in placentae from pregnancies with FGR. Downregulation of H19 leads to reduced migration and invasion of extravillous trophoblast (EVT) cells in vitro. This is consistent with reduced trophoblast invasion that has been observed in FGR. Genome-scale transcriptome profiling of EVT cells reveals significantly decreased expression of the type III TGF-β receptor (TβR3) following H19 knockdown. Decreased TβR3 expression is also seen in FGR placentae. TβR3 repression decreases EVT cell migration and invasion, owing to impaired TGF-β signaling through a non-canonical TGF-β signaling pathway. Further, we identify TβR3 as a novel regulatory target of microRNA let-7. We propose that dysregulation of this newly identified H19/TβR3-mediated regulatory pathway may contribute to the molecular mechanism of FGR. Our findings are the first to show a lncRNA-based mechanism of FGR, holding promise for the development of novel predictive, diagnostic, and therapeutic modalities for FGR.

Matricellular CCN6 (WISP3) protein: a tumor suppressor for mammary metaplastic carcinomas

Located at 6q22-23, Ccn6 (WISP3) encodes for a matrix-associated protein of the CCN family, characterized by regulatory, rather than structural, roles in development and cancer. CCN6, the least studied member of the CCN family, shares the conserved multimodular structure of CCN proteins, as well as their tissue and cell-type specific functions. In the breast, CCN6 is a critical regulator of epithelial-to-mesenchymal transitions (EMT) and tumor initiating cells. Studies using human breast cancer tissue samples demonstrated that CCN6 messenger RNA and protein are expressed in normal breast epithelia but reduced or lost in aggressive breast cancer phenotypes, especially inflammatory breast cancer and metaplastic carcinomas. Metaplastic carcinomas are mesenchymal-like triple negative breast carcinomas, enriched for markers of EMT and stemness. RNAseq analyses of the TCGA Breast Cancer cohort show reduced CCN6 expression in approximately 50% of metaplastic carcinomas compared to normal breast. Our group identified frameshift mutations of Ccn6 in a subset of human metaplastic breast carcinoma. Importantly, conditional, mammary epithelial-cell specific ccn6 (wisp3) knockout mice develop invasive high-grade mammary carcinomas that recapitulate human spindle cell metaplastic carcinomas, demonstrating a tumor suppressor function for ccn6. Our studies on CCN6 functions in metaplastic carcinoma highlight the potential of CCN6 as a novel therapeutic approach for this specific type of breast cancer.

The matricellular protein CCN6 (WISP3) decreases Notch1 and suppresses breast cancer initiating cells

Increasing evidence supports that the epithelial to mesenchymal transition (EMT) in breast cancer cells generates tumor initiating cells (TICs) but the contribution of the tumor microenvironment to these programs needs further elucidation. CCN6 (WISP3) is a secreted matrix-associated protein (36.9 kDa) of the CCN family (named after CTGF, Cyr61 and Nov) that is reduced or lost in invasive carcinomas of the breast with lymph node metastasis and in inflammatory breast cancer. CCN6 exerts breast cancer growth and invasion inhibitory functions, but the mechanisms remain to be defined. In the present study we discovered that ectopic CCN6 overexpression in triple negative (TN) breast cancer cells and in cells derived from patients is sufficient to induce a mesenchymal to epithelial transition (MET) and to reduce TICs. In vivo, CCN6 overexpression in the TIC population of MDA-MB-231 cells delayed tumor initiation, reduced tumor volume, and inhibited the development of metastasis. Our studies reveal a novel CCN6/Slug signaling axis that regulates Notch1 signaling activation, epithelial cell phenotype and breast TICs, which requires the conserved thrombospondin type 1 (TSP1) motif of CCN6. The relevance of these data to human breast cancer is highlighted by the finding that CCN6 protein levels are inversely correlated with Notch1 intracellular activated form (NICD1) in 69.5% of invasive breast carcinomas. These results demonstrate that CCN6 regulates epithelial and mesenchymal states transition and TIC programs, and pinpoint one responsible mechanism.

Usp9x regulates Ets-1 ubiquitination and stability to control NRAS expression and tumorigenicity in melanoma

ETS transcription factors are commonly deregulated in cancer by chromosomal translocation, overexpression or post-translational modification to induce gene expression programs essential in tumorigenicity. Targeted destruction of these proteins may have therapeutic impact. Here we report that Ets-1 destruction is regulated by the deubiquitinating enzyme, Usp9x, and has major impact on the tumorigenic program of metastatic melanoma. Ets-1 deubiquitination blocks its proteasomal destruction and enhances tumorigenicity, which could be reversed by Usp9x knockdown or inhibition. Usp9x and Ets-1 levels are coincidently elevated in melanoma with highest levels detected in metastatic tumours versus normal skin or benign skin lesions. Notably, Ets-1 is induced by BRAF or MEK kinase inhibition, resulting in increased NRAS expression, which could be blocked by inactivation of Usp9x and therapeutic combination of Usp9x and MEK inhibitor fully suppressed melanoma growth. Thus, Usp9x modulates the Ets-1/NRAS regulatory network and may have biologic and therapeutic implications.

MMTV-cre;Ccn6 knockout mice develop tumors recapitulating human metaplastic breast carcinomas

Metaplastic breast carcinoma is an aggressive form of invasive breast cancer with histological evidence of epithelial to mesenchymal transition (EMT). However, the defining molecular events are unknown. Here we show that CCN6 (WISP3), a secreted matricellular protein of the CCN (CYR61/CTGF/NOV) family, is significantly down regulated in clinical samples of human spindle cell metaplastic breast carcinoma. We generated a mouse model of mammary epithelial-specific Ccn6 deletion by developing a floxed Ccn6 mouse which was bred with an MMTV-Cre mouse. Ccn6^fl/fl; MMTV-Cre mice displayed severe defects in ductal branching and abnormal age-related involution compared to littermate controls. Ccn6^fl/fl ;MMTV-Cre mice developed invasive high grade mammary carcinomas with bona fide EMT, histologically similar to human metaplastic breast carcinomas. Global gene expression profiling of Ccn6^fl/fl mammary carcinomas and comparison of orthologous genes with a human metaplastic carcinoma signature revealed a significant overlap of 87 genes (p=5×10⁻¹¹). Among the shared deregulated genes between mouse and human are important regulators of epithelial morphogenesis including Cdh1, Ck19, Cldn3 and 4, Ddr1, and Wnt10a. These results document a causal role for Ccn6 deletion in the pathogenesis of metaplastic carcinomas with histological and molecular similarities with human disease. We provide a platform to study new targets in the diagnosis and treatment of human metaplastic carcinomas, and a new disease relevant model in which to test new treatment strategies.

Dual roles of CCN proteins in breast cancer progression

The tumor microenvironment has a powerful effect on the development and progression of human breast cancer, which may be used therapeutically. Despite efforts to understand the complex role of the tumor microenvironment in breast cancer development, the specific players and their contributions to tumorigenesis need further investigation. The CCN family of matricellular proteins comprises six members (CCN1-6; CYR61, CTGF, NOV, WISP1-3) with central roles in development, inflammation, and tissue repair. CCN proteins also exert functions during pathological processes including fibrosis and cancer by regulating extracellular signals in the cellular environment. Studies have demonstrated that all six CCN proteins exert functions in breast tumorigenesis. Although CCN proteins share a multimodular structure in which most cysteine residues are conserved within structural motifs, they may have opposing functions in breast cancer progression. A better understanding of the functions of each CCN member will assist in the development of specific therapeutic approaches for breast cancer.

CCN family of proteins: critical modulators of the tumor cell microenvironment

The CCN family of proteins consisting of CCN1 (Cyr61), CCN2 (CTGF), CCN3 (NOV), CCN4 (WISP-1), CCN5 (WISP-2) and CCN6 (WISP-3) are considered matricellular proteins operating essentially in the extracellular microenvironment between cells. Evidence has also been gradually building since their first discovery of additional intracellular roles although the major activity is triggered at the cell membrane. The proteins consist of 4 motifs, a signal peptide (for secretion} followed consecutively by the IGFBP, VWC, TSP1 and CT (C-terminal cysteine knot domain) motifs, which signify their potential binding partners and functional connections to a variety of key regulators of physiological processes. With respect to cancer it is now clear that, whereas certain members can facilitate tumor behavior and progression, others can competitively counter the process. It is therefore clear that the net outcome of biological interactions in the matrix and what gets signaled or inhibited can be a function of the interplay of these CCN 1-6 proteins. Because the CCN proteins further interact with other key proteins, like growth factors in the matrix, the balance is not only important but can vary dynamically with the physiological states of tumor cells and the surrounding normal cells. The tumor niche with its many cell players has surfaced as a critical determinant of tumor behavior, invasiveness, and metastasis. It is in this context that CCN proteins should be investigated with the potential of being recognized and validated for future therapeutic approaches.

WISP3 is highly expressed in a subset of colorectal carcinomas with a better prognosis

Outlier genes with marked overexpression in subsets of cancers like ERBB2 have potential for the identification of gene classifiers and therapeutic targets for the appropriate subpopulation. In this study, using the cancer outlier profile analysis strategy, we identified WNT1-inducible-signaling pathway protein 3 (WISP3) as an outlier gene that is highly expressed in a subset of colorectal cancers (CRCs) from The Cancer Genome Atlas dataset. A meta-cancer outlier profile analysis and immunohistochemistry experiment to validate the outlier expression model of WISP3 in CRC was then performed. Our immunohistochemical results indicated that WISP3 was more frequently seen in the small tumors, and there was a significant association between its overexpression with a good prognosis. Furthermore, in the multivariable model, WISP3 outlier expression retained significance for overall survival. In summary, in this study, we identified an outlier gene WISP3 overexpressed in a subset of CRC having less aggressive characteristics and a better prognosis. We suggest WISP3 may provide more accurate and precise information regarding CRC population classification.

Frameshift mutation of WISP3 gene and its regional heterogeneity in gastric and colorectal cancers

WISP3 is involved in many cancer-related processes including epithelial-mesenchymal transition, cell death, invasion, and metastasis and is considered a tumor suppressor. The aim of our study was to find whether WISP3 gene was mutated and expressionally altered in gastric (GC) and colorectal cancers (CRCs). WISP3 gene possesses a mononucleotide repeat in the coding sequence that could be mutated in cancers with high microsatellite instability (MSI-H). We analyzed 79 GCs and 156 CRCs, and found that GCs (8.8%) and CRCs (10.5%) with MSI-H, but not those with microsatellite stable/low MSI, harbored a frameshift mutation. We also analyzed intratumoral heterogeneity (ITH) of the frameshift mutation in 16 CRCs and found that the WISP3 mutation exhibited regional ITH in 25% of the CRCs. In immunohistochemistry, loss of WISP3 expression was identified in 24% of GCs and 21% of CRCs. The loss of expression was more common in those with WISP3 mutation than with wild-type WISP3 and those with MSI-H than with microsatellite stable/low MSI. Our data indicate that WISP3 harbored not only frameshift mutation but also mutational ITH and loss of expression, which together might play a role in tumorigenesis of GC and CRC with MSI-H by inhibiting tumor suppressor functions of WISP3. Our data also suggest that mutation analysis in multiregions is needed for a proper evaluation of mutation status in GC and CRC with MSI-H.

Eyeing the Cyr61/CTGF/NOV (CCN) group of genes in development and diseases: highlights of their structural likenesses and functional dissimilarities

“CCN” is an acronym referring to the first letter of each of the first three members of this original group of mammalian functionally and phylogenetically distinct extracellular matrix (ECM) proteins [i.e., cysteine-rich 61 (CYR61), connective tissue growth factor (CTGF), and nephroblastoma-overexpressed (NOV)]. Although “CCN” genes are unlikely to have arisen from a common ancestral gene, their encoded proteins share multimodular structures in which most cysteine residues are strictly conserved in their positions within several structural motifs. The CCN genes can be subdivided into members developmentally indispensable for embryonic viability (e.g., CCN1, 2 and 5), each assuming unique tissue-specific functions, and members not essential for embryonic development (e.g., CCN3, 4 and 6), probably due to a balance of functional redundancy and specialization during evolution. The temporo-spatial regulation of the CCN genes and the structural information contained within the sequences of their encoded proteins reflect diversity in their context and tissue-specific functions. Genetic association studies and experimental anomalies, replicated in various animal models, have shown that altered CCN gene structure or expression is associated with “injury” stimuli—whether mechanical (e.g., trauma, shear stress) or chemical (e.g., ischemia, hyperglycemia, hyperlipidemia, inflammation). Consequently, increased organ-specific susceptibility to structural damages ensues. These data underscore the critical functions of CCN proteins in the dynamics of tissue repair and regeneration and in the compensatory responses preceding organ failure. A better understanding of the regulation and mode of action of each CCN member will be useful in developing specific gain- or loss-of-function strategies for therapeutic purposes.

Usp5 links suppression of p53 and FAS levels in melanoma to the BRAF pathway

Usp5 is a deubiquitinase (DUB) previously shown to regulate unanchored polyubiquitin (Ub) chains, p53 transcriptional activity and double-strand DNA repair. In BRAF mutant melanoma cells, Usp5 activity was suppressed by BRAF inhibitor (vemurafenib) in sensitive but not in acquired or intrinsically resistant cells. Usp5 knockdown overcame acquired vemurafenib resistance and sensitized BRAF and NRAS mutant melanoma cells to apoptosis initiated by MEK inhibitor, cytokines or DNA-damaging agents. Knockdown and overexpression studies demonstrated that Usp5 regulates p53 (and p73) levels and alters cell growth and cell cycle distribution associated with p21 induction. Usp5 also regulates the intrinsic apoptotic pathway by modulating p53-dependent FAS expression. A small molecule DUB inhibitor (EOAI3402143) phenocopied the FAS induction and apoptotic sensitization of Usp5 knockdown and fully blocked melanoma tumor growth in mice. Overall, our results demonstrate that BRAF activates Usp5 to suppress cell cycle checkpoint control and apoptosis by blocking p53 and FAS induction; all of which can be restored by small molecule-mediated Usp5 inhibition. These results suggest that Usp5 inhibition can provide an alternate approach in recovery of diminished p53 (or p73) function in melanoma and can add to the targeted therapies already used in the treatment of melanoma.

Cancer subclonal genetic architecture as a key to personalized medicine

The future of personalized oncological therapy will likely rely on evidence-based medicine to integrate all of the available evidence to delineate the most efficacious treatment option for the patient. To undertake evidence-based medicine through use of targeted therapy regimens, identification of the specific underlying causative mutation(s) driving growth and progression of a patient's tumor is imperative. Although molecular subtyping is important for planning and treatment, intraclonal genetic diversity has been recently highlighted as having significant implications for biopsy-based prognosis. Overall, delineation of the clonal architecture of a patient's cancer and how this will impact on the selection of the most efficacious therapy remain a topic of intense interest.

Characterization of type III TGF-β receptor expression in invasive breast carcinomas: a potential new marker and target for triple negative breast cancer

Invasive breast carcinomas are heterogeneous and exhibit distinct molecular features and biological behavior. Understanding the underlying molecular events that promote breast cancer progression is necessary to improve treatment and prognostication. TGF-β receptor III (TBR3) is a member of the TGF-β signaling pathway, with functions in cell proliferation and migration in malignancies, including breast cancer. Recent studies propose that TBR3 may function as a tumor suppressor and that its loss may correlate with disease progression. However, there are limited data on the expression of TBR3 in breast cancer in relationship to tumor type, hormonal receptor status and HER-2/neu, and patient outcome. In this study, we investigated the expression of TBR3 in a cohort of 205 primary invasive breast carcinomas in tissue microarrays (TMAs), with comprehensive clinical, pathological and follow- up information. Sections were stained for TBR3 and evaluated for intensity of reactivity based on a 4-tiered scoring system (1 to 4; TBR3 low = scores 1-2; TBR3 high = scores 3-4). Of the 205 invasive carcinomas, 123 were luminal type (95 type A, 28 type B), 8 were HER-2 type, and 62 were triple negative (TN). TBR3 was high in 112 (55 %) and low in 93 (45 %) cases. Low TBR3 was associated with higher histological grade and worse disease free and overall survival, all features of biologically aggressive breast carcinomas. TBR3 was significantly associated with the subtype of breast cancer, as low TBR3 was detected in 95 % of TN compared to 22 % of luminal tumors (p < 0.0001). We discovered a significant association between low TBR3 protein expression, TN breast cancer phenotype, and disease progression. These data suggest that TBR3 loss might be linked to the development of TN breast cancers and pave the way to investigating whether restoring TBR3 function may be a therapeutic strategy against TN breast carcinomas.