Metaplastic carcinoma show different expression pattern of YAP compared to triple-negative breast cancer

Epithelial to mesenchymal transition (EMT) in metaplastic breast cancer and phyllodes breast tumors

Epithelial-mesenchymal transition (EMT), a transdifferentiation program whereby epithelial cells acquire mesenchymal phenotype, is essential during embryonic development. EMT has also been implicated in cancer progression by conferring migratory and metastatic potential, as well as cell plasticity and stem cell like traits, to cancer cells. Metaplastic breast carcinoma (MBC) is a rare aggressive type of breast cancer characterized by the presence of heterologous elements, typically by the existence of epithelial and mesenchymal components. Phyllodes tumors (PTs) are uncommon fibroepithelial neoplasms consisting of epithelial and mesenchymal elements. Although various hypotheses have been proposed on the pathogenesis of these biphasic tumors, there is growing evidence supporting the theory that PTs and MBC could both correlate with cancer related EMT. This review summarizes the existing literature on the emerging role of EMT in the pathogenesis of MBC and PTs. Both malignant PTs and MBC are characterized by poor prognosis. Therefore, several anti-EMT targeting strategies such as blocking upstream signaling pathways, targeting the molecular drivers of EMT and targeting mesenchymal cells and the extracellular matrix, could potentially represent a promising therapeutic approach for patients suffering from these aggressive neoplasms.

Expression of markers of stem cell characteristics, epithelial-mesenchymal transition, basal-like phenotype, proliferation, and androgen receptor in metaplastic breast cancer and their prognostic impact

BACKGROUND

Metaplastic breast cancer (MpBC) is a heterogeneous subtype of invasive mammary carcinoma associated with epithelial-mesenchymal transition (EMT) and cancer stem cell characteristics. Data regarding prognostic markers and potentially actionable targets for therapy are still limited. The present study aimed to characterize the immunohistochemical landscape of this rare malignancy and to identify potential prognostic factors and targets for therapy.

MATERIAL AND METHODS

A total of 75 patients diagnosed with MpBC over a 15-year period were included in the study. We performed immunohistochemical analyses for Ki-67 (MIB-1), epidermal growth factor receptor (EGFR), cytokeratin 5/6, vimentin, CD44, and androgen receptor (AR) and correlated their expression with clinicopathologic features and clinical outcomes. The p-values for survival analyses were corrected for multiple testing (threshold 0.01).

RESULTS

Most tumors expressed CK5/6 (73%), EGFR (59%), CD44 (81%), and vimentin (87%). Eighty-nine percent had a high Ki-67 index. Eighty-four percent were classified as basal-like (CK 5/6 or EGFR positive). AR was expressed in 21% of the tumors. The basal-like phenotype was significantly (p = 0.009) associated with inferior disease-free (DFS) and breast-cancer-specific overall survival (BCOS) with borderline significance (p = 0.01). In addition, a low Ki-67 index was associated with improved DFS (p = 0.033) and BCOS (p = 0.03).

CONCLUSION

Most MpBCs express basal markers (CK5/6, EGFR), epithelial-mesenchymal transition marker vimentin, and the stem cell marker CD44. Expression of basal-like markers was significantly related to inferior DFS. All the 11 patients with a lack of expression of basal markers survived without relapse.

Increased YAP1 expression is significantly associated with breast cancer progression, metastasis and poor survival

YAP1 plays a key role as a transcriptional coactivator in the Hippo pathway. Based on conflicting reports regarding YAP1 function in cancer, this study discerned its role in breast carcinogenesis. First, a systematic review of salient breast cancer studies targeting YAP1 dysregulation was performed. Additionally, freshly excised tumor specimens of approximately 200 breast cancer patients were processed for quantification of YAP1 expression at mRNA and protein levels using quantitative PCR and immunohistochemistry, respectively. YAP1 expression was nine folds higher in tumors versus controls and significantly associated with metastasis (p < 0.05) and poor survival in Pakistani breast cancer patients. These findings establish the role of YAP1 overexpression in tumorigenesis and metastasis. Hence, YAP1 inhibition may be considered a possible therapeutic strategy.

Effects of Quinacrine on Expression of Hippo signaling Pathway Components (LATS1, LATS2, and YAP) in Human Breast Cancer Stem Cells

OBJECTIVE

The Hippo signaling pathway has important role in the pathogenesis of some tumors. Breast cancer is the most prevalent cancer among females in the world. In recent years, various articles referred to inhibiting effect of quinacrine, a derivative of 9-aminoacridine, on the growth of several types of cancer cells. In this study, we evaluated the effect of quinacrine on expression of LATS1, LATS2, and YAP genes of the Hippo signaling pathway and YAP level in human breast cancer stem cells (MDA-MB 231 cell line). This cell line of breast cancer expresses the triple negative characteristics.

METHODS

MDA-MB 231 cells was treated with 0.5 µM of quinacrine for 3 days. The dose was selected using MTT assays. The expression of genes was quantified by Real-time PCR. The protein expression was performed by Western blotting. Significance of observations were checked by means of Mann-Whitney test using p.

Clinicopathologic significance of nuclear HER4 and phospho-YAP(S127) in human breast cancers and matching brain metastases

Background

Human epidermal growth factor receptor-4 (HER4) and yes-associated protein-1 (YAP) are candidate therapeutic targets in oncology. YAP's transcriptional coactivation function is modulated by the HER4 intracellular domain (HER4-ICD) in vitro, but the clinical relevance of this has not been established. This study investigated the potential for targeting the HER4-YAP pathway in brain metastatic breast cancer.

Methods

We performed immuno-phenotypic profiling of pathway markers in a consecutive breast cancer series with 25 years of clinical follow up (n = 371), and patient-matched breast and metastatic brain tumours (n = 91; 30 pairs).

Results

Membrane localisation of phospho-HER4 [pHER4(Y¹¹⁶²)] was infrequent in primary breast cancer, but very frequent in brain metastases (5.9% versus 75% positive), where it was usually co-expressed with pHER3(Y¹²⁸⁹) (p < 0.05). The presence of YAP in tumour cell nuclei was associated directly with nuclear pERK5(T²¹⁸/Y²¹⁰) (p = 0.003). However, relationships with disease-specific survival depended on oestrogen receptor (ER) status. Nuclear pYAP(S¹²⁷) was associated with smaller, good prognostic ER+ breast tumours (log-rank hazard-ratio 0.53; p = 9.6E^-03), but larger, poor prognostic triple-negative cancers (log-rank hazard-ratio 2.78; p = 1.7E^-02), particularly when co-expressed with nuclear HER4-ICD (p = 0.02). This phenotype was associated with stemness and mitotic instability markers (vimentin, SOX9, ID1, SPAG5, TTK, geminin; p < 0.05). YAP expression in brain metastases was higher than matched primary tumours; specifically, nuclear pYAP(S¹²⁷) in ER-negative cases (p < 0.05). Nuclear YAP was detected in ~70% of ER-negative, HER4-activated brain metastases.

Discussion

Our findings suggest that the canonical-mechanism where Hippo pathway-mediated phosphorylation of YAP ostensibly excludes it from the nucleus is dysfunctional in breast cancer. The data are consistent with pYAP(S¹²⁷) having independent transcriptional functions, which may include transducing neuregulin signals in brain metastases. Consistent with mechanistic studies implicating it as an ER co-factor, nuclear pYAP(S¹²⁷) associations with breast cancer clinical outcomes were dependent on ER status.

Conclusion

Preclinical studies investigating HER4 and nuclear YAP combination therapy strategies are warranted.

The role of radiotherapy in metaplastic breast cancer: a propensity score-matched analysis of the SEER database

BACKGROUND

Only few studies, with small patient cohorts, have evaluated the effect of radiotherapy (RT) for metaplastic breast cancer (MBC). Hence, it is important to investigate the role of RT in MBC survival using a large population-database.

METHODS

A retrospective cohort study using the Surveillance, Epidemiology, and End Results (SEER) from 1973 to 2015 was performed. We compared MBC patients with or without RT for overall survival (OS) and breast cancer-specific survival (BCSS) using univariate and multivariate Cox proportional hazard regressions before and after propensity score matching (PSM).

RESULTS

From a total of 2267 patients diagnosed with MBC between 1998 and 2015, 1086 (47.9%) received RT. In the multivariate analysis before PSM, RT provided a better OS (HR 0.73; 95% CI 0.61-0.88; p = 0.001) and BCSS (HR 0.71; 95% CI 0.58-0.88; p = 0.002). Multivariate analyses after PSM (n = 1066) confirmed that patients receiving RT (n = 506) survived longer than those without RT (OS, HR 0.64; 95% CI 0.51-0.80; p < 0.001 and BCSS, HR 0.64; 95% CI 0.50-0.83; p = 0.001). A longer OS was observed when RT was given to older patients (p = 0.001) and in case of large tumor size (p = 0.002). Intriguingly, patients with N0 stage showed better OS after RT (HR 0.69, P = 0.012).

CONCLUSIONS

Our findings support the beneficial effect of RT for MBC patients. In particular, older patients or with large tumor size have a greater survival benefit from RT. In conclusion, we have assessed the importance of the use of RT in MBC as survival factor and this could lead to the development of guidelines for this rare sub-type of tumors.

Dysregulation of the Hippo pathway signaling in aging and cancer

Human beings are facing emerging degenerative and cancer diseases, in large part, as a consequence of increased life expectancy. In the near future, researchers will have to put even more effort into fighting these new challenges, one of which will be prevention of cancer while continuing to improve the aging process through this increased life expectancy. In the last few decades, relevance of the Hippo pathway on cancer has become an important study since it is a major regulator of organ size control and proliferation. However, its deregulation can induce tumors throughout the body by regulating cell proliferation, disrupting cell polarity, releasing YAP and TAZ from the Scribble complexes and facilitating survival gene expression via activation of TEAD transcription factors. This pathway is also involved in some of the most important mechanisms that control the aging processes, such as the AMP-activated protein kinase and sirtuin pathways, along with autophagy and oxidative stress response/antioxidant defense. This could be the link between two tightly connected processes that could open a broader range of targeted molecular therapies to fight aging and cancer. Therefore, available knowledge of the processes involved in the Hippo pathway during aging and cancer must necessarily be well understood.

WW-Domain Containing Protein Roles in Breast Tumorigenesis

Protein-protein interactions are key factors in executing protein function. These interactions are mediated through different protein domains or modules. An important domain found in many different types of proteins is WW domain. WW domain-containing proteins were shown to be involved in many human diseases including cancer. Some of these proteins function as either tumor suppressor genes or oncogenes, while others show dual identity. Some of these proteins act on their own and alter the function(s) of specific or multiple proteins implicated in cancer, others interact with their partners to compose WW domain modular pathway. In this review, we discuss the role of WW domain-containing proteins in breast tumorigenesis. We give examples of specific WW domain containing proteins that play roles in breast tumorigenesis and explain the mechanisms through which these proteins lead to breast cancer initiation and progression. We discuss also the possibility of using these proteins as biomarkers or therapeutic targets.

A time for YAP1: Tumorigenesis, immunosuppression and targeted therapy

YAP1 is one of the most important effectors of the Hippo pathway and has crosstalk with other cancer promoting pathways. YAP1 contributes to cancer development in various ways that include promoting malignant phenotypes, expansion of cancer stem cells and drug resistance of cancer cells. Because pharmacologic or genetic inhibition of YAP1 suppresses tumor progression and increases the drug sensitivity, targeting YAP1 may open a fertile avenue for a novel therapeutic approach in relevant cancers. Recent enormous studies have established the efficacy of immunotherapy, and several immune checkpoint blockades are in clinical use or in the phase of development to treat various cancer types. Immunosuppression in the tumor microenvironment (TME) induced by cancer cells, immune cells and associated stromal cells promotes tumor progression and causes drug resistance. Accumulated evidences of scientific efforts from the last few years suggest that YAP1 influences macrophages, myeloid-derived suppressor cells and regulatory T-cells to facilitate immunosuppressive TME. Although the underlying mechanisms is not clearly discerned, it is evident that YAP1 activating pathways in different cellular components induce immunosuppressive TME. In this review, we summarize the evidences involved in the dual roles of YAP1 in cancer development and immunosuppression in the TME. We also discuss the possibility of YAP1 as a novel therapeutic target.

The role of Hippo signal pathway in breast cancer metastasis

The Hippo pathway is a novel and highly conserved mammalian signaling pathway. Mutations and altered expression of core Hippo pathway components promote the migration, invasion, malignancy, and chemotherapy resistance of breast cancer cells. In cancer metastasis, tumor cells must detach from the primary tumor, invade surrounding tissue, and enter and survive in a foreign microenvironment. The metastatic potential of breast cancer is closely related to individual patient genetic profile. Nevertheless, the exact molecular mechanism that regulates the Hippo pathway in breast cancer metastasis is yet to be fully elucidated. This article discusses the function and regulation of the Hippo pathway, with focus given to its role in the context of breast cancer metastasis.

Early and Locally Advanced Metaplastic Breast Cancer: Presentation and Survival by Receptor Status in Surveillance, Epidemiology, and End Results (SEER) 2010-2014

BACKGROUND

Metaplastic breast cancer (MBC) is a rare disease subtype characterized by an aggressive clinical course. MBC is commonly triple negative (TN), although hormone receptor (HR) positive and human epidermal growth receptor 2 (HER2) positive cases do occur. Previous studies have reported similar outcomes for MBC with regard to HR status. Less is known about outcomes for HER2 positive MBC.

MATERIALS AND METHODS

Surveillance, Epidemiology, and End Results Program data were used to identify women diagnosed 2010-2014 with MBC or invasive ductal carcinoma (IDC). Kaplan-Meier curves estimated overall survival (OS) and multivariate Cox models were fitted. For survival analyses, only first cancers were included, and 2014 diagnoses were excluded to allow for sufficient follow-up.

RESULTS

Our MBC sample included 1,516 women. Relative to women with IDC, women with MBC were more likely to be older (63 vs. 61 years), black (16.0% vs. 11.1%), and present with stage III disease (15.6% vs. 10.8%). HER2 positive and HER2 negative/HR positive MBC tumors represented 5.2% and 23.0% of cases. For MBC overall, 3-year OS was greatest for women with HER2 positive MBC (91.8%), relative to women with TN (75.4%) and HER2 negative/HR positive MBC (77.1%). This difference was more pronounced for stage III MBC, for which 3-year OS was 92.9%, 47.1%, and 42.2% for women with HER2 positive, TN, and HER2 negative/HR positive MBC, respectively. A multivariate Cox model of MBC demonstrated that HER2 positive tumors (relative to TN) were associated with improved survival (hazard ratio = 0.32, 95% confidence interval [CI] 0.13-0.79). In a second Cox model of exclusively HER2 positive tumors, OS did not differ between MBC and IDC disease subtypes (hazard ratio = 1.16, 95% CI 0.48-2.81).

CONCLUSION

In this contemporary, population-based study of women with MBC, HER2 but not HR status was associated with improved survival. Survival was similar between HER2 positive MBC and HER2 positive IDC. This suggests HER2 positive MBC is responsive to HER2-directed therapy, a finding that may offer insights for additional therapeutic approaches to MBC.

IMPLICATIONS FOR PRACTICE

This population-based study reports recent outcomes, by receptor status, for women with metaplastic breast cancer. Survival in metaplastic breast cancer is not impacted by hormone receptor status. To the authors' knowledge, this is the first report indicating that women with human epidermal growth receptor 2 (HER2) positive metaplastic breast cancer have survival superior to women with HER2 negative metaplastic breast cancer and survival similar to women with HER2 positive invasive ductal carcinoma. This information can be used for counseling patients diagnosed with metaplastic breast cancer. Further understanding of HER2 positive metaplastic breast cancer could offer insights for the development of therapeutic approaches to metaplastic breast cancer more broadly.

YAP1-TEAD1-Glut1 axis dictates the oncogenic phenotypes of breast cancer cells by modulating glycolysis

Altered energy metabolism is a universal property of most cancer cells. The Hippo signaling pathway and its principal downstream effector YAP1 are responsible for tissue homeostasis including organ size, cell proliferation, apoptosis, and differentiation. Dysregulation of the Hippo pathway leads to the activation of YAP1 and further culminates in the development of multiple human cancers. In this study, by loss-of-function assay, we demonstrated that YAP1 contributed to the glycolytic phenotype of breast cancer cells. Knockdown of YAP1 inhibited the extracellular acidification rates, glucose consumption, and lactate production of breast cancer cells. Moreover, YAP1 interacted with TEAD1, exerted their transcriptional control of the functional target, glucose transporter 1 (Glut1). Overexpression of Glut1 restored the inhibitory effects of YAP1 knockdown on glycolysis as demonstrated by glucose consumption and lactate production. Suppression of glycolysis by deprivation of glucose largely compromised the oncogenic roles of YAP1 on cell proliferation, apoptosis, and invasive potential. Taken together, our data identify a novel role of YAP1-TEAD1 pathway in cancer energy metabolism.

Expression of YES-associated protein (YAP) and its clinical significance in breast cancer tissues

The transcriptional co-activator YES-associated protein (YAP) has been reported to act as both an oncogene and tumor suppressor in breast cancers. In this study, we evaluated YAP expression immunohistochemically in 324 breast cancer tissues and correlated the expression with clinicopathological findings and patient survival data. Additionally, we reviewed the literature to clarify the role of YAP in breast cancer. We detected YAP, estrogen receptor, progesterone receptor (PR), and human epidermal growth receptor-2 (HER2) expression and a Ki67 labeling index >20% in 53.4%, 49.0%, 45.0%, 28.3%, and 57.4% of invasive ductal carcinoma tissues, respectively. YAP is mainly localized within the tumor cell nuclei, and its expression was associated with the PR status and luminal A subtype. YAP expression also inversely correlated with the HER2 and Ki67 levels and lymph node metastasis. Kaplan-Meier curves revealed associations of YAP expression with favorable disease-free survival (DFS) and overall survival in patients with luminal A breast cancer and with favorable DFS association among patients with invasive ductal carcinoma, luminal B (HER2-), and luminal B (HER2+) breast cancers. A multivariate Cox analysis revealed that YAP expression and PR status were independent favorable predictors of DFS and overall survival, respectively, among patients with breast cancer, whereas tumor-node-metastasis stage and an old age were independent predictors of a poor DFS. Our results, together with the literature review findings, suggest that YAP could be a prognostic marker in patients with breast cancer.

Deregulation of the Hippo pathway in mouse mammary stem cells promotes mammary tumorigenesis

The Hippo-YAP pathway mediates organ size control, contact inhibition, and tumorigenesis. It is a kinase cascade that inhibits the nuclear localization and transcriptional activities of YAP and TAZ. E-cadherin, cell junctions, polarity proteins, and the merlin/NF2 tumor suppressor activate the pathway to inhibit YAP/TAZ activity, while growth factor signaling inhibits the pathway to activate YAP/TAZ in the nucleus. We examined its role in the development of mouse mammary glands and tumor formation using gland reconstitution by transplantation of genetically modified mammary stem cells (MaSCs). Knockdown of YAP and TAZ with shRNA in MaSCs did not inhibit gland reconstitution. In contrast, knockdown of β-catenin blocked gland reconstitution, consistent with the known role of Wnt signaling in mammary gland development. However, we find that Hippo signaling is involved in mammary tumor formation. Expression of a constitutively active form of YAP caused rapid formation of large tumors. Moreover, knockdown of YAP/TAZ slowed the development of tumors in polyoma middle T transgenic mice, a well-studied mammary tumor model involving activation of several signaling pathways. YAP accumulated in nuclei of mammary glands in ErbB2/EGFR-transgenic mice, suggesting that EGFR signaling affects YAP in vivo similar to cell culture. ErbB2/EGFR-transgenic mice develop mammary tumors in 7-8 months, but surprisingly, MaSCs from these mice did not form tumors when transplanted into host mice. Nonetheless, expression of dominant-negative Lats, which inhibits Hippo signaling, leads to tumor formation in ErbB2-transgenic mice, suggesting that Hippo signaling is involved in EGFR-induced mammary tumorigenesis.

Management and Outcomes in Metaplastic Breast Cancer

Metaplastic breast cancer (MBC) constitutes a rare clinical entity with special clinicopathologic, immunohistochemical, and molecular features. Resistance to systemic therapies, whether chemotherapy or hormonal therapy, is among its main characteristics, which in turn explains the poor prognosis and renders its management a challenge. Thus, the scope of the present review is to discuss the current therapeutic strategies for MBC in clinical practice and the corresponding outcomes and to suggest possible directions for future research. Potential novel targeted therapies could provide a hope for better outcomes but limited data are available owing to the rarity of MBC. As knowledge accumulates on the pathogenesis and genetic characteristics of MBC, emphasis should be given to the implementation of more targeted treatments, which will allow more efficient and individualized management of the disease.

Topographic expression of the Hippo transducers TAZ and YAP in triple-negative breast cancer treated with neoadjuvant chemotherapy

Background

The Hippo signaling acts as a tumor-suppressor pathway that negatively regulates TAZ and YAP. Increasing evidence supports the activation of TAZ and YAP in breast cancer. Moreover, the Hippo pathway is involved in the biology of non-neoplastic cells residing in the tumor microenvironment. On this basis, we herein assessed TAZ and YAP in triple-negative breast cancer and its surrounding microenvironemnt in order to investigate their impact on pathological complete response (pCR) and tumor recurrence.

Methods

Sixty-one triple-negative breast cancer patients treated with neoadjuvant chemotherapy were retrospectively evaluated. TAZ and YAP were assessed by immunohistochemistry and classified as positive or negative according to the percentage of tumor-expressing cells, cellular localization, and staining intensity. TAZ and YAP expression was also evaluated in non-lymphocytic stromal cells, tumor-infiltrating lymphocytes (TILs) and endothelial cells. The Pearson’s Chi-squared test of independence was used to test the association between TAZ/YAP and clinical-molecular factors. A multivariate logistic regression model was generated to identify variables impacting pCR. The Kaplan-Meier method and the log-rank test were used for estimating and comparing survival curves. Cox proportional regression models were built to evaluate the risk of recurrence for the variables considered. Internal validation was carried out with a re-sampling without replacement method.

Results

We did not observe any impact on pCR rate when TAZ and YAP were addressed singularly. Conversely, the combined expression of YAP in tumor cells and non-lymphocytic stromal cells was an independent predictor of reduced pCR rate in the multivariate model (OR 7.13, 95 % CI: 1.23–41.41, p = 0.029). Next, the combined expression of TAZ and YAP was associated with shorter disease-free survival (DFS) in multivariate analysis (HR 3.07, 95 % CI: 1.24–7.61, p = 0.016). The robustness of these findings were internally validated.

Conclusions

The combined expression of YAP in TNBC cells and in the surrounding stroma seems to be associated with a decreased likelihood to achieve pCR. Conversely, the combined expression of TAZ and YAP in tumor cells conferred poor survival outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0338-7) contains supplementary material, which is available to authorized users.

The Hippo transducers TAZ and YAP in breast cancer: oncogenic activities and clinical implications

The Hippo signalling is emerging as a tumour suppressor pathway whose function is regulated by an intricate network of intracellular and extracellular cues. Defects in the signal cascade lead to the activation of the Hippo transducers TAZ and YAP. Compelling preclinical evidence showed that TAZ/YAP are often aberrantly engaged in breast cancer (BC), where their hyperactivation culminates into a variety of tumour-promoting functions such as epithelial-to-mesenchymal transition, cancer stem cell generation and therapeutic resistance. Having acquired a more thorough understanding in the biology of TAZ/YAP, and the molecular outputs they elicit, has prompted a first wave of exploratory, clinically-focused analyses aimed at providing initial hints on the prognostic/predictive significance of their expression. In this review, we discuss oncogenic activities linked with TAZ/YAP in BC, and we propose clinical strategies for investigating their role as biomarkers in the clinical setting. Finally, we address the therapeutic potential of TAZ/YAP targeting and the modalities that, in our opinion, should be pursued in order to further study the biological and clinical consequences of their inhibition.

[Modification of a micromethod for determining leukocyte migration inhibition and its significance in oncological patients]

Breast cancer stem cells (BCSC) have been implicated in tumor initiation, progression, metastasis, recurrence, and resistance to therapy. The origins of BCSCs remain controversial due to tumor heterogeneity and the presence of such small side populations for study, but nonetheless, cell surface markers and their correlation with BCSC functionality continue to be identified. BCSCs are driven by persistent activation of developmental pathways, such as Notch, Wnt, Hippo, and Hedgehog and new treatment strategies that are aimed at these pathways are in preclinical and clinical development.