αE-catenin is a candidate tumor suppressor for the development of E-cadherin-expressing lobular-type breast cancer.

Although mutational inactivation of E-cadherin (CDH1) is the main driver of invasive lobular breast cancer (ILC), approximately 10-15% of all ILCs retain membrane-localized E-cadherin despite the presence of an apparent non-cohesive and invasive lobular growth pattern. Given that ILC is dependent on constitutive actomyosin contraction for tumor development and progression, we used a combination of cell systems and in vivo experiments to investigate the consequences of α-catenin (CTNNA1) loss in the regulation of anchorage independence of non-invasive breast carcinoma. We found that inactivating somatic CTNNA1 mutations in human breast cancer correlated with lobular and mixed ducto-lobular phenotypes. Further, inducible loss of α-catenin in mouse and human E-cadherin-expressing breast cancer cells led to atypical localization of E-cadherin, a rounded cell morphology, and anoikis resistance. Pharmacological inhibition experiments subsequently revealed that, similar to E-cadherin-mutant ILC, anoikis resistance induced by α-catenin loss was dependent on Rho/Rock-dependent actomyosin contractility. Finally, using a transplantation-based conditional mouse model, we demonstrate that inducible inactivation of α-catenin instigates acquisition of lobular features and invasive behavior. We therefore suggest that α-catenin represents a bona fide tumor suppressor for the development of lobular-type breast cancer and as such provides an alternative event to E-cadherin inactivation, adherens junction (AJ) dysfunction, and subsequent constitutive actomyosin contraction. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Intraductal cisplatin treatment in a BRCA-associated breast cancer mouse model attenuates tumor development but leads to systemic tumors in aged female mice.

BRCA deficiency predisposes to the development of invasive breast cancer. In BRCA mutation carriers this risk can increase up to 80%. Currently, bilateral prophylactic mastectomy and prophylactic bilateral salpingo-oophorectomy are the only preventive, albeit radical invasive strategies to prevent breast cancer in BRCA mutation carriers. An alternative non-invasive way to prevent BRCA1-associated breast cancer may be local prophylactic treatment via the nipple. Using a non-invasive intraductal (ID) preclinical intervention strategy, we explored the use of combined cisplatin and poly (ADP)-ribose polymerase 1 (PARP1) inhibition to prevent the development of hereditary breast cancer. We show that ID cisplatin and PARP-inhibition can successfully ablate mammary epithelial cells, and this approach attenuated tumor onset in a mouse model of Brca1-associated breast cancer from 153 to 239 days. Long-term carcinogenicity studies in 150 syngeneic wild-type mice demonstrated that tumor incidence was increased in the ID treated mammary glands by 6.3% due to systemic exposure to cisplatin. Although this was only evident in aged mice (median age = 649 days), we conclude that ID cisplatin treatment only presents a safe and feasible local prevention option if systemic exposure to the chemotherapy used can be avoided.

Methylation biomarkers for pleomorphic lobular breast cancer - a short report.

BACKGROUND: Pleomorphic invasive lobular cancer (pleomorphic ILC) is a rare variant of ILC that is characterized by a classic ILC-like growth pattern combined with an infiltrative ductal cancer (IDC)-like high nuclear atypicality. There is an ongoing discussion whether pleomorphic ILC is a dedifferentiated form of ILC or in origin an IDC with a secondary loss of cohesion. Since gene promoter hypermethylation is an early event in breast carcinogenesis and thus may provide information on tumor progression, we set out to compare the methylation patterns of pleomorphic ILC, classic ILC and IDC. In addition, we aimed at analyzing the methylation status of pleomorphic ILC. METHODS: We performed promoter methylation profiling of 24 established and putative tumor suppressor genes by methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) analysis in 20 classical ILC, 16 pleomorphic ILC and 20 IDC cases. RESULTS: We found that pleomorphic ILC showed relatively low TP73 and MLH1 methylation levels and relatively high RASSF1A methylation levels compared to classic ILC. Compared to IDC, pleomorphic ILC showed relatively low MLH1 and BRCA1 methylation levels. Hierarchical cluster analysis revealed a similar methylation pattern for pleomorphic ILC and IDC, while the methylation pattern of classic ILC was different. CONCLUSION: This is the first report to identify TP73, RASSF1A, MLH1 and BRCA1 as possible biomarkers to distinguish pleomorphic ILC from classic ILC and IDC.

Nuclear localization of the transcriptional coactivator YAP is associated with invasive lobular breast cancer.

BACKGROUND: Yes Associated Protein (YAP) has been implicated in the control of organ size by regulating cell proliferation and survival. YAP is a transcriptional coactivator that controls cellular responses through interaction with TEAD transcription factors in the nucleus, while its transcriptional functions are inhibited by phosphorylation-dependent translocation to the cytosol. YAP overexpression has been associated with different types of cancer, such as lung, skin, prostate, ovary and liver cancer. Recently, YAP was linked to E-cadherin-dependent regulation of contact inhibition in breast cancer cells. RESULTS: In this study we examined YAP protein expression and cellular localization in 237 cases of human invasive breast cancer by immunohistochemistry and related its expression to clinicopathological features and E-cadherin expression. We observed that invasive lobular carcinoma is characterized by higher expression levels of both nuclear and cytosolic YAP (p < 0.001). Nuclear YAP expression did not associate with other variables such as lymph node involvement, tumor grade, tumor size, mitotic activity or the molecular sub-types of invasive breast cancer. We observed that high nuclear and cytosolic YAP expression are associated with the E-cadherin deficient breast cancer subtype ILC (p < 0.001) and cell lines derived from human breast cancers and conditional mouse models of human lobular breast cancer. CONCLUSIONS: Since our data indicate that nuclear YAP localization is more common in breast cancers lacking functional adherens junctions, it suggests that YAP-mediated transcription may be involved in the development and progression of invasive lobular breast cancer.

Loss of p120-catenin induces metastatic progression of breast cancer by inducing anoikis resistance and augmenting growth factor receptor signaling.

Metastatic breast cancer remains the chief cause of cancer-related death among women in the Western world. Although loss of cell-cell adhesion is key to breast cancer progression, little is known about the underlying mechanisms that drive tumor invasion and metastasis. Here, we show that somatic loss of p120-catenin (p120) in a conditional mouse model of noninvasive mammary carcinoma results in formation of stromal-dense tumors that resemble human metaplastic breast cancer and metastasize to lungs and lymph nodes. Loss of p120 in anchorage-dependent breast cancer cell lines strongly promoted anoikis resistance through hypersensitization of growth factor receptor (GFR) signaling. Interestingly, p120 deletion also induced secretion of inflammatory cytokines, a feature that likely underlies the formation of the prometastatic microenvironment in p120-negative mammary carcinomas. Our results establish a preclinical platform to develop tailored intervention regimens that target GFR signals to treat p120-negative metastatic breast cancers.

Cytosolic p120-catenin regulates growth of metastatic lobular carcinoma through Rock1-mediated anoikis resistance.

Metastatic breast cancer is the major cause of cancer-related death among women in the Western world. Invasive carcinoma cells are able to counteract apoptotic signals in the absence of anchorage, enabling cell survival during invasion and dissemination. Although loss of E-cadherin is a cardinal event in the development and progression of invasive lobular carcinoma (ILC), little is known about the underlying mechanisms that govern these processes. Using a mouse model of human ILC, we show here that cytosolic p120-catenin (p120) regulates tumor growth upon loss of E-cadherin through the induction of anoikis resistance. p120 conferred anchorage independence by indirect activation of Rho/Rock signaling through interaction and inhibition of myosin phosphatase Rho-interacting protein (Mrip), an antagonist of Rho/Rock function. Consistent with these data, primary human ILC samples expressed hallmarks of active Rock signaling, and Rock controlled the anoikis resistance of human ILC cells. Thus, we have linked loss of E-cadherin - an initiating event in ILC development - to Rho/Rock-mediated control of anchorage-independent survival. Because activation of Rho and Rock are strongly linked to cancer progression and are susceptible to pharmacological inhibition, these insights may have clinical implications for the development of tailor-made intervention strategies to better treat invasive and metastatic lobular breast cancer.

Controlling cardiomyocyte survival.

Gradually the distinction between signalling pathways originally believed to be specific for either hypertrophy, cell cycle control, apoptosis and cell survival are fading. The subtle variations in stimuli to a cell and the microenvironment will determine cell fate. In cardiomyocytes the entrance into the cell cycle is efficiently blocked. Therefore attention has focused on pathways involved in hypertrophy to assess effects in ischaemic models and vice versa. Interventions at different levels have been shown to be cardiomyocyte protective. Various growth factors (including IGF1 and FGF1,2) have shown to prevent or delay cardiomyocyte loss in and ex vivo. Similar results have been reported for downstream interventions in the signalling pathways. Strong effects after MAPK activation have been shown in gene targeted mice. Especially constitutive activation of the ERK proteins prevents ischemic damage of the heart with conservation of left ventricular function. Evidence for a key role of nuclear Akt in preventing apoptosis is accumulating from various genetic and pharmacological sources. Development of techniques to measure the level of cardiomyocyte death depends on further improvements in molecular imaging in mouse and human. In addition to studying cardiomyocyte cell death, it is crucial to measure myocardial function. Whether hypertrophy following ischaemia is adaptive or maladaptive and whether all apoptosis is detrimental will have to be determined by assessment of left ventricular function through invasive and noninvasive methods.