Intraductal xenografts model estrogen receptor-positive (ER+) breast cancer dormancy and reveal a critical role for epithelial-mesenchymal transition (EMT) in its establishment

Compared to estrogen receptor-negative (ER-) breast cancer (BC), ER+ BC often manifests with a latent disease that recurs decades after initial diagnosis. The mechanisms governing dormancy and distant recurrence of ER+ tumors remain elusive due to the lack of preclinical models. Here, we compared the tumor progression of ER+ and triple negative (TN; ER-, progesterone receptor and human epidermal growth factor receptor 2-negative) BCs by grafting cell lines- and patient-derived tumor cells into the milk ducts of immunocompromised mice. In the intraductal model, both ER+ and TN BC cells disseminate already during the in situ stage. TN disseminated tumor cells (DTCs) proliferate and form macro-metastases, while DTCs from ER+ BC xenografts have low proliferative indices, are arrested in the G0/G1 phase of the cell cycle, and express the dormancy marker p27. Dormant DTCs display mesenchymal and niche-specific characteristics, as revealed by three-dimensional single cell resolution imaging, and show molecular features of Epithelial-Mesenchymal Transition (EMT) with decreased CDH1, and in-creased ZEB1, ZEB2, and VIM expression levels. Surprisingly, EMT is neither detected in primary tumor cells, nor required for their invasion or dissemination, but is acquired upon their establishment in distant sites. In ex vivo cultures, dormant lung and brain DTCs, revert back to a proliferative state within 3 weeks through a Mesenchymal-Epithelial Transition (MET). In vivo, CDH1 restoration in dormant DTCs overcomes dormancy and increases the growth and proliferation of lung metastases, while decreasing the expression of EMT-transcription factors (MET). We conclude that the intraductal model provides exciting new experimental opportunities to study ER+ BC metastasis dormancy, and reveals that EMT could be exploited therapeutically to promote dormancy and prevent distant recurrence.

Intraductal patient-derived xenografts of estrogen receptor α-positive breast cancer recapitulate the histopathological spectrum and metastatic potential of human lesions

Patrik Aouad, Ayyakkannu Ayyanan, Laura Battista, Cathrin Brisken, Valérian Charles Robert Dormoy, Maryse Fiche, Valentina Scabia, Georgios Sflomos

Estrogen receptor α-positive (ER-positive) or 'luminal' breast cancers were notoriously difficult to establish as patient-derived xenografts (PDXs). We and others recently demonstrated that the microenvironment is critical for ER-positive tumor cells; when grafted as single cells into milk ducts of NOD Scid gamma females, >90% of ER-positive tumors can be established as xenografts and recapitulate many features of the human disease in vivo. This intraductal approach holds promise for personalized medicine, yet human and murine stroma are organized differently and this and other species specificities may limit the value of this model. Here, we analyzed 21 ER-positive intraductal PDXs histopathologically. We found that intraductal PDXs vary in extent and define four histopathological patterns: flat, lobular, in situ and invasive, which occur in pure and combined forms. The intraductal PDXs replicate earlier stages of tumor development than their clinical counterparts. Micrometastases are already detected when lesions appear in situ. Tumor extent, histopathological patterns and micrometastatic load correlate with biological properties of their tumors of origin. Our findings add evidence to the validity of the intraductal model for in vivo studies of ER-positive breast cancer and raise the intriguing possibility that tumor cell dissemination may occur earlier than currently thought. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

2018

Hormone receptor signaling in estrogen receptor positive breast cancer

Valentina Scabia

Estrogen receptor (ER) and progesterone receptor (PR) signaling tightly interact in controlling postnatal breast development and impinge on breast carcinogenesis. PR is a direct transcriptional target of ER signaling and ER and PR bind closely to DNA and interact physically. The clinical significance of their molecular interactions remains unclear as most studies are done using simplistic or non-physiological models. Here, we exploit intraductal xenografts of ER+ breast cancer (BC) cell lines and patient-derived tumor cells to study ER and PR signaling in physiological endocrine settings. Relative tumor growth stimulation by 17-Î²-estradiol (E2), progesterone (P4) and the combination of the two is cell line and PDX-dependent. Across all models both ER and PR are required for tumor growth. Ectopic PR expression restores growth in genetically or pharmacologically ER-ablated tumor cells and induces ER-dependent gene expression in MCF7 xenografts showing that PR mediates ER function. PR stimulates tumor growth and metastasis independent of ligand. In PDXs PR induction correlates with tumor growth. Our findings show differential hormone sensitivities of luminal BC and reveal PR as essential for hormone receptor positive tumor progression and suggest PR degradation as a therapeutic option for ER BCs.

EPFL2019

A Preclinical Model for ERα-Positive Breast Cancer Points to the Epithelial Microenvironment as Determinant of Luminal Phenotype and Hormone Response

Ayyakkannu Ayyanan, Laura Battista, Cathrin Brisken, Valérian Charles Robert Dormoy, Maryse Fiche, Valentina Scabia, Georgios Sflomos

Seventy-five percent of breast cancers are estrogen receptor α positive (ER(+)). Research on these tumors is hampered by lack of adequate in vivo models; cell line xenografts require non-physiological hormone supplements, and patient-derived xenografts (PDXs) are hard to establish. We show that the traditional grafting of ER(+) tumor cells into mammary fat pads induces TGFβ/SLUG signaling and basal differentiation when they require low SLUG levels to grow in vivo. Grafting into the milk ducts suppresses SLUG; ER(+) tumor cells develop, like their clinical counterparts, in the presence of physiological hormone levels. Intraductal ER(+) PDXs are retransplantable, predictive, and appear genomically stable. The model provides opportunities for translational research and the study of physiologically relevant hormone action in breast carcinogenesis.

Elsevier2016