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

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.

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

Patrik Aouad

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.

EPFL2021

The Cell Differentiation Status Influences the Outcome of Notch-Induced Malignancy

Caroline Poisson

The Notch signaling cascade is a well conserved pathway that regulates many aspects of embryonic development and plays a crucial role in the differentiation process and tissue homeostasis in multiple organs of adult species. Several human pathological disorders, including cancer, arise as a consequence of the deregulation of the Notch signaling pathway. Notch deregulation, up to date, has been best characterized in acute T-cell lymphoblastic leukemia (T-ALL). Indeed, in T-ALL pediatric patients activating Notch1 mutations have been identified in more than 50% of the cases. Increased knowledge of the mechanisms underlying T-ALL development and maintenance is clearly needed as one out of 5 patients with T-ALL has a very poor prognosis. Moreover, the high toxicity of chemotherapeutic regimens has been associated with elevated risks of developing severe secondary health problems. In the present study, we characterized the role of Notch in T-ALL induction and maintenance. Using transgenic mouse models, we could demonstrate that the oncogenic potential of Notch is dependent on RBP-Jκ transcriptional activity. Indeed, the canonical Notch signaling pathway, mediated by the RBP-Jκ transcription factor, is essential for both Notch-mediated T-ALL induction and maintenance, as well as for the induction of a Notch-mediated lymphoproliferative disorder. Moreover, constitutive overexpression of Notch1 at discrete developmental stages within the hematopoietic system, led us to identify a correlation between the differentiation status of a cell, within the hierarchy of the hematopoietic tree, and its sensitivity to Notch1-induced transformation. We demonstrated that forced Notch1 expression in hematopoietic stem cells was not sufficient to induce T-ALL. Nevertheless, aberrant Notch1 expression in the bone marrow resulted in the development of a lethal lymphoproliferative disorder. Overexpression of Notch1 in thmus at the DN2 to DN3 stage of T-cell delvelopment generated an aggressive transplantable T-ALL with important metastatic potential. This suggested that progenitors already committed to the T-cell lineage are highly susceptible to Notch-mediated transformation, which is relevant to the human disease. Nevertheless, forced Notch1 expression after the β-selection checkpoint in the thymys, was no longer sufficient to induce transformation of late DN3 to DN4 thymocytes. We therefore established a murine genetic system that allowed us to dissect the mechanisms of aberrant Notch1 signaling in a lymphoproliferative disorder and a true T-ALL model. We were able to assess the genetic signature that is involved in the transplantability and metastatic potential of leukemic cells and generated a list of candidate genes implicated in these processes. In addition, we correlated genes identified in our murine models with genes associated as well in human T-ALL profiles to identify genes implicated in T-ALL pathogenesis in both mouse and human.

EPFL2011

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.