An avian embryo patient-derived xenograft model for preclinical studies of human breast cancers

Epithelial-to-mesenchymal plasticity from development to disease: An introduction to the special issue

Epithelial-Mesenchymal Transition (EMT) refers to the ability of cells to switch between epithelial and mesenchymal states, playing critical roles in embryonic development, wound healing, fibrosis, and cancer metastasis. Here, we discuss some examples that challenge the use of specific markers to define EMT, noting that their expression may not always correspond to the expected epithelial or mesenchymal identity. In concordance with recent development in the field, we emphasize the importance of generalizing the use of the term Epithelial-Mesenchymal Plasticity (EMP), to better capture the diverse and context-dependent nature of the bidirectional journey that cells can undertake between the E and M phenotypes. We highlight the usefulness of studying a wide range of physiological EMT scenarios, stress the value of the dynamic of expression of EMP regulators and advocate, whenever possible, for more systematic functional assays to assess cellular states.

Functional precision oncology for follicular lymphoma with patient-derived xenograft in avian embryos

Despite achieving high rates of complete remission with RCHOP immuno-chemotherapy, almost all patients with follicular lymphoma (FL) will experience multiple relapses after treatment. The lack of experimental model of FL limits our understanding of heterogeneity in treatment response. Here we characterized a new model of FL patient-derived xenograft (PDX) in avian embryos. Based on 20 biopsies, we observed that tumor volume reduction upon RCHOP treatment in ovo predicted progression free survival in multivariate analysis. To further explore the model, we performed single-cell RNA sequencing and discovered a signature of 21 genes upregulated after RCHOP exposure, with significant intratumoral heterogeneity. Among these genes, we functionally validated BAX as a critical effector of RCHOP which can be targeted with venetoclax in vitro and in ovo . Overall, the FL-AVI-PDX model is a platform for functional precision oncology in FL, which captures both interpatient and intratumoral heterogeneity, and opens an avenue for drug development.

Development of an in vivo system to model breast cancer metastatic organotropism and evaluate treatment response using the chick embryo

Metastatic lesions produced through the process of systemic tumor cell dissemination and growth at distant sites are challenging to treat and the primary cause of patient mortality. Developing in vivo models of metastasis with utility in evaluating molecular targets and therapeutics in a timely manner would expedite the path to therapeutic discovery. Here, we evaluated breast cancer metastasis and metastatic organotropism using the chick embryo. We developed a method to evaluate metastasis using the MDA231 cell line. Then, using cell lines with demonstrated tropism for the bone, brain, and lung, we evaluated organotropism. Rapid and robust organ-specific metastasis was modeled in the chick embryo and, importantly, recapitulated metastatic organotropism congruent to what has been demonstrated in mice. Treatment response in the metastatic setting was also evaluated and quantified. This work establishes the chick embryo as a model for studies aimed at understanding organotropism and therapeutic response in the metastatic setting.

An in vivo avian model of human melanoma to perform rapid and robust preclinical studies

Metastatic melanoma patients carrying a BRAF^V600 mutation can be treated with a combination of BRAF and MEK inhibitors (BRAFi/MEKi), but innate and acquired resistance invariably occurs. Predicting patient response to targeted therapies is crucial to guide clinical decision. We describe here the development of a highly efficient patient-derived xenograft model adapted to patient melanoma biopsies, using the avian embryo as a host (AVI-PDX^TM ). In this in vivo paradigm, we depict a fast and reproducible tumor engraftment of patient samples within the embryonic skin, preserving key molecular and phenotypic features. We show that sensitivity and resistance to BRAFi/MEKi can be reliably modeled in these AVI-PDX^TM , as well as synergies with other drugs. We further provide proof-of-concept that the AVI-PDX^TM models the diversity of responses of melanoma patients to BRAFi/MEKi, within days, hence positioning it as a valuable tool for the design of personalized medicine assays and for the evaluation of novel combination strategies.

In Vivo Modeling of Human Breast Cancer Using Cell Line and Patient-Derived Xenografts

Historically, human breast cancer has been modeled largely in vitro using long-established cell lines primarily in two-dimensional culture, but also in three-dimensional cultures of varying cellular and molecular complexities. A subset of cell line models has also been used in vivo as cell line-derived xenografts (CDX). While outstanding for conducting detailed molecular analysis of regulatory mechanisms that may function in vivo, results of drug response studies using long-established cell lines have largely failed to translate clinically. In an attempt to address this shortcoming, many laboratories have succeeded in developing clinically annotated patient-derived xenograft (PDX) models of human cancers, including breast, in a variety of host systems. While immunocompromised mice are the predominant host, the immunocompromised rat and pig, zebrafish, as well as the chicken egg chorioallantoic membrane (CAM) have also emerged as potential host platforms to help address perceived shortcomings of immunocompromised mice. With any modeling platform, the two main issues to be resolved are criteria for "credentialing" the models as valid models to represent human cancer, and utility with respect to the ability to generate clinically relevant translational research data. Such data are beginning to emerge, particularly with the activities of PDX consortia such as the NCI PDXNet Program, EuroPDX, and the International Breast Cancer Consortium, as well as a host of pharmaceutical companies and contract research organizations (CRO). This review focuses primarily on these important aspects of PDX-related research, with a focus on breast cancer.