Fig. 2.

Simplified representation of breast cancer (BC) models generation. (a) Transgenic mice: one common approach for BC genetically engineered mice model generation is to overexpress an oncogene driven by a specific promoter targeting the mammary gland, such as MMTV. (b) 3D culture: the combination of a supporting scaffold (scaffold-dependent model), such as hydrogels and inert matrices, and different cell types allow cell growth and cell-extracellular matrix and cell-cell interactions. (c) Mammospheres (MM): these spheroids can be originated either from breast cancer cell lines (BCCL) or from BC biopsy. A single-cell suspension is obtained from the material, cell phenotypes are sorted for stem and progenitor cells, followed by culture in an ultra-low adherent surface for MM formation. (d) Patient-derived xenograft (PDX): tissue fragments from patient’s tumor are directly transplanted onto the immunodeficient mice heterotopically or orthotopically, with no need of an in vitro preparation step (F0). Once tumor reaches appropriate size, it can be dissected and expanded by reimplanting it onto another mice recipient (F1). The tumor expansion can go on for multiple generations (Fn). Patient-derived organoid (PDO): tissue fragments from patient’s tumor are digested and cultured in a 3D extracellular matrix hydrogel, giving rise to organoids