Fig. 1. Sources employed for in vitro and in vivo tumor modeling.

This figure outlines the major sources employed in tumor modeling. For in vitro representations of tumor cells, both established cancer cell lines and patient-derived tumor cells were used. Emerging models, such as patient-derived tumor organoids (PDOs), which are developed from patient-derived stem cells, serve to recapitulate the heterogeneity intrinsic to tumor cells more faithfully. In the context of in vitro stroma reconstruction, only stromal cell lines and primary stromal cells derived from tumor tissue can accurately represent the tumor stroma. For in vivo studies, mouse models are the most commonly utilized systems. These include cell line-derived xenograft (CDX) models that are generated by inoculating tumor cell lines into immunocompromised mice; patient-derived xenograft (PDX) models that are established through the implantation of patient tumor cells or tissue into immunocompromised mice; genetically engineered mouse models (GEMMs) that feature genomes altered to mimic in vivo genetic events; and environmentally induced mouse models (EIMMs) that are developed through the administration of carcinogens to immunocompetent mice. Notably, these models have limitations in their ability to incorporate a human stromal cell compartment, often relying on mouse stromal cells or substituting human stromal cells. Strategies focused on the deconstruction and subsequent reconstruction of the tumor microenvironment may offer more accurate representations of the heterogeneous tumor stroma.