Xenograft as In Vivo Experimental Model.

The identification of experimental models that recapitulate human cancers designed to predict patient clinical response to therapies is a major break in oncology. Cancer stem cells (CSCs) represent a small tumor cell population responsible for drug resistance, where their effective killing may lead to identifying better treatment options. While the CSCs hypothesis highlights the need for a specific tumor target, patient-derived xenografts (PDXs) should also be considered for drug development as they better represent tumor heterogeneity and the environment in which a tumor develops.