Protocol for establishing a chemoresistant orthotopic triple-negative breast cancer patient-derived xenograft model for preclinical drug testing.

Here, we present a protocol for establishing patient-derived xenograft (PDX) mouse models of chemoresistant triple-negative breast cancer (TNBC). We describe steps for tumor collection, surgical implantation, and serial expansion. We then detail procedures for histopathological validation and in vivo therapeutic assessment to confirm the maintenance of chemoresistance across passages. These models provide a clinically relevant platform to investigate mechanisms of treatment resistance, evaluate novel therapeutic strategies in preclinical settings, and predict therapeutic responses in refractory TNBC.