Ferritin nanoparticles, including HFn-Dox,have been shown not only to enter tumor cells via TfR1-mediated uptakebut also to interact with stromal components, such as cancer-associatedfibroblasts (CAFs), which can influence drug delivery and therapeuticoutcome. The composition and densityof the stromal compartment differ substantially between 4T1 tumorsand human-derived xenografts, possibly modulating drug efficacy indistinct ways. Here, TFRC is linked to cancer.