NPC1L1 and neoplasm: This additional stromal subtyping was also recently applied to PDAC patient-derived xenograft (PDX) tumours, whereby tumours classified as basal or classical were shown to have an ‘echo’ in the mouse stroma.49 They further demonstrated the power of their classifications through inhibition of cholesterol uptake in subtyped PDX models, where basal tumours were highly sensitive to inhibition, but classical tumours were shown to have higher NPC1L1 expression and may require a greater concentration of inhibitor to achieve an equivalent growth inhibition.