PADI4 and breast cancer: Additionally, we inoculated fresh tumor cells isolated from spontaneous mammary tumors of MMTV-PyMT mice to wild-type C57BL/6J (WT) or syngeneic peptidylarginine deiminase 4–knockout (Pad4–/–) mice (the latter showed substantially impaired capacity to generate NETs) (16), then treated them with Dox or vehicle.