Given that PAD2 likely plays an importantrole in the biology of both ER and HER2+ lesions, these observationssuggest that PAD2 could represent a therapeutic target for 85–90%of all breast cancers in humans.30 Thehigh-resolution structures of PAD1–4 have been reported.9,33−35 The catalytic activity for PADs is known to be regulatedby calcium ions through conformational changes, including the appropriatepositioning of the catalytic cysteine in the active site cleft. Here, ERBB2 is linked to breast carcinoma.