PADI4 and neoplasm: Subsequently, in 4T1 orthotopic tumor-bearing mice, Zhu and colleagues found that tumors treated with PAD4 inhibitor 5i (37) had a significant increase in normal neutrophils but a decrease in aging neutrophils (Naged CD194hi | CD62Llo) [75], which can promote breast cancer metastasis by mediating NETs [91].