In order to test whether the observed correlation between PADI2 and HER2/ERBB2 would be retained at the protein level, we also tested a small sample of cell lines representing the four common breast cancer subtypes and found that PADI2 expression was only observed in the HER2/ERBB2+ BT-474 and SK-BR-3 lines. The gene discussed is ERBB2; the disease is breast cancer.