Notable differences were also detected after the combination of T and HRG compared to HRG alone regarding the formation of HER-1:HER-1 homodimer (6,62 vs 17,5), suggesting that in HER-2 positive breast cancer cells, at least in vitro, HRG might also act as HER-1 activating ligand (Figure 1B). The gene discussed is ERBB2; the disease is breast cancer.