To evaluate whether IL-6 trans-signaling is important for activation of 4T1 breast cancer cells, we cultivated 4T1 cells in the presence of IL-6 and/or soluble IL-6Rα and evaluated the individual and combined effects of a blocking anti-IL-6R antibody (which blocks both conventional IL-6 signaling and IL-6 trans-signaling) and a gp130-Fc fusion protein (which only blocks IL-6 trans-signaling). The gene discussed is IL6; the disease is breast carcinoma.