Runx1 acts as a tumor promoter in the formation and maintenance of mouse skin cancer through its promotion of Stat3 activation15,29 and Runx1 stimulates the Stat pathway through the repression of suppressor of cytokine signaling 3 (Socs3), a major negative feedback regulator of Stat3-activating cytokines13. The gene discussed is SOCS3; the disease is skin cancer.