STAT3 and cancer: Constitutive activation of Stat3 plays an important role in the tumorigenesis of various types of human cancer (Catlett-Falcone et al, 1999; Fernandes et al, 1999), and abrogation of Stat3 signalling has been correlated with stimulation of cell proliferation, prevention of apoptosis and tumour formation (Bromberg et al, 1999; Bowman et al, 2000).