STAT3 and cancer: In addition to activation in cancer cells, STAT3 can be activated by viruses such as HTLV1, Hepatitis B, Hepatitis C, varicella zoster virus, SV40, Friend virus and herpesvirus saimiri (Lee and Yun, 1998; Nakamura et al., 1999; Yoshida et al., 2002; Chung et al., 2004; Sarcar et al., 2004; Vultur et al., 2005; Ni et al., 2007; Sen et al., 2012).