STAT3 and neoplasm: In the mouse model, STAT3 was shown to be essential for DEN-induced carcinogenesis.25 Compelling molecular evidence has demonstrated a role for STAT3 in tumor initiation and progression.19, 26, 27 In line with these previous findings, STAT3 phosphorylation at Tyr705 and Ser727 was evident in gp130f/f livers 40 weeks after DEN injection.