STAT3 and cancer: This difference in prognosis prediction may be partly due to different tumor biology among cancers, and by the various regulatory mechanisms upstream of p‐STAT3 signaling, for example, endogenous negative regulators such as the suppressor of cytokine signaling family, protein inhibitor of activated STAT (PIAS) proteins and the PTP family, or post‐translational modifications (Chai et al., 2016).