STAT3 and breast cancer: The differential effect of silencing GRN on PY-STAT3 in breast cancer cells with constitutive versus cytokine-inducible STAT3 activation suggests that GRN may have multiple collaborating mechanisms of modulating STAT3 activity including affecting the dynamics of cytokine-stimulated STAT3 phosphorylation and also modifying the DNA binding of STAT3 or other transcriptional cofactors.