STAT3 and cancer: Besides tyrosine and serine phosphorylation, STAT3 functions in cancer cells can also be elicited by the fine tuning of other post-translational modifications (PTMs), such as methylation [18,19], ubiquitination [20], acetylation [21], SUMOylation [22], S-glutathionylation [23], and S-nitrosylation [24], through the modulation of STAT3 activity and/or stabilization/degradation.