while constitutive STAT3 activation is associated with various human cancers and commonly suggests poor prognosis. It has anti-apoptotic as well as proliferative effects.

STAT3 can promote oncogenesis by being constitutively active through various pathways as mentioned elsewhere. A tumor suppressor role of STAT3 has also been reported. In the report on human glioblastoma tumor, or brain cancer, STAT3 was shown to have an oncogenic or a tumor suppressor role depending upon the mutational background