In several cancers such as prostate, non-small cell lung cancers, cervical cancers, renal cell carcinoma (RCC) and glioblastoma, activation of STAT3 or STAT5 is associated with a worse prognosis; conversely, STAT3 is associated with favorable prognosis in breast cancer and in some studies in CRC and head and neck squamous cell carcinoma [108]. Here, STAT3 is linked to breast cancer.