STAT3 and breast cancer: However, other studies have reported contradictory findings; Dolled-Filhart et al. [12] reported that STAT3 played the role of a tumor suppressor protein in breast cancer without lymph node metastasis, and the fact that STAT3 and p-STAT3 expression was associated with a favorable prognosis may simply mean that tumors that activate these pathways are less aggressive than tumors that progress even in the absence of STAT activation.