PGR and breast cancer: Among breast cancers, TGFβ pathway activation and corresponding elevation of FOXP3 was especially striking in triple-negative breast cancer (TNBC) (Fig. 1c), an aggressive subtype that lacks expression of hormone receptors (estrogen receptor (ER)/progesterone receptor (PR)) and HER2/neu, and has a higher risk of metastases and death within 5 years of diagnosis.