PGR and breast cancer: Resistance-associated proteins were Caveolin-1, PgR, mTOR, phosphorylated MEK1/2 (pSer217/221) of the Erk/MAPK signaling pathway, phosphorylated IKKα (pThr23) of the NFκB pathway, the microtubule-associated protein Tau and the basal breast cancer markers CK5, CK6 and Vimentin-pSer56 (Table 2).