PTEN and neoplasm: Salinomycin, a polyether antibiotic, inhibited PTEN-null castration-sensitive and castration-resistant prostate cancer cells for expansion in vitro and in tumor xenografts, and prevented a compensatory negative crosstalk between AR and mTORC1, which otherwise would have led to reciprocal activation of the two oncogenic pathways, causing activation of one when the other is blocked.