UC San Diego

Androgen-dependent ("AD") early prostate cancer often switches to a lethal, castration-resistant (CR) phenotype. We show that early, "AD" prostate cancers contain CR Cancer Initiating Cells (CIC) that drive its growth. We have isolated CR CIC cells from early PrCa, which possess (i) a high degree of self-renewal, (ii) differentiation ability into hormone-responsive prostate cells, (iii) potent tumorgenicity, (iv) the capacity to grow as "sphere" cells and (v) the potential to metastasize. The propagation of CR PrCa cells from localized AD-PrCa facilitates their characterization. Characterization of CIC-spheres and their adherent progenitor Prostate Tumor Cells (PrTuC) utilized RT-PCR, FACS analysis, and immunofluorescent staining. The markers analyzed include AR, ER[alpha], ER[beta], TERT, TMPRSS2-ERG fusion RNA, and ALDH. PrTuCells and their CIC-sphere embodiment are unresponsive to physiological concentrations of steroid hormones. PrTuCells and CIC-spheres express abundant AR mRNA but no AR protein; ER[alpha] is up-regulated and ER[beta] down-regulated compared with normal human prostate epithelial cells. PrTuCells and CIC-sphere cells express the TERT gene; normal prostate epithelial are TERT -negative. The PrCa-associated fusion mRNA TMPRSS2-ERG was undetectable in PrTuCells. The stemness of PrTuCells and CIC-sphere cells was supported by their expression of aldehyde dehydrogenase (ALDH). Propagation of PrCa CIC facilitates complete exome-sequencing, leading to the identification of causative/etiological events in PrCa initiation and potentially permitting the discovery of targetable entities on early human prostate cancer cells. Our work points to the existence of CR ("androgen- independent") CIC in the early stages of human prostate cancer, representing a paradigm change with far-reaching consequences to the field