UC San Diego

Although blockade of androgen receptor (AR) signaling represents the main treatment for advanced prostate cancer (PrCa), many patients progress to a lethal phenotype of "Castration-Resistant" prostate cancer (CR-PrCa). With the hypothesis that early PrCa may harbor a population of androgen-unresponsive cancer cells as precursors to CR-recurrent disease, we undertook the propagation of androgen-independent cells from PrCa-prostatectomy samples of early, localized (Stage-I) cases. A collection of 120 surgical specimens from prostatectomy cases was established, among which 54 were adenocarcinomas. Hormone-free cell culture conditions were developed allowing routine propagation of cells expressing prostate basal cell markers and stem/progenitor cell markers, and which proliferated as spheres/spheroids in suspension cultures. Colonies of androgen-independent epithelial cells grew out from 30/43 (70%) of the adenocarcinoma cases studied in detail. Fluorescence microscopy and flow cytometry showed that CR-PrCa cells were positive for CD44, CD133, CK5/14, c-kit, integrin α2β1, SSEA4, E-Cadherin and Aldehyde Dehydrogenase (ALDH). All 30 CR-PrCa cell cultures were also TERT-positive, but negative for TMPRSS2-ERG. Additionally, a subset of 22 of these CR-PrCa cell cultures was examined by orthotopic xenografting in intact and castrated SCID mice, generating histologically typical locally-invasive human PrCa or undifferentiated cancers, respectively, in 6-8 weeks. Cultured PrCa cells and orthotopically-induced in vivo cancers lacked PSA expression. We report here the propagation of Cancer Initiating Cells (CIC) directly from Stage I human PrCa tissue without selection or genetic manipulation. The propagation of stem/progenitor-like CR-PrCa cells derived from early human prostate carcinomas suggests the existence of a subpopulation of cells resistant to androgen-deprivation therapy and which may drive the subsequent emergence of disseminated CR-PrCa.