Background: Prostate carcinoma progression from an androgen dependent (AD) state to an androgen independent (AI) state occurs clinically in patients who undergo hormonal therapy. In their laboratory, the authors developed two human prostate carcinoma skeletal metastasis models, the LNCaP progression model and the ARCaP model, to investigate phenotypic and genotypic changes of prostate carcinoma cells during disease progression and to understand molecular pathways for potential therapeutic targeting.
Methods: LNCaP or ARCaP cells were inoculated in athymic mice and were exposed to selective hormonal conditions both in vivo and in vitro. The effects of various hormonal treatment regimens on tumor volumes and distant metastasis and the effects of bone stromal cells on prostate specific antigen (PSA) expression by prostate carcinoma cells were evaluated.
Results: The authors propose that prostate carcinoma progression from the AD state to the AI state assumes three AI phenotypes: AI that remains androgen responsive, AI that is unresponsive to androgen stimulation, and AI that is suppressed by or hypersensitive to androgen. AI prostate carcinoma cells interacted reciprocally with osteoblasts to produce enhanced tumor growth and osteoblastic reaction when they are deposited in bone. Bone stromal cell conditioned media stimulated prostate carcinoma cell growth and suppressed its PSA expression, as also evidenced by androgen receptor-mediated transactivation of PSA promoter reporter activity. Conditioned media obtained from prostate carcinoma cells also stimulated osteoblastic cell growth in vitro. A novel gene therapy strategy is being developed to target prostatic tumor epithelium and its supporting stroma using tissue specific and tumor-restricted, promoter-directed toxic gene expression in both cellular compartments. In addition, new strategies are being designed to target the tumor endothelial system in the stroma and tumor cell-extracellular matrix interaction mediated by isotype specific integrins.
Conclusions: Prostate carcinoma skeletal metastasis models may prove useful in developing a new targeting strategy for the prevention and treatment of patients with prostate carcinoma.