DERIVATION OF ANDROGEN-INDEPENDENT HUMAN LNCAP PROSTATIC-CANCER CELL SUBLINES - ROLE OF BONE STROMAL CELLS

A model of human prostate cancer was established to study cellular int eraction between prostate cancer and bone stroma in vivo. In this mode l, subcutaneous co-injection of 2 nontumorigenic human cell lines - LN CaP, a prostate cancer cell line, and MS, a bone stromal cell line - i nto intact adult male mice resulted in formation of carcinomas that se creted prostate-specific antigen (PSA), a clinically useful human seru m prostate cancer marker. In castrated hosts, upon cellular interactio n with bone fibroblasts, we observed the progression of these tumors f rom an androgen-dependent (AD) to an androgen-independent state (AI). We derived 4 LNCaP cell sublines from the chimeric LNCap/MS tumors: th e M subline from intact hosts and the C4, C4-2 and C5 sublines from ca strated hosts. The LNCaP sublines had chromosomal markers similar to t hose of the parental LNCaP cells and distinctly different from those f o the MS bone stromal cell line. Although the parental and derived cel l lines expressed similar steady-state levels of ornithine decarboxyla se transcript, the sublines expressed 5- to 10-fold higher basal stead y-state levels of PSA transcript than did the parental LNCaP cell line . The LNCaP sublines formed 13- to 26-fold more soft-agar colonies tha n the parental LNCaP cell line. The sublines became tumorigenic, yield ing an incidence of tumors in intact athymic mice of 7-75%. The LNCaP sublines C4 and C5 (but not the parental and M cell line) formed tumor s in castrated hosts when co-injected with bone fibroblasts. A second- generation LNCaP subline, C4-2, was derived from a chimeric tumor indu ced by co-inoculating castrated mouse with C4 cells and MS cells. We f ound that C4-2 subline was tumorigenic when inoculated into castrated hosts in the absence of inductive fibroblasts. Moreover, C4-2 was the only subline capable of forming soft-agar colonies when cultured in se rum-free medium. In comparison with the parental LNCaP cells, the C4-2 subline expressed lower steady-state levels of androgen receptor (AR) protein and mRNA transcript and lost its androgen responsiveness in v itro. Our results suggest that certain genetic traits of prostate canc er cells may be selected or altered through an ''adaptive'' mechanism that involves cellular interaction with the bone stromal cells. (C) 19 94 Wiley-Liss, Inc.