TRANSFECTED NEU ONCOGENE INDUCES HUMAN PROSTATE-CANCER METASTASIS

c-erb B2/neu has been demonstrated to be a transforming oncogene in bo th rodent and human prostatic epithelial cells. To understand the pote ntial role of neu in human prostatic cancer progression, we used a gen e transfer procedure to determine whether neu amplification/overexpres sion leads to increased tumor growth and metastasis. We chose an andro gen-independent human prostatic epithelial cell line, PC-3, as the tar get for gene transfer. PC-3 cells were cotransfected with pSVneu-T (a point-mutated rat neu oncogene construct) and pSV2neo, and single-cell cloned. Fifty cell clones were isolated and characterized, of which t wo neu-transfected clones (N17 and N35) and a neo control clone (C32) were studied extensively with respect to neu gene integration, levels of neu mRNA and protein expression, anchorage-independent growth, and tumorigenic and metastatic potential. Results showed that: 1) Clone N3 5 contained 70 copies of the neu oncogene and a high level of neu mRNA transcripts. It acquired increased anchorage-independent growth poten tial in vitro and increased tumorigenicity in vivo. 2) Clone N17 conta ined 10 copies of the neu oncogene and a low level of neu mRNA transcr ipts. It did not acquire additional capability for anchorage-independe nt growth and tumorigenic potential as compared to the controls. 3) De spite an increased level of neu mRNA transcripts present in clone N35, there was no corresponding increase of the steady-state levels of neu protein in this particular clone. 4) When administered subcutaneously , none of the cell clones tested, including the control neomycin-resis tant clone, acquired metastatic potential. However, clone N35 exhibite d marked metastatic potential when administered orthotopically; this c ell clone was found to disseminate widely to the lymph nodes, kidney, skeletal muscle, lung, liver, and bone. 5) When neu-transfected cell s ubclones from N35-induced primary and metastatic lymph node, kidney, a nd bone tumors were analyzed for cytoskeletal, extracellular matrix, a nd cell adhesion protein expression, the bone metastatic subclone exhi bited increased levels of vimentin and collagen IV and decreased level s of cytokeratin and ICAM-1. These results, taken together, suggest th at neu transfection induces secondary changes, which, rather than neu protein per se, are responsible for the acquisition of tumorigenic and metastatic potential of prostate cancer cells when an appropriate hos t microenvironment is present. (C) 1996 Wiley-Liss, Inc.