The purpose of this study was to determine whether the expression level of several metastasis-regulating genes correlates with the metastatic potential of human prostate cancer cells implanted into the prostate of nude mice. The steady-state mRNA expression levels for epidermal growth factor receptor (EGFR; growth), basic fibroblast growth factor (bFGF) and interleukin (IL)-8 (angiogenesis), 72-kd and 92-kd type IV collagenase (invasion), E-cadherin (adhesion), and multidrug resistance (mdr-1; drug resistance) were measured by Northern blot and colorimetric in situ hybridization techniques in human PC-3M cells and selected cell variants with different metastatic potentials. Highly metastatic cells growing in culture constitutively and uniformly expressed higher levels of bFGF, IL-8, type IV collagenase, and mdr-1 mRNA transcripts than parental PC-3M cells or low metastatic cells, which displayed a heterogeneous pattern of gene expression. Human prostate cancer cells implanted in nude mice at an ectopic site (subcutaneous) expressed lower levels of EGFR, mdr-1, bFGF, IL-8, and collagenase type IV than those implanted in an orthotopic site (prostate), indicating that the expression of these genes was dependent on the organ environment. Highly metastatic cells growing in the prostate expressed higher levels of EGFR, bFGF, type IV collagenase, and mdr-1 mRNA than low metastatic parental cells in the same site. These data demonstrate a direct correlation between the expression of several metastasis-related genes and the metastatic potential of human prostate cancer cells in nude mice and suggest that multiparametric in situ hybridization analyses can be used to identify the metastatic potential of individual patients' prostate cancers.