The long-term propagation of primary human prostate cancer (PCA) in vivo or in vitro has been rare. Most such PCAs are phenotypically different from most PCAs in humans; i.e., they make little prostate specific antigen and respond little, if at all, to androgen deprivation. A serially transplantable, primary human PCA, designated CWR22, exhibits a clonal cytogenetic aberration, causes high elevations of prostate specific antigen in the peripheral blood of nude mice, and is unusually responsive to androgen deprivation as compared with other xenografts. Studies of mRNA from CWR22 have demonstrated the expression of prostate specific antigen and the epidermal growth factor receptor family including erbB1/epidermal growth factor receptor, erbB2/neu, and erbB3, but not erbB4. A ligand for these receptors, the neu differentiation factor, is also expressed.