Several pieces of evidence support the presence of epithelial PCa cells in the reconstituted HPCa/Hs5 tumors: most tumor cells present an epithelial morphology; CK8+ and CK5+ cells can be observed; RT-PCR and/or Western analyses reveal AR and CK18 expression in most tumors; karyotyping analysis shows cytogenetic abnormalities characteristic of human PCa cells; and presence of EpCAM+ cells that are both clonogenic and tumorigenic. The gene discussed is KRT18; the disease is neoplasm.