The present invention relates to an isolated antibody or antigen-binding fragment thereof that specifically binds with high affinity to at least a portion of a segment of human prostate-derived Ets transcription factor (PDEF). The anti-PDEF antibody of the present invention is effective in prognostic and diagnostic assays for detecting PDEF with immunohistochemistry. The present invention also relates to methods of making the anti-PDEF antibody disclosed herein. The present invention further relates to vaccines against cancers associated with positive expression of PDEF, as well as methods for treating those cancers. Vectors, diagnostic kits, and hybridomas are also disclosed.