A new secreted prostate protein has the N-terminal sequence KYVQLAENXXTDNG, or a variant, and shows immunoreactivity with serum and/or T-lymphocytes from an individual with prostate cancer. Antibodies against the N-terminal fragment are capable of detecting at least 30% of primary or metastatic human prostate tumors. DNA encoding the protein may be inserted in a vector for recombinant protein expression in Escherichia coli, a yeast or a mammal cell culture. The protein may be used as an antitumor recombinant vaccine. A new monoclonal antibody against the protein may be used as a diagnostic agent to detect prostate cancer. In an example, an LnCapfgc cell culture was grown in RPMI-1640 culture medium with 10% fetal cattle serum, and proteins in the supernatant were purified and sequenced. Six new prostate antigens were isolated, which lacked significant homology to known proteins.