Generation of monoclonal antibodies specific for human kallikrein 2 (hK2) using hK2‐expressing tumors

Abstract BACKGROUND Human kallikrein 2 (hK2) and prostate‐specific antigen (PSA) are serine proteases in the human kallikrein gene family that are 80% identical at the protein level. Like PSA, hK2 is expressed primarily in the prostate, making it an attractive bio‐marker for prostate cancer development. In addition, its potent enzymatic activity may functionally affect the biology of prostate cancer. In order to further elucidate the possible roles of hK2 in prostate cancer, we have generated a panel of hK2‐specific, non‐PSA cross‐reactive monoclonal antibodies. METHODS A novel tumor‐immunization strategy was used to produce monoclonal antibodies. Human hK2 cDNA was transfected into a BALB/c tumor cell line and used to immunize both BALB/c and PSA‐expressing BALB/c.PSA transgenic mice. Because the BALB/c.PSA transgenic mouse showed a biased response towards hK2, a B cell fusion was performed using spleen cells from a transgenic mouse immunized in this fashion. RESULTS A panel of monoclonal antibodies was produced and shown to be hK2‐specific using newly developed hK2‐specific sandwich ELISA and ELIspot assays. One of the monoclonal antibodies (6B7) was used to detect hK2 in human prostate by immunohistochemistry. Interestingly, two of the antibodies affected the function of hK2. The 1F8 antibody enhanced the enzymatic activity of hK2 whereas the 3C7 antibody inhibited its function. CONCLUSIONS These hK2‐specific antibodies illustrate a novel approach for constructing B‐cell hybridomas and provide useful reagents to examine the role of hK2 in the biology and detection of prostate cancer. Prostate 51: 153–165, 2002. © 2002 Wiley‐Liss, Inc.