title: Human kallikrein 2 (hK2), but not prostate-specific antigen (PSA), rapidly complexes with protease inhibitor 6 (PI-6) released from prostate carcinoma cells.
abstract: Human kallikrein 2 (hK2) is a secreted, trypsin-like protease that shares 80% amino acid sequence identity with prostate-specific antigen (PSA). hK2 has been shown to be a serum marker for prostate cancer and may also play a role in cancer progression and metastasis. We have previously identified a novel complex between human kallikrein 2 (hK2) and protease inhibitor 6 (PI-6) in prostate cancer tissue. PI-6 is an intracellular serine protease inhibitor with both antitrypsin and antichymotrypsin activity. In the current study we have shown that PI-6 forms a rapid in vitro complex with hK2 but does not complex with PSA. Recombinant mammalian cells expressing both hK2 and PI-6 showed hK2-PI-6 complex in the spent media only after cell death and lysis. Similarly, LNCaP cells expressing endogenous hK2 and PI-6 showed extracellular hK2-PI-6 complex formation concurrently with cell death. Immunostaining of prostate cancer tissues with PI-6 monoclonal antibodies showed a marked preferential staining pattern in cancerous epithelial cells compared with noncancerous tissue. These results indicate that the hK2-PI-6 complex may be a naturally occurring marker of tissue damage and necrosis associated with neoplasia. Both hK2 and PI-6 were shed into the lumen of prostate cancer glands as granular material that appeared to be cellular necrotic debris. The differential staining pattern of PI6 in tissues suggests a complex regulation of PI-6 expression that may play a role in other aspects of neoplastic progression.
authors.affiliation: Hybritech Inc., San Diego, CA, USA. mssaedi@beckman.com
authors.forename: M S
authors.initials: MS
authors.lastname: Saedi
authors.forename: Z
authors.initials: Z
authors.lastname: Zhu
authors.forename: K
authors.initials: K
authors.lastname: Marker
authors.forename: R S
authors.initials: RS
authors.lastname: Liu
authors.forename: P M
authors.initials: PM
authors.lastname: Carpenter
authors.forename: H
authors.initials: H
authors.lastname: Rittenhouse
authors.forename: S D
authors.initials: SD
authors.lastname: Mikolajczyk
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018450:Disease Progression; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009336:Necrosis; D011467:Prostate / Q000378:metabolism; D017430:Prostate-Specific Antigen / Q000737:chemistry* / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000737:chemistry* / Q000378:metabolism*; D013997:Time Factors; D020840:Tissue Kallikreins / Q000737:chemistry* / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D011994:Recombinant Proteins; D015843:Serpins; C094472:serpin B6; D020840:Tissue Kallikreins; D017430:Prostate-Specific Antigen