title: Inhibition of circulating dipeptidyl peptidase 4 activity in patients with metastatic prostate cancer.
abstract: Cancer is responsible for many deaths and is a major source of healthcare expenditures. The identification of new, non-invasive biomarkers might allow improvement of the direct diagnostic or prognostic ability of already available tools. Here, we took the innovative approach of interrogating the activity of exopeptidases in the serum of cancer patients with the aim of establishing a distinction based on enzymatic function, instead of simple protein levels, as a means to biomarker discovery. We first analyzed two well-characterized mouse models of prostate cancer, each with a distinct genetic lesion, and established that broad exopeptidase and targeted aminopeptidase activity tests reveal proteolytic changes associated with tumor development. We also describe new peptide-based freeze-frame reagents uniquely suited to probe the altered balance of selected aminopeptidases, as opposed to the full array of exopeptidases, and/or their modulators in patient serum or plasma. One particular proteolytic activity was impaired in animals with aggressive disease relative to cancer-free littermates. We identified the protease in question as dipeptidyl peptidase 4 (DPP4) by analyzing selected knockout mice and evaluating the effect of specific inhibitors. DPP4 activity was also reduced in the sera of patients with metastatic prostate cancer relative to patients with localized disease or healthy controls. However, no significant differences in DPP4 serum levels were observed, which established the loss of activity as the result of impaired enzymatic function. Biochemical analysis indicated that reduced activity was the result not of post-translational modifications or allosteric changes, but instead of a low-molecular-weight inhibitor. After we adjusted for age and total prostate-specific antigen, reduced DPP4 activity remained a significant predictor of cancer status. The results of this proof-of-principle study suggest that DPP4 activity might be a potential blood-based indicator of the presence of metastatic cancer of prostatic origin, either by itself or, more likely, as a means to improve the sensitivity and specificity of existing markers.
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Arpi
authors: A
authors: Nazarian
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Kevin
authors: K
authors: Lawlor
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: San San
authors: SS
authors: Yi
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: John
authors: J
authors: Philip
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065; §Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Mousumi
authors: M
authors: Ghosh
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065; §Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Mariana
authors: M
authors: Yaneva
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065; §Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Josep
authors: J
authors: Villanueva
authors: **Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138;
authors: Alan
authors: A
authors: Saghatelian
authors: ‡‡Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Melissa
authors: M
authors: Assel
authors: ‡‡Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Andrew J
authors: AJ
authors: Vickers
authors: §§Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: James A
authors: JA
authors: Eastham
authors: ¶¶Genitourinary Oncology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Howard I
authors: HI
authors: Scher
authors: §§Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York 10065; ‖‖Human Oncology and Pathology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065;
authors: Brett S
authors: BS
authors: Carver
authors: §§Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York 10065; ¶¶Genitourinary Oncology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York 10065; Department of Laboratory Medicine, Memorial Sloan Kettering Cancer Center, New York, New York 10065; Nuffield Department of Surgical Sciences, University of Oxford, Oxford, UK; Department of Laboratory Medicine, Lund University, University Hospital UMAS, Malmö, Sweden.
authors: Hans
authors: H
authors: Lilja
authors: From the ‡Protein Center, Memorial Sloan Kettering Cancer Center, New York, New York 10065; §Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065; p-tempst@mskcc.org.
authors: Paul
authors: P
authors: Tempst
mesh_terms: D000626:Aminopeptidases / Q000097:blood / Q000235:genetics / Q000378:metabolism; D000818:Animals; D014408:Biomarkers, Tumor / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000097:blood* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009374:Neoplasms, Experimental / Q000097:blood / Q000175:diagnosis; D051059:PTEN Phosphohydrolase / Q000235:genetics; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; C489428:Myc protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D016159:Tumor Suppressor Protein p53; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse; D000626:Aminopeptidases; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4; C545245:Dpp4 protein, mouse