This study was aimed at defining molecular species of prostate-specific antigen (PSA) in immune complexes with immunoglobulin M (IgM). Having in mind the oligoreactivity of IgM and its preference for carbohydrate antigens, there is the possibility that it can selectively recognize known PSA glycoisoforms. PSA-IgM complexes and free PSA fractions were separated from the sera of subjects with prostate cancer (PCa) and benign prostatic hyperplasia (BPH) by gel filtration and subjected to on-chip immunoaffinity and ion-exchange chromatography. PSA-immunoreactive species were detected using surface-enhanced laser desorption/ionization time of flight mass spectrometry. The obtained spectra were analyzed for protein and glycan composition. The general pattern of the molecular species of PCa PSA and BPH PSA found in complexes with IgM was similar. It comprised major peaks at 17？kDa and minor peaks at 28？kDa, corresponding to the entire mature glycosylated PSA. The main difference was the presence of incompletely glycosylated 26.8？kDa species, having putative paucimannosidic structures, observed in PCa PSA-IgM, but not in BPH PSA-IgM. Characteristic PCa PSA-IgM glycoforms pose the question of the possible role of glycosylation as a framework for immune surveillance and may be of interest in light of recent data indicating mannose-containing glycans as cancer biomarker. 1. Introduction Efforts in the field of biomarker research have pointed to the existence of circulating immune complexes as a novel class of tumor markers with diagnostic potential comparable with or greater than that of the corresponding free biomarker. They include biomarker-immunoglobulin M (IgM) complexes, which have been found in several neoplastic diseases, such as colorectal, liver, and prostate cancer [1–3]. Although they are supposed to be a valuable adjunct in differential diagnostics, the biological meaning of this kind of complexes has not been elucidated; that is, it is not known whether they have any physiological role. In addition, from the biochemical point of view, there is no insight into their composition in terms of the structural properties of the molecules recognized by IgM. Prostate-specific antigen (PSA), a well-known tumor marker for prostate cancer (PCa), has been found complexed with IgM in both benign prostatic hyperplasia (BPH) and cancer [3]. In general, PSA comprises heterogeneous molecules differing in primary structure and in glycan composition. Structural variability exists among PSA forms in serum, seminal plasma, and hyperplastic or cancerous tissues [4–6].
References
[1]
L. Beneduce, F. Castaldi, M. Marino et al., “Improvement of liver cancer detection with simultaneous assessment of circulating levels of free alpha-fetoprotein (AFP) and AFP-IgM complexes,” International Journal of Biological Markers, vol. 19, no. 2, pp. 155–159, 2004.
[2]
L. Beneduce, F. Castaldi, M. Marino et al., “Squamous cell carcinoma antigen-immunoglobulin M complexes as novel biomarkers for hepatocellular carcinoma,” Cancer, vol. 103, no. 12, pp. 2558–2565, 2005.
[3]
L. Beneduce, T. Prayer-Galetti, A. M. G. Giustinian et al., “Detection of prostate-specific antigen coupled to immunoglobulin M in prostate cancer patients,” Cancer Detection and Prevention, vol. 31, no. 5, pp. 402–407, 2007.
[4]
W.-M. Zhang, J. Leinonen, N. Kalkkinen, B. Dowell, and U.-H. Stenman, “Purification and characterization of different molecular forms of prostate-specific antigen in human seminal fluid,” Clinical Chemistry, vol. 41, no. 11, pp. 1567–1573, 1995.
[5]
A. M. Ward, J. W. F. Catto, and F. C. Hamdy, “Prostate specific antigen: biology, biochemistry and available commercial assays,” Annals of Clinical Biochemistry, vol. 38, no. 6, pp. 633–651, 2001.
[6]
á. Végvári, M. Rezeli, C. Sihlbom et al., “Molecular microheterogeneity of prostate specific antigen in seminal fluid by mass spectrometry,” Clinical Biochemistry, vol. 45, no. 4-5, pp. 331–338, 2012.
[7]
K. Jung, B. Brux, M. Lein et al., “Molecular forms of prostate-specific antigen in malignant and benign prostatic tissue: biochemical and diagnostic implications,” Clinical Chemistry, vol. 46, no. 1, pp. 47–54, 2000.
[8]
T. Isono, T. Tanaka, S. Kageyama, and T. Yoshiki, “Structural diversity of cancer-related and non-cancer-related prostate-specific antigen,” Clinical Chemistry, vol. 48, no. 12, pp. 2187–2194, 2002.
[9]
K. Jung, J. Reiche, A. Boehme et al., “Analysis of subforms of free prostate-specific antigen in serum by two-dimensional gel electrophoresis: potential to improve diagnosis of prostate cancer,” Clinical Chemistry, vol. 50, no. 12, pp. 2292–2301, 2004.
[10]
A. Sarrats, R. Saldova, J. Comet et al., “Glycan characterization of PSA 2-DE subforms from serum and seminal plasma,” OMICS, vol. 14, no. 4, pp. 465–474, 2010.
[11]
á. Végvári, M. Rezeli, C. Welinder et al., “Identification of prostate-specific antigen (PSA) isoforms in complex biological samples utilizing complementary platforms,” Journal of Proteomics, vol. 73, no. 6, pp. 1137–1147, 2010.
[12]
M. M. Kosanovic, S. R. Goc, G. S. Potpara, and M. M. Jankovic, “On chip immuno-affinity profiling of cancer- and benign hyperplasia-associated free prostate specific antigen,” Disease Markers, vol. 31, no. 2, pp. 111–118, 2011.
[13]
P. R. Huber, H.-P. Schmid, G. Mattarelli, B. Strittmatter, G. J. Van Steenbrugge, and A. Maurer, “Serum free prostate specific antigen: isoenzymes in benign hyperplasia and cancer of the prostate,” Prostate, vol. 27, no. 4, pp. 212–219, 1995.
[14]
H. Hilz, J. Noldus, P. Hammerer, F. Buck, M. Luck, and H. Huland, “Molecular heterogeneity of free PSA in sera of patients with benign and malignant prostate tumors,” European Urology, vol. 36, no. 4, pp. 286–292, 1999.
[15]
J. P. Charrier, C. Tournel, S. Michel, S. Comby, C. Jolivet-Reynaud, J. Passagot, et al., “Differential diagnosis of prostate cancer and benign prostate hyperplasia using two-dimensional electrophoresis,” Electrophoresis, vol. 22, no. 9, pp. 1861–1866, 2001.
[16]
S. D. Mikolajczyk, K. M. Marker, L. S. Millar et al., “A truncated precursor form of prostate-specific antigen is a more specific serum marker of prostate cancer,” Cancer Research, vol. 61, no. 18, pp. 6958–6963, 2001.
[17]
S. D. Mikolajczyk, L. S. Millar, T. J. Wang et al., “‘BPSA,’ a specific molecular form of free prostate-specific antigen, is found predominantly in the transition zone of patients with nodular benign prostatic hyperplasia,” Urology, vol. 55, no. 1, pp. 41–45, 2000.
[18]
H. P. Vollmers and S. Br？ndlein, “The “early birds”: natural IgM antibodies and immune surveillance,” Histology and Histopathology, vol. 20, no. 3, pp. 927–937, 2005.
[19]
H. P. Vollmers and S. Br？ndlein, “Natural IgM antibodies: from parias to parvenus,” Histology and Histopathology, vol. 21, no. 12, pp. 1355–1366, 2006.
[20]
G. P. Dunn, A. T. Bruce, H. Ikeda, L. J. Old, and R. D. Schreiber, “Cancer immunoediting: from immunosurveillance to tumor escape,” Nature Immunology, vol. 3, no. 11, pp. 991–998, 2002.
[21]
G. P. Dunn, L. J. Old, and R. D. Schreiber, “The three Es of cancer immunoediting,” Annual Review of Immunology, vol. 22, pp. 329–360, 2004.
[22]
A. Bélanger, H. Van Halbeek, H. C. B. Graves et al., “Molecular mass and carbohydrate structure of prostate specific antigen: studies for establishment of an international PSA standard,” Prostate, vol. 27, no. 4, pp. 187–197, 1995.
[23]
T. Okada, Y. Sato, N. Kobayashi et al., “Structural characteristics of the N-glycans of two isoforms of prostate-specific antigens purified from human seminal fluid,” Biochimica et Biophysica Acta, vol. 1525, no. 1-2, pp. 149–160, 2001.
[24]
J. M. Mattsson, L. Valmu, P. Laakkonen, U.-H. Stenman, and H. Koistinen, “Structural characterization and anti-angiogenic properties of prostate-specific antigen isoforms in seminal fluid,” Prostate, vol. 68, no. 9, pp. 945–954, 2008.
[25]
K. Y. White, L. Rodemich, J. O. Nyalwidhe et al., “Glycomic characterization of prostate-specific antigen and prostatic acid phosphatase in prostate cancer and benign disease seminal plasma fluids,” Journal of Proteome Research, vol. 8, no. 2, pp. 620–630, 2009.
[26]
T. Vermassen, M. M. Speeckaert, N. Lumen, S. Rottey, and J. R. Delanghe, “Glycosylation of prostate specific antigen ant its potential diagnostic applications,” Clin Chim Acta, vol. 413, no. 19-20, pp. 1500–1505, 2012.
[27]
S. Prakash and P. W. Robbins, “Glycotyping of prostate specific antigen,” Glycobiology, vol. 10, no. 2, pp. 173–176, 2000.
[28]
R. Peracaula, G. Tabarés, L. Royle et al., “Altered glycosylation pattern allows the distinction between prostate-specific antigen (PSA) from normal and tumor origins,” Glycobiology, vol. 13, no. 6, pp. 457–470, 2003.
[29]
M. M. Jankovi？ and M. M. Kosanovi？, “Glycosylation of urinary prostate-specific antigen in benign hyperplasia and cancer: assessment by lectin-binding patterns,” Clinical Biochemistry, vol. 38, no. 1, pp. 58–65, 2005.
[30]
M. M. Kosanovi？ and M. M. Jankovi？, “Sialylation and fucosylation of cancer-associated prostate specific antigen,” Journal of Balkan Union of Oncology, vol. 10, no. 2, pp. 247–250, 2005.
[31]
C. I. Balog, K. Stavenhagen, W. L. Fung, C. A. Koeleman, L. A. McDonnell, A. Verhoeven, et al., “N-glycosylation of colorectal cancer tissues: a liquid chromatography and mass spectrometry-based investigation,” Molecular & Cellular Proteomics, vol. 11, pp. 571–585, 2012.
[32]
B. Zipser, D. Bello-DeOcampo, S. Diestel, M. H. Tai, and B. Schmitz, “Mannitou monoclonal antibody uniquely recognizes paucimannose, a marker for human cancer, stemness and inflammation,” Journal of Carbohydrate Chemistry, vol. 31, no. 4-6, pp. 504–518, 2012.
[33]
H. H. Wandall and M. A. Tarp, “Therapeutic cancer vaccines: Clinical trials and applications,” in Carbohydrate-Based Vaccines and Immunotherapies, Z. Guo and G. J. Boons, Eds., pp. 333–366, John Wiley & Sons, Hoboken, NJ, USA, 2009.
