Biomarker development, from bench to bedside

Abstract

This review describes studies performed by our group and other laboratories in the field aimed at development of biomarkers not only for cancer but also for other diseases. The markers covered include tumor-associated trypsin inhibitor (TATI), tumor-associated trypsin (TAT), human chorionic gonadotropin (hCG), prostate-specific antigen (PSA) and their various molecular forms, their biology and diagnostic use. The discovery of TATI was the result of a hypothesis-driven project aimed at finding new biomarkers for ovarian cancer among urinary peptides. TATI has since proved to be a useful prognostic marker for several cancers. Recently, it has been named Serine Peptidase Inhibitor Kazal Type 1 (SPINK1) after being rediscovered by several groups as a tumor-associated peptide by gene expression profiling and proteomic techniques and shown to promote tumor development by stimulating the EGF receptor. To explain why a trypsin inhibitor is strongly expressed in some cancers, research focused on the protease that it inhibited led to the finding of tumor-associated trypsin (TAT). Elevated serum concentrations of TAT-2 were found in some cancer types, but fairly high background levels of pancreatic trypsinogen-2 limited the use of TAT-2 for cancer diagnostics. However, trypsinogen-2 and its complex with α1-protease inhibitor proved to be very sensitive and specific markers for pancreatitis. Studies on hCG were initiated by the need to develop more rapid and sensitive pregnancy tests. These studies showed that serum from men and non-pregnant women contains measurable concentrations of hCG derived from the pituitary. Subsequent development of assays for the subunits of hCG showed that the β subunit of hCG (hCGβ) is expressed at low concentrations by most cancers and that it is a strong prognostic marker. These studies led to the formation of a working group for standardization of hCG determinations and the development of new reference reagents for several molecular forms of hCG. The preparation of intact hCG has been adopted as the fifth international standard by WHO. Availability of several well-defined forms of hCG made it possible to characterize the epitopes of nearly 100 monoclonal antibodies. This will facilitate design of immunoassays with pre-defined specificity. Finally, the discovery of different forms of immunoreactive PSA in serum from a prostate cancer patient led to identification of the complex between PSA and α1-antichymotrypsin, and the use of assays for free and total PSA in serum for improved diagnosis of prostate cancer. Epitope mapping of PSA antibodies and establishment of PSA standards has facilitated establishment well-standardized assays for the various forms of PSA.

• Epitope mapping
• hCGβ
• human chorionic gonadotropin
• immunoassay standardization
• prostate-specific antigen
• SPINK1
• tumor markers
• tumor-associated trypsin inhibitor
• tumor-associated trypsin

View correction statement:

Erratum

Acknowledgements

Throughout my career, I have been fortunate to collaborate with enthusiastic and skilled people. I have especially enjoyed tutoring doctoral students by helping them to experience the joy of discovering new phenomena. I have also had the luck to collaborate with many skilled clinicians, Markku Seppälä, Caj Haglund, Pekka Ylöstalo, Olavi Ylikorkala, Bruno Cacciatore, Dan Apter and Leo Dunkel, biochemists and biologists, Ursula Turpeinen, Jim Schröder, Marja-Liisa Huhtala, Hannu Koistinen, Leena Valmu. Thanks to these I have been able to develop clinically relevant methods. I have had the luck of having very skilled technicians working with me for decades, especially Taina Grönholm, Maarit Leinimaa and, Marianne Niemelä. The collaboration with Steven Birken, Peter Berger, Jean-Michel Bidart, Rob Norman, Catharine Sturgeon and Elisabeth Paus has been essential for the success of the hCG standardization and epitope mapping of hCG. Collaboration with other research groups has been essential for many projects and I would like to thank, Timo Lövgren, Kim Pettersson, Hans Lilja, Anders Bjartell, Barry Dowell, Kjell Nustad and Olle Nilsson.

Collaboration with diagnostics companies has been crucial by facilitating the use of cutting edge technology. I am grateful to Erkki Soini, who as the research director of LKB-Wallac gave me access to reagents and equipment for time-resolved fluorometry. Collaboration with PerkinElmer-Wallac, Orion Diagnostica, Medix Biochemica, and Abbott Diagnostics has been essential for the success of many of my projects. It has also been a necessity in order to make new assay commercially available.

Disclosures

The author holds patents for TATI, tumor-associated trypsinogen, free and complexed PSA, PSA complexes with API and A2M and peptides modulating the activity of KLK2 and KLK3. He has served as a consultant for LKB-Wallac, Pharmacia-Wallac, PerkinElmer, Orion Diagnostica and Abbott Diagnostics.

Declaration of interest

The author reports no conflicts of interest. The author alone is responsible for the content and writing of this article.