DPC Cosponsors 25th Anniversary Meeting of the ISOBM

DPC was delighted to cosponsor the annual meeting of the International Society for Oncodevelopmental Biology and Medicine (ISOBM) held this year in Montreux, Switzerland. The society was founded in 1972 by the late Professor Hidematsu Hirai, Sapporo, Japan, who wanted to facilitate international contact between scientists from Japan, Russia, Europe, Canada and the US in the field of carcinoembryonic antigens. All of the 250 submitted abstracts were published in the society's journal, "Tumor Biologys ", and made available during the ISOBM meeting.

Tumor Markers in Cancer Immunotherapy
The scientific symposia covered aspects of cancer immunotherapy, tumor targeting, gene therapy, apoptosis (programmed cell death), and cytokine therapy. Many studies were reported on the use of tumor markers in a variety of cancers, including prostate, breast, lung, ovarian, melanoma, germ cell, gastrointestinal tract and pancreatic. Often, combinations of markers are of greater value than markers used individually.

Among studies using DPC's tumor marker assays were two by independent research groups on the detection of serum interleukin-2 receptors (IL-2R) in benign and malignant epithelial ovarian tumors, using the IMMULITE® IL-2R* assay. Serum cytokine measurements hold the promise of many applications in oncology.

Tissue Differentiation Workshops
One feature of the ISOBM meeting which has excited academic and industry scientists alike has been the tissue differentiation (TD) workshops. The workshops are intended to be a bridge between research and industry, wherein monoclonal antibodies can be submitted to gain an understanding of some tumor marker characteristics. The areas which have benefited from analyses are prostate specific antigen (PSA), cytokeratins (for example, TPS(TM)*‚an assay which has recently become available on the IMMULITE), sialyl-Lewisa (GI-MA*, CA19-9) for gastrointestinal and pancreatic tumors, alpha-fetoprotein (AFP*) and MUC1 antigen (BR-MA*, CA15-3). This year a new workshop was announced for HCG with the intention of better understanding this molecule and obtaining a consensus among assay manufacturers. DPC has actively participated in, and has submitted a number of monoclonal antibodies to, these workshops.

Prostate specific antigen molecular model. Some key residues in the active site region are in red. The disulfide bridges are in green. Strands and helices appear as yellow arrows and magenta cylinders, respectively. (Used with permission from Dr. Bruno Villoutreix and Dr. Hans Lilja of Lund University, Malm– University Hospital, Sweden.)

PSA Workshop
The workshops categorized the antibodies according to the region of the molecule that they recognize. For example, in the PSA workshop, all of the monoclonal antibodies submitted have been mapped to six distinct binding regions on the molecule by crossinhibition studies. The five PSA monoclonals submitted by DPC were chosen in virtue of their ability to detect different epitopes on the molecule, including the alpha1-antichymotrypsin (ACT) binding site on PSA. The predominant form of PSA in the serum is the complex PSA-ACT; antibodies that detect the ACT-binding site thus recognize free PSA. One of the monoclonal antibodies submitted by DPC detects this site and is an essential part of both the IMMULITE Free PSA assay and the Coat-A-Count® Free PSA IRMA.

PSA belongs to a family of proteins known as the kallikreins. The most recent results show that 29 percent of all of the submitted PSA monoclonal antibodies have human kallikrein 2 (hK2) reactivity; this is not totally surprising since hK2 and PSA (hK3) have very close structural homology. The workshop will focus next on hK2 antibodies and PSA-ACT-specific antibodies. It will be interesting to see whether any clinical advantage can be gained from the measurement of these other molecules. Structural studies of the PSA molecule were presented by Dr. Hans Lilja; an example of this work is provided in the figure. All of the data from these workshops will appear in a future issue of "Tumor Biology ".

*Available outside the US.