Monoclonal Antibody to SAAL _1–3 Isomer Better Discriminant of the Acute Phase Reaction to Cancer and Monitor of Disease Progression than the Polyclonal Antibody to Human AA

Abstract

During the last three decades it was found that many of the serum proteins that behave as acute phase reactants present specific patterns of change in relation to the dissemination of most malignant tumors; serum haptoglobin, various glycoproteins (1) and serum mucoid (2) were found to be positive discriminants for metastatic spread while serum transferrin and albumin (1) appeared to be negative discriminants. Serum Amyloid A (SAA) a precursor of amyloid A (AA) protein found in amyloid deposits in patients with secondary amyloidosis and with Familial Mediteranean Fever was also found by us (3) and others (4,5) to behave biologically as an acute phase reactive protein, and to be a positive discriminant for metastatic dissemination of malignant tumors (6–9). However, in other studies (10,11,12) the correlation of SAA level with disease activity in patients with cancer was found more difficult to define-The recent identification in our laboratory of four isomers of the low molecular SAA (SAAL) by isoelectric focusing (13) has permitted to look at SAA level variations in different diseases with monoclonal antibodies against these isomers. In the present study, using these antibodies we attempted to better define the correlation between SAA levels and cancer dissemination by looking at the correlation of SAA level with tumor size and by comparing this correlation to that between tumor size and other acute phase reactive proteins. We found that SAAL level correlates well with tumor size, that this correlation is superior to that of four other acute phase reactive proteins we tested and is improved when a monoclonal antibody to one of the SAAL isomers (SAAL 1–3) was used.