Immunoregulatory markers in rats carrying Dunning R3327 H, G, or MAT-LyLu prostatic adenocarcinoma variants

The Dunning R3327 tumor represents a system for studying prostate cancer in Copenhagen X Fischer rats. Animals bearing variant sublines (H, G, and MAT-LyLu) differing in growth rate, differentiation, hormone responsiveness, and metastatic ability were assayed for three immunological markers. Spleens were passed through a tissue sieve, and mononuclear cells were obtained by Ficoll-Hypaque centrifugation. These were assayed for leukocytic subsets using monoclonal antibodies. An adherent population was isolated and evaluated using thin-layer chromatography for conversion of radiolabeled arachidonic acid to E series prostaglandins. Finally, sera from these animals were assayed for levels of circulating immune complexes using polyethylene glycol precipitation. Data from 52 rats bearing the various tumors were obtained, correlated with subline aggressiveness, and compared to 15 controls. Each tumor group demonstrated significantly lower helper/suppressor T-cell ratios than controls, probably due to general tumor presence. In addition, the most aggressive R3327 MAT-LyLu variant had significantly increased prostaglandin E synthesis by adherent spleen cells compared to the H or G sublines and significantly increased levels of circulating immune complexes relative to the H subline. G subline values for both prostaglandin E and circulating immune complexes levels were intermediate, suggesting that these markers correlate better with tumor aggressiveness than helper/suppressor T-cell ratios.