Soluble suppressor factors elaborated in experimental malignant ascites |
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Authors: | Alan G Wile Deborrah Hensen Maurice Nahabedian Kenneth H Ibsen Gale A Granger |
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Institution: | 1. Department of Surgery, California College of Medicine, University of California, Irvine, California 91717 USA;2. Department of Biological Chemistry, California College of Medicine, University of California, Irvine, California 91717 USA;3. Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of California, Irvine, California 91717 USA |
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Abstract: | Soluble suppressor factors in the sera of cancer patients inhibit lectin-stimulated lymphocyte proliferation. These factors, derived from human material, preclude easy corroboration by other investigators. To gain a general understanding of soluble suppressor factors and to avoid the necessary restrictions of human experimentation, an animal model was devised. Sprague-Dawley rats were injected ip with the Walker 256 carcinoma. The resultant ascites proved to be a stable, reproducible source of soluble suppressor factors. Ascites inhibited phytohemagglutinin (PHA)-induced blastogenesis of normal splenocytes by 98%. The possibility of a toxic effect was eliminated by vital staining of splenocytes and by examination in a specific lymphotoxin assay. Suppressor activity persisted after heating at 100 °C for 40 min. Extraction by lipid solvents revealed that the bulk of suppressor activity resides in the lipid phase. The active fraction of heat-treated ascites passed through an Amicon PM-10 filter. Thin-layer chromatography revealed the presence of prostaglandins E2 and F2a. Tissue culture supernatants from short-term cultures derived from tumor-bearing animals revealed suppressor activity from thymus, spleen, and liver cultures (97, 91, and 71%, respectively). No suppressor activity was detected in cultures of cancer cells. This study has demonstrated in this animal model that prostaglandins play a major role in suppression of lectin-induced blastogenesis. All suppressor factors appear to be host derived. An understanding of the mechanism of release of these suppressor substances may open new avenues in the immunotherapy of cancer. |
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Keywords: | Recipient of ACS Junior Faculty Fellowship and to whom requests for reprints should be addressed: Department of Surgery University of California Irvine Medical Center 101 City Drive So Orange Calif 92668 |
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