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Protein A of Staphylococcus aureus Cowan I is a powerful immunostimulating agent. Female Swiss Portan rats fed 7,12-dimethylbenz(alpha)anthrancene (DMBA) exhibited increased serum alkaline phosphatase activity, which returned to normal levels following eight weeks of treatment with 12 micrograms protein A subcutaneously. Protein A reduced the potential of tumor induction by DMBA as observed by the noninduction of tumors until three months after discontinuation of protein A administration. The total leukocyte count was not affected. Protein A treatment for six weeks of DMBA-induced mammary adenocarcinoma-bearing rats caused the increased serum alkaline phosphatase activity to decrease but not to normal levels, indicating regression but no disappearance of the tumors. The total leukocyte count of the tumor bearers was stimulated by protein A and increased 24 hours after protein A administration; however, in the fourth week of treatment it returned to normal levels. The leukocytosis suggests that protein A could cause tumor necrosis by an inflammatory reaction, edema, and cell destruction and thus tumor regression.

Adsorption of the plasma of Sprague-Dawley rats having 7, 12-dimethylbenzanthracene (DMBA)-induced primary mammary adenocarcinomas with protein A-containing Staphylococcus aureus Cowan I (SAC) and reinfusion of the adsorbed plasma caused significant (p less than 0.05) regression of mammary adenocarcinomas. Adsorption of plasma was done at different intervals--weekly, biweekly, and on alternate days. Of these protocols, alternate-day adsorptions induced very fast (within a week) tumor regression (p less than 0.001). Other protocols also produced tumor regression; however, the effect was delayed. In long-term studies, the responding animals showed fewer tumor nodules than did the untreated controls. The plasma of the treated animals showed (a) a reduction in blocking activity, (b) an increase in antibody- and complement-mediated cytotoxicity, and (c) potentiation of the cytotoxic activity of peripheral blood mononuclear cells (PBMCs). Histopathological analyses of biopsied sections of tumors from treated animals showed (a) disruption of tumor cell architecture, (b) loss of glandular structure, (c) shrinkage of epithelial cells, and (d) moderate mononuclear cell infiltration. Thus, adsorption of the plasma of DMBA tumor-bearing rats with SAC allows an indigenous immune mechanism to function against autochthonous tumors to control their growth and cause regression.

Administration of plasma perfused over Protein A immobilized in collodion-charcoal produced focal acute tumor necrolytic reactions in breast adenocarcinomas. With repeated procedures, objective tumor regressions were observed in four of the first five consecutive patients treated. Within 4 to 48 hr after treatments, tumors became hyperemic and edematous, often with the appearance of focal vesicles. Microscopic and ultrastructural evaluation demonstrated a spectrum of lesions in cytoplasm and nucleus of tumor cells indicative of lethal and sublethal changes. With further treatments, more pronounced degenerative changes in individual tumor cells, tumor nodules, and intervening stroma were apparent. Furthermore, increased luminal and abluminal vesiculation of endothelial cells of postcapillary venules adjacent to tumor nodules was noted. With continued treatments at intervals of 2 to 3 days, some tumor sites showed focal mononuclear cell infiltration, and at the conclusion of plasma perfusion treatments previously ulcerated tumor foci were replaced by granulation tissue. These data suggest that several cytotoxic and inflammatory mechanisms are activated simultaneously or in succession and may account for the tumoricidal effects noted following repeated plasma perfusions.

In dogs with spontaneous mammary adenocarcinomas, a single nontoxic infusion of cytosine arabinoside after extracorporeal perfusion of plasms over immobilized protein A resulted in a necrotizing response rapid in onset and specific for tumorous tissue. Gross tumoricidal reactions 12 hours after this combined treatment exceeded the algebraic sum of responses to cytosine arabinoside and protein A perfusion treatments alone in the same dogs, implying a synergistic effect between the two. The magnitude, rapidity, and specificity of the tumoricidal response after the combined treatment suggests that it may be an effective chemimmunotherapeutic approach to breast adenocarcinoma.

Adsorption of autologous plasma over nonviable Staphylococcus aureus Cowan I (SAC) followed by reinfusion of the plasma causes regression of (a) chemically induced rat mammary adenocarcinomas (MA), and (b) canine transmissible venereal tumors (TVT) and spontaneously occurring dog tumors. Animal data are more impressive than that from trials in humans. Nine of 41 patients receiving perfusions of adsorbed plasma showed some partial objective response. Eight of these nine patients received multiple perfusions over a period of time. Twenty-one of 41 patients showed subjective responses. Adsorption of autologous plasma over non-protein A--containing S. aureus Wood 46 caused regression of MA. Adsorption of normal rat plasma with SAC, and infusion of this adsorbed plasma into mammary tumor--bearing rats, caused regression of MA. Intravenous infusion of purified protein A alone caused regression of both rat MA and canine TVT. Superimposed on this observation is the finding that, during plasma adsorption, bacterial moieties leach from SAC. It is possible that the immunostimulation observed in plasma-perfused hosts is due to the removal of plasma blocking agents on one hand, and introduction of the bacterial agents on the other.

This report confirms our previous observation that IV inoculation of purified protein A causes regression of rat mammary adenocarcinomas. In treated tumors, we have obtained histological evidence of changes indicating tumor cell destruction. Protein A treatment does not cause reduction in the body weight or organ weights of rats; nor does it cause any decrease in activity of the enzymes of the microsomal mixed function oxidase system in the liver. Protein A stimulates peripheral white cell counts in normal rats, but not in tumor-bearing rats. We found that protein A infusion reduced (P less than 0.0005) the level of circulating plasma immune complex concentration. A homing study with 125I-labeled protein A indicated that liver, spleen, and kidney tissues are the major sites of protein A accumulation. Therefore, protein A seemed to exert its antitumor effects without causing any generalized toxicity to the system. It is postulated that the action of protein A may be related to its ability to cause a drastic reduction in circulating plasma immune complex concentration, thus potentiating the immune reactivity of the host observed earlier.

The toxic effects of protein A (Prosorba, IMRE Corporation, Seattle, WA) treatments given as part of an on-line plasmapheresis or off-line procedure were determined in a Phase I Study. Patients were randomized and treated 12 times either once per week or three times per week with a Prosorba column containing 50 or 200 mg protein A. Treated plasma volumes varied from 150 ml off-line to 2000 ml on-line. Seven patients having advanced metastatic breast adenocarcinoma patients were evaluated. All had advanced progressive disease that was resistant to chemotherapy and/or radiation therapy. Greater than 50% regression of measurable tumor volume occurred in four of seven patients; an additional patient responded with 33.5% regression. Two patients with only bony metastases demonstrated stable disease for a 60-day period. Side effects resulting from protein A treatments included transient fever, chills, rigors, and infrequently nausea, vomiting, diarrhea, episodic hyper and/or hypotension, bronchospasm, venospasm, headache, joint and tumor pain. Mild to moderate reactions were seen in all patients regardless of clinical response, but abated spontaneously or were controlled with pretreatment and/or post treatment with antipyretics and/or antihistaminics. The side effects decreased notably during the course of the week with the more intense reaction occurring during the first treatment of the week. Side effects occurred regardless of column size or volume of plasma treated. In the course of 12 treatments, anemia requiring transfusion developed in two of seven patients. Significant tumor regression was obtained in this group of patients with advanced disease. In light of the mild to moderate side effects and tumor regression in five of seven of the patients treated, protein A treatment merits further evaluation to determine the effectiveness of this treatment in breast adenocarcinoma.

Plasma perfusion over filters containing staphylococcal protein A (SPA) was used to treat 11 patients with adenocarcinoma who developed a hemolytic uremic syndrome. Immunoperfusion resulted in complete clearance of pretreatment elevated levels of circulating immune complexes in eight of the 11 patients with normalization of complement values depressed at the start of the therapy in seven. A significant rise in platelets and erythrocyte counts was achieved in nine patients, and stabilization of progressive renal impairment was achieved in six. The response was incomplete and short lived in three patients with clinically evident tumor recurrence, whereas long-term control of the syndrome was demonstrated in seven patients in complete tumor remission (no recurrence with median follow-up of 9 months). SPA immunoperfusion appears to be an effective form of therapy for this otherwise fatal syndrome.

Protein A was purified from Staphylococcus aureus Cowan I and administered subcutaneously for a period of six weeks to a 7,12-dimethylbenz(alpha)anthracene-induced rat mammary adenocarcinoma model, which resulted in a significant reduction in tumor volume. Considerable fibrosis, inflammatory reactions, cellular debris, and edema were the hallmarks of tumor necrosis caused by administration of protein A. Calcification, which may be the replacement of earlier necrosis, also was observed. Thick eosinophilic secretions were observed in the lumina of the breast tubules. The results suggest that inflammatory mechanisms may be activated, accounting for the tumoricidal effects observed following treatment with protein A.