Trial of anticancer immunotherapy with immobilized pokeweed mitogen: Immunotherapy by extracorporeal circulation

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Abstract
For the purpose of activating the immune system in the living body, we made use of pokeweed mitogen (PWM). PWM, a type of lectin, has the potential to induce anticancer cells. In order to utilize this potential and apply it to cancer therapy by hemoperfusion with PWM, the lectin is immobilized on the surface of synthetic polymer beads and these beads are packed into a minicolumn. Human peripheral lymphocytes were activated by circulatory contact stimulation through the PWM column for 1 h. After circulatory contact stimulation through the colum, lymphocytes were collected and used as effector cells. Cytotoxicity tests were measured by51Cr-release assay using K-562 cells and Daudi cells for targets. This material could enhance natural killer activity and induce cytotoxicity against natural-killer-resistant Daudi cells. Lymphocytes activated by the PWM column were injected intraregionally into nude mice bearing MKN-1 tumor, and suppression of tumor growth was recognized. Anticancer activities by direct hemoperfusion treatment with a PWM minicolumn were examined in Vx2-tumor-bearing rabbits. A single treatment using the PWM column was performed 6 days after tumor inoculation. Suppression of the tumor growth was observable for 25 days. PWM minicolumns are a likely anticancer material, acting as immunomodulators.