Cytotoxic and cytostatic effects of anti-Thy 1.2 targeted doxorubicin and cyclosporin A

Abstract

Recently we have developed a new generation of antibody-targeted immunosuppressive (cyclosporin A, CyA) and cytostatic (doxorubicin, Dox) drugs effective in vitro and in vivo. The drugs and the targeting antibody (polyclonal and monoclonal anti-Thy 1.2) are conjugated to the oligopeptidic side chains of a water-soluble synthetic carrier, copolymer of N-(2-hydroxypropyl)methacrylamide (HPMA). In this study we investigated the effects of such drugs on cell proliferation and cytokine release by EL-4 mouse thymoma and X63Ag8-653 (IL-2) and X63Ag8-653 (IL-3) mouse myeloma transfected with IL-2 and IL-3 gene, respectively. The Thy 1.2 + EL-4 mouse thymoma cell line strongly reacted with the anti-Thy 1.2-targeted polymer bound CyA and Dox as assayed by cell fluorometry, whereas Thy 1.2 − X63Ag8-653 (IL-2) and X63Ag8-653 (IL-3) mouse myelomas bound anti-Thy 1.2 targeted drugs to a considerably lower extent. Anti-Thy 1.2 targeted doxorubicin and cyclosporin A effectively inhibit proliferation and IL-2 release by EL-4 mouse thymoma. More importantly, low sensitivity of EL-4 mouse thymoma to the anti-proliferative effect of free doxorubicin is partly overcome when anti-Thy 1.2 targeted form of the drug is used. Proliferation of both X63Ag8-653 mouse myelomas and their lymphokine (IL-2 or IL-3) release is inhibited only in the presence of a very high concentration of antibody-targeted conjugates with no difference between the efficacy of non-targeted and anti-Thy 1.2 targeted form. Preincubation of mouse T-cell lymphoma EL-4 with free anti-Thy 1.2 antibody considerably decreases the cytotoxic effects of anti-Thy 1.2 targeted doxorubicin.