Antiproliferative effect of a lectin- and anti-Thy-1.2 antibody-targeted HPMA copolymer-bound doxorubicin on primary and metastatic human colorectal carcinoma and on human colorectal carcinoma transfected with the mouse Thy-1.2 gene

The aim of this study was to compare the potential of two plant lectins [pe anut agglutinin (PNA) and wheat germ agglutinin (WGA)], monoclonal antibody (anti-Thy-1.2), its F(ab')(2) fragments, and galactosamine as targeting mo ieties bound to the polymer drug carrier to deliver a xenobiotic, doxorubic in, to selected cancer cell lines. We have used primary (SW 480, HT 29) and metastatic (SW 620) human colorectal cancer cell lines and a transfectant, genetically engineered SW 620 cell line with mouse gene Thy-1.2 (SW 620/T) to test the possibility of marking human cancer with xenogeneic mouse gene and use it for effective site-specific targeting. The targeting moieties a nd doxorubicin were conjugated to a water-soluble copolymer based on N-(2-h ydroxypropyl)methacrylamide (HPMA) acting as a carrier responsible for cont rolled intracellular release of the targeted drug. FAGS analysis showed a s trong binding of WGA-FITC to all tested cell lines. Binding of PNA-FITC was considerably weaker. The in vitro antiproliferative effect of lectin-targe ted HPMA carrier-bound doxorubicin evaluated as [H-3]TdR incorporation refl ected both the intensity of the binding and the different sensitivity of th e tested cancer cells lines to doxorubicin. The antiproliferative effect of conjugates targeted with WGA was comparable to that with the conjugates ta rgeted with the anti-Thy-1.2 monoclonal antibody or their F(ab')(2) fragmen ts. The magnitude of the cytotoxic effect of HPMA-doxorubicin targeted with PNA was lower in all tested cell lines. While the conjugates with WGA were more cytotoxic, the conjugates with PNA were more specific as their bindin g is limited to cancer cells and to the sites of inflammation. Noncytotoxic conjugates with a very low concentration of doxorubicin and targeted with PNA, anti-Thy-1.2, or their F(ab')(2) fragments exerted in some lines (SW 4 80, SW 620) low mitogenic activity. The Thy-1.2 gene-transfected SW 620 met astatic colorectal cancer cell line was sensitive to the antiproliferative effect of Thy-1.2-targeted doxorubicin as was shown for the Thy-1.2(+) EL4 cell line and for Thy-1.2(+) concanavalin A-stimulated mouse T lymphocytes. These results represent the first indication of the suitability of transfe ction of human cancer cells with selected targeting genes for site-specific therapy of malignancies.