A. Trouet

Drug Targeting in Human Cancer Chemotherapy

Drug targeting aims to restrict the access of pharmacological agents to selected cells. Theoretically, such a method should on one hand, decrease unsuitable side effects resulting from an interaction of the drugs with non target cells and, on the other hand, enhance the pharmacological activity by increasing the proportion of the administered drug found within the target cells. Our conceptual approach to this problem consists in linking drugs through a covalent bond to macromolecular carriers which are recognized by receptors or antigens present at the cell surface of the target cells and thereafter endocytosed to allow the release of the drug after hydrolysis of the covalent linkage by lysosomal enzymes.

DNA, Liposomes, and Proteins as Carriers for Antitumoral Drugs

The “drug-carrier” concept in cancer chemotherapy is discussed in view of the experience gained in developing and testing drug-carrier complexes composed of anthracyclines and vincristine associated with DNA, liposomes, or proteins.

Immunohistochemical Reaction of Three Monoclonal Antibodies to Human Milk Fat Globule Membrane with Human Normal and Tumoral Tissues

Abstract The reactivity of three monoclonal antibodies to human milk fat globule membrane with human normal and tumoral tissues has been studied by indirect immunohistochemical methods. Results show that one of them reacts with 19 out of 19 ductal breast carcinoma as well as with lymph node metastasis but also with some normal epithelial cells. The two others react respectively with 12 and 13 out of 19 breast tumors examined. However some weak reaction with normal tissues has been observed as well. These results suggest that such antibodies could be used as diagnostic tool but also to restrict partially the access of attached drug to breast tissue, decreasing therefore toxicity of the drug.

Covalent Linkage of Anthracyclines to Macromolecular Carriers

Abstract Daunorubicin (DNR) and doxorubicin (DOX) have been covalently linked to protein carriers such as human serum albumin (SA), galactosylated serum albumin (gal SA) and antibodies. The drug is transformed into a succinylated tetrapeptide derivative and is linked to the amino group of the protein via an activated ester derivative. Molar drug to protein ratios of 4 to 12 have been reached in the drug albumin conjugates whereas in the drug antibodies conjugates its value never raised above 3. Monomeric conjugates were obtained in good yields with over 99.7% of the drug covalently attached to the carrier.

Binding, Uptake and Subcellular Distribution of Two Monoclonal Antibodies to Human Milk Fat Globule Membrane Studied on Human Mcf 7 Breast Carcinoma Cells

Abstract Binding, uptake and subcellular distribution of two monoclonal antibodies 7F11C7 (IgG 2b) and 9H4 (IgG 3) raised against Human Milk Fat Globule Membrane (HMFGM) have been studied on cultured MCF-7 cells, a human breast carcinoma line. Eventhough the kinetics of interaction is different for the two 3H-labelled antibodies, both are interiorized by endocytosis, gain access to lysosomes and their resulted degradation products are released from the cells. For 9H4, recycling of the antigenic sites after antibody unloading inside lysosomes is assumed. After 24 hours of incubation, cell fractionation experiments localize the 7F11C7 antibody in lysosomes whereas 9H4 is found associated with both plasma membranes and lysosomes.

Drug Targeting with Monoclonal Antibody for Human Hepatomas

Abstract Binding, uptake and subcellular distribution of monoclonal antibody to surface antigen of hepatitis B virus (HbsAg) or to alphafoetoprotein (AFP) have been studied in cultured human hepatoma cells. 3H labelled anti-HbsAg IgG is taken up selectively by PLC/PRF/5 cells. In constrast anti-AFP IgG is not selectively taken up by three cell lines. Cell fractionation studies indicate that these antibodies, as control IgG, gain access to lysosomes wherein they are digested.

Binding, Uptake and Processing of Polymeric IgA by Cultured Rat Hepatocytes

The binding, uptake and processing of polymeric IgA (pIgA) by cultured rat hepatocytes have been studied in conditions where the cells reassociate into hepatic-like trabeculae and reform bile caniculi.

Daunorubicin Conjugated to Galactosylated Neoglycoprotein as Drug Carrier Conjugate for Human Hepatomas

Abstract Human serumalbumin to which galactose residues have been linked is selectively taken up via receptor mediated endocytosis by hepatocytes and hepatoma cells. Daunorubicin has been linked to this neoglycoprotein via a succinylated tetrapeptide arm. This conjugate is selectively taken up by cultured rat hepatocytes and human hepatoma Hep G2 cells in a time and concentration dependent process. Our results strongly suggest that the conjugate is endocytosed and that within the lysosomes, the drug is liberated intact whereas the protein is digested. These results indicate that daunorubicin-galactosylated serumalbumin could be used for the treatment of human hepatoma.

Transferrin Protein and Iron Uptake by Liver Parenchymal Cells

The interaction of 59Fe loaded 3H labelled transferrin with rat hepatocytes has been studied. At 4°, the binding of transferrin to cultured hepatocytes is largely non-specific but the presence of about 30.000 high affinity sites has been detected. After 24 h at 37°, hepatocytes have taken up 16 times more 59Fe than 3H, which implies a mechanism for the reutilization of iron-depleted transferrin. After perfusion of livers and cell fractionation, 3H transferrin is associated with vesicles equilibrating at low densities, whereas 59Fe accumulates in lysosomes before to be incorporated in cytosol ferritin.

Transferrin Protein and Iron Uptake by Cultured Mammalian Cells

Abstract The uptake of transferrin iron by cultured mammalian cells involves receptor-mediated endocytosis and internalization of the transferrin-receptor complex, followed by iron release in an intracellular acidic vesicle (which may be the endocytic vesicle itself or a lysosome). The iron is transferred to cytosol ferritin, while the iron-depleted transferrin is recycled back to plasma membrane and released intact into the extracellular medium. In addition, in some cell types, transferrin is also internalized by fluid phase or adsorptive endocytosis, its iron released and the protein degraded in lysosomes.