Anti-oncofoetal proteins for targeting cytotoxic drugs

Fatty acid conjugates of 2'-deoxy-5-fluorouridine as prodrugs for the selective delivery of 5-fluorouracil to tumor cells

We have prepared a novel class of prodrugs by coupling 2'-deoxy-5-fluorouridine (5dFU) to oleic (18:1) and docosahexaenoic (22:6) acids, respectively. The cytotoxic activity of the drug and its conjugates (5dFU-18:1 and 5dFU-22:6) has been assayed in vitro upon HT-29, a colon carcinoma cell line of human origin. After short term (2-hr) treatments with the drugs, both fatty acid conjugates of 5dFU showed cytotoxic activity in a dose-dependent way, while 5dFU alone was devoid of toxic effects within the whole range of concentrations (10-200 microM) tested. Following long term (24- or 48-hr) incubations only a fraction of the HT-29 cell population was sensitive to 5dFU, the rest of the population being resistant even at the highest concentration tested (200 microM). In contrast, 5dFU-oleic acid and, particularly, 5dFU-docosahexaenoic acids appeared toxic for the whole population of HT-29 cells under the same experimental conditions. The considerable gain in cell toxicity and, to a lesser extent, in selectivity resulted from the conjugation since the toxic effect of the drug alone was not modified when equimolar mixtures of 5dFU and fatty acids were assayed. These results confirm a previous study on the cytotoxicity of fatty acid derivatives of chlorambucil toward malignant lymphoblastoid cells and reinforce the potential use of fatty acid conjugates as efficient anti-tumor prodrugs.

Antibody-mediated targeting in the treatment and diagnosis of cancer: an overview

Enhancing the discrimination between tumour and host has been an underlying goal of efforts to improve the diagnosis and treatment of cancer. Over the past 15 years considerable interest has focussed upon targeting systems designed to permit selective delivery of a variety of agents, including drugs, radioisotopes and toxins, to tumours, for both diagnosis and therapy. A vast body of information has accumulated on this subject, and considerable emphasis has been placed on the use of antibodies as carriers, as at present they offer the greatest clinical potential. Many targeting systems have been evaluated in vitro and in pre-clinical models, but few, with the exception of antibody-radioisotope conjugates, have been evaluated in patients. However, systematic evaluation of the therapeutic potential of immunoconjugates in the clinic is planned or already under way. While reviews of some individual aspects of antibody targeting do exist, there are none that encompass this entire field. Our objective is to fill this gap with a concise overview of antibody-mediated targeting for diagnostic and therapeutic applications.

Methods for production of monoclonal antibodies with specificity for human lung cancer cells

We have developed a screening strategy and technology to produce monoclonal antibodies with specificity for human lung cancer cells. Mice and rats were immunized with well-characterized tissue culture lines of human small cell lung cancer (SCLC), mouse myeloma x spleen hybrids formed by the technique of Kohler and Milstein, and the resulting culture fluids were screened for antibody binding phenotype using a radioimmunoassay. To facilitate testing large numbers of culture fluids, a 96-well, microtiter based, reusable, replicating device was designed. Using this, many hybridoma culture fluids were replica plated for antibody binding tests on a series of human target cell plates. Hybrids producing antibodies that reacted with the immunizing SCLC line and another independent SCLC line, but not with autologous B-lymphoblastoid cells derived from one of the patients, were identified, selected, and then repeatedly recloned using the same screening strategy. With this technology, hybridomas representing less than 0.5% of all hybrids generated could be isolated and stable antibody producing cultures derived. Such antibodies reacted with a panel of well-characterized SCLC lines and SCLC samples taken directly from patients but not with a variety of normal tissues. Using these antibodies we can demonstrate: tumor cell contamination of bone marrow specimens, marked heterogeneity of antigen expression on cells within individual SCLC lines and individual patients, and inhibition of clonal growth of SCLC lines in soft agarose assays. All of these findings have potential clinical and cell biologic application.