GENETICALLY DESIGNING A MORE POTENT ANTI-PANCREATIC CANCER AGENT BY SIMULTANEOUSLY COTARGETING HUMAN IL-13 AND EGF RECEPTORS IN A MOUSE XENOGRAFT MODEL

Abstract

Alternative therapies treatments are urgently needed for drug-resistant pancreatic cancer therapy. IL-13R and EGFR are potential targets and have been targeted by recombinant cytotoxins (CT) made by fusing IL-13 to toxin genes. These drugs are not mainstream, but have shown great promise. To improve activity of a recombinant IL-13 CT comprised of IL-13 spliced to and truncated diphtheria toxin (DT390), Epidermal Growth Factor (EGF) was added to the same single chain protein. This new recombinant bispecific CT, called DTEGF13 was potent and highly effective against MiaPaCa-2 human pancreatic cancer cells in vitro displaying an IC50 of 0.00017 pM, representing a 41-fold increase in activity over DTEGF and a 176,000-fold increase in activity over DTIL-13. Similar results were obtained with the Panc-1 cell line. Studies with mixtures of monomeric CT showed that the enhanced activity of DTEGF13 was dependent on having both ligands on the same single chain molecule. A similar enhancement was observed against the lung adenocarcinoma cell line, H2891-T3. Enhanced activity could not be explained by the increased number of EGF and IL-13 molecules available for binding since a combination of monospecific DTEGF and DTIL13 did not cause the same enhanced activity. Killing was receptor specific as Daudi lymphoma cells were unaffected by the highly selective DTEGF13 and cytotoxicity could be blocked with a specially synthesized EGF13 protein devoid of DT390. In a xenograft flank tumor model, intratumoral injection of DTEGF13, but not monospecific DTEGF or DTIL13, significantly inhibited the growth of established MIA PaCa-2 tumors in nude mice (p < 0.008). In this model, the human EGF and IL-13 components of DTEGF13 are reactive with mouse EGFR and IL-13R respectively. These studies show that a new cotargeting agent simultaneously recognizing EGFR and IL-13R is more effective than its monospecific counterparts and that DTEGF13 has numerous therapeutic advantages for treatment of pancreatic cancer.