M.Sc Thesis

M.Sc StudentHaus-Cohen Maya
SubjectTargeting Multidrug Resistance Cancer Cells by Recombinant
Single-Chain Fv Antibody Fragments
DepartmentDepartment of Biology
Supervisor PROF. Yoram Reiter


Inherent and acquired multidrug resistance (MDR) is characterized by a simultaneous resistance to diverse anticancer drugs and continues to be a major impediment towards curative chemotherapy of cancer. The MDR1 gene product, P-glycoprotein (Pgp) is an ATP-driven efflux pump, which extrudes a variety of dissimilar hydrophobic cytotoxic compounds from MDR cells. Pgp overexpression results in MDR of tumor cell lines in vitro as well as of a variety of human malignancies. Thus, one major goal is to develop strategies aimed at specifically disrupting Pgp drug efflux activity. To this end, we have here developed a novel small recombinant antibody capable of potent reversal of MDR, by disrupting Pgp drug efflux activity. Using a phage display approach, we have isolated a small single-chain Fv (scFv) recombinant antibody fragment that specifically reacts with the first extracellular loop of the human Pgp. This scFv fragment binds specifically to various Pgp-overexpressing human MDR carcinoma cells lines, and consequently disrupts Pgp drug efflux function, thereby resulting in potent reversal of the MDR phenotype. The present findings constitute the first successful disruption of an anticancer drug extrusion pump activity in MDR cells using a small recombinant scFv fragment. We propose that these novel small Fv-based recombinant antibody molecules, possessing superior tumor penetration capabilities and favorable pharmacokinetic properties, may prove a potent class of agents which specifically inhibit Pgp drug extrusion function. Hence, these small recombinant antibody fragments may be applied in combination chemotherapy in order to overcome MDR in various human cancers.