Intracellular antibodies and cancer: New technologies offer therapeutic opportunities

Abstract

Since the realisation that the antigen-binding regions of antibodies, the variable (V) regions, can be uncoupled from the rest of the molecule to create fragments that recognise and abrogate particular protein functions in cells, the use of antibody fragments inside cells has become an important tool in bioscience. Diverse libraries of antibody fragments plus in vivo screening can be used to isolate single chain variable fragments comprising VH and VL segments or single V-region domains. Some of these are interfering antibody fragments that compete with protein-protein interactions, providing lead molecules for drug interactions that until now have been considered difficult or undruggable. It may be possible to deliver or express antibody fragments in target cells as macrodrugs per se. In future incarnations of intracellular antibodies, however, the structural information of the interaction interface of target and antibody fragment should facilitate development of binding site mimics as small drug-like molecules. This is a new dawn for intracellular antibody fragments both as macrodrugs and as precursors of drugs to treat human diseases and should finally lead to the removal of the epithet of the 'undruggable' protein-protein interactions.

Anti-CHMP5 single chain variable fragment antibody retrovirus infection induces programmed cell death of AML leukemic cells in vitro

“…These findings indicate that highly expressed CHMP5 protein in the cytosol may participate in leukemogenesis, and it may be a target for gene therapy. The scFv to target molecules within cells provide a useful tool for research as well as for the control of diseases [13,15,16,21] . To produce a scFv-CHMP5, the hybridoma cells should be created, and subsequently the VL and VH variable region from the RNA of hybridoma cells must be obtained [29] .…”

“…The scFv is one of the smallest fragments to be produced that shows equivalent binding affinity to the parent Fab (fragment antigen-binding) fragment [11,12] . ScFv can be conjugated to different types of molecules, such as radioisotopes and toxins, or expressed as an intracellular antibody (intrabody) in a specific intracellular compartment, where it can interfere with the function of the targeted antigen at the level of a specific domain [13] . Human single chain antibody fragments offer the advantage of being expressed as a single polypeptide, and their small size means that they can serve as a highly safe, selective and effective diagnostic and therapeutical tool [10,[14][15][16][17][18][19][20] .…”

“…Human single chain antibody fragments offer the advantage of being expressed as a single polypeptide, and their small size means that they can serve as a highly safe, selective and effective diagnostic and therapeutical tool [10,[14][15][16][17][18][19][20] . The scFv on target molecules within cells or intrabodies provides a useful tool for research as well as for control of diseases such as human immunodeficiency virus type 1 infection and other diseases [13,15,16,21] .…”

Single Domain Intracellular Antibodies from Diverse Libraries

“…The utilities of intracellular application of antibody fragments is that, unlike gene knock-out and interfering RNAs or antisense, these molecules interfere with cellular functions directly by binding to target proteins and can therefore target specific properties of proteins such as particular signal transduction via blockading protein-protein interaction (2,3). This not only provides valuable and robust tools in biological analysis such as functional genomics and proteomics but also serve as drug surrogates to establish the target validity for drug development by ascertaining the biological effects from targeting the protein.…”

“…Here, we describe use of IAC 3 to isolate VH or VL iDAbs binding to LMO2, TP53, CRAF1, and Hoxa9. We have characterized one VH binding to LMO2 in cells that can inhibit the Lmo2 protein-protein interactions in cells and interfere with Lmo2 function in an erythroid differentiation * This work was supported by grants from the Medical Research Council, from Leukemia and Lymphoma Research, and from the Leeds Institute of Molecular Medicine (University of Leeds).…”