Abstract 4637: Cell penetrating antibodies for intracellular targets: Expanding the antibody-based treatments for cancer

Abstract

Abstract Antibody based therapeutics have gained significant interest in recent years. Herceptin, which targets cell surface protein, have been successful for the treatment of cancer. While antibodies are promising platforms for therapy, antibodies have been limited to targeting cell surface proteins because they cannot penetrate cells. Recently, we have developed cell penetrating antibodies engineered from the conjugation of a cell penetrating peptide (CPP) and an antibody. The CPP-mIgG and CPP-anti-RPA1 IgGs were internalized in cells as observed by fluorescence microscopy. Biological activities of these conjugates were determined and the expected anti-proliferative effects of the CPP-anti-RPA1 were subtly distinguishable from the control CPP-mIgG. While RPA1 is a valid anti-cancer target, its function depends on complicated pathways and cell cycle where dosing may have to be optimized. This demonstrates the difficulties in establishing CPP-IgG as an efficient therapeutic. To demonstrate that CPP-IgG bioconjugates are capable of inducing biological effects, we sought a different intracellular target. Antimitotic drugs are standard cancer chemotherapeutic agents. Recently, other proteins involved in the mitotic machinery have gained much attention. For example, kinesin motor protein Eg5 plays an important role in mitosis and inhibiting Eg5 prevents the formation of bipolar spindles resulting to an unmistakable change of morphology during mitosis_a star-like structure called “monoastral”. Small molecules, such as monastrol and (S)-trityl cysteine (STLC), lead to monastral formation. Thus, we chose Eg5 protein as an intracellular target to demonstrate that CPP-IgG bioconjugates are able to penetrate cells and have neutralizing activity. We expect that CPP-anti-Eg5 conjugates will penetrate cells and produce the canonical inhibition of Eg5 protein by observing for the monoastral morphology during mitosis. We tested whether CPP-anti-Eg5 IgG will present the same biological activity as STLC. We bioconjugated the anti-Eg5 with a CPP. Cell cycle synchronized cells were treated with the positive control STLC and CPP-anti-Eg5 showed an atypical star-like structure similar to monoastral. In whole, these studies show that CPP-IgG against intracellular targets are able to enter the cells and show inhibitory activities. We will describe our progress and discuss approaches to expanding the utility of antibodies as therapeutics for intracellular cancer targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4637. doi:1538-7445.AM2012-4637