Abstract 5922: "Gammora": Selective killing of cancer cells bearing CD24 by viral integrase

Abstract

Abstract The HIV integrase is important in the integration of viral DNA to the host genome resulting in double-stranded breaks (DSB). Only 1-2 copies are integrated, due to inhibition of HIV-1 Rev protein, making the cells invisible to the immune system. CD24 is mostly expressed on cancer and not normal cells. We hypothesize that specific targeting of the viral particles using mAb to CD24 together with stimulating the enzyme activity and increasing the frequency of integration events, would increase the occurrence of DSB, that will lead to genomic instability, and ultimately to apoptosis of the target cells. Aim To develop a therapeutic platform, for selective eradication of cancer cells, which consists of targeted lentivirus particles and IN-derived peptides. Methods Integrase derived peptides (designated as INR2 and INS) were synthesized. Humanized anti-CD24 antibody (scFv) was engineered and fused to the lentivirus envelope. Stability, solubility and toxicity of the peptides were analyzed by HPLC-MS and MTD, respectively, as well as their activity and permeability into cells. Cell death was measured qualitatively by fluorescent microscopy and quantified by the enzymatic MTT assay. Colorectal, pancreatic and lung cancer cells were used for testing the potency of the lentiviral-based system. The efficacy of the suggested system was assessed in vivo, in nude mice bearing xenografts of lung cancer. The mice were treated systemically twice weekly. Results INS and INR2 stimulate viral integrase in vitro. A single IV administration of INR2 and INS was well tolerated without adverse effects. These lentivirus particles contain nonfunctional DNA with flanked LTRs allowing their integration into the target cells DNA and formation of DSB due to the action of the integrase whose activity was stimulated by the IN-derived peptides. Massive cell death (40-70%) in a dose- dependent manner was achieved. Raltegravir, an antiretroviral FDA-approved drug, was able to inhibit cell death (2-3 times). In vivo, the INR2 and INS combination led to a significant reduction (50%) in tumor volume. Live imaging (IVIS device) of the tumors and selected organs confirmed that the viruses indeed reach the tumor after systemic injection and that the anti-CD24 enhanced the selectivity of infection. Conclusions The use of IN-derived peptides together with the CD24-targeted lenti-therapy approach suggests a novel strategy that specifically promotes killing and removal of a wide range of cancer cells. Citation Format: Shiran Shapira, Eynat Finkelshtein, Abraham Loyter, Nadir Arber. "Gammora": Selective killing of cancer cells bearing CD24 by viral integrase [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5922.