Abstract 1488: Development of anti-nucleolin antibodies with broad spectrum anticancer activity and negligible toxicity to normal cells

Nucleolin has multiple, unique functions in cancer cells, including the shuttling of ligands from the cell surface to the cytoplasm and the stabilization of oncogene and cytokine mRNAs that have an AU-rich nucleolin binding element in their 3’-UTRs. We developed a panel of anti-nucleolin antibodies that exploit the temperature-dependent shuttling function of nucleolin to gain access to the cytoplasm of human tumor cells and induce oncogene mRNA destabilization. Several lines of evidence indicate that our fully human monoclonal IgG1 antibody, CP101.2C8, targets nucleolin and penetrates tumor cells. CP101.2C8 bound tightly to human recombinant nucleolin (Kd = 26 ± 7 nM, SEM.) and to plasma membrane nucleolin of human tumor cells. Confocal microscopy of Panc-1 and DU-145 tumor cells incubated at 37 0C with CP101.2C8 revealed punctate localization of the antibody in the plasma membranes of these cells and internalization of the antibody into the cytoplasm. The localization of the antibody within foci in the plasma membrane suggested that the antibody was bound to nucleolin that was incorporated into lipid rafts within the plasma membrane. MCF-7 human breast cancer cells were made more than 100-fold resistant to CP101.2C8 by growing the cells in increasing concentrations of the antibody. The resistant cells regained contact inhibition and had a 10-fold lower level of cytoplasmic nucleolin compared to the parental MCF-7 cells. CP101.2C8 is a potent inhibitor of tumor cell viability in vitro. IC50 values of less than 1 μg/ml were obtained for CP101.2C8 versus MV4-11 AML cells, colon, prostate, and lung cancer cells as well as CD33+-CD24- stem cells from MDA-MD-231 breast cancer cells. In contrast, the IC50 concentrations of CP101.2C8 versus normal human B and myeloid cells, breast epithelial cells and lung fibroblasts were greater than 10 μg/ml. Unlike the tumor cells, these normal cells did not express detectable levels of nucleolin in either the plasma membrane or cytoplasm. A fully human recombinant CP101.2C8 is also potent in reducing the viability of MV4-11 cells (IC50 = 0.4 μg/ml). Groups of 10 nu/nu mice bearing SC MV4-11 tumor xenografts were injected IV (every 3 days x 6) with either 10 mg/kg CP101.2C8 or 10 mg/kg of a human IgG1 isotype control antibody. Tumor progression to the 2,000 mm3 endpoint was observed between 24-41 days in all mice treated with the control antibody, while 3/10 of the CP101.2C8-treated mice were long-term survivors that did not reach the endpoint by day 76. The hazard ratio calculated from the Kaplan-Meier plot was 0.22. CP101.2C8 was well tolerated by all the mice; the only adverse event observed was a transient loss in mean body weight of 16%. The widespread and aberrant expression of the multi-functional protein nucleolin in human tumor cells, in contrast to the corresponding normal cells, explains both the broad-spectrum anticancer activity and tumor selectivity of antibody CP101.2C8. Citation Format: Daniel J. Fernandes, Baby G. Tholanikunnel. Development of anti-nucleolin antibodies with broad spectrum anticancer activity and negligible toxicity to normal cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1488.