Abstract 4623: Human anti-nucleolin antibodies with broad spectrum anticancer activity

Abstract

Extensive preclinical studies have validated nucleolin as a new therapeutic target in oncology. Confocal microscopy, immunohistochemistry, and cell fractionation studies have shown that this protein is highly overexpressed in the plasma membrane and cytoplasm of a wide variety of human hematological and solid tumor cells, but is usually undetectable on the cell surface or in the cytoplasm of the corresponding normal cells. We have utilized our licensed platform technology to generate a first-in-class panel of eight fully human monoclonal IgG₁ antibodies (HuMAbs). These antibodies bind specifically to nucleolin on the tumor cell surface, which in turn elicits potent cytotoxicity to a variety of human tumor cell lines. One such example is CP101, which killed MV4-11 (AML), MCF-7 (breast), DU145 (prostate), PANC-1 and MIA PaCa-2 (pancreas) tumor cell lines with IC₅₀ values ranging from (0.5-2.0 µg/ml; 3-12 nM) following exposure to the HuMAb for 96 hrs. These in vitro assays were performed in the absence of human complement and immune effector cells required for complement-dependent cellular cytotoxicity (CDCC) and antibody-dependent cellular cytotoxicity (ADCC), respectively. These results are consistent with published observations that anti-nucleolin HuMAbs can exploit the known shuttling function of cell surface nucleolin to gain intracellular access and induce direct tumor cytotoxicity. In contrast to its cytocidal effects on tumor cells, CP101 had no effect on the viability of either MCF-10A normal human breast epithelial cells or normal human CD19+ B cells, neither of which expresses nucleolin on the cell surface. In summary, the results suggest that anti-nucleolin HuMAbs are unique in that they can exert broad spectrum antitumor activity independently of the immune mechanism of CDCC and ADCC, while having no detectable effects on the viability of the corresponding normal cells.

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 4623. doi:1538-7445.AM2012-4623