Abstract 2244: Internalization of basigin-2, a poor prognosis marker, by a monoclonal antibody

Abstract

Basigin-2 (EMMPRIN, CD147) is widely expressed on the surface of numerous tumor types and is associated with poor prognosis. Basigin is an integral membrane glycoprotein also expressed on numerous normal cell types. Several functions have been described for basigin-2 within both normal and malignant tissues. The best characterized is its ability to induce the expression of matrix metalloproteinases in stromal cells. As such, it is suggested to play a role in tumor metastasis. Because of its association with poor prognosis and possible role in metastasis, we examined the ability of basigin-2 to be targeted on the cell surface and internalized as a possible gateway for entry into tumor cells, or for down-regulation for inhibition of metastasis. Belton et al. have documented internalization of basigin-2 by a recombinant soluble protein corresponding to the extracellular domain (ECD) of basigin-2 (J Biol Chem, 2008, 283:17805). We have extended this investigation to examine antibody-mediated endocytosis. A monoclonal antibody to the basigin ECD (also reported in Belton et al.) has been used in an internalization assay using biotinylated antibody mixed with streptavidinylated-saporin (the ribosome-inactivating protein). This complex will eliminate cells only if there is antibody-mediated endocytosis, since saporin has no mechanism of cell entry. HeLa cells, which are known to express basigin-2, were challenged and a potent cytotoxicity was observed: the ED50 of the biotinylated antibody-streptavidin-saporin complex is 370 pM. This is evidence that the antibody internalizes in HeLa cells. Similar data were observed with ovarian carcinoma cells (OVCAR3, SKOV3). Non-tumor cells with low expression have low sensitivity to the complex and there was a correlation between basigin-2 expression on the cell surface and cytotoxicity. We conclude that basigin-2 internalizes in response to antibody binding. Further work is necessary to determine if this can be used for introduction of molecules into basigin-2-expressing cells or if down-regulation would have an effect on metastasis promoted by this poor prognosis molecule. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2244.