Amf-1c-120: An Antibody Specific For Misfolded Prion Protein Expressed On Ovarian Cancer Cells.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC We tested the hypothesis that cancer cells might display misfolded protein molecules at the cell surface, due to oxidative covalent modifications, defective glycosylation, and/or other factors relevant to cancer. We developed a computational algorithm to predict regions of proteins which were most likely to undergo loss of structure and resemble free unstructured peptides against which antibodies could be generated and screened. Antibodies directed against these misfolding-prone regions, termed disease-specific epitopes (DSEs), are therefore expected to recognize cancer cells while sparing natively folded proteins on healthy cells. We have applied this strategy to develop an antibody that is specific for ovarian cancer cells, which does not bind to normal ovarian epithelium. Using the ProMIS™ computational algorithm to predict unstable regions in proteins, three DSEs in the prion protein (PrP) were identified. Ultra-high sensitivity antibodies are required for binding to isolated misfolded protein molecules at the cell surface, and thus rabbits were immunized with peptides corresponding to the PrP DSE sequences and rabbit monoclonal anti-peptide antibodies were generated. One antibody, AMF-1c-120, has sub-nanomolar binding affinity for denatured PrP, but does not bind to native PrP. AMF-1c-120 binds to four ovarian tumor cell lines and one ovarian tumor implanted and propagated in mice, but does not bind to normal ovarian epithelial cells. Proteinase K sensitivity of the AMF-1c-120 epitope is consistent with partial denaturation of PrP at the cell surface of ovarian cancer cell lines. Preclinical efficacy studies are in progress to investigate the anti-tumor effects of AMF-1c-120. Citation Format: Marni D. Uger, Viengthong Chai, Veronica Ciolfi, Hui Chen, Ewa Plawinski, Tapfuma Mutukura, Andrew Sage, Ryan Demers, Leo Lau, Pierre Lee, Xiuwen Liu, Jun Guan, Yuzhuo Wang, William C. Guest, Steven S. Plotkin, Neil R. Cashman. AMF-1c-120: an antibody specific for misfolded prion protein expressed on ovarian cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4636. doi:10.1158/1538-7445.AM2013-4636