Abstract 510: Identification and characterization of immunogenic epitopes from CD133 and their potential for use to immunologically target cancer stem cells

CD133 is a marker that identifies cancer stem cells (CSC) on many solid tumors and its expression has been correlated with shortened survival. Although expressed on many normal tissues and stem cells, CD133 is overexpressed on CSC and normal SC are negative or express low levels of MHC making them less sensitive to recognition by CD8+ cytotoxic T lymphocytes (CTL). Potential CTL epitopes were identified by algorithms to predict binding to HLA-A2. Binding studies showed high affinity binding and low off rates for four candidate epitopes. CTL induction studies using IL-12 secreting dendritic cells to stimulate CD8+ T cells evaluated the immunogenicity of the candidate peptides after three or four weekly in vitro stimulations. Multimer and IFNγ responses were observed with CD133-753, 405 and 708 epitopes. Subsequent studies demonstrated killing of T2 cells loaded with peptide. To evaluate the potential for autoimmunity, mouse homolog peptides of the 753 and 405 epitopes that were shown to have high affinity binding to human HLA-A2 were used to immunize HLA-A2 transgenic mice (9CB6F1-Tg (HLA-A*0201/H2-Kb) A*0201). Mice were immunized 3 times at 3 week intervals in IFA + HBV helper peptide and spleens were harvested 2 weeks after the last immunization and stimulated in vitro for one week with peptide pulsed LPS stimulated- APC. An additional group was sacrificed 6 weeks after the last immunization and studied. IFNγ ELISpot assays showed immune responses to the 753 and 405 peptides in 35% and 40% of mice. Organs, including heart, lung, liver, kidney, stomach, intestine, brain, bone marrow, gonads, and eyes from mice with immune responses were found to be negative for lymphocytic infiltrations supporting a lack of autoimmunity related to the immune response to these peptides. Together these studies support the safety and immunogenicity of these peptides as a potential vaccine to target CD133 cancer stem 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 510. doi:1538-7445.AM2012-510