UC San Diego

The identification of novel biomarkers and therapeutic targets in advanced cancer is critical for improving cancer diagnosis and therapeutics. Survivin (SV) is highly expressed predominantly in most cancer cells and tissues but is absent or undetectable in terminally differentiated normal adult tissues. Therefore, it functions as an almost universal tumor antigen. Peptides are short chains of amino acids linked by peptide bonds. To obtain novel SV decamers that are able to induce SV-specific cytotoxic T lymphocytes (CTLs) with a higher cytotoxic efficiency against cancer cells, major histocompatibility complex (MHC) peptide binding algorithms were conducted to predict nine modified SV₉₅ decamers (from SV_95-2 to SV_95-10) based on the natural SV_95-104 peptide sequence of ELTLGEFLKL (here defined as SV_95-1). The fluorescent density of each SV₉₅ peptide was determined by a MHC stability assay, followed by the generation of SV₉₅-specific CTLs with each SV₉₅ peptide (from SV_95-1 to SV_95-10) and human dendritic cells (DCs) loaded with Poly(lactic-co-glycolic) acid (PLGA) nanoparticles encapsulated with SV₉₅ peptide. Finally, IFN-γ ELISpot and CytoTox 96^® Non-Radioactive Cytotoxicity Assays were employed to verify their cytotoxic efficiency of the SV₉₅-specific CTLs generated with the corresponding artificial antigen presenting cells (aAPCs) containing SV₉₅ (SV_95-1 to SV_95-10) peptide. Furthermore, the cytotoxicity of the SV₉₅ specific CTLs generated with nine mutated SV₉₅ peptides was compared to the one generated with natural SV_95-1 peptide and TIL2080 cells. The results indicated that the HLA-A2-restricted mutated SV₉₅ epitope decamers (SV_95-6 and SV_95-7) showed significant higher binding ability compared to natural peptide SV_95-1 in MHC stability assay. More importantly, SV_95-specific CTLs with higher cytotoxicity were successfully induced with both SV_95-6 and SV_95-7 peptides, which significantly eliminated target cells (not only SV_95-1 peptide pulsed T2 cells, but also both HLA-A2 and SV positive cancer cells) when compared to those generated with natural SV_95-1 peptide and TIL2080 cells. These findings suggest that the SV_95-6 and SV_95-7 peptides are two novel HLA-A2-restricted CTL epitopes and may be useful for the immunotherapy for patients with survivin expressing cancer.