Novel Survivin Peptides Screened With Computer Algorithm Induce Cytotoxic T Lymphocytes With Higher Cytotoxic Efficiency to Cancer Cells.

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 SV(95)decamers (from SV(95-2)to SV95-10) based on the natural SV(95-104)peptide sequence of ELTLGEFLKL (here defined as SV95-1). The fluorescent density of each SV(95)peptide was determined by a MHC stability assay, followed by the generation of SV95-specific CTLs with each SV(95)peptide (from SV(95-1)to SV95-10) and human dendritic cells (DCs) loaded with Poly(lactic-co-glycolic) acid (PLGA) nanoparticles encapsulated with SV(95)peptide. Finally, IFN-gamma ELISpot and CytoTox 96(R)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 SV95-10) peptide. Furthermore, the cytotoxicity of the SV(95)specific CTLs generated with nine mutated SV(95)peptides was compared to the one generated with natural SV(95-1)peptide and TIL2080cells. The results indicated that the HLA-A2-restricted mutated SV(95)epitope decamers (SV(95-6)and SV95-7) 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.