CD8+ T cell recognition of polymorphic wild-type sequence p53_65–73 peptides in squamous cell carcinoma of the head and neck

Abstract

The TP53 tumor suppressor gene contains a well-studied polymorphism that encodes either proline (P) or arginine (R) at codon 72, and over half of the world’s population is homozygous for R at this codon. The wild-type sequence (wt) p53 peptide, p53_65–73, has been identified as a CD8+ T cell-defined tumor antigen for use in broadly applicable cancer vaccines. However, depending on the TP53 codon 72 polymorphism of the recipient, the induced responses to the peptides incorporating R (p53_72R) or P (p53_72P) can be “self” or “non-self.” Thus, we sought to determine which wt p53_65–73 peptide should be used in wt p53-based cancer vaccines. Despite similar predicted HLA-A2-binding affinities, the p53_72P peptide was more efficient than the p53_72R peptide in HLA-A2 stabilization assays. In vitro stimulation (IVS) of CD8+ T cells obtained from healthy HLA-A2⁺ donors with these two peptides led to the generation of CD8+ T cell effectors in one-third of the samples tested, at a frequency similar to the responsiveness to other wt p53 peptides. Interestingly, regardless of their p53 codon 72 genotype, CD8+ T cells stimulated with either p53_72P or p53_72R peptide were cross-reactive against T2 cells pulsed with either peptide, as well as HLA-A2⁺ head and neck cancer (HNC) cell lines presenting p53_72P and/or p53_72R peptides for T cell recognition. Therefore, the cross-reactivity of CD8+ T cells for the polymorphic wt p53_65–73 peptides, irrespective of their p53 codon 72 polymorphism, suggests that employing either peptide in wt p53-based vaccines can result in efficient targeting of this epitope.