Development of allo-restricted cytotoxic T cell specific for TWIST a potential novel target for cancer immunotherapy of childhood cancers
Session type: Poster / e-Poster / Silent Theatre session
University College London Institute of Child Health & Great Ormond Street Hospital, London, UK
Despite the characterisation of a vast number of tumour-associated antigens; the selection of which targets to use in immunotherapeutic cancer treatments still remains crucial. TWIST is a basic helix-loop-helix (bHLH) transcription factor found to regulate tumour survival, progression and metastasis. It is expressed in numerous tumour types such as neuroblastoma and osteosarcoma. Its expression levels in normal tissues are limited to the placenta and the testis at low levels, therefore we hypothesis TWIST as an attractive target for T-cell mediated therapy.
We identified two peptide sequences derived from TWIST which binds to HLA-A0201 molecules in vitro: KLAARYIDFL (KLA) and SLNEAFAAL (SLN). Two different approaches were then used to test the immunogenicity of the peptides, stimulation of CTL from autologous and allogeneic T cells respectively. Initial screening of four HLA-A0201+ healthy donors failed to induce a TWIST peptide specific CTL response. The lack of immune response could be the consequence of complete tolerance within the self-restricted T cell repertoire. To overcome this, we developed an optimised stimulation protocol incorporating MHC class I pentamer (KLAARYIDFL/HLA-A0201) staining and magnetic cell sorting. With this approach a rare antigen-specific T cell population was isolated from HLA-A0201 negative donors. Using this novel approach a CTL line against KLA restricted to a non-self MHC class I molecule was generated from allogeneic sources and was devoid of alloreactivity.
The initial demonstration of immunogenicity of TWIST peptides provides the bases to generate specific CTL lines to test the specific lysis of TWIST expressing tumour cell lines. In addition, with further development of the methodology it could be exploited to circumvent self-tolerance and to study the allo-restricted T cell repertoire of HLA-mismatched donors against other tumour-associated antigens.