CCLG1
A chimeric T cell receptor targeting the antigen GD2 for the treatment of neuroblastoma
Simon Thomas1, Brian Philip1, Amit Jathoul1, John Anderson2, Martin Pule1
1University College London Cancer Institute, London, UK, 2University College London Institute of Child Health, London, UK
Background
Chimeric T cell receptors (cTCRs) are artificial receptors constructed by linking the antigen-binding moiety of a monoclonal antibody to activation motifs from endogenous T cell receptors. Introduction of the cTCR into T cells by means of a replication-deficient retrovirus serves to alter the cells’ specificity re-targeting them to the antigen to which the original monoclonal antibody was raised.
Method
We have constructed a cTCR based on a humanized antibody which recognizes the ganglioside GD2, an antigen commonly expressed by multiple tumours including neuroblastoma, melanoma and osteosarcoma. We have also constructed a murine counterpart to this receptor incorporating the antigen binding region from the original murine antibody.
Results
When expressed in healthy-donor lymphocytes both the humanized receptor and its murine equivalent efficiently mediate specific lysis of GD2-bearing neuroblastoma cells to comparable levels as assessed by chromium-release cytotoxicity assay. Whilst both receptors stimulate substantial proliferation of transduced T cells in the presence of GD2-expressing Lan-1 cells the humanized version induces an approximate 2-fold greater expansion compared to its murine counterpart. Surprisingly, T cells expressing the humanized receptor secrete higher levels of the cytokines IL2 and interferon-γ compared to T cells expressing the murine version upon co-culture with GD2-expressing tumour cells. Additionally we have coupled the cTCR to a caspase-based suicide gene. Upon administration of a chemically inert dimerization compound the suicide gene becomes active and gene-modified T cells selectively undergo apoptosis. This modification gives us a rapid, effective means to eradicate exogenous T cells from the patient should therapy-related complications arise.
Conclusion
We have constructed a highly efficient, fully-humanized cTCR for the treatment of neuroblastoma. By removing xenogeneic sequences from the receptor we aim to prevent a host immune response thus greatly increasing the persistence of exogenous, genetically modified T cells in the patient in order to provide life-long protection from tumour metastases and later growths of GD2-expressing cancers.
