Abstract
Gene-engineered T-cell products have been developed for immunotherapy to treat cancers, with great success observed in haematological malignancies but limited efficacy in treating solid cancers. TCR-engineered T cells utilize transferred TCRs targeting tumour-associated and cancer-specific peptides presented by MHC molecules. The CD3ζ chains are part of the TCR-CD3 complex expressed by T cells and mediate signal transduction when the TCR binds to MHC-presented peptides. In this study, we explored whether co-stimulation domains, that were effective in improving the function of T cells engineered with chimeric antigen receptors (CARs), can be exploited to improve the functionality of TCR-engineered T cells. We inserted the signalling domains of CD28 or 4-1BB at the membrane proximal or the membrane distal position of the intracellular tail of CD3ζ and engineered human T cells to express a specific TCR in combination with either modified CD3ζ or unmodified control. Antigen-specific in vitro stimulation assays revealed that T cells expressing CD3ζ constructs with CD28 signal domains displayed enhanced peptide-specific IL-2 production and, following repeated antigen stimulation, expanded to substantially greater numbers than T cells expressing unmodified CD3ζ. Importantly, greater expansion seen with the CD28-containing ζ did not result in any reduction of effector function as assessed by peptide-specific cytotoxicity and cytokine production. The data indicate that modification of the CD3ζ chain with a CD28 signal motif provides an opportunity to improve antigen-specific expansion and effector function of TCR-engineered T cells by combining signal 1 and co-stimulatory signal 2 in one molecular TCR-CD3 complex.