Manipulating T lymphocyte homing and activation for cancer immunotherapy

The immune system, and in particular CD8+ T cells, have the potential to eliminate tumours and novel immunotherapies are giving encouraging results for cancer patients. This thesis focuses on the improvement of one such therapy, adoptive T cell therapy. The aim of this thesis was to genetically modify human CD8+ T cells to enhance their anti-tumour potential for adoptive T cell therapy. One approach was to mutate the SH2 domain containing protein tyrosine phosphatase (SHP-1) gene to reduce T cell checkpoint inhibition. A second approach was to express a shedding-resistant form of L-selectin in T cells to promote T cell homing. In this thesis, the rapid shedding of L-selectin within minutes after TCR stimulation was shown to be ADAM17 dependent. Furthermore, new data indicated a second proteolytic cleavage which is γ-secretase dependent. The shedding-resistant L-selectin (ΔM-N) was shown to resist proteolysis by both ADAM17 and γ-secretase. Previous work by our group and others has shown that the loss of SHP-1 leads to the enhanced entrance of T cells into proliferation and gives better protection against tumour growth in mice. To study the effect of SHP-1 loss in human CD8+ T cells, SHP-1 deficient tumour-specific T cells were generated by lentiviral delivery of a pair of SHP-1 specific zinc finger nucleases in conjunction with the Mel TCR. Populations of melanoma-specific CD8+ T cells containing a small fraction (< 8 %) of SHP-1 mutant cells showed no enhanced Mel526 target cell killing in vitro or in vivo in Mel526 xenograft bearing NSG mice. However, there was some suggestion of enhanced survival and/or proliferation in vitro of melanoma-specific CD8+ T cells containing a population of SHP-1 CD8+ mutant cells. Overall the proof of principle of gene-editing SHP-1 in T cell lines and primary CD8+ T cells was demonstrated which supports further exploitation of this approach for testing in adoptive T cell therapy strategies