Overcoming Regulatory T Cell Suppression through Ex Vivo Priming of Natural Killer Cells for Cancer Immunotherapy

Background: The tumour microenvironment (TME) promotes both immune evasion and cancer progression. TME is an essential component of promoting invasion, metastasis, as well as the ability to resist therapeutic interventions. One of the key aspects of this environment that supports the growth of cancerous cells is the recruitment of immunosuppressive cells such as the T regulatory cell. These immunosuppressive cells, Treg, often impairs the NK cell’s function, which normally recognises cancer cells. This project has found a way to improve the NK cell function by tumour-priming NK, which enhanced anti-tumour functions for clinical use. The aim of this study is to investigate the relationship between NKs and Tregs in cancer cells. In particle to examine if by tumour-priming, NK can overcome the suppression of Treg in vitro. NK and Treg cells were isolated from leukocyte cone and Treg cells were expanded, and suppression was performed. NK cells were prime with cytokine, IL2 and CTV-1 cell line and co-incubated with K562, Raji and OVCAR3 cancer cell line, with and without Treg. These were followed by 4h of cytotoxicity assays and were read in flowcytometry or xCELLigence. The Treg cells after the expansion were found to be 90% suppressive at ratio of 1:2 (E:T). The cytotoxicity assays that were carried for 4h, showed a reduction in the NK cells cytotoxicity, with the addition of Treg cells, as against the NK cells with 3 different cell line K562, Raji and OVCAR3. In case of OVCAR3, at 4h of cytotoxicity assay, the Treg cells completely inhibited NK cell cytolysis. As for all the targeted cell lines, when the NK cells were primed with IL2, there was an increased in cytotoxicity, even with the addition of Treg cells. The TpNK cells cytotoxicity were not much higher than the NK cells; however, it manages to completely inhibit the Treg suppression. The NK cells, by themselves are not capable of inhibiting the suppression of Treg cells, but with additional treatments, like with IL2 or CTV-1, their resistance to Treg influence increases. TpNK cell manages to completely inhibits the Treg suppression.