Using chemokine sorting to imrpove NK cell function in an anti-tumour model

Abstract

Background & Aim The immune system plays an important role in checking the development of tumours. While many inroads have been made into the role various immune cell types play within the context of cancer, further research is required to identify new cellular targets and improve anti-tumour therapeutics. Natural killer (NK) cells are involved in tumour rejection through direct cytotoxic mechanisms and the release of inflammatory mediators. As they are important in anti- tumour defence and amenable to ex vivo expansion, as shown in a number of clinical settings, NK cells are a candidate immunotherapy for cancer. Methods, Results & Conclusion Recent publications have shown that in mice lacking the atypical chemokine receptor ACKR2, NK cells have an increased expression of the chemokine receptor CCR2. ACKR2 KO animals demonstrate an increased protection from the development of metastatic lesions within the lungs compared to WT controls. Superior infiltration into the tumours by CCR2+ NK cells resulted in more efficient killing, and thus greater rejection of the newly-forming tumours. Here we provide evidence that CCR2+ NK cells can be isolated from the mouse using a GMP-compatible chemokine-based fluorescence sorting system, and that they are more capable than their CCR2- counterparts at inducing tumour cell death and reducing tumour burden following adoptive transfer in the B16F10 cancer model. In addition, we have generated preliminary data highlighting differential expression of CCR2 in human NK cells from healthy donor blood. Human NK cells were identified using CD56 expression and divided into two populations based on the intensity of the staining. Both CD56bright and CD56dim NK cells are capable of expressing CCR2. We have developed an adapted protocol for culturing and expanding NK cells, showing that expanded NK cells retain their phenotype and cytotoxicity over time. This is crucial to achieve a suitable cell number for potential therapeutic applications. We have performed multiple experiments to optimise the conditions for the maintenance of CCR2 expression and upregulation of the receptor on human NK cells. We are currently investigating whether CCR2+ human NK cells are equivalent to their murine counterparts, by assessing migratory capacity and cytotoxicity in vitro. Taking these data into account, we show that chemokine-sorted CCR2+ NK cells are a potentially viable immunotherapy for cancer.