Targeting natural killer cell receptors for immunotherapeutic benefit

Hepatocellular carcinoma (HCC) arises in the liver, is the fifth most common cancer worldwide and the third commonest cause of cancer death. On a worldwide basis it arises on the background of viral hepatitis, but its prevalence is increasing in the UK due to the rise in numbers of people with non-alcoholic fatty liver disease, which is associated with obesity. It remains difficult to treat, in part because it arises in livers that are usually damaged by cirrhosis, which means that chemotherapeutic agents are poorly tolerated by patients. Furthermore, patients present in advanced stages of disease beyond the time when curative surgical treatment is possible. The outlook for these patients is poor and therefore newer therapies are needed.
Natural killer (NK) cells are cells of the innate immune system which have anti-cancer properties and the liver is an organ where NK cells accumulate. We therefore propose that NK cells are a potential therapeutic for HCC. NK cell targeting therapies are currently undergoing much investigation, but are often cumbersome and expensive. Our recent work has suggested that a novel therapeutic strategy involving vaccination, might be an option for developing better NK cell targeting strategies. We propose using a DNA vaccine that encodes a sequence for a protein that our previous work has shown is recognised by the NK cell receptor KIR2DS2.
We will first optimise the procedure for delivering this DNA vaccine. The DNA vaccine will then be tested in preclinical models to determine their potential as therapeutics, focussing on HCC as the therapeutic target.
As part of this project we will also test the novel concept that NK cells can recognise tumour antigens in a similar way to another immune cell, the cytotoxic T cell. These cells recognise small fragments of cellular proteins which are displayed on the cell surface by specialised proteins called MHC class I molecules, Our on-going work shows that one small peptide, derived from the protein XPO1, is a potential target for NK cells by binding MHC class I and KIR2DS2 and then activating NK cells. The XPO1 protein is upregulated in many cancers including hepatocellular carcinoma. We therefore consider that it provides a rationale for our NK cell therapy of HCC. We will perform in vitro and in vivo experiments to test the hypothesis that KIR2DS2+ NK cells recognise XPO1 as a tumour antigen.
Our work tests a novel strategy for NK cell therapy, which has potential translational and clinical benefit for HCC, and for other cancers. We believe it would have wide applicability as both a monotherapy and in conjunction with currently available immunotherapeutic strategies.

The aim of this project is to test and develop natural killer (NK) cell therapy for hepatocellular carcinoma (HCC). We have identified that the NK cell receptor KIR2DS2 recognizes peptide:MHC complexes. This project will exploit this finding and determine whether this feature of KIR2DS2 can be targeted for therapeutic benefit. We have generated preliminary data suggesting that a DNA vaccine strategy targeting KIR2DS2 can be used to activate NK cells and that these have potential to inhibit tumour growth in two different models. The overall goal is to optimise this strategy by:
a) Addressing co-stimulation of NK cells using this vaccine, by targeting complementary signalling pathways. We will target TLR activation, IL-15 stimulation and the cell surface receptors, NKG2D.
b) Refine the vaccine strategy to bring it closer towards translation to the clinic by: optimising delivery, testing additional vaccine constructs, investigating the phenotype of the NK cells generated, and performing pre-clinical testing.
c) Test a novel mechanism for tumour recognition by KIR2DS2+ NK cells, based on a cancer peptide derived from XPO1 that we have identified. For this we will define the HLA-C restriction of this peptide, and then test recognition by KIR2DS2+ NK cells in vitro, and then in an in vivo model of HCC.

NK cell therapy is an emerging field. We propose a novel strategy to target NK cells, which may have direct anti-tumour effects or, synergise with immunotherapies that target the adaptive immune system.

The major impact of the work outside of the academic community will be for health. The work is a study of a potential treatment strategy for cancer, and as hepatocellular carcinoma (HCC) is the third commonest cause of cancer death worldwide then this can have a widespread impact. The work will impact the UK, in which the prevalence of HCC is rising. However it could also l impact low and middle-income countries where HCC is especially prevalent, such as sub-Saharan Africa. Currently natural killer cell-based therapies are predominantly utilising adoptive transfer methods and so require expensive facilities for preparation and administration. The potential treatment strategy that could result from our work is a vaccine-based strategy which could be deployed in resource-poor areas. Although our work is focussed on HCC, it could have impact on other cancers and natural killer cell therapies are currently being trialled in haematological malignancies including acute myelogenous leukaemia, chronic lymphocytic leukaemia and multiple myeloma. It thus could have a broad health benefit to cancer treatment.

Additionally, our work has potential for translation into anti-viral vaccines as it is based upon peptides derived from flaviviruses. Such viruses include dengue virus, Zika virus, yellow fever, West Nile, Tick-borne encephalitis, Japanese encephalitis and hepatitis C viruses. There is therefore a potential for a wide health benefit. For instance, The World Health Organisation estimates that there are 390 million dengue infections per annum. Severely affected areas include African, Americas, Eastern Mediterranean, South-East Asia and Western Pacific regions; the Americas, South-East Asia and Western Pacific regions (http://www.who.int/denguecontrol/epidemiology/en/). As well as the potential for affecting health in these regions it will also have an indirect effect through encouraging research into these areas, bringing an added societal benefit.

The work can also have economic and commercial benefit. The global cancer market is currently estimated to be worth more than $40bn and is forecast to rise to over $119bn by 2021. Similarly, the current worldwide vaccine market to be worth $24billion rising to $61billion by 2020. If the work is successful then it could therefore have substantial economic impact in these markets both within and outside of the UK. In addition, we have filed for patents on the peptides within this proposal and so there is an immediate opportunity for commercialisation of the work through the pharmaceutical industry, which could be done at a local, national or international levels.