Discovery of the mechanisms governing Natural Killer T-cell activation and therapeutic potential in cancer

About This Grant

Abstract While immunotherapies have revolutionized the treatment of cancer over the past 15 years, many patients still do not respond to these treatments, leaving a sizeable therapeutic need unmet. Recently, several studies have focused on an understudied class of lipid antigen responsive T cells, called Natural Killer T-cell (NKT), to improve immunotherapy response rates. NKT cells recognize lipid antigens presented on the receptor CD1d via their T cell receptor and help support anti-tumor immune responses by producing cytokines and killing immunosuppressive myeloid cells and CD1d+ tumor cells. NKT cells effectively infiltrate tumors and correlate with good prognosis in many types of human cancer; however, how they are recruited to tumors, what tumor specific lipid antigens they recognize, and mechanisms of immune evasion are entirely unknown. These three unanswered questions represent a gap in our understanding of NKT cell biology that has become increasingly important to fill as NKT cell therapies continue to show promise. In the F99 phase of this proposal, I will address the question of how NKT cells are recruited to tumors and whether increasing NKT cell trafficking to tumors could enhance the efficacy of current generation NKT cell therapies. Leveraging the unique tumor model system I developed in our lab, where deletion of the mitochondrial gene Ndufs4 induces NKT cell accumulation in melanoma tumors, I will: 1) Define the mechanism of NKT cell recruitment to Ndufs4 deleted tumors by adoptively transferring labeled NKT cells into tumor bearing mice; 2) Determine the metabolic pathways and components necessary for NKT cell recruitment to Ndufs4 deleted tumors by co-culturing NKT cells with tumor cells treated with a panel of siRNAs; and 3) Determine the synergy between Ndufs4 deletion and NKT cell therapies by treating tumor bearing mice with chimeric antigen receptor (CAR) expressing NKT cells. This aim will support my hypothesis that altered mitochondrial metabolism in Ndufs4 deleted cells drives increased trafficking of NKT cells to tumors and this increased trafficking will improve the efficacy of current generation CAR-NKT cell therapies. In the K00 phase of this proposal, I will work under an expert in CD1 biology and lipid ligand identification to address the questions of how epithelial cancers evade NKT cell surveillance by downregulating CD1d and identify lipid tumor specific antigen (TSAs) and the structural basis of their recognition by NKT cells by: 1) Determining the regulators of CD1d using a genome-wide CRISPR screen; 2) Identify CD1d TSAs in prostate cancer and their therapeutic utility using a CD1d purification methodology developed by my K00 sponsor; and 3) Define the structural basis of CD1d TSA recognition of NKT cells using X-ray crystallography. This aim will support my hypothesis that epigenetic changes drive CD1d repression in epithelial cancers and that NKT cells can recognize CD1d bound TSAs to promote anti-tumor immunity. Altogether, this proposal will significantly advance our knowledge of NKT cell behavior and potential therapeutic benefits in cancer.