Unravel the role of extracellular NNMT (eNNMT) in the modulation of prostate cancer (PC) tumor immune microenvironment (TIME)

Objective

Prostate cancer (PC) is the most common male cancer in the United Kingdom and more effective treatments are needed to control the lethal late-stage disease, termed castration-resistant PC (CRPC). CRPC is largely refractory to immunotherapeutic interventions mainly due to its tumour-immune microenvironment (TIME) with low infiltration of activated anti-tumour immune cells. Nicotinamide N-methyltransferase (NNMT) is a metabolic enzyme which catalyses the transfer of methyl groups from S-adenosylmethionine to nicotinamide. Independent studies have implicated NNMT upregulation in sustaining aggressiveness of a specific subset of CRPC with stem cell-like features (CRPC-SCL), in several cellular and organoid models. We’ve recently described a “moonlighting” function of this enzyme, which can be secreted by cancer cells (extracellular NNMT – eNNMT) and activate TLR4-dependent NF-kB signalling in macrophages. Preliminary data demonstrate that PC secrete eNNMT, but how eNNMT may modulate the TIME, remains unknown. This project aims to elucidate the role of eNNMT in shaping the TIME of CRPC-SCL. eNNMT release by CRPC-SCL murine cells and organoids, overexpressing NNMT will be quantified by ELISA. Using the state-of-the-art micro-mapping technology, we will identify eNNMT interactors in immune cells, to gain insight into the signalling pathways primed by eNNMT. Functional assays will be performed in co-cultures of CRPC-SCL models and immune cells, in the presence or absence of eNNMT blockage. Defining eNNMT as a mediator of immune modulation in CRPC-SCL will provide mechanistic insights into tumour–immune crosstalk and establish the basis for novel immunotherapeutic strategies using eNNMT-neutralizing antibodies. Importantly, this project will also establish a pipeline to identify interactors of secreted factors/biomarkers with immune modulatory potential.