Title: Targeting the stress kinase GCN2 to overcome proteasome inhibitor resistance in multiple myeloma
Funder: Cancer Research UK

Abstract: BACKGROUND Multiple myeloma (MM) is a malignancy of plasma cells, the terminally differentiated effector cells of the humoral immune system. MM is the second most common haematopoietic cancer and was diagnosed in over 5500 patients in the UK in 2015. MM accounts for 2% of all cancer deaths in the UK, and only 33% of patients survive for more than 10 years. Inhibitors of the proteasome, the main cellular protein break-down machinery, form the backbone of multiple treatment regimens for newly diagnosed and advanced stage patients. However, proteasome inhibitor (PI) tratment is limited by primary or secondary resistance in most patients. Here, we propose to test if GCN2 (EIF2AK4) is a valid drug target to overcome PI resistance. GCN2 is a kinase that is activated by intracellular amino acid shortages, a major effect of PIs, and acts to protect cells from this stress by temporarily reducing protein synthesis. AIMS To determine whether GCN2 inhibition can be a valid therapeutic strategy to optimise PI-based anti-myeloma therapies and/or to overcome PI resistance. METHODS We will use a comprehensive combination of bioinformatic analyses of molecular and clinical trial data and patient samples, genetic depletion approaches and tool inhibitors in cell lines, and xenografting studies in mice. In particular, we will (1) investigate whether GCN2 mRNA expression in primary MM cells (MMCs) correlates with molecular abnormalities and clinical outcomes; (2) determine whether functional GCN2 depletion sensitises MMCs to PIs; (3) identify biomarkers that demonstrate successful GCN2 inhibition, using a paired transcriptomic and phosphoproteomic approach (4) determine whether GCN2 kinase activity is required for cytoprotection from PI effects; (5) establish whether GCN2 depletion reduces MM xenograft growth and improves the anti-myeloma effects of PI treatment in mice; (6) establish a biochemical GCN2 activity assay and perform a small scale inhibitor screen (7) generate a biobank of primary MM and non-MM cells. HOW THE RESULTS OF THIS RESEARCH WILL BE USED Should the target validation experiments outlined above confirm GCN2 as a promising target, we will seek further drug discovery funding for the next phase including further screening/assay development, and hit-lead identification with pharmacokinetic/ADME-toxicology optimisation. Lead compounds will be triaged based on efficacy and toxicity in cell models (cell lines and primary) and in vivo MM xenografts. If successful, this next chapter of work will identify a lead or possibly preclinical candidate for MM therapy ready for formulation, toxicology and safety prior to Phase 1 trials.

Lay abstract: BACKGROUND Multiple myeloma (MM) is a malignancy of plasma cells, the terminally differentiated effector cells of the humoral immune system. MM is the second most common haematopoietic cancer and was diagnosed in over 5500 patients in the UK in 2015. MM accounts for 2% of all cancer deaths in the UK, and only 33% of patients survive for more than 10 years. Inhibitors of the proteasome, the main cellular protein break-down machinery, form the backbone of multiple treatment regimens for newly diagnosed and advanced stage patients. However, proteasome inhibitor (PI) tratment is limited by primary or secondary resistance in most patients. Here, we propose to test if a kinase that is activated by intracellular amino acid shortages, a major effect of PIs, and acts to protect cells from this stress by temporarily reducing protein synthesis, could be a valid drug target to overcome PI resistance. AIMS To determine whether kinase inhibition can be a valid therapeutic strategy to optimise PI-based anti-myeloma therapies and/or to overcome PI resistance. METHODS We will use a comprehensive combination of bioinformatic analyses of molecular and clinical trial data and patient samples, genetic depletion approaches in cell lines, and xenografting studies in mice. HOW THE RESULTS OF THIS RESEARCH WILL BE USED Should the target validation experiments outlined above confirm the kinase as a promising target, we will seek further drug discovery funding for the next phase including further screening/assay development, and hit-lead identification with pharmacokinetic/ADME-toxicology optimisation. Lead compounds will be triaged based on efficacy and toxicity in cell models (cell lines and primary) and in vivo MM xenografts. If successful, this next chapter of work will identify a lead or possibly preclinical candidate for MM therapy ready for formulation, toxicology and safety prior to Phase 1 trials.

Research activity codes: 5.1 PHARMACEUTICALS
Health categories: CANCER AND NEOPLASMS