Metabolic Biomarkers of Response of Mantle Cell Lymphoma to Bruton Tyrosine Kinase Inhibition

Due to increased application of kinase inhibitors to cancer therapy, there is a need to develop noninvasive early detection methods to monitor the activity of treatment in patients. We aim to develop methods to address three critical issues – 1) early detection of tumor response or resistance to therapy, particularly by noninvasive imaging techniques, 2) defining detailed mechanisms of drug response and resistance, and 3) using this information to overcome drug resistance. Noninvasive in vivo monitoring of cell signaling pathways is not feasible, and monitoring of changes in tumor volume is a late and often misleading response indicator. FDG PET, while ideal for tumor detection is not response predictive, likely because it evaluates only the first two steps of the glycolytic pathway, while tumors are able to use other pathways to process nutrients required for their growth. We propose a novel alternative – to detect response by monitoring the key metabolic pathways regulated by the kinase inhibitor. Our basic premise is that changes in tumor metabolism are earlier and more reliable indicators of therapeutic response than changes in tumor volume. We focus on the Bruton's tyrosine kinase (BTK) signaling pathway using an FDA-approved BTK inhibitor, ibrutinib (IBR), as well as two second-generation inhibitors of mantle cell lymphoma (MCL). We propose to use a comprehensive genomic/phosphoproteomic/metabolomic approach to delineate the mechanism of response and resistance to BTK inhibition. In preliminary studies we have evaluated index MCL cell lines, one of which (MCL-RL) is highly sensitive to IBR and another (JeKo-1) is resistant. Preliminary RNA-Seq analysis indicates that BTK modulates expression of many genes involved in key metabolic pathways including glycolysis, the pentose shunt, TCA cycle and glutaminolysis. By measuring metabolic flux through these pathways before and after treatment with IBR, we will determine which of these pathways are critical to response and resistance. We found that in JeKo-1 cells glutaminolysis is critical to IBR resistance and can be overcome with glutaminase inhibitors. We have developed and validated novel 13C MRS and 13C LC-MS methods to monitor flux through key pathways of tumor metabolism and propose to use these methods on the MCL models in in vitro and in vivo studies to define the mechanism of response and resistance to the drug. Lactic acid, alanine and choline have emerged as potential metabolic biomarkers of response of MCL cells to BTK inhibition that can be monitored by 1H MRS using the HadSel-MQC pulse sequence developed by us. In Aim 1, we will perform genomic and metabolomic studies of response and resistance to BTK inhibition in cell lines and primary cells derived from MCL patients. In Aim 2, we will utilize in vitro 1H MRS and 13C MRS and LC-MS to verify and quantitate perturbations of metabolic fluxes in pathways identified in Aim 1 as potential imaging biomarkers of BTK inhibition. Finally, in Aim 3 we will utilize 1H, 13C & 31P MRS imaging and LC-MS analysis in mouse xenografts of MCL to validate the metabolic biomarkers of BTK inhibition identified in Aims 1 & 2.