Abstract 5423: ZAP70 alters metabolism in chronic lymphocytic leukemic cells

Abstract Chronic lymphocytic leukemia (CLL) has the highest incidence among adults in western countries. Prognosis of CLL is highly variable but one of the biomarker zeta-chain-associated protein 70 (ZAP70) over expression is associated with aggressive disease with time to treatment being 2.6 years for ZAP70 expressing (ZAP70+) patients and 8 years for ZAP70 deficient (ZAP70-) patients. Thus ZAP70 may play a role in CLL progression. Metabolic reprograming plays a central role in cancer progression and is altered in CLL cells. However, the role of ZAP70 in metabolism in CLL cells is remains unclear. We found that ZAP70 binds to pyruvate kinase M2 (PKM2). PKM2 is key isoform of pyruvate kinase which is rate limiting enzyme of the glycolytic pathway and provides a metabolic advantage to tumour cells allowing for increased growth. Our results also indicated the PKM2 is expressed in CLL cells and binding to ZAP70 is not affected by glucose starvation or treatment with kinase inhibitors. Furthermore immunofluorescence microscopy revealed that ZAP-70 and PKM2 colocalize in CLL cells in the cytoplasm. In addition, we found ZAP70+ cells have increased rate of oxygen consumption from basal level determined by addition of inhibitor (Oligomycin A) and mitochondrial uncoupler (FCCP). Simultaneously ZAP70+ cells also have higher extracellular acidification rates. This indicates ZAP70+ CLL cells have increased mitochondrial respiratory capacity with high glycolytic rate. In addition, fluorometric analysis indicates ZAP70+ CLL cells have high glucose consumption rate towards production of lactate compared to ZAP70- CLL cells. Collectively, our data reveals a new function for ZAP70, which is to regulate the Warburg effect and may play a role in CLL progression and may identify new therapeutic targets. Note: This abstract was not presented at the meeting. Citation Format: Subhadip Das, RF Dielschneider, Elizabeth S. Henson, Spencer B. Gibson. ZAP70 alters metabolism in chronic lymphocytic leukemic cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5423. doi:10.1158/1538-7445.AM2017-5423</jats:p

Survey of ex vivo drug combination effects in chronic lymphocytic leukemia reveals synergistic drug effects and genetic dependencies

Drug combinations that target critical pathways are a mainstay of cancer care. To improve current approaches to combination treatment of chronic lymphocytic leukemia (CLL) and gain insights into the underlying biology, we studied the effect of 352 drug combination pairs in multiple concentrations by analysing ex vivo drug response of 52 primary CLL samples, which were characterized by "omics" profiling. Known synergistic interactions were confirmed for B-cell receptor (BCR) inhibitors with Bcl-2 inhibitors and with chemotherapeutic drugs, suggesting that this approach can identify clinically useful combinations. Moreover, we uncovered synergistic interactions between BCR inhibitors and afatinib, which we attribute to BCR activation by afatinib through BLK upstream of BTK and PI3K. Combinations of multiple inhibitors of BCR components (e.g., BTK, PI3K, SYK) had effects similar to the single agents. While PI3K and BTK inhibitors produced overall similar effects in combinations with other drugs, we uncovered a larger response heterogeneity of combinations including PI3K inhibitors, predominantly in CLL with mutated IGHV, which we attribute to the target's position within the BCR-signaling pathway. Taken together, our study shows that drug combination effects can be effectively queried in primary cancer cells, which could aid discovery, triage and clinical development of drug combinations