DACH1 DOWNREGULATION DELINEATE A LYMPHOID PRIMED PROGENITOR (LPP) POPULATION WITHIN THE MPP4 CLUSTER

Dysregulation of cancer cell bioenergetics is one of the hallmarks of cancer.The Warburg effect is one such documented change.However, glucose metabolism is not universally increased in cancer cells.Uptake of 18F-FDG in chronic lymphocytic leukemia (CLL) fails as a marker of proliferation and whilst the underlying reason is poorly understood it suggests that CLL cells utilize energy sources other than glucose to proliferate.Using genetic, proteomic and lipidomic analyses, complemented with microscopy and nutrient uptake assays the preferred metabolic pathways of CLL cells have been identified.We measured the uptake of fluorescently labelled short, medium and long-chain fatty acids (LCFA) and the glucose analog 2-NBDG by flow cytometry and confocal microscopy.Three CLL lines (MEC1, MEC2, OSU-CLL) prefer LCFA, over short and medium chain and show a low uptake of 2-NBDG.We have also confirmed these findings in primary CLL samples.Using qPCR and western blot analysis we have identified varying levels of LCFA uptake receptors.We found an up-regulation of proteins involved in lipogenesis in quiescent peripheral CLL cells, and an increase in b-oxidation proteins in the proliferative compartment of the lymph node.Together with our morphological examination using electron and confocal microscopy we suggest that peripheral CLL cells scavenge lipids, which are stored in lipid droplets and protected from degradation by a high expression of PLIN proteins.These cells circulate back to the proliferation centres, the lipid droplets are degraded, likely by lipophagy which frees fatty acids for b-oxidation.Our results begin to unravel CLL bioenergetics and dysregulation of cellular metabolism that occurs in this disease.We are now investigating whether the manipulation of these pathways, particularly lipophagy, may represent a novel therapeutic approach in CLL.