Functional cooperation between the B-cell receptor and NOTCH1 in regulating metabolic reprogramming in chronic...

Mutations in NOTCH1, which occur in ~10% of Chronic Lymphocytic Leukemia (CLL) patients at diagnosis, are typically associated with unmutated (UM) B-cell receptor (BCR) subsets and define patients with earlier treatment need. Using primary CLL cells classified as NOTCH1 wild-type (CLL/N^WT) or mutated (CLL/N^M), both with UM-BCR, we show that BCR stimulation activates the NOTCH1 pathway, upregulating metabolic programs and mitochondrial biogenesis, selectively in CLL/N^M. These cells display enhanced basal respiration and glycolysis, driven by higher mitochondrial mass, and further increase metabolic activity upon BCR triggering. To directly implicate NOTCH1 mutations, we engineered an MEC-1 model to generate wild-type (MEC-1/N^WT) or mutated (MEC-1/N^M) clones in a UM-BCR background. Here, NOTCH1 hyperactivation promoted mitochondrial metabolism through TFAM-dependent transcriptional control. Gene expression profiling, metabolic assays, and stable isotope tracing confirmed that MEC-1/N^M cells rely on oxidative metabolism, with increased glutamine dependency and strengthened anabolic pathways, leading to augmented proliferation compared to MEC-1/N^WT. Importantly, CLL/N^M cells exhibit a marked vulnerability to glutamine deprivation. Combined inhibition of glutamine utilization and BCL2 triggered rapid apoptosis, providing a rationale for tailored therapeutic strategies in NOTCH1-mutated CLL. Representation of the molecular mechanism behind the metabolic reprogramming. BCR and NOTCH1 drive a dual metabolic reprogramming of glucose and glutamine pathways. In NOTCH1-mutated cells, both glucose and glutamine uptake are positively increased and even more upon BCR stimulation. Glucose is preferentially used to fuel the pentose phosphate pathway, and glutamine the TCA cycle. Concurrently, NICD accumulation, driven by BCR signaling, promotes TFAM expression and mitochondrial biogenesis. The resulting increase in mitochondrial mass underpins enhanced ATP production, oxygen consumption, and ROS generation, establishing a glutamine-dependent mitochondrial phenotype. This dependency sensitizes NOTCH1-mutated cells to glutamine blockade, which selectively induces apoptosis, further enhanced by combination with BCL-2 inhibition.