In vitro Immune Signaling under Metabolic Stress: Serum Starvation and Glutaminase Inhibitor CB-839 in MV4-11 and DU145 Cancer Cells

Metabolic stress responses in cancer cells are commonly examined through isolated pathway analysis, but the interconnectivity between metabolic stressors and immune evasion mechanisms such as Programmed Death-Ligand 1 (PD-L1) expression remains poorly understood. This study investigated how serum starvation and glutaminase inhibition with CB-839 reshapes cell viability, cell cycle, and immune-related responses in MV4-11 acute myeloid leukemia and DU145 prostate cancer cells. Serum starvation induced rapid, uniform collapse in both lines, including viability losses exceeding 60%, G1 arrest, and the downregulation of immune evasion genes, demonstrating acute stress that obscures metabolic and immune relationships. Glutaminase inhibition revealed distinct responses based on cell type. MV4-11 showed initial viability loss at 48 hours that stabilized by 72 hours, as well as recovery of GLS1 and PD-L1 expression, suggesting metabolic reprogramming from the TCA cycle toward glycolysis. DU145 exhibited early tolerance followed by collapse at 72 hours with G1 arrest, and declining immune evasion gene expression, indicating failed adaptation. Under serum starvation, DU145 upregulated GLS1, shifting toward the TCA cycle, but when CB-839 blocked this pathway, cells failed to metabolically reprogram to glycolysis. MYC directly regulated PD-L1 in MV4-11 across all conditions, while in DU145 PD-L1 expression remained similar to control levels despite MYC decreases, indicating alternative PD-L1 expression pathways in DU145. These findings demonstrate that prolonged glutaminase inhibition differentially impacts cell types based on metabolic flexibility. Future work will target the KMT2A-AFF1 fusion via siRNA, restoring RUNX1 against premature CDK1 degradation to determine whether plasticity and immune evasion are fusion-dependent.