Distinct NF-kB Regulation Favors a Synergic Action of Pevonedistat and Laduviglusib in B-Chronic Lymphocytic Leukemia Cells Ex Vivo

<b>Background/Objectives:</b> Chronic lymphocytic leukemia (CLL) remains an incurable B-cell malignancy. B-CLL cells exhibit an extended lifespan in part due to the activation of survival pathways such as NF-kB. A crosstalk between NF-kB and GSK-3β pathways has been reported. NF-kB has also been identified as a primary target of the NEDD8-activating enzyme inhibitor MLN4924. Our objective was to investigate potential synergies of MLN4924 with other NF-kB-targeting agents for the treatment of CLL and elucidate the mechanisms of action underlying this pathway regulation. <b>Methods:</b> To assess the cytotoxic efficacy of the combined ex vivo treatment with CHIR-99021 and MLN4924, we employed 7-AAD staining and XTT viability assays on primary samples from CLL patients. Subsequently, we conducted various analyses to identify the molecular mechanisms underlying the cytotoxic effects of this combination. <b>Results:</b> We discovered a discrepancy between the mRNA and protein levels of IkBɑ and provided evidence of translational control over its expression. This observation may explain why, unlike other cell types, B-CLL cells did not activate NF-kB signaling following inhibition of GSK-3ß. Furthermore, we describe a synergistic effect between a specific GSK-3ß inhibitor, CHIR-99021/Laduviglusib, and the NEDD8-activating enzyme inhibitor MLN4924/Pevonedistat, at doses that only slightly affect healthy B cell viability ex vivo. We investigated the molecular basis of this co-induction of cell death by analyzing the alterations in apoptosis-related gene expression. We found that the combinational treatment enhances a reduction in BCL2 mRNA expression levels, providing an alternative approach for BCL-2 inhibition in CLL that could have therapeutic implications for the treatment of refractory CLL cases. <b>Conclusions:</b> our findings revealed a unique interaction between GSK-3ß and NF-kB pathways in CLL and their regulation of BCL2 expression.