Eflornithine and venetoclax combination therapy: Targeting senescence to induce apoptosis in neuroblastoma

High-risk neuroblastoma (HRNB) is difficult to cure due to relapses and limited therapeutic durability. Eflornithine, an inhibitor of ornithine decarboxylase, inhibits polyamine synthesis and is clinically effective in preventing HRNB recurrence. Eflornithine induces a stable senescent phenotype that suppresses proliferation. Eliminating these senescent HRNB cells is of therapeutic interest. Venetoclax, a selective Bcl-2 inhibitor approved for hematologic malignancies, has been identified as a potent senolytic that triggers apoptosis in senescent cells. We therefore hypothesized that venetoclax may induce apoptosis in eflornithine-induced senescent HRNB cells, thereby overcoming tumor persistence. HRNB cells (BE2c cell line) were sequentially treated with eflornithine for 4 days to induce senescence followed by the addition of venetoclax for 18 hours to induce apoptosis. Senescence was assessed by beta-galactosidase staining and p21, p16, and p27 protein expression. Apoptosis and survival markers were analyzed by Western blotting to detect Mcl-1, BAG3, GLS1, cleaved Caspase-3, and cleaved PARP. Cytokine levels were measured by qPCR. Treatment of NB cells with eflornithine induced a robust senescence response, increasing beta-galactosidase activity and expression of p21, p16, and p27 in a time-dependent manner. Venetoclax alone failed to induce apoptosis and instead upregulated the pro-survival protein Mcl-1 (5.5-fold), whereas pre-treatment with eflornithine both reduced basal Mcl-1 (0.5-fold) and prevented venetoclax-induced Mcl-1 elevation (0.03-fold in the combination). Consistent with eflornithine's effect on polyamine-dependent translation, BAG3, a chaperone that stabilizes Mcl-1, was downregulated, providing a mechanistic basis for Mcl-1 destabilization and enhanced venetoclax sensitivity. Eflornithine also decreased expression of GLS1, an enzyme linked to mitochondrial fitness and anti-apoptotic signaling. Sequential treatment of eflornithine followed by venetoclax triggered strong activation of apoptotic markers, increasing cleaved Caspase-3 (1.4-fold) and cleaved PARP (9-fold) compared to vehicle, confirming a synergistic shift from senescence to apoptosis. Cytokine analysis revealed selective remodeling of the SASP, with an increase in IL-1beta (33-fold) and IL-6 (6-fold), and IFN-gamma (>50-fold). Together, these findings establish a novel mechanistically informed combinatorial strategy in which polyamine depletion converts senescent tumor cells into apoptotically vulnerable targets, offering a promising therapeutic avenue for HRNB. Ongoing in vivo studies will determine the translational potential of eflornithine + venetoclax as a rational senescence-targeting regimen.