Background: Hepatocellular carcinoma (HCC) remains a major clinical challenge due to its pronounced molecular heterogeneity and frequent resistance to conventional therapies. A key driver of therapeutic failure is the overexpression of the anti-apoptotic proteins myeloid cell leukemia-1 (Mcl-1) and B-cell lymphoma-extra large (Bcl-XL), which collectively maintain mitochondrial integrity and promote tumor cell survival. Methods: In this study, we evaluated a rational combination strategy targeting these complementary survival pathways using the histone deacetylase inhibitor panobinostat and the DNA-damaging agent bleomycin in HepG2 cells, a p53-functional HCC cell model. Results: In HepG2 cells, each agent alone produced only limited cytotoxicity, whereas their combination resulted in a marked and synergistic induction of apoptosis. This was shown by increased Annexin V positivity, mitochondrial outer membrane permeabilization (MOMP), and activation of caspases-8, -9, and -3 as well as cleavage of poly(ADP-ribose) polymerase (PARP). Mechanistically, panobinostat reduced Bcl-XL expression and primed mitochondria for apoptosis but simultaneously triggered compensatory upregulation of Mcl-1, representing an adaptive resistance response within this experimental system. Bleomycin effectively counteracted this escape mechanism by suppressing Mcl-1 induction, thereby lowering the apoptotic threshold and enabling mitochondrial permeabilization. In parallel, combined treatment potentiated caspase-8 cleavage, suggesting an additional caspase-8-associated apoptotic signal that amplified caspase-3/PARP execution. Pharmacological inhibition with zVAD-FMK confirmed that the observed cell death was predominantly caspase-dependent, supporting a coordinated engagement of both intrinsic and extrinsic apoptotic pathways. In summary, the combination of panobinostat and bleomycin overcomes anti-apoptotic defenses in HepG2 cells through synergistic and coordinated disruption of mitochondrial survival checkpoints and dual apoptosis pathway activation. Conclusions: By blocking a compensatory Mcl-1 escape response while simultaneously engaging extrinsic apoptosis signaling, this strategy produces potent synergistic cell death in this defined p53-functional HCC model and represents a promising mechanistic proof of concept that warrants further validation in additional molecularly diverse HCC models before broader translational conclusions can be drawn.

Colorectal cancer (CRC) is a leading cause of cancer death, with resistance and apoptosis evasion—often via Bcl-2—representing major challenges. The redox-modulating drug dimethyl fumarate (DMF) has demonstrated efficacy in hematologic malignancies; however, its potential in solid tumors remains unclear. Here, we show that DMF, especially in combination with the Bcl-2 inhibitor venetoclax (ABT-199), induces apoptosis in HCT-116 CRC cells. DMF impairs mitochondrial respiration, causing membrane hyperpolarization, ATP depletion, autophagy, and cell cycle arrest. Combined treatment increases metabolic stress, reduces proliferation, and induces sustained G2 arrest with downregulation of cyclins and CDKs. These findings highlight a combined effect targeting redox balance and apoptosis in CRC. Given their clinical availability, DMF and ABT-199 represent a promising combination for further preclinical evaluation.