Novel Tetrahydroxanthylium-Based Ligands Targeting Mitochondrial DNA G‑Quadruplex Structures for Concurrent Induction of Apoptosis and Inhibition of Autophagy in Liver Cancer

Liver cancer, a leading cause of cancer-related mortality, is characterized by intrinsic and acquired therapeutic resistance linked to dysregulated programmed cell death pathways. Apoptosis evasion, driven by p53 mutations or antiapoptotic protein overexpression, and autophagy upregulation, which sustains cancer cell survival under stress, are critical barriers to effective treatment. This study introduced XAN-5, a novel mitochondrial DNA G-quadruplex (mtG4)-targeting tetrahydroxanthylium ligand that can simultaneously induce apoptosis and inhibit autophagy. Mechanistically, XAN-5 bound mtG4s, triggering mitochondrial dysfunction, reactive oxygen species overproduction, and caspase-dependent apoptosis. Concurrently, XAN-5 disrupted autophagic flux, evidenced by reduced LC3B–II conversion and p62 accumulation. In a mouse liver cancer model, XAN-5 inhibited tumor growth while enhancing tumor-infiltrating CD4+ and CD8+ T cells. These findings highlighted the unique capacity of XAN-5 to target two resistance mechanisms, offering a paradigm shift in liver cancer therapy.