Gboxin

Non-small cell lung cancer (NSCLC) ranks among the most prevalent malignancies globally. Gboxin, a novel inhibitor of mitochondrial complex V that exerts unique anti-tumor effects via oxidative phosphorylation inhibition, but shows no efficacy against NSCLC in vivo. Through chemical structure optimization, we designed and synthesized Gboxin analog Y9, which demonstrates significantly enhanced potency over its predecessor. Specifically, Y9 inhibited NSCLC significantly more strongly than Gboxin and possessed the ability to inhibit cell cycle progression and induce oxidative stress similar to Gboxin. Further investigation revealed that unlike Gboxin, Y9 selectively acidifies lysosomes and induces lysosomal dysfunction. This leads to hyperactive autophagy with impaired substrate clearance, and ultimately resulting in apoptosis. Animal studies confirmed the efficacy of Y9 in suppressing tumor growth in a xenograft mouse model. Collectively, Y9 is a distinctive Gboxin analog that outperforms its prototype by inducing lysosomal dysfunction and apoptosis, and has the potential to be developed as a novel anti-NSCLC lead compound.

Lacking a clear understanding of the molecular mechanism determining cancer cell sensitivity to oxidative phosphorylation (OXPHOS) inhibition limits the development of OXPHOS‐targeting cancer treatment. Here, cancer cell lines sensitive or resistant to OXPHOS inhibition are identified by screening. OXPHOS inhibition‐sensitive cancer cells possess increased OXPHOS activity and silenced nicotinamide N‐methyltransferase (NNMT) expression. NNMT expression negatively correlates with OXPHOS inhibition sensitivity and functionally downregulates the intracellular levels of S‐adenosyl methionine (SAM). Expression of DNA methyltransferase 1 (DNMT1), a SAM consumer, positively correlates with OXPHOS inhibition sensitivity. NNMT overexpression and DNMT1 inhibition render OXPHOS inhibition‐sensitive cancer cells resistant. Importantly, treatments of OXPHOS inhibitors (Gboxin and Berberine) hamper the growth of mouse tumor xenografts by OXPHOS inhibition sensitive but not resistant cancer cells. What's more, the retrospective study of 62 tumor samples from a clinical trial demonstrates that administration of Berberine reduces the tumor recurrence rate of NNMTlow/DNMT1high but not NNMThigh/DNMT1low colorectal adenomas (CRAs). These results thus reveal a critical role of the NNMT‐DNMT1 axis in determining cancer cell reliance on mitochondrial OXPHOS and suggest that NNMT and DNMT1 are faithful biomarkers for OXPHOS‐targeting cancer therapies.