Marine-derived ophiobolin MHO7 targets voltage-dependent anion channel 2 and promotes its degradation in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) lacks effective molecularly targeted therapies, highlighting an urgent need to identify druggable vulnerabilities. Although the marine-derived ophiobolin MHO7 exhibits potent antitumor activity, its cellular targets remain elusive. By integrating activity-based protein profiling (ABPP) with clinical relevance analysis, we identified voltage-dependent anion channel 2 (VDAC2) as a primary MHO7-interacting protein in TNBC cells. Probe pull-down, cellular thermal shift assays, microscale thermophoresis and colocalization analysis provided convergent evidence of MHO7-VDAC2 association; the lysate-based assay yielded an apparent dissociation constant, whereas mutagenesis identified Cys103, Cys210 and Cys227 as mutation-sensitive determinants of the detectable lysate-based response. MHO7 preferentially reduced VDAC2 abundance elative to VDAC1 and VDAC3 and accelerated its turnover. Pharmacological inhibition of autophagy-lysosomal function and depletion of autophagy-related protein 7 (ATG7) or sequestosome 1 (p62 /SQSTM1) attenuated VDAC2 loss, implicating contributions from the core autophagy machinery and p62. Genetic depletion and re-expression experiments revealed that VDAC2 modulates mitochondria-endoplasmic reticulum contact (MERC) architecture, longer-time mitochondrial Ca2+ homeostasis, mitochondrial reactive oxygen species (mitoROS), proteasome activity and antitumor responses. Several MHO7 responses persisted after partial VDAC2 depletion, indicating that VDAC2 is an important contributor rather than the sole mediator of MHO7 pharmacology. Collectively, these findings identify VDAC2 as a pharmacologically relevant target of MHO7 and show that MHO7 promotes its autophagy-lysosomal turnover, providing a protein-level mechanism that complements previously described pathway-level actions of MHO7, thereby extending mechanism understanding of marine-derived ophiobolins in cancer therapy.