Streptomycin targets tumor-initiating cells by disrupting oxidative phosphorylation

Tumor initiating cells (TICs) are the roots of current shortcomings in advanced and metastatic cancer treatment. Endowed with self-renewal and multi-lineage differentiation capacity, TICs can disseminate and seed metastasis in distant organ. Our work identified streptomycin (SM), a potent bactericidal antibiotic, as a molecule capable of specifically targeting non-adherent TIC from colon and breast cancer cell lines. SM induces iron-dependent, reactive oxygen species (ROS)-mediated cell death, which is mechanistically distinct from RSL3-induced ferroptosis. SM-induced cell death is associated with profound alterations in mitochondrial morphology. This effect results from COX1 inhibition, which disrupts the regulation of the cytochrome c oxidase complex and triggers mitochondrial ROS production. SM's aldehyde group is essential, as its reduction into dihydrostreptomycin (DSM) abolishes its activity. These findings reveal a mechanism of action for streptomycin, shedding light on TIC metabolism and resistance, with potential implications for advanced cancer treatment.