Monopolar perinuclear mitochondrial clustering is a recurrent cancer-associated response to H2O2-dominant oxidative stress

Perinuclear mitochondrial clustering (PMC) has been described as a cytoprotective mitochondrial response in cancer cells, characterized by the symmetric or circumferential distribution of fragmented mitochondria around the nucleus. In contrast, a distinct mitochondrial spatial arrangement associated with cancer-cell injury remains undefined. Here, we characterized monopolar perinuclear mitochondrial clustering (MPMC), a distinct mitochondrial remodeling phenotype in which fragmented mitochondria accumulate asymmetrically along one side of the nuclear periphery. MPMC emerged after exposure to H₂O₂-dominant oxidative stress inducers, such as plasma- or ozone-treated media. It developed progressively with increasing stress intensity and exposure time and appeared before plasma membrane rupture. Less severe stress predominantly increased PMC, whereas more severe stress promoted pronounced MPMC formation. Transmission electron microscopy confirmed asymmetric perinuclear accumulation of fragmented mitochondria with disruption of inner mitochondrial membranes and cristae. MPMC was observed across diverse human and canine cancer models susceptible to stress-induced cell injury, whereas tolerant nonmalignant cells retained the PMC phenotype without progression to MPMC under comparable conditions. Catalase suppressed MPMC formation, whereas inhibiting glutathione synthesis enhanced it; these changes paralleled corresponding decreases or increases in cellular injury. Collectively, these findings identify MPMC as a distinct cancer-associated mitochondrial remodeling phenotype associated with cellular injury under H₂O₂-dominant oxidative stress.