Evasion of cell death despite mitochondrial outer membrane permeabilization: an oncogenic outcome of apoptosis.
Apoptosis has traditionally been viewed as an irreversible, tumor-suppressive process, with mitochondrial outer membrane permeabilization (MOMP) representing the decisive "point of no return" that irrevocably commits cells to death. Classical models described MOMP as a rapid, synchronous, all-or-none event leading to caspase activation and cellular demise. However, accumulating evidence now challenges this binary view, revealing that both MOMP and downstream caspase activity are threshold-dependent processes that can produce diverse non-lethal outcomes. Under specific conditions, cells can survive or recover from MOMP and downstream apoptotic signaling, fundamentally reshaping our understanding of cell fate decisions. Failed apoptosis and anastasis lie at the center of this paradigm shift, revealing unexpected plasticity in apoptotic outcomes. Failed apoptosis occurs when limited MOMP triggers sublethal yet sustained caspase activity, leading to DNA damage, chromosomal instability, and prolonged cellular reprogramming, thereby accelerating oncogenesis and tumor progression. In contrast, anastasis describes a remarkable recovery process in which cells rebound from late-stage apoptosis after the removal of apoptotic stimuli. Recovered cells exhibit acquired enhanced stress tolerance and oncogenic traits, raising concern about their role in therapy failure, cancer progression, and relapse. This review discusses the molecular mechanisms governing MOMP initiation and subsequent apoptotic signaling, with particular emphasis on new insights into the reversibility of apoptosis. It highlights the concepts of failed apoptosis and anastasis as adaptive responses that influence cell fate, integrating current research, experimental tools and challenges, and their physiological relevance and clinical implications. By describing these survival pathways, the review aims to enhance our understanding of the reversibility of apoptosis and emphasize its relevance to cancer progression, metastasis, and resistance to therapy. These insights may help develop more effective cancer treatments and improve patient outcomes.