In Vitro Cell Death Determination for Drug Discovery: A Landscape Review of Real Issues

Méry, Benoite; Guy, Jean-Baptiste; Vallard, Alexis; Espenel, Sophie; Ardail, Dominique; Rodriguez-Lafrasse, Claire; Rancoule, Chloé; Magné, Nicolas

Autophagic cell death involves the formation of double membrane which contains vacuoles, and this sequestrated cytoplasm is subsequently digested through the fusion with lysosome vacuoles. However, the specific role of autophagy in the execution of cell death remains controversial and is not fully elucidated yet. Autophagy may constitute an epiphenomenon of cell death that could be analyzed as an ultimate but unsuccessful attempt by cells to cope with stress and re-establish homeostasis. 14 Moreover, concerning recent neologisms introduced to define other putative cell death modalities, only a few of them truly reflect cell death pathways that are biochemically and morphologically distinct from apoptosis and necrosis. Indeed, terms such as mitotic catastrophe, anoikis, and pyroptosis most often refer to cell death mechanisms that are executed by the molecular machinery of apoptosis and necrosis. 15, 16 In contrast, ferroptosis, an iron-dependent form of cell death, is morphologically, biochemically, and genetically different from apoptosis, necrosis, and autophagy. This particular form of nonapoptotic cell death can occur in specific pathologic conditions after its activation by an oncogenic RAS-selective lethal small molecule (erastin) and is iron dependent. 17 Finally, even if apoptosis, autophagy, and necrosis display distinct morphologic characteristics and physiologic processes, they do share significant commonalities and more particularly coordinate with each other. As a matter of fact, under some conditions, apoptosis and autophagy can display synergetic effects, whereas autophagy can be activated when apoptosis is suppressed. 18 Consequently, it seems that the existence of several pathways for cell death and the complex relationship between these modalities require the use of different protocols to measure and identify the type of cell death, for quantitative and qualitative analysis. Moving away from a monolithic point of view is necessary as the interrelation between cell death processes appears to be more complex than initially anticipated.