Assessing apoptosis: a critical survey

Much progress has been made in the understanding of the process of apoptosis and there is a burgeoning literature pointing to it being a key phenomenon in tissue homeostasis. Moreover it is clear that derangements of the apoptotic cascade and its regulation can occur in a variety of disease states including in cancer. Many methods exist for the demonstration of apoptosis but some are not quantifiable. Others, such as enumeration of apoptotic bodies or end-labelling techniques, lend themselves to quantification. However, poor methods of quantification are sometimes employed. In this review, the methodological problems that can affect the assessment of apoptosis are discussed and suggestions made for more rigorous approaches.