Herein is described a method of detecting apoptotic cells and monitoring apoptosis in a caspase-independent manner. Cells are treated with a caspase inhibitor, and then a marker of apoptosis, such as a caspase-independent signaling protein, is detected for an extended period of time. When cells were suspended in the process of apoptosis and scored for apoptotic cells, the method was shown to be more sensitive than conventional assays. When apoptosis was induced by certain inhibitors, the method is capable of measuring cumulative background levels of apoptosis over a multi-day interval.
STATEMENT OF GOVERNMENTAL SUPPORT
 This invention was made during work supported by National Institutes of Health fellowship (AG24015) and grant (AG17242), Department of Defense grant DAMD17-02-1-0443, and the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The government has certain rights in this invention.