Cytotoxic factors having use in modulating cell death, and their use in methods of treating necrosis or apoptosis-related conditions are disclosed. The invention also relates to methods for identifying active agents useful in treating conditions related to cell death. The present inventors have found that different pathogens produce different cytotoxic factor(s) having anticancer activity. The substantially pure cytotoxic factors can be used in a method of treating an infectious disease or a cancer.