Treatment of P388D1, a macrophage-like cell line, with staurosporine triggered apoptosis through the activation of caspase-9 and caspase-3. Unexpected effects of staurosporine on the induction of apoptosis were the activation of caspase-8, and an increase of the levels of TNF-alpha. The increased TNF-alpha levels led to activation of caspase-8 by an autocrine effect via the TNF receptor expressed by the P388D1 macrophages. In contrast, P388D1 macrophages that either had been exposed to UV light or treated with dexamethasone did not undergo apoptosis.