Schematic representation of the molecular mechanism of violacein-induced HL60 cell death. Data presented in this report revealed that violacein induces apoptosis in HL60 cells through activation of the TNF signaling cascade as demonstrated by up-regulation of TRAF2 and its coimmunoprecipitation with TNFR1. Trimeric TNF binds to and trimerizes TNFR1 molecules, leading to a recruitment of TRADD, which in turn can recruit TRAF2, receptor-interacting protein (RIP), and Fas-associated death domain (FADD). This event is involved in NF-κB, MAPK, and caspase 8 induction. p38 MAPK and NF-κB are translocated to the nucleus and activate some gene transcription (eg, TNF-α). Newly produced TNF-α will amplify the effect of violacein in neighboring cells. Active caspase 8 initiates the apoptotic cascade as demonstrated by activation of caspase 3 and PARP cleavage. TNFR1 can activate 2 signaling pathways, cell survival (through activation of NF-κB), or apoptosis. HL60 cells treated with violacein for 24 hours presented dominance of the apoptotic signaling cascade (which was also demonstrated by down-regulation of IAP1 and PARP cleavage). All proteins investigated in this work have been underlined.