Schematic representation of apoptotic pathways triggered by 2ME2, 4HT and RU. Apoptosis induced by 2ME2 (in black) is mediated by the release of apoptogenic proteins cytochrome c and Smac from the mitochondria to the cytosol, followed by the activation of caspase-9, -8 and -3 . The mitochondria intrinsic death pathway is also recruited by 4HT (in red) and RU (in blue): following the cytosolic release of cytochrome c, the caspase-9 is activated then the caspase-3 [11, 16] (Gauduchon et al, submitted). 4HT and RU treatments also lead to the activation of caspase-8 but we have not yet determined the mechanism of caspase-8 activation. However, we know that the three death receptors selectively expressed by MM cells, Fas, DR4 and DR5  are not involved (data not shown).