Sequential treatment by ionizing radiation and sodium arsenite dramatically accelerates TRAIL-mediated apoptosis of human melanoma cells

Abstract

Melanoma is the most lethal form of skin cancer. There is a lack of effective treatments for individuals with advanced disease. Many melanomas exhibit high levels of radioresistance. The direct consequence of γ-irradiation for most melanoma cells is growth arrest at the G 2-M phase of cell cycle. However,radiation-indu ced signaling pathways may affect numerous additional targets in cancer cells. We show in the present study that γ-irradiation, as well as α-particle exposure, dramatically increases the susceptibility of melanoma cells to recombinant tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis via up-regulation of surface TRAIL-receptor 1/receptor 2 (DR4/ DR5) levels and to Fas ligand-mediated apoptosis via upregulation of surface Fas levels. Additionally,incr eased dynamin-2 expression after irradiation is critically important in the translocation of death receptor to the cell surface. Moreover, sodium arsenite treatment may up-regulate expression of endogenous TRAIL and induces its translocation to cell surface and further down-regulates cFLIP levels in melanoma cells. We have evaluated the effects of sequential γ-irradiation and arsenite treatment of melanoma cells for the induction of death signaling. Such treatment results in an efficient TRAIL-mediated apoptosis via a paracrine mechanism. These data highlight the efficacy of combined modality treatment involving radiation and arsenite in clinical management of this often fatal form of skin cancer. ©2007 American Association for Cancer Research.