Evidence of an immunologic mechanism behind the therapeutical effects of arsenic trioxide (As₂O₃) on myeloma cells

Exposure of RPMI 8226, Karpas 707 and U266 human myeloma-like lines to low doses of As₂O₃ was followed by a marked increase in lymphokine activated killers (LAK)-mediated killing and up- modulation of CD38 and CD54, two molecules involved in cell-cell interactions. Moreover, simultaneous exposure of effectors and targets to As₂O₃ yielded the most effective condition for lysis. The expression of CD31 (CD38 ligand) and CD11a (CD54 ligand) was also up-regulated by LAK, suggesting that increased adhesion was responsible for the improved killing. Similar results were obtained using freshly isolated myeloma cells. These findings indicate that As₂O₃ may be useful to boost the immune system against myelomas.