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 effecters 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 As(2)O2(3) may be useful to boost the immune system against myelomas. (C) 2001 Elsevier Science Ltd. All rights reserved.