Phenotypic and Functional Effects of Perifosine on Dendritic Cells.

Perifosine is a synthetic novel alkylphospholipid, a new class of antitumor agent which targets cell membranes and inhibits Akt activation. Perifosine inhibits multiple myeloma (MM) cell growth in vitro and in vivo mouse model. Currently perifosine is under the evaluation of phase II clinical trail in MM. Although perifosine has shown significant direct antitumor effects, its effect on immune system has not yet been clarified. The objective of this study is to evaluate the effects of perifosine on the activity of antigen presenting cells (APCs). Monocyte-derived dendritic cells (DCs) from normal human donors were used as the APCs, and mature DCs were obtained by the treatment of TNF-α and IL-1β. Perifosine was used at the concentrations of 2.5 uM, 5 uM and 10 uM for the treatment with DCs. We first evaluated the effect of perifosine on the survival of DCs. We observed that the perifosine treatment up to 48 hours had no effect on viability (>90%) of DCs, assessed by annexin V and PI staining. Alteration of phenotype by perifosine on DCs was further examined by flow cytometry. Our results demonstrated that with dose-dependent manner, perifosine led to a significant down-regulation of surface antigens on immature DCs at 24 and 48 hours, which associated to costimulation (CD40, CD80 and CD86), antigen presentation (HLA-ABC, HLA-DPQR) and maturation (CD83). However, we did not observed significant effect of perifosine on above surface markers on mature DCs. Since DCs play a crucial role on the regulation of Th1/Th2 immune responses by the production of IL-12, we next evaluated IL-12 secretion by DCs with and without perifosine treatment. Importantly, treatment with perifosine significantly decreased LPS-induced-IL-12 production, compared to untreated DCs (untrt vs. trt = 192.29 vs. 166.23 pg/ml (2.5uM), 111.19 pg/ml (5uM) and 44.886 pg/ml (10uM)) at 24 hours. To assess the effect of perifosine on DCs function on the regulation of T cell responses, we stimulated allogenic T cells with mature DCs with or without the pre-treatment of perifosine. The proliferation assay by ³H-TdR incorporation and IFN-γ production by ELISA indicated perifosine-treated DCs had no significant effect on the regulation of T cells function. Taken together, these results showed that DCs function are influenced by the treatment of perifosine. Our pre-clinical data therefore indicates the need to monitor immune functions in patients under the Akt inhibitor treatment.