Enhanced cross‐priming of naive CD8+ T cells by dendritic cells treated by the IMiDs® immunomodulatory compounds lenalidomide and pomalidomide

The IMiDs^® immunomodulatory compounds lenalidomide and pomalidomide are agents with anti‐inflammatory, immunomodulatory and anti‐cancer activity. An excellent success rate has been shown for multiple myeloma in phase I/II clinical trials leading to Food and Drug Administration approval of lenalidomide. One mechanism by which these drugs could enhance anti‐tumour immunity may be through enhanced dendritic cell (DC) function. Thalidomide, a compound structurally related to lenalidomide and pomalidomide, is known to enhance DC function, and we have investigated whether its analogues, pomalidomide and lenalidomide, also have functional effects on DCs. We used mouse bone marrow‐derived DCs treated with 5 or 10 μm pomalidomide, or lenalidomide from day 1 of culture. Treatment with IMiD^® immunomodulatory compounds increased expression of Class I (H2‐Kb), CD86, and pomalidomide also increased Class II (I‐Ab) expression in bone marrow‐derived DCs, as measured by flow cytometry. Fluorescent bead uptake was increased by up to 45% when DCs were treated with 5 or 10 μm pomalidomide or lenalidomide compared with non‐treated DCs. Antigen presentation assays using DCs primed with ovalbumin, and syngeneic T cells from transgenic OTI and OTII mice (containing MHC restricted, ovalbumin‐specific, T cells) showed that both pomalidomide and lenalidomide effectively increased CD8⁺ T‐cell cross‐priming (by up to 47%) and that pomalidomide alone was effective in increasing CD4⁺ T‐cell priming (by 30%). Our observations suggest that pomalidomide and lenalidomide enhance tumour antigen uptake by DCs with an increased efficacy of antigen presentation, indicating a possible use of these drugs in DC vaccine therapies.