Abstract
Background: The myelodysplastic syndromes (MDS) comprise a spectrum of stem cell malignancies with natural histories that vary from indolent mild cytopenias to rapid transformation to acute leukemia. MDS patients have impaired T cell antigen-induced proliferation and reduced T helper-1 (Th-1) cytokine production. Lenalidomide, an immuno-modulatory drug structurally-related to thalidomide, is FDA-approved for the treatment of MDS with chromosome 5q deletion; however, its mechanism of action is not fully characterized. We hypothesize that immune modulation by lenalidomide will be an effective adjunct to vaccine therapy for patients with MDS.
Methods: The immunoregulatory effects of lenalidomide were investigated both in vitro and in vivo. Peripheral blood mononuclear cells (PBMCs) from MDS patients and normal controls were stimulated with anti-CD3 cross-linking, allogeneic dendritic cells (allo-DCs), autologous dendritic cells (auto-DCs), and patient-derived autologous bone marrow mononuclear cells (BM-MNC) as antigen sources in the presence of DMSO (vehicle control) and lenalidomide [0.625 μM to 40 μM]. Proliferation of specific CD4+ and CD8+ T cell populations was assessed by Brdu incorporation and intracellular cytokine production by flow cytometry. Preliminary studies were performed to examine the combined effects of the GMCSF/K562 “bystander” vaccine (gift of Dr. I. Borrello, Johns Hopkins University) and lenalidomide on antigen-induced T cell proliferation in PBMC from both normal donors and MDS patients.
Results: Lenalidomide augmented a Th-1-biased cytokine (IFN-γ, TNF-α and IL-2) response from normal donors (n=5) and MDS patients (n=5). The Th-1-biased increase in cytokine production accompanied erythroid response in MDS patients treated with 10 mg of lenalidomide for 16 weeks (n=4 responders and 3 non-responders) (List et al, NEJM2005;351:549). Augmentation of antigen-dependent proliferation accompanied cytokine responses both in vitro and in vivo. Next, we examined the effects of lenalidomide on in vitro response to autologous and allogeneic antigens. We found that pre-treatment T cell proliferation in response to auto-DC priming was not distinguishable from background. However, proliferation in response to auto-BM-MNCs used as a source of autologous tumor antigens was significantly increased by lenalidomide in CD3+, CD4+, and CD8+ T cell populations (P=0.002, 0.04, and 0.04, respectively). Proliferation after allo-DC exposure was also significantly enhanced by lenalidomide treatment (P<0.05). GMCSF/K562 “bystander” vaccine-increased proliferation to allo-DC antigens in CD4+ and CD8+ T cells without exposure to lenalidomide (n=4) (167% increase vs. 245% increase, respectively). When allo-DC-stimulated PBMCs were treated with lenalidomide alone, CD4+ and CD8+ proliferation was increased by 47% and 39% respectively. The combination of lenalidomide and the GMCSF/K562 vaccine further enhanced T cell proliferation to allo-DC stimulation (325% and 397% for CD4+ and CD8+ populations, respectively).
Conclusion: Lenalidomide significantly augments T cell immune function in MDS, and potentiates immune response to the GMCSF/K562 “bystander” vaccine. We conclude that lenalidomide represents an attractive adjunct to vaccines for clinical investigation in MDS.
Keratinocytes Regulate the Threshold of Inflammation by Inhibiting T Cell Effector Functions