Impact of Lenalidomide Maintenance Therapy on Immune Polarization and Activation in Multiple Myeloma

BACKGROUND: Lenalidomide is an immunomodulatory drug (IMiD) with co-stimulatory effects on immune effector cells in vitro and is an approved treatment for multiple myeloma (MM), although its mode of action in patients is not well defined. We studied the impact of lenalidomide maintenance therapy, following autologous stem cell transplant (ASCT), on NK and NK-T polarization (i.e. activating or inhibitory molecules) and, T cell activation (early vs. late activation) in patients with multiple myeloma.

PATIENTS AND METHODS: In this ongoing prospective study with a targeted enrollment of 28 newly diagnosed multiple myeloma patients, blood samples are being collected at 2 to 3 months post ASCT, before starting lenalidomide maintenance therapy (baseline), and serially after 1, 3 and 6 months of treatment (T+1mo, T+3mo, T+6mo). Using a 9 color flow cytometry panel, peripheral blood samples were analyzed for expression of CD3 and CD56 to define NK (CD56+ CD3-), NKT (CD56+ CD3+), and T cell (CD56- CD3+) subsets. Killer 'inhibitory' Ig-like receptors, (KiR2DS4, KiR3DL1) natural killer group 2 proteins (NKG2a, NKG2D) and natural killer p46 protein (NKp46) expression were quantified to assess polarization of NK, and NK-T cells. Programmed death receptor 1 (PD-1) and T-cell Ig and mucin receptor 3 (Tim3) expression was quantified to assess T cell activation state. Flow cytometry data were acquired on a BD FACSAria II, and analyzed using FlowJo version X software.

RESULTS: Samples from 11 patients have been collected and analyzed so far (11 baseline, 6 T+1mo, 4 T+3mo). At baseline lymphoid cells represent 12-46% of white blood cells (WBC), this heterogeneity being mainly driven by a wide range of T cell relative distribution among patients (30-74 % lymphoid cells). Phenotypically, NK cells at baseline mainly express natural cytotoxicity receptors (NKp46 and NKG2D), whereas NK-T cell also express NKG2D but approximately 1/3 also express PD-1 indicating they may be functionally defective. T cells at baseline express early T cell activation markers NKG2D and approximately 1/3 also stained positive for late T cell activation marker PD-1. Lymphoid cells relative distribution among WBC tends to normalize at T+1mo of treatment (15 to 35 % of WBC) before expanding at T+3mo (35 to 43 % of WBC). Phenotypically, across the 27 immune variables analyzed, each multiple myeloma patient displayed high level of immune homeostasis after 1 or 3 months of lenalidomide treatment. Noticeably, Nkp46 expression by NK cell and PD-1 expression by NK-T cells decreased in 4/6 patients and, NKG2D expression by T cell decreased in all but one patient during lenalidomide therapy.

CONCLUSION: To our knowledge, this is the first study examining the influence of lenalidomide maintenance on the comprehensive immune repertoire in the post-ASCT setting in MM patients. The wide heterogeneity of NK, NK-T and T cell distribution observed at baseline among lymphoid cells indicates the potential effect of post-ASCT immune reconstitution and immunomodulatory the impact of lenalidomide. The capacity of lenalidomide to mediate effects on several immune cells raises the question as to which, if any, of these changes correlate with clinical responses. In our study, serially collected data from each patient, when completed would determine the impact of lenalidomide immunomodulatory effect of therapeutic efficacy and PFS duration in relation to immune reconstitution stage.