Allogeneic natural killer cells for refractory lymphoma

Abstract

We reported that IL-2 activated autologous NK cells can induce, but not maintain durable remissions in lymphoma patients. We hypothesized that allogeneic NK cells may overcome class I MHC-mediated inhibition of NK cell killing. In a pilot study, we evaluated infusion of haploidentical donor NK cells for antitumor efficacy. Six patients with advanced B cell non-Hodgkin lymphoma (NHL) received rituximab, cyclophosphamide, and fludarabine as immunosupression to permit homeostatic NK cell expansion, followed by CD3-depleted NK cell-enriched cell products followed by subcutaneous IL-2 administration (10 x 10(6) units every other day x 6 doses). At 2 months, four patients showed an objective clinical response. We observed early donor cell persistence in two patients (blood and in tumor-bearing node), but this was not detectable beyond 7 days. All patients demonstrated substantial increases in host-regulatory T cells (Treg) after NK cell and IL-2 therapy (180 +/- 80 cells/microl vs. baseline: 58 +/- 24 cells/microl, p = 0.04) which may have limited donor cell expansion in vivo. These findings suggest safety and feasibility of allogeneic NK cell therapy in patients with lymphoma; however host Treg and inadequate immunodepletion may contribute to a hostile milieu for NK cell survival and expansion. Cell therapy trials should incorporate novel strategies to limit Treg expansion.

Fig. 1

a Allogeneic NK cell products and ex vivo expansion. Total nucleated cell (TNC), CD56⁺/CD3⁻ NK cell and CD3⁺ T cell frequencies (mean ± SEM) in six apheresis products, after CD3 depletion and overnight activation with 1,000 IU/ml IL-2. b CD3 depleted clinical products (n = 6) were tested in Cr₅₁ release cytotoxic assay against K562 targets before and after ex vivo incubation with 1,000 IU/ml IL-2 at E:T ratio as shown (*p < 0.05). c Regulatory T cells increase after NK cell and IL-2 therapy. Patients with refractory lymphoma received pre-infusion chemotherapy, haploidentical donor NK cell infusion and IL-2 × 6 doses. Absolute numbers of regulatory T cells, cytotoxic CD3⁺CD4⁻ lymphocytes, serum levels of tumor necrosis factor receptor 1 and IL-10 are compared at baseline and at day 14. Mean cell frequencies ± SEM of five evaluable patients are shown (*p < 0.05). d Flow cytometric detection of T lymphocytes subsets and Treg in peripheral blood at baseline, days 0 (prior to allogeneic NK cells infusion) and 14 (following IL-2 therapy) are compared. Representative plot from patient #6 is shown