Adoptive transfer of autologous natural killer cells leads to high levels of circulating natural killer cells but does not mediate tumor regression

Abstract

Purpose: Adoptive transfer of tumor-infiltrating lymphocytes (TIL) can mediate regression of metastatic melanoma. However, many patients with cancer are ineligible for such treatment because their TIL do not expand sufficiently or because their tumors have lost expression of antigens and/or MHC molecules. Natural killer (NK) cells are large granular lymphocytes that lyse tumor cells in a non-MHC-restricted manner. Therefore, we initiated in a clinical trial to evaluate the efficacy of adoptively transferred autologous NK cells to treat patients with cancers who were ineligible for treatment with TIL.

Experimental design: Patients with metastatic melanoma or renal cell carcinoma were treated with adoptively transferred in vitro activated autologous NK cells after the patients received a lymphodepleting but nonmyeloablative chemotherapy regimen. Clinical responses and persistence of the adoptively transferred cells were evaluated.

Results: Eight patients were treated with an average of 4.7 × 10(10) (± 2.1 × 10(10)) NK cells. The infused cells exhibited high levels of lytic activity in vitro. Although no clinical responses were observed, the adoptively transferred NK cells seemed to persist in the peripheral circulation of patients for at least one week posttransfer and, in some patients, for several months. However, the persistent NK cells in the circulation expressed significantly lower levels of the key activating receptor NKG2D and could not lyse tumor cell targets in vitro unless reactivated with IL-2.

Conclusions: The persistent NK cells could mediate antibody-dependent cell-mediated cytotoxicity without cytokine reactivation in vitro, which suggests that coupling adoptive NK cell transfer with monoclonal antibody administration deserves evaluation.

Conflict of interest statement

Conflict of Interest Disclosure

The authors have no financial conflicts of interest to declare.

©2011 AACR

Figures

Figure 1

Phenotype of NK cells activated in vitro with OKT3 and IL-2 at clinical scale. CD3+ T cells were depleted from whole PBMC using a Clinimacs machine and anti-CD3 reagent (Miltenyi Biotech) and were subsequently expanded in vitro with OKT3 and IL-2. On days 21 and 23, the resulting cell populations were evaluated by FACS for expression of a variety of activating and inhibitory NKRs and cytokine receptors.

Figure 2

Adoptively transferred NK cells persist in the peripheral circulation of patients. Blood was drawn from patients at multiple time points throughout treatment and was analyzed by the Hematology and Immunology Flow Cytometry Laboratories within the Department of Laboratory Medicine at the NIH Clinical Center to determine the absolute lymphocyte count (ALC) and absolute NK cell count (ANK). Normal NK cell counts range from 100 – 500 cells/μl as noted by the dashed lines on the graphs. Arrows indicate initiation of high dose IL-2 administration.

Figure 3

Adoptively transferred NK cells that persist in the peripheral circulation lose the ability to lyse tumor cells unless reactivated in vitro. PBMCs from patient 1 were collected at various time points after adoptive NK cell transfer as indicated. These cells and NK cells from the infused cell population were cultured for 2 days in the presence (A, B, and C) or absence (D, E, and F) of IL-2 and then evaluated for the ability to lyse two melanoma cell lines (888 and Sk23) in comparison to autologous PBMCs using standard 4-hour 51Cr release assays. Each symbol represents the average of 3 data points.

Figure 4

Adoptively transferred NK cells that persist in the peripheral circulation can mediate ADCC without in vitro reactivation. PBMCs from patient 1 were collected at 10 days (A) and 48 days (B) after adoptive NK cell transfer. At 10 days post-treatment, PBMCs contained 90% CD3-CD56+ NK cells, and at 48 days, PBMCs were 69% NK cells. These cells were cultured for 2 days in the presence or absence of IL-2 as noted and then evaluated for the ability to lyse antibody-coated tumor cells using standard 4-hour 51Cr release assays. Each symbol represents the average of 3 data points.