The effect of acute exercise and latent cytomegalovirus infection on NK-cell redeployment and anti-tumor cytotoxicity in healthy adults.

摘要

Allogeneic adoptive transfer of NK-cells from healthy donors to cancer patients has shown promise as a means of controlling or reversing the spread of multiple human malignancies including multiple myeloma and acute myeloid leukemia. However, multiple issues remain that undermine the efficacy of long-term cancer treatment using adoptive transfer of NK-cells including loss of activating receptors and cytotoxic potential in transferred NK-cells. We sought to improve the clinical usefulness of NK-cells by using either acute exercise or cytomegalovirus (CMV)-driven expansion of NKG2C+ NK-cells as an adjuvant. Acute exercise mobilizes NK-cells, while latent CMV infection is associated with impaired mobilization of NK-cells and expansion of NK-cells expressing the activating receptor NKG2C. Thus, we hypothesized that a single bout of exercise or latent CMV infection would be associated with enhanced anti-tumor cytotoxicity, and that latent CMV infection would be associated with a blunted increase in NK-cell cytotoxicity with exercise. This was divided into three specific hypotheses: 1) Exercise-induced changes in the composition of NK-cell subsets will increase anti-tumor cytotoxicity; 2) CMV-driven NKG2C+ NK-cell expansion will increase anti-tumor cytotoxicity; and 3) latent CMV infection will impair the exercise-induced mobilization of NK-cells through decreased beta-AR sensitivity. To test hypothesis 1, sixteen healthy cyclists performed three 30-minute bouts of cycling exercise at -5%, +5%, and +15% of blood lactate threshold. Blood samples were obtained before, immediately after, and 1h after exercise were used to enumerate NK-cells and their subsets, and determine NKCA and degranulating subsets (CD 107+) against cell lines of multiple myeloma (U266 and RPMI-8226), lymphoma (721.221 and 221 AEH), and leukemia (K562) origin by 4 and 10-color flow cytometry, respectively. To test hypothesis 2, 30 young healthy subjects donated blood samples to enumerate NK-cell subsets, NKCA (against U266, 721.221, 221 AEH, and K562 cells), and degranulating subsets in response to 221 AEH cells in the context of latent CMV infection. To test hypothesis 3, the same subjects from aim 1 were used and NK-cell responsiveness to exercise and beta-AR stimulation were explored in the context of latent CMV infection. In support of hypothesis 1, we found a 1h post-exercise increase in NK-cell anti-tumor cytotoxicity in association with a proportional increase in NK-cells lacking inhibitory KIR for classical HLA molecules and expressing activating receptor for HLA-E (NKG2C). In support of hypothesis 2, we found that latent CMV-infection was associated with a marked, NKG2C-dependent increase in NK-cell activity against tumor cell lines expressing HLA-E (U266, K562, and 221 AEH). In support of hypothesis 3, we found that latent CMV infection was associated with a blunted NK-cell redeployment and 1h post-exercise increase in NK-cell activity following exercise above the blood lactate threshold. This blunted NK-cell mobilization was associated with decreased beta2-AR expression and impaired beta-AR sensitivity. We conclude that exercise and CMV are both capable of enhancing NK-cell killing efficiency through distinct mechanisms; however, these effects are not additive as CMV infection is associated with an impaired exercise response. This works opens the door to using either exercise or in vitro expansion of NKG2C+ NK-cells as a simple strategy for enhancing the anti-tumor cytotoxicity of NK-cells for immunotherapy.