IL15 Infusion of Cancer Patients Expands the Subpopulation of Cytotoxic CD56bright NK Cells and Increases NK-Cell Cytokine Release Capabilities.

The cytokine IL15 is required for survival and activation of natural killer (NK) cells as well as expansion of NK-cell populations. Here, we compare the effects of continuous IL15 infusions on NK-cell subpopulations in cancer patients. Infusions affected the CD56bright NK-cell subpopulation in that the expansion rates exceeded those of CD56dim NK-cell populations with a 350-fold increase in their total cell numbers compared with 20-fold expansion for the CD56dim subset. CD56bright NK cells responded with increased cytokine release to various stimuli, as expected given their immunoregulatory functions. Moreover, CD56bright NK cells gained the ability to kill various target cells at levels that are typical for CD56dim NK cells. Some increased cytotoxic activities were also observed for CD56dim NK cells. IL15 infusions induced expression changes on the surface of both NK-cell subsets, resulting in a previously undescribed and similar phenotype. These data suggest that IL15 infusions expand and arm CD56bright NK cells that alone or in combination with tumor-targeting antibodies may be useful in the treatment of cancer. Cancer Immunol Res; 5(10); 929-38. ©2017 AACR. ©2017 American Association for Cancer Research.