IL15 and cancer: To investigate the mechanisms of the increased cancer cell death, we first evaluated the expansion of NK cells in the lymphocyte: cancer cell co-cultures: We observed that the percentage of NK cells did not significantly change from the PBS control when the combination of IL-15 and ADU-S100 analog, or the ADU-S100 analog alone was used, although significant expansion was seen with IL-15 alone as previously described by ourselves and others (19, 39).