Comparison of cytotoxic dynamics between cytokine-induced killer cells and natural killer cells at the single cell level

Abstract

Abstract Although much has been learned about the cytotoxic mechanisms of cytokine-induced killer (CIK) and natural killer (NK) cells, little is known about how they kill cancer cells at the single-cell level. In the present study, we examined the contact dynamics of CIK and NK cells at the single-cell level by using time-lapse imaging. CIK cells killed MHC-I-negative and -positive cancer cells, but NK cells destroyed MHC-I-negative cells only. Moreover, CIK cells moved in all directions and showed longer tracks than did NK cells. CIK cells showed higher displacement and straightness scores than did NK cells, which indicates long-distance random migration of CIK cells. CIK and NK cells moved at 6.7 mm/min and 4.5 mm/min on average, respectively. These data suggest that CIK cells are likely moving more actively than NK cells. The average threshold number of CIK cells required to kill an individual cancer cell was 6.7 for MHC-I-negative cells and 6.9 for MHC-I-positive cells. That of NK cells was 2.4 for MHC-I-negative cells. Likely due to the higher threshold numbers, killing by CIK cells was delayed in comparison with NK cells: 40% of MHC-negative target cells were killed after 5 h when co-cultured with CIK cells and after 2 h with NK cells. Our data have implications for the rational design of CIK or NK cell–based immunotherapy of cancer patients