Can the dual-functional capability of CIK cells be used to improve antitumor effects?

•CIK cells combine the characteristic of NK cells with T cells.•The mechanisms of CIK cell cytotoxicity are still not clear.•CIK cells therapy is a novol strategy for the treatment of tumors.•CIK cells therapy is worthwhile optimization.

Cytokine-induced killer (CIK) cells, which display both potent anti-tumor ability of T lymphocytes and non-major histocompatibility complex (MHC) restricted killing tumor cells capacity of natural killer (NK) cells are capable of recognizing and lysing a broad array of tumor targets. They have begun to be used in clinical care with good prospects for treatment success. CIK cells are a heterogeneous cell population that contain CD3+CD56+ cells, CD3−CD56+ natural killer (NK) cells and CD3+CD56− T cells on which much attention has been focused. This review will summarize the connections and differences among CD3+CD56+CIK cells, CD3−CD56+ NK cells and CD3+CD56− T cells in the following aspects: the main cell surface molecule, killing mechanism, and clinical applications so that treatment with CIK cells can be optimized and further to enhance the antitumor effect.