KLRK1 and neoplasm: Furthermore, blocking NKG2D significantly reduced the efficacy of CAR-modified CIK cells against ErbB2-expressing tumor targets, suggesting that the combination of NKG2D-mediated and ErbB2-specific killing in CAR-CIKs may reduce the impact of tumor escape mechanisms and increase killing of tumors with a relatively low and heterogeneous expression of ErbB2, such as most STS tumors.