KLRK1 and glioblastoma: The specific targeting of NKG2D-positive primary NK and NKAR-engineered NK-92 cells by NKAB-EGFR and NKAB-ErbB2 was investigated in cell-killing experiments with tumor cells expressing EGFR and/or ErbB2, and with mixed glioblastoma cell cultures mimicking the heterogeneous target antigen expression often observed in human tumors.