In contrast to the comparable activity of NKAB-EGFR, NKAB-ErbB2 or a combination of the NKAB molecules seen with GL261 cells expressing both target antigens (Figure 6A, right), treatment of the heterogeneous tumor cell culture of GL261/EGFR and GL261/ErbB2 cells with NKAR-NK cells and a single NKAB antibody resulted in much less pronounced target cell killing than the combination of NKAB-EGFR and NKAB-ErbB2 (Figure 6C, left). The gene discussed is ERBB2; the disease is neoplasm.