T cells were isolated from 2 donor's PBMCs and transduced with HER2-CAR construct. The study evaluated the cytotoxic activity of HER2-CAR T cells against three cell lines: HER2-negative MDA cells and HER2-positive MDA-HER2 and MDA-HER2-231 cells. The results demonstrated significant cytotoxicity against MDA-HER2 cells, confirming the specificity of HER2-CAR T cells, while no cytotoxic effects were observed for HER2-negative MDA cells and MDA-HER2-231 cells, which had low expression of HER2 antigen. It implies that HER2-CAR T cells are unlikely to target healthy tissues with low expression of HER2. The same pattern was observed in the case of pre-activated T cells, and regardless of IL-2 and the donor of T cells.