CLDN6 and neoplasm: Disappointingly, its effectiveness in treating solid tumors is still limited due to a lack of comprehensive understanding of tumor-specific antigens, the suppression of T-cell infiltration and killing ability by the TME, and limited expansion potential of T cells.315 Therefore, Mackensen et al. designed CAR-T cells targeting the tumor-specific antigen Claudin 6 (CLDN6) and demonstrated potential clinical activity.