Two methods for treating a tumor are disclosed. The first method includes (i) obtaining NK cells or NKT cells from a subject, (ii) transducing the NK cells or NKT cells in vitro with an expression vector encoding a chimeric antigen receptor that contains an scFv specifically recognizing stage-specific embryonic antigen 4, (iii) expanding the transduced NK cells or NKT cells in vitro, and (iv) infusing the expanded transduced NK cells or NKT cells into the subject. The second method includes, in place of step (ii) above, transducing the NK cells or NKT cells in vitro with an expression vector encoding a chimeric antigen receptor that is specific for a tumor antigen other than stage-specific embryonic antigen 4, and further requires a step of administering an antibody against stage-specific embryonic antigen 4.
