chA21-28z chimeric antigen receptor T cells inhibit tumor growth in vivo . (A) Two million SKBR3 tumor cells were injected subcutaneously into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice, followed by intravenous treatment with T cells beginning on either day 40 or day 47 after tumor inoculation. Tumors regressed in response to injections of chA21-28z chimeric antigen receptor (CAR) T cells (triangles). Tumors grew progressively in mice (squares) that received nontransduced (NT) T-cell injections. HER2 CAR T cells inhibited tumor growth to a significantly greater extent compared to the control group (P = 0.00012). (B) SKBR tumors were dissected, and photographs of four representative samples are shown. (C) Graphed tumor weight data. Values are expressed as mean ± SEM. (D) SKBR3 tumors were collected from killed mice and stained for human CD3 expression (brown). Representative sections are shown at 100× original magnification.