Fig. 5. The CD20-specific A23 TCR mediates rejection of established tumors in a syngeneic mouse model of cancer.

A Expression of HLA-A2 was measured by flow cytometry in the naturally HLA-A2⁺ human leukemia cell lines NALM-6 and BV-173 and in MC703 cells generated in HHD mice. To reach HLA-A2 levels in MC703 cells that are comparable to the human cell lines, the HHD transgene was retrovirally introduced (MC703/HHD). B MC703 and MC703-SLF tumor cells were incubated with A23 TCR-engineered HHD T cells and supernatants of 24 h co-cultures were analyzed for IFN-γ content by ELISA. One representative of two independent experiments is shown, and dots represent technical replicates. Growth of MC703-SLF (C) or MC703/HHD-SLF tumors (D) in HHDxRag1^−/− mice treated 3–4 weeks after tumor cell injection with A23 TCR-engineered HHD T cells (blue). Control animals received either HHD T cells engineered with TCR-DMF5 (MART-1 specific, gray) or were left untreated (no ATT, white). Numbers refer to treated animals (n) and to animals in which T-cell therapy achieved tumor rejection (r). The timepoint of adoptive T cell therapy (ATT) is indicated with an arrowhead. E MC703-SLF tumor cells either re-isolated from relapsed tumors depicted in (D) or cultured in vitro were incubated with A23 TCR-engineered HHD T cells. Supernatants of 24 h co-cultures were analyzed for IFN-γ content by ELISA. The relative amount of IFN-γ refers to the incubation of A23 TCR-Ts with MC703-SLF tumor cells cultured in vitro. Data shown are from one representative of two independent experiments performed, and dots represent technical replicates. F Expression of HHD on MC703-SLF tumor cells as determined by flow cytometry. Cells were derived from tumors that relapsed after treatment with A23 TCR-engineered HHD T cells depicted in (D) or from in vitro cultures.