Adoptive T-Cell Therapy with TCL1-Specific TCR for B-Cell Lymphomas

Chimeric antigen receptor (CAR)-modified T-cell therapy targeting CD19 induces high response rates in patients with relapsed or refractory B-cell lymphomas. However, about 60% of patients experience primary or secondary resistance after CD19-targeted CAR T-cell therapy and a major of cause of failure appears to be due to loss of CD19 expression on the tumor. Therefore, novel targets for adoptive T-cell therapeutic approaches are needed to further improve clinical outcome in these patients.

T-cell leukemia/lymphoma antigen1 (TCL1) is an oncoprotein that is overexpressed in multiple B-cell malignancies including follicular lymphoma (FL), mantle cell lymphoma (MCL), diffuse large B-cell lymphoma (DLBCL), and chronic lymphocytic leukemia (CLL). Importantly, it has restricted expression in only a subset of B cells among normal tissues. We previously identified a TCL1-derived HLA-A2-binding epitope (TCL1_70-79 SLLPIMWQLY) that can be used to generate TCL1-specific CD8+ T cells from peripheral blood mononuclear cells of both HLA-A2+ normal donors and lymphoma patients. More importantly, we showed that the TCL1-specific CD8+ T cells lysed autologous primary lymphoma cells but not normal B cells (Weng et al. Blood 2012).

To translate the above discovery into clinic, we cloned the T-cell receptor (TCR) alpha and beta chains from a TCL1-specific CD8⁺ T-cell clone and showed that this TCL1-TCR could be transduced into polyclonal donor T cells using a lentiviral system with a transduction efficiency of >40% as determined by TCL1_70-79 tetramer positive T cells. Furthermore, we demonstrated that the TCL1-TCR-transduced T cells recognized T2 cells pulsed with TCL1_70-79 peptide producing IFN- γ >8 ng/ml and IL-2 >350 ng/ml but were not reactive to control HIV-Gag peptide (IFN- γ <0.1 ng/ml and IL-2 <0.2 ng/ml). The TCL1-TCR-transduced T cells recognized TCL1_70-79 peptide pulsed onto T2 cells at a concentration of 1-10 nM (IL-2 >10 ng/ml) suggesting it has moderate to high avidity. Importantly, TCL1-TCR-transduced T cells lysed HLA-A2⁺ (up to 43% lysis of Mino and 25% lysis of Jeko-1 at 40:1 Effector:Target ratio) but not HLA-A2^- lymphoma cell lines (5.5% lysis of HLA A2^- Raji and 2.3% lysis of Daudi at 40:1 Effector:Target ratio). TCL1-TCR-transduced T cells were also cytotoxic to HLA-A2⁺ primary lymphoma tumor cells (up to 48% lysis of CLL, 43% lysis of FL, 41% lysis of DLBCL, 46% lysis of splenic marginal zone lymphoma, and 11% lysis of MCL at 40:1 Effector:Target ratio) but not normal B cells derived from the same patients. Lastly, TCL1-TCR transduced T cells showed high efficacy in in vivo models. Adoptive transfer of the TCL1-TCR-tranduced T cells significantly reduced lymphoma tumor growth and extended survival in Mino mantle cell lymphoma cell line xenograft model (48% survival in TCL1-TCR-T treated group vs. 12.5% survival in control group at 10 weeks n=7-8 mice/group; P=0.02).

Collectively, our data suggest that the high expression in B-cell tumors, restricted expression in normal tissues, and presence of an immunogenic CD8 T-cell epitope, make TCL1 a target for T cell-based therapeutic approaches in multiple B-cell malignancies. Our results also demonstrate that the TCL1-specific TCR-transduced T cells may serve as a novel adoptive immunotherapy approach for the treatment of patients with various B-cell malignancies (including FL, MCL, DLBCL, CLL).

Acknowledgments: This study is supported by MD Anderson Moon Shot Program and CPRIT and the National Natural Science Foundation of China Grant (No. 81570189)