Abstract 2566: A TCL1-specific T-cell receptor redirects T cells against B-cell lymphomas and non-hematological tumors

T-cell leukemia/lymphoma Antigen1 (TCL1) is a B-cell oncoprotein that is overexpressed in multiple forms of B-cell lymphoma. In our previous study, we identified a HLA*A0201-restricted T cell epitope from TCL1 that stimulated CD8+ T cells to specifically lyse lymphoma cells. In this study, we have cloned the TCL170-79 peptide-specific T-cell receptor (TCR) gene that after lentivirus transduction into donor T cells can redirect the specificity of T cells to lyse T2 cells pulsed with TCL170-79 but not control peptide. The TCR-transduced CD8+ T cells efficiently lysed HLA-0201+, TCL1-expressing human lymphoma cell lines and primary lymphoma cells, but not normal B cells. Adoptive transfer of TCR-transduced T cells into a mantle cell lymphoma xenograft mouse model inhibited the tumor growth and significantly extended the survival of mice. In addition, we found that TCL1 is expressed in multiple solid tumors. The TCR-transduced T cells lysed colon and liver tumor cells but not normal human cells in vitro as well as in a mouse xenograft model. Collectively, our data demonstrate that TCL1-specific TCR-based immunotherapy is highly effective against human B-cell lymphomas and non-hematological tumors.

Citation Format: Jinsheng Weng, Kelsey E. Moriarty, Yong Pan, Flavio Egidio Baio, Hua Wang, Hiroki Torikai, Sourindra N. Maiti, Fuliang Chu, Xiaoyun Cheng, Swathi Karri, Deepshika Medapalli, Laurence J. N. Cooper, Sattva S. Neelapu. A TCL1-specific T-cell receptor redirects T cells against B-cell lymphomas and non-hematological tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2566.

IL-15 enhances the antitumor effect of human antigen-specific CD8+ T cells by cellular senescence delay

Optimal expansion protocols for adoptive human T-cell therapy often include interleukin (IL)-15; however, the mechanism by which IL-15 improves the in vivo antitumor effect of T cells remains to be elucidated. Using human T cells generated from HLA-A2+ donors against novel T-cell epitopes derived from the human U266 myeloma cell line Ig light chain V-region (idiotype) as a model, we found that T cells cultured with IL-15 provided superior resistance to tumor growth in vivo, compared with IL-2, after adoptive transfer into immunodeficient hosts. This effect of IL-15 was associated with delayed/reversed senescence in tumor antigen-specific memory CD8⁺ T cells mediated through downregulation of P21^WAF1, P16^INK4a, and P53 expression. Compared to IL-2, IL-15 stimulation dramatically activated JAK3-STAT5 signaling and inhibited the expression of DNA damage genes. Thus, our study elucidates a new mechanism for IL-15 in the regulation of STAT signaling pathways and CD8⁺ T-cell senescence.

Targeting B-cell malignancies through human B-cell receptor specific CD4+ T cells

The B-cell receptor (BCR) expressed by a clonal B cell tumor is a tumor specific antigen (idiotype). However, the T-cell epitopes within human BCRs which stimulate protective immunity still lack detailed characterization. In this study, we identified 17 BCR peptide-specific CD4⁺ T-cell epitopes derived from BCR heavy and light chain variable region sequences. Detailed analysis revealed these CD4⁺ T-cell epitopes stimulated normal donors' and patients' Th1 CD4⁺ T cells to directly recognize the autologous tumors by secretion of IFNγ, indicating the epitopes are processed and presented by tumor cells. One BCR peptide-specific CD4⁺ T cell line was also cytotoxic and lysed autologous tumor cells through the perforin pathway. Sequence analysis of the epitopes revealed that 10 were shared by multiple primary patients' tumors, and 16 had the capacity to bind to more than one HLA DRB1 allele. T cells stimulated by shared epitopes recognized primary tumors expressing the same sequences on multiple HLA DRB1 alleles. In conclusion, we identified 17 BCR-derived CD4⁺ T-cell epitopes with promiscuous HLA DRB1 binding affinity that are shared by up to 36% of patients, suggesting a strategy to overcome the requirement for individual preparation of therapeutic agents targeting idiotype.