Preclinical development of T-cell receptor-engineered T-cell therapy targeting the 5T4 tumor antigen on renal cell carcinoma.

5T4 (trophoblast glycoprotein, TPBG) is a transmembrane tumor antigen expressed on more than 90% of primary renal cell carcinomas (RCC) and a wide range of human carcinomas but not on most somatic adult tissues. The favorable expression pattern has encouraged the development and clinical testing of 5T4-targeted antibody and vaccine therapies. 5T4 also represents a compelling and unexplored target for T-cell receptor (TCR)-engineered T-cell therapy. Our group has previously isolated high-avidity CD8+ T-cell clones specific for an HLA-A2-restricted 5T4 epitope (residues 17-25; 5T4p17). In this report, targeted single-cell RNA sequencing was performed on 5T4p17-specific T-cell clones to sequence the highly variable complementarity-determining region 3 (CDR3) of T-cell receptor α chain (TRA) and ß chain (TRB) genes. Full-length TRA and TRB sequences were cloned into lentiviral vectors and transduced into CD8+ T-cells from healthy donors. Redirected effector T-cell function against 5T4p17 was measured by cytotoxicity and cytokine release assays. Seven unique TRA-TRB pairs were identified. All seven TCRs exhibited high expression on CD8+ T-cells with transduction efficiencies from 59 to 89%. TCR-transduced CD8+ T-cells demonstrated redirected cytotoxicity and cytokine release in response to 5T4p17 on target-cells and killed 5T4+/HLA-A2+ kidney-, breast-, and colorectal-tumor cell lines as well as primary RCC tumor cells in vitro. TCR-transduced CD8+ T-cells also detected presentation of 5T4p17 in TAP1/2-deficient T2 target-cells. TCR-transduced T-cells redirected to recognize the 5T4p17 epitope from a broadly shared tumor antigen are of interest for future testing as a cellular immunotherapy strategy for HLA-A2+ subjects with 5T4+ tumors.

RNA helicase, DDX3X, is actively recruited to sites of DNA damage in live cells.

Recent studies have suggested that human RNA helicase, DDX3X, is important for DNA repair, but little is known about the nuclear activity of this protein. In vitro analysis of nuclear DDX3X interactions and localization with DNA damage pointed to a direct role for DDX3X in the DNA damage response. We aimed to investigate whether DDX3X plays a direct role in the DNA damage response in live cells. In order to track nuclear DDX3X, we generated a nuclear-export deficient DDX3X mutant construct and performed microirradiation in live cells. We found that DDX3X accumulates at sites of microirradiation shortly after DNA damage induction. We further found DDX3X recruitment to be mediated by its intrinsically disordered domains, similar to other RNA binding proteins that are recruited to sites of DNA damage. Inhibition of liquid-liquid phase separation also reduced DDX3X recruitment. CRISPR/Cas9-mediated knockout of PARP1 ablated DDX3X recruitment, which was restored upon transgenic expression of wild-type PARP1 but not catalytically inactive PARP1, suggesting that DDX3X recruitment is PARP1-dependent.