[In vitro and in vivo validation of cytotoxicity of targeting human epidermal growth factor receptor-2 chimeric antigen receptor T (HER2-CAR-T) cells].

Objective To evaluate the toxicology of targeting human epidermal growth factor receptor-2 chimeric antigen receptor T (HER2-CAR-T) cells and to provide a safety basis for the clinical evaluation of HER2-CAR-T cell therapy. Methods The recombinant lentiviral vector was used to generate HER2-CAR-T cells. Soft agar colony formation assay was used to observe the colony formation of HER2-CAR-T cells, and the colony formation rate was statistically analyzed. The HER2-CAR-T cell suspension was co-incubated with rabbit red blood cell suspension, and the hemolysis of red blood cells was evaluated by direct observation and microplate reader detection. The HER2-CAR-T cell preparation was injected into the ear vein of male New Zealand rabbits, and the stimulating effect of HER2-CAR-T cells on the blood vessels of the animals was observed by staining of tissue sections. The vesicular stomatitis virus envelope glycoprotein (VSV-G) gene of pMD 2.G vector was used as the target sequence, and the safety of the lentiviral vector was verified by real-time fluorescence quantitative PCR. The heart, liver, lung, and kidney of mice receiving HER2-CAR-T cell infusion were collected, and the lesions were observed by HE staining. Results The HER2-CAR-T cells were successfully prepared. These cells did not exhibit soft agar colony formation ability in vitro, and the HER2-CAR-T cell preparation did not cause hemolysis in New Zealand rabbit red blood cells. After the infusion of HER2-CAR-T cells into the ear vein of New Zealand rabbits, no obvious vascular stimulation response was found, and no specific amplification of VSV-G was detected. No obvious lesions were found in the heart, liver, lung and kidney tissues of the treatment group. Conclusion The prepared HER2-CAR-T cells have reliable safety.

SMAD7 expression in CAR-T cells improves persistence and safety for solid tumors.

Despite the tremendous progress of chimeric antigen receptor T (CAR-T) cell therapy in hematological malignancies, their application in solid tumors has been limited largely due to T-cell exhaustion in the tumor microenvironment (TME) and systemic toxicity caused by excessive cytokine release. As a key regulator of the immunosuppressive TME, TGF-ß promotes cytokine synthesis via the NF-κB pathway. Here, we coexpressed SMAD7, a suppressor of TGF-ß signaling, with a HER2-targeted CAR in engineered T cells. These novel CAR-T cells displayed high cytolytic efficacy and were resistant to TGF-ß-triggered exhaustion, which enabled sustained tumoricidal capacity after continuous antigen exposure. Moreover, SMAD7 substantially reduced the production of inflammatory cytokines by antigen-primed CAR-T cells. Mechanistically, SMAD7 downregulated TGF-ß receptor I and abrogated the interplay between the TGF-ß and NF-κB pathways in CAR-T cells. As a result, these CAR-T cells persistently inhibited tumor growth and promoted the survival of tumor-challenged mice regardless of the hostile tumor microenvironment caused by a high concentration of TGF-ß. SMAD7 coexpression also enhanced CAR-T-cell infiltration and persistent activation in patient-derived tumor organoids. Therefore, our study demonstrated the feasibility of SMAD7 coexpression as a novel approach to improve the efficacy and safety of CAR-T-cell therapy for solid tumors.

Humanized single-domain antibody targeting HER2 enhances function of chimeric antigen receptor T cells.

Introduction: Chimeric antigen receptors (CARs) can redirect T cells against antigen-expressing tumors, and each component plays an important role in the function and anti-tumor efficacy. It has been reported that using human sequences or a low affinity of CAR single-chain variable fragments (scFvs) in the CAR binding domains is a potential way to enhance the function of CAR-T cells. However, it remains largely unknown how a lower affinity of CARs using humanized scFvs affects the function of CAR-T cells until recently. Methods: We used different humanized anti-HER2 antibodies as the extracellular domain of CARs and further constructed a series of the CAR-T cells with different affinity. Results: We have observed that moderately reducing the affinity of CARs (light chain variable domain (VL)-based CAR-T) could maintain the anti-tumor efficacy, and improved the safety of CAR therapy both in vitro and in vivo compared with high-affinity CAR-T cells. Moreover, T cells expressing the VL domain only antibody exhibited long-lasting tumor elimination capability after multiple challenges in vitro, longer persistence and lower cytokine levels in vivo. Discussion: Our findings provide an alternative option for CAR-T optimization with the potential to widen the use of CAR T cells.

[Application of TARP luciferase reporter system in function identification of CAR-T cells].

Objective To investigate a convenient and quantitative solution to activation levels and functional characterization of CAR-T cells by inserting T cell activity-responsive promoter (TARP) nanoluciferase reporter gene system into a lentiviral plasmid containing the gene encoding the chimeric antigen receptor (CAR). Methods The recombinant plasmid was constructed by using whole gene synthesis and molecular cloning techniques. The lentivirus was packaged and was infected with human primary T lymphocytes. Flow cytometry was used to detected the positive rate of lentivirus-infected T cells. The functional characterization of CAR-T cells was identified by luciferase reporter gene system, Western blot, flow cytometry, and small animal live imaging techniques. Results The results of enzyme digestion identification and the plasmid sequencing showed that the recombinant plasmids were constructed, and flow cytometry displayed the normal preparation of CAR-T cells. This system could dynamically respond to the activation of CAR-T cells by luciferase reporter gene system. The functional assay in vitro confirmed that the system could reflect the exhaustion of CAR-T cells, and the small animal live imaging results demonstrated that the system can be used as a tracer of CAR-T cells in mice. Conclusion TARP nanoluciferase reporter gene system provides a more convenient, sensitive and quantitative method for evaluating CAR-T cells activation level, exhaustion phenotype and tracing.