EGFRvIII-specific CAR-T cells produced by piggyBac transposon exhibit efficient growth suppression against hepatocellular carcinoma

Adoptive cellular immunotherapy employing chimeric antigen receptors-modified T (CAR-T) cells has demonstrated promising antitumor effects in hematologic cancers. However, CAR-T therapy confront many challenges in solid tumors like immunosuppressive microenvironment, molecular heterogeneity, etc. The cancer genome atlas (TCGA) of hepatocellular carcinoma (HCC) revealed many genetic characteristic and molecular tumorigenesis. EGFRvIII is a tumor specific antigen widely expressed in a variety of cancers including HCC and an ideal therapeutic target for cancer therapy. The liver cancer cell line SMMC7721 express high level EGFRvIII and widely applied in HCC investigations. Herein, we developed EGFRvIII CAR-T cells by piggyBac transposon system, and detected its specific killing effect against SMMC7721 cells in vitro and in vivo. Results indicated that transduction efficiency of CAR reached 53.1%. Expression of CAR protein was verified by immunoblotting as a band of approximate 57KD. The killing effect of CAR-T cells against SMMC7721 was positively correlated with E/T ratio (E:T=5:1, 10:1, 20:1, 40:1), and exceeded 50% at 20:1 ratio. Significant increase in IFN-γ and TNF-α secretion were detected in the co-culture supernatant of CAR-T cells and SMMC7721, comparable to the level of exogenous EGFRvIII-expressing U87 cells. The killing activity and cytokine secretion were both dependent on the expression level of EGFRvIII in target cells. In HCC xenograft models, CAR-T cells could effectively suppress the growth of SMMC7721. In conclusion, EGFRvIII CAR-T cells demonstrated specific antitumor effect against SMMC7721 in vitro and in vivo, providing basis for immunotherapy of HCC in future clinical use.