[Study on construction of c-Met specific CAR-T cells and its killing effect on non-small cell lung carcinoma].

Objective: To produce chimeric antigen receptor T cells (CAR-T) targeting human hepatocyte growth factor/c-Met (HGF/c-Met) protein and detect its cytotoxicity against non-small cell lung cancer (NSCLC) cells H1975 in vitro. Methods: The whole gene sequence of c-Met CAR containing c-Met single-chain fragment variable was synthesized and linked to lentiviral vector plasmid, plasmid electrophoresis was used to detect the correctness of target gene. HEK293 cells were transfected with plasmid and the concentrated solution of the virus particles was collected. c-Met CAR lentivirus was transfected into T cells to obtain second-generation c-Met CAR-T and the expression of CAR sequences was verified by reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) and western blot, and the positive rate and cell subtypes of c-Met CAR-T cells were detected by flow cytometry. The positive expression of c-Met protein in NSCLC cell line H1975 was verified by flow cytometry, and the negative expression of c-Met protein in ovarian cancer cell line A2780 was selected as the control. The cytotoxicity of c-Met CAR-T to H1975 was detected by lactate dehydrogenase (LDH) cytotoxicity assay at 1∶1, 5∶1, 10∶1 and 20∶1 of effector: target cell ratio (E∶T). Enzyme-linked immunosorbent assay (ELISA) was used to detect the release of cytokines such as TNF-α, IL-2 and IFN-γ from c-Met CAR-T co-cultured with H1975. Results: The size of band was consistent with that of designed c-Met CAR, suggesting that the c-Met CAR plasmid was successfully constructed. The results of gene sequencing were consistent with the original design sequence and lentivirus was successfully constructed. CAR molecules expression in T cells infected with lentivirus was detected by western blot and RT-qPCR, which showed c-Met CAR-T were successfully constructed. Flow cytometry results showed that the infection efficiency of c-Met CAR in T cells was over 38.4%, and the proportion of CD8(+) T cells was increased after lentivirus infection. The NSCLC cell line H1975 highly expressed c-Met while ovarian cancer cell line A2780 negatively expressed c-Met. LDH cytotoxicity assay indicated that the killing efficiency was positively correlated with the E∶T, and higher than that of control group, and the killing rate reached 51.12% when the E∶T was 20∶1. ELISA results showed that c-Met CAR-T cells released more IL-2, TNF-α and IFN-γ in target cell stimulation, but there was no statistical difference between c-Met CAR-T and T cells in the non-target group. Conclusions: Human NSCLC cell H1975 expresses high level of c-Met which can be used as a target for immunotherapy. CAR-T cells targeting c-Met have been successfully produced and have high killing effect on c-Met positive NSCLC cells in vitro.

[Establishment of a dual-fluorescence-traced lung cancer subcutaneous transplantation model in nude mice].

Objective: To establish a nude mouse model of subcutaneous lung cancer using dual fluorescence reporting genes of luciferase (Luc) and near-infrared fluorescent protein (iRFP). Methods: The Luc and iRFP expressed lentiviral vector was constructed by Gateway method. After verified by sequencing, the lentivirus particle was prepared and infected into lung cancer A549 cells. Successfully infected A549 (mA549) cells were selected by puromycin and amplified. The expression of Luc and iRFP were observed under fluorescence microscope, and the expression of c-Met protein on the cell surface was detected by immunofluorescence. Twelve female nude mice were randomly divided into 2 groups, 6 in each group. A549 and mA549 cells were inoculated subcutaneously into the right forelimb of nude mice. The growth and fluorescence expression of the tumor were observed by in vivo imaging. The tumor formation was evaluated by hematoxylin-eosin (HE) staining and immunohistochemistry. Results: The Luc and iRFP stably expressed mA549 cell line was successfully constructed. The expressions of iRFP and Luc in mA549 cells were observed under fluorescence microscope. The results of immunofluorescence showed that c-Met protein expressed in both A549 cells and mA549 cells. The growth period of mA549 xenograft in nude mice was moderate and the tumorigenesis rate was 100%. The growth trend of mA549 cells in vivo was not significantly different from that of A549 cells (P>0.05). HE staining and immunohistochemistry results showed that the tumor issues displayed typical histopathological features of tumor. Immunohistochemistry results showed that both A549 and mA549 tumors expressed c-Met protein. Conclusion: A stable, real-time monitoring model of iRFP-Luc-A549 lung cancer cell xenograft in nude mice was successfully constructed.