Objective To investigate the effect and potential mechanism of chimeric antigen receptor(CAR)-natural killer(NK)cell therapy on the growth of gastric cancer cells and xenograft tumors.Methods Cell experiments:The gastric cancer cell lines of SGC7901 and MGC803 were co-cultured with CAR-NK cells as the CAR-NK group,the NK cells were co-cultured with SGC7901 and MGC803 cells as the NK group,respectively.The mRNA levels of PD-1 and PD-L1 in both groups were detected by RT-qPCR.The cell proliferation ability was assessed using EdU staining and CCK-8 assay.The cell migration and invasion abilities were detected by Transwell assay.The change of cell cycle was detected by flow cytometry.The expression of PD-1 and PD-L1 proteins in cells was detected by Western blot.Animal experiments:Mice were established model of xenograft tumors and divided into the blank control group(inoculated with routinely cultured SGC7901 cells),NK treatment group(inoculated SGC7901 cells combined NK cells),CAR-NK treatment group(inoculated SGC7901 cells combined CAR-NK cells),CAR-NK+rhPD-1 treatment group(inoculated SGC7901 cells combined CAR-NK cells,with intraperitoneal injection of 5 mg/kg rhPD-1 concurrently),and CAR-NK+rhPD-L1 treatment group(inoculated SGC7901 cells combined CAR-NK cells,with intraperitoneal injection of 5 mg/kg rhPD-L1 concurrently),with 5 mice in each group.The tumor volume of each group was observed,the tumor weight was recorded,and the expression of PD-1 and PD-L1 proteins in the tumor tissue of each group were detected by Western blot.Results Compared to the NK group,the CAR-NK group showed significantly decreased proliferation rate,and numbers of migration and invasion of SGC7901 and MGC803 cells(P<0.05).Compared to the NK group,the number of S phase cells increased,while G2/M phase cells decreased in the CAR-NK group(P<0.05).Compared to the NK group,the mRNA and protein expression levels of PD-1 and PD-L1 significantly downregulated in SGC7901 cell of the CAR-NK group(P<0.05).In the xenograft mouse model,compared to the NK treatment group,the protein expression of PD-1 and PD-L1 downregulated in the tumor tissues of the CAR-NK treatment group,with smaller tumor volume and decreased tumor weight,the differences were statistically significant(P<0.05).Compared to the blank control group,the CAR-NK treatment group exhibited downregulated protein expression of PD-1 and PD-L1 in tumor tissues,reduced tumor volume,and decreased tumor weight,with statistically significant differences(P<0.05).Compared to the CAR-NK treatment group,the CAR-NK+rhPD-1 treatment group showed upregulated expression of PD-1 protein,large tumor volume,and increased tumor weight,with statistically significant differences(P<0.05).Compared to the CAR-NK treatment group,the CAR-NK+rhPD-L1 treatment group exhibited upregulated expression of PD-L1 protein,large tumor volume,and increased tumor weight,with statistically significant differences(P<0.05).Conclusion CAR-NK cell therapy have a significant inhibitory effect on the proliferation,migration,and invasion of gastric cancer cells,resulting in the gastric cancer cell cycle arrest,which may inhibit the growth of xenograft tumors by inhibiting the PD-1/PD-L1 axis.

Objective To investigate the effect and potential mechanism of chimeric antigen receptor(CAR)-natural killer(NK)cell therapy on the growth of gastric cancer cells and xenograft tumors.Methods Cell experiments:The gastric cancer cell lines of SGC7901 and MGC803 were co-cultured with CAR-NK cells as the CAR-NK group,the NK cells were co-cultured with SGC7901 and MGC803 cells as the NK group,respectively.The mRNA levels of PD-1 and PD-L1 in both groups were detected by RT-qPCR.The cell proliferation ability was assessed using EdU staining and CCK-8 assay.The cell migration and invasion abilities were detected by Transwell assay.The change of cell cycle was detected by flow cytometry.The expression of PD-1 and PD-L1 proteins in cells was detected by Western blot.Animal experiments:Mice were established model of xenograft tumors and divided into the blank control group(inoculated with routinely cultured SGC7901 cells),NK treatment group(inoculated SGC7901 cells combined NK cells),CAR-NK treatment group(inoculated SGC7901 cells combined CAR-NK cells),CAR-NK+rhPD-1 treatment group(inoculated SGC7901 cells combined CAR-NK cells,with intraperitoneal injection of 5 mg/kg rhPD-1 concurrently),and CAR-NK+rhPD-L1 treatment group(inoculated SGC7901 cells combined CAR-NK cells,with intraperitoneal injection of 5 mg/kg rhPD-L1 concurrently),with 5 mice in each group.The tumor volume of each group was observed,the tumor weight was recorded,and the expression of PD-1 and PD-L1 proteins in the tumor tissue of each group were detected by Western blot.Results Compared to the NK group,the CAR-NK group showed significantly decreased proliferation rate,and numbers of migration and invasion of SGC7901 and MGC803 cells(P<0.05).Compared to the NK group,the number of S phase cells increased,while G2/M phase cells decreased in the CAR-NK group(P<0.05).Compared to the NK group,the mRNA and protein expression levels of PD-1 and PD-L1 significantly downregulated in SGC7901 cell of the CAR-NK group(P<0.05).In the xenograft mouse model,compared to the NK treatment group,the protein expression of PD-1 and PD-L1 downregulated in the tumor tissues of the CAR-NK treatment group,with smaller tumor volume and decreased tumor weight,the differences were statistically significant(P<0.05).Compared to the blank control group,the CAR-NK treatment group exhibited downregulated protein expression of PD-1 and PD-L1 in tumor tissues,reduced tumor volume,and decreased tumor weight,with statistically significant differences(P<0.05).Compared to the CAR-NK treatment group,the CAR-NK+rhPD-1 treatment group showed upregulated expression of PD-1 protein,large tumor volume,and increased tumor weight,with statistically significant differences(P<0.05).Compared to the CAR-NK treatment group,the CAR-NK+rhPD-L1 treatment group exhibited upregulated expression of PD-L1 protein,large tumor volume,and increased tumor weight,with statistically significant differences(P<0.05).Conclusion CAR-NK cell therapy have a significant inhibitory effect on the proliferation,migration,and invasion of gastric cancer cells,resulting in the gastric cancer cell cycle arrest,which may inhibit the growth of xenograft tumors by inhibiting the PD-1/PD-L1 axis.