Objective:To design the fourth-generation chimeric antigen receptor-T (CAR-T) cells that secrete interleukin-7 (IL7) and chemokine C legend 19 (CCL19) on the basis of the second-generation CAR, and to analyze and compare the differences in proliferation, chemotaxis, tumor cell clearance and persistence in the microenvironment of multiple myeloma (MM) between them.Methods:The fourth-generation CAR vector plasmid was constructed by using 2A self-cleaving peptide technology. The third-generation lentiviral packaging system was used to prepare high-titer lentivirus. Flow cytometry was used to monitor the transduction efficiency of lentivirus and the subtype changes of CAR-T cells. The enzyme-linked immunosorbent assay (ELISA) was used to quantify the IL7 and CCL19 secreted by CAR-T cells.The calculation of absolute number of CAR-T cells during culture was used to analysis cell proliferation activity. Transwell migration assay was used to verify the chemotactic ability of CAR-T cells. The specific killing activity of CAR-T cells was detected by using the luciferase bioluminescence method. The NOD-Prkdcem26Cd52Il2rgem26Cd22/Nju (NOD) mouse xenograft model was used to verify the anti-myeloma activity and safety of CAR-T cells in vivo.Results:Flow cytometry results showed that the stable CAR expression rates of the second-generation anti-CS1 CAR-T and fourth-generation anti-CS1-IL7-CCL19 CAR-T cells were (91.50±0.29)% and (46.7±0.12)%, respectively. CAR-T cells were successfully constructed. Subtype analysis demonstrated that the ratio of stem memory T cell (TSCM) in anti-CS1-IL7-CCL19 CAR-T cells was (67.58±0.59)%, which was significantly higher than (50.74 ± 1.01)% of anti-CS1 CAR-T ( P=0.000 1), with more strong immune memory function and better durability. Anti-CS1-IL7-CCL19 CAR-T cells can continuously secrete IL7 and CCL19 compared to MOCK-T and anti-CS1 CAR-T ( P<0.000 1). The number of anti-CS1-IL7-CCL19 CAR-T cells reached (22.77±0.79)×10 6 on the 9th day after lentivirus transduction, which was significantly higher than (9.40±0.79)×10 6 of anti-CS1 CAR-T cells ( P=0.000 1), with stronger proliferation ability. The number of chemotaxis cells of anti-CS1-IL7-CCL19 CAR-T cells to reactive T cells was (109.0±4.04), which was significantly higher than (9.33±1.20) of MOCK-T ( P<0.000 1) and (7.33±0.88) of anti-CS1 CAR-T ( P<0.000 1), with stronger chemotactic ability. The specific killing activity showed that both anti-CS1-IL7-CCL19 CAR-T and anti-CS1 CAR-T cells had specific killing efficacies when compared with the MOCK-T cells ( P<0.000 1). Animal experiment indicated that anti-CS1-IL7-CCL19 CAR-T cells significantly reduced the tumor burden ( P<0.000 1) and extended the overall survival time ( P=0.006 1) of tumor-bearing mice. Conclusions:The anti-CS1-IL7-CCL19 CAR-T cells designed in this study show stronger proliferative activity, chemotactic ability, and durability without affecting the anti-myeloma activity in vivo and in vivo, which provides strategies for overcoming the defects of low survival rate, poor durability and inhibition by tumor microenvironment of traditional CAR-T cells, and offers preliminary experimental basis for the clinical application of the fourth-generation CAR-T cells.

Objective:To design the fourth-generation chimeric antigen receptor-T (CAR-T) cells that secrete interleukin-7 (IL7) and chemokine C legend 19 (CCL19) on the basis of the second-generation CAR, and to analyze and compare the differences in proliferation, chemotaxis, tumor cell clearance and persistence in the microenvironment of multiple myeloma (MM) between them.Methods:The fourth-generation CAR vector plasmid was constructed by using 2A self-cleaving peptide technology. The third-generation lentiviral packaging system was used to prepare high-titer lentivirus. Flow cytometry was used to monitor the transduction efficiency of lentivirus and the subtype changes of CAR-T cells. The enzyme-linked immunosorbent assay (ELISA) was used to quantify the IL7 and CCL19 secreted by CAR-T cells.The calculation of absolute number of CAR-T cells during culture was used to analysis cell proliferation activity. Transwell migration assay was used to verify the chemotactic ability of CAR-T cells. The specific killing activity of CAR-T cells was detected by using the luciferase bioluminescence method. The NOD-Prkdcem26Cd52Il2rgem26Cd22/Nju (NOD) mouse xenograft model was used to verify the anti-myeloma activity and safety of CAR-T cells in vivo.Results:Flow cytometry results showed that the stable CAR expression rates of the second-generation anti-CS1 CAR-T and fourth-generation anti-CS1-IL7-CCL19 CAR-T cells were (91.50±0.29)% and (46.7±0.12)%, respectively. CAR-T cells were successfully constructed. Subtype analysis demonstrated that the ratio of stem memory T cell (TSCM) in anti-CS1-IL7-CCL19 CAR-T cells was (67.58±0.59)%, which was significantly higher than (50.74 ± 1.01)% of anti-CS1 CAR-T ( P=0.000 1), with more strong immune memory function and better durability. Anti-CS1-IL7-CCL19 CAR-T cells can continuously secrete IL7 and CCL19 compared to MOCK-T and anti-CS1 CAR-T ( P<0.000 1). The number of anti-CS1-IL7-CCL19 CAR-T cells reached (22.77±0.79)×10 6 on the 9th day after lentivirus transduction, which was significantly higher than (9.40±0.79)×10 6 of anti-CS1 CAR-T cells ( P=0.000 1), with stronger proliferation ability. The number of chemotaxis cells of anti-CS1-IL7-CCL19 CAR-T cells to reactive T cells was (109.0±4.04), which was significantly higher than (9.33±1.20) of MOCK-T ( P<0.000 1) and (7.33±0.88) of anti-CS1 CAR-T ( P<0.000 1), with stronger chemotactic ability. The specific killing activity showed that both anti-CS1-IL7-CCL19 CAR-T and anti-CS1 CAR-T cells had specific killing efficacies when compared with the MOCK-T cells ( P<0.000 1). Animal experiment indicated that anti-CS1-IL7-CCL19 CAR-T cells significantly reduced the tumor burden ( P<0.000 1) and extended the overall survival time ( P=0.006 1) of tumor-bearing mice. Conclusions:The anti-CS1-IL7-CCL19 CAR-T cells designed in this study show stronger proliferative activity, chemotactic ability, and durability without affecting the anti-myeloma activity in vivo and in vivo, which provides strategies for overcoming the defects of low survival rate, poor durability and inhibition by tumor microenvironment of traditional CAR-T cells, and offers preliminary experimental basis for the clinical application of the fourth-generation CAR-T cells.

Objective:To construct the second and fourth generations of CAR-T cells targeting fibroblast activation protein (FAP) on the surface of stromal carcinoma-associated fibroblasts and compare their characteristics in vitro and in vivo. Methods:ELISA was used to detect the cytokines secreted by CAR-T cells. Cell proliferation and viability were analyzed by counting. Chemotactic ability was tested by Transwell migration assay. Distribution of T cell subsets was analyzed by flow cytometry. Cytotoxicity was assessed by luciferase bioluminescence. The safety and therapeutic effects were evaluated in a NOG mouse model of metastatic human lung cancer.Results:The expression rates of the second and fourth generations of CAR-T cells (h4BBz CAR-T and h4BBz-7.19 CAR-T) were (74.280±4.384)% and (67.220±4.013)%, respectively. The h4BBz-7.19 CAR-T cells had better in vitro proliferation and chemotactic activity than h4BBz CAR-T cells as they were able to secrete IL-7 and CCL19, while the viability of h4BBz-7.19 CAR-T cells was comparable to that of h4BBz CAR-T cells. There was no significant difference in the expression rate of h4BBz CAR or h4BBz-7.19 CAR between CD4 + T and CD8 + T cells. The proportions of both Naive cells and T memory stem cells (TSCM) in CD4 + and CD8 + T cells were higher in h4BBz-7.19 CAR-T cells than in h4BBz CAR-T cells. Moreover, h4BBz-7.19 CAR-T cells possessed stronger specific cytotoxicity on the target cancer cells than h4BBz CAR-T cells when the ratio of effectors/targets was low ( P1∶1=0.004, P2∶1=0.000 6, P5∶1<0.000 1, P10∶1=0.022, P20∶1=0.116), while the expression of PD-1 on the surface of h4BBz-7.19 CAR-T cells was lower than that on h4BBz CAR-T cells. In the NOG mouse model of metastatic human lung cancer, h4BBz-7.19 CAR-T cells could slow the tumor growth and prolong the survival time of mice without causing weight loss or pathological changes in the organs. Conclusions:The fourth-generation CAR-T cells targeting FAP were shown to have stronger proliferation, better penetration and more potent specific cytotoxicity by secreting IL-7 and CCL19 and could slow the tumor growth and prolong survival by improving tumor immunosuppressive microenvironment. This study provided reference for the clinical application of the fourth generation of CAR-T cells.