Regional delivery of mesothelin-targeted chimeric antigen receptor T-cell effectively and safely targets colorectal cancer liver metastases in mice.

BACKGROUND: Liver metastasis is the major cause of colorectal cancer related death. Mesothelin (MSLN)-targeted chimeric antigen receptor (CAR) T-cell therapy has been illustrated effective and safe through regional delivery of breast cancer, ovarian cancer and malignant mesothelioma tumors. Herein, we investigated the safety, efficacy, and immune microenvironment of regional delivery of MSLN (CAR) T-cell in the treatment of colorectal carcinoma liver metastases (CRLM).

METHODS: Second-generation MSLN CAR T-cells were administered by portal vein (PV) or caudal vein (CV, systemic administration) delivery in an orthotopic MSLN+ CRLM nonobese diabetic (NOD)/severe combined immunodeficient (SCID)/γc-/- (NSG) mouse model. A total of 20 mice were randomly divided into control group, non-transduced T cell (NT)-CV group, NT-PV group, MSLN CAR T-cell CV (MSLN-CV) group, and MSLN CAR T-cell PV (MSLN-PV) group, with each group containing four mice to examine the safety and efficacy. The bioluminescence intensity (BLI) of tumor burden, tumor tissue macroscopic and microscopic observation were used to evaluate treatment efficacy. The safety was examined by body weight, survival time, and vital organ damage of mice. CAR T-cell infiltration and cytokine concentration were analyzed by flow cytometry, and immunostaining. The change of immune microenvironment between regional delivery and systemic delivery was investigated on an immune reconstructed CRLM patient-derived xenograft (PDX) model. Additionally, T cell subsets and immunosuppressive markers were examined.

RESULTS: PV administration of 1×107 /100 μL MSLN CAR T-cells in 20 NSG mice was well tolerated, and no overt toxicity was observed. The tumor burden in the PV group was obviously alleviated. The BLI was (0.73±0.52)×109 in PV group and (1.97±0.11)×109 in CV group (P<0.05), CD8+ granzyme B (GB)+ T cell percentage (MSLN-CV 4.42%±0.47% vs. MSLN-PV 13.5%±4.67%, P<0.01) and cytokine concentration were obviously increased in the MSLN-PV group. In the immune reconstituted CRLM PDX model, intratumor (IT) delivery of MSLN CAR T-cells exhibited much more infiltration of CD4+ and CD8+ T cells accompanied with elevated expression levels of PD-1, LAG-3, and TIM-3.

CONCLUSIONS: Regional delivery of MSLN-targeted CAR T-cell therapy has encouraging results in the orthotopic CRLM NSG mouse model and PDX model, and converts the tumor microenvironment from cold to hot. This study may provide a new therapeutic approach for CRLM. Further clinical study is needed.