Effect of chemotherapy drug cisplatin on the efficacy of B7H3 CAR-T cells in treating melanoma by increasing target antigen density.

Abstract

e21562 Background: B7H3 is overexpressed in multiple types of solid tumors, including melanoma, making it an ideal target for chimeric antigen receptor (CAR)-T cell therapy. However, the efficacy of B7H3 CAR-T cell therapies in solid malignancies is limited, due to multiple reasons. One of the major obstacles is antigen escape, B7H3 expression has been found to be downregulated under the tumor microenvironment. Conversely, B7H3 expression on tumor cells can be upregulated by treatments with radiotherapy or chemotherapeutic agents. Cisplatin is one of the most effective and widely used chemotherapeutic agents in the treatment of solid tumors. Methods: In this report, melanoma cells were pretreated with low-dose cisplatin, and the antitumor activity of B7H3-targeted CAR-T cells against these cisplatin-treated melanomas was evaluated. Moreover, high-throughput RNA-sequencing analysis was performed on the cisplatin-treated melanoma cells to further investigate the potential molecular mechanisms of how cisplatin affected CAR-T cell therapy. Results: Here, we found that pretreatment of low-dose cisplatin was able to enhance the killing capacity of B7H3-targeted CAR-T cells on melanomas both in vitro and in vivo . B7H3 expression was detected in most of the melanoma patient samples and highly expressed on multiple melanoma cell lines. Notably, treatment of cisplatin markedly increased B7H3 expression levels on melanoma cells. In vitro killing assay indicated that treatment of low-dose cisplatin had a positive effect on the efficacy of CAR-T cells by upregulating the expression of target antigen B7H3 on melanoma cells. Furthermore, combination of low-dose cisplatin pretreatment and B7H3-targeted CAR-T cell infusion on immune-deficient NSG mice, which were inoculated with human melanomas (A375-luc), further reduced the tumor size when compared to those without cisplatin pretreatment. Lastly, high-throughput RNA-sequencing analysis was performed on melanoma cells with or without low-dose cisplatin treatment, and we found that the transcriptome profiles of melanoma cells were altered, particularly with increased B7H3 and decreased PD-L1 expressions, after low-dose cisplatin treatment. Further, gene set enrichment analysis (GSEA) indicated that genes related to fundamental cellular biology pathways were significantly reduced in melanoma cells after low-dose cisplatin treatment. Conclusions: Thus, treatment of low-dose cisplatin increased target antigen B7H3 expression on melanoma cells, and further resulted in a more intensive killing activity of B7H3-targeted CAR-T cells both in vitro and in vivo . Taken together, our findings may provide a new strategy to strengthen the therapeutic efficacy of CAR-T cells in treating solid tumors in combination of the use of chemotherapeutic agents.