Lenvatinib suppress FGF19-FGFR4 signaling to enhance antitumor immune response in gastric cancer.

Background: Fibroblast growth factor receptor (FGFR) 4 is overexpressed in gastric cancer (GC) and is a potential therapeutic target for GC. Since the FGF/FGFR signaling is involved in tumor microenvironment inducing the formation of an immunosuppression, lenvatinib is expected to inhibit FGFR4 leading to reduced tumor PD-L1 levels and regulatory T cell (Treg) infiltration, improving pembrolizumab efficacy. This study explored the background of the molecular mechanisms underlying the therapeutic efficacy of lenvatinib plus pembrolizumab.

Methods: Expression of FGFR4 and its specific ligand FGF19 was assessed by immunohistochemical staining and clinicopathological relevance was also examined. The effect of lenvatinib on FGF19-FGFR4 signaling was evaluated using cellular experiments. Lastly, the expression of FGFR4 on Treg cells was evaluated by immunostaining and flow cytometry. The Cancer Genome Atlas cBioPortal and Gene Expression Omnibus microarray databases were accessed to support these results.

Results: High FGFR4 expression was associated with histological type and venous invasion and predominantly detected in human epidermal growth factor receptor 2 and Epstein-Barr virus-positive GC. Bioinformatics data suggested that FGF19-FGFR4 signaling was activated in GC, and cellular experiments showed that lenvatinib reduced FGFR4 and PD-L1 expression in GC cells. Results of integrating various analyses suggested that FGFR4 did not seem to be enough expressed on Treg cells in GC.

Conclusions: The FGF19-FGFR4 signaling has a pivotal role in gastric tumorigenesis and may be involved in immunosuppression through PD-L1 modification. But, lenvatinib may not regulate immune editing by directly inhibiting FGFR4 on Treg cells.