# Targeting p-FGFR1Y654 Enhances CD8+ T Cells Infiltration and Overcomes Immunotherapy Resistance in Esophageal Squamous Cell Carcinoma by Regulating the CXCL8–CXCR2 Axis

## TL;DR

This study shows that targeting p-FGFR1Y654 improves immunotherapy effectiveness in esophageal cancer by boosting CD8+ T cell infiltration and reducing immune resistance.

## Contribution

The study identifies p-FGFR1Y654 as a novel target to overcome immunotherapy resistance in ESCC via the CXCL8–CXCR2 axis.

## Key findings

- Inhibition of p-FGFR1Y654 enhances CD8+ T cell infiltration in ESCC by suppressing MDSC recruitment via the CXCL8–CXCR2 axis.
- AZD4547 combined with immunotherapy improves tumor suppression in ESCC models with humanized immune systems.

## Abstract

Background: Esophageal squamous cell carcinoma (ESCC) is a fatal malignant tumor. Several studies have demonstrated that immune checkpoint inhibitors can provide clinical benefits to patients with ESCC. However, the single-agent efficacy of these agents remains limited. Although combination therapies (e.g., radiotherapy, chemotherapy) can help to overcome immunotherapy resistance in ESCC, their severe side effects limit clinical application. This study aimed to explore new resistance mechanisms to immunotherapy in ESCC and identify novel molecular targets to overcome immunotherapy resistance. Methods: We employed immunohistochemistry staining to examine the p-FGFR1Y654 in tumor samples obtained from 103 patients with ESCC, in addition to evaluating CD8+ T cell infiltration. In vitro expression, western blotting, CCK-8, 5-bromo-2′-deoxyuridine incorporation assays, and migration assays were used to confirm the impact of AZD4547 on p-FGFR1Y654 expression and the proliferation and migration in ESCC cell lines. Through RNA sequencing analysis, databases such as the Cancer Genome Atlas (TCGA) and Gene Set Cancer Analysis (GSCA), and the reconstruction of transgenic mice using the humanized immune system, we validated the correlation between the expression of p-FGFR1Y654 and CD8+ T cell infiltration. We also explored how p-FGFR1Y654 recruits myeloid-derived suppressor cells (MDSCs) through the CXCL8–CXCR2 axis to suppress the therapeutic efficacy of immunotherapy in ESCC. Finally, the tumor-suppressive effects of AZD4547 combined with immunotherapy were confirmed in vivo in tumor-bearing mice with a humanized immune system. Results: We found that the inhibition of p-FGFR1Y654 expression in ESCC can enhance CD8+ T cell infiltration by suppressing the CXCL8-–XCR2 recruitment of MDSCs. AZD4547, combined with immunotherapy, further promotes immunotherapeutic efficacy in ESCC. Conclusions: In conclusion, our study presents a promising model for combination therapy in ESCC immunotherapy.