Effects of anlotinib combined with camrelizumab and chemotherapy as first-line treatment for advanced esophageal squamous cell carcinoma on tumor immune microenvironment.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) presents significant therapeutic challenges due to limited treatment options. While immune checkpoint inhibitors (ICIs) combined with chemotherapy have demonstrated efficacy, variable response rates underscore the necessity for enhanced therapeutic approaches. Anlotinib, a multi-target tyrosine kinase inhibitor, has shown synergistic effects with ICIs in clinical practice. However, its influence on the tumor immune microenvironment (TIME) in ESCC requires further elucidation. This study aimed to investigate anlotinib's effects on the TIME. METHODS: In our phase II trial (NCT04471480), we analyzed 8 advanced ESCC patients who achieved operability following treatment with anlotinib, camrelizumab, and chemotherapy (TCAC group). A control group (TCC group) comprised 8 patients from a separate neoadjuvant trial who received identical treatment, excluding anlotinib. Tumor-infiltrating immune cell populations (CD4(+), CD8(+), CD20(+), CD68(+), FOXP3(+)) were evaluated using multiplex immunofluorescence. Additional mechanistic insights were obtained through RNA sequencing (RNA-seq) and enzyme-linked immunosorbent assay (ELISA). RESULTS: Baseline immune cell profiles showed no significant intergroup differences. Post-treatment analysis revealed the TCAC group had significantly elevated CD8(+) cell proportions and reduced FOXP3(+) cell proportions compared to controls (P<0.05). Within the TCAC cohort, pretreatment immune cell distributions were comparable between pathological complete response (pCR) and non-pCR patients. However, post-treatment pCR patients demonstrated significantly higher CD8(+) and lower FOXP3(+) cell levels versus non-pCR cases (P<0.05). RNA-seq and ELISA analyses suggested anlotinib's potential to enhance the immune microenvironment through C-C motif chemokine ligand 5 (CCL5) upregulation. CONCLUSIONS: The combination of anlotinib with camrelizumab and chemotherapy appears to modify the ESCC immune microenvironment by promoting cytotoxic CD8(+) T cell infiltration while suppressing FOXP3(+) regulatory T cells, possibly mediated through CCL5 induction. These results warrant further investigation of anlotinib's immunomodulatory potential in ESCC combination therapies.