EGFR mutations induce the suppression of CD8+ T cell and anti-PD-1 resistance via ERK1/2-p90RSK-TGF-ß axis in non-small cell lung cancer.

ABSTRACT

BACKGROUND: Non-small cell lung cancer (NSCLC) patients with EGFR mutations exhibit an unfavorable response to immune checkpoint inhibitor (ICI) monotherapy, and their tumor microenvironment (TME) is usually immunosuppressed. TGF-ß plays an important role in immunosuppression; however, the effects of TGF-ß on the TME and the efficacy of anti-PD-1 immunotherapy against EGFR-mutated tumors remain unclear. METHODS: Corresponding in vitro studies used the TCGA database, clinical specimens, and self-constructed mouse cell lines with EGFR mutations. We utilized C57BL/6N and humanized M-NSG mouse models bearing EGFR-mutated NSCLC to investigate the effects of TGF-ß on the TME and the combined efficacy of TGF-ß blockade and anti-PD-1 therapy. The changes in immune cells were monitored by flow cytometry. The correlation between TGF-ß and immunotherapy outcomes of EGFR-mutated NSCLC was verified by clinical samples. RESULTS: We identified that TGF-ß was upregulated in EGFR-mutated NSCLC by EGFR activation and subsequent ERK1/2-p90RSK phosphorylation. TGF-ß directly inhibited CD8+ T cell infiltration, proliferation, and cytotoxicity both in vitro and in vivo, but blocking TGF-ß did not suppress the growth of EGFR-mutated tumors in vivo. Anti-TGF-ß antibody combined with anti-PD-1 antibody significantly inhibited the proliferation of recombinant EGFR-mutated tumors in C57BL/6N mice, which was superior to their monotherapy. Mechanistically, the combination of anti-TGF-ß and anti-PD-1 antibodies significantly increased the infiltration of CD8+ T cells and enhanced the anti-tumor function of CD8+ T cells. Moreover, we found that the expression of TGF-ß1 in EGFR-TKI resistant cell lines was significantly higher than that in parental cell lines. The combination of anti-TGF-ß and nivolumab significantly inhibited the proliferation of EGFR-TKI resistant tumors in humanized M-NSG mice and prolonged their survival. CONCLUSIONS: Our results reveal that TGF-ß expression is upregulated in NSCLC with EGFR mutations through the EGFR-ERK1/2-p90RSK signaling pathway. High TGF-ß expression inhibits the infiltration and anti-tumor function of CD8+ T cells, contributing to the "cold" TME of EGFR-mutated tumors. Blocking TGF-ß can reshape the TME and enhance the therapeutic efficacy of anti-PD-1 in EGFR-mutated tumors, which provides a potential combination immunotherapy strategy for advanced NSCLC patients with EGFR mutations.