EREG promotes colorectal cancer progression and immune suppressive microenvironment formation through IL-17A/NF-κB pathway

Colorectal cancer (CRC), as a common malignancy, predominantly exhibits an immune evasion phenotype, making it largely unresponsive to immune checkpoint inhibitors (ICIs). Epiregulin (EREG), a member of the epidermal growth factor family, is frequently overexpressed in CRC, which has been implicated in tumor progression and therapy resistance in various cancers, but its specific role and underlying mechanisms in CRC cell and tumor microenvironment (TME) regulation remain to be elucidated. We determined EREG expression in CRC through The Cancer Genome Atlas (TCGA) database and selected tumor tissues and adjacent non-tumor tissues from 8 treatment-naïve patients with newly diagnosed advanced disease for immunohistochemical analysis(IHC). Lentivirus-mediated RNA interference was employed to establish EREG knockdown CRC cell lines. The effects of EREG silencing on cell proliferation, invasion, colony formation, migration, and apoptosis were evaluated by CCK-8 assay, transwell invasion assay, colony formation assay, wound healing assay, and flow cytometry, respectively. Furthermore, mRNA sequencing (mRNA-seq), enzyme-linked immunosorbent assay (ELISA), and Western blot (WB) analyses were conducted to explore intracellular signaling pathway changes and TME modulation following EREG knockdown. EREG was significantly overexpressed in CRC tissues compared to adjacent normal tissues and correlated closely with intratumoral CD8+T cell infiltration. EREG knockdown significantly inhibited CRC cell proliferation, invasion, clone and migration, while promoting apoptosis. Differentially expressed genes were enriched in the Interleukin-17A/Nuclear Factor Kappa B(IL-17A/NF-κB) signaling pathway. EREG depletion suppressed IL-17A and NF-κB expression, reversible by exogenous IL-17A. Additionally, EREG knockdown increased secretion of chemokines, enhancing CD8+T cell infiltration and remodeling the TME towards an immune-activated state. EREG promotes CRC progression by modulating the IL-17A/NF-κB pathway and maintaining an immunosuppressive TME. Targeting EREG may improve immunotherapy outcomes by transforming cold tumors into hot tumors, providing a promising strategy for CRC treatment.