4060 Background: Anti-EGFR therapy has been used as a standard treatment for metastatic colon cancer, but the innate resistance is still issues of increasing significance. Fibroblast growth factor receptor 4 (FGFR4) plays an important role in cell proliferation, invasion and anti-apoptosis, through the pathway of MAPK-ERK and PI3K-AKT. We investigated potential crosstalk between FGFR4 and EGFR signaling to identify new resistant mechanism of anti-EGFR therapy and how to overcome it in colon cancer. Methods: RNA-Seq was used to identify the associated signal pathway and down targets induced by FGFR4. Molecular studies including RTK array, RT-qPCR, western blotting were performed to validate the interaction between FGFR4 and EGFR signaling in vitro and in vivo. Next, the effect of FGFR4 in cetuximab resistance was investigated in vitro and in colon cancer patients. Results: FGFR4 overexpression in colon cancer cells activates downstream signaling, such as, PI3K/Akt and RAS/RAF/Erk pathway. Gene Ontology (GO) analysis from RNA-seq revealed that differentially expressed genes (DEGs) altered by expression of FGFR4 were related to biological functions, including cell proliferation, epidermal growth factor receptor signaling, NIK/NF-kB signaling, interferon-gamma signaling, wound healing. RT–qRCR showed that FGFR4 promotes the EGFR and ErbB3 by inducing the expression of EGFR ligands such as AREG, BTC, EREG, HBEGF. In vivo tumorigenesis, we found that FGFR4 promotes tumor growth and high expression of AREG in xenograft tumors. FGFR4 expression reduced the sensitivity to cetuximab in colon cancer cells and synergistic effect was shown when treated with FGFR4 inhibitor with cetuximab. A positive correlation between FGFR4 and AREG expression was observed in cancer, but not in normal tissues and high FGFR4 or AREG expression showed significantly inferior overall survival than low expression in patients treated with cetuximab for metastatic colon cancer. Conclusions: We demonstrated a pivotal mechanism of FGFR4 in colon cancer progression and cetuximab resistance through inducing AREG. Our data point to FGFR4 as a new biomarker to predict cetuximab response and dual targeting of FGFR4 and EGFR may be a promising treatment modality for colon cancer.
