ErbB4/KITENIN-Mediated Signaling is Activated in Cetuximab-Resistant Colorectal Cancer Cells

ErbB4/KITENIN signaling plays a role in epidermal growth factor receptor (EGFR)-independent EGF pathways mediating the invasiveness and tumorigenesis of colorectal cancer cells. However, whether alterations in ErbB4/KITENIN signaling play a role in the resistance to anti-EGFR therapy remains unclear. Here, we established cetuximab-resistant DLD1 and HT29 cells, and analyzed changes in ErbB4/KITENIN signaling. c-Jun, a final effector in ErbB4/KITENIN-mediated signaling, was upregulated, whereas KITENIN levels remained constant in both cetuximab-resistant cell lines. The phosphorylation of EGFR and ErbB4 was increased in cetuximab-resistant cells, suggesting that ErbB4/KITENIN signaling contributed to the acquisition of cetuximab resistance in the cells. Silencing of KITENIN and/or ErbB4 increased cetuximab sensitivity in cetuximab-resistant cells. This study is the first to report the activation of ErbB4/KITENIN-mediated signaling in cetuximab-resistant colorectal cancer cells and the potential clinical application of ErbB4/KITENIN-targeting therapy for overcoming anti-EGFR resistance.