EPHA2 Is a Predictive Biomarker of Resistance and a Potential Therapeutic Target for Improving Antiepidermal Growth Factor Receptor Therapy in Colorectal Cancer

The EphA2 tyrosine kinase receptor is implicated in tumor progression and targeted therapies resistance. We evaluated EphA2 as a potential resistance marker to the antiepidermal growth factor receptor (EGFR) monoclonal antibody cetuximab in colorectal Cancer. We studied activation of EphA2 in a panel of human colorectal Cancer cell lines sensitive or resistant to anti-EGFR drugs. The in vitro and in vivo effects of ALW-II-41-27 (an EphA2 inhibitor) and/or cetuximab treatment were tested. Formalin-fixed paraffin-embedded tumor specimens from 82 Ras wild-type (WT) metastatic colorectal Cancer patients treated with FOLFIRI + cetuximab as first-line therapy in the CAPRI-GOIM trial were assessed for EphA2 expression by immunohistochemistry and correlated with treatment efficacy. EphA2 was differentially activated in colorectal Cancer cell lines. Combined treatment with ALW-II-41-27 plus cetuximab reverted primary and acquired resistance to cetuximab, causing cell growth inhibition, inducing Apoptosis and cell-cycle G1-G2 arrest. In tumor xenograft models, upon progression to cetuximab, ALW-II-41-27 addition significantly inhibited tumor growth. EphA2 protein expression was detected in 55 of 82 tumor samples, frequently expressed in less-differentiated and left-sided tumors. High levels of EphA2 significantly correlated with worse progression-free survival [8.6 months; confidence interval (CI) 95%, 6.4-10.8; vs. 12.3 months; CI 95%, 10.4-14.2; P = 0.03] and with increased progression rate (29% vs. 9%, P = 0.02). A specific EphA2 inhibitor reverts in vitro and in vivo primary and acquired resistance to anti-EGFR therapy. EphA2 levels are significantly associated with worse outcome in patients treated with FOLFIRI + cetuximab. These results highlight EphA2 as a potential therapeutic target in metastatic colorectal Cancer.