Resumen de High early growth response 1 (EGR1) expression correlates with resistance to anti-EGFR treatment in vitro and with poorer outcome in metastatic colorectal cancer patients treated with cetuximab
S. Kumar, J.E Hardingham, T.J. Price, M. Bruhn, Y. Tomita, J. Wrin, A. Swalling, M. Mohammed
Purpose Biomarkers, such as mutant RAS, predict resistance to anti-EGFR therapy in only a proportion of patients, and hence, other predictive biomarkers are needed. The aims were to identify candidate genes upregulated in colorectal cancer cell lines resistant to anti-EGFR monoclonal antibody treatment, to knockdown (KD) these genes in the resistant cell lines to determine if sensitivity to anti-EGFR antibody was restored, and finally to perform a pilot correlative study of EGR1 expression and outcomes in a cohort of metastatic colorectal cancer (mCRC) patients given cetuximab therapy.
Methods Comparative expression array analysis of resistant cell lines (SW48, COLO-320DM, and SNU-C1) vs sensitive cell lines (LIM1215, CaCo2, and SW948) was performed. The highest up-regulated gene in each resistant cell line was knocked down (KD) using RNA interference, and effect on proliferation was assessed with and without anti-EGFR treatment. Expression of the candidate genes in patients’ tumours treated with cetuximab was assessed by immunohistochemistry; survival analyses were performed comparing high vs low expression.
Results Genes significantly upregulated in resistant cell lines were EGR1 (early growth response protein 1), HBEGF (heparin-binding epidermal growth factor-like growth factor), and AKT3 (AKT serine/threonine kinase 3). KD of each gene resulted in the respective cells being more sensitive to anti-EGFR treatment, suggesting that the resistant phenotype was reversed. In the pilot study of mCRC patients treated with cetuximab, both median PFS (1.38 months vs 6.79 months; HR 2.77 95% CI 1.2–19.4) and median OS (2.59 months vs 9.82 months; HR 3.0 95% CI 1.3–23.2) were significantly worse for those patients with high EGR1 expression.
Conclusion High EGR1 expression may be a candidate biomarker of resistance to anti-EGFR therapy.
