ATM mutations and E-cadherin expression define sensitivity to EGFR-targeted therapy in colorectal cancer

// Anna-Lena Geisler 1, 2, 3, 4 , Miriam Geisler 1, 2, 3 , Daniel Kottmann 1, 2, 3 , Lisa Lutz 1, 2 , Christiane D. Fichter 1, 2, 3 , Ralph Fritsch 2, 5, 7 , Britta Weddeling 1, 7 , Frank Makowiec 2, 6, 7 , Martin Werner 1, 2, 4, 7 , Silke Lassmann 1, 2, 4, 7, 8 1 Institute of Surgical Pathology, University of Freiburg, Freiburg im Breisgau, Germany 2 Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany 3 Faculty of Biology, University of Freiburg, Freiburg im Breisgau, Germany 4 German Cancer Consortium (DKTK) and German Cancer Research Center (DKFZ), Heidelberg, Germany 5 Department of Internal Medicine, University of Freiburg, Freiburg im Breisgau, Germany 6 Department of Surgery, University of Freiburg, Freiburg im Breisgau, Germany 7 Comprehensive Cancer Center Freiburg, All Medical Center – University of Freiburg, Freiburg im Breisgau, Germany 8 BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg im Breisgau, Germany Correspondence to: Silke Lassmann, email: silke.lassmann@uniklinik-freiburg.de Keywords: anti-EGFR therapy, next generation sequencing, predictive markers, colorectal cancer (CRC), E-cadherin Received: July 11, 2016      Accepted: January 16, 2017      Published: February 09, 2017 ABSTRACT EGFR-targeted therapy is a key treatment approach in patients with RAS wildtype metastatic colorectal cancers (CRC). Still, also RAS wildtype CRC may be resistant to EGFR-targeted therapy, with few predictive markers available for improved stratification of patients. Here, we investigated response of 7 CRC cell lines (Caco-2, DLD1, HCT116, HT29, LS174T, RKO, SW480) to Cetuximab and correlated this to NGS-based mutation profiles, EGFR promoter methylation and EGFR expression status as well as to E-cadherin expression. Moreover, tissue specimens of primary and/or recurrent tumors as well as liver and/or lung metastases of 25 CRC patients having received Cetuximab and/or Panitumumab were examined for the same molecular markers. In vitro and in situ analyses showed that EGFR promoter methylation and EGFR expression as well as the MSI and or CIMP-type status did not guide treatment responses. In fact, EGFR-targeted treatment responses were also observed in RAS exon 2 p.G13 mutated CRC cell lines or CRC cases and were further linked to PIK3CA exon 9 mutations. In contrast, non-response to EGFR-targeted treatment was associated with ATM mutations and low E-cadherin expression. Moreover, down-regulation of E-cadherin by siRNA in otherwise Cetuximab responding E-cadherin positive cells abrogated their response. Hence, we here identify ATM and E-cadherin expression as potential novel supportive predictive markers for EGFR-targeted therapy.