title: The impact of co-expression of wild-type EGFR and its ligands determined by immunohistochemistry for response to treatment with cetuximab in patients with metastatic colorectal cancer.
abstract: Anti-EGFR mAbs cetuximab and panitumumab are routinely used for the treatment of patients with KRAS-wild type metastatic colorectal cancer (mCRC). However, in some patients their efficacy remains modest and with no clear association between the EGFR protein expression determined by PharmDx™ kit, and response to anti-EGFR therapies. Therefore, we investigated the relative expression and predictive value of wild-type EGFR (wtEGFR), mutated EGFRvIII and EGFR ligand proteins in mCRC patients treated with cetuximab. The expression levels of wtEGFR, EGFRvIII, and EGFR ligand were determined by immunohistochemistry (IHC) in 60 tumour specimens using specific antibodies. Sections were scored according to the percentage of positive tumour cells, intensity and cellular location of staining, and these were associated with response, overall survival (OS) and progression-free survival (PFS). At cut-off value > 5%, wtEGFR, and EGFRvIII were present in 44%, and 41%, betacellulin (BTC) in 72%, followed by epigen (67%), TGFα (58%), amphiregulin (34%), EGF (31%) of the cases, respectively and 96% of the wtEGFR positive cases had co-expression of at least one ligand. We found a significant association between the expression of wtEGFR and poor response to cetuximab. In addition, the co-expression of wtEGFR with one ligand at a cut-off value of > 5% and > 10% was associated with worse response to cetuximab (P = 0.021, and P = 0.005 respectively). We found a 3-fold and 5-fold increased risk of shorter OS with expression of BTC and epigen. Interestingly, the expression of wtEGFR and its co-expression with one or two ligands was associated with shorter PFS but not with OS. The relative expression of wtEGFR and its competing ligands, which is the target for therapeutic interventions with anti-EGFR antibodies, could serve as a more reliable predictive biomarker of response to therapy with anti-EGFR mAbs in mCRC patients and warrants further investigation in large prospective studies.
authors.affiliation: School of Life Sciences, Pharmacy and Chemistry, Kingston University London, Kingston UK.
authors.forename: Said
authors.initials: S
authors.lastname: Khelwatty
authors.affiliation: School of Life Sciences, Pharmacy and Chemistry, Kingston University London, Kingston UK.|St Luke's Cancer Centre, Royal Surrey County Hospital, Guildford, UK.
authors.forename: Sharadah
authors.initials: S
authors.lastname: Essapen
authors.affiliation: Department of Histopathology, Royal Surrey County Hospital, Guildford, UK.
authors.forename: Izhar
authors.initials: I
authors.lastname: Bagwan
authors.affiliation: Department of Histopathology, Royal Surrey County Hospital, Guildford, UK.
authors.forename: Margaret
authors.initials: M
authors.lastname: Green
authors.affiliation: School of Life Sciences, Pharmacy and Chemistry, Kingston University London, Kingston UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Seddon
authors.affiliation: School of Life Sciences, Pharmacy and Chemistry, Kingston University London, Kingston UK.
authors.forename: Helmout
authors.initials: H
authors.lastname: Modjtahedi
mesh_terms: D000368:Aged; D000074322:Antineoplastic Agents, Immunological / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000068818:Cetuximab / Q000627:therapeutic use*; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D018450:Disease Progression; D018572:Disease-Free Survival; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D008024:Ligands; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D008297:Male; D009154:Mutation; D010766:Phosphorylation; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000074322:Antineoplastic Agents, Immunological; D014408:Biomarkers, Tumor; D008024:Ligands; C410723:epidermal growth factor receptor VIII; C512478:EGFR protein, human; D066246:ErbB Receptors; D000068818:Cetuximab
keywords: EGFR; cetuximab; colorectal cancer; immunohistochemistry; response