title: Heterogeneous EGFR gene copy number increase is common in colorectal cancer and defines response to anti-EGFR therapy.
abstract: Anti-EGFR therapy is commonly used to treat colorectal cancer (CRC), although only a subset of patients benefit from the treatment. While KRAS mutation predicts non-responsiveness, positive predictive markers are not in clinical practice. We previously showed that immunohistochemistry (IHC)-guided EGFR gene copy number (GCN) analysis may identify CRC patients benefiting from anti-EGFR treatment. Here we tested the predictive value of such analysis in chemorefractory metastatic CRC, elucidated EGFR GCN heterogeneity within the tumors, and evaluated the association between EGFR GCN, KRAS status, and anti-EGFR antibody response in CRC cell lines. The chemorefractory patient cohort consisted of 54 KRAS wild-type (WT) metastatic CRC patients. EGFR GCN status was analyzed by silver in situ hybridization using a cut-off value of 4.0 EGFR gene copies/cell. KRAS-WT and KRAS mutant CRC cell lines with different EGFR GCN were used in in vitro studies. The chemorefractory CRC tumors with EGFR GCN increase (≥4.0) responded better to anti-EGFR therapy than EGFR GCN (<4.0) tumors (clinical benefit, P = 0.0004; PFS, HR = 0.23, 95% CI 0.12-0.46). EGFR GCN counted using EGFR IHC guidance was significantly higher than the value from randomly selected areas verifying intratumoral EGFR GCN heterogeneity. In CRC cell lines, EGFR GCN correlated with EGFR expression. Best anti-EGFR response was seen with KRAS-WT, EGFR GCN = 4 cells and poorest response with KRAS-WT, EGFR GCN = 2 cells. Anti-EGFR response was associated with AKT and ERK1/2 phosphorylation, which was effectively inhibited only in cells with KRAS-WT and increased EGFR GCN. In conclusion, IHC-guided EGFR GCN is a promising predictor of anti-EGFR treatment efficacy in chemorefractory CRC.
authors.affiliation: Department of Oncology and Radiotherapy, Turku University Hospital, Turku, Finland.
authors.forename: Annika
authors.initials: A
authors.lastname: Ålgars
authors.affiliation: Department of Oncology and Radiotherapy, Turku University Hospital, Turku, Finland.
authors.forename: Tuulia
authors.initials: T
authors.lastname: Avoranta
authors.affiliation: Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland; Department of Oncology, University of Helsinki, Helsinki, Finland.
authors.forename: Pia
authors.initials: P
authors.lastname: Österlund
authors.affiliation: Department of Pathology, University of Turku, Turku, Finland; Department of Pathology, Turku University Hospital -Tyks-Sapa, Turku, Finland.
authors.forename: Minnamaija
authors.initials: M
authors.lastname: Lintunen
authors.affiliation: Department of Pathology, University of Turku, Turku, Finland; Department of Pathology, Turku University Hospital -Tyks-Sapa, Turku, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Sundström
authors.affiliation: Department of Pathology, University of Turku, Turku, Finland; Department of Pathology, Turku University Hospital -Tyks-Sapa, Turku, Finland.
authors.forename: Terhi
authors.initials: T
authors.lastname: Jokilehto
authors.affiliation: Division of Pathology and Genetics, Helsinki University Central Hospital - HUSLAB, Helsinki, Finland; Department of Pathology, Haartman Institute and Genome-Scale Biology, Research Programs Unit, University of Helsinki, Helsinki, Finland.
authors.forename: Ari
authors.initials: A
authors.lastname: Ristimäki
authors.affiliation: Department of Oncology and Radiotherapy, Turku University Hospital, Turku, Finland.
authors.forename: Raija
authors.initials: R
authors.lastname: Ristamäki
authors.affiliation: Department of Pathology, University of Turku, Turku, Finland; Department of Pathology, Turku University Hospital -Tyks-Sapa, Turku, Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Carpén
mesh_terms: D000328:Adult; D000368:Aged; D045744:Cell Line, Tumor; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D018572:Disease-Free Survival; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics*; D005260:Female; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic; D018740:Genetic Heterogeneity; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D015203:Reproducibility of Results; D016896:Treatment Outcome; D018631:ras Proteins / Q000235:genetics
chemical_list: C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D066246:ErbB Receptors; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins