title: PTEN loss of expression predicts cetuximab efficacy in metastatic colorectal cancer patients.
abstract: To evaluate whether the epidermal growth factor receptor (EGFR), K-Ras and PTEN, all members of the EGFR signalling pathway, may affect the clinical response in cetuximab-treated metastatic colorectal cancer (mCRC) patients. Twenty-seven cetuximab-treated mCRC patients were evaluated for drug response and investigated for EGFR protein expression and gene status, K-Ras mutational status and PTEN protein expression. Ten patients achieved a partial response (PR) to cetuximab-based therapy. All 27 patients showed EGFR protein overexpression. Epidermal growth factor receptor gene amplification was observed in eight out of 27 (30%) and chromosome 7 marked polysomy in 16 (59%) patients. Partial response was observed in six out of eight patients with EGFR gene amplification, four out of 16 with marked polysomy and none out of three with eusomy (P<0.05). The K-Ras wild-type sequence was observed in 17 patients, and nine of them experienced a PR. Conversely, K-Ras was mutated in 10 cases, of which one patient experienced a PR (P<0.05). The PTEN protein was normally expressed in 16 patients, and 10 of them achieved a PR. In contrast, no benefit was documented in 11 patients with loss of PTEN activity (P<0.001). Patients with EGFR gene amplification or chromosome 7 marked polysomy respond to cetuximab. In addition to K-Ras mutations, we demonstrate for the first time that the loss of PTEN protein expression is associated with nonresponsiveness to cetuximab.
authors.affiliation: Institute of Pathology, via in Selva 24, CH-6600 Locarno, Switzerland. milo.frattini@ti.ch
authors.forename: M
authors.initials: M
authors.lastname: Frattini
authors.forename: P
authors.initials: P
authors.lastname: Saletti
authors.forename: E
authors.initials: E
authors.lastname: Romagnani
authors.forename: V
authors.initials: V
authors.lastname: Martin
authors.forename: F
authors.initials: F
authors.lastname: Molinari
authors.forename: M
authors.initials: M
authors.lastname: Ghisletta
authors.forename: A
authors.initials: A
authors.lastname: Camponovo
authors.forename: L L
authors.initials: LL
authors.lastname: Etienne
authors.forename: F
authors.initials: F
authors.lastname: Cavalli
authors.forename: L
authors.initials: L
authors.lastname: Mazzucchelli
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D000068818:Cetuximab; D002897:Chromosomes, Human, Pair 7; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005260:Female; D005784:Gene Amplification; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins / Q000235:genetics
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D066246:ErbB Receptors; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D000068818:Cetuximab