title: High TUBB3 expression, an independent prognostic marker in patients with early non-small cell lung cancer treated by preoperative chemotherapy, is regulated by K-Ras signaling pathway.
abstract: We assessed the prognostic and predictive value of β-tubulin III (TUBB3) expression, as determined by immunohistochemistry, in 412 non-small cell lung cancer (NSCLC) specimens from early-stage patients who received neoadjuvant chemotherapy (paclitaxel- or gemcitabine-based) in a phase III trial (IFCT-0002). We also correlated TUBB3 expression with K-Ras and EGF receptor (EGFR) mutations in a subset of 208 cryopreserved specimens. High TUBB3 protein expression was associated with nonsquamous cell carcinomas (P < 0.001) and K-Ras mutation (P < 0.001). The 127 (30.8%) TUBB3-negative patients derived more than 1 year of overall survival advantage, with more than 84 months median overall survival versus 71.7 months for TUBB3-positive patients [HR, 1.58; 95% confidence interval (CI), 1.11-2.25)]. This prognostic value was confirmed in multivariate analysis (adjusted HR for death, 1.51; 95% CI, 1.04-2.21; P = 0.031) with a bootstrapping validation procedure. TUBB3 expression was associated with nonresponse to chemotherapy (adjusted HR, 1.31; 95% CI, 1.01-1.70; P = 0.044) but had no predictive value (taxane vs. gemcitabine). Taking account of these clinical findings, we further investigated TUBB3 expression in isogenic human bronchial cell lines only differing by K-Ras gene status and assessed the effect of K-Ras short interfering RNA (siRNA) mediated depletion, cell hypoxia, or pharmacologic inhibitors of K-Ras downstream effectors, on TUBB3 protein cell content. siRNA K-Ras knockdown, inhibition of RAF/MEK (MAP-ERK kinase) and phosphoinositide 3-kinase (PI3K)/AKT signaling, and hypoxia were shown to downregulate TUBB3 expression in bronchial cells. This study is the first one to identify K-Ras mutations as determinant of TUBB3 expression, a chemoresistance marker. Our in vitro data deserve studies combining standard chemotherapy with anti-MEK or anti-PI3K drugs in patients with TUBB3-overexpressing tumors.
authors.affiliation: ER3 INSERM Cancers et Populations, CHU de Caen, Caen, France.
authors.forename: Guénaëlle
authors.initials: G
authors.lastname: Levallet
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bergot
authors.forename: Martine
authors.initials: M
authors.lastname: Antoine
authors.forename: Christian
authors.initials: C
authors.lastname: Creveuil
authors.forename: Adriana O
authors.initials: AO
authors.lastname: Santos
authors.forename: Michelle
authors.initials: M
authors.lastname: Beau-Faller
authors.forename: Florence
authors.initials: F
authors.lastname: de Fraipont
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Brambilla
authors.forename: Jérôme
authors.initials: J
authors.lastname: Levallet
authors.forename: Franck
authors.initials: F
authors.lastname: Morin
authors.forename: Virginie
authors.initials: V
authors.lastname: Westeel
authors.forename: Marie
authors.initials: M
authors.lastname: Wislez
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Quoix
authors.forename: Didier
authors.initials: D
authors.lastname: Debieuvre
authors.forename: Fatéméh
authors.initials: F
authors.lastname: Dubois
authors.forename: Isabelle
authors.initials: I
authors.lastname: Rouquette
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Pujol
authors.forename: Denis
authors.initials: D
authors.lastname: Moro-Sibilot
authors.forename: Jacques
authors.initials: J
authors.lastname: Camonis
authors.forename: Gérard
authors.initials: G
authors.lastname: Zalcman
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000378:metabolism* / Q000401:mortality; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D009154:Mutation; D020360:Neoadjuvant Therapy; D011379:Prognosis; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D016019:Survival Analysis; D016896:Treatment Outcome; D014404:Tubulin / Q000235:genetics / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; C498585:TUBB3 protein, human; D014404:Tubulin; D016283:Proto-Oncogene Proteins p21(ras)