Alonso-Espinaco V, Cuatrecasas M, Alonso V, Escudero P, Marmol M, Horndler C, Ortego J, Gallego R, Codony-Servat J, Garcia-Albeniz X, Jares P, Castells A, Lozano JJ, Rosell R, Maurel J. RAC1b overexpression correlates with poor prognosis in KRAS/BRAF WT metastatic colorectal cancer patients treated with first-line FOLFOX/XELOX chemotherapy. Eur J Cancer. 2014 Jul;50(11):1973-81. doi: 10.1016/j.ejca.2014.04.019.

INTRODUCTION: Chemotherapy is the principal treatment in metastatic colorectal cancer (mCRC) patients. RAC1b, a RAC1 spliced variant, is over-expressed in colorectal cancer (CRC), and impairs apoptosis by activation of nuclear-factor-KB. Since RAC1b has been associated with the BRAF(V600E) mutation, associated with poor prognosis in CRC, we evaluated the role of RAC1b expression as a predictor of chemotherapy efficacy in mCRC.

METHODS: We analysed KRAS and BRAF mutation, microsatellite instability and RAC1b expression in 157 mCRC patients treated with FOLFOX/XELOX in first-line therapy.

RESULTS: KRAS mutations were detected in 46 patients (34%), 10 patients were BRAF mutant (7%) and 79 were WT for both, KRAS and BRAF (59%). RAC1b overexpression was found in 30 patients (19%). In the multivariate analysis, BRAF mutational status was a poor prognostic factor for overall survival (OS); hazard ratio (HR), 2.78 (95% confidence interval (CI), 1.35-5.72; p=0.0057). RAC1b overexpression was a poor survival factor for OS (HR, 2.35; 95% CI, 1.2-4.59; p=0.01) and progression-free survival (PFS) (HR, 2.4; 95% CI, 1.2-4.78; p=0.01) in KRAS/BRAF WT mCRC patients.

CONCLUSIONS: RAC1b overexpression constitutes a marker of poor prognosis in KRAS/BRAF WT mCRC patients treated with first-line FOLFOX/XELOX therapy.

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