Purpose In patients with advanced colorectal cancer, FOLFIRI is considered as one of the reference first-line treatments. was then constructed using support vector machines. Finally, leave-one-out cross validation was used to estimate the performance and the accuracy of the output class prediction rule. Results We determined a set of 14 predictor genes of response to FOLFIRI. Nine of 9 responders (100% specificity) and 11 of 12 non-responders (92% sensitivity) were correctly classified, for an overall accuracy of 95%. Conclusion After validation Isoliquiritin in an independent cohort of patients, our gene signature could be used as a decision tool to assist oncologists in selecting colorectal cancer patients who could benefit from FOLFIRI chemotherapy, both in the adjuvant and the first-line metastatic setting. study on prediction of response of colon Isoliquiritin cancer cells demonstrated that the measurement of multiple rather than single marker genes resulted in a more accurate assessment of drug response.16 Gene expression profiling has become a strategy to predict clinical outcome or to classify molecular tumor subtypes. Several studies have already been conducted, showing the feasibility of identifying genes involved in the progression and the prognosis of colorectal cancer17C21 or for predicting drug-response in other cancer types, notably in breast cancer.22C24 However, no indication on the possible added value of this approach for predicting drug response in colon cancer has been reported.25 Only a recent study showed that gene expression profiling might contribute to the response prediction of rectal adenocarcinomas to preoperative chemoradiotherapy.26 In this report, our objective was to build a predictor classifier for response to FOLFIRI treatment Isoliquiritin in patients with advanced colorectal using microarray gene expression profiles of primary colon cancer tissue. PATIENTS AND METHODS Patients, and sample collection From January 2000 to June 2004, we enrolled in a prospective study 40 colorectal cancer patients with synchronous and unresectable liver metastases at the Val dAurelle Regional Cancer center. The eligibility criteria for inclusion were: histologically proven adenocarcinoma of the colon; advanced and bidimensionally measurable disease; age 18 to 75 years, WHO performance status of 2 or less. All RHOC patients were chemonaive. Liver metastases were determined as unresectable when there was an impossibility of performing resection of all the lesions with clear margins or when there was an extrahepatic disease involvement. Before receiving any chemotherapy, all patients underwent surgery for primary tumor resection independently of their symptomatic status. R0 resection was achieved in all patients. Colon tumor samples were collected at the time of surgery following a standardized procedure in order to obtain high quality RNA.27 The study was approved by our local ethical committee and all participating patients were informed of the study and had to provide signed written informed consent before enrolment. Chemotherapy Patients were treated with a combination of irinotecan with an LV5FU2 regimen (FOLFIRI), as first-line treatment. Ten patients participated in a multicenter phase II clinical trial aimed at assessing whether increasing the dose of irinotecan (from 180 to 260 mg/m2) in the FOLFIRI regimen would benefit patients with metastatic colorectal cancer. The remaining patients received a FOLFIRI regimen with a standard dose of irinotecan (180 mg/m2). For one patient, intravenous 5-FU was replaced by an oral form of 5-FU (uracil/ftorafur or UFT). Tumor response was evaluated according to WHO recommendations for the evaluation of cancer treatment in solid tumors.28 The size of the metastatic lesions was estimated from bidimensional measurements (the product of the longest diameter and the longest perpendicular diameter) using computed tomography scanning. Patients were evaluated for response before and after every 4 cycles of chemotherapy for a regimen of 3-week cycles and after every 6 cycles of chemotherapy for a regimen of 2-week cycles, to calculate the percent change from baseline. Best observed response was then used to classify patients into two groups. Patients with a decrease 50% of the metastatic lesion were classified as responders (R), and patients with a decrease < 50% or with an increase in size of lesions were classified as non-responders (NR). RNA preparation and assessment of RNA quality All tissue samples were maintained at ?180C (liquid nitrogen) until RNA extraction and were weighed before homogenization. Tissue samples were then disrupted directly into a lysis buffer using Mixer Mill? MM 300 (Qiagen, Valencia, CA). Total RNA was isolated from tissue lysates using the RNeasy? mini Kit (Qiagen), and additional DNAse digestion was performed on all samples during the extraction process (RNase-Free DNase Set? Protocol for DNase treatment on RNeasy? Mini Spin Columns, Qiagen). After each extraction,.