Microarray-Based Prediction of Tumor Response to Neoadjuvant Radiochemotherapy of Patients With Locally Advanced Rectal Cancer  Caroline Rimkus, Jan Friederichs, Anne–laure Boulesteix, Jörg Theisen, Jörg Mages, Karen Becker, Hjalmar Nekarda, Robert Rosenberg, Klaus–Peter Janssen, Jörg Rüdiger Siewert  Clinical Gastroenterology and Hepatology  Volume 6, Issue 1, Pages 53-61 (January 2008) DOI: 10.1016/j.cgh.2007.10.022 Copyright © 2008 AGA Institute Terms and Conditions

Figure 1 Hierarchic clustering of 43 patients with rectal carcinomas based on 50 significantly differentially expressed probe sets representing 42 genes between the subgroup of responders and nonresponders to neoadjuvant chemoradiotherapy. Responders are located on the left side, nonresponders are clustered on the right side. Red represents increased gene expression; green indicates decreased expression. Clinical Gastroenterology and Hepatology 2008 6, 53-61DOI: (10.1016/j.cgh.2007.10.022) Copyright © 2008 AGA Institute Terms and Conditions

Figure 2 Principal component analysis plot after preliminary gene selection (threshold, P < .001) with good discrimination of histopathologic responders (○) and nonresponders (●). Clinical Gastroenterology and Hepatology 2008 6, 53-61DOI: (10.1016/j.cgh.2007.10.022) Copyright © 2008 AGA Institute Terms and Conditions

Figure 3 (A) Receiver operating characteristic curves showing the sensitivity and specificity of response prediction of patients with rectal carcinomas based on 200 random splittings into training and test data sets. Different P value thresholds were used for gene selection: P < .001 (blue), P < .0005 (green), P < .0001 (yellow), reference (pink). (B) Individual measure of the prediction strength in percentage of correct classification for each histopathologic nonresponder (left) and responder (right), obtained with the gene selection threshold of P less than .001. Clinical Gastroenterology and Hepatology 2008 6, 53-61DOI: (10.1016/j.cgh.2007.10.022) Copyright © 2008 AGA Institute Terms and Conditions

Figure 4 Relative expression of caspase-1 determined by quantitative reverse-transcriptase polymerase chain reaction in responders (n = 10) and nonresponders (n = 11), arbitrarily normalized to the expression in normal colon mucosa (expression level = 1.0). Each dot represents one tissue sample, bar = median of expression. The quantitative reverse-transcriptase polymerase chain reaction analysis was performed in duplicate in 3 independent experiments. Median caspase-1 expression in responders was 1.7-fold higher than in nonresponders. However, this difference was not significant. Clinical Gastroenterology and Hepatology 2008 6, 53-61DOI: (10.1016/j.cgh.2007.10.022) Copyright © 2008 AGA Institute Terms and Conditions