Pathway based meta-analysis process (described for scenario I in Tables 2 and 3). The meta-analysis approach involved three major steps: individual analysis of the data sets, meta-analysis at the pathway level, and validation of the signature. Figure 1 represents the process for one scenario. For each scenario, three of the data sets were used to generate the signature and the fourth one was used for testing of the signature. The four data sets were switched around to create four scenarios (see Table 2). The signatures from each scenario were then combined to provide a meta-signature, which was confirmed by the fifth data set.