Figure 1. Identification of feedback combinations that have a significant effect on E-cadherin expression.

To identify the feedback combinations that have a significant effect on E-cadherin expression, we introduced three output indexes, SD, STI and EC50, and quantified the dose-response curves of 32 network topologies for oncogenic stimulation. These are summarized in ‘the feedback combination-output indexes table’ (step 1). The real-valued outputs of each output index are discretized. Then a truth table was constructed from the previous feedback combination table based on the logical representation of each value (step 2). By employing the K-map analysis method, we determined the simplest form of each Boolean function over the 32 feedback combinations and output indexes (step 3&4). Each term of the Boolean function denotes a particular feedback combination that has a significant effect on each output index. In the output indexes of a dose-response curve, RR20, RR50, and RR80 denote 20%, 50%, and 80% of the response range, respectively, where x-axis represents the normalized stimulation (‘0’ denotes low and ‘1’ denotes high) and y-axis represents the expression level of E-cadherin.