Table 3 The connectivity of up- and down-regulated proteins. Observed and expected frequencies of pairwise protein interactions, categorised by their expression: N-N (non-expressed protein interacting with non-expressed protein), U-U (up-regulated protein interacting with up-regulated protein), D-D (down-regulated protein interacting with down-regulated protein) and U-D (up-regulated interacting with down-regulated). For the purpose of the classification, up-regulated proteins are those up-regulated more than 20% and down-regulated proteins down-regulated more than 20%. Expected values were calculated based on a random distribution of the expression data on the network (p < 0.001 for a χ²-test).

From: Cluster analysis of networks generated through homology: automatic identification of important protein communities involved in cancer metastasis