of genes from a gene set to constitute the composite feature. The value of the composite feature is derived from the expression values of the subset of genes as defined in Chuang [*et al.*]{} [@Chuang2007]. In contrast to Chuang [*et al.*]{}, Lee [*et al.*]{}do not exploit the connectivity of the pathway in the construction of the composite features. Lee [*et al.*]{}claim that by using these pathway activities a higher classification performance can be achieved on different cancer types, most notably leukemia, lung and breast cancer. They also report a higher overlap between genes in the top scoring composite features compared to the top scoring single genes.

The underlying assumption in the study by Taylor [*et al.*]{}[@Taylor2009] is that disease-causing perturbations disturb the organization of the interactome, which then has an effect on outcome. They concentrate on highly connected proteins, so-called hubs, as these proteins act as organizers in the molecular network. In contrast to Lee [*et al.*]{}and Chuang [*et al.*]{}, Taylor [*et al.*]{}detect aberrations in the correlation structure between a hub and its immediate interactors. As correlation between two genes cannot be assessed for a single sample, Taylor [*et al.*]{}employ the pairwise expression difference between the hub and each of 