For a given protein set X of size jX j, we measure its enrichment in BC (and SP) genes. We compute the statistical significance (pvalue) of observing a given enrichment by measuring the probability that the same enrichment would be observed in a randomly chosen set of jX j proteins in the PPI network. This probability is computed as follows by using the following notation: the total number of proteins in the network is jV j; the number of proteins in set X is jX j; the number of proteins in set X that are BC (SP) genes is jf j; there are jFj proteins in the entire PPI network that are BC (SP) genes. Then, the enrichment is jf j=jX j, and the p-value, i.e., the probability of observing the same or higher enrichment purely by chance, is obtained by using the hypergeometric distribution formula for sampling without replacement: