ERBB2 and neoplasm: Likewise, biological knowledge provides an alternative mapping relation and a related justification for a mapping between 'HER2' and 'tumour aggressiveness', e.g. protein interaction pathways that result in cell proliferation and tumour aggressiveness (see Figure 1, Domain 2), captured, for instance, in GO, UniProt, and KEGG (see http://www.genome.jp/kegg/).