Molecules such as Her2, EGFR, VEGFR, ALK, AKT, p52, cyclin D1, Met, Cdk4, HIF-1α or MMP2 which play important roles as oncogenes and are involved in essential pathways of cancer are described to be client proteins of HSP90 (for review [10,13]). The gene discussed is ERBB2; the disease is cancer.