ERBB2 and cancer: Among the more than 200 HSP90 clients are many proteins required for tumor growth, including primary cancer “drivers” such as BCR-ABL1, wildtype ERBB2 and mutant forms of EGFR, ERBB2, FLT3, JAK2 and KIT, as well as critical downstream effectors of these oncoproteins such as AKT1 and RAF1 [3].