ERBB2 and cancer: Finally, HSP90 is a molecular chaperone whose association is required for the stability and function of multiple mutated, chimeric, and overexpressed signaling proteins that can promote the growth and survival of cancer cells since HSP90 client proteins include mutated p53, Bcr-Abl, Raf-1, Akt, HER2/Neu (ErbB2), and HIF-1α [23].