EML4 and cancer: Heat shock protein 90 (Hsp90) is a molecular chaperone that plays a central role in regulating the correct folding, stability, and function of numerous “client proteins,” including human epidermal growth factor receptor 2 (HER2), BRAF, mutant EGFR, and EML4-ALK, Bcr-Abl, Raf-1, which are required for cancer cell survival [15, 16, 17, 18].