ALK fusion proteins are HSP90 clients, and it has already been shown in preclinical and clinical studies that HSP90 inhibition is highly effective against EML4-ALK-positive lung cancer as well as against ALK-positive ALCL cells in vitro (Bonvini et al. 2002; Chen et al. 2010; Katayama et al. 2011; Li et al. 2012; Sequist et al. 2010). This evidence concerns the gene EML4 and lung cancer.