ALK and leukemia: Well-known examples of clinically approved biomarkers are the Philadelphia chromosome for treatment of leukemias with imatinib (5), activating mutations in the epidermal growth factor receptor (EGFR) gene for treatment of non-small cell lung cancer (NSCLC) with gefitinib (6), activating mutations in the B-Raf proto-oncogene (BRAF) for treatment of metastatic melanoma with vemurafenib (7), and gene fusions resulting in constitutive activity of the anaplastic lymphoma kinase (ALK) for treatment of NSCLC with crizotinib (8).