title: Differential protein stability and clinical responses of EML4-ALK fusion variants to various ALK inhibitors in advanced ALK-rearranged non-small cell lung cancer.
abstract: Anaplastic lymphoma kinase (ALK) inhibition using crizotinib has become the standard of care in advanced ALK-rearranged non-small cell lung cancer (NSCLC), but the treatment outcomes and duration of response vary widely. Echinoderm microtubule-associated protein-like 4 (EML4)-ALK is the most common translocation, and the fusion variants show different sensitivity to crizotinib in vitro. However, there are only limited data on the specific EML4-ALK variants and clinical responses of patients to various ALK inhibitors.
  
  
  
  By multiplex reverse-transcriptase PCR, which detects 12 variants of known EML4-ALK rearrangements, we retrospectively determined ALK fusion variants in 54 advanced ALK rearrangement-positive NSCLCs. We subdivided the patients into two groups (variants 1/2/others and variants 3a/b) by protein stability and evaluated correlations of the variant status with clinical responses to crizotinib, alectinib, or ceritinib. Moreover, we established the EML4-ALK variant-expressing system and analyzed patterns of sensitivity of the variants to ALK inhibitors.
  
  
  
  Of the 54 tumors analyzed, EML4-ALK variants 3a/b (44.4%) was the most common type, followed by variants 1 (33.3%) and 2 (11.1%). The 2-year progression-free survival (PFS) rate was 76.0% [95% confidence interval (CI) 56.8-100] in group EML4-ALK variants 1/2/others versus 26.4% (95% CI 10.5-66.6) in group variants 3a/b (P = 0.034) among crizotinib-treated patients. Meanwhile, the 2-year PFS rate was 69.0% (95% CI 49.9-95.4) in group variants 1/2/others versus 32.7% (95% CI 15.6-68.4) in group variants 3a/b (P = 0.108) among all crizotinib-, alectinib-, and ceritinib-treated patients. Variant 3a- or 5a-harboring cells were resistant to ALK inhibitors with >10-fold higher half maximal inhibitory concentration in vitro.
  
  
  
  Our findings show that group EML4-ALK variants 3a/b may be a major source of ALK inhibitor resistance in the clinic. The variant-specific genotype of the EML4-ALK fusion allows for more precise stratification of patients with advanced NSCLC.
authors.affiliation: Department of Pathology, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Gyeonggi-do, South Korea.
authors.forename: C G
authors.initials: CG
authors.lastname: Woo
authors.affiliation: Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
authors.forename: S
authors.initials: S
authors.lastname: Seo
authors.affiliation: Department of Surgery, Seoul National University College of Medicine, Daehak-ro 101, Jongno-gu, Seoul, South Korea.
authors.forename: S W
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Molecular Imaging Research Center, Korea Institute of Radiological and Medical Sciences, Seoul 01812, South Korea.
authors.forename: S J
authors.initials: SJ
authors.lastname: Jang
authors.affiliation: Department of Biomedical Science, College of Life Science, CHA University, Seoul, South Korea.
authors.forename: K S
authors.initials: KS
authors.lastname: Park
authors.affiliation: Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
authors.forename: J Y
authors.initials: JY
authors.lastname: Song
authors.affiliation: Division of Surgical Oncology, Department of Surgery, City of Hope, Duarte, California, USA.
authors.forename: B
authors.initials: B
authors.lastname: Lee
authors.affiliation: Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
authors.forename: M W
authors.initials: MW
authors.lastname: Richards
authors.affiliation: Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
authors.forename: R
authors.initials: R
authors.lastname: Bayliss
authors.affiliation: Division of Medical Oncology, Department of Internal Medicine, Korea University College of Medicine, Korea University, Seoul 152-703, South Korea.
authors.forename: D H
authors.initials: DH
authors.lastname: Lee
authors.affiliation: epartment of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
authors.forename: J
authors.initials: J
authors.lastname: Choi
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D002227:Carbazoles / Q000627:therapeutic use; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics*; D000077547:Crizotinib; D018572:Disease-Free Survival; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D060885:Multiplex Polymerase Chain Reaction; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D010880:Piperidines / Q000627:therapeutic use; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D055550:Protein Stability; D011720:Pyrazoles / Q000627:therapeutic use; D011725:Pyridines / Q000627:therapeutic use; D011743:Pyrimidines / Q000627:therapeutic use; D012189:Retrospective Studies; D013450:Sulfones / Q000627:therapeutic use
chemical_list: D000970:Antineoplastic Agents; D002227:Carbazoles; C522504:EML4-ALK fusion protein, human; D015514:Oncogene Proteins, Fusion; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; D011725:Pyridines; D011743:Pyrimidines; D013450:Sulfones; D000077547:Crizotinib; C586847:ceritinib; C582670:alectinib
keywords: ALK inhibitor; ALK translocation.; EML4-ALK; crizotinib; non-small cell lung cancer