title: Pulmonary inflammatory myofibroblastic tumor expressing a novel fusion, PPFIBP1-ALK: reappraisal of anti-ALK immunohistochemistry as a tool for novel ALK fusion identification.
abstract: OBJECTIVE
  The anaplastic lymphoma kinase (ALK) inhibitor crizotinib has been used in patients with lung cancer or inflammatory myofibroblastic tumor (IMT), both types harboring ALK fusions. However, detection of some ALK fusions is problematic with conventional anti-ALK immunohistochemistry because of their low expression. By using sensitive immunohistochemistry, therefore, we reassessed "ALK-negative" IMT cases defined with conventional immunohistochemistry (approximately 50% of all examined cases).
  
  
  METHODS
  Two cases of ALK-negative IMT defined with conventional anti-ALK immunohistochemistry were further analyzed with sensitive immunohistochemistry [the intercalated antibody-enhanced polymer (iAEP) method].
  
  
  RESULTS
  The two "ALK-negative" IMTs were found positive for anti-ALK immunohistochemistry with the iAEP method. 5'-rapid amplification of cDNA ends identified a novel partner of ALK fusion, protein-tyrosine phosphatase, receptor-type, F polypeptide-interacting protein-binding protein 1 (PPFIBP1) in one case. The presence of PPFIBP1-ALK fusion was confirmed with reverse transcriptase PCR, genomic PCR, and FISH. We confirmed the transforming activities of PPFIBP1-ALK with a focus formation assay and an in vivo tumorigenicity assay by using 3T3 fibroblasts infected with a recombinant retrovirus encoding PPFIBP1-ALK. Surprisingly, the fusion was also detected by FISH in the other case.
  
  
  CONCLUSIONS
  Sensitive immunohistochemical methods such as iAEP will broaden the potential value of immunohistochemistry. The current ALK positivity rate in IMT should be reassessed with a more highly sensitive method such as iAEP to accurately identify those patients who might benefit from ALK-inhibitor therapies. Novel ALK fusions are being identified in various tumors in addition to IMT, and thus a reassessment of other "ALK-negative" cancers may be required in the forthcoming era of ALK-inhibitor therapy.
authors.affiliation: Pathology Project for Molecular Targets, Division of Pathology, Thoracic Center, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan. kentakeuchi-tky@umin.net
authors.forename: Kengo
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Manabu
authors.initials: M
authors.lastname: Soda
authors.forename: Yuki
authors.initials: Y
authors.lastname: Togashi
authors.forename: Emiko
authors.initials: E
authors.lastname: Sugawara
authors.forename: Satoko
authors.initials: S
authors.lastname: Hatano
authors.forename: Reimi
authors.initials: R
authors.lastname: Asaka
authors.forename: Sakae
authors.initials: S
authors.lastname: Okumura
authors.forename: Ken
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mano
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ishikawa
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000328:Adult; D000077548:Anaplastic Lymphoma Kinase; D000818:Animals; D000906:Antibodies / Q000378:metabolism; D001483:Base Sequence; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006104:Granuloma, Plasma Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D058628:Myofibroblasts / Q000378:metabolism / Q000473:pathology; D015514:Oncogene Proteins, Fusion / Q000032:analysis / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014183:Transplantation, Heterologous
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies; D015514:Oncogene Proteins, Fusion; C449803:PPFIBP1 protein, human; C000626173:ALK protein, human; C000626174:Alk protein, mouse; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases