title: Immunohistochemical detection of ROS1 is useful for identifying ROS1 rearrangements in lung cancers.
abstract: The recent discovery and characterization of an oncogenic ROS1 gene fusion in a subset of lung cancers has raised significant clinical interest because small molecule inhibitors may be effective to these tumors. As lung cancers with ROS1 rearrangements comprise only 1-3% of lung adenocarcinomas, patients with such tumors must be identified to gain optimal benefit from molecular therapy. Recently, immunohistochemical analyses using a novel anti-ROS1 rabbit monoclonal antibody (D4D6) have shown promise for accurate identification of ROS1-rearranged cancers. To validate this finding, we compared the immunostaining results of tissue microarrays (TMAs) containing 17 ROS1-rearranged and 253 ROS1-non-rearranged lung carcinomas. All 17 ROS1-rearranged cancers showed ROS1 immunoreactivity mostly in a diffuse and moderate-to-strong manner with an H-score range of 5-300 (median, 260). In contrast, 69% of ROS1-non-rearranged cancers lacked detectable immunoreactivity, whereas the remaining 31% showed reactivity mainly in a weak or focal manner. The H-score for the entire ROS1-non-rearranged group ranged from 0 to 240 (median, 0). The difference in H-score between the two cohorts was statistically significant, and the H-score cutoff (≥150) allowed optimal discrimination (94% sensitivity and 98% specificity). Similar but slightly less-specific performance was achieved using the extent of diffuse (≥75%) staining or ≥2+ staining intensity as cutoffs. CD74-ROS1 and EZR-ROS1 fusions were significantly associated with at least focal globular immunoreactivity and plasma membranous accentuation, respectively, and these patterns were specific to ROS1-rearranged cases. Although full-length ROS1 is expressed in some ROS1-non-rearranged cases, we showed that establishment of an optimal set of interpretative criteria makes ROS1 immunohistochemistry a valuable method to rapidly and accurately screen lung cancer patients for appropriate molecular therapy.
authors.affiliation: Division of Pathology and Clinical Laboratories, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshida
authors.affiliation: Division of Pathology and Clinical Laboratories, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuta
authors.affiliation: Division of Pathology and Clinical Laboratories, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Wakai
authors.affiliation: Division of Cancer Genomics, Center for Medical Genomics, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Arai
authors.affiliation: Division of Thoracic Surgery, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Asamura
authors.affiliation: Division of Cancer Genomics, Center for Medical Genomics, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Shibata
authors.affiliation: Division of Pathology and Clinical Laboratories, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Koh
authors.initials: K
authors.lastname: Furuta
authors.affiliation: Division of Genome Biology, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kohno
authors.affiliation: Division of Pathology and Clinical Laboratories, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Ryoji
authors.initials: R
authors.lastname: Kushima
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D015321:Gene Rearrangement; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D046888:Tissue Array Analysis
chemical_list: D014408:Biomarkers, Tumor; D011518:Proto-Oncogene Proteins; D011505:Protein-Tyrosine Kinases; C062333:ROS1 protein, human