title: Analysis of ROR1 Protein Expression in Human Cancer and Normal Tissues.
abstract: Purpose:This study examines cell surface ROR1 expression in human tumors and normal tissues. ROR1 is considered a promising target for cancer therapy due to putative tumor-specific expression, and multiple groups are developing antibodies and/or chimeric antigen receptor-modified T cells to target ROR1. On-target, off-tumor toxicity is a challenge for most nonmutated tumor antigens; however, prior studies suggest that ROR1 is absent on most normal tissues.Experimental Design:Our studies show that published antibodies lack sensitivity to detect endogenous levels of cell surface ROR1 by immunohistochemistry (IHC) in formalin-fixed, paraffin-embedded tissues. We developed a ROR1-specific monoclonal antibody (mAb) targeting the carboxy-terminus of ROR1 and evaluated its specificity and sensitivity in IHC.Results:The 6D4 mAb is a sensitive and specific reagent to detect cell surface ROR1 by IHC. The data show that ROR1 is homogenously expressed on a subset of ovarian cancer, triple-negative breast cancer, and lung adenocarcinomas. Contrary to previous findings, we found ROR1 is expressed on several normal tissues, including parathyroid; pancreatic islets; and regions of the esophagus, stomach, and duodenum. The 6D4 mAb recognizes rhesus ROR1, and ROR1 expression was similar in human and macaque tissues, suggesting that the macaque is a suitable model to evaluate safety of ROR1-targeted therapies.Conclusions:ROR1 is a promising immunotherapeutic target in many epithelial tumors; however, high cell surface ROR1 expression in multiple normal tissues raises concerns for on-target off-tumor toxicities. Clinical translation of ROR1-targeted therapies warrants careful monitoring of toxicities to normal organs and may require strategies to ensure patient safety.Clin Cancer Res; 23(12); 3061-71. ©2016 AACR.
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Ashwini
authors.initials: A
authors.lastname: Balakrishnan
authors.affiliation: Experimental Histopathology Shared Resource, Fred Hutchinson Cancer Research Center, Seattle Washington.
authors.forename: Tracy
authors.initials: T
authors.lastname: Goodpaster
authors.affiliation: Experimental Histopathology Shared Resource, Fred Hutchinson Cancer Research Center, Seattle Washington.
authors.forename: Julie
authors.initials: J
authors.lastname: Randolph-Habecker
authors.affiliation: Antibody Development Shared Resource, Fred Hutchinson Cancer Research Center, Seattle Washington.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Hoffstrom
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, Washington.
authors.forename: Florencia G
authors.initials: FG
authors.lastname: Jalikis
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, Washington.
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Koch
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.|Department of Medicine, University of Washington, Seattle, Washington.
authors.forename: Carolina
authors.initials: C
authors.lastname: Berger
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Paula L
authors.initials: PL
authors.lastname: Kosasih
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Anusha
authors.initials: A
authors.lastname: Rajan
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Daniel
authors.initials: D
authors.lastname: Sommermeyer
authors.affiliation: Department of Pathology, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Peggy L
authors.initials: PL
authors.lastname: Porter
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington. sriddell@fredhutch.org.|Department of Medicine, University of Washington, Seattle, Washington.|Institute for Advanced Study, Technical University of Munich, Munich, Germany.
authors.forename: Stanley R
authors.initials: SR
authors.lastname: Riddell
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D002277:Carcinoma / Q000188:drug therapy* / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007167:Immunotherapy; D008297:Male; D058990:Molecular Targeted Therapy; D057050:Receptor Tyrosine Kinase-like Orphan Receptors / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D011948:Receptors, Antigen, T-Cell; C078716:ROR1 protein, human; D057050:Receptor Tyrosine Kinase-like Orphan Receptors