title: Analytic validation of a clinical-grade PTEN immunohistochemistry assay in prostate cancer by comparison with PTEN FISH.
abstract: PTEN loss is a promising prognostic and predictive biomarker in prostate cancer. Because it occurs most commonly via PTEN gene deletion, we developed a clinical-grade, automated, and inexpensive immunohistochemical assay to detect PTEN loss. We studied the sensitivity and specificity of PTEN immunohistochemistry relative to four-color fluorescence in situ hybridization (FISH) for detection of PTEN gene deletion in a multi-institutional cohort of 731 primary prostate tumors. Intact PTEN immunostaining was 91% specific for the absence of PTEN gene deletion (549/602 tumors with two copies of the PTEN gene by FISH showed intact expression of PTEN by immunohistochemistry) and 97% sensitive for the presence of homozygous PTEN gene deletion (absent PTEN protein expression by immunohistochemistry in 65/67 tumors with homozygous deletion). PTEN immunohistochemistry was 65% sensitive for the presence of hemizygous PTEN gene deletion, with protein loss in 40/62 hemizygous tumors. We reviewed the 53 cases where immunohistochemistry showed PTEN protein loss and FISH showed two intact copies of the PTEN gene. On re-review, there was ambiguous immunohistochemistry loss in 6% (3/53) and failure to analyze the same tumor area by both methods in 34% (18/53). Of the remaining discordant cases, 41% (13/32) revealed hemizygous (n=8) or homozygous (n=5) PTEN gene deletion that was focal in most cases (11/13). The remaining 19 cases had two copies of the PTEN gene detected by FISH, representing truly discordant cases. Our automated PTEN immunohistochemistry assay is a sensitive method for detection of homozygous PTEN gene deletions. Immunohistochemistry screening is particularly useful to identify cases with heterogeneous PTEN gene deletion in a subset of tumor glands. Mutations, small insertions, or deletions and/or epigenetic or microRNA-mediated mechanisms may lead to PTEN protein loss in tumors with normal or hemizygous PTEN gene copy number.
authors.affiliation: Pathology, Johns Hopkins School of Medicine, Baltimore, MD, USA.|Oncology, Johns Hopkins School of Medicine, Baltimore, MD, USA.
authors.forename: Tamara L
authors.initials: TL
authors.lastname: Lotan
authors.affiliation: MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.affiliation: Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada.
authors.forename: Olga
authors.initials: O
authors.lastname: Ludkovski
authors.affiliation: Pathology, Johns Hopkins School of Medicine, Baltimore, MD, USA.
authors.forename: Carlos L
authors.initials: CL
authors.lastname: Morais
authors.affiliation: Pathology, Johns Hopkins School of Medicine, Baltimore, MD, USA.
authors.forename: Liana B
authors.initials: LB
authors.lastname: Guedes
authors.affiliation: Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada.
authors.forename: Tamara
authors.initials: T
authors.lastname: Jamaspishvili
authors.affiliation: Pathology, UCSF, San Francisco, CA, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Lopez
authors.affiliation: Canary Foundation, Palo Alto, CA, USA.
authors.forename: Sarah T
authors.initials: ST
authors.lastname: Hawley
authors.affiliation: MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Ziding
authors.initials: Z
authors.lastname: Feng
authors.affiliation: Vancouver Prostate Centre, Vancouver, BC, Canada.
authors.forename: Ladan
authors.initials: L
authors.lastname: Fazli
authors.affiliation: Vancouver Prostate Centre, Vancouver, BC, Canada.
authors.forename: Antonio
authors.initials: A
authors.lastname: Hurtado-Coll
authors.affiliation: Pathology, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Jesse K
authors.initials: JK
authors.lastname: McKenney
authors.affiliation: Pathology, UCSF, San Francisco, CA, USA.|Urology, UCSF, San Francisco, CA, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Simko
authors.affiliation: Urology, UCSF, San Francisco, CA, USA.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Carroll
authors.affiliation: Canary Foundation, Palo Alto, CA, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Gleave
authors.affiliation: Urology, University of Washington, Seattle, WA, USA.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Lin
authors.affiliation: Urology, University of Washington, Seattle, WA, USA.|Oncology, University of Washington, Seattle, WA, USA.|Pathology, University of Washington, Seattle, WA, USA.|Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Nelson
authors.affiliation: Urology, UTHSCSA, San Antonio, TX, USA.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Thompson
authors.affiliation: Pathology, University of Washington, Seattle, WA, USA.
authors.forename: Lawrence D
authors.initials: LD
authors.lastname: True
authors.affiliation: Urology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Brooks
authors.affiliation: Urology, Eastern Virginia Medical School, Norfolk, VA, USA.
authors.forename: Raymond
authors.initials: R
authors.lastname: Lance
authors.affiliation: Urology, Eastern Virginia Medical School, Norfolk, VA, USA.|Pathology, Eastern Virginia Medical School, Norfolk, VA, USA.
authors.forename: Dean
authors.initials: D
authors.lastname: Troyer
authors.affiliation: Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada.|Department of Pathology, University of Sao Paulo Medical School, São Paulo, Brazil.
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Squire
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics*; D001955:British Columbia; D017353:Gene Deletion; D018628:Gene Dosage; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D051059:PTEN Phosphohydrolase / Q000032:analysis* / Q000235:genetics*; D010641:Phenotype; D011237:Predictive Value of Tests; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D015203:Reproducibility of Results; D012189:Retrospective Studies; D046888:Tissue Array Analysis; D014481:United States
chemical_list: D014408:Biomarkers, Tumor; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human