title: Branched Chain RNA In Situ Hybridization for Androgen Receptor Splice Variant AR-V7 as a Prognostic Biomarker for Metastatic Castration-Sensitive Prostate Cancer.
abstract: OBJECTIVE
  The androgen receptor (AR) mRNA splice variant AR-V7 has emerged as a predictive biomarker for response to AR-targeted therapies. There are currently no commercially available assays to detect AR splice variants. The branched chain RNA in situ hybridization (ISH) platform enables the highly sensitive detection of RNA transcripts in formalin-fixed, paraffin-embedded (FFPE) tissues.
  
  
  METHODS
  We designed a branched chain RNA ISH probe to target the unique cryptic exon CE3 of AR-V7 using multiple tiling probes. This automated ISH assay was applied to tumor tissue from two distinct clinical cohorts that we hypothesized would differ in AR-V7 status.
  
  
  RESULTS
  We detected AR-V7 in all tumor samples from men with metastatic castration-resistant prostate cancer with tissue obtained after disease progression despite at least one subsequent line of hormonal therapy (abiraterone, enzalutamide, or bicalutamide; n = 12). We detected AR-V7 in just one tumor from men who had undergone prostatectomy for localized adenocarcinoma (n = 30; Gleason 4 + 5 = 9 in the AR-V7-positive sample). Given the apparent distinction between the above groups by AR-V7 signal, we analyzed pretreatment AR-V7 status as a predictive and prognostic biomarker in men with treatment-naïve metastatic disease. Patients with metastases but without detectable AR-V7 RNA at baseline had significantly longer overall survival (log-rank P = 0.044) and a trend toward superior progression-free survival (log-rank P = 0.055).
  
  
  CONCLUSIONS
  Within an institutional cohort, the RNA ISH assay identified AR-V7 within FFPE tissue and may have prognostic value in metastatic castration-sensitive prostate cancer. These preliminary findings warrant further study in larger cohorts. Clin Cancer Res; 23(2); 363-9. ©2016 AACR.
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Saylor
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lee
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Kshitij S
authors.initials: KS
authors.lastname: Arora
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Vikram
authors.initials: V
authors.lastname: Deshpande
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Rong
authors.initials: R
authors.lastname: Hu
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Kara
authors.initials: K
authors.lastname: Olivier
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Erika
authors.initials: E
authors.lastname: Meneely
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Miguel N
authors.initials: MN
authors.lastname: Rivera
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: David T
authors.initials: DT
authors.lastname: Ting
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Chin-Lee
authors.initials: CL
authors.lastname: Wu
authors.affiliation: Massachusetts General Hospital Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts. dmiyamoto@mgh.harvard.edu.|Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: David T
authors.initials: DT
authors.lastname: Miyamoto
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D014408:Biomarkers, Tumor / Q000235:genetics*; D045744:Cell Line, Tumor; D018572:Disease-Free Survival; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D060787:Neoplasm Grading; D011379:Prognosis; D011468:Prostatectomy; D064129:Prostatic Neoplasms, Castration-Resistant / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D020033:Protein Isoforms / Q000235:genetics; D015347:RNA Probes / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics; D011944:Receptors, Androgen / Q000235:genetics*
chemical_list: C410798:AR protein, human; D014408:Biomarkers, Tumor; D020033:Protein Isoforms; D015347:RNA Probes; D011944:Receptors, Androgen