TY - JOUR

T1 - ESR1 gene status correlates with estrogen receptor protein levels measured by ligand binding assay and immunohistochemistry

AU - Laenkholm, Anne-Vibeke

AU - Knoop, Ann

AU - Ejlertsen, Bent

AU - Rudbeck, Tine

AU - Jensen, Maj-Britt

AU - Müller, Sven

AU - Lykkesfeldt, Anne Elisabeth

AU - Rasmussen, Birgitte Bruun

AU - Nielsen, Kirsten Vang

N1 - Copyright © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

PY - 2012/8

Y1 - 2012/8

N2 - The Estrogen Receptor (ER) is an established predictive marker for the selection of adjuvant endocrine treatment in early breast cancer. During the 1990s Immunohistochemistry (IHC) replaced cytosol based assays for determination of ER status. This study examined the association between ER protein level determined by two different methods and ESR1 gene copy number. From 289 primary high-risk breast cancer patients, randomized in the Danish Breast Cancer Cooperative Group (DBCG) 77C trial, results from cytosolic ER levels were available from ligand binding assays. Archival tumor tissue was retrieved from 257 patients. ESR1/CEN-6 ratio was analyzed successfully by Fluorescence In Situ Hybridization (FISH) in 220 (86%) patients. ESR1 amplification (ESR1/CEN-6 ≥ 2.00) was observed in 23% of the patients and ESR1 deletion (ESR1/CEN-6 < 0.80) was observed in 32%. Further, we identified ESR1 gain (ratio ESR1/CEN-6 from 1.30 to 1.99) in 19% of the patients. A positive correlation of ESR1 FISH with both ER-cytosol and ER IHC was found (p < 0.0001). Amplification and gain of the ESR1 gene are associated with higher ER protein content measured by ligand binding assay and a more intense nuclear staining by IHC compared to tumors with normal ESR1 gene status. Major variations in ER measured by ligand binding assay and IHC are observed within all ESR1 copy number subgroups and other mechanisms than gene copy number seem to contribute to the ER protein content in the tumors.

AB - The Estrogen Receptor (ER) is an established predictive marker for the selection of adjuvant endocrine treatment in early breast cancer. During the 1990s Immunohistochemistry (IHC) replaced cytosol based assays for determination of ER status. This study examined the association between ER protein level determined by two different methods and ESR1 gene copy number. From 289 primary high-risk breast cancer patients, randomized in the Danish Breast Cancer Cooperative Group (DBCG) 77C trial, results from cytosolic ER levels were available from ligand binding assays. Archival tumor tissue was retrieved from 257 patients. ESR1/CEN-6 ratio was analyzed successfully by Fluorescence In Situ Hybridization (FISH) in 220 (86%) patients. ESR1 amplification (ESR1/CEN-6 ≥ 2.00) was observed in 23% of the patients and ESR1 deletion (ESR1/CEN-6 < 0.80) was observed in 32%. Further, we identified ESR1 gain (ratio ESR1/CEN-6 from 1.30 to 1.99) in 19% of the patients. A positive correlation of ESR1 FISH with both ER-cytosol and ER IHC was found (p < 0.0001). Amplification and gain of the ESR1 gene are associated with higher ER protein content measured by ligand binding assay and a more intense nuclear staining by IHC compared to tumors with normal ESR1 gene status. Major variations in ER measured by ligand binding assay and IHC are observed within all ESR1 copy number subgroups and other mechanisms than gene copy number seem to contribute to the ER protein content in the tumors.

KW - Biological Assay/methods

KW - Breast Neoplasms/genetics

KW - Charcoal

KW - Estrogen Receptor alpha/genetics

KW - Female

KW - Gene Dosage/genetics

KW - Genes, Neoplasm/genetics

KW - Humans

KW - Immunohistochemistry/methods

KW - In Situ Hybridization, Fluorescence

KW - Ligands

KW - Neoplasm Invasiveness

KW - Ploidies

U2 - 10.1016/j.molonc.2012.04.003

DO - 10.1016/j.molonc.2012.04.003

M3 - Journal article

C2 - 22626971

VL - 6

SP - 428

EP - 436

JO - Molecular Oncology

JF - Molecular Oncology

SN - 1574-7891

IS - 4

ER -