Prognostic significance of ESR1 gene amplification, mRNA/protein expression and functional profiles in high-risk early breast cancer: a translational study of the Hellenic Cooperative Oncology Group (HeCOG).
BACKGROUND
Discrepant data have been published on the incidence and prognostic significance of ESR1 gene amplification in early breast cancer.


METHODS
Formalin-fixed paraffin-embedded tumor blocks were collected from women with early breast cancer participating in two HeCOG adjuvant trials. Messenger RNA was studied by quantitative PCR, ER protein expression was centrally assessed using immunohistochemistry (IHC) and ESR1 gene copy number by dual fluorescent in situ hybridization probes.


RESULTS
In a total of 1010 women with resected node-positive early breast adenocarcinoma, the tumoral ESR1/CEP6 gene ratio was suggestive of deletion in 159 (15.7%), gene gain in 551 (54.6%) and amplification in 42 cases (4.2%), with only 30 tumors (3%) harboring five or more ESR1 copies. Gene copy number ratio showed a significant, though weak correlation to mRNA and protein expression (Spearman's Rho <0.23, p = 0.01). ESR1 clusters were observed in 9.5% (57 gain, 38 amplification) of cases. In contrast to mRNA and protein expression, which were favorable prognosticators, gene copy number changes did not obtain prognostic significance. When ESR1/CEP6 gene ratio was combined with function (as defined by ER protein and mRNA expression) in a molecular classifier, the Gene Functional profile, it was functional status that impacted on prognosis. In univariate analysis, patients with functional tumors (positive ER protein expression and gene ratio normal or gain/amplification) fared better than those with non-functional tumors with ESR1 gain (HR for relapse or death 0.49-0.64, p = 0.003). Significant interactions were observed between gene gain/amplification and paclitaxel therapy (trend for DFS benefit from paclitaxel only in patients with ESR1 gain/amplification, p = 0.066) and Gene Functional profile with HER2 amplification (Gene Functional profile prognostic only in HER2-normal cases, p = 0.029).


CONCLUSIONS
ESR1 gene deletion and amplification do not constitute per se prognostic markers, instead they can be classified to distinct prognostic groups according to their protein-mediated functional status.
Department of Medical Oncology, Ioannina University Hospital, Ioannina, Greece. gpenther@otenet.gr
George
G
Pentheroudakis
Vassiliki
V
Kotoula
Anastasia G
AG
Eleftheraki
Eleftheria
E
Tsolaki
Ralph M
RM
Wirtz
Konstantine T
KT
Kalogeras
Anna
A
Batistatou
Mattheos
M
Bobos
Meletios A
MA
Dimopoulos
Eleni
E
Timotheadou
Helen
H
Gogas
Christos
C
Christodoulou
Kyriaki
K
Papadopoulou
Ioannis
I
Efstratiou
Chrisoula D
CD
Scopa
Irene
I
Papaspyrou
Dimitrios
D
Vlachodimitropoulos
Helena
H
Linardou
Epaminontas
E
Samantas
Dimitrios
D
Pectasides
Nicholas
N
Pavlidis
George
G
Fountzilas
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D047628:Estrogen Receptor alpha / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005784:Gene Amplification; D018628:Gene Dosage; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
D014408:Biomarkers, Tumor; D047628:Estrogen Receptor alpha; D012333:RNA, Messenger; D018719:Erb-b2 Receptor Tyrosine Kinases; C506487:ESR1 protein, human