Evaluation of oestrogen receptor expression in breast cancer by quantification of mRNA.
OBJECTIVE
cDNA microarrays have subclassified breast carcinomas into molecular subtypes with oestrogen receptor-alpha (ER) gene expression as a main marker. The aim was to compare ER expression in 97 patients with operable breast cancer estimated by real-time reverse transcriptase-polymerase chain reaction (real-time RT-PCR) and by routine immunohistochemistry, and to determine which method was reliable for molecular subtyping in relation to basal-type keratins and HER2 gene expression.


RESULTS
Frozen tumour samples were analysed by real-time RT-PCR for the expression of ER, HER2, keratin 5 and keratin 17 genes. In a group of 27 tumours with a low level of ER mRNA (<1.00), there were eight ER+ cases as assessed by immunohistochemistry, and of 70 cases with a high level of ER mRNA (>or=1.00), 26 were ER- by immunohistochemistry (P = 0.003). Lack of prognostic relevance of ER mRNA level was demonstrated, whereas assessment by immunohistochemistry was related to clinical outcome. Expression of basal keratins and HER2 genes differed significantly between ER+ and ER- tumours based on immunohistochemistry, but not on mRNA level.


CONCLUSIONS
These results throw doubt on the assessment of ER mRNA as a key factor in the molecular distinction between breast tumours.
Potemski
P
P
Department of Chemotherapy, Medical University of Lodz, Copernicus Memorial Hospital, Lodz, Poland. piotrpo@mp.pl
Pluciennik
E
E
Bednarek
A K
AK
Kusinska
R
R
Kubiak
R
R
Kordek
R
R
D001943:Breast Neoplasms / Q000378:metabolism* / Q000401:mortality; D017931:DNA Primers; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D011379:Prognosis; D012333:RNA, Messenger / Q000032:analysis*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis; D011960:Receptors, Estrogen / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity
D017931:DNA Primers; D012333:RNA, Messenger; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen