Expression of estrogen receptor alpha exon 5 and 7 deletion variant in human breast cancers.
BACKGROUND
An exon deletion variant of estrogen receptor (ER) mRNA has been reported, as one of the possible mechanisms of loss of ER function.


METHODS
We examined the expression of exons 3, 5, and 7 in ER alpha mRNA and the frequency of exon deletion variant expression in 64 cases of human breast cancers and in 8 non-cancerous breast tissues using reverse transcriptase polymerase chain reaction (RT-PCR).


RESULTS
Approximately the same amount of wild-type (wt) mRNA was detected in all the non-cancerous breast tissues. In cancers, expression of wild-type exon 3 (w3), exon 5 (w5), and exon 7 (w7) was detected in 93.5%, 93.5%, and 91.3% of ER alpha protein (pER) positive cases, respectively, and 27.8%, 38.9%, and 44.4% in negative cases, respectively (p < 0.0001, p = 0.0035, and p = 0.0002). Although the variants for exon 5 (d5) and 7 (d7) were detected in both non-cancerous and cancerous tissues respectively, the variant for exon 3 was not detected at all. Comparatively, the ratio of d5/w5 was significantly higher in pER positive and progesterone receptor protein (pPgR) negative cases.


CONCLUSIONS
We suspect that the exon 5 deletion does not work as a dominant positive.
Omoto
Y
Y
Department of Surgery II, Nagoya City University Medical School, Japan.
Iwase
H
H
Iwata
H
H
Hara
Y
Y
Toyama
T
T
Ando
Y
Y
Kobayashi
S
S
D001940:Breast / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D018270:Carcinoma, Ductal, Breast / Q000378:metabolism*; D047628:Estrogen Receptor alpha; D005091:Exons / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000235:genetics*; D017384:Sequence Deletion
D047628:Estrogen Receptor alpha; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011960:Receptors, Estrogen