PURPOSE:
Quantification of mRNA has historically been
done by reverse transcription polymerase chain reaction (RT-PCR). Recently, a
robust method of detection of mRNA utilizing in situ hybridization has been
described that is linear and shows high specificity with low background. Here
we describe the use of the AQUA method of quantitative immunofluorescence (QIF)
for measuring mRNA in situ using ESR1 (the estrogen receptor alpha gene) in
breast cancer to determine its predictive value compared to Estrogen Receptor α (ER) protein.
METHODS:
Messenger RNA for ER (ESR1) and Ubiquitin C
(UbC) were visualized using RNAscope probes and levels were quantified by quantitative
in situ hybridization (qISH) on two Yale breast cancer cohorts on tissue
microarrays. ESR1 levels were compared to ER protein levels measured by QIF
using the SP1 antibody.
RESULTS:
ESR1 mRNA is reproducibly and specifically
measurable by qISH on tissue collected from 1993 or later. ESR1 levels were
correlated to ER protein levels in a non-linear manner on two Yale cohorts.
High levels of ESR1 were found to be predictive of response to tamoxifin.
CONCLUSION:
Quantification of mRNA using qISH may allow
assessment of large cohorts with minimal formalin fixed, paraffin embedded
tissue. Exploratory data using this method suggests that measurement of ESR1
mRNA levels may be predictive of response to endocrine therapy in a manner that
is different from the predictive value of ER.
Source : Quantitative in situ
measurement of estrogen receptor mRNA predicts response to tamoxifen. Bordeaux
JM, Cheng H, Welsh AW, Haffty BG, Lannin DR, Wu X, Su N, Ma XJ, Luo Y, Rimm DL.
PLoS One. 2012;7(5):e36559.
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