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downregulation only means it is decreased, not necessarily absent
(although it can be)
In general according to Dr.Mark Pegram, one of the authors of the original article, all her2+ breast cancers have less ER than their measured ER
% would seem to indicate. This seems to be either because the way we measure ER is not the most accurate (I have posted on this before) or because ER percentage is correct but the hormonal sensitivity (the reason ER is tested) of those tumors that are her2 positive is decreased. A recent article I read said this may be because of AKT activation because of her2 or other downstream signalling systems, and in fact this seems to be a major way that other ER+ tumors escape the effects not only of tamoxifen , but even faslodex.
Here there seems to be a similar effect involving EGFR, her2, MAPK, NFKbeta and ER expression (inverse relationship) but the question seems to be what is the chicken and what is the egg and is there a feedback loop?
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Hybrid Mode
