This study demonstrates how the potentiating effects of E-2 on insulin sign
aling in endoplasmic reticulum-positive breast cancer cells are consequent
to an enhanced IRS-1 expression. It induces an increase of both PI-3K/AKT a
nd ERK1/2 activities. A direct action of E-2 in the regulating mouse IRS-1
gene is also investigated in both Chinese hamster ovary and MCF-7 cells tha
t are transfected with mouse IRS-1 regulatory sequences. The authors have r
eported, for the first time, how E-2 induction of ERS-1 mRNA was correlated
with a direct positive regulatory role Of E-2 on the IRS-1 promoter. This
effect seems to be not strictly related to the cell type. (C) 2001 Academic
Press.