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About 80% of breast cancers express estrogen receptor a and or progesterone receptor, biomarkers indicative of hormone dependence, Therapies against ER breast cancers inhibit ER function either by antago nizing ligand binding to ER, downregulating ER or blocking estrogen biosynthesis, However, many tumors exhibit de novo or acquired ARN-509 分子量 resistance to endocrine therapies. Overexpression of the ErbB2 HER2 protooncogene has been shown to promote clinical resistance to antiestro gen therapy, However, 10% of ER breast cancers overexpress HER2, suggesting that, for the majority of ER breast cancers, mechanisms of escape from endo crine therapy remain to be discovered.<br><br> The PI3K pathway has been causally AUY922 分子量 associated with resistance to endocrine therapy, Upon acquisition of hormone independence, ER breast cancer cells increase their dependence on PI3K AKT signaling, Herein we show that inhibition of AKT using the cataly tic inhibitor AZD5363, currently in phase I clinical trials, suppressed hormone independent ER breast can cer growth. However, upregulation of IGF IR InsR and their ligands compensated for AKT inhibition and lim ited the effect of AZD5363. Addition of an IGF IR InsR tyrosine kinase inhibitor enhanced the action of AZD5363 against MCF 7 xenografts in ovariectomized mice devoid of estrogen supplementation, suggesting a novel and testable therapeutic combination for patients with ER breast cancer.<br><br> Methods Cell lines Cell lines were maintained in improved minimum essential medium 10% fetal bovine serum and authenticated by short Alvocidib Flavopiridol tandem repeat profiling using Sanger sequencing, Long term estrogen deprived cells were generated and maintained in phenol red free IMEM with 10% dextran charcoal treated FBS, Immunoblot analysis and RTK arrays Lysates from cells treated with AZD5363, IGF I, IGF II, IGFBP 3, AEW541 or BKM120 were subjected to SDS PAGE, transferred to nitrocellulose and analyzed by immunoblot analysis using antibodies against PAKTS473, PAKTT308, AKT, P PRAS40, P GSK 3a b, P S6S240 244, S6, P IGF IRbY1131 P InsRbY1146, P HER3Y1197, P HER2Y1248, P SrcY416, P FRS2 aY436, EGFR, InsRb, IGF IRb, ERa, HER3, HER4, FGFR2, HER2, PR, IRS 1, and actin, Densitometric analysis was performed using ImageJ.<br><br> Phos pho RTK arrays were performed using the Human Phos pho RTK Array Kit according to the manufacturers protocol, Cell proliferation Cells seeded in triplicate in 12 well plates were treated in 10% DCC FBS AZD5363, selumetinib, fulvestrant, 17b estradiol or AZD9362, AZD9362 is a reversible, ATP competitive small molecule inhibitor of IGF IR and insulin receptor. In isolated enzyme assays, it inhibits the IGF IR enzyme with an IC50 of 14 nM. In cellular assays, the compound prevents autophosphorylation of IGF IR in fibroblasts from IGF IR knockout mice stably transfected with human IGF IR with an IC50 of 48 nM; it inhibits autop hosphorylation of human InsR in CHO T cells with an IC50 of 186 nM.