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Articles by I Barone
Total Records ( 2 ) for I Barone
  I Barone , Y Cui , M. H Herynk , A Corona Rodriguez , C Giordano , J Selever , A Beyer , S Ando and S. A.W. Fuqua
 

Aromatase inhibitors (AI) are rapidly becoming the first choice for hormonal treatment of estrogen receptor- (ER)–positive breast cancer in postmenopausal women. However, de novo and acquired resistance frequently occurs. We have previously identified a lysine to arginine transition at residue 303 (K303R) in ER in premalignant breast lesions and invasive breast cancers, which confers estrogen hypersensitivity and resistance to tamoxifen treatment. Thus, we questioned whether resistance to AIs could arise in breast cancer cells expressing the ER mutation. As preclinical models to directly test this possibility, we generated K303R-overexpressing MCF-7 cells stably transfected with an aromatase expression vector. Cells were stimulated with the aromatase substrate, androstenedione, with or without the AI anastrozole (Ana). We found that Ana decreased androstenedione-stimulated growth of wild-type cells, whereas K303R-expressing cells were resistant to the inhibitory effect of Ana on growth. We propose that a mechanism of resistance involves an increased binding between the mutant receptor and the p85 regulatory subunit of phosphatidylinositol-3-OH kinase (PI3K), leading to increased PI3K activity and activation of protein kinase B/Akt survival pathways. Inhibition of the selective "addiction" to the PI3K/Akt pathway reversed AI resistance associated with expression of the mutant receptor. Our findings suggest that the K303R ER mutation might be a new predictive marker of response to AIs in mutation-positive breast tumors, and that targeting the PI3K/Akt pathway may be a useful strategy for treating patients with tumors resistant to hormone therapy. [Cancer Res 2009;69(11):4724–32]

  S Catalano , I Barone , C Giordano , P Rizza , H Qi , G Gu , R Malivindi , D Bonofiglio and S. Ando
 

In situ estrogen production by aromatase conversion from androgens plays an important role in breast tumor promotion. Here, we show that 17β-estradiol (E2) can rapidly enhance aromatase enzymatic activity through an increase of aromatase protein phosphorylation in breast cancer cell lines. In vivo labeling experiments and site-directed mutagenesis studies demonstrated that phosphorylation of the 361-tyrosine residue is crucial in the up-regulation of aromatase activity under E2 exposure. Our results demonstrated a direct involvement of nonreceptor tyrosine-kinase c-Src in E2-stimulated aromatase activity because inhibition of its signaling abrogated the up-regulatory effects induced by E2 on aromatase activity as well as phosphorylation of aromatase protein. In addition, from our data it emerges that aromatase is a target of cross talk between growth factor receptors and estrogen receptor signaling. These findings show, for the first time, that tyrosine phosphorylation processes play a key role in the rapid changes induced by E2 in aromatase enzymatic activity, revealing the existence of a short nongenomic autocrine loop between E2 and aromatase in breast cancer cells.

 
 
 
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