Browsing by Subject "endocrine resistance"

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    Obesity Enhances Nongenomic Estrogen Receptor Crosstalk with the PI3K/Akt and MAPK Pathways to Promote in Vitro Measures of Breast Cancer Progression
    (2013) Bowers, Laura W.; Cavazos, David A.; Maximo, Ilane X. F.; Brenner, Andrew J.; Hursting, Stephen D.; deGraffenried, Linda A.; Bowers, Laura W.; Cavazos, David A.; Maximo, Ilane X. F.; Brenner, Andrew J.; Hursting, Stephen D.; deGraffenried, Linda A.
    Epidemiological and clinical studies indicate that obesity is associated with a worse postmenopausal breast cancer prognosis and an increased risk of endocrine therapy resistance. However, the mechanisms mediating these effects remain poorly understood. Here we investigate the molecular pathways by which obesity-associated circulating factors in the blood enhance estrogen receptor alpha (ER alpha) positive breast cancer cell viability and growth. Methods: Blood serum was collected from postmenopausal breast cancer patients and pooled by body mass index (BMI) category (Control: 18.5 to 24.9 kg/m(2); Obese: >= 30.0 kg/m(2)). The effects of patient sera on MCF-7 and T47D breast cancer cell viability and growth were examined by MTT and colony formation assays, respectively. Insulin-like growth factor receptor 1(IGF-1R), Akt, and ERK1/2 activation and genomic ER alpha activity were assessed to determine their possible contribution to obese patient sera-induced cell viability and growth. To further define the relative contribution of these signaling pathways, cells grown in patient sera were treated with various combinations of ER alpha, PI3K/Akt and MAPK targeted therapies. Comparisons between cells exposed to different experimental conditions were made using one-way analysis of variance (ANOVA) and Student's t test. Results: Cells grown in media supplemented with obese patient sera displayed greater cell viability and growth as well as IGF-1R, Akt and ERK1/2 activation relative to control sera. Despite the lack of a significant difference in genomic ER alpha activity following growth in obese versus control patient sera, we observed a dramatic reduction in cell viability and growth after concurrent inhibition of the ER alpha and PI3K/Akt signaling pathways. Further, we demonstrated that ER alpha inhibition was sufficient to attenuate obese serum-induced Akt and ERK1/2 activation. Together, these data suggest that obesity promotes greater ER alpha positive breast cancer cell viability and growth through enhanced crosstalk between nongenomic ER alpha signaling and the PI3K/Akt and MAPK pathways. Conclusions: Circulating factors in the serum of obese postmenopausal women stimulate ER alpha positive breast cancer cell viability and growth by facilitating non-genomic ER alpha crosstalk with the PI3K/Akt and MAPK signaling pathways. These findings provide valuable insight into one mechanism by which obesity may promote ER alpha positive postmenopausal breast cancer progression and endocrine therapy resistance.
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    Targeting Cholesterol-Rich Microdomains to Circumvent Tamoxifen-Resistant Breast Cancer
    (2011) Tiwary, Richa; Yu, Weiping; Degraffenried, Linda A.; Sanders, Bob G.; Kline, Kimberly; Degraffenried, Linda A.; Sanders, Bob G.; Kline, Kimberly
    Adjuvant treatment with tamoxifen substantially improves survival of women with estrogen-receptor positive (ER+) tumors. Tamoxifen resistance (TAMR) limits clinical benefit. RRR alpha tocopherol ether-linked acetic acid analogue (alpha-TEA) is a small bioactive lipid with potent anticancer activity. We evaluated the ability of alpha-TEA in the presence of tamoxifen to circumvent TAMR in human breast cancer cell lines. Methods: Two genotypically matched sets of TAM-sensitive (TAMS) and TAM-resistant (TAMR) human breast cancer cell lines were assessed for signal-transduction events with Western blotting, apoptosis induction with Annexin V-FITC/PI assays, and characterization of cholesterol-rich microdomains with fluorescence staining. Critical involvement of selected mediators was determined by using RNA interference and chemical inhibitors. Results: Growth-factor receptors (total and phosphorylated forms of HER-1 and HER-2), their downstream prosurvival mediators pAkt, pmTOR, and pERK1/2, phosphorylated form of estrogen receptor-alpha (pER-alpha at Ser-167 and Ser-118, and cholesterol-rich lipid microdomains were highly amplified in TAMR cell lines and enhanced by treatment with TAM. alpha-TEA disrupted cholesterol-rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators, and induced DR5-mediated mitochondria-dependent apoptosis via an endoplasmic reticulum stress-triggered pro-death pJNK/CHOP/DR5 amplification loop. Furthermore, methyl-beta-cyclodextrin (M beta CD), a chemical disruptor of cholesterol rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators and to induce apoptosis. Conclusions: Data for the first time document that targeting cholesterol-rich lipid microdomains is a potential strategy to circumvent TAMR, and the combination of alpha-TEA + TAM can circumvent TAMR by suppression of prosurvival signaling via disruption of cholesterol-rich lipid microdomains and activation of apoptotic pathways via induction of endoplasmic reticulum stress.