Publications (3)27.1 Total impact
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Article: Resistance to discodermolide, a microtubule-stabilizing agent and senescence inducer, is 4E-BP1–dependent
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ABSTRACT: Discodermolide is a microtubule-stabilizing agent that induces accelerated cell senescence. A discodermolide-resistant cell line, AD32, was generated from the human lung cancer cell line A549. We hypothesize that the major resistance mechanism in these cells is escape from accelerated senescence. AD32 cells have decreased levels of 4E-BP1 mRNA and protein, relative to the parental discodermolide-sensitive A549 cells. Lentiviral-mediated re-expression of wild-type 4E-BP1 in AD32 cells increased the proliferation rate and reverted resistance to discodermolide via restoration of discodermolide-induced accelerated senescence. Consistent with this, cell growth and response to discodermolide was confirmed in vivo using tumor xenograft models. Furthermore, reintroduction of a nonphosphorylatable mutant (Thr-37/46 Ala) of 4E-BP1 was able to partially restore sensitivity and enhance proliferation in AD32 cells, suggesting that these effects are independent of phosphorylation by mTORC1. Microarray profiling of AD32-resistant cells versus sensitive A549 cells, and subsequent unbiased gene ontology analysis, identified molecular pathways and functional groupings of differentially expressed mRNAs implicated in overcoming discodermolide-induced senescence. The most statistically significant classes of differentially expressed genes included p53 signaling, G2/M checkpoint regulation, and genes involved in the role of BRCA1 in the DNA damage response. Consistent with this, p53 protein expression was up-regulated and had increased nuclear localization in AD32 cells relative to parental A549 cells. Furthermore, the stability of p53 was enhanced in AD32 cells. Our studies propose a role for 4E-BP1 as a regulator of discodermolide-induced accelerated senescence.Proceedings of the National Academy of Sciences 01/2011; 108(1):391-396. · 9.68 Impact Factor -
Article: Resistance to discodermolide, a microtubule-stabilizing agent and senescence inducer, is 4E-BP1-dependent.
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ABSTRACT: Discodermolide is a microtubule-stabilizing agent that induces accelerated cell senescence. A discodermolide-resistant cell line, AD32, was generated from the human lung cancer cell line A549. We hypothesize that the major resistance mechanism in these cells is escape from accelerated senescence. AD32 cells have decreased levels of 4E-BP1 mRNA and protein, relative to the parental discodermolide-sensitive A549 cells. Lentiviral-mediated re-expression of wild-type 4E-BP1 in AD32 cells increased the proliferation rate and reverted resistance to discodermolide via restoration of discodermolide-induced accelerated senescence. Consistent with this, cell growth and response to discodermolide was confirmed in vivo using tumor xenograft models. Furthermore, reintroduction of a nonphosphorylatable mutant (Thr-37/46 Ala) of 4E-BP1 was able to partially restore sensitivity and enhance proliferation in AD32 cells, suggesting that these effects are independent of phosphorylation by mTORC1. Microarray profiling of AD32-resistant cells versus sensitive A549 cells, and subsequent unbiased gene ontology analysis, identified molecular pathways and functional groupings of differentially expressed mRNAs implicated in overcoming discodermolide-induced senescence. The most statistically significant classes of differentially expressed genes included p53 signaling, G2/M checkpoint regulation, and genes involved in the role of BRCA1 in the DNA damage response. Consistent with this, p53 protein expression was up-regulated and had increased nuclear localization in AD32 cells relative to parental A549 cells. Furthermore, the stability of p53 was enhanced in AD32 cells. Our studies propose a role for 4E-BP1 as a regulator of discodermolide-induced accelerated senescence.Proceedings of the National Academy of Sciences 01/2011; 108(1):391-6. · 9.68 Impact Factor -
Article: Insulin-like growth factor 2 expression modulates Taxol resistance and is a candidate biomarker for reduced disease-free survival in ovarian cancer.
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ABSTRACT: This study was undertaken to examine the role of the insulin-like growth factor (IGF) signaling pathway in the response of ovarian cancer cells to Taxol and to evaluate the significance of this pathway in human epithelial ovarian tumors. The effect of Taxol treatment on AKT activation in A2780 ovarian carcinoma cells was evaluated using antibodies specific for phospho-AKT. To study the drug-resistant phenotype, we developed a Taxol-resistant cell line, HEY-T30, derived from HEY ovarian carcinoma cells. IGF2 expression was measured by real-time PCR. A type 1 IGF receptor (IGF1R) inhibitor, NVP-AEW541, and IGF2 small interfering RNA were used to evaluate the effect of IGF pathway inhibition on proliferation and Taxol sensitivity. IGF2 protein expression was evaluated by immunohistochemistry in 115 epithelial ovarian tumors and analyzed in relation to clinical/pathologic factors using the chi(2) or Fisher's exact tests. The influence of IGF2 expression on survival was studied with Cox regression. Taxol-induced AKT phosphorylation required IGF1R tyrosine kinase activity and was associated with upregulation of IGF2. Resistant cells had higher IGF2 expression compared with sensitive cells, and IGF pathway inhibition restored sensitivity to Taxol. High IGF2 tumor expression correlated with advanced stage (P < 0.001) and tumor grade (P < 0.01) and reduced disease-free survival (P < 0.05). IGF2 modulates Taxol resistance, and tumor IGF2 expression is a candidate prognostic biomarker in epithelial ovarian tumors. IGF pathway inhibition sensitizes drug-resistant ovarian carcinoma cells to Taxol. Such novel findings suggest that IGF2 represents a therapeutic target in ovarian cancer, particularly in the setting of Taxol resistance.Clinical Cancer Research 06/2010; 16(11):2999-3010. · 7.74 Impact Factor
