sirolimus and deguelin

Topics: Animals; Carrier Proteins; Dilatation; Fibrosis; GATA4 Transcription Factor; Heart Ventricles; Intracellular Signaling Peptides and Proteins; Lithium Compounds; Male; MAP Kinase Signaling System; Myocardial Contraction; Myocardial Infarction; NFATC Transcription Factors; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphoproteins; Proto-Oncogene Proteins c-akt; Rats; Rats, Wistar; Rotenone; Sirolimus; Stimulation, Chemical; Time Factors; TOR Serine-Threonine Kinases; Ventricular Remodeling

Triple-negative breast cancers (TNBC) are aggressive malignancies with no effective targeted therapies. Recent gene expression profiling of these heterogeneous cancers and the classification of cell line models now allows for the identification of compounds with selective activities against molecular subtypes of TNBC. The natural product deguelin was found to have selective activity against MDA-MB-453 and SUM-185PE cell lines, which both model the luminal androgen receptor (LAR) subtype of TNBC. Deguelin potently inhibited proliferation of these cells with GI50 values of 30 and 61 nM, in MDA-MB-453 and SUM-185PE cells, respectively. Deguelin had exceptionally high selectivity, 197 to 566-fold, for these cell lines compared to cell lines representing other TNBC subtypes. Deguelin's mechanisms of action were investigated to determine how it produced these potent and selective effects. Our results show that deguelin has dual activities, inhibiting PI3K/Akt/mTOR signaling, and decreasing androgen receptor levels and nuclear localization. Based on these data, we hypothesized that the combination of the mTOR inhibitor rapamycin and the antiandrogen enzalutamide would have efficacy in LAR models. Rapamycin and enzalutamide showed additive effects in MDA-MB-453 cells, and both drugs had potent antitumor efficacy in a LAR xenograft model. These results suggest that the combination of antiandrogens and mTOR inhibitors might be an effective strategy for the treatment of androgen receptor-expressing TNBC.

Topics: Animals; Antineoplastic Agents; Benzamides; Cell Line, Tumor; Cell Nucleus; Cell Proliferation; Cell Survival; Drug Synergism; Female; Gene Expression Regulation, Neoplastic; Humans; Mice; Nitriles; Phenylthiohydantoin; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Receptors, Androgen; Rotenone; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Triple Negative Breast Neoplasms; Xenograft Model Antitumor Assays

Interferon-alpha (IFNα)-induced cell death of tumor cells is likely mediated through several signaling pathways. We previously demonstrated that blocking the activation of phosphoinositide-3-kinase, PI3K, or mammalian target of rapamycin, mTOR, partially inhibited apoptosis induced by IFNα. Here, we postulate using pharmacological inhibition and dominant negative mutants that activation of signal transducer and activator of transcription-1, STAT1, is also required for the cell death induced by IFNα. Inhibition of STAT1 tyrosine phosphorylation and DNA binding by a naturally occurring rotenoid deguelin also rescued U266 myeloma cell lines from IFNα-induced apoptosis. Deguelin had no effect on upstream Jak kinases or STAT2 phosphorylation suggesting the involvement of a yet unknown mechanism. Inhibition of STAT1 tyrosine phosphorylation and activity was independent of the known effects of deguelin on PI3K, Akt or mTOR as shown using selective pharmacological inhibitors against these kinases. The combination of deguelin and PI3K or mTOR antagonists further inhibited apoptosis suggesting that both the Jak-STAT and the PI3K/mTOR pathways contribute to the induction of apoptosis by IFNα in these cells. Over-expression of STAT1-Y701A or K410/413A mutants in Rhek-1 keratinocytes largely inhibited apoptosis further supporting the importance of STAT1 phosphorylation and activity for IFNα-induced cell death. Thus, at least two signaling pathways, one of which requires STAT1 activation, cooperate to mediate IFNα-induced apoptosis.

Topics: Apoptosis; Cell Death; Cell Line, Tumor; HSP90 Heat-Shock Proteins; Humans; Interferon-alpha; Mutant Proteins; Oncogene Protein v-akt; Phosphorylation; Protein Kinase Inhibitors; Rotenone; Signal Transduction; Sirolimus; STAT1 Transcription Factor; Transfection

Lung cancer is the leading cause of cancer-related death in the United States, and 85 to 90% of lung cancer cases are associated with tobacco use. Tobacco components promote lung tumorigenesis through genotoxic effects, as well as through biochemical modulation of signaling pathways such as the Akt/mammalian target of rapamycin (mTOR) pathway that regulates cell proliferation and survival. This review will describe cell surface receptors and other upstream components required for tobacco carcinogen-induced activation of Akt and mTOR. Preclinical studies show that inhibitors of the Akt/mTOR pathway inhibit tumor formation in mouse models of carcinogen-induced lung tumorigenesis. Some of these inhibitors will be highlighted, and their clinical potential for the treatment and prevention of lung cancer will be discussed.

Topics: Animals; Carcinogens; Humans; Indoles; Inositol; Intracellular Signaling Peptides and Proteins; Lung Neoplasms; Mice; Nicotiana; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Rotenone; Signal Transduction; Sirolimus; Smoking; TOR Serine-Threonine Kinases

Mature striatal medium size spiny neurons express the dopamine and cyclic AMP-regulated phosphoprotein, 32 kDa (DARPP-32), but little is known about the mechanisms regulating its levels or the specification of fully differentiated neuronal subtypes. Cell extrinsic molecules that increase DARPP-32 mRNA and/or protein levels include brain-derived neurotrophic factor (BDNF), retinoic acid, and estrogen. DARPP-32 induction by BDNF in vitro requires phosphatidylinositide 3-kinase (PI3K), but inhibition of phosphorylation of protein kinase B/Akt does not entirely abolish expression of DARPP-32. Moreover, the requirement for Akt has not been established. Using pharmacologic inhibitors of PI3K, Akt, and cyclin-dependent kinase 5 (cdk5) and constitutively active and dominant negative PI3K, Akt, cdk5, and p35 viruses in cultured striatal neurons, we measured BDNF-induced levels of DARPP-32 protein and/or mRNA. We demonstrated that both the PI3K/Akt/mammalian target of rapamycin and the cdk5/p35 signal transduction pathways contribute to the induction of DARPP-32 protein levels by BDNF and that the effects are on both the transcriptional and translational levels. It also appears that PI3K is upstream of cdk5/p35, and its activation can lead to an increase in p35 protein levels. These data support the presence of multiple signal transduction pathways mediating expression of DARPP-32 in vitro, including a novel, important pathway via by which PI3K regulates the contribution of cdk5/p35.

Topics: Androstadienes; Animals; Brain-Derived Neurotrophic Factor; Cells, Cultured; Cyclin-Dependent Kinase 5; Dopamine and cAMP-Regulated Phosphoprotein 32; Huntington Disease; Mice; Nerve Tissue Proteins; Neurons; Phosphatidylinositol 3-Kinases; Protein Kinases; Proto-Oncogene Proteins c-akt; Rotenone; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Wortmannin