Gary G Chiang

Sanford-Burnham Medical Research Institute, La Jolla, California, United States

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Publications (20)136.83 Total impact

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    ABSTRACT: Metabolic rewiring is an established hallmark of cancer, but the details of this rewiring at a systems level are not well characterized. Here we acquire this insight in a melanoma cell line panel by tracking metabolic flux using isotopically labeled nutrients. Metabolic profiling and flux balance analysis were used to compare normal melanocytes to melanoma cell lines in both normoxic and hypoxic conditions. All melanoma cells exhibited the Warburg phenomenon; they used more glucose and produced more lactate than melanocytes. Other changes were observed in melanoma cells that are not described by the Warburg phenomenon. Hypoxic conditions increased fermentation of glucose to lactate in both melanocytes and melanoma cells (the Pasteur effect). However, metabolism was not strictly glycolytic, as the tricarboxylic acid (TCA) cycle was functional in all melanoma lines, even under hypoxia. Furthermore, glutamine was also a key nutrient providing a substantial anaplerotic contribution to the TCA cycle. In the WM35 melanoma line glutamine was metabolized in the "reverse" (reductive) direction in the TCA cycle, particularly under hypoxia. This reverse flux allowed the melanoma cells to synthesize fatty acids from glutamine while glucose was primarily converted to lactate. Altogether, this study, which is the first comprehensive comparative analysis of metabolism in melanoma cells, provides a foundation for targeting metabolism for therapeutic benefit in melanoma.
    Journal of Biological Chemistry 12/2011; 286(49):42626-34. · 4.65 Impact Factor
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    ABSTRACT: Metabolic rewiring is an established hallmark of cancer, but the details of this rewiring at a systems level are not well characterized. Here we acquire this insight in a melanoma cell line panel by tracking metabolic flux using isotopically labeled nutrients. Metabolic profiling and flux balance analysis were used to compare normal melanocytes to melanoma cell lines in both normoxic and hypoxic conditions. All melanoma cells exhibited the Warburg phenomenon; they used more glucose and produced more lactate than melanocytes. Other changes were observed in melanoma cells that are not described by the Warburg phenomenon. Hypoxic conditions increased fermentation of glucose to lactate in both melanocytes and melanoma cells (the Pasteur effect). However, metabolism was not strictly glycolytic, as the tricarboxylic acid (TCA) cycle was functional in all melanoma lines, even under hypoxia. Furthermore, glutamine was also a key nutrient providing a substantial anaplerotic contribution to the TCA cycle. In the WM35 melanoma line glutamine was metabolized in the “reverse” (reductive) direction in the TCA cycle, particularly under hypoxia. This reverse flux allowed the melanoma cells to synthesize fatty acids from glutamine while glucose was primarily converted to lactate. Altogether, this study, which is the first comprehensive comparative analysis of metabolism in melanoma cells, provides a foundation for targeting metabolism for therapeutic benefit in melanoma.
    Journal of Biological Chemistry 12/2011; 286(49):42626-42634. · 4.65 Impact Factor
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    ABSTRACT: In melanoma, the activation of pro-survival signaling pathways, such as the AKT and NF-κB pathways, is critical for tumor growth. We have recently reported that the AKT inhibitor BI-69A11 causes efficient inhibition of melanoma growth. Here, we show that in addition to its AKT inhibitory activity, BI-69A11 also targets the NF-κB pathway. In melanoma cell lines, BI-69A11 inhibited TNF-α-stimulated IKKα/β and IκB phosphorylation as well as NF-κB reporter gene expression. Furthermore, the effective inhibition of melanoma growth by BI-69A11 was attenuated upon NF-κB activation. Mechanistically, reduced NF-κB signaling by BI-69-A11 is mediated by the inhibition of sphingosine kinase 1, identified in a screen of 315 kinases. Significantly, we demonstrate that BI-69A11 is well tolerated and orally active against UACC 903 and SW1 melanoma xenografts. Our results demonstrate that BI-69A11 inhibits both the AKT and the NF-κB pathways and that the dual targeting of these pathways may be efficacious as a therapeutic strategy in melanoma.
    Pigment Cell & Melanoma Research 06/2011; 24(4):703 - 713. · 5.84 Impact Factor
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    ABSTRACT: Mutations in the MID1 gene are causally linked to X-linked Opitz BBB/G syndrome (OS), a congenital disorder that primarily affects the formation of diverse ventral midline structures. The MID1 protein has been shown to function as an E3 ligase targeting the catalytic subunit of protein phosphatase 2A (PP2A-C) for ubiquitin-mediated degradation. However, the molecular pathways downstream of the MID1/PP2A axis that are dysregulated in OS and that translate dysfunctional MID1 and elevated levels of PP2A-C into the OS phenotype are poorly understood. Here, we show that perturbations in MID1/PP2A affect mTORC1 signaling. Increased PP2A levels, resulting from proteasome inhibition or depletion of MID1, lead to disruption of the mTOR/Raptor complex and down-regulated mTORC1 signaling. Congruously, cells derived from OS patients that carry MID1 mutations exhibit decreased mTORC1 formation, S6K1 phosphorylation, cell size, and cap-dependent translation, all of which is rescued by expression of wild-type MID1 or an activated mTOR allele. Our findings define mTORC1 signaling as a downstream pathway regulated by the MID1/PP2A axis, suggesting that mTORC1 plays a key role in OS pathogenesis.
    Proceedings of the National Academy of Sciences 05/2011; 108(21):8680-5. · 9.81 Impact Factor
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    ABSTRACT: A new series of 3-ethynyl-1H-indazoles has been synthesized and evaluated in both biochemical and cell-based assays as potential kinase inhibitors. Interestingly, a selected group of compounds identified from this series exhibited low micromolar inhibition against critical components of the PI3K pathway, targeting PI3K, PDK1, and mTOR kinases. A combination of computational modeling and structure-activity relationship studies reveals a possible novel mode for PI3K inhibition, resulting in a PI3Kα isoform-specific compound. Hence, by targeting the most oncogenic mutant isoform of PI3K, the compound displays antiproliferative activity both in monolayer human cancer cell cultures and in three-dimensional tumor models. Because of its favorable physicochemical, in vitro ADME and drug-like properties, we propose that this novel ATP mimetic scaffold could prove useful in deriving novel selecting and multikinase inhibitors for clinical use.
    Journal of Medicinal Chemistry 11/2010; · 5.61 Impact Factor
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    ABSTRACT: The phosphoinositide 3-kinase (PI3K) pathway regulates mammalian cell growth, survival, and motility and plays a major pathogenetic role in human prostate cancer (PCa). However, the oncogenic contributions downstream of the PI3K pathway made by mammalian target of rapamycin complex 1 (mTORC1)-mediated cell growth signal transduction in PCa have yet to be elucidated in detail. Here, we engineered constitutive mTORC1 activation in prostate epithelium by a conditional genetic deletion of tuberous sclerosis complex 1 (Tsc1), a potent negative regulator of mTORC1 signaling. Epithelial inactivation was not immediately tumorigenic, but Tsc1-deficient mice developed prostatic intraepithelial neoplasia (mPIN) in lateral and anterior prostates by 6 months of age, with increasing disease penetrance over time. Lateral prostate lesions in 16- to 22-month-old mutant mice progressed to two types of more advanced lesions, adenomatous gland forming lesion (Type 1) and atypical glands embedded in massively expanded reactive stroma (Type 2). Both Type 1 and Type 2 lesions contained multiple foci of microinvasive carcinoma. Epithelial neoplastic and atypical stromal lesions persisted despite 4 weeks of RAD001 chemotherapy. Rapalogue resistance was not due to AKT or extracellular signal-regulated kinase 1/2 activation. Expression of the homeobox gene Nkx3.1 was lost in Tsc1-deficient mPIN, and it cooperated with TSC1 loss in mPIN initiation in doubly mutant Tsc1:Nkx3.1 prostatic epithelial knockout mice. Thus, TSC1 inactivation distal to PI3K and AKT activation is sufficient to activate a molecular signaling cascade producing prostatic neoplasia and focal carcinogenesis.
    Cancer Research 10/2010; 70(21):8937-47. · 9.28 Impact Factor
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    ABSTRACT: Small GTPase Ras homologue enriched in brain (RHEB) binds and activates the key metabolic regulator mTORC1, which has an important role in cancer cells, but the role of RHEB in cancer pathogenesis has not been shown. By performing a meta-analysis of published cancer cytogenetic and transcriptome databases, we defined a gain of chromosome 7q36.1-q36.3 containing the RHEB locus, an overexpression of RHEB mRNA in several different carcinoma histotypes, and an association between RHEB upregulation and poor prognosis in breast and head and neck cancers. To model gain of function in epithelial malignancy, we targeted Rheb expression to murine basal keratinocytes of transgenic mice at levels similar to those that occur in human squamous cancer cell lines. Juvenile transgenic epidermis displayed constitutive mTORC1 pathway activation, elevated cyclin D1 protein, and diffuse skin hyperplasia. Skin tumors subsequently developed with concomitant stromal angio-inflammatory foci, evidencing induction of an epidermal hypoxia-inducible factor-1 transcriptional program, and paracrine feed-forward activation of the interleukin-6-signal transducer and activator of transcription 3 pathway. Rheb-induced tumor persistence and neoplastic molecular alterations were mTORC1 dependent. Rheb markedly sensitized transgenic epidermis to squamous carcinoma induction following a single dose of Ras-activating carcinogen 7,12-dimethylbenz(a)anthracene. Our findings offer direct evidence that RHEB facilitates multistage carcinogenesis through induction of multiple oncogenic mechanisms, perhaps contributing to the poor prognosis of patients with cancers overexpressing RHEB.
    Cancer Research 04/2010; 70(8):3287-98. · 9.28 Impact Factor
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    ABSTRACT: The DNA replication machinery plays additional roles in S phase checkpoint control, although the identities of the replication proteins involved in checkpoint activation remain elusive. Here, we report that depletion of the prereplicative complex (pre-RC) protein Cdc6 causes human nontransformed diploid cells to arrest nonlethally in G1-G1/S and S phase, whereas multiple cancer cell lines undergo G1-G1/S arrest and cell death. These divergent phenotypes are dependent on the activation, or lack thereof, of an ataxia telangiectasia and Rad3-related (ATR)-dependent S phase checkpoint that inhibits replication fork progression. Although pre-RC deficiency induces chromatin structural alterations in both nontransformed and cancer cells that normally lead to ATR checkpoint activation, the sensor mechanisms in cancer cells seem to be compromised such that higher levels of DNA replication stress/damage are required to trigger checkpoint response. Our results suggest that therapy-induced disruption of pre-RC function might exert selective cytotoxic effects on tumor cells in human patients.
    Molecular biology of the cell 08/2009; 20(17):3953-64. · 5.98 Impact Factor
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    ABSTRACT: The cellular response to hypoxia involves several signalling pathways that mediate adaptation and survival. REDD1 (regulated in development and DNA damage responses 1), a hypoxia-inducible factor-1 target gene, has a crucial role in inhibiting mammalian target of rapamycin complex 1 (mTORC1) signalling during hypoxic stress. However, little is known about the signalling pathways and post-translational modifications that regulate REDD1 function. Here, we show that REDD1 is subject to ubiquitin-mediated degradation mediated by the CUL4A-DDB1-ROC1-beta-TRCP E3 ligase complex and through the activity of glycogen synthase kinase 3beta. Furthermore, REDD1 degradation is crucially required for the restoration of mTOR signalling as cells recover from hypoxic stress. Our findings define a mechanism underlying REDD1 degradation and its importance for regulating mTOR signalling.
    EMBO Reports 07/2009; 10(8):866-72. · 7.19 Impact Factor
  • Toshiya Tsuji, Eric Lau, Gary G Chiang, Wei Jiang
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    ABSTRACT: The Dbf4/Drf1-dependent S-phase-promoting kinase Cdc7 (Ddk) is thought to be an essential target inactivated by the S-phase checkpoint machinery that inhibits DNA replication. However, we show here that the complex formation, chromatin association, and kinase activity of Ddk are not inhibited during the DNA-damage-induced S-phase checkpoint response in Xenopus egg extracts and mammalian cells. Instead, we find that Ddk plays an active role in regulating S-phase checkpoint signaling. Addition of purified Ddk to Xenopus egg extracts or overexpression of Dbf4 in HeLa cells downregulates ATR-Chk1 checkpoint signaling and overrides the inhibition of DNA replication and cell-cycle progression induced by DNA-damaging agents. These results indicate that Ddk functions as an upstream regulator to monitor S-phase checkpoint signaling. We propose that Ddk modulates the S-phase checkpoint control by attenuating checkpoint signaling and triggering DNA replication reinitiation during the S-phase checkpoint recovery.
    Molecular cell 01/2009; 32(6):862-9. · 14.61 Impact Factor
  • Gary G Chiang, Robert T Abraham
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    ABSTRACT: The mammalian target of rapamycin (mTOR) is an unconventional protein kinase that is centrally involved in the control of cancer cell metabolism, growth and proliferation. The mTOR pathway has attracted broad scientific and clinical interest, particularly in light of the ongoing clinical cancer trials with mTOR inhibitors. The mixed clinical results to date reflect the complexity of both cancer as a disease target, and the mTOR signaling network, which contains two functionally distinct mTOR complexes, parallel regulatory pathways, and feedback loops that contribute to the variable cellular responses to the current inhibitors. In this review, we discuss the regulatory pathways that govern mTOR activity, and highlight clinical results obtained with the first generation of mTOR inhibitors to reach the oncology clinics.
    Trends in Molecular Medicine 11/2007; 13(10):433-42. · 9.57 Impact Factor
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    ABSTRACT: The phosphatidylinositol 3-kinase (PI3K) pathway is activated in many human tumors and mediates processes such as cell proliferation, survival, adhesion, and motility. The natural product, wortmannin, has been widely used to study the functional consequences of PI3K inhibition in both normal and transformed cells in culture but is not a suitable cancer chemotherapeutic agent due to stability and toxicity issues. PX-866, an improved wortmannin analogue, displays significant antitumor activity in xenograft models. Here, we directly compare PX-866 and wortmannin in human cancer cell lines cultured in monolayer or as three-dimensional spheroids. Both PI3K inhibitors failed to inhibit monolayer cell growth at concentrations up to 100 nmol/L but strongly suppressed spheroid growth at low nanomolar concentrations, with PX-866 showing greater potency than wortmannin. Relative to wortmannin, PX-866 treatment results in a more sustained loss of Akt phosphorylation, suggesting that the increased potency of PX-866 is related to a more durable inhibition of PI3K signaling. PX-866 and wortmannin both inhibit spheroid growth without causing cytotoxicity, similar to known cytostatic agents, such as rapamycin. PX-866 also inhibits cancer cell motility at subnanomolar concentrations. These findings suggest that the antitumor activities of PX-866 stem from prolonged inhibition of the PI3K pathway and inhibition of cell motility. In addition, we propose that the use of three-dimensional tumor models is more predictive of in vivo growth inhibition by PI3K inhibitors in cancer cell lines lacking phosphatase and tensin homologue activity or expression.
    Molecular Cancer Therapeutics 10/2007; 6(9):2505-14. · 5.60 Impact Factor
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    ABSTRACT: The mammalian target of rapamycin (mTOR) is a protein that is intricately involved in signaling pathways controlling cell growth. Rapamycin is a natural product that binds and inhibits mTOR function by interacting with its FKBP-rapamycin-binding (FRB) domain. Here we report on the NMR solution structure of FRB and on further studies aimed at the identification and characterization of novel ligands that target the rapamycin binding pocket. The biological activity of the ligands, and that of rapamycin in the absence of FKBP12, was investigated by assaying the kinase activity of mTOR. While we found that rapamycin binds the FRB domain and inhibits the kinase activity of mTOR even in the absence of FKBP12 (in the low micromolar range), our most potent ligands bind to FRB with similar binding affinity but inhibit the kinase activity of mTOR at much higher concentrations. However, we have also identified one low-affinity compound that is also capable of inhibiting mTOR. Hence, we have identified compounds that can directly mimic rapamycin or can dissociate the FRB binding from the inhibition of the catalytic activity of mTOR. As such, these ligands could be useful in deciphering the complex regulation of mTOR in the cell and in validating the FRB domain as a possible target for the development of novel therapeutic compounds.
    Biochemistry 09/2006; 45(34):10294-302. · 3.38 Impact Factor
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    ABSTRACT: The Chk1 kinase is a major effector of S phase checkpoint signaling during the cellular response to genotoxic stress. Here, we report that replicative stress induces the polyubiquitination and degradation of Chk1 in human cells. This response is triggered by phosphorylation of Chk1 at Ser-345, a known target site for the upstream activating kinase ATR. The ubiquitination of Chk1 is mediated by E3 ligase complexes containing Cul1 or Cul4A. Treatment of cells with the anticancer agent camptothecin (CPT) triggers Chk1 destruction, which blocks recovery from drug-induced S phase arrest and leads to cell death. These findings indicate that ATR-dependent phosphorylation of Chk1 delivers a signal that both activates Chk1 and marks this protein for proteolytic degradation. Proteolysis of activated Chk1 may promote checkpoint termination under normal conditions, and may play an important role in the cytotoxic effects of CPT and related anticancer drugs.
    Molecular Cell 10/2005; 19(5):607-18. · 15.28 Impact Factor
  • Gary G Chiang, Robert T Abraham
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    ABSTRACT: The mammalian target of rapamycin (mTOR) coordinates cell growth with the growth factor and nutrient/energy status of the cell. The phosphatidylinositol 3-kinase-AKT pathway is centrally involved in the transmission of mitogenic signals to mTOR. Previous studies have shown that mTOR is a direct substrate for the AKT kinase and identified Ser-2448 as the AKT target site in mTOR. In this study, we demonstrate that rapamycin, a specific inhibitor of mTOR function, blocks serum-stimulated Ser-2448 phosphorylation and that this drug effect is not explained by the inhibition of AKT. Furthermore, the phosphorylation of Ser-2448 was dependent on mTOR kinase activity, suggesting that mTOR itself or a protein kinase downstream from mTOR was responsible for the modification of Ser-2448. Here we show that p70S6 kinase phosphorylates mTOR at Ser-2448 in vitro and that ectopic expression of rapamycin-resistant p70S6 kinase restores Ser-2448 phosphorylation in rapamycin-treated cells. In addition, we show that cellular amino acid status, which modulates p70S6 kinase (S6K1) activity via the TSC/Rheb pathway, regulates Ser-2448 phosphorylation. Finally, small interfering RNA-mediated depletion of p70S6 kinase reduces Ser-2448 phosphorylation in cells. Taken together, these results suggest that p70S6 kinase is a major effector of mTOR phosphorylation at Ser-2448 in response to both mitogen- and nutrient-derived stimuli.
    Journal of Biological Chemistry 08/2005; 280(27):25485-90. · 4.65 Impact Factor
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    ABSTRACT: Phosphoinositide 3-kinases (PI3-Ks) are an ubiquitous class of signaling enzymes that regulate diverse cellular processes including growth, differentiation, and motility. Physiological roles of PI3-Ks have traditionally been assigned using two pharmacological inhibitors, LY294002 and wortmannin. Although these compounds are broadly specific for the PI3-K family, they show little selectivity among family members, and the development of isoform-specific inhibitors of these enzymes has been long anticipated. Herein, we prepare compounds from two classes of arylmorpholine PI3-K inhibitors and characterize their specificity against a comprehensive panel of targets within the PI3-K family. We identify multiplex inhibitors that potently inhibit distinct subsets of PI3-K isoforms, including the first selective inhibitor of p110beta/p110delta (IC(50) p110beta=0.13 microM, p110delta=0.63 microM). We also identify trends that suggest certain PI3-K isoforms may be more sensitive to potent inhibition by arylmorpholines, thereby guiding future drug design based on this pharmacophore.
    Bioorganic & Medicinal Chemistry 10/2004; 12(17):4749-59. · 2.90 Impact Factor
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    ABSTRACT: A series of viridin analogs was prepared from wortmannin by nucleophilic ring opening at C(20) and evaluated against the signaling kinases PI-3-kinase and mTOR. Several subnanomolar enzyme inhibitors with orders of magnitude selectivity for PI-3-kinase and strong cytotoxic activity against four cancer cell lines were identified. Among the ten most promising derivatives, six demonstrated lower liver toxicity and greater promise for inhibition of tumor cell growth than the lead structure wortmannin.
    Organic & Biomolecular Chemistry 08/2004; 2(13):1911-20. · 3.57 Impact Factor
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    ABSTRACT: Rapamycin and its analogues have shown promising anticancer activities in preclinical and clinical studies. However, the mechanism whereby rapamycin inhibits signaling through the mammalian target of rapamycin (mTOR) remains poorly understood. Here, we show that the FKBP12/rapamycin complex is an essentially irreversible inhibitor of mTOR kinase activity in vitro. However, we observe no suppression of mTOR catalytic activity after immunoprecipitation from rapamycin-treated cells. These results suggest either that rapamycin acts as a reversible kinase inhibitor in intact cells or that the cellular effects of rapamycin are not mediated through global suppression in mTOR kinase activity. To better understand the cellular pharmacology of rapamycin, we compared the individual and combined effects of rapamycin and kinase-inactive mTOR expression on a panel of mTOR-dependent cellular responses. These studies identified glycolytic activity, amino acid transporter trafficking, and Akt kinase activity as novel, mTOR-modulated functions in mammalian cells. Whereas kinase-inactive mTOR did not enhance the decreases in cell size and glycolysis induced by rapamycin, expression of this mTOR mutant significantly enhanced the inhibitory effects of rapamycin on cell proliferation, 4EBP1 phosphorylation, and Akt activity. Unexpectedly, amino acid transporter trafficking was perturbed by kinase-inactive mTOR but not by rapamycin, indicating that this process is rapamycin insensitive. These results indicate that rapamycin exerts variable inhibitory actions on mTOR signaling functions and suggest that direct inhibitors of the mTOR kinase domain will display substantially broader anticancer activities than rapamycin.
    Cancer Research 01/2004; 63(23):8451-60. · 8.65 Impact Factor
  • Gary G Chiang, Robert T Abraham
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    ABSTRACT: Members of the phosphoinositide-3-kinase-related kinase (PIKK) family, which includes mTOR, ATM, ATR, and hSMG-1, play important roles in regulating the cellular response to environmental stimuli. Despite the similarity of their catalytic domain to that of phosphoinositide-3-kinase, these extremely large (>250 kDa) polypeptides function as serine/threonine protein kinases. The catalytic activities of these PIKK family members can now be measured in immune-complex kinase assays. This assay involves isolation of the kinase by immunoprecipitation and the in vitro phosphorylation of a specific substrate in the presence of radio-labeled ATP. Here we describe, in detail, the determination of PIKK catalytic activity with a standardized immune-complex kinase assay protocol.
    Methods in molecular biology (Clifton, N.J.) 01/2004; 281:125-41. · 1.29 Impact Factor
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    ABSTRACT: Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric transcription factor containing an inducibly expressed HIF-1alpha subunit and a constititutively expressed HIF-1beta subunit. Under hypoxic conditions, the HIF-1alpha subunit accumulates due to a decrease in the rate of proteolytic degradation, and the resulting HIF-1alpha-HIF-1beta heterodimers undergo posttranslational modifications that promote transactivation. Recent studies suggest that amplified signaling through phosphoinositide 3-kinase, and its downstream target, mTOR, enhances HIF-1-dependent gene expression in certain cell types. In the present study, we have explored further the linkage between mTOR and HIF-1 in PC-3 prostate cancer cells treated with hypoxia or the hypoxia mimetic agent, CoCl(2). Pretreatment of PC-3 cells with the mTOR inhibitor, rapamycin, inhibited both the accumulation of HIF-1alpha and HIF-1-dependent transcription induced by hypoxia or CoCl(2). Transfection of these cells with wild-type mTOR enhanced HIF-1 activation by hypoxia or CoCl(2), while expression of a rapamycin-resistant mTOR mutant rendered both HIF-1alpha stabilization and HIF-1 transactivating function refractory to inhibition by rapamycin. Studies with GAL4-HIF-1alpha fusion proteins pinpointed the oxygen-dependent degradation domain as a critical target for the rapamycin-sensitive, mTOR-dependent signaling pathway leading to HIF-1alpha stabilization by CoCl(2). These studies position mTOR as an upstream activator of HIF-1 function in cancer cells and suggest that the antitumor activity of rapamycin is mediated, in part, through the inhibition of cellular responses to hypoxic stress.
    Molecular and Cellular Biology 11/2002; 22(20):7004-14. · 5.04 Impact Factor

Publication Stats

1k Citations
136.83 Total Impact Points

Institutions

  • 2004–2011
    • Sanford-Burnham Medical Research Institute
      • Signal Transduction Research Program
      La Jolla, California, United States
    • La Jolla Bioengineering Institute
      La Jolla, California, United States
    • University of Pennsylvania
      Philadelphia, Pennsylvania, United States
  • 2002
    • Duke University Medical Center
      • Department of Pharmacology and Cancer Biology
      Durham, NC, United States