G Powis

University of Texas MD Anderson Cancer Center, Houston, TX, United States

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Publications (329)1441.25 Total impact

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    ABSTRACT: Clear cell kidney cancer (CRCC) is initiated typically by loss of the tumor suppressor VHL, driving constitutive activation of HIF-1 and HIF-2. However, whereas HIF-1 has a tumor suppressor role, HIF-2 plays a distinct role in driving CRCC. In this study, we show that the HIF-1α E3 ligase HAF complexes with HIF-2α at DNA to promote HIF-2-dependent transcription through a mechanism relying upon HAF SUMOylation. HAF SUMOylation was induced by hypoxia, whereas HAF-mediated HIF-1α degradation was SUMOylation independent. HAF overexpression in mice increased CRCC growth and metastasis. Clinically, HAF overexpression was associated with poor prognosis. Taken together, our results show that HAF is a specific mediator of HIF-2 activation that is critical for CRCC development and morbidity. Copyright © 2014, American Association for Cancer Research.
    Cancer research. 11/2014;
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    ABSTRACT: HRC, SN, and M-CK are equally contributed first authors. TP, HL, and YHK are equally contributed corresponding authors. ABSTRACT Background Worldwide, gastric cancer (GC) is the fourth most common malignancy and the most common cancer in East Asia. Development of targeted therapies for this disease has focused on a few known oncogenes but has had limited effects. Objective To determine oncogenic mechanisms and novel therapeutic targets specific for GC by identifying commonly dysregulated genes from the tumours of both Asian-Pacific and Caucasian patients. Methods We generated transcriptomic profiles of 22 Caucasian GC tumours and their matched non-cancerous samples and performed an integrative analysis across different GC gene expression datasets. We examined the inhibition of commonly overexpressed oncogenes and their constituent signalling pathways by RNAi and/or pharmacological inhibition. Results Hepatocyte nuclear factor-4α (HNF4α) upregulation was a key signalling event in gastric tumours from both Caucasian and Asian patients, and HNF4α antagonism was antineoplastic. Perturbation experiments in GC tumour cell lines and xenograft models further demonstrated that HNF4α is downregulated by AMPKα signalling and the AMPK agonist metformin; blockade of HNF4α activity resulted in cyclin downregulation, cell cycle arrest and tumour growth inhibition. HNF4α also regulated WNT signalling through its target gene WNT5A, a potential prognostic marker of diffuse type gastric tumours. Conclusions Our results indicate that HNF4α is a targetable oncoprotein in GC, is regulated by AMPK signalling through AMPKα and resides upstream of WNT signalling. HNF4α may regulate 'metabolic switch' characteristic of a general malignant phenotype and its target WNT5A has potential prognostic values. The AMPKα-HNF4α-WNT5A signalling cascade represents a potentially targetable pathway for drug development. INTRODUCTION
    Gut 11/2014; · 10.73 Impact Factor
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    ABSTRACT: Although trastuzumab is a successful targeted therapy for breast cancer patients with tumors expressing HER2 (ERBB2), many patients eventually progress to drug resistance. Here, we identified subpathways differentially expressed between trastuzumab-resistant vs. -sensitive breast cancer cells, in conjunction with additional transcriptomic preclinical and clinical gene datasets, to rigorously identify overexpressed, resistance-associated genes. From this approach, we identified 32 genes reproducibly upregulated in trastuzumab resistance. 25 genes were upregulated in drug-resistant JIMT-1 cells, which also downregulated HER2 protein by >80% in the presence of trastuzumab. 24 genes were downregulated in trastuzumab-sensitive SKBR3 cells, Trastuzumab sensitivity was restored by siRNA knockdown of these genes in the resistant cells, and overexpression of 5 of the 25 genes was found in at least one of five refractory HER2+ breast cancer. In summary, our rigorous computational approach, followed by experimental validation, significantly implicate ATF4, CHEK2, ENAH, ICOSLG, and RAD51 as potential biomarkers of trastuzumab resistance. These results provide further proof-of-concept of our methodology for successfully identifying potential biomarkers and druggable signal pathways involved in tumor progression to drug resistance.
    Cancer Letters. 11/2014;
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    ABSTRACT: The translation of high-throughput gene expression data into biologically meaningful information remains a bottleneck. We developed a novel computational algorithm, PATHOME, for detecting differentially expressed biological pathways. This algorithm employs straightforward statistical tests to evaluate the significance of differential expression patterns along subpathways. Applying it to gene expression data sets of gastric cancer (GC), we compared its performance with those of other leading programs. Based on a literature-driven reference set, PATHOME showed greater consistency in identifying known cancer-related pathways. For the WNT pathway uniquely identified by PATHOME, we validated its involvement in gastric carcinogenesis through experimental perturbation of both cell lines and animal models. We identified HNF4α-WNT5A regulation in the cross-talk between the AMPK metabolic pathway and the WNT signaling pathway, and further identified WNT5A as a potential therapeutic target for GC. We have demonstrated PATHOME to be a powerful tool, with improved sensitivity for identifying disease-related dysregulated pathways.Oncogene advance online publication, 31 March 2014; doi:10.1038/onc.2014.80.
    Oncogene 03/2014; · 8.56 Impact Factor
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    ABSTRACT: Background & Aims: Farnesoid X receptor (FXR) is a bile acid nuclear receptor described through mouse knockout studies as a tumor suppressor for the development of colon adenocarcinomas. This study investigates the regulation of FXR in the development of human colon cancer. Methods: Immunohistochemistry of FXR in normal (n=238), polyps (n=32), and adenocarcinomas, staged I-IV (n= 43, 39, 68, and 9), of the colon and RT-PCR, reverse phase protein array (RPPA) and western blot analysis in 15 colon cancer cell lines, NR1H4 promoter methylation and mRNA expression in colon cancer samples from The Cancer Genome Atlas (TCGA), DNA methyltransferase inhibition, methyl-DNA immunoprecipitation (MeDIP), bisulfite sequencing and KRAS knock-down assessed were used to investigate FXR regulation in colon cancer development. Results: IHC and RT-qPCR revealed the expression and function of FXR was reduced in precancerous lesions and silenced in majority of stage I-IV tumors. FXR expression negatively correlated with PI3-kinase signaling and the epithelial-to-mesenchymal transition (EMT). The NR1H4 promoter is methylated in ~12% colon cancer TCGA samples, and methylation patterns segregate with tumor sub-types. Inhibition of DNA methylation and KRAS silencing both increased FXR expression. Conclusion: FXR expression is decreased early in human colon cancer progression and both DNA methylation and KRAS signaling may be contributing factors to FXR silencing. FXR potentially suppresses EMT and other oncogenic signaling cascades and restoration of FXR activity, by blocking silencing mechanisms or increasing residual FXR activity, represents promising therapeutic options for the treatment of colon cancer.
    AJP Gastrointestinal and Liver Physiology 10/2013; · 3.65 Impact Factor
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    ABSTRACT: An improved method for the synthesis of 17β-hydroxy-16α-iodo-wortmannin along with the first synthesis of 17β-hydroxy-16α-iodoPX866 and [(131)I] radiolabeled 17β-hydroxy-16α-[(131)I]iodo-wortmannin, as potential PET tracers for PI3K was also described. The differences between wortmannin and its iodo analogue were compared by covalently docking each structure to L833 in PI3K.
    Bioorganic & medicinal chemistry 06/2013; · 2.82 Impact Factor
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    ABSTRACT: Pancreatic cancer is characterized by a desmoplastic reaction that creates a dense fibroinflammatory microenvironment, promoting hypoxia and limiting cancer drug delivery due to decreased blood perfusion. Here we describe a novel tumor-stroma interaction that may help explain the prevalence of desmoplasia in this cancer. Specifically, we found that activation of HIF-1α by tumor hypoxia strongly activates secretion of the sonic hedgehog ligand SHH by cancer cells which in turn causes stromal fibroblasts to increase fibrous tissue deposition. In support of this finding, elevated levels of HIF-1α and SHH in pancreatic tumors were determined to be markers of decreased patient survival. Repeated cycles of hypoxia and desmoplasia amplified each other in a feed forward loop that made tumors more aggressive and resistant to therapy. This loop could be blocked by HIF-1α inhibition, which was sufficient to block SHH production and HH signaling. Taken together, our findings suggest that increased HIF-1α produced by hypoxic tumors triggers the desmoplasic reaction in pancreatic cancer, which is then amplified by a feed forward loop involving cycles of decreased blood flow and increased hypoxia. our findings strengthen the rationale for testing HIF inhibitors may therefore represent a novel therapeutic option for pancreatic cancer.
    Cancer Research 04/2013; · 9.28 Impact Factor
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    ABSTRACT: PURPOSE: Vemurafenib, a selective inhibitor of BRAFV600 has shown significant activity in BRAFV600 melanoma, but not in the <10% of metastatic BRAFV600 colorectal cancers (CRC), suggesting that studies of the unique hypermethylated phenotype and concurrent oncogenic activation of BRAFmut CRC may provide combinatorial strategies EXPERIMENTAL DESIGN: We performed comparative proteomic analysis of BRAFV600E melanoma and CRC cell lines, followed by correlation of PI3K pathway activation and sensitivity to the vemurafenib-analog PLX-4720. Pharmacologic inhibitors and siRNA were used in combination with PLX4720 to inhibit PI3K and methyltrasnferase in cell lines and murine models. RESULTS: Compared to melanoma, CRC lines demonstrate higher levels of PI3K/AKT pathway activation. CRC cell lines with mutations in PTEN or PIK3CA were less sensitive to growth inhibition by PLX4720 (P=0.03), and knockdown of PTEN expression in sensitive CRC cells reduced growth inhibition by the drug. Combined treatment of PLX4720 with PI3K inhibitors caused synergistic growth inhibition in BRAF-mutant CRC cells with both primary and secondary resistance. In addition, methyltransferase inhibition was synergistic with PLX4720 and decreased AKT activation. In vivo, PLX4720 combined with either inhibitors of AKT or methyltransferase demonstrated greater tumor growth inhibition than PLX4720 alone. Clones with acquired resistance to PLX4720 in vitro demonstrated PI3K/AKT activation with EGFR or KRAS amplification. CONCLUSIONS: We demonstrate that activation of the PI3K/AKT pathway is a mechanism of both innate and acquired resistance to BRAF inhibitors in BRAFV600E CRC, and suggest combinatorial approaches to improve outcomes in this poor prognosis subset of patients.
    Clinical Cancer Research 12/2012; · 7.84 Impact Factor
  • Scott Kopetz, Robert Lemos, Garth Powis
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    ABSTRACT: Compared with xenografts from previously established cell lines, patient-derived xenografts may more faithfully recapitulate the molecular diversity, cellular heterogeneity, and histology seen in patient tumors, although other limitations of murine models remain. The ability of these models to inform clinical development and answer mechanistic questions will determine their ultimate use. Clin Cancer Res; 18(19); 5160-2. ©2012 AACR.
    Clinical Cancer Research 08/2012; 18(19):5160-2. · 7.84 Impact Factor
  • Mei Yee Koh, Garth Powis
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    ABSTRACT: Hypoxia is an inadequate oxygen supply to tissues and cells, which can restrict their function. The hypoxic response is primarily mediated by the hypoxia-inducible transcription factors, HIF-1 and HIF-2, which have both overlapping and unique target genes. HIF target gene activation is highly context specific and is not a reliable indicator of which HIF-α isoform is active. For example, in some cell lines, the individual HIFs have specific temporal and functional roles: HIF-1 drives the initial response to hypoxia (<24h) and HIF-2 drives the chronic response (>24h). Here, we review the significance of the HIF switch and the relation between HIF-1 and HIF-2 under both physiological and pathophysiological conditions.
    Trends in Biochemical Sciences 07/2012; 37(9):364-72. · 13.08 Impact Factor
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    ABSTRACT: Gd-LC6-SH is a thiol-bearing DOTA complex of gadolinium designed to bind plasma albumin at the conserved Cys(34) site. The binding of Gd-LC6-SH shows sensitivity to the presence of competing thiols. We hypothesized that Gd-LC6-SH could provide magnetic resonance imaging (MRI) enhancement that is sensitive to tumor redox state and that the prolonged retention of albumin-bound Gd-LC6-SH in vivo can be exploited to identify a saturating dose above which the shortening of MRI longitudinal relaxation time (T(1)) of tissue is insensitive to the injected gadolinium dose. In the Mia-PaCa-2 pancreatic tumor xenograft model in SCID mice, both the small-molecule Gd-DTPA-BMA and the macromolecule Galbumin MRI contrast agents produced dose-dependent decreases in tumor T(1). By contrast, the decreases in tumor T(1) provided by Gd-LC6-SH at 0.05 and 0.1 mmol/kg were not significantly different at longer times after injection. SCID mice bearing Mia-PaCa-2 or NCI-N87 tumor xenografts were treated with either the glutathione synthesis inhibitor buthionine sulfoximine or the thiol-oxidizing anticancer drug Imexon, respectively. In both models, there was a significantly greater increase in tumor R(1) (=1/T(1)) 60 minutes after injection of Gd-LC6-SH in drug-treated animals relative to saline-treated controls. In addition, Mercury Orange staining for nonprotein sulfhydryls was significantly decreased by drug treatment relative to controls in both tumor models. In summary, these studies show that thiol-bearing complexes of gadolinium such as Gd-LC6-SH can serve as redox-sensitive MRI contrast agents for detecting differences in tumor redox status and can be used to evaluate the effects of redox-active drugs.
    Translational oncology 06/2012; 5(3):190-9. · 3.40 Impact Factor
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    ABSTRACT: Gastric cancer is the most common cancer in Asia and most developing countries. Despite the use of multimodality therapeutics, it remains the second leading cause of cancer death in the world. To identify the molecular underpinnings of gastric cancer in the Asian population, we applied an RNA-sequencing approach to gastric tumor and noncancerous specimens, generating 680 million informative short reads to quantitatively characterize the entire transcriptome of gastric cancer (including mRNAs and miRNAs). A multilayer analysis was then developed to identify multiple types of transcriptional aberrations associated with different stages of gastric cancer, including differentially expressed mRNAs, recurrent somatic mutations, and key differentially expressed miRNAs. Through this approach, we identified the central metabolic regulator AMP-activated protein kinase (AMPK)α as a potential functional target in Asian gastric cancer. Furthermore, we experimentally showed the translational relevance of this gene as a potential therapeutic target for early-stage gastric cancer in Asian patients. Together, our findings not only provide a valuable information resource for identifying and elucidating the molecular mechanisms of Asian gastric cancer, but also represent a general integrative framework to develop more effective therapeutic targets.
    Cancer Research 03/2012; 72(10):2512-21. · 9.28 Impact Factor
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    ABSTRACT: Oxidative protein folding in the endoplasmic reticulum (ER) requires strict regulation of redox homeostasis. Disruption of the lumenal redox balance induces an integrated ER stress response that is associated with reduced protein translation, increased chaperone activity, and ultimately cell death. Imexon is a small-molecule chemotherapeutic agent that has been shown to bind glutathione (GSH) and induce oxidative stress in tumor cells; however, the mechanism of cytotoxicity is not well understood. In this report, we investigate the effects of imexon on the integrated ER stress response in pancreatic carcinoma cells. Acute exposure to imexon induces an ER stress response characterized by accumulation of the oxidized form of the oxidoreductase Ero1α, phosphorylation of eIF2α, and inhibition of protein synthesis. An RNA interference chemosensitization screen identified the eukaryotic translation initiation factor eIF2B5 as a target that enhanced imexon-induced growth inhibition of MiaPaCa-2 pancreatic cancer cells, but did not significantly augment the effects of imexon on protein synthesis. Concurrent reduction of intracellular thiols with N-acetyl cysteine reversed imexon activity, however cotreatment with superoxide scavengers had no effect, suggesting thiol binding may be a primary component of the oxidative effects of imexon. Moreover, the data suggest that disruption of the redox balance in the ER is a potential therapeutic target.
    Molecular Cancer Research 02/2012; 10(3):392-400. · 4.35 Impact Factor
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    ABSTRACT: Mutations in the v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) play a critical role in cancer cell growth and resistance to therapy. Most mutations occur at codons 12 and 13. In colorectal cancer, the presence of any mutant KRas amino acid substitution is a negative predictor of patient response to targeted therapy. However, in non-small cell lung cancer (NSCLC), the evidence that KRAS mutation is a predictive factor is conflicting. We used data from a molecularly targeted clinical trial for 215 patients with tissues available out of 268 evaluable patients with refractory NSCLC to examine associations between specific mutant KRas proteins and progression-free survival and tumor gene expression. Transcriptome microarray studies of patient tumor samples and reverse-phase protein array studies of a panel of 67 NSCLC cell lines with known substitutions in KRas and in immortalized human bronchial epithelial cells stably expressing different mutant KRas proteins were used to investigate signaling pathway activation. Molecular modeling was used to study the conformations of wild-type and mutant KRas proteins. Kaplan-Meier curves and Cox regression were used to analyze survival data. All statistical tests were two-sided. Patients whose tumors had either mutant KRas-Gly12Cys or mutant KRas-Gly12Val had worse progression-free survival compared with patients whose tumors had other mutant KRas proteins or wild-type KRas (P = .046, median survival = 1.84 months) compared with all other mutant KRas (median survival = 3.35 months) or wild-type KRas (median survival = 1.95 months). NSCLC cell lines with mutant KRas-Gly12Asp had activated phosphatidylinositol 3-kinase (PI-3-K) and mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) signaling, whereas those with mutant KRas-Gly12Cys or mutant KRas-Gly12Val had activated Ral signaling and decreased growth factor-dependent Akt activation. Molecular modeling studies showed that different conformations imposed by mutant KRas may lead to altered association with downstream signaling transducers. Not all mutant KRas proteins affect patient survival or downstream signaling in a similar way. The heterogeneous behavior of mutant KRas proteins implies that therapeutic interventions may need to take into account the specific mutant KRas expressed by the tumor.
    CancerSpectrum Knowledge Environment 02/2012; 104(3):228-39. · 14.07 Impact Factor
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    Genome Biology 09/2011; 12(1). · 10.30 Impact Factor
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    Radiation Research 09/2011; 176(3):e0016-21. · 2.70 Impact Factor
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    ABSTRACT: Most solid tumors and their metastases experience periods of low oxygen or hypoxia, which is of major clinical significance as it promotes both tumor progression and resistance to therapy. Critical mediators of the hypoxic response are the hypoxia-inducible factors HIF-1α and HIF-2α. The HIFs are nonredundant and regulate both overlapping and unique downstream target genes. Here, we describe a novel mechanism for the switch between HIF-1α- and HIF-2α-dependent transcription during tumor hypoxia caused by the hypoxia associated factor (HAF). HAF is overexpressed in a variety of tumors and its levels are decreased during acute hypoxia, but increased following prolonged hypoxia. We have previously identified HAF as an E3 ubiquitin ligase that binds and ubiquitinates HIF-1α by an oxygen and pVHL-independent mechanism, thus targeting HIF-1α for proteasomal degradation. Here, we show that HAF also binds to HIF-2α, but at a different site than HIF-1α, and increases HIF-2α transactivation without causing its degradation. HAF, thus, switches the hypoxic response of the cancer cell from HIF-1α-dependent to HIF-2α-dependent transcription and activates genes involved in invasion such as MMP9, PAI-1, and the stem cell factor OCT-3/4. The switch to HIF-2α-dependent gene expression caused by HAF also promotes an enriched tumor stem cell population, resulting in highly aggressive tumors in vivo. Thus, HAF, by causing a switch from a HIF-1α- to HIF-2α-dependent response to hypoxia, provides a mechanism for more aggressive growth of tumors under prolonged hypoxia.
    Cancer Research 06/2011; 71(11):4015-27. · 9.28 Impact Factor
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    ABSTRACT: Several small molecules that inhibit the PI3 kinase (PI3K)-Akt signaling pathway are in clinical development. Although many of these molecules have been effective in preclinical models, it remains unclear whether this strategy alone will be sufficient to interrupt the molecular events initiated and maintained by signaling along the pathways because of the activation of other pathways that compensate for the inhibition of the targeted kinase. In this study, we performed a synthetic lethality screen to identify genes or pathways whose inactivation, in combination with the PI3K inhibitors PX-866 and NVPBEZ-235, might result in a lethal phenotype in glioblastoma multiforme (GBM) cells. We screened GBM cells (U87, U251, and T98G) with a large-scale, short hairpin RNA library (GeneNet), which contains 43 800 small interfering RNA sequences targeting 8500 well-characterized human genes. To decrease off-target effects, we selected overlapping genes among the 3 cell lines that synergized with PX-866 to induce cell death. To facilitate the identification of potential targets, we used a GSE4290 dataset and The Cancer Genome Atlas GBM dataset, identifying 15 target genes overexpressed in GBM tissues. We further analyzed the selected genes using Ingenuity Pathway Analysis software and showed that the 15 genes were closely related to cancer-promoting pathways, and a highly interconnected network of aberrations along the MYC, P38MAPK, and ERK signaling pathways were identified. Our findings suggest that inhibition of these pathways might increase tumor sensitivity to PX-866 and therefore represent a potential clinical therapeutic strategy.
    Neuro-Oncology 04/2011; 13(4):367-75. · 6.18 Impact Factor
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    ABSTRACT: Hypoxia-inducible factor 1 (HIF-1) promotes cancer cell survival and tumor progression. The specific role played by HIF-1 and tumor-stromal interactions toward determining tumor resistance to radiation treatment remains undefined. We applied a multimodality preclinical imaging platform to mechanistically characterize tumor response to radiation, with a focus on HIF-1-dependent resistance pathways. C6 glioma and HN5 human squamous carcinoma cells were stably transfected with a dual HIF-1 signaling reporter construct (dxHRE-tk/eGFP-cmvRed2XPRT). Reporter cells were serially interrogated in vitro before and after irradiation as monolayer and multicellular spheroid cultures and as subcutaneous xenografts in nu/nu mice. In vitro, single-dose irradiation of C6 and HN5 reporter cells modestly impacted HIF-1 signaling in normoxic monolayers and inhibited HIF-1 signaling in maturing spheroids. In contrast, irradiation of C6 or HN5 reporter xenografts with 8 Gy in vivo elicited marked upregulation of HIF-1 signaling and downstream proangiogenic signaling at 48 hours which preceded recovery of tumor growth. In situ ultrasound imaging and dynamic contrast-enhanced (DCE) MRI indicated that HIF-1 signaling followed acute disruption of stromal vascular function. High-resolution positron emission tomography and dual-contrast DCE-MRI of immobilized dorsal skin window tumors confirmed postradiotherapy HIF-1 signaling to spatiotemporally coincide with impaired stromal vascular function. Targeted disruption of HIF-1 signaling established this pathway to be a determinant of tumor radioresistance. Our results illustrate that tumor radioresistance is mediated by a capacity to compensate for stromal vascular disruption through HIF-1-dependent proangiogenic signaling and that clinically relevant vascular imaging techniques can spatially define mechanisms associated with tumor irradiation.
    Molecular Cancer Research 03/2011; 9(3):259-70. · 4.35 Impact Factor
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    ABSTRACT: Polynuclear platinum compounds are more effective at killing glioblastoma cells than cisplatin, work by a different mechanism, and typically do not induce high levels of apoptosis at early time points after exposure. Here, we tested the hypothesis that combining BBR3610, the most potent polynuclear platinum, with a phosphoinositide-3-kinase (PI3K) inhibitor would promote apoptosis and enhance the impact on glioblastoma cells. The PI3K pathway is commonly activated in glioblastoma and promotes tumor cell survival, suggesting that its inhibition would make cells more sensitive to cytotoxic agents. We chose PX-866 as a PI3K inhibitor as it is a clinically promising agent being evaluated for brain tumor therapy. Combining BBR3610 and PX-866 resulted in synergistic killing of cultured glioma cells and an extension of survival in an orthotopic xenograft animal model. Both agents alone induced autophagy, and this appeared to be saturated, because when they were combined no additional autophagy was observed. However, the combination of PX-866 and BBR3610 did induce statistically significant increases in the level of apoptosis, associated with a reduction in pAkt and pBad, as well as inhibition of transwell migration. We conclude that combining polynuclear platinums with PI3K inhibitors has translational potential and alters the cellular response to include early apoptosis.
    International Journal of Cancer 02/2011; 128(4):787-96. · 6.20 Impact Factor

Publication Stats

10k Citations
1,441.25 Total Impact Points


  • 2006–2013
    • University of Texas MD Anderson Cancer Center
      • Department of Experimental Therapeutics
      Houston, TX, United States
    • University of Oxford
      Oxford, England, United Kingdom
  • 2001–2010
    • University of Pittsburgh
      • Department of Chemistry
      Pittsburgh, Pennsylvania, United States
  • 1997–2010
    • Uppsala University
      • Department of Chemistry - BMC
      Uppsala, Uppsala, Sweden
    • Georgetown University
      • • Institute for Cognitive and Computational Sciences
      • • Department of Neurology
      Washington, Washington, D.C., United States
  • 1993–2010
    • The University of Arizona
      • • College of Medicine
      • • Cancer Center
      Tucson, Arizona, United States
    • University of Washington Seattle
      • Department of Pharmacology
      Seattle, WA, United States
    • University of Minnesota Twin Cities
      • Department of Anesthesiology
      Minneapolis, MN, United States
  • 2008
    • University of Houston
      Houston, Texas, United States
  • 2004
    • University of South Florida
      Tampa, Florida, United States
  • 1992–2004
    • Arizona Research Center
      Phoenix, Arizona, United States
  • 1988–2001
    • Georgia Institute of Technology
      • School of Chemistry and Biochemistry
      Atlanta, GA, United States
  • 1997–1999
    • University of Regina
      • Department of Chemistry and Biochemistry
      Regina, Saskatchewan, Canada
  • 1996
    • New York University
      • Department of Cell Biology
      New York City, NY, United States
  • 1981–1995
    • Mayo Foundation for Medical Education and Research
      • • Department of Pharmacology
      • • Department of Anesthesiology
      Rochester, Michigan, United States
  • 1994
    • Research Triangle Park Laboratories, Inc.
      Raleigh, North Carolina, United States
  • 1981–1991
    • Mayo Clinic - Rochester
      • • Department of Immunology
      • • Department of Oncology
      Rochester, Minnesota, United States
  • 1987
    • Oklahoma State University - Oklahoma City
      Oklahoma City, Oklahoma, United States
  • 1986
    • City of Hope National Medical Center
      Duarte, California, United States
    • National Cancer Institute (USA)
      • Developmental Therapeutics Program
      Maryland, United States
  • 1977
    • Yale-New Haven Hospital
      New Haven, Connecticut, United States