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Lehman SL, Wechsler T, Schwartz K, Brown LE, Porco JA, Devine WG, Pelletier J, Shankavaram UT, Camphausen K, Tofilon PJ. Inhibition of the Translation Initiation Factor eIF4A Enhances Tumor Cell Radiosensitivity. Mol Cancer Ther 2022; 21:1406-1414. [PMID: 35732578 PMCID: PMC9452469 DOI: 10.1158/1535-7163.mct-22-0037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 04/12/2022] [Accepted: 06/16/2022] [Indexed: 11/16/2022]
Abstract
A fundamental component of cellular radioresponse is the translational control of gene expression. Because a critical regulator of translational control is the eukaryotic translation initiation factor 4F (eIF4F) cap binding complex, we investigated whether eIF4A, the RNA helicase component of eIF4F, can serve as a target for radiosensitization. Knockdown of eIF4A using siRNA reduced translational efficiency, as determined from polysome profiles, and enhanced tumor cell radiosensitivity as determined by clonogenic survival. The increased radiosensitivity was accompanied by a delayed dispersion of radiation-induced γH2AX foci, suggestive of an inhibition of DNA double-strand break repair. Studies were then extended to (-)-SDS-1-021, a pharmacologic inhibitor of eIF4A. Treatment of cells with the rocaglate (-)-SDS-1-021 resulted in a decrease in translational efficiency as well as protein synthesis. (-)-SDS-1-021 treatment also enhanced the radiosensitivity of tumor cell lines. This (-)-SDS-1-021-induced radiosensitization was accompanied by a delay in radiation-induced γH2AX foci dispersal, consistent with a causative role for the inhibition of double-strand break repair. In contrast, although (-)-SDS-1-021 inhibited translation and protein synthesis in a normal fibroblast cell line, it had no effect on radiosensitivity of normal cells. Subcutaneous xenografts were then used to evaluate the in vivo response to (-)-SDS-1-021 and radiation. Treatment of mice bearing subcutaneous xenografts with (-)-SDS-1-021 decreased tumor translational efficiency as determined by polysome profiles. Although (-)-SDS-1-021 treatment alone had no effect on tumor growth, it significantly enhanced the radiation-induced growth delay. These results suggest that eIF4A is a tumor-selective target for radiosensitization.
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Affiliation(s)
| | | | | | - Lauren E Brown
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, Massachusetts
| | - John A Porco
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, Massachusetts
| | - William G Devine
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, Massachusetts
| | - Jerry Pelletier
- Department of Biochemistry, Oncology and Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada
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2
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Meattini I, Livi L, Lorito N, Becherini C, Bacci M, Visani L, Fozza A, Belgioia L, Loi M, Mangoni M, Lambertini M, Morandi A. Integrating radiation therapy with targeted treatments for breast cancer: from bench to bedside. Cancer Treat Rev 2022; 108:102417. [PMID: 35623219 DOI: 10.1016/j.ctrv.2022.102417] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 05/14/2022] [Accepted: 05/17/2022] [Indexed: 11/02/2022]
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3
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Lehman SL, Wilson ED, Camphausen K, Tofilon PJ. Translation Initiation Machinery as a Tumor Selective Target for Radiosensitization. Int J Mol Sci 2021; 22:ijms221910664. [PMID: 34639005 PMCID: PMC8508945 DOI: 10.3390/ijms221910664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/22/2021] [Accepted: 09/29/2021] [Indexed: 01/04/2023] Open
Abstract
Towards improving the efficacy of radiotherapy, one approach is to target the molecules and processes mediating cellular radioresponse. Along these lines, translational control of gene expression has been established as a fundamental component of cellular radioresponse, which suggests that the molecules participating in this process (i.e., the translational machinery) can serve as determinants of radiosensitivity. Moreover, the proteins comprising the translational machinery are often overexpressed in tumor cells suggesting the potential for tumor specific radiosensitization. Studies to date have shown that inhibiting proteins involved in translation initiation, the rate-limiting step in translation, specifically the three members of the eIF4F cap binding complex eIF4E, eIF4G, and eIF4A as well as the cap binding regulatory kinases mTOR and Mnk1/2, results in the radiosensitization of tumor cells. Because ribosomes are required for translation initiation, inhibiting ribosome biogenesis also appears to be a strategy for radiosensitization. In general, the radiosensitization induced by targeting the translation initiation machinery involves inhibition of DNA repair, which appears to be the consequence of a reduced expression of proteins critical to radioresponse. The availability of clinically relevant inhibitors of this component of the translational machinery suggests opportunities to extend this approach to radiosensitization to patient care.
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Hintelmann K, Kriegs M, Rothkamm K, Rieckmann T. Improving the Efficacy of Tumor Radiosensitization Through Combined Molecular Targeting. Front Oncol 2020; 10:1260. [PMID: 32903756 PMCID: PMC7438822 DOI: 10.3389/fonc.2020.01260] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 06/18/2020] [Indexed: 12/11/2022] Open
Abstract
Chemoradiation, either alone or in combination with surgery or induction chemotherapy, is the current standard of care for most locally advanced solid tumors. Though chemoradiation is usually performed at the maximum tolerated doses of both chemotherapy and radiation, current cure rates are not satisfactory for many tumor entities, since tumor heterogeneity and plasticity result in chemo- and radioresistance. Advances in the understanding of tumor biology, a rapidly growing number of molecular targeting agents and novel technologies enabling the in-depth characterization of individual tumors, have fuelled the hope of entering an era of precision oncology, where each tumor will be treated according to its individual characteristics and weaknesses. At present though, molecular targeting approaches in combination with radiotherapy or chemoradiation have not yet proven to be beneficial over standard chemoradiation treatment in the clinical setting. A promising approach to improve efficacy is the combined usage of two targeting agents in order to inhibit backup pathways or achieve a more complete pathway inhibition. Here we review preclinical attempts to utilize such dual targeting strategies for future tumor radiosensitization.
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Affiliation(s)
- Katharina Hintelmann
- Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Hamburg, Germany.,Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Malte Kriegs
- Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Kai Rothkamm
- Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Thorsten Rieckmann
- Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Hamburg, Germany.,Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Hamburg, Germany
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5
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Maimaitili Y, Inase A, Miyata Y, Kitao A, Mizutani Y, Kakiuchi S, Shimono Y, Saito Y, Sonoki T, Minami H, Matsuoka H. An mTORC1/2 kinase inhibitor enhances the cytotoxicity of gemtuzumab ozogamicin by activation of lysosomal function. Leuk Res 2018; 74:68-74. [PMID: 30300823 DOI: 10.1016/j.leukres.2018.09.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 09/25/2018] [Accepted: 09/29/2018] [Indexed: 11/18/2022]
Abstract
Gemtuzumab ozogamicin (GO), the first antibody-drug conjugate (ADC), has attracted the interest of hematologists because more than 90% of acute myeloid leukemia (AML) blasts express its target, CD33. Although GO and subsequently developed ADCs depend on lysosomes for activation, lysosome number and activity in tumor cells has not been well elucidated. In this study, we investigated whether an mTORC1/2 kinase inhibitor, PP242, which was reported to activate lysosomal function, potentiates the cytotoxicity of GO in AML cells. Eight AML cell lines (U937, THP-1, SKM-1, SKK-1, SKNO-1, HL-60, MARIMO and KO52) were treated with GO and PP242. The cytotoxic effect of GO was enhanced by concurrent treatment with a non-cytotoxic concentration (500 nM) of PP242 in most cell lines, except MARIMO and KO52 cells. We then used LysoTracker to label acidic lysosomes in U937, THP-1, SKM-1, MARIMO and KO52 cells. LysoTracker fluorescence was dramatically increased by treatment with PP242 in U937, THP-1 and SKM-1 cells, and the intensified fluorescence was retained with PP242 + GO. In contrast, PP242 did not induce a significant increase in fluorescence in MARIMO cells, consistent with the lack of combinatory cytotoxicity. LysoTracker fluorescence was also increased by PP242 in KO52 cells, which have been reported to strongly express multidrug resistance (MDR). Further, PP242 suppressed GO-induced Chk1 activation and G2/M cell cycle arrest, which in turn triggered cell cycle promotion and cell death. These results indicate that inhibition of mTORC1/2 kinase by PP242 enhanced the cytotoxicity of GO by increasing lysosomal compartments and promoting the cell cycle via suppression of GO-induced Chk1 activation. This combination may represent an attractive new therapeutic strategy for the treatment of leukemia.
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Affiliation(s)
- Yimamu Maimaitili
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Aki Inase
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yoshiharu Miyata
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Akihito Kitao
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yu Mizutani
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Seiji Kakiuchi
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yohei Shimono
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan; Division of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yasuyuki Saito
- Division of Molecular and Cellular Signaling, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Takashi Sonoki
- Division of Hematology/Oncology, Wakayama Medical University, Wakayama, Japan
| | - Hironobu Minami
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroshi Matsuoka
- Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
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Eke I, Makinde AY, Aryankalayil MJ, Sandfort V, Palayoor ST, Rath BH, Liotta L, Pierobon M, Petricoin EF, Brown MF, Stommel JM, Ahmed MM, Coleman CN. Exploiting Radiation-Induced Signaling to Increase the Susceptibility of Resistant Cancer Cells to Targeted Drugs: AKT and mTOR Inhibitors as an Example. Mol Cancer Ther 2018; 17:355-367. [PMID: 28802252 PMCID: PMC5805592 DOI: 10.1158/1535-7163.mct-17-0262] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/21/2017] [Accepted: 08/01/2017] [Indexed: 12/13/2022]
Abstract
Implementing targeted drug therapy in radio-oncologic treatment regimens has greatly improved the outcome of cancer patients. However, the efficacy of molecular targeted drugs such as inhibitory antibodies or small molecule inhibitors essentially depends on target expression and activity, which both can change during the course of treatment. Radiotherapy has previously been shown to activate prosurvival pathways, which can help tumor cells to adapt and thereby survive treatment. Therefore, we aimed to identify changes in signaling induced by radiation and evaluate the potential of targeting these changes with small molecules to increase the therapeutic efficacy on cancer cell survival. Analysis of "The Cancer Genome Atlas" database disclosed a significant overexpression of AKT1, AKT2, and MTOR genes in human prostate cancer samples compared with normal prostate gland tissue. Multifractionated radiation of three-dimensional-cultured prostate cancer cell lines with a dose of 2 Gy/day as a clinically relevant schedule resulted in an increased protein phosphorylation and enhanced protein-protein interaction between AKT and mTOR, whereas gene expression of AKT, MTOR, and related kinases was not altered by radiation. Similar results were found in a xenograft model of prostate cancer. Pharmacologic inhibition of mTOR/AKT signaling after activation by multifractionated radiation was more effective than treatment prior to radiotherapy. Taken together, our findings provide a proof-of-concept that targeting signaling molecules after activation by radiotherapy may be a novel and promising treatment strategy for cancers treated with multifractionated radiation regimens such as prostate cancer to increase the sensitivity of tumor cells to molecular targeted drugs. Mol Cancer Ther; 17(2); 355-67. ©2017 AACRSee all articles in this MCT Focus section, "Developmental Therapeutics in Radiation Oncology."
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Affiliation(s)
- Iris Eke
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.
| | - Adeola Y Makinde
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Molykutty J Aryankalayil
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Veit Sandfort
- Department of Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, Maryland
| | - Sanjeewani T Palayoor
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Barbara H Rath
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Lance Liotta
- Center for Applied Proteomics and Molecular Medicine, George Mason University, Manassas, Virginia
| | - Mariaelena Pierobon
- Center for Applied Proteomics and Molecular Medicine, George Mason University, Manassas, Virginia
| | - Emanuel F Petricoin
- Center for Applied Proteomics and Molecular Medicine, George Mason University, Manassas, Virginia
| | - Matthew F Brown
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Jayne M Stommel
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Mansoor M Ahmed
- Radiation Research Program, National Cancer Institute, National Institutes of Health, Rockville, Maryland
| | - C Norman Coleman
- Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
- Radiation Research Program, National Cancer Institute, National Institutes of Health, Rockville, Maryland
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7
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Elkon R, Loayza-Puch F, Korkmaz G, Lopes R, van Breugel PC, Bleijerveld OB, Altelaar AFM, Wolf E, Lorenzin F, Eilers M, Agami R. Myc coordinates transcription and translation to enhance transformation and suppress invasiveness. EMBO Rep 2015; 16:1723-36. [PMID: 26538417 PMCID: PMC4687422 DOI: 10.15252/embr.201540717] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 09/21/2015] [Indexed: 12/15/2022] Open
Abstract
c‐Myc is one of the major human proto‐oncogenes and is often associated with tumor aggression and poor clinical outcome. Paradoxically, Myc was also reported as a suppressor of cell motility, invasiveness, and metastasis. Among the direct targets of Myc are many components of the protein synthesis machinery whose induction results in an overall increase in protein synthesis that empowers tumor cell growth. At present, it is largely unknown whether beyond the global enhancement of protein synthesis, Myc activation results in translation modulation of specific genes. Here, we measured Myc‐induced global changes in gene expression at the transcription, translation, and protein levels and uncovered extensive transcript‐specific regulation of protein translation. Particularly, we detected a broad coordination between regulation of transcription and translation upon modulation of Myc activity and showed the connection of these responses to mTOR signaling to enhance oncogenic transformation and to the TGFβ pathway to modulate cell migration and invasiveness. Our results elucidate novel facets of Myc‐induced cellular responses and provide a more comprehensive view of the consequences of its activation in cancer cells.
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Affiliation(s)
- Ran Elkon
- Division of Biological Stress Response, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Fabricio Loayza-Puch
- Division of Biological Stress Response, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Gozde Korkmaz
- Division of Biological Stress Response, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Rui Lopes
- Division of Biological Stress Response, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Pieter C van Breugel
- Division of Biological Stress Response, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Onno B Bleijerveld
- Mass Spectrometry/Proteomics Facility, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - A F Maarten Altelaar
- Mass Spectrometry/Proteomics Facility, The Netherlands Cancer Institute, Amsterdam, The Netherlands Biomolecular Mass Spectrometry and Proteomics Group, Bijvoet Center for Biomolecular Research, Utrecht Institute for Pharmaceutical Sciences Utrecht University, Utrecht, The Netherlands Netherlands Proteomics Centre Cancer Genomics Centre, Utrecht, The Netherlands
| | - Elmar Wolf
- Biozentrum der Universität Würzburg Theodor Boveri Institut Am Hubland, Würzburg, Germany
| | - Francesca Lorenzin
- Biozentrum der Universität Würzburg Theodor Boveri Institut Am Hubland, Würzburg, Germany
| | - Martin Eilers
- Biozentrum der Universität Würzburg Theodor Boveri Institut Am Hubland, Würzburg, Germany
| | - Reuven Agami
- Division of Biological Stress Response, The Netherlands Cancer Institute, Amsterdam, The Netherlands Erasmus MC, Rotterdam University, Rotterdam, The Netherlands
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8
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Leiker AJ, DeGraff W, Choudhuri R, Sowers AL, Thetford A, Cook JA, Van Waes C, Mitchell JB. Radiation Enhancement of Head and Neck Squamous Cell Carcinoma by the Dual PI3K/mTOR Inhibitor PF-05212384. Clin Cancer Res 2015; 21:2792-801. [PMID: 25724523 DOI: 10.1158/1078-0432.ccr-14-3279] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/23/2015] [Indexed: 11/16/2022]
Abstract
PURPOSE Radiation remains a mainstay for the treatment of nonmetastatic head and neck squamous cell carcinoma (HNSCC), a malignancy characterized by a high rate of PI3K/mTOR signaling axis activation. We investigated the ATP-competitive dual PI3K/mTOR inhibitor, PF-05212384, as a radiosensitizer in preclinical HNSCC models. EXPERIMENTAL DESIGN Extent of radiation enhancement of two HNSCC cell lines (UMSCC1-wtP53 and UMSCC46-mtP53) and normal human fibroblast (1522) was assessed by in vitro clonogenic assay with appropriate target inhibition verified by immunoblotting. Radiation-induced DNA damage repair was evaluated by γH2AX Western blots with the mechanism of DNA double-strand break repair abrogation investigated by cell cycle analysis, immunoblotting, and RT-PCR. PF-05212384 efficacy in vivo was assessed by UMSCC1 xenograft tumor regrowth delay, xenograft lysate immunoblotting, and tissue section immunohistochemistry. RESULTS PF-05212384 effectively inhibited PI3K and mTOR, resulting in significant radiosensitization of exponentially growing and plateau-phase cells with 24-hour treatment following irradiation, and variable radiation enhancement with 24-hour treatment before irradiation. Tumor cells radiosensitized to a greater extent than normal human fibroblasts. Postirradiation PF-05212384 treatment delays γH2AX foci resolution. PF-05212384 24-hour exposure resulted in an evident G1-S phase block in p53-competent cells. Fractionated radiation plus i.v. PF-05212384 synergistically delayed nude mice bearing UMSCC1 xenograft regrowth, with potential drug efficacy biomarkers identified, including pS6, pAkt, p4EBP1, and Ki67. CONCLUSIONS Taken together, our results of significant radiosensitization both in vitro and in vivo validate the PI3K/mTOR axis as a radiation modification target and PF-05212384 as a potential clinical radiation modifier of nonmetastatic HNSCC.
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Affiliation(s)
- Andrew J Leiker
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland. Medical Research Scholars Program, NIH, Bethesda, Maryland
| | - William DeGraff
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - Rajani Choudhuri
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - Anastasia L Sowers
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - Angela Thetford
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - John A Cook
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - Carter Van Waes
- Head and Neck Surgery Branch, NIDCD, NIH, Bethesda, Maryland
| | - James B Mitchell
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
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9
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Abstract
The mammalian target of rapamycin (mTOR) has emerged as a potential target for drug development, particularly due to the fact that it plays such a crucial role in cancer biology. In addition, next-generation mTOR inhibitors have become available, marking an exciting new phase in mTOR-based therapy. However, the verdict on their therapeutic efectiveness remains unclear. Here we review phosphatidylinositol-3-kinase (PI3K)/Akt/mTOR signaling as one of the primary mechanisms for sustaining tumor outgrowth and metastasis, recent advances in the development of mTOR inhibitors, and current studies addressing mTOR activation/inhibition in colorectal cancer (CRC). We will also discuss our recent comparative study of diferent mTOR inhibitors in a population of colon cancer stem cells (CSCs), and current major challenges for achieving individualized drug therapy using kinase inhibitors.
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10
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Hayman TJ, Wahba A, Rath BH, Bae H, Kramp T, Shankavaram UT, Camphausen K, Tofilon PJ. The ATP-competitive mTOR inhibitor INK128 enhances in vitro and in vivo radiosensitivity of pancreatic carcinoma cells. Clin Cancer Res 2014; 20:110-9. [PMID: 24198241 PMCID: PMC3947297 DOI: 10.1158/1078-0432.ccr-13-2136] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Radiotherapy remains a primary treatment modality for pancreatic carcinoma, a tumor characterized by aberrant mTOR activity. Given the regulatory role of mTOR in gene translation, in this study, we defined the effects of the clinically relevant, ATP-competitive mTOR inhibitor, INK128 on the radiosensitivity of pancreatic carcinoma cell lines. EXPERIMENTAL DESIGN Clonogenic survival was used to determine the effects of INK128 on in vitro radiosensitivity of three pancreatic carcinoma cell lines and a normal fibroblast cell line with mTOR activity defined using immunoblots. DNA double-strand breaks were evaluated according to γH2AX foci. The influence of INK128 on radiation-induced gene translation was determined by microarray analysis of polysome-bound mRNA. Leg tumor xenografts grown from pancreatic carcinoma cells were evaluated for mTOR activity, eIF4F cap complex formation, and tumor growth delay. RESULTS INK128, while inhibiting mTOR activity in each of the cell lines, enhanced the in vitro radiosensitivity of the pancreatic carcinoma cells but had no effect on normal fibroblasts. The dispersal of radiation-induced γH2AX foci was inhibited in pancreatic carcinoma cells by INK128 as were radiation-induced changes in gene translation. Treatment of mice with INK128 resulted in an inhibition of mTOR activity as well as cap complex formation in tumor xenografts. Whereas INK128 alone had no effect of tumor growth rate, it enhanced the tumor growth delay induced by single and fractionated doses of radiation. CONCLUSION These results indicate that mTOR inhibition induced by INK128 enhances the radiosensitivity of pancreatic carcinoma cells and suggest that this effect involves the inhibition of DNA repair.
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Affiliation(s)
- Thomas J. Hayman
- University of South Florida Morsani College of Medicine, Tampa, FL
- Radiation Oncology Branch, National Cancer Institute, Bethesda, MD
| | - Amy Wahba
- Radiation Oncology Branch, National Cancer Institute, Bethesda, MD
| | - Barbara H. Rath
- Radiation Oncology Branch, National Cancer Institute, Bethesda, MD
| | - Heekyong Bae
- Radiation Oncology Branch, National Cancer Institute, Bethesda, MD
| | - Tamalee Kramp
- Radiation Oncology Branch, National Cancer Institute, Bethesda, MD
| | | | - Kevin Camphausen
- Radiation Oncology Branch, National Cancer Institute, Bethesda, MD
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11
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Kahn J, Hayman TJ, Jamal M, Rath BH, Kramp T, Camphausen K, Tofilon PJ. The mTORC1/mTORC2 inhibitor AZD2014 enhances the radiosensitivity of glioblastoma stem-like cells. Neuro Oncol 2013; 16:29-37. [PMID: 24311635 DOI: 10.1093/neuonc/not139] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The mammalian target of rapamycin (mTOR) has been suggested as a target for radiosensitization. Given that radiotherapy is a primary treatment modality for glioblastoma (GBM) and that mTOR is often dysregulated in GBM, the goal of this study was to determine the effects of AZD2014, a dual mTORC1/2 inhibitor, on the radiosensitivity of GBM stem-like cells (GSCs). METHODS mTORC1 and mTORC2 activities were defined by immunoblot analysis. The effects of this mTOR inhibitor on the in vitro radiosensitivity of GSCs were determined using a clonogenic assay. DNA double strand breaks were evaluated according to γH2AX foci. Orthotopic xenografts initiated from GSCs were used to define the in vivo response to AZD2014 and radiation. RESULTS Exposure of GSCs to AZD2014 resulted in the inhibition of mTORC1 and 2 activities. Based on clonogenic survival analysis, addition of AZD2014 to culture media 1 hour before irradiation enhanced the radiosensitivity of CD133+ and CD15+ GSC cell lines. Whereas AZD2014 treatment had no effect on the initial level of γH2AX foci, the dispersal of radiation-induced γH2AX foci was significantly delayed. Finally, the combination of AZD2014 and radiation delivered to mice bearing GSC-initiated orthotopic xenografts significantly prolonged survival as compared with the individual treatments. CONCLUSIONS These data indicate that AZD2014 enhances the radiosensitivity of GSCs both in vitro and under orthotopic in vivo conditions and suggest that this effect involves an inhibition of DNA repair. Moreover, these results suggest that this dual mTORC1/2 inhibitor may be a radiosensitizer applicable to GBM therapy.
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Affiliation(s)
- Jenna Kahn
- Corresponding author: Philip J. Tofilon, PhD, National Cancer Institute, 10 Center Drive-MSC 1002, Building 10, B3B69B, Bethesda, MD 20892.
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