Ling Geng
Publications
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6.75Impact points
The novel chemical entity YTR107 inhibits recruitment of nucleophosmin to sites of DNA damage, suppressing repair of DNA double-strand breaks and enhancing radiosensitization.
Clinical cancer research : an official journal of the American Association for Cancer Research. 08/2011; 17(20):6490-9.
Radiation therapy continues to be an important therapeutic strategy for providing definitive local/regional control of human cancer. However, oncogenes that harbor driver mutations and/or amplifications can compromise therapeutic efficacy. Thus, there is a need for novel approaches that enhance the ... [more] Radiation therapy continues to be an important therapeutic strategy for providing definitive local/regional control of human cancer. However, oncogenes that harbor driver mutations and/or amplifications can compromise therapeutic efficacy. Thus, there is a need for novel approaches that enhance the DNA damage produced by ionizing radiation. A forward chemical genetic approach coupled with cell-based phenotypic screening of several tumor cell lines was used to identify a novel chemical entity (NCE) that functioned as a radiation sensitizer. Proteomics, comet assays, confocal microscopy, and immunoblotting were used to identify the biological target. The screening process identified a 5-((N-benzyl-1H-indol-3-yl)-methylene)pyrimidine-2,4,6(1H,3H,5H)trione as an NCE that radiosensitized cancer cells expressing amplified and/or mutated RAS, ErbB, PIK3CA, and/or BRAF oncogenes. Affinity-based solid-phase resin capture followed by liquid chromatography/tandem mass spectrometry identified the chaperone nucleophosmin (NPM) as the NCE target. SiRNA suppression of NPM abrogated radiosensitization by the NCE. Confocal microscopy showed that the NCE inhibited NPM shuttling to radiation-induced DNA damage repair foci, and the analysis of comet assays indicated a diminished rate of DNA double-strand break repair. These data support the hypothesis that inhibition of DNA repair due to inhibition of NPM shuttling increases the efficacy of DNA-damaging therapeutic strategies.
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4.59Impact points
A new class of molecular targeted radioprotectors: GSK-3beta inhibitors.
International journal of radiation oncology, biology, physics. 02/2010; 76(2):557-65.
Development of new treatments is critical to effective protection against radiation-induced injury. We investigate the potential of developing small-molecule inhibitors of glycogen synthase kinase 3beta (GSK-3beta)-SB216763 or SB415286-as radioprotective agents to attenuate intestinal injury. A surv... [more] Development of new treatments is critical to effective protection against radiation-induced injury. We investigate the potential of developing small-molecule inhibitors of glycogen synthase kinase 3beta (GSK-3beta)-SB216763 or SB415286-as radioprotective agents to attenuate intestinal injury. A survival study was done by use of C57BL/6J mice to evaluate the radioprotective effect of GSK-3beta inhibitors. Terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay and immunohistochemical staining for Bax and Bcl-2 were used to assess apoptosis in the small intestines of the treated mice. A clonogenic survival study, apoptosis assays (staining with annexin V or 4',6-diamidino-2-phenylindole), and immunoblot analysis of beta-catenin, Bcl-2, Bax, and caspase 3 were done by use of Rat intestinal epithelial cell line IEC-6 cells. Pretreatment with SB415286 significantly improved survival of mice irradiated with 8 and 12 Gy. Mice pretreated with SB216763 or SB415286 showed a significant reduction in TUNEL- and Bax-positive cells and an increase in Bcl-2-positive cells in intestinal crypts at 4 and/or 12 h after radiation with 4 and/or 8 Gy compared with radiation alone. Pretreatment of irradiated IEC-6 cells with GSK-3beta inhibitors significantly increased clonogenic survival compared with cells treated with radiation alone. This increase was due to the attenuation of radiation-induced apoptosis, as shown by annexin V and 4',6-diamidino-2-phenylindole assays, as well as immunoblot analysis of Bcl-2, Bax, and caspase 3. Glycogen synthase kinase 3beta small-molecule inhibitors protect mouse intestine from radiation-induced damage in cell culture and in vivo and improve survival of mice. Molecular mechanisms of this protection involve attenuated radiation-induced apoptosis regulated by Bcl-2, Bax, and caspase 3. Therefore GSK-3beta inhibitors reduce deleterious consequences of intestinal irradiation and thereby improve quality of life during radiation therapy.
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1.84Impact points
Radiation induces an antitumour immune response to mouse melanoma.
International journal of radiation biology. 12/2009; 85(12):1126-36.
Purpose: Irradiation of cancer cells can cause immunogenic death. We used mouse models to determine whether irradiation of melanoma can enhance the host antitumour immune response and function as an effective vaccination strategy, and investigated the molecular mechanisms involved in this radiation-... [more] Purpose: Irradiation of cancer cells can cause immunogenic death. We used mouse models to determine whether irradiation of melanoma can enhance the host antitumour immune response and function as an effective vaccination strategy, and investigated the molecular mechanisms involved in this radiation-induced response. Materials and methods: For in vivo studies, C57BL6/J mice and the B16F0 melanoma cell line were used in a lung metastasis model, intratumoural host immune activation assays, and tumour growth delay studies. In vitro studies included a dendritic cell (DC) phagocytosis assay, detection of cell surface exposure of the protein calreticulin (CRT), and small interfering RNA (siRNA)-mediated depletion of CRT cellular levels. Results: Irradiation of cutaneous melanomas prior to their resection resulted in more than 20-fold reduction in lung metastases after systemic challenge with untreated melanoma cells. A syngeneic vaccine derived from irradiated melanoma cells also induced adaptive immune response markers in irradiated melanoma implants. Our data indicate a trend for radiation-induced increase in melanoma cell surface exposure of CRT, which is involved in the enhanced phagocytic activity of DC against irradiated melanoma cells (VIACUC). Conclusion: The present study suggests that neoadjuvant irradiation of cutaneous melanoma tumours prior to surgical resection can stimulate an endogenous anti-melanoma host immune response.
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6.40Impact points
Indolyl-quinuclidinols inhibit ENOX activity and endothelial cell morphogenesis while enhancing radiation-mediated control of tumor vasculature.
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology. 04/2009;
There is a need for novel strategies that target tumor vasculature, specifically those that synergize with cytotoxic therapy, in order to overcome resistance that can develop with current therapeutics. A chemistry-driven drug discovery screen was employed to identify novel compounds that inhibit end... [more] There is a need for novel strategies that target tumor vasculature, specifically those that synergize with cytotoxic therapy, in order to overcome resistance that can develop with current therapeutics. A chemistry-driven drug discovery screen was employed to identify novel compounds that inhibit endothelial cell tubule formation. Cell-based phenotypic screening revealed that noncytotoxic concentrations of (Z)-(+/-)-2-(1-benzenesulfonylindol-3-ylmethylene)-1-azabicyclo[2.2.2]octan-3-ol (analog I) and (Z)-(+/-)-2-(1-benzylindol-3-ylmethylene)-1-azabicyclo[2.2.2]octan-3-ol (analog II) inhibited endothelial cell migration and the ability to form capillary-like structures in Matrigel by >/=70%. The ability to undergo neoangiogenesis, as measured in a window-chamber model, was also inhibited by 70%. Screening of biochemical pathways revealed that analog II inhibited the enzyme ENOX1 (EC50 = 10 microM). Retroviral-mediated shRNA suppression of endothelial ENOX1 expression inhibited cell migration and tubule formation, recapitulating the effects observed with the small-molecule analogs. Genetic or chemical suppression of ENOX1 significantly increased radiation-mediated Caspase3-activated apoptosis, coincident with suppression of p70S6K1 phosphorylation. Administration of analog II prior to fractionated X-irradiation significantly diminished the number and density of tumor microvessels, as well as delayed syngeneic and xenograft tumor growth compared to results obtained with radiation alone. Analysis of necropsies suggests that the analog was well tolerated. These results suggest that targeting ENOX1 activity represents a novel therapeutic strategy for enhancing the radiation response of tumors.-Geng, L., Rachakonda, G., Morré, D. J., Morré, D. M., Crooks, P. A., Sonar, V. N., Roti Roti, J. L., Rogers, B. E., Greco, S., Ye, F., Salleng, K. J., Sasi, S., Freeman, M. L., Sekhar, K. R. Indolyl-quinuclidinols inhibit ENOX activity and endothelial cell morphogenesis while enhancing radiation-mediated control of tumor vasculature.
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6.75Impact points
Cytosolic Phospholipase A2: Targeting Cancer through the Tumor Vasculature.
Clinical cancer research : an official journal of the American Association for Cancer Research. 03/2009;
PURPOSE: In vascular endothelial cells, low doses of ionizing radiation trigger the immediate activation of cytosolic phospholipase A2 (cPLA2). This event initiates prosurvival signaling that could be responsible for radioresistance of tumor vasculature. Thus, the development of radiosensitizers tar... [more] PURPOSE: In vascular endothelial cells, low doses of ionizing radiation trigger the immediate activation of cytosolic phospholipase A2 (cPLA2). This event initiates prosurvival signaling that could be responsible for radioresistance of tumor vasculature. Thus, the development of radiosensitizers targeting these survival pathways may enhance tumor response to radiation therapy. Arachidonyltrifluoromethyl Ketone (AACOCF3), a specific cPLA2 inhibitor, was studied as a potential radiosensitizer. EXPERIMENTAL DESIGN: Vascular endothelial cells (3B11 and MPMEC) and lung tumor cells (LLC and H460) were treated with 1 micromol/L AACOCF3 for 30 minutes prior to irradiation. Treatment response was evaluated by clonogenic survival, activation of extracellular signal-regulated kinase 1/2 (ERK1/2), tubule formation, and migration assays. For in vivo experiments, mice with LLC or H460 tumors in the hind limbs were treated for 5 consecutive days with 10 mg/kg AACOCF3 administered daily 30 minutes prior to irradiation. Treatment response was assessed by tumor growth delay, Power Doppler Sonography, and immunohistochemistry. RESULTS: In cell culture experiments, inhibition of cPLA2 with AACOCF3 prevented radiation-induced activation of ERK1/2 and decreased clonogenic survival of irradiated vascular endothelial cells but not the lung tumor cells. Treatment with AACOCF3 also attenuated tubule formation and migration in irradiated vascular endothelial cells. In both tumor mouse models, treatment with AACOCF3 prior to irradiation significantly suppressed tumor growth and decreased overall tumor blood flow and vascularity. Increased apoptosis in both tumor cells and tumor vascular endothelium was determined as a possible mechanism of the observed effect. CONCLUSION: These findings identify cPLA2 as a novel molecular target for tumor sensitization to radiation therapy through the tumor vasculature.
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4.59Impact points
SU11248 (sunitinib) sensitizes pancreatic cancer to the cytotoxic effects of ionizing radiation.
International journal of radiation oncology, biology, physics. 07/2008; 71(3):873-9.
PURPOSE: SU11248 (sunitinib) is a small-molecule tyrosine kinase inhibitor which targets VEGFR and PDGFR isoforms. In the present study, the effects of SU11248 and ionizing radiation on pancreatic cancer were studied. METHODS AND MATERIALS: For in vitro studies human pancreatic adenocarcinoma cells ... [more] PURPOSE: SU11248 (sunitinib) is a small-molecule tyrosine kinase inhibitor which targets VEGFR and PDGFR isoforms. In the present study, the effects of SU11248 and ionizing radiation on pancreatic cancer were studied. METHODS AND MATERIALS: For in vitro studies human pancreatic adenocarcinoma cells lines were treated with 1 microM SU11248 1 h before irradiation. Western blot analysis was used to determine the effect of SU11248 on radiation-induced signal transduction. To determine if SU11248 sensitized pancreatic cancer to the cytotoxic effects of ionizing radiation, a clonogenic survival assay was performed using 0-6 Gy. For in vivo assays, CAPAN-1 cells were injected into the hind limb of nude mice for tumor volume and proliferation studies. RESULTS: SU11248 attenuated radiation-induced phosphorylation of Akt and ERK at 0, 5, 15, and 30 min. Furthermore, SU11248 significantly reduced clonogenic survival after treatment with radiation (p < 0.05). In vivo studies revealed that SU11248 and radiation delayed tumor growth by 6 and 10 days, respectively, whereas combined treatment delayed tumor growth by 30 days. Combined treatment with SU11248 and radiation further attenuated Brdu incorporation by 75% (p = 0.001) compared to control. CONCLUSIONS: SU11248 (sunitinib) sensitized pancreatic cancer to the cytotoxic effects of radiation. This compound is promising for future clinical trials with chemoradiation in pancreatic cancer.
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7.54Impact points
Bone marrow X kinase-mediated signal transduction in irradiated vascular endothelium.
Cancer research. 05/2008; 68(8):2861-9.
Radiation-induced activation of the phosphatidyl inositol-3 kinase/Akt signal transduction pathway requires Akt binding to phosphatidyl-inositol phosphates (PIP) on the cell membrane. The tyrosine kinase bone marrow X kinase (Bmx) binds to membrane-associated PIPs in a manner similar to Akt. Because... [more] Radiation-induced activation of the phosphatidyl inositol-3 kinase/Akt signal transduction pathway requires Akt binding to phosphatidyl-inositol phosphates (PIP) on the cell membrane. The tyrosine kinase bone marrow X kinase (Bmx) binds to membrane-associated PIPs in a manner similar to Akt. Because Bmx is involved in cell growth and survival pathways, it could contribute to the radiation response within the vascular endothelium. We therefore studied Bmx signaling within the vascular endothelium. Bmx was activated rapidly in response to clinically relevant doses of ionizing radiation. Bmx inhibition enhanced the efficacy of radiotherapy in endothelial cells as well as tumor vascular endothelium in lung cancer tumors in mice. Retroviral shRNA knockdown of Bmx protein enhanced human umbilical vascular endothelial cell (HUVEC) radiosensitization. Furthermore, pretreatment of HUVEC with a pharmacologic inhibitor of Bmx, LFM-A13, produced significant radiosensitization of endothelial cells as measured by clonogenic survival analysis and apoptosis as well as functional assays including cell migration and tubule formation. In vivo, LFM-A13, when combined with radiation, resulted in significant tumor microvascular destruction as well as enhanced tumor growth delay. Bmx therefore represents a molecular target for the development of novel radiosensitizing agents.
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27.14Impact points
Noninvasive assessment of cancer response to therapy.
Nature medicine. 04/2008; 14(3):343-9.
Rapid assessment of cancer response to a therapeutic regimen can determine efficacy early in the course of treatment. Although biopsies of cancer can be used to rapidly assess pharmacodynamic response, certain disease sites are less accessible to repeated biopsies. Here, we simultaneously assess res... [more] Rapid assessment of cancer response to a therapeutic regimen can determine efficacy early in the course of treatment. Although biopsies of cancer can be used to rapidly assess pharmacodynamic response, certain disease sites are less accessible to repeated biopsies. Here, we simultaneously assess response in all sites of disease within days of starting therapy by use of peptide ligands selected for their ability to discern responding from nonresponding cancers. When conjugated to near-infrared imaging agents, the HVGGSSV peptide differentiates between these two types of cancer. Rapid, noninvasive assessment of the pharmacodynamic response within cancer promises to accelerate drug development and minimize the duration of treatment with ineffective regimens in cancer patients.
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2.23Impact points
Histone deacetylase inhibitor NVP-LAQ824 sensitizes human nonsmall cell lung cancer to the cytotoxic effects of ionizing radiation.
Anti-cancer drugs. 09/2007; 18(7):793-800.
Stage III nonsmall cell lung cancer is primarily treated with combined chemotherapy and radiation therapy. Relapses for progression of disease within irradiated sites remains a primary pattern of failure. To evaluate the interaction between histone deacetylase inhibitors and irradiation in nonsmall ... [more] Stage III nonsmall cell lung cancer is primarily treated with combined chemotherapy and radiation therapy. Relapses for progression of disease within irradiated sites remains a primary pattern of failure. To evaluate the interaction between histone deacetylase inhibitors and irradiation in nonsmall cell lung cancer, we studied NVP-LAQ824 in mouse models of human lung cancer. Colony formation assays were performed to determine whether LAQ824 sensitized nonsmall cell lung cancer to the cytotoxic effects of ionizing radiation. LAQ824 reduced clonogenic survival of the H23 and H460 cell lines five-fold compared with controls and four-fold compared with either agent alone (P<0.001). Western blot analysis of caspase cleavage, microscopic analysis of nuclei and Annexin-fluorescein isothiocyanate/propidium iodide flow cytometry assays showed that LAQ824 enhanced radiation-induced apoptosis and attenuated mitosis (P<0.001). Immunostaining for gamma-H2AX nuclear foci was performed to determine the effect of LAQ824 on radiation-induced DNA double-strand breaks. Combined modality treatment delayed the resolution of gamma-H2AX foci with over 30% of cells staining positive 6 h after treatment versus approximately 5 and 3% in cells treated with LAQ824 or radiation alone (P<0.001). Additionally, an in-vivo xenograft model was utilized to study the effects of fractioned irradiation and LAQ824 on tumor growth. Fractioned irradiation and LAQ824 delayed tumor growth by 19 days versus 7 and 4 days for treatment with LAQ824 and radiation alone. This study shows the effectiveness of histone deacetylase inhibitors to enhance the cytotoxic effects of radiation by attenuating DNA repair and inducing apoptosis in human nonsmall cell lung cancer.
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7.54Impact points
HIV protease inhibitors enhance the efficacy of irradiation.
Cancer research. 06/2007; 67(10):4886-93.
Tumor vascular endothelium is rather resistant to the cytotoxic effects of radiation. The HIV protease inhibitors (HPI) amprenavir, nelfinavir, and saquinavir have previously been shown to sensitize tumor cells to the cytotoxic effects of radiation. Additionally, this class of drug has been shown to... [more] Tumor vascular endothelium is rather resistant to the cytotoxic effects of radiation. The HIV protease inhibitors (HPI) amprenavir, nelfinavir, and saquinavir have previously been shown to sensitize tumor cells to the cytotoxic effects of radiation. Additionally, this class of drug has been shown to inhibit angiogenesis and tumor cell migration. Therefore, in the current study, we wanted to determine whether HPIs could enhance the effect of radiation on endothelial function. Our study shows that HPIs, particularly nelfinavir, significantly enhance radiations effect on human umbilical vein endothelial cells (HUVEC) and tumor vascular endothelium. We show that pretreatment of HUVEC with nelfinavir results in enhanced cytotoxicity, including increased apoptosis, when combined with radiation. Moreover, using several functional assays, we show that combination treatment effectively blocks endothelial cell migration and organization. These findings were accompanied by attenuation of Akt phosphorylation, a known pathway for radioresistance. Last, in vivo analysis of tumor microvasculature destruction showed a more than additive effect for nelfinavir and radiation. This study shows that HPIs can enhance the effect of ionizing radiation on vascular endothelium. Therefore, the Food and Drug Administration-approved drug, nelfinavir, may be an effective radiosensitizer in the clinic.
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6.75Impact points
Inhibition of poly(ADP-ribose) polymerase enhances cell death and improves tumor growth delay in irradiated lung cancer models.
Clinical cancer research : an official journal of the American Association for Cancer Research. 06/2007; 13(10):3033-42.
PURPOSE: Poly(ADP-ribose) polymerase-1 (PARP-1) is the founding member of a family of enzymes that catalyze the addition of ADP-ribose units to proteins that mediate DNA repair pathways. Ionizing radiation induces DNA strand breaks, suggesting that PARP-1 inhibition may sensitize tumor cells to radi... [more] PURPOSE: Poly(ADP-ribose) polymerase-1 (PARP-1) is the founding member of a family of enzymes that catalyze the addition of ADP-ribose units to proteins that mediate DNA repair pathways. Ionizing radiation induces DNA strand breaks, suggesting that PARP-1 inhibition may sensitize tumor cells to radiation. EXPERIMENTAL DESIGN: We investigated the combination of PARP-1 inhibition with radiation in lung cancer models. ABT-888, a novel potent PARP-1 inhibitor, was used to explore the effects of PARP-1 inhibition on irradiated tumors and tumor vasculature. RESULTS: ABT-888 reduced clonogenic survival in H460 lung cancer cells, and inhibited DNA repair as shown by enhanced expression of DNA strand break marker histone gamma-H2AX. Both apoptosis and autophagy contributed to the mechanism of increased cell death. Additionally, ABT-888 increased tumor growth delay at well-tolerated doses in murine models. For a 5-fold increase in tumor volume, tumor growth delay was 1 day for ABT-888 alone, 7 days for radiation alone, and 13.5 days for combination treatment. Immunohistochemical staining of tumor sections revealed an increase in terminal deoxyribonucleotide transferase-mediated nick-end labeling apoptotic staining, and a decrease in Ki-67 proliferative staining after combination treatment. Matrigel assay showed a decrease in in vitro endothelial tubule formation with ABT-888/radiation combination treatment, and von Willebrand factor staining of tumor sections revealed decreased vessel formation in vivo, suggesting that this strategy may also target tumor angiogenesis. CONCLUSIONS: We conclude that PARP-1 inhibition shows promise as an effective means of enhancing tumor sensitivity to radiation, and future clinical studies are needed to determine the potential of ABT-888 as a radiation enhancer.
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2.23Impact points
Effects of vascular endothelial growth factor receptor inhibitor SU5416 and prostacyclin on murine lung metastasis.
Anti-cancer drugs. 03/2007; 18(3):349-55.
The majority of patients with a diagnosis of cancer die from metastatic disease. Targeting specific steps in the metastatic process has the potential to improve patient outcomes. In this study, a novel lung metastasis model was developed by injecting DiI (1,1'-dioctadecyl-3,3,3',3'-tetra... [more] The majority of patients with a diagnosis of cancer die from metastatic disease. Targeting specific steps in the metastatic process has the potential to improve patient outcomes. In this study, a novel lung metastasis model was developed by injecting DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbo-cyanine perchlorate)-labeled Lewis lung carcinoma cells into the tail vein of mice. The temporal development of tumor metastases was studied in the lung, liver and spleen. Additionally, the effects of vascular endothelial growth factor receptor inhibitor SU5416 and platelet activation inhibitor prostacyclin were tested in this metastasis model. Systemically injected Lewis lung carcinoma cells present in the lung at 15 min slowly accumulated in the liver and spleen reaching a peak at 4 days. After 8 days, tumor development was only evident in the lung. Use of SU5416 or prostacyclin lowered the initial density of Lewis lung carcinoma-labeled cells in the lung by a factor 1.8 and 2.3, respectively (P<0.05). Furthermore, treatment with prostacyclin or SU5416 decreased lung weight by over 50% and the number of visible metastatic nodes by over 90% (P<0.05). Combined treatment resulted in grossly normal lung tissue. Additionally, systemic treatment with prostacyclin reduced harvested metastatic cell adherence to endothelial cells by a factor of 10 and treatment with SU5416 attenuated vascular formation (P<0.001). In conclusion, SU5416 and prostacyclin effectively attenuated metastasis formation in this model. DiI labeling is an effective technique to monitor the temporal and spatial distribution of metastatic cells.
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Hedgehog signaling in the murine melanoma microenvironment.
Angiogenesis. 02/2007; 10(4):259-67.
The Hedgehog intercellular signaling pathway regulates cell proliferation and differentiation. This pathway has been implicated to play a role in the pathogenesis of cancer and in embryonic blood vessel development. In the current study, Hedgehog signaling in tumor related vasculature and microenvir... [more] The Hedgehog intercellular signaling pathway regulates cell proliferation and differentiation. This pathway has been implicated to play a role in the pathogenesis of cancer and in embryonic blood vessel development. In the current study, Hedgehog signaling in tumor related vasculature and microenvironment was examined using human umbilical vein endothelial cells and B16F0 (murine melanoma) tumors models. Use of exogenous Sonic hedgehog (Shh) peptide significantly increased BrdU incorporation in endothelial cells in vitro by a factor of 2 (P < 0.001). The Hedgehog pathway antagonist cyclopamine effectively reduced Shh-induced proliferation to control levels. To study Hedgehog signaling in vivo a hind limb tumor model with the B16F0 cell line was used. Treatment with 25 mg/kg cyclopamine significantly attenuated BrdU incorporation in tumor cells threefold (P < 0.001), in tumor related endothelial cells threefold (P = 0.004), and delayed tumor growth by 4 days. Immunohistochemistry revealed that the Hedgehog receptor Patched was localized to the tumor stroma and that B16F0 cells expressed Shh peptide. Furthermore, mouse embryonic fibroblasts required the presence of B16F0 cells to express Patched in a co-culture assay system. These studies indicate that Shh peptide produced by melanoma cells induces Patched expression in fibroblasts. To study tumor related angiogenesis a vascular window model was used to monitor tumor vascularity. Treatment with cyclopamine significantly attenuated vascular formation by a factor of 2.5 (P < 0.001) and altered vascular morphology. Furthermore, cyclopamine reduced tumor blood vessel permeability to FITC labeled dextran while having no effect on normal blood vessels. These studies suggest that Hedgehog signaling regulates melanoma related vascular formation and function.
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7.54Impact points
Histone deacetylase (HDAC) inhibitor LBH589 increases duration of gamma-H2AX foci and confines HDAC4 to the cytoplasm in irradiated non-small cell lung cancer.
Cancer research. 01/2007; 66(23):11298-304.
Histone deacetylases (HDAC) have been identified as therapeutic targets due to their regulatory function in DNA structure and organization. LBH589 is a novel inhibitor of class I and II HDACs. We studied the effect of LBH589 and ionizing radiation (IR) on DNA repair in two human non-small cell lung ... [more] Histone deacetylases (HDAC) have been identified as therapeutic targets due to their regulatory function in DNA structure and organization. LBH589 is a novel inhibitor of class I and II HDACs. We studied the effect of LBH589 and ionizing radiation (IR) on DNA repair in two human non-small cell lung cancer (NSCLC) cell lines (H23 and H460). gamma-H2AX foci present at DNA double-strand breaks (DSBs) were detected in the nuclei following 3 Gy irradiation for up to 6 hours. LBH589 administered before irradiation increased the duration of gamma-H2AX foci beyond 24 hours. Furthermore, radiation alone induced translocation of HDAC4 to the nucleus. In contrast, treatment with LBH589 followed by irradiation resulted in HDAC4 confinement to the cytoplasm, indicating that HDAC inhibition affects the nuclear localization of HDAC4. The findings that LBH589 confines HDAC4 to the cytoplasm and increases the duration of gamma-H2AX foci in irradiated cell lines suggest that HDAC4 participates in DNA damage signaling following IR. Annexin-propidium iodide flow cytometry assays, cell morphology studies, and cleaved caspase-3 Western blot analysis revealed a synergistic effect of LBH589 with IR in inducing apoptosis. Clonogenic survival showed a greater than additive effect when LBH589 was administered before irradiation compared with irradiation alone. In vivo tumor volume studies showed a growth delay of 20 days with combined treatment compared with 4 and 2 days for radiation or LBH589 alone. This study identifies HDAC4 as a biomarker of LBH589 activity and recognizes the ability of LBH589 to sensitize human NSCLC to radiation-induced DNA DSBs.
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7.54Impact points
Vascular endothelial growth factor tyrosine kinase inhibitor AZD2171 and fractionated radiotherapy in mouse models of lung cancer.
Cancer research. 01/2007; 66(23):11409-15.
The vascular endothelial growth factor receptor (VEGFR) tyrosine kinases are being explored as targets for antiangiogenic cancer therapy. Radiotherapy also inhibits tumor growth and affects vasculature. We investigated the combination of the potent VEGFR tyrosine kinase inhibitor AZD2171 and ionizin... [more] The vascular endothelial growth factor receptor (VEGFR) tyrosine kinases are being explored as targets for antiangiogenic cancer therapy. Radiotherapy also inhibits tumor growth and affects vasculature. We investigated the combination of the potent VEGFR tyrosine kinase inhibitor AZD2171 and ionizing radiation in cell culture and mouse models of lung cancer. We show that ionizing radiation induces expression of phosphorylated VEGFR-2 (Flk-1) in endothelial cells and that this phosphorylation is inhibited by AZD2171. Human umbilical vascular endothelial cells become more sensitive to radiation after treatment with AZD2171 as determined by clonogenic assay. Matrigel assay showed a decrease in in vitro endothelial tubule formation with AZD2171/radiation combination treatment. When similar combination was applied to the H460 lung cancer xenograft model in nude mice, loss of radiation-induced phosphorylated Flk-1 was observed in the combination treatment group, which also showed a large decrease in tumor vascular density by staining of the von Willebrand factor. H460 tumor growth delay was enhanced in the combination treatment group compared with the groups treated with AZD2171 or radiation alone. Additionally, after therapy, Ki67 index showed >4-fold reduction of tumor proliferation in the combination therapy group, which also showed increased intratumoral apoptotic index by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. In conclusion, AZD2171 sensitizes lung tumor xenografts to radiation and inhibits angiogenesis both in vitro and in vivo. When used as a radiation enhancer, AZD2171 has the potential to improve tumor growth delay by inhibiting tumor proliferation and promoting apoptosis. Clinical trials are needed to determine the potential of this combination therapy in patients with locally advanced lung cancer.
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1.18Impact points
Noninvasive assessment of tumor vasculature response to radiation-mediated, vasculature-targeted therapy using quantified power Doppler sonography: implications for improvement of therapy schedules.
Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 01/2007; 25(12):1507-17.
OBJECTIVE: Stereotactic radiotherapy (ablative radiation) is a modality that holds considerable promise for effective treatment of intracranial and extracranial malignancies. Although tumor vasculature is relatively resistant to small fractionated doses of ionizing radiation, large ablative doses of... [more] OBJECTIVE: Stereotactic radiotherapy (ablative radiation) is a modality that holds considerable promise for effective treatment of intracranial and extracranial malignancies. Although tumor vasculature is relatively resistant to small fractionated doses of ionizing radiation, large ablative doses of ionizing radiation lead to effective demise of the tumor vasculature. The purpose of this study was (1) to noninvasively monitor and compare tumor physiologic parameters in response to ablative radiation treatments and (2) to use these noninvasive parameters to optimize the schedule of administration of radiation therapy. METHODS: Lewis lung carcinoma tumors were implanted into C57BL/6 mice and treated with ablative radiation. The kinetics of change in physiologic parameters of a response to single-dose 20-Gy treatments was measured. Parameters studied included tumor blood flow, apoptosis, and proliferation rates. Serial tumor sections were stained to correlate noninvasive Doppler assessment of tumor blood flow with microvasculature histologic findings. RESULTS: A single administration of 20 Gy led to an incomplete tumor vascular response, with subsequent recovery of tumor blood flow within 4 days after treatment. Sustained reduction of tumor blood flow by administering the successive ablative radiation treatment before tumor blood flow recovery led to a 3-fold tumor growth delay. The difference in tumor volumes at each measurement time point (every 2 days) was statistically significant (P=.016). CONCLUSIONS: This study suggests a rational design of schedule optimization for radiation-mediated, vasculature-directed treatments guided by noninvasive assessment of tumor blood flow levels to ultimately improve the tumor response.
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7.54Impact points
Inhibition of mammalian target of rapamycin or apoptotic pathway induces autophagy and radiosensitizes PTEN null prostate cancer cells.
Cancer research. 11/2006; 66(20):10040-7.
The phosphatidylinositol 3-kinase/Akt pathway plays a critical role in oncogenesis, and dysregulation of this pathway through loss of PTEN suppression is a particularly common phenomenon in aggressive prostate cancers. The mammalian target of rapamycin (mTOR) is a downstream signaling kinase in this... [more] The phosphatidylinositol 3-kinase/Akt pathway plays a critical role in oncogenesis, and dysregulation of this pathway through loss of PTEN suppression is a particularly common phenomenon in aggressive prostate cancers. The mammalian target of rapamycin (mTOR) is a downstream signaling kinase in this pathway, exerting prosurvival influence on cells through the activation of factors involved in protein synthesis. The mTOR inhibitor rapamycin and its derivatives are cytotoxic to a number of cell lines. Recently, mTOR inhibition has also been shown to radiosensitize endothelial and breast cancer cells in vitro. Because radiation is an important modality in the treatment of prostate cancer, we tested the ability of the mTOR inhibitor RAD001 (everolimus) to enhance the cytotoxic effects of radiation on two prostate cancer cell lines, PC-3 and DU145. We found that both cell lines became more vulnerable to irradiation after treatment with RAD001, with the PTEN-deficient PC-3 cell line showing the greater sensitivity. This increased susceptibility to radiation is associated with induction of autophagy. Furthermore, we show that blocking apoptosis with caspase inhibition and Bax/Bak small interfering RNA in these cell lines enhances radiation-induced mortality and induces autophagy. Together, these data highlight the emerging importance of mTOR as a molecular target for therapeutic intervention, and lend support to the idea that nonapoptotic modes of cell death may play a crucial role in improving tumor cell kill.
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4.59Impact points
Integrin alpha v beta 3 antagonist Cilengitide enhances efficacy of radiotherapy in endothelial cell and non-small-cell lung cancer models.
International journal of radiation oncology, biology, physics. 09/2006; 65(5):1536-43.
PURPOSE: Integrins alpha v beta 3 and alpha v beta 5 are important in tumor growth and angiogenesis and have been recently explored as targets for cancer therapy. Radiotherapy also inhibits tumor growth and affects vasculature. We explored the combination of integrin antagonist Cilengitide (EMD 1219... [more] PURPOSE: Integrins alpha v beta 3 and alpha v beta 5 are important in tumor growth and angiogenesis and have been recently explored as targets for cancer therapy. Radiotherapy also inhibits tumor growth and affects vasculature. We explored the combination of integrin antagonist Cilengitide (EMD 121974) and ionizing radiation. METHODS AND MATERIALS: Levels of alpha v beta 3 were determined for human umbilical vein endothelial cells (HUVEC), as well as H157 and H460 human non-small-cell lung cancer cells, using FACS analysis and immunofluorescence imaging. Clonogenic assays, Western immunoblots probed for cleaved caspase 3, and Annexin-V probing were used to evaluate cell survival and apoptosis. A cell detachment assay and matrigel assay were used to further examine the effects of treatment. RESULTS: Human umbilical vein endothelial cells had the highest alpha v beta 3 level, followed by H157, and H460. Interestingly, we found that 5 Gy irradiation induced expression of alpha v beta 3 in all cell lines. Clonogenic assays showed a radiosensitizing effect with Cilengitide, and calculation of the dose enhancement ratio showed that the effect was highest in HUVECs (1.38), followed by H157 (1.19), and H460 (1.10), corresponding to the levels of target expression. There was an increase in apoptotic cells after combination treatment with Cilengitide and radiation, and there was an increase in detached cells after treatment with Cilengitide. Additionally, there was decreased endothelial tubule formation after combination treatment. CONCLUSIONS: We conclude that radiation induces expression of alpha v beta 3 integrin in endothelial and non-small-cell lung cancer models, and that integrin antagonist Cilengitide is a radiosensitizer in proportion to the levels of target integrin expression.
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4.59Impact points
SRC family kinase inhibitor SU6656 enhances antiangiogenic effect of irradiation.
International journal of radiation oncology, biology, physics. 04/2006; 64(4):1197-203.
PURPOSE: Src family kinases (SFK) have been identified as molecular targets. SU6656 is a small-molecle indolinone that specifically inhibits this family of kinases. METHODS AND MATERIALS: Human umbilical vein endothelial cells were used to study the effects of SFK inhibition. Western blot analysis w... [more] PURPOSE: Src family kinases (SFK) have been identified as molecular targets. SU6656 is a small-molecle indolinone that specifically inhibits this family of kinases. METHODS AND MATERIALS: Human umbilical vein endothelial cells were used to study the effects of SFK inhibition. Western blot analysis was performed to determine the effect of SFK inhibition on the PI3K/Akt pathway and caspase cleavage. Apoptosis was studied by propidium iodide staining of nuclei. Angiogenesis was examined using capillary tubule formation in Matrigel. Tumor response was further studied in vivo using Lewis lung carcinoma cells implanted into the dorsal skin fold of mice in the window model and in the hind limb in the tumor volume model. RESULTS: Clonogenic survival of endothelial cells was decreased after the combined therapy of SU6656 and radiation compared with radiotherapy alone. Furthermore, SFK inhibition by SU6656 attenuated radiation-induced Akt phosphorylation and increased radiation-induced apoptosis and vascular endothelium destruction. In vivo, SU6656 administered before irradiation significantly enhanced radiation-induced destruction of blood vessels within the tumor windows and enhanced tumor growth delay when administered during fractionated irradiation. CONCLUSIONS: This study demonstrates the potential use of SFK inhibition to enhance the effects of ionizing radiation during radiotherapy.
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7.54Impact points
Protein kinase B/Akt-dependent phosphorylation of glycogen synthase kinase-3beta in irradiated vascular endothelium.
Cancer research. 03/2006; 66(4):2320-7.
The vascular endothelium plays a critical role in the response of cancer to ionizing radiation. Activation of the phosphoinositide-3-kinase/Akt pathway is one initial signaling event in irradiated endothelial cells. Specifically, a low dose of ionizing radiation (3 Gy) induces phosphorylation of Akt... [more] The vascular endothelium plays a critical role in the response of cancer to ionizing radiation. Activation of the phosphoinositide-3-kinase/Akt pathway is one initial signaling event in irradiated endothelial cells. Specifically, a low dose of ionizing radiation (3 Gy) induces phosphorylation of Akt at Ser473 in the vascular endothelium within minutes of irradiation. However, signaling events that are downstream of Akt have not been well defined. Here, we show that phosphorylation of the Akt downstream target glycogen synthase kinase-3beta (GSK-3beta) at Ser9 also occurred within minutes of exposure to ionizing radiation. In addition, ionizing radiation caused the dissociation of GSK-3beta from the cell membrane, consistent with the inactivation of GSK-3beta enzyme activity. Overexpression of the dominant negative mutant Akt attenuated GSK-3beta phosphorylation at Ser9 and enhanced radiation-induced apoptosis. X-irradiated endothelial cells formed capillaries in both in vitro and in vivo models, whereas overexpression of the dominant negative mutant Akt inhibited capillary tubule formation. Studies using GSK-3beta antagonists showed that GSK-3beta activity was required for apoptosis in endothelial cells treated simultaneously with Akt antagonists and radiation. In mouse vascular models, radiation-induced microvascular destruction in response to Akt antagonists also required GSK-3beta function. These data indicate that on exposure of vascular endothelium to ionizing radiation, activation of Akt signaling contributes to GSK-3beta inhibition, which in turn promotes endothelial cell survival and capillary formation. Thus, pharmacologic regulation of Akt/GSK-3beta signaling may present a new approach to the radiation response in the tumor microvasculature.
Following (4)
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Todd D Giorgio
Vanderbilt University -
Hailun Wang
Vanderbilt University -
Girish Rachakonda
Vanderbilt University Medical Center -
Eugenia M Yazlovitskaya
Vanderbilt University -
Hayes Mcdonald
Vanderbilt University Medical Center
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