Publications by authors named "Benjamin P C Chen"

73 Publications

Personalized Ultrafractionated Stereotactic Adaptive Radiotherapy (PULSAR) in Preclinical Models Enhances Single-Agent Immune Checkpoint Blockade.

Int J Radiat Oncol Biol Phys 2021 Mar 29. Epub 2021 Mar 29.

Radiation Oncology; Harold C. Simmons Comprehensive Cancer; Department of Neurosurgery, UT Southwestern Medical Center, Dallas, Texas. Electronic address:

Purpose: Harnessing the immune-stimulatory effects of radiation by combining it with immunotherapy is a promising new treatment strategy. However, more studies characterizing immunotherapy and radiation dose scheduling for the optimal therapeutic effect is essential for designing clinical trials.

Methods And Materials: A new ablative radiation dosing scheme, personalized ultrafractionated stereotactic adaptive radiation therapy (PULSAR), was tested in combination with α-PD-L1 therapy in immune-activated and resistant syngeneic immunocompetent mouse models of cancer. Specifically, tumor growth curves comparing immunotherapy and radiation therapy dose sequencing were evaluated in immunologically cold and hot tumor models. The response relative to cytotoxic killer T cells was evaluated using an α-CD8 depleting antibody, and immunologic memory was tested by tumor rechallenge of cured mice.

Results: We report that both radiation and immunotherapy sequencing, as well as radiation therapy fraction spacing, affect the combination treatment response. Better tumor control was achieved by giving α-PD-L1 therapy during or after radiation, and spacing fractions 10 days apart (PULSAR) achieved better tumor control than traditional daily fractions. We showed that CD8 depleting antibody abrogated tumor control in the PULSAR combination treatment, and certain treatment schedules induced immunologic memory.

Conclusions: These results illustrate that radiation therapy dosing and scheduling affect tumor control, in combination with checkpoint blockade therapies. PULSAR-style radiation dosing is more complementary in combination with single-agent immunotherapy than traditional daily fractions in this preclinical model. Preclinical investigation could prove helpful in designing clinical trials investigating combination therapy.
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http://dx.doi.org/10.1016/j.ijrobp.2021.03.047DOI Listing
March 2021

DNA-PKcs inhibition impairs HDAC6-mediated HSP90 chaperone function on Aurora A and enhances HDACs inhibitor-induced cell killing by increasing mitotic aberrant spindle assembly.

Cell Cycle 2021 Jan 6;20(2):211-224. Epub 2021 Jan 6.

Department of Radiation Oncology, Simmons Comprehensive Cancer Center at UT Southwestern Medical Center , Dallas, TX, USA.

Combining targeted therapeutic agents is an attractive cancer treatment strategy associated with high efficacy and low toxicity. DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is an essential factor in DNA damage repair. Studies from us and others have revealed that DNA-PKcs also plays an important role in normal mitosis progression. Histone deacetylase (HDACs) inhibitors commonly lead to mitotic aberration and have been approved for treating various cancers in the clinic. We showed that DNA-PKcs depletion or kinase activity inhibition increases cancer cells' sensitivity to HDACs inhibitors and . DNA-PKcs deficiency significantly enhances HDACs inhibitors (HDACi)-induced mitotic arrest and is followed by apoptotic cell death. Mechanistically, we found that DNA-PKcs binds to HDAC6 and facilitates its acetylase activity. HDACi is more likely to impair HDAC6-induced deacetylation of HSP90 and abrogate HSP90's chaperone function on Aurora A, a critical mitotic kinase that regulates centrosome separation and mitotic spindle assembly in DNA-PKcs-deficient cells. Our current work indicates crosstalk between DNA-PKcs and HDACs signaling pathways, and highlights that the combined targeting of DNA-PKcs and HDACs can be used in cancer therapy. DNA-PKcs, DNA-dependent protein kinase catalytic subunit, HDACs, Histone deacetylases, DSBs, DNA double-strand breaks, ATM, ataxia telangiectasia mutated, ATR, ATM-Rad3-related.
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http://dx.doi.org/10.1080/15384101.2020.1867790DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7889180PMC
January 2021

Lysophosphatidic acid receptors 2 and 3 regulate erythropoiesis at different hematopoietic stages.

Biochim Biophys Acta Mol Cell Biol Lipids 2021 01 6;1866(1):158818. Epub 2020 Oct 6.

Department of Life Science, National Taiwan University, Taipei, Taiwan; Center for Biotechnology, National Taiwan University, Taipei, Taiwan; Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; Angiogenesis Research Center, National Taiwan University, Taipei, Taiwan; Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan. Electronic address:

Hematopoiesis, the complex developmental process that forms blood components and replenishes the blood system, involves multiple intracellular and extracellular mechanisms. We previously demonstrated that lysophosphatidic acid (LPA), a lipid growth factor, has opposing regulatory effects on erythrocyte differentiation through activation of LPA receptors 2 and 3; yet the mechanisms underlying this process remain unclear. In this study, LPA is observed that highly expressed in common myeloid progenitors (CMP) in murine myeloid cells, whereas the expression of LPA displaces in megakaryocyte-erythroid progenitors (MEP) of later stage of myeloid differentiation. Therefore, we hypothesized that the switching expression of LPA and LPA determine the hematic homeostasis of mammalian megakaryocytic-erythroid lineage. In vitro colony-forming unit assays of murine progenitors reveal that LPA agonist GRI reduces the erythroblast differentiation potential of CMP. In contrast, LPA agonist OMPT increases the production of erythrocytes from megakaryocyte-erythrocyte progenitor cells (MEP). In addition, treatment with GRI reduces the erythroid, CMP, and MEP populations in mice, indicating that LPA predominantly inhibits myeloid differentiation at an early stage. In contrast, activation of LPA increases the production of terminally differentiated erythroid cells through activation of erythropoietic transcriptional factor. We also demonstrate that the LPA signaling is essential for restoration of phenylhydrazine (PHZ)-induced acute hemolytic anemia in mice and correlates to erythropoiesis impairment of Hutchinson-Gilford progeria Symptom (HGPS) premature aging expressed K562 model. Our results reveal the distinct roles of LPA and LPA at different stages of hematopoiesis in vivo, providing potentiated therapeutic strategies of anemia treatment.
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http://dx.doi.org/10.1016/j.bbalip.2020.158818DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7683362PMC
January 2021

The role of extracellular vesicles in prostate cancer with clinical applications.

Endocr Relat Cancer 2020 05;27(5):R133-R144

Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

In mammalian cells, extracellular vesicles (EVs) derived from the endosomal system carry many different kinds of bioactive molecule to deliver to recipient cells in a paracrine or endocrine manner. EVs can mediate local and systemic intercellular communications, including reeducating stromal cells, remodeling the architecture of the tumor microenvironment, modulating cancer metabolism and metastases, or even conferring drug resistance. Because the molecular and functional characteristics of prostate cancer (PCa) evolve over time, the bioactive molecule profiles/signatures of tumor-derived EVs (TDEs) reflect the real-time status of cancer cells. TDEs appear to be valuable diagnostic and prognostic biomarkers as well as potential therapeutic vehicles, suggesting their essential role in precision medicine of disease management. We summarized critical aspects of TDEs in PCa and discussed their potential clinical applications.
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http://dx.doi.org/10.1530/ERC-20-0021DOI Listing
May 2020

Multi-domain cognitive assessment of male mice shows space radiation is not harmful to high-level cognition and actually improves pattern separation.

Sci Rep 2020 02 17;10(1):2737. Epub 2020 Feb 17.

Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA.

Astronauts on interplanetary missions - such as to Mars - will be exposed to space radiation, a spectrum of highly-charged, fast-moving particles that includes Fe and Si. Earth-based preclinical studies show space radiation decreases rodent performance in low- and some high-level cognitive tasks. Given astronaut use of touchscreen platforms during training and space flight and given the ability of rodent touchscreen tasks to assess functional integrity of brain circuits and multiple cognitive domains in a non-aversive way, here we exposed 6-month-old C57BL/6J male mice to whole-body space radiation and subsequently assessed them on a touchscreen battery. Relative to Sham treatment, Fe irradiation did not overtly change performance on tasks of visual discrimination, reversal learning, rule-based, or object-spatial paired associates learning, suggesting preserved functional integrity of supporting brain circuits. Surprisingly, Fe irradiation improved performance on a dentate gyrus-reliant pattern separation task; irradiated mice learned faster and were more accurate than controls. Improved pattern separation performance did not appear to be touchscreen-, radiation particle-, or neurogenesis-dependent, as Fe and Si irradiation led to faster context discrimination in a non-touchscreen task and Fe decreased new dentate gyrus neurons relative to Sham. These data urge revisitation of the broadly-held view that space radiation is detrimental to cognition.
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http://dx.doi.org/10.1038/s41598-020-59419-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7026431PMC
February 2020

DNA-dependent protein kinase in telomere maintenance and protection.

Cell Mol Biol Lett 2020 17;25. Epub 2020 Jan 17.

3Department of Radiation Oncology, University of Texas Southwestern Medical Center, 2201 Inwood Rd., Dallas, TX 75390-9187 USA.

This review focuses on DNA-dependent protein kinase (DNA-PK), which is the key regulator of canonical non-homologous end-joining (NHEJ), the predominant mechanism of DNA double-strand break (DSB) repair in mammals. DNA-PK consists of the DNA-binding Ku70/80 heterodimer and the catalytic subunit DNA-PKcs. They assemble at DNA ends, forming the active DNA-PK complex, which initiates NHEJ-mediated DSB repair. Paradoxically, both Ku and DNA-PKcs are associated with telomeres, and they play crucial roles in protecting the telomere against fusions. Herein, we discuss possible mechanisms and contributions of Ku and DNA-PKcs in telomere regulation.
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http://dx.doi.org/10.1186/s11658-020-0199-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6969447PMC
November 2020

RUVBL1/RUVBL2 ATPase Activity Drives PAQosome Maturation, DNA Replication and Radioresistance in Lung Cancer.

Cell Chem Biol 2020 01 26;27(1):105-121.e14. Epub 2019 Dec 26.

Eugene McDermott Center for Human Growth and Development, UT Southwestern Medical Center, Dallas, TX 75390, USA; Department of Pharmacology, UT Southwestern Medical Center, Dallas, TX 75390, USA; Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, TX 75390, USA. Electronic address:

RUVBL1 and RUVBL2 (collectively RUVBL1/2) are essential AAA+ ATPases that function as co-chaperones and have been implicated in cancer. Here we investigated the molecular and phenotypic role of RUVBL1/2 ATPase activity in non-small cell lung cancer (NSCLC). We find that RUVBL1/2 are overexpressed in NSCLC patient tumors, with high expression associated with poor survival. Utilizing a specific inhibitor of RUVBL1/2 ATPase activity, we show that RUVBL1/2 ATPase activity is necessary for the maturation or dissociation of the PAQosome, a large RUVBL1/2-dependent multiprotein complex. We also show that RUVBL1/2 have roles in DNA replication, as inhibition of its ATPase activity can cause S-phase arrest, which culminates in cancer cell death via replication catastrophe. While in vivo pharmacological inhibition of RUVBL1/2 results in modest antitumor activity, it synergizes with radiation in NSCLC, but not normal cells, an attractive property for future preclinical development.
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http://dx.doi.org/10.1016/j.chembiol.2019.12.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048778PMC
January 2020

Vanillin derivative VND3207 activates DNA-PKcs conferring protection against radiation-induced intestinal epithelial cells injury in vitro and in vivo.

Toxicol Appl Pharmacol 2020 01 9;387:114855. Epub 2019 Dec 9.

State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Medical College of Soochow University, Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China. Electronic address:

Vanillin is a natural compound endowed with antioxidant and anti-mutagenic properties. We previously identified the vanillin derivative VND3207 with strong radio-protective and antioxidant effects and found that VND3207 confers survival benefit and protection against radiation-induced intestinal injury (RIII) in mice. We also observed that VND3207 treatment enhanced the expression level of the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) in human lymphoblastoid cells with or without γ-irradiation. DNA-PKcs is a critical component of DNA double strand break repair pathway and also regulates mitotic progression by stabilizing spindle formation and preventing mitotic catastrophe in response to DNA damage. In the present study, we found that VND3207 protected intestinal epithelial cells in vitro against ionizing radiation by promoting cell proliferation and inhibiting cell apoptosis. In addition, VND3207 promoted DNA-PKcs activity by increasing autophosphorylation at S2056 site. Consistent with this, VND3207 significantly decreased the number of γH2AX foci and mitotic catastrophe after radiation. DNA-PKcs deficiency abolished these VND3207 radio-protective effects, indicating that DNA-PKcs activation is essential for VND3207 activity. In conclusion, VND3207 promoted intestinal repair following radiation injury by regulating the DNA-PKcs pathway.
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http://dx.doi.org/10.1016/j.taap.2019.114855DOI Listing
January 2020

Lysophosphatidic acid receptor LPA prevents oxidative stress and cellular senescence in Hutchinson-Gilford progeria syndrome.

Aging Cell 2020 01 12;19(1):e13064. Epub 2019 Nov 12.

Department of Life Science, National Taiwan University, Taipei, Taiwan.

Hutchinson-Gilford progeria syndrome (HGPS) is a rare laminopathy that produces a mutant form of prelamin A, known as Progerin, resulting in premature aging. HGPS cells show morphological abnormalities of the nuclear membrane, reduced cell proliferation rates, accumulation of reactive oxygen species (ROS), and expression of senescence markers. Lysophosphatidic acid (LPA) is a growth factor-like lipid mediator that regulates various physiological functions via activating multiple LPA G protein-coupled receptors. Here, we study the roles of LPA and LPA receptors in premature aging. We report that the protein level of LPA was highly downregulated through internalization and the lysosomal degradation pathway in Progerin-transfected HEK293 cells. By treating Progerin HEK293 cells with an LPA agonist (OMPT, 1-Oleoyl-2-O-methyl-rac-glycerophosphothionate) and performing shRNA knockdown of the Lpa3r transcript in these cells, we showed that LPA activation increased expression levels of antioxidant enzymes, consequently inhibiting ROS accumulation and ameliorating cell senescence. LPA was shown to be downregulated in HGPS patient fibroblasts through the lysosomal pathway, and it was shown to be crucial for ameliorating ROS accumulation and cell senescence in fibroblasts. Moreover, in a zebrafish model, LPA deficiency was sufficient to cause premature aging phenotypes in multiple organs, as well as a shorter lifespan. Taken together, these findings identify the decline of LPA as a key contributor to the premature aging phenotypes of HGPS cells and zebrafish.
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http://dx.doi.org/10.1111/acel.13064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6974717PMC
January 2020

The vanillin derivative VND3207 protects intestine against radiation injury by modulating p53/NOXA signaling pathway and restoring the balance of gut microbiota.

Free Radic Biol Med 2019 12 30;145:223-236. Epub 2019 Sep 30.

State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Medical College of Soochow University, Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou, 215123, China. Electronic address:

The intestine is a highly radiosensitive tissue that is susceptible to structural and functional damage due to systemic as well as localized radiation exposure. Unfortunately, no effective prophylactic or therapeutic agents are available at present to manage radiation-induced intestinal injuries. We observed that the vanillin derivative VND3207 improved the survival of lethally irradiated mice by promoting intestinal regeneration and increasing the number of surviving crypts. Pre-treatment with VND3207 significantly increased the number of Lgr5 intestinal stem cells (ISCs) and their daughter cells, the transient Ki67 proliferating cells. Mechanistically, VND3207 decreased oxidative DNA damage and lipid peroxidation and maintained endogenous antioxidant status by increasing the level of superoxide dismutase and total antioxidant capacity. In addition, VND3207 maintained appropriate levels of activated p53 that triggered cell cycle arrest but were not sufficient to induce NOXA-mediated apoptosis, thus ensuring DNA damage repair in the irradiated small intestinal crypt cells. Furthermore, VND3207 treatment restores the intestinal bacterial flora structures altered by TBI exposure. In conclusion, VND3207 promoted intestinal repair following radiation injury by reducing reactive oxygen species-induced DNA damage and modulating appropriate levels of activated p53 in intestinal epithelial cells.
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http://dx.doi.org/10.1016/j.freeradbiomed.2019.09.035DOI Listing
December 2019

A nanodroplet cell processing platform facilitating drug synergy evaluations for anti-cancer treatments.

Sci Rep 2019 07 12;9(1):10120. Epub 2019 Jul 12.

Department of Electrical Engineering, Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan.

Therapeutic drug synergism intervened in cancer treatments has been demonstrated to be more effective than using a single effector. However, it remains inherently challenging, with a limited cell count from tumor samples, to achieve potent personalized drug cocktails. To address the issue above, we herein present a nanodroplet cell processing platform. The platform incorporates an automatic nanodroplet dispenser with cell array ParaStamp chips, which were fabricated by a new wax stamping approach derived from laser direct writing. Such approach enables not only the on-demand de-wetting with hydrophobic wax films on substrates but also the mask-less fabrication of non-planar microstructures (i.e. no photolithography process). The ParaStamp chip was pre-occupied with anti-cancer drugs and their associate mixtures, enabling for the spatially addressable screening of optimal drug combinations simultaneously. Each droplet with a critical volume of 200 nl containing with 100 cells was utilized. Results revealed that the optimal combination reduces approximate 28-folds of conducted doses compared with single drugs. Tumor inhibition with the optimally selected drug combination was further confirmed by using PC-3 tumor-bearing mouse models. Together, the nanodroplet cell processing platform could therefore offer new opportunities to power the personalized cancer medicine at early-stage drug screening and discovery.
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http://dx.doi.org/10.1038/s41598-019-46502-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6625988PMC
July 2019

Author Correction: CPS1 maintains pyrimidine pools and DNA synthesis in KRAS/LKB1-mutant lung cancer cells.

Nature 2019 May;569(7756):E4

Children's Medical Center Research Institute, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.

Further analysis has revealed that the signal reported in Extended Data Fig. 1c of this Letter is attributed to phosphorylethanolamine, not carbamoyl phosphate. A newly developed derivatization method revealed that the level of carbamoyl phosphate in these NSCLC extracts is below the detection threshold of approximately 10 nanomoles. These findings do not alter the overall conclusions of the Letter; see associated Amendment for full details. The Letter has not been corrected online.
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http://dx.doi.org/10.1038/s41586-019-1133-3DOI Listing
May 2019

Downregulation of Human DAB2IP Gene Expression in Renal Cell Carcinoma Results in Resistance to Ionizing Radiation.

Clin Cancer Res 2019 07 18;25(14):4542-4551. Epub 2019 Apr 18.

Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas.

Purpose: Renal cell carcinoma (RCC) is known to be highly radioresistant but the mechanisms associated with radioresistance have remained elusive. We found DOC-2/DAB2 interactive protein (DAB2IP) frequently downregulated in RCC, is associated with radioresistance. In this study, we investigated the underlying mechanism regulating radioresistance by DAB2IP and developed appropriate treatment.

Experimental Design: Several RCC lines with or without DAB2IP expression were irradiated with ionizing radiation (IR) for determining their radiosensitivities based on colony formation assay. To investigate the underlying regulatory mechanism of DAB2IP, immunoprecipitation-mass spectrometry was performed to identify DAB2IP-interactive proteins. PARP-1 expression and enzymatic activity were determined using qRT-PCR, Western blot analysis, and ELISA. ubiquitination assay was used to test PARP-1 degradation. Furthermore, mice xenograft model and patient-derived xenograft (PDX) model were used to determine the effect of combination therapy to sensitizing tumors to IR.

Results: We notice that DAB2IP-deficient RCC cells acquire IR-resistance. Mechanistically, DAB2IP can form a complex with PARP-1 and E3 ligases that is responsible for degrading PARP-1. Indeed, elevated PARP-1 levels are associated with the IR resistance in RCC cells. Furthermore, PARP-1 inhibitor can enhance the IR response of either RCC xenograft model or PDX model.

Conclusions: In this study, we unveil that loss of DAB2IP resulted in elevated PARP-1 protein is associated with IR-resistance in RCC. These results provide a new targeting strategy to improve the efficacy of radiotherapy of RCC.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-3004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6635020PMC
July 2019

High Glucose Induces VEGF-C Expression via the LPA1/3-Akt-ROS-LEDGF Signaling Axis in Human Prostate Cancer PC-3 Cells.

Cell Physiol Biochem 2018 12;50(2):597-611. Epub 2018 Oct 12.

Department of Life Science and Electrical Engineering, National Taiwan University, Taipei, Taiwan.

Background/aims: Hyperglycemia has been shown to increase the incidence and metastasis in various types of cancers. However, the correlation between hyperglycemia and lymphatic metastasis in prostate cancer (PCa) remains unclear. Our previous study demonstrated that lysophosphatidic acid (LPA) enhances vascular endothelial growth factor-C (VEGF-C) expression, a lymphangiogenic factor, through activating it receptors LPA1/3 in prostate cancer (PCa) cells. Moreover, hyperglycemia up-regulates autotaxin (ATX) expression, a LPA-generating enzyme. Therefore, we propose that high glucose promotes VEGF-C expression through LPA signaling in PCa cells.

Methods: Pharmacological inhibitors and siRNAs were utilized to investigate the molecular mechanism of high glucose-induced VEGF-C expression. Real-time PCR and Western blot were used to determine the mRNA and protein expressions, respectively. Cellular bioenergetics analysis was performed to determine the glycolysis levels.

Results: We demonstrated that the expressions of VEGF-C, ATX, and calreticulin were increased upon high glucose treatments in PC-3 cells. Moreover, high glucose-induced VEGF-C expression was mediated through the LPA1/3, PLC, Akt, ROS and LEDGF-dependent pathways. Additionally, high glucose enhanced the aerobic glycolysis via LPA1/3.

Conclusion: These results indicated that hyperglycemia leads to LPA synthesis, and subsequent promoting pathological consequence of PCa. These novel findings could potentially provide new strategies for PCa treatments.
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http://dx.doi.org/10.1159/000494177DOI Listing
November 2018

Whole-Body C Irradiation Transiently Decreases Mouse Hippocampal Dentate Gyrus Proliferation and Immature Neuron Number, but Does Not Change New Neuron Survival Rate.

Int J Mol Sci 2018 Oct 9;19(10). Epub 2018 Oct 9.

Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.

High-charge and -energy (HZE) particles comprise space radiation and they pose a challenge to astronauts on deep space missions. While exposure to most HZE particles decreases neurogenesis in the hippocampus-a brain structure important in memory-prior work suggests that C does not. However, much about C's influence on neurogenesis remains unknown, including the time course of its impact on neurogenesis. To address this knowledge gap, male mice (9⁻11 weeks of age) were exposed to whole-body C irradiation 100 cGy (IRR; 1000 MeV/n; 8 kEV/µm) or Sham treatment. To birthdate dividing cells, mice received BrdU i.p. 22 h post-irradiation and brains were harvested 2 h (Short-Term) or three months (Long-Term) later for stereological analysis indices of dentate gyrus neurogenesis. For the Short-Term time point, IRR mice had fewer Ki67, BrdU, and doublecortin (DCX) immunoreactive (+) cells versus Sham mice, indicating decreased proliferation (Ki67, BrdU) and immature neurons (DCX). For the Long-Term time point, IRR and Sham mice had similar Ki67+ and DCX+ cell numbers, suggesting restoration of proliferation and immature neurons 3 months post-C irradiation. IRR mice had fewer surviving BrdU+ cells versus Sham mice, suggesting decreased cell survival, but there was no difference in BrdU+ cell survival rate when compared within treatment and across time point. These data underscore the ability of neurogenesis in the mouse brain to recover from the detrimental effect of C exposure.
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http://dx.doi.org/10.3390/ijms19103078DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6213859PMC
October 2018

Facilitating tumor spheroid-based bioassays and in vitro blood vessel modeling via bioinspired self-formation microstructure devices.

Lab Chip 2018 08;18(16):2453-2465

Department of Electrical Engineering, Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan, Republic of China.

Non-planar microstructure-based tissue culture devices have emerged as powerful tools to mimic in vivo physiological microenvironments in a wide range of medical applications. Here we report a spontaneous aqueous molding approach - inspired by Stenocara gracilipes beetles - to rapidly fabricate non-planar microstructure devices for facilitating tissue-based bioassays. The device fabrication is determined from the self-assembled liquid morphology, which is induced by condensation or guided by surface tension. Through experiments and modeling, we reveal that the molding mainly comprises two typical circular and striped domains, highlighting versatile applications for bioengineering. In addition, the molding characteristic is dependent on the geometry of the patterned wetting surfaces, the working volume of the liquid, and the interaction between the liquid and the substrate. The theoretical model, based on the geometry of the patterned liquid, is highly consistent with experimental data. We also demonstrate that our approach can facilitate the culturing of tumor spheroids incorporated with biomimic nano-cilia, rapid high-throughput drug screening, tumor spheroid migration assay, and in vitro modeling of blood vessels. Remarkably, the delivery of multiple concentrations of drugs and their associate mixtures (a total of 25 test spots in one device) can be carried out simultaneously within seconds. Taken together, these insights may offer new opportunities to tailor non-planar microstructures, and our proposed methodology can be applicable for the emerging needs in tumor cell biology and tissue engineering.
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http://dx.doi.org/10.1039/c8lc00423dDOI Listing
August 2018

PIDD mediates the association of DNA-PKcs and ATR at stalled replication forks to facilitate the ATR signaling pathway.

Nucleic Acids Res 2018 02;46(4):1847-1859

Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA.

The DNA-dependent protein kinase (DNA-PK), consisting of the DNA binding Ku70/80 heterodimer and the catalytic subunit DNA-PKcs, has been well characterized in the non-homologous end-joining mechanism for DNA double strand break (DSB) repair and radiation resistance. Besides playing a role in DSB repair, DNA-PKcs is required for the cellular response to replication stress and participates in the ATR-Chk1 signaling pathway. However, the mechanism through which DNA-PKcs is recruited to stalled replication forks is still unclear. Here, we report that the apoptosis mediator p53-induced protein with a death domain (PIDD) is required to promote DNA-PKcs activity in response to replication stress. PIDD is known to interact with PCNA upon UV-induced replication stress. Our results demonstrate that PIDD is required to recruit DNA-PKcs to stalled replication forks through direct binding to DNA-PKcs at the N' terminal region. Disruption of the interaction between DNA-PKcs and PIDD not only compromises the ATR association and regulation of DNA-PKcs, but also the ATR signaling pathway, intra-S-phase checkpoint and cellular resistance to replication stress. Taken together, our results indicate that PIDD, but not the Ku heterodimer, mediates the DNA-PKcs activity at stalled replication forks and facilitates the ATR signaling pathway in the cellular response to replication stress.
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http://dx.doi.org/10.1093/nar/gkx1298DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5829747PMC
February 2018

Whole-Body Exposure to Si-Radiation Dose-Dependently Disrupts Dentate Gyrus Neurogenesis and Proliferation in the Short Term and New Neuron Survival and Contextual Fear Conditioning in the Long Term.

Radiat Res 2017 11 25;188(5):532-551. Epub 2017 Sep 25.

Department of a   Psychiatry, UT Southwestern Medical Center, Dallas, Texas.

Astronauts traveling to Mars will be exposed to chronic low doses of galactic cosmic space radiation, which contains highly charged, high-energy (HZE) particles. Fe-HZE-particle exposure decreases hippocampal dentate gyrus (DG) neurogenesis and disrupts hippocampal function in young adult rodents, raising the possibility of impaired astronaut cognition and risk of mission failure. However, far less is known about how exposure to other HZE particles, such as Si, influences hippocampal neurogenesis and function. To compare the influence of Si exposure on indices of neurogenesis and hippocampal function with previous studies on Fe exposure, 9-week-old C57BL/6J and Nestin-GFP mice (NGFP; made and maintained for 10 or more generations on a C57BL/6J background) received whole-body Si-particle-radiation exposure (0, 0.2 and 1 Gy, 300 MeV/n, LET 67 KeV/μ, dose rate 1 Gy/min). For neurogenesis assessment, the NGFP mice were injected with the mitotic marker BrdU at 22 h postirradiation and brains were examined for indices of hippocampal proliferation and neurogenesis, including Ki67, BrdU, BrdUNeuN and DCX cell numbers at short- and long-term time points (24 h and 3 months postirradiation, respectively). In the short-term group, stereology revealed fewer Ki67, BrdU and DCX cells in 1-Gy-irradiated group relative to nonirradiated control mice, fewer Ki67 and DCX cells in 0.2 Gy group relative to control group and fewer BrdU and DCX cells in 1 Gy group relative to 0.2 Gy group. In contrast to the clearly observed radiation-induced, dose-dependent reductions in the short-term group across all markers, only a few neurogenesis indices were changed in the long-term irradiated groups. Notably, there were fewer surviving BrdU cells in the 1 Gy group relative to 0- and 0.2-Gy-irradiated mice in the long-term group. When the short- and long-term groups were analyzed by sex, exposure to radiation had a similar effect on neurogenesis indices in male and female mice, although only male mice showed fewer surviving BrdU cells in the long-term group. Fluorescent immunolabeling and confocal phenotypic analysis revealed that most surviving BrdU cells in the long-term group expressed the neuronal marker NeuN, definitively confirming that exposure to 1 Gy Si radiation decreased the number of surviving adult-generated neurons in male mice relative to both 0- and 0.2-Gy-irradiated mice. For hippocampal function assessment, 9-week-old male C57BL/6J mice received whole-body Si-particle exposure and were then assessed long-term for performance on contextual and cued fear conditioning. In the context test the animals that received 0.2 Gy froze less relative to control animals, suggesting decreased hippocampal-dependent function. However, in the cued fear conditioning test, animals that received 1 Gy froze more during the pretone portion of the test, relative to controls and 0.2-Gy-irradiated mice, suggesting enhanced anxiety. Compared to previously reported studies, these data suggest that Si-radiation exposure damages neurogenesis, but to a lesser extent than Fe radiation and that low-dose Si exposure induces abnormalities in hippocampal function, disrupting fear memory but also inducing anxiety-like behavior. Furthermore, exposure to Si radiation decreased new neuron survival in long-term male groups but not females suggests that sex may be an important factor when performing brain health risk assessment for astronauts traveling in space.
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http://dx.doi.org/10.1667/RR14797.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5901735PMC
November 2017

Androgen Receptor Variants Mediate DNA Repair after Prostate Cancer Irradiation.

Cancer Res 2017 09 28;77(18):4745-4754. Epub 2017 Jul 28.

Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas.

In prostate cancer, androgen deprivation therapy (ADT) enhances the cytotoxic effects of radiotherapy. This effect is associated with weakening of the DNA damage response (DDR) normally supported by the androgen receptor. As a significant number of patients will fail combined ADT and radiotherapy, we hypothesized that DDR may be driven by androgen receptor splice variants (ARV) induced by ADT. Investigating this hypothesis, we found that ARVs increase the clonogenic survival of prostate cancer cells after irradiation in an ADT-independent manner. Notably, prostate cancer cell irradiation triggers binding of ARV to the catalytic subunit of the critical DNA repair kinase DNA-PK. Pharmacologic inhibition of DNA-PKc blocked this interaction, increased DNA damage, and elevated prostate cancer cell death after irradiation. Our findings provide a mechanistic rationale for therapeutic targeting of DNA-PK in the context of combined ADT and radiotherapy as a strategy to radiosensitize clinically localized prostate cancer. .
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http://dx.doi.org/10.1158/0008-5472.CAN-17-0164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5600864PMC
September 2017

Three-dimensional spheroid culture targeting versatile tissue bioassays using a PDMS-based hanging drop array.

Sci Rep 2017 06 29;7(1):4363. Epub 2017 Jun 29.

Department of Life Science, National Taiwan University, Taipei, Taiwan, ROC.

Biomaterial-based tissue culture platforms have emerged as useful tools to mimic in vivo physiological microenvironments in experimental cell biology and clinical studies. We describe herein a three-dimensional (3D) tissue culture platform using a polydimethylsiloxane (PDMS)-based hanging drop array (PDMS-HDA) methodology. Multicellular spheroids can be achieved within 24 h and further boosted by incorporating collagen fibrils in PDMS-HDA. In addition, the spheroids generated from different human tumor cells exhibited distinct sensitivities toward drug chemotherapeutic agents and radiation as compared with two-dimensional (2D) cultures that often lack in vivo-like biological insights. We also demonstrated that multicellular spheroids may enable key hallmarks of tissue-based bioassays, including drug screening, tumor dissemination, cell co-culture, and tumor invasion. Taken together, these results offer new opportunities not only to achieve the active control of 3D multicellular spheroids on demand, but also to establish a rapid and cost-effective platform to study anti-cancer therapeutics and tumor microenvironments.
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http://dx.doi.org/10.1038/s41598-017-04718-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5491519PMC
June 2017

CPS1 maintains pyrimidine pools and DNA synthesis in KRAS/LKB1-mutant lung cancer cells.

Nature 2017 06 24;546(7656):168-172. Epub 2017 May 24.

Children's Medical Center Research Institute, UT Southwestern Medical Center, Dallas, Texas 75390, USA.

Metabolic reprogramming by oncogenic signals promotes cancer initiation and progression. The oncogene KRAS and tumour suppressor STK11, which encodes the kinase LKB1, regulate metabolism and are frequently mutated in non-small-cell lung cancer (NSCLC). Concurrent occurrence of oncogenic KRAS and loss of LKB1 (KL) in cells specifies aggressive oncological behaviour. Here we show that human KL cells and tumours share metabolomic signatures of perturbed nitrogen handling. KL cells express the urea cycle enzyme carbamoyl phosphate synthetase-1 (CPS1), which produces carbamoyl phosphate in the mitochondria from ammonia and bicarbonate, initiating nitrogen disposal. Transcription of CPS1 is suppressed by LKB1 through AMPK, and CPS1 expression correlates inversely with LKB1 in human NSCLC. Silencing CPS1 in KL cells induces cell death and reduces tumour growth. Notably, cell death results from pyrimidine depletion rather than ammonia toxicity, as CPS1 enables an unconventional pathway of nitrogen flow from ammonia into pyrimidines. CPS1 loss reduces the pyrimidine to purine ratio, compromises S-phase progression and induces DNA-polymerase stalling and DNA damage. Exogenous pyrimidines reverse DNA damage and rescue growth. The data indicate that the KL oncological genotype imposes a metabolic vulnerability related to a dependence on a cross-compartmental pathway of pyrimidine metabolism in an aggressive subset of NSCLC.
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http://dx.doi.org/10.1038/nature22359DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5472349PMC
June 2017

Imaging of Fluorescently Tagged ATM Kinase at the Sites of DNA Double Strand Breaks.

Methods Mol Biol 2017 ;1599:277-285

Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, 2201 Inwood Road, Dallas, TX, 75390, USA.

The combination of live cell imaging and laser micro-irradiation is an important technique to investigate the recruitment and kinetics of DNA repair molecules to DNA damage sites. In this chapter, we describe the detailed methods to study the dynamics of fluorescently tagged ATM protein kinase at laser-induced DNA double strand break (DSB) sites. The same protocol can be applied to analyze the recruitment and kinetics of other potential or known DNA repair proteins to DSB sites.
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http://dx.doi.org/10.1007/978-1-4939-6955-5_20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6085091PMC
February 2018

ParaStamp and Its Applications to Cell Patterning, Drug Synergy Screening, and Rewritable Devices for Droplet Storage.

Adv Biosyst 2017 May 24;1(5). Epub 2017 Apr 24.

Department of Life Science, National Taiwan University, Taipei 10617, Taiwan, R.O.C.

Engineered materials have been employed as versatile tools to explore the fundamental cell biology/drug development as well as to approach the intelligent device, thereby becoming the key components in modern technology. Herein, a ParaStamp technique has been revealed to possess applications for cell patterning, drug screening, and rewritable functional patterning. The ParaStamp includes a micropatterned PDMS master and a liquid-phased paraffin oil generated at high temperature, which can transfer the patterned paramembrane onto varied material surfaces, such as glass, polystyrene, and flexible foil. This technique is simple and cost-effective to meet the high-throughput requirement for industries. Taken together, our findings herein should have general insights in cell biology, biodetection, and development of smart hydrophobic surface.
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http://dx.doi.org/10.1002/adbi.201700048DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6171521PMC
May 2017

Coordination of the Ser2056 and Thr2609 Clusters of DNA-PKcs in Regulating Gamma Rays and Extremely Low Fluencies of Alpha-Particle Irradiation to G/G Phase Cells.

Radiat Res 2017 02 24;187(2):259-267. Epub 2017 Jan 24.

d   Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts 02115.

The catalytic subunit of DNA dependent protein kinase (DNA-PKcs) and its kinase activity are critical for mediation of non-homologous end-joining (NHEJ) of DNA double-strand breaks (DSB) in mammalian cells after gamma-ray irradiation. Additionally, DNA-PKcs phosphorylations at the T2609 cluster and the S2056 cluster also affect DSB repair and cellular sensitivity to gamma radiation. Previously we reported that phosphorylations within these two regions affect not only NHEJ but also homologous recombination repair (HRR) dependent DSB repair. In this study, we further examine phenotypic effects on cells bearing various combinations of mutations within either or both regions. Effects studied included cell killing as well as chromosomal aberration induction after 0.5-8 Gy gamma-ray irradiation delivered to synchronized cells during the G/G phase of the cell cycle. Blocking phosphorylation within the T2609 cluster was most critical regarding sensitization and depended on the number of available phosphorylation sites. It was also especially interesting that only one substitution of alanine in each of the two clusters separately abolished the restoration of wild-type sensitivity by DNA-PKcs. Similar patterns were seen for induction of chromosomal aberrations, reflecting their connection to cell killing. To study possible change in coordination between HRR and NHEJ directed repair in these DNA-PKcs mutant cell lines, we compared the induction of sister chromatid exchanges (SCEs) by very low fluencies of alpha particles with mutant cells defective in the HRR pathway that is required for induction of SCEs. Levels of true SCEs induced by very low fluence of alpha-particle irradiation normally seen in wild-type cells were only slightly decreased in the S2056 cluster mutants, but were completely abolished in the T2609 cluster mutants and were indistinguishable from levels seen in HRR deficient cells. Again, a single substitution in the S2056 together with a single substitution in the T2609 cluster abolished SCE formation and thus also effectively interferes with HRR.
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http://dx.doi.org/10.1667/RR14679.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5319878PMC
February 2017

Tumor suppressor protein DAB2IP participates in chromosomal stability maintenance through activating spindle assembly checkpoint and stabilizing kinetochore-microtubule attachments.

Nucleic Acids Res 2016 Oct 27;44(18):8842-8854. Epub 2016 Aug 27.

Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA

Defects in kinetochore-microtubule (KT-MT) attachment and the spindle assembly checkpoint (SAC) during cell division are strongly associated with chromosomal instability (CIN). CIN has been linked to carcinogenesis, metastasis, poor prognosis and resistance to cancer therapy. We previously reported that the DAB2IP is a tumor suppressor, and that loss of DAB2IP is often detected in advanced prostate cancer (PCa) and is indicative of poor prognosis. Here, we report that the loss of DAB2IP results in impaired KT-MT attachment, compromised SAC and aberrant chromosomal segregation. We discovered that DAB2IP directly interacts with Plk1 and its loss inhibits Plk1 kinase activity, thereby impairing Plk1-mediated BubR1 phosphorylation. Loss of DAB2IP decreases the localization of BubR1 at the kinetochore during mitosis progression. In addition, the reconstitution of DAB2IP enhances the sensitivity of PCa cells to microtubule stabilizing drugs (paclitaxel, docetaxel) and Plk1 inhibitor (BI2536). Our findings demonstrate a novel function of DAB2IP in the maintenance of KT-MT structure and SAC regulation during mitosis which is essential for chromosomal stability.
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http://dx.doi.org/10.1093/nar/gkw746DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5062997PMC
October 2016

Transcriptional elongation requires DNA break-induced signalling.

Nat Commun 2015 Dec 16;6:10191. Epub 2015 Dec 16.

Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA.

We have previously shown that RNA polymerase II (Pol II) pause release and transcriptional elongation involve phosphorylation of the factor TRIM28 by the DNA damage response (DDR) kinases ATM and DNA-PK. Here we report a significant role for DNA breaks and DDR signalling in the mechanisms of transcriptional elongation in stimulus-inducible genes in humans. Our data show the enrichment of TRIM28 and γH2AX on serum-induced genes and the important function of DNA-PK for Pol II pause release and transcriptional activation-coupled DDR signalling on these genes. γH2AX accumulation decreases when P-TEFb is inhibited, confirming that DDR signalling results from transcriptional elongation. In addition, transcriptional elongation-coupled DDR signalling involves topoisomerase II because inhibiting this enzyme interferes with Pol II pause release and γH2AX accumulation. Our findings propose that DDR signalling is required for effective Pol II pause release and transcriptional elongation through a novel mechanism involving TRIM28, DNA-PK and topoisomerase II.
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http://dx.doi.org/10.1038/ncomms10191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703865PMC
December 2015

FANCD2 and REV1 cooperate in the protection of nascent DNA strands in response to replication stress.

Nucleic Acids Res 2015 Sep 17;43(17):8325-39. Epub 2015 Jul 17.

Key Laboratory of Genomics and Precision Medicine, China Gastrointestinal Cancer Research Center, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China

REV1 is a eukaryotic member of the Y-family of DNA polymerases involved in translesion DNA synthesis and genome mutagenesis. Recently, REV1 is also found to function in homologous recombination. However, it remains unclear how REV1 is recruited to the sites where homologous recombination is processed. Here, we report that loss of mammalian REV1 results in a specific defect in replication-associated gene conversion. We found that REV1 is targeted to laser-induced DNA damage stripes in a manner dependent on its ubiquitin-binding motifs, on RAD18, and on monoubiquitinated FANCD2 (FANCD2-mUb) that associates with REV1. Expression of a FANCD2-Ub chimeric protein in RAD18-depleted cells enhances REV1 assembly at laser-damaged sites, suggesting that FANCD2-mUb functions downstream of RAD18 to recruit REV1 to DNA breaks. Consistent with this suggestion we found that REV1 and FANCD2 are epistatic with respect to sensitivity to the double-strand break-inducer camptothecin. REV1 enrichment at DNA damage stripes also partially depends on BRCA1 and BRCA2, components of the FANCD2/BRCA supercomplex. Intriguingly, analogous to FANCD2-mUb and BRCA1/BRCA2, REV1 plays an unexpected role in protecting nascent replication tracts from degradation by stabilizing RAD51 filaments. Collectively these data suggest that REV1 plays multiple roles at stalled replication forks in response to replication stress.
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http://dx.doi.org/10.1093/nar/gkv737DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4787816PMC
September 2015

DNA-PKcs phosphorylates hnRNP-A1 to facilitate the RPA-to-POT1 switch and telomere capping after replication.

Nucleic Acids Res 2015 Jul 20;43(12):5971-83. Epub 2015 May 20.

Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA

The heterogeneous nuclear ribonucleoprotein A1 (hnRNP-A1) has been implicated in telomere protection and telomerase activation. Recent evidence has further demonstrated that hnRNP-A1 plays a crucial role in maintaining newly replicated telomeric 3' overhangs and facilitating the switch from replication protein A (RPA) to protection of telomeres 1 (POT1). The role of hnRNP-A1 in telomere protection also involves DNA-dependent protein kinase catalytic subunit (DNA-PKcs), although the detailed regulation mechanism has not been clear. Here we report that hnRNP-A1 is phosphorylated by DNA-PKcs during the G2 and M phases and that DNA-PK-dependent hnRNP-A1 phosphorylation promotes the RPA-to-POT1 switch on telomeric single-stranded 3' overhangs. Consequently, in cells lacking hnRNP-A1 or DNA-PKcs-dependent hnRNP-A1 phosphorylation, impairment of the RPA-to-POT1 switch results in DNA damage response at telomeres during mitosis as well as induction of fragile telomeres. Taken together, our results indicate that DNA-PKcs-dependent hnRNP-A1 phosphorylation is critical for capping of the newly replicated telomeres and prevention of telomeric aberrations.
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http://dx.doi.org/10.1093/nar/gkv539DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4499152PMC
July 2015

The Catalytic Subunit of DNA-Dependent Protein Kinase Coordinates with Polo-Like Kinase 1 to Facilitate Mitotic Entry.

Neoplasia 2015 Apr;17(4):329-38

Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA. Electronic address:

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is the key regulator of the non-homologous end joining pathway of DNA double-strand break repair. We have previously reported that DNA-PKcs is required for maintaining chromosomal stability and mitosis progression. Our further investigations reveal that deficiency in DNA-PKcs activity caused a delay in mitotic entry due to dysregulation of cyclin-dependent kinase 1 (Cdk1), the key driving force for cell cycle progression through G2/M transition. Timely activation of Cdk1 requires polo-like kinase 1 (Plk1), which affects modulators of Cdk1. We found that DNA-PKcs physically interacts with Plk1 and could facilitate Plk1 activation both in vitro and in vivo. Further, DNA-PKcs-deficient cells are highly sensitive to Plk1 inhibitor BI2536, suggesting that the coordination between DNA-PKcs and Plk1 is not only crucial to ensure normal cell cycle progression through G2/M phases but also required for cellular resistance to mitotic stress. On the basis of the current study, it is predictable that combined inhibition of DNA-PKcs and Plk1 can be employed in cancer therapy strategy for synthetic lethality.
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http://dx.doi.org/10.1016/j.neo.2015.02.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4415140PMC
April 2015

NSCLC cells demonstrate differential mode of cell death in response to the combined treatment of radiation and a DNA-PKcs inhibitor.

Oncotarget 2015 Feb;6(6):3848-60

Department of Radiation Oncology, Simmons Comprehensive Cancer Center at UT Southwestern Medical Center, Dallas, TX, USA.

The current standard of care for lung cancer consists of concurrent chemotherapy and radiation. Several studies have shown that the DNA-PKcs inhibitor NU7441 is a highly potent radiosensitizer, however, the mechanism of NU7441's anti-proliferation effect has not been fully elucidated. In this study, the combined effect of NU7441 and ionizing radiation (IR) in a panel of non-small cell lung cancer cell lines (A549, H460 and H1299) has been investigated. We found that NU7441 significantly enhances the effect of IR in all cell lines. The notable findings in response to this combined treatment are (i) prolonged delay in IR-induced DNA DSB repair, (ii) induced robust G2/M checkpoint, (iii) increased aberrant mitosis followed by mitotic catastrophe specifically in H1299, (iv) dramatically induced autophagy in A549 and (v) IR-induced senescence specifically in H460. H1299 cells show greater G2 checkpoint adaptation after combined treatment, which can be attributed to higher expression level of Plk1 compared to A549 and H460. The enhanced autophagy after NU7441 treatment in A549 is possibly due to the higher endogenous expression of pS6K compared to H1299 and H460 cells. In conclusion, choice of cell death pathway is dependent on the mutation status and other genetic factors of the cells treated.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4414158PMC
http://dx.doi.org/10.18632/oncotarget.2975DOI Listing
February 2015