Publications by authors named "Swapna Joshi"

18 Publications

  • Page 1 of 1

Disruption of a GATA2, TAL1, ERG regulatory circuit promotes erythroid transition in healthy and leukemic stem cells.

Blood 2021 Jun 1. Epub 2021 Jun 1.

University of New South Wales, Sydney, Australia.

Changes in gene regulation and expression govern orderly transitions from hematopoietic stem cells to terminally differentiated blood cell types. These transitions are disrupted during leukemic transformation but knowledge of the gene regulatory changes underpinning this process is elusive. We hypothesised that identifying core gene regulatory networks in healthy hematopoietic and leukemic cells could provide insights into network alterations that perturb cell state transitions. A heptad of transcription factors (LYL1, TAL1, LMO2, FLI1, ERG, GATA2, RUNX1) bind key hematopoietic genes in human CD34+ haematopoietic stem and progenitor cells (HSPCs) and have prognostic significance in acute myeloid leukemia (AML). These factors also form a densely interconnected circuit by binding combinatorially at their own, and each other's, regulatory elements. However, their mutual regulation during normal haematopoiesis and in AML cells, and how perturbation of their expression levels influences cell fate decisions remains unclear. Here, we integrated bulk and single cell data and found that the fully connected heptad circuit identified in healthy HSPCs persists with only minor alterations in AML, and that chromatin accessibility at key heptad regulatory elements was predictive of cell identity in both healthy progenitors and in leukemic cells. The heptad factors GATA2, TAL1 and ERG formed an integrated sub-circuit that regulates stem cell to erythroid transition in both healthy and leukemic cells. Components of this triad could be manipulated to facilitate erythroid transition providing a proof of concept that such regulatory circuits could be harnessed to promote specific cell type transitions and overcome dysregulated haematopoiesis.
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http://dx.doi.org/10.1182/blood.2020009707DOI Listing
June 2021

Effect of Exclusion Diets on Symptom Severity and the Gut Microbiota in Patients with Irritable Bowel Syndrome.

Clin Gastroenterol Hepatol 2021 May 19. Epub 2021 May 19.

G Oppenheimer Center for Neurobiology of Stress and Resilience; Vatche and Tamar Manoukian Division of Digestive Diseases, David Geffen School of Medicine, University of California, Los Angeles, United States,. Electronic address:

Background & Aims: Altered fecal microbiota have been reported in IBS, although studies vary which could be due to dietary effects. Many IBS patients may eliminate certain foods because of their symptoms, which in turn may alter fecal microbiota diversity and composition. This study aims were to determine if dietary patterns were associated with IBS, symptoms, and fecal microbiota differences reported in IBS.

Methods: 346 IBS participants and 170 healthy controls (HCs) completed a Diet Checklist reflecting the diet(s) consumed most frequently. An exclusion diet was defined as a diet that eliminated food components by choice. Within this group, a gluten-free, dairy-free, or low FODMAP diet was further defined as restrictive as they are often implicated to reduce symptoms. Stool samples were obtained from 171 IBS patients and 98 HCs for 16S rRNA gene sequencing and microbial composition analysis.

Results: Having IBS symptoms was associated with consuming a restrictive diet (27.17% of IBS patients vs 7.65% of HCs; OR 3.25; 95% CI 1.66-6.75; p-value 0.006). IBS participants on an exclusion or restrictive diet reported more severe IBS symptoms (p=0.042 and p=0.029 respectively). The composition of the microbiota in IBS patients varied depending on the diet consumed. IBS participants on an exclusion diet had a greater abundance of Lachnospira and a lower abundance of Eubacterium (q-values<0.05) and those on a restrictive diet had a lower abundance of Lactobacillus (q-value <0.05).

Conclusions: Restrictive diets are likely consumed more by IBS patients than HCs to reduce GI symptom severity. Dietary patterns influence the composition of fecal microbiota and may explain some of the differences between IBS and HCs.
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http://dx.doi.org/10.1016/j.cgh.2021.05.027DOI Listing
May 2021

Dual targeting of the epigenome via FACT complex and histone deacetylase is a potent treatment strategy for DIPG.

Cell Rep 2021 Apr;35(2):108994

Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Sydney, NSW, Australia; School of Women's and Children's Health, University of New South Wales, Sydney, NSW, Australia; Kid's Cancer Centre, Sydney Children's Hospital, Randwick, NSW, Australia. Electronic address:

Diffuse intrinsic pontine glioma (DIPG) is an aggressive and incurable childhood brain tumor for which new treatments are needed. CBL0137 is an anti-cancer compound developed from quinacrine that targets facilitates chromatin transcription (FACT), a chromatin remodeling complex involved in transcription, replication, and DNA repair. We show that CBL0137 displays profound cytotoxic activity against a panel of patient-derived DIPG cultures by restoring tumor suppressor TP53 and Rb activity. Moreover, in an orthotopic model of DIPG, treatment with CBL0137 significantly extends animal survival. The FACT subunit SPT16 is found to directly interact with H3.3K27M, and treatment with CBL0137 restores both histone H3 acetylation and trimethylation. Combined treatment of CBL0137 with the histone deacetylase inhibitor panobinostat leads to inhibition of the Rb/E2F1 pathway and induction of apoptosis. The combination of CBL0137 and panobinostat significantly prolongs the survival of mice bearing DIPG orthografts, suggesting a potential treatment strategy for DIPG.
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http://dx.doi.org/10.1016/j.celrep.2021.108994DOI Listing
April 2021

Targeting reduced mitochondrial DNA quantity as a therapeutic approach in pediatric high-grade gliomas.

Neuro Oncol 2020 01;22(1):139-151

Children's Cancer Institute, University of New South Wales, Sydney, New South Wales, Australia.

Background: Despite increased understanding of the genetic events underlying pediatric high-grade gliomas (pHGGs), therapeutic progress is static, with poor understanding of nongenomic drivers. We therefore investigated the role of alterations in mitochondrial function and developed an effective combination therapy against pHGGs.

Methods: Mitochondrial DNA (mtDNA) copy number was measured in a cohort of 60 pHGGs. The implication of mtDNA alteration in pHGG tumorigenesis was studied and followed by an efficacy investigation using patient-derived cultures and orthotopic xenografts.

Results: Average mtDNA content was significantly lower in tumors versus normal brains. Decreasing mtDNA copy number in normal human astrocytes led to a markedly increased tumorigenicity in vivo. Depletion of mtDNA in pHGG cells promoted cell migration and invasion and therapeutic resistance. Shifting glucose metabolism from glycolysis to mitochondrial oxidation with the adenosine monophosphate-activated protein kinase activator AICAR (5-aminoimidazole-4-carboxamide ribonucleotide) or the pyruvate dehydrogenase kinase inhibitor dichloroacetate (DCA) significantly inhibited pHGG viability. Using DCA to shift glucose metabolism to mitochondrial oxidation and then metformin to simultaneously target mitochondrial function disrupted energy homeostasis of tumor cells, increasing DNA damage and apoptosis. The triple combination with radiation therapy, DCA and metformin led to a more potent therapeutic effect in vitro and in vivo.

Conclusions: Our results suggest metabolic alterations as an onco-requisite factor of pHGG tumorigenesis. Targeting reduced mtDNA quantity represents a promising therapeutic strategy for pHGG.
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http://dx.doi.org/10.1093/neuonc/noz140DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6954438PMC
January 2020

Integration of genomics, high throughput drug screening, and personalized xenograft models as a novel precision medicine paradigm for high risk pediatric cancer.

Cancer Biol Ther 2018 9;19(12):1078-1087. Epub 2018 Oct 9.

a Children's Cancer Institute, Lowy Cancer Research Centre , University of New South Wales , Randwick , New South Wales , Australia.

Pediatric high grade gliomas (HGG) are primary brain malignancies that result in significant morbidity and mortality. One of the challenges in their treatment is inter- and intra-tumoral heterogeneity. Precision medicine approaches have the potential to enhance diagnostic, prognostic and/or therapeutic information. In this case study we describe the molecular characterization of a pediatric HGG and the use of an integrated approach based on genomic, in vitro and in vivo testing to identify actionable targets and treatment options. Molecular analysis based on WGS performed on initial and recurrent tumor biopsies revealed mutations in TP53, TSC1 and CIC genes, focal amplification of MYCN, and copy number gains in SMO and c-MET. Transcriptomic analysis identified increased expression of MYCN, and genes involved in sonic hedgehog signaling proteins (SHH, SMO, GLI1, GLI2) and receptor tyrosine kinase pathways (PLK, AURKA, c-MET). HTS revealed no cytotoxic efficacy of SHH pathway inhibitors while sensitivity was observed to the mTOR inhibitor temsirolimus, the ALK inhibitor ceritinib, and the PLK1 inhibitor BI2536. Based on the integrated approach, temsirolimus, ceritinib, BI2536 and standard therapy temozolomide were selected for further in vivo evaluation. Using the PDX animal model (median survival 28 days) we showed significant in vivo activity for mTOR inhibition by temsirolimus and BI2536 (median survival 109 and 115.5 days respectively) while ceritinib and temozolomide had only a moderate effect (43 and 75.5 days median survival respectively). This case study demonstrates that an integrated approach based on genomic, in vitro and in vivo drug efficacy testing in a PDX model may be useful to guide the management of high risk pediatric brain tumor in a clinically meaningful timeframe.
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http://dx.doi.org/10.1080/15384047.2018.1491498DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6301829PMC
September 2019

Dual targeting of mitochondrial function and mTOR pathway as a therapeutic strategy for diffuse intrinsic pontine glioma.

Oncotarget 2018 Jan 8;9(7):7541-7556. Epub 2018 Jan 8.

Targeted Therapies Research Program, Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Sydney, New South Wales, Australia.

Diffuse Intrinsic Pontine Gliomas (DIPG) are the most devastating of all pediatric brain tumors. They mostly affect young children and, as there are no effective treatments, almost all patients with DIPG will die of their tumor within 12 months of diagnosis. A key feature of this devastating tumor is its intrinsic resistance to all clinically available therapies. It has been shown that glioma development is associated with metabolic reprogramming, redox state disruption and resistance to apoptotic pathways. The mitochondrion is an attractive target as a key organelle that facilitates these critical processes. PENAO is a novel anti-cancer compound that targets mitochondrial function by inhibiting adenine nucleotide translocase (ANT). Here we found that DIPG neurosphere cultures express high levels of ANT2 protein and are sensitive to the mitochondrial inhibitor PENAO through oxidative stress, while its apoptotic effects were found to be further enhanced upon co-treatment with mTOR inhibitor temsirolimus. This combination therapy was found to act through inhibition of PI3K/AKT/mTOR pathway, HSP90 and activation of AMPK. experiments employing an orthotopic model of DIPG showed a marginal anti-tumour effect likely due to poor penetration of the inhibitors into the brain. Further testing of this anti-DIPG strategy with compounds that penetrate the BBB is warranted.
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http://dx.doi.org/10.18632/oncotarget.24045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5800923PMC
January 2018

Combination of palbociclib and radiotherapy for glioblastoma.

Cell Death Discov 2017 3;3:17033. Epub 2017 Jul 3.

Cure Brain Cancer Foundation Biomarkers and Translational Research Group, Prince of Wales Clinical School, University of New South Wales Sydney, Sydney, NSW, Australia.

The cyclin-dependent kinase inhibitor, palbociclib has shown compelling efficacy in breast cancer patients. Several pre-clinical studies of glioblastoma (GBM) have also shown palbociclib to be efficacious. In this study, we investigated palbociclib in combination with radiation therapy (RT) for treating GBM. We tested palbociclib (with and without RT) on four patient-derived cell lines (PDCLs; RB1 retained; CDKN2A loss). We investigated the impact of therapy on the cell cycle and apoptosis using flow cytometry, . Balb/c nude mice were intracranially injected with the PDCL, GBM-L1 and treated orally with palbociclib (with and without RT). Overall survival was measured. Palbociclib treatment resulted in a significant increase in the percentage of cells in the G1 cell cycle phase. Apoptotic cell death, measured by Annexin V was induced. Palbociclib combined with RT acted synergistically with the significant impediment of colony formation. The oral treatment of mice with palbociclib did not show any significant survival advantage when compared to control mice, however when combined with RT, a survival advantage of 8 days was observed. Our results support the use of palbociclib as an adjuvant treatment to RT and warrant translation to the clinic.
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http://dx.doi.org/10.1038/cddiscovery.2017.33DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5494656PMC
July 2017

Veliparib in combination with radiotherapy for the treatment of MGMT unmethylated glioblastoma.

J Transl Med 2017 03 17;15(1):61. Epub 2017 Mar 17.

Cure Brain Cancer Biomarkers and Translational Research Group, Prince of Wales Clinical School, Adult Cancer Program, Lowy Cancer Research Centre, UNSW, Kensington, Australia.

Background: The O -methylguanine methyltransferase (MGMT) gene is frequently unmethylated in patients with glioblastoma (GBM), rendering them non-responsive to the standard treatment regime of surgery followed by concurrent radiotherapy (RT) and temozolomide. Here, we investigate the efficacy of adding a PARP inhibitor, veliparib, to radiotherapy to treat MGMT unmethylated GBM.

Methods: The inhibition of PARP with veliparib (ABT-888), a potent and orally bioavailable inhibitor in combination with RT was tested on a panel of patient derived cell lines (PDCLs) and patient-derived xenografts (PDX) models generated from GBM patients with MGMT unmethylated tumors.

Results: The combination of veliparib and RT inhibited colony formation in the majority of PDCLs tested. The PDCL, RN1 showed significantly reduced levels of the homologous repair protein, Mre11 and a heightened response to PARP inhibition measured by increased apoptosis and decreased colony formation. The oral administration of veliparib (12.5 mg/kg, twice daily for 5 days in a 28-day treatment cycle) in combination with whole brain RT (4 Gy) induced apoptosis (Tunel staining) and decreased cell proliferation (Ki67 staining) in a PDX of MGMT unmethylated GBM. Significantly longer survival times of the PDX treated with the combination treatment were recorded compared to RT only or veliparib only.

Conclusions: Our results demonstrate preclinical efficacy of targeting PARP at multiple levels and provide a new approach for the treatment of MGMT unmethylated GBM.
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http://dx.doi.org/10.1186/s12967-017-1164-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5356284PMC
March 2017

Identification of Circulating MicroRNA Signatures in Crohn's Disease Using the Nanostring nCounter Technology.

Inflamm Bowel Dis 2016 09;22(9):2063-9

*Center for Inflammatory Bowel Diseases, Division of Digestive Diseases, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California; †College of Arts and Science, School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom; and ‡Center for Systems Biomedicine, Division of Digestive Diseases, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California.

Background: Current clinical indices, such as Harvey-Bradshaw index, are often inadequate for the assessment of disease activity in Crohn's disease (CD). Alternative methods including imaging modalities and laboratory markers, such as C-reactive protein (CRP), are routinely applied to assess disease activity. However, laboratory markers poorly reflect the actual disease activity. Consequently, novel biomarkers represent a clinical necessity for CD patient management. We hypothesized that circulating serum-derived microRNAs may be used as diagnosis and disease activity monitoring tools of CD patients.

Methods: To test this hypothesis, we performed microRNA expression profiling through Nanostring nCounter technology in blood serum samples of CD patients and healthy control subjects. Harvey-Bradshaw index score was used to capture clinical disease activity; CRP was measured as part of standard clinical practice. The expression profile of circulating microRNAs and the levels of CRP correlated with Harvey-Bradshaw index.

Results: We identified a signature of 10 circulating microRNAs that are differentially expressed in CD patients compared with healthy control subjects. Two of these microRNAs (hsa-miR-1286 and hsa-miR-1273d) correlated with CD disease activity and exhibited higher correlation values compared with CRP. Further analysis revealed distinct microRNA signatures between CD patients with ileal and colonic involvement.

Conclusions: Circulating microRNAs show superior value as diagnostic and disease activity markers in comparison to traditional methods. Circulating microRNAs could improve CD patient management, if applied in combination with current state-of-the-art diagnostic and disease activity assessment modalities.
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http://dx.doi.org/10.1097/MIB.0000000000000883DOI Listing
September 2016

Antileukemic potency of CD19-specific T cells against chemoresistant pediatric acute lymphoblastic leukemia.

Exp Hematol 2015 Dec 16;43(12):1001-1014.e5. Epub 2015 Sep 16.

Cord & Marrow Transplant Facility, Kids Cancer Centre, Sydney Children's Hospital, Sydney, Australia; Faculty of Medicine, University of New South Wales, Sydney, Australia; Children's Cancer Institute Australia, Sydney, Australia.

Adoptive therapy with chimeric antigen receptor (CAR) T cells (CART cells) has exhibited great promise in clinical trials, with efficient response correlated with CART-cell expansion and persistence. Despite extensive clinical use, the mechanisms regulating CART-cell expansion and persistence have not been completely elucidated. We have examined the antileukemia potency of CART cells targeting CD19 antigen using second-generation CAR containing a CD28 co-stimulatory domain cloned into piggyBac-transposon vector and patient-derived chemoresistant pediatric acute lymphoblastic leukemia samples. In the presence of large numbers of target cells characteristic of patients with high leukemia burden, excessive proliferation of CART cells leads to differentiation into short-lived effector cells. Transient leukemia growth delay was induced by CART-cell infusion in mice xenografted with rapidly growing CD19+ acute lymphoblastic leukemia cells and was followed by rapid CART-cell extinction. Conditioning with the hypomethylating agent 5-aza-2'-deoxycytidine-activating caspase 3 and promotion of apoptosis in leukemia cells maximized the effect of CART cells and improved CART-cell persistence. These data suggest that the clinical use of 5-aza-2'-deoxycytidine before CART cells could be considered. Coculture of leukemia cells with bone marrow stroma cells reduced target cell loss, suggesting that leukemia cell mobilization into circulation may help to remove the protective effect of bone marrow stroma and increase the efficacy of CART-cell therapy.
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http://dx.doi.org/10.1016/j.exphem.2015.08.006DOI Listing
December 2015

Identification of Spinal Cord MicroRNA and Gene Signatures in a Model of Chronic Stress-Induced Visceral Hyperalgesia in Rat.

PLoS One 2015 29;10(7):e0130938. Epub 2015 Jul 29.

Oppenheimer Family Center for Neurobiology of Stress, Division of Digestive Diseases, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America.

Introduction: Animal studies have shown that stress could induce epigenetic and transcriptomic alterations essential in determining the balance between adaptive or maladaptive responses to stress. We tested the hypothesis that chronic stress in rats deregulates coding and non-coding gene expression in the spinal cord, which may underline neuroinflammation and nociceptive changes previously observed in this model.

Methods: Male Wistar rats were exposed to daily stress or handled, for 10 days. At day 11, lumbar spinal segments were collected and processed for mRNA/miRNA isolation followed by expression profiling using Agilent SurePrint Rat Exon and Rat miRNA Microarray platforms. Differentially expressed gene lists were generated using the dChip program. Microarrays were analyzed using the Ingenuity Pathways Analysis (IPA) tool from Ingenuity Systems. Multiple methods were used for the analysis of miRNA-mRNA functional modules. Quantitative real time RT-PCR for Interleukin 6 signal transducer (gp130), the Signal Transducer And Activator Of Transcription 3 (STAT3), glial fibrillary acidic protein and mir-17-5p were performed to confirm levels of expression.

Results: Gene network analysis revealed that stress deregulated different inflammatory (IL-6, JAK/STAT, TNF) and metabolic (PI3K/AKT) signaling pathways. MicroRNA array analysis revealed a signature of 39 deregulated microRNAs in stressed rats. MicroRNA-gene network analysis showed that microRNAs are regulators of two gene networks relevant to inflammatory processes. Specifically, our analysis of miRNA-mRNA functional modules identified miR-17-5p as an important regulator in our model. We verified miR-17-5p increased expression in stress using qPCR and in situ hybridization. In addition, we observed changes in the expression of gp130 and STAT3 (involved in intracellular signaling cascades in response to gp130 activation), both predicted targets for miR-17-5p. A modulatory role of spinal mir17-5p in the modulation of visceral sensitivity was confirmed in vivo.

Conclusion: Using an integrative high throughput approach, our findings suggest a link between miR-17-5p increased expression and gp130/STAT3 activation providing new insight into the possible mechanisms mediating the effect of chronic stress on neuroinflammation in the spinal cord.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0130938PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4519289PMC
April 2016

Alterations in the mitochondrial responses to PENAO as a mechanism of resistance in ovarian cancer cells.

Gynecol Oncol 2015 Aug 14;138(2):363-71. Epub 2015 Jun 14.

Tumour Metabolism Group, Adult Cancer Program, Lowy Cancer Research Centre and Prince of Wales Clinical School, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address:

Objective: The purpose of this study was to test PENAO, a promising new organoarsenical that is in phase 1 testing in patients with solid tumours, on a range of ovarian cancer cell lines with different histotypes, and to understand the molecular basis of drug resistance exhibited by the endometrioid ovarian cancer cell line, SKOV-3.

Methods: Proliferation arrest and cell death induced by PENAO in serous (OVCAR-3), endometrioid (SKOV-3, TOV112D), clear cell (TOV21G) and mucinous (EFO27) ovarian cancer cells in culture, and anti-tumour efficacy in a murine model of SKOV-3 and OVCAR-3 tumours, were measured. Cells were analysed for cell cycle arrest, cell death mechanisms, reactive oxygen species production, mitochondrial depolarisation, oxygen consumption and acid production.

Results: PENAO demonstrated promising anti-proliferative activity on the most common (serous, endometrioid) as well as on rare (clear cell, mucinous) subtypes of ovarian cancer cell lines. No cross-resistance with platinum-based drugs was evident. Endometrioid SKOV-3 cells were, however, shown to be resistant to PENAO in vitro and in a xenograft mouse model. This resistance was due to an ability to cope with PENAO-induced oxidative stress, notably through heme oxygenase-1 induction, and a shift in metabolism towards glycolysis. The adaptive glycolytic shift in SKOV-3 was targeted using a mTORC1 inhibitor in combination with PENAO. This strategy was successful with the two drugs acting synergistically to inhibit cell proliferation and to induce cell death via apoptosis and autophagy.

Conclusion: Mitochondria/mTOR dual-targeting therapy may constitute a new approach for the treatment of recurrent/resistant forms of epithelial ovarian cancer.
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http://dx.doi.org/10.1016/j.ygyno.2015.06.018DOI Listing
August 2015

Sensitization of Glioblastoma Cells to Irradiation by Modulating the Glucose Metabolism.

Mol Cancer Ther 2015 Aug 10;14(8):1794-804. Epub 2015 Jun 10.

Cure Brain Cancer Neuro-Oncology Group, Adult Cancer Program, Lowy Cancer Research Centre, Prince of Wales Clinical School, University of New South Wales, Sydney, New South Wales, Australia.

Because radiotherapy significantly increases median survival in patients with glioblastoma, the modulation of radiation resistance is of significant interest. High glycolytic states of tumor cells are known to correlate strongly with radioresistance; thus, the concept of metabolic targeting needs to be investigated in combination with radiotherapy. Metabolically, the elevated glycolysis in glioblastoma cells was observed postradiotherapy together with upregulated hypoxia-inducible factor (HIF)-1α and its target pyruvate dehydrogenase kinase 1 (PDK1). Dichloroacetate, a PDK inhibitor currently being used to treat lactic acidosis, can modify tumor metabolism by activating mitochondrial activity to force glycolytic tumor cells into oxidative phosphorylation. Dichloroacetate alone demonstrated modest antitumor effects in both in vitro and in vivo models of glioblastoma and has the ability to reverse the radiotherapy-induced glycolytic shift when given in combination. In vitro, an enhanced inhibition of clonogenicity of a panel of glioblastoma cells was observed when dichloroacetate was combined with radiotherapy. Further mechanistic investigation revealed that dichloroacetate sensitized glioblastoma cells to radiotherapy by inducing the cell-cycle arrest at the G2-M phase, reducing mitochondrial reserve capacity, and increasing the oxidative stress as well as DNA damage in glioblastoma cells together with radiotherapy. In vivo, the combinatorial treatment of dichloroacetate and radiotherapy improved the survival of orthotopic glioblastoma-bearing mice. In conclusion, this study provides the proof of concept that dichloroacetate can effectively sensitize glioblastoma cells to radiotherapy by modulating the metabolic state of tumor cells. These findings warrant further evaluation of the combination of dichloroacetate and radiotherapy in clinical trials.
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http://dx.doi.org/10.1158/1535-7163.MCT-15-0247DOI Listing
August 2015

Employing pancreatic tumor γ-glutamyltransferase for therapeutic delivery.

Mol Pharm 2014 May 2;11(5):1500-11. Epub 2014 Apr 2.

Lowy Cancer Research Centre and Prince of Wales Clinical School, University of New South Wales , Sydney, New South Wales 2052, Australia.

γ-Glutamyltransferase (γGT) is a cell surface enzyme that catalyzes hydrolysis of the bond linking the glutamate and cysteine residues of glutathione and glutathione-S-conjugates. We have observed that human pancreatic tumor cells and tumor-associated stellate cells express high levels of this enzyme when compared to normal pancreatic epithelial and stellate cells. Detection of the protein in tumor sections correlated with γGT activity on the surface of the cultured tumor and stellate cells. We tested whether the tumor γGT could be employed to deliver a therapeutic to the tumor endothelial cells. GSAO is a glutathione-S-conjugate of a trivalent arsenical that is activated to enter endothelial cells by γGT cleavage of the γ-glutamyl residue. The arsenical moiety triggers proliferation arrest and death of the endothelial cells by targeting the mitochondria. Human pancreatic tumor and stellate cell γGT activated GSAO in culture and γGT activity positively correlated with GSAO-mediated proliferation arrest and death of endothelial cells in Transwell and coculture systems. A soluble form of γGT is found in blood, and we measured the rate of activation of GSAO by this enzyme. We calculated that systemically administered GSAO would circulate through the pancreatic blood supply several times before appreciable activation by normal blood levels of γGT. In support of this finding, tumor γGT activity positively correlated with GSAO-mediated inhibition of pancreatic tumor angiogenesis and tumor growth in mice. Our findings indicate that pancreatic tumor γGT can be used to deliver a therapeutic to the tumor.
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http://dx.doi.org/10.1021/mp400664tDOI Listing
May 2014

Purine Nucleoside Phosphorylase mediated molecular chemotherapy and conventional chemotherapy: a tangible union against chemoresistant cancer.

BMC Cancer 2011 Aug 24;11:368. Epub 2011 Aug 24.

Oncology Research Centre, Prince of Wales Hospital, Randwick, Sydney, NSW, 2031, Australia.

Background: Late stage Ovarian Cancer is essentially incurable primarily due to late diagnosis and its inherent heterogeneity. Single agent treatments are inadequate and generally lead to severe side effects at therapeutic doses. It is crucial to develop clinically relevant novel combination regimens involving synergistic modalities that target a wider repertoire of cells and lead to lowered individual doses. Stemming from this premise, this is the first report of two- and three-way synergies between Adenovirus-mediated Purine Nucleoside Phosphorylase based gene directed enzyme prodrug therapy (PNP-GDEPT), docetaxel and/or carboplatin in multidrug-resistant ovarian cancer cells.

Methods: The effects of PNP-GDEPT on different cellular processes were determined using Shotgun Proteomics analyses. The in vitro cell growth inhibition in differentially treated drug resistant human ovarian cancer cell lines was established using a cell-viability assay. The extent of synergy, additivity, or antagonism between treatments was evaluated using CalcuSyn statistical analyses. The involvement of apoptosis and implicated proteins in effects of different treatments was established using flow cytometry based detection of M30 (an early marker of apoptosis), cell cycle analyses and finally western blot based analyses.

Results: Efficacy of the trimodal treatment was significantly greater than that achieved with bimodal- or individual treatments with potential for 10-50 fold dose reduction compared to that required for individual treatments. Of note was the marked enhancement in apoptosis that specifically accompanied the combinations that included PNP-GDEPT and accordingly correlated with a shift in the expression of anti- and pro-apoptotic proteins. PNP-GDEPT mediated enhancement of apoptosis was reinforced by cell cycle analyses. Proteomic analyses of PNP-GDEPT treated cells indicated a dowregulation of proteins involved in oncogenesis or cancer drug resistance in treated cells with accompanying upregulation of apoptotic- and tumour- suppressor proteins.

Conclusion: Inclusion of PNP-GDEPT in regular chemotherapy regimens can lead to significant enhancement of the cancer cell susceptibility to the combined treatment. Overall, these data will underpin the development of regimens that can benefit patients with late stage ovarian cancer leading to significantly improved efficacy and increased quality of life.
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http://dx.doi.org/10.1186/1471-2407-11-368DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3185280PMC
August 2011

Molecular chemotherapy and chemotherapy: a new front against late-stage hormone-refractory prostate cancer.

Clin Cancer Res 2011 Jun 29;17(12):4006-18. Epub 2011 Apr 29.

Oncology Research Centre, Prince of Wales Hospital, Randwick, Sydney, New South Wales 2031, Australia.

Purpose: Stemming from its inherent heterogeneity, single-agent treatments are essentially ineffective against castration-resistant prostate cancer (CRPC). Thus, clinically relevant regimens that harness different modalities to maximize treatment efficacy without increasing cumulative toxicities are urgently needed. Based on this rationale, we investigated whether a novel combination of purine nucleoside phosphorylase-mediated, gene-directed enzyme-prodrug therapy (PNP-GDEPT) with docetaxel against CRPC has superior efficacy in comparison with individual treatments.

Methods: The in vitro cell growth inhibition in differentially treated murine and human CRPC cell lines was established using a cell-viability assay. The extent of synergy, additivity, or antagonism between treatments was evaluated using CalcuSyn statistical analyses. The local and systemic effects of docetaxel and/or PNP-GDEPT were tested in both immunodeficient and immunocompetent mice against human and murine CRPC tumors, respectively. Subsequently, immunohistochemical analyses and an evaluation of serum cytokine and serum toxicity profiles were conducted to characterize the differential host responses to treatment.

Results: The combined use of PNP-GDEPT and docetaxel led to strong synergistic cell killing in vitro. Compared with the individual modalities, a combination of the 2 led to a marked reduction in "local and distant" tumor growth in vivo, and importantly, with lowered doses and without additional toxicities. Immunomodulation was indicated by enhanced immune cell infiltration and altered serum cytokine levels. Furthermore, a lowering of T-helper type 2 cytokines, MCP-1, interleukin (IL)-4, IL-6, and IL-10 marked lower tumor burden and enhanced treatment efficacy.

Conclusion: PNP-GDEPT and docetaxel are a potent combination against CRPC in immunocompetent and immunodeficient settings; these outcomes have implications of translational potential for improved treatment and management of CRPC patients.
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http://dx.doi.org/10.1158/1078-0432.CCR-11-0248DOI Listing
June 2011

Anatomical Parts-Based Regression Using Non-Negative Matrix Factorization.

Conf Comput Vis Pattern Recognit Workshops 2010 :2863-2870

Department Psychology, University of New Mexico.

Non-negative matrix factorization (NMF) is an excellent tool for unsupervised parts-based learning, but proves to be ineffective when parts of a whole follow a specific pattern. Analyzing such local changes is particularly important when studying anatomical transformations. We propose a supervised method that incorporates a regression constraint into the NMF framework and learns maximally changing parts in the basis images, called Regression based NMF (RNMF). The algorithm is made robust against outliers by learning the distribution of the input manifold space, where the data resides. One of our main goals is to achieve good region localization. By incorporating a gradient smoothing and independence constraint into the factorized bases, contiguous local regions are captured. We apply our technique to a synthetic dataset and structural MRI brain images of subjects with varying ages. RNMF finds the localized regions which are expected to be highly changing over age to be manifested in its significant basis and it also achieves the best performance compared to other statistical regression and dimensionality reduction techniques.
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http://dx.doi.org/10.1109/CVPR.2010.5540022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4059066PMC
January 2010

Pancreatic stellate cells: partners in crime with pancreatic cancer cells.

Cancer Res 2008 Apr;68(7):2085-93

Pancreatic Research Group, South Western Sydney Clinical School, The University of New South Wales, Sydney, New South Wales 2052, Australia.

Pancreatic stellate cells (PSC) produce the stromal reaction in pancreatic cancer, but their role in cancer progression is not fully elucidated. We examined the influence of PSCs on pancreatic cancer growth using (a) an orthotopic model of pancreatic cancer and (b) cultured human PSCs (hPSC) and human pancreatic cancer cell lines MiaPaCa-2 and Panc-1. Athymic mice received an intrapancreatic injection of saline, hPSCs, MiaPaCa-2 cells, or hPSCs + MiaPaCa-2. After 7 weeks, tumor size, metastases, and tumor histology were assessed. In vitro studies assessed the effect of cancer cell secretions on PSC migration and the effect of hPSC secretions on cancer cell proliferation, apoptosis, and migration. Possible mediators of the effects of hPSC secretions on cancer cell proliferation were examined using neutralizing antibodies. Compared with mice receiving MiaPaCa-2 cells alone, mice injected with hPSCs + MiaPaCa-2 exhibited (a) increased tumor size and regional and distant metastasis, (b) fibrotic bands (desmoplasia) containing activated PSCs within tumors, and (c) increased tumor cell numbers. In vitro studies showed that, in the presence of pancreatic cancer cells, PSC migration was significantly increased. Furthermore, hPSC secretions induced the proliferation and migration, but inhibited the apoptosis, of MiaPaCa-2 and Panc-1 cells. The proliferative effect of hPSC secretions on pancreatic cancer cells was inhibited in the presence of neutralizing antibody to platelet-derived growth factor. Our studies indicate a significant interaction between pancreatic cancer cells and stromal cells (PSCs) and imply that pancreatic cancer cells recruit stromal cells to establish an environment that promotes cancer progression.
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http://dx.doi.org/10.1158/0008-5472.CAN-07-2477DOI Listing
April 2008