Perturbations of the complex intrinsic and extrinsic factors that contribute to cellular differentiation can have many consequences ranging from dedifferentiation to cell death. The overall objective of my research is to investigate the factors that contribute to the maintenance of mature midbrain neurons and glia. In order to address this objective, I first carried out a detailed immunocytochemical analysis to demonstrate that histone deacetylase inhibitor (HDACI) treatment of differentiated midbrain neurons in culture results in an overall destabilization of neuronal phenotype, which leads to caspase-independent cell death. GFAP positive astrocytes are refractory to the effects of HDACI treatment, suggesting that inhibition of HDACs has differential effects on neurons and glia. HDACI treatment alone was not sufficient to induce neuronal dedifferentiation as evidenced by RT-PCR analysis of stem/progenitor markers, and recovery experiments. Finally, I demonstrate that cortical neurons do not undergo cell death in response to HDACI treatment, suggesting that there may be microenvironmental factors that promote the susceptibility of midbrain neurons to the neurotoxic effects of HDACI. In the second part of this thesis I determined the molecular mechanism that was at least partly responsible for the effects of HDACI treatment on midbrain neurons. Gene expression profiling of HDACI treated midbrain cultures revealed a strong down-regulation of immune related factors. This observation is supported by the loss of microglia in HDACI treated midbrain cultures. I also provide evidence that Toll-like receptor (TLR) signaling, likely through the activation of Interleukin-6 (IL-6) expression, mediates HDAC-dependent neuronal survival. These data provide new evidence that the neuroimmune system is an extrinsic regulator for the homeostasis and survival of neurons.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

Burkitt lymphoma (BL) was the first tumor found to be strongly associated with Epstein-Barr virus (EBV). Almost 100% of the lymphoma cells are cycling, necessitating dose- and time-intense multi-agent chemotherapy regimens to achieve a cure of the disease. Whilst standard risk BL can be cured with this approach, high risk BL with leukaemic and CNS disease has significantly inferior survival. The intensive chemotherapy regimen causes considerable toxicity to the patients and relapse of BL is largely incurable. Thus, novel therapeutic approaches for high risk and relapsed BL are needed. Histone deacetylase inhibitors (HDACis) represent a novel class of drugs with potent anti-cancer effect in a wide range of malignancies. In the first part of this study, we tested HDACis of different classes for their ability to inhibit cell proliferation and activate the lytic cycle of EBV in a panel of EBV-positive BL cells of different latent viral gene expression patterns (type I, Wp-restricted and type III latency with highly restrictive, partial and full spectrum of EBV latent gene expression, respectively). Different HDACis could inhibit proliferation of EBV-positive BL cells in a time- and dose-dependent manner but only weakly activate the viral lytic cycle indicating that the drugs’ cytotoxic effect is independent of the EBV lytic cycle. Of note, BL cells of Wp-restricted or type III latency were more resistant to killing by HDACis than those of latency I, suggesting a possible link between relative resistance to the drug and expression of the latent viral genes. Bortezomib, a proteasome inhibitor, may have synergistic action with HDACis on lymphoid malignancies. We hypothesized that Bortezomib could potentiate the killing of EBV-positive BL cells by HDACis. In the second part, we tested the effect of combination of a FDA-approved HDACi, suberoylanilide hydroxamic acid (SAHA) and Bortezomib in the same panel of BL cells and also EBV-transformed lymphoblastoid cell lines (LCLs) which represent an in-vitro model of EBV-associated post-transplant lymphoproliferative disorder (PTLD). Interestingly, combination of SAHA and Bortezomib significantly enhanced the killing of BL cells of Wp-restricted or type III latency. Furthermore, the resistance to either SAHA or Bortezomib alone in contrast to synergistic killing by the combination of the two drugs could be observed in LCLs which also have the type III latency pattern. Compared with either drug alone, combination of SAHA and Bortezomib induced enhanced apoptosis in Wp-restricetd BL cells and LCLs as shown by the increase in the percentage of annexin V-positive cell, sub-G1 population and the proteolytic cleavage of apoptotic markers including PARP, caspase-3 and -9. The drug combination hyper-acetylated histone and induced cell cycle arrest. Combination of SAHA and Bortezomib was further shown to suppress the growth of BL xenograft in nude mice. In conclusion, our data indicated that expression of partial or full spectrum of viral latent genes in EBV-positive BL cells of Wp-restricted or type III latency confers resistance of the tumor cells to cytotoxic effect of HDACis. Bortezomib could potentiate SAHA-induced apoptosis of both BL cells and LCLs and might overcome mechanism of drug resistance. / published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Philosophy

Today, cancer is understood as an epigenetic as well as a genetic disease. The main epigenetic hallmarks of the cancer cell are DNA methylation and histone modifications. The latter changes may be an optimal target for novel anticancer agents. The main goal of using histone deacetylase inhibitors (HDACIs) would be restoration of gene expression of those tumor-suppressor genes that have been transcriptionally silenced by promoter-associated histone deacetylation. However, HDACIs have pleiotropic effects that we are only just starting to understand. These may also be responsible for the induction of differentiation, cell-cycle arrest and pro-apoptotic effects. There are now so many HDACIs available, with such different chemical structures and biological and biochemical properties, that it is hopeful that at least some of them will succeed, probably in combination with other agents or therapies. In our studies we focussed ourselves on studies some new HDACIs, that can be useful for treating cancers, including leukemia and epithelial cancer. To do that, we used novel HDACIs, like BML-210, and their combination with the differentiation inducer all-trans retinoic acid (ATRA). Cell differentiation and proliferation in general, and specific gene expression require de novo protein synthesis and/or post-translational protein modifications. So, we tried to identify proteins in general and specifically the proteins that could be important for the cell differentiation process, and when and where in the cell the proteins appear. We delineated that HDACIs inhibited leukemia (NB4 and HL-60) cell growth in a time- and dose-dependent way. Moreover, BML-210 blocked HeLa cell growth and promoted apoptosis in a time-dependent way. Combining of BML-210 with ATRA induced a differentiation process in leukemia cell lines that lead to apoptosis. This correlated with cell cycle arrest in G0/G1 stage and changes in expression of cell cycle proteins (p21, p53), transcription factors (NF-κB, Sp1) and their binding activity to consensus or specific promoter sequences. We also assessed histone modifications, i.e. H3 phosphorylation and H4 hyperacetylation due to HDACI, leading to chromatin remodeling and changes in gene transcriptions. We have also studied changes in protein maps caused by HDACIs and differentiation agents, identifying differences for a few proteins due to growth inhibition and induction of differentiation in NB4 cells using BML-210 alone or in combination with ATRA. These proteins are involved in cell proliferation and signal transduction, like Rab, actin and calpain. One of them was alpha-dystrobrevin (α-DB). To further study possible roles of the latter, we determined changes of α-DB protein isoform expression that correlated with induction of differentiation. We thus identified a novel ensemble of α-DB interacting proteins in promyelocytic leukemia cells, including tropomyosin 3, actin, tubulin, RIBA, STAT and others, being important in cytoskeleton reorganization and signal transduction. Using confocal microscopy, we determined that α-DB co-localizes with HSP90 and F-actin in NB4 and HeLa cells. We also revealed that it changes sub-cellular compartment after treatment with ATRA and/or BML-210. α-DB silencing affected F-actin expression in HeLa cells, further supporting the idea that α-DB is involved in cytoskeleton reorganization in cells. Altogether, our results suggest that α−DB may work as a structural protein during proliferation and differentiation processes of human cancer cells. Based on our findings, we suggest that HDACIs, like BML-210, can be promising anticancer agents, especially in leukemia treatment, by inducing apoptosis and regulating proliferation and differentiation through the modulation of histone acetylations and gene expression.

Cancer is the second leading cause of death in the United States (more than half a million people each year), and even with billions of dollars in medical effort patients are rarely cured. This dissertation research is devoted to meeting this medical need by providing new cancer therapeutics that are more potent and safer than current chemotherapies. This is achieved by using two state of the art anticancer “warheads”: 1) gold nanoparticle (AuNP) technology and 2) a new class of epigenetic anticancer small molecules, histone deacetylase inhibitors (HDACi). These warheads are then selectively delivered to cancer cells via “homing devices” targeted to receptors that are overexpressed in the cancers. This work primarily focuses on the androgen receptor (AR) to target prostate cancer. The 1st chapter sets the stage, providing scientific rationale and background for the central hypothesis: small molecules that engage the AR can, upon conjugation to a therapeutic agent, enable selective delivery of that agent to prostate cancer cells. Chapter 2 delves into the structural molecular biology of the androgen receptor. There is a survey of the crystallographic data for all nuclear receptors, providing structural information which is used to build AR homology models for antagonist and inverse agonist modes of ligand binding. These models are used to design AR targeting ligands (Chapters 3, 5, 6 and 7). The application of the targeting technology is illustrated by attaching them to AuNPs for selective delivery to prostate cancer cells (Chapter 3). Next, in order to appreciate the importance of using targeting agents in HDACi cancer therapeutics, we reviewed this recently emerged field in Chapter 4. In this chapter we argue that the failure of HDACi in solid tumors, despite more than 500 clinical trials in the last decade, is primarily due to an inability of these small molecules to accumulate at effective concentrations in the cancer. We provide an analysis of the paradigms being pursued to overcome this barrier, including HDAC isoform selectivity, localized administration, and targeting cap groups to achieve selective tissue and cell type distribution. In Chapter 5, this last approach (targeting cap groups, or a “homing device”) is illustrated with HDACi targeted to prostate cancer via antiandrogens that bind the AR. The second generation of improved “homing devices” is disclosed in Chapter 6 (for both AuNPs and HDACi), in addition to preliminary ADMET data and safety studies in mice. Excitingly, our three dimensional understanding of binding to the AR allowed design and structure-activity-relationship studies that lead to the first reported examples of AR inverse agonists (Chapter 7) Several points of significance: • AuNP targeted to AR ∙ have the strongest binding affinity ever reported (IC50 ~14 picomolar) ∙ are actively recruited to prostate cancer cells ∙ overcome treatment resistance in advanced prostate cancer cells ∙ exhibit nanomolar anticancer potency ∙ resolved the identity of the “membrane AR” as the GPRC6A • HDACi targeted to AR ∙ have HDACi activity and AR binding affinity superior to their clinical precursors ∙ exhibit potent AR antagonist activity ∙ induce AR translocation to the nucleus in a HDACi dependent fashion ∙ selectively and potently kill prostate cancer cells that express AR ∙ are safer than Tylenol®, as tested in small animals • Pure AR binding ligand studies ∙ resulted in the discovery of the first examples of AR inverse agonists, which are vastly more potent that clinically available antiandrogens for prostate cancer ∙ work via a never-before-seen mechanism of action, by localizing to the nucleus and recruiting corepressors to actively shut off AR genes

Thesis (Ph.D.). / Written for the Dept. of Pharmacology & Therapeutics. Title from title page of PDF (viewed 2009/06/10). Includes bibliographical references.

The enhanced expression of histone deacetylases (HDACs) in a variety of malignancies drew attention to investigate a new category of anti-cancer drugs that are based on the inhibition of those enzymes. Valproic acid (VPA) is a well-known antiepileptic drug that exhibits antitumor activities through inhibition of HDACs class I and IIa. Cancer stem cells (CSCs) have been recognized to drive the tumor growth and progression hence; attention has been given to target this small subpopulation of CSCs rather than the whole bulk tumor cells. CD133 is considered to be a CSC marker in several tumors and its transcription is strongly influenced by epigenetic changes that will be altered upon administration of histone deacetylase inhibitors (HDACi) in cancer treatment. Therefore, we evaluated the epigenetic and cytotoxic effects of treatment with 1 mM VPA in combination with other chemotherapeutics and its influence on the expression of CD133 in human neuroblastoma (NB) cell lines. Our results revealed that addition of VPA to DNA-damaging chemotherapeutics induced a synergistic anti-tumor effect that was associated with caspase-3 dependent induction of apoptosis in UKF-NB-4 cells. This synergism was related to the increase of the acetylation status of histones H3 and H4 and was only produced either by...

Neuroblastoma is the most common extracranial solid tumor that occurs during infancy. Despite the great progress has been made in contemporary clinic medicine some forms of neuroblastoma disease are still found very difficult to treat . This work focuses on the effects of histone deacetylase inhibitors (HDAC) in the neuroblastoma cell lines. It is known that HDAC inhibitors may contribute to recurrence of the tumor cells by affecting the chromatin structure and thus increase the expression of critical tumor suppressor genes. These genes activate apoptotic pathways that may even be independent of caspases. We observed the efficiency of used HDAC inhibitors as under standard conditions an in hypoxia (1 % O2). Inadequate amount of oxygen supply is one of the characteristic features of tumors and it also may contribute to chemoresistance. With the hypoxia-induced chemoresistance of tumor cells, the influence of HIF-1α is expected. Some HDAC inhibitors reduce the amount of HIF-1α in hypoxia and thus HIF transcription factor activity. Thus, the first part of this study is concerned with the acquisition of suitable experimental arrangement for the monitoring of induction of cellular death in human neuroblastoma cell lines SK-N-AS and UKF-NB-3. Secondly, this paper provides the evaluation of the influence...

Vitamin D plays an important role in preserving healthy bones, and has additional roles in the body, including modulation of cell growth, differentiation, neuromuscular and immune function, and anti-inflammatory function. The vitamin D receptor (VDR) is a member of the nuclear hormone receptor superfamily and regulates transcription of vitamin D-dependent target genes, such as those for key proteins involved in calcium and phosphorus absorption and bone development. Histone acetylation weakens the association of histones with DNA, and increases the accessibility of transcriptional regulatory proteins to chromatin templates, thereby increasing transcriptional activity of gene expression. Histone deacetylases remove the acetyl groups and condense chromatin structure, thereby preventing transcription. TSA is a potent histone deacetylase inhibitor and can significantly enhance gene expression. Bioactive food component, sulforaphane (SFN) is found in cruciferous vegetables and is known to be a histone deacetylase inhibitor, leading to transcriptional activation of gene expression. The objective of this study is to demonstrate that the bioactive food components modulate vitamin D action in adipocytes. To investigate the effects of TSA and SFN on vitamin D response, 3T3L1 mouse preadipocytes were treated with the combination of various concentrations of 1,25(OH)2 vitamin D, TSA, and SFN. Upon harvesting cells, the amounts of 24-hydroxylase mRNA, marker of vitamin D response, were measured by semiquantitative reverse transcriptase-PCR analysis. The results showed that the cells treated with 1μM TSA increased 1,25(OH)2 vitamin D-induced CYP24 mRNA level nearly 3.5-fold (p < 0.05) at 1nM 1,25(OH)2 vitamin D and nearly 2.5-fold (p < 0.05) in 10 nM 1,25(OH)2 vitamin D, and the cells treated with 5μM SFN increased 1,25(OH)2 vitamin D-induced CYP24 mRNA level nearly 1.4-fold at 1nM 1,25(OH)2 vitamin D and nearly 1.2-fold at 10 nM 1,25(OH)2 vitamin D.

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