Histone deacetylase inhibitor ITF2357 (givinostat) reverts transformed phenotype and counteracts stemness in in vitro and in vivo models of human glioblastoma

Calotropis procera: A double edged sword against glioblastoma, inhibiting glioblastoma cell line growth by targeting histone deacetylases (HDAC) and angiogenesis

Despite substantial investments in anti-glioblastoma (GBM) drug discovery over the last decade, progress is limited to preclinical stages, with clinical studies frequently encountering obstacles. Angiogenic and histone deacetylase inhibitors (HDACi) have shown profound results in pre-clinical studies. Investigating a multicomponent anti-cancer remedy that disrupts the tumor angiogenic blood vessels and simultaneously disrupts HDACs, while inducing minimal side effects, is critically needed. The crude extracts derived from medicinal plants serve as a renewable reservoir of anti-tumor drugs, exhibiting reduced toxicity compared to chemically synthesized formulations. Calotropis procera is a traditional medicinal plant, and its anticancer potential against many cancer cell lines has been reported, however its antiangiogenic and HDAC inhibitory action is largely unknown. The anticancer activity of methanol leaf extract of C. procera was tested in three types of human glioblastoma cell lines. Wild-type and transgenic zebrafish embryos were used to evaluate developmental toxicity and angiogenic activity. A human angiogenic antibody array was used to profile angiogenic proteins in the U251 GM cell line. A real-time reverse transcriptase polymerase chain reaction (RT PCR) assay was used to detect the differential expression of eleven HDAC genes in U251 cells treated with C. procera extract. The extract significantly reduced the proliferation of all three types of GBM cell lines and the cytotoxicity was found to be more pronounced in U251 GM cells, with an IC50 value of 2.63 ± 0.23 μg/ml, possibly by arresting the cell cycle at the G2/M transition. The extract did not exhibit toxic effects in zebrafish embryos, even at concentrations as high as 1000 μg/ml. The extract also inhibited angiogenic blood vessel formation in the transgenic zebrafish model in a dose-dependent manner. The results from the angiogenic antibody array have suggested novel angiogenesis targets that can be utilized to treat GBM. Real-time RT PCR analysis has shown that C. procrea extract caused an upregulation of HDAC5, 7, and 10, while the mRNA of HDAC1, 2, 3 and 8 (Class I HDACs), and HDAC4, 6, and 9 (Class II) were downregulated in U251 GM cells. The cytotoxicity of the C. procera extract on GBM cell lines could be due to its dual action by regulation of both tumor angiogenesis and histone deacetylases enzymes. Through this study, the C. procera leaf extract has been suggested as an effective remedy to treat GBM with minimal toxicity. In addition, various novel angiogenic and HDAC targets has been identified which could be helpful in designing better therapeutic strategies to manage glioblastoma multiforme in human patients.

Double-strand DNA break repair: molecular mechanisms and therapeutic targets

Double-strand break (DSB), a significant DNA damage brought on by ionizing radiation, acts as an initiating signal in tumor radiotherapy, causing cancer cells death. The two primary pathways for DNA DSB repair in mammalian cells are nonhomologous end joining (NHEJ) and homologous recombination (HR), which cooperate and compete with one another to achieve effective repair. The DSB repair mechanism depends on numerous regulatory variables. DSB recognition and the recruitment of DNA repair components, for instance, depend on the MRE11-RAD50-NBS1 (MRN) complex and the Ku70/80 heterodimer/DNA-PKcs (DNA-PK) complex, whose control is crucial in determining the DSB repair pathway choice and efficiency of HR and NHEJ. In-depth elucidation on the DSB repair pathway's molecular mechanisms has greatly facilitated for creation of repair proteins or pathways-specific inhibitors to advance precise cancer therapy and boost the effectiveness of cancer radiotherapy. The architectures, roles, molecular processes, and inhibitors of significant target proteins in the DSB repair pathways are reviewed in this article. The strategy and application in cancer therapy are also discussed based on the advancement of inhibitors targeted DSB damage response and repair proteins.

Oncogenic BRAF and p53 Interplay in Melanoma Cells and the Effects of the HDAC Inhibitor ITF2357 (Givinostat)

Oncogenic BRAF mutations have been widely described in melanomas and promote tumour progression and chemoresistance. We previously provided evidence that the HDAC inhibitor ITF2357 (Givinostat) targets oncogenic BRAF in SK-MEL-28 and A375 melanoma cells. Here, we show that oncogenic BRAF localises to the nucleus of these cells, and the compound decreases BRAF levels in both the nuclear and cytosolic compartments. Although mutations in the tumour suppressor p53 gene are not equally frequent in melanomas compared to BRAF, the functional impairment of the p53 pathway may also contribute to melanoma development and aggressiveness. To understand whether oncogenic BRAF and p53 may cooperate, a possible interplay was considered in the two cell lines displaying a different p53 status, being p53 mutated into an oncogenic form in SK-MEL-28 and wild-type in A375 cells. Immunoprecipitation revealed that BRAF seems to preferentially interact with oncogenic p53. Interestingly, ITF2357 not only reduced BRAF levels but also oncogenic p53 levels in SK-MEL-28 cells. ITF2357 also targeted BRAF in A375 cells but not wild-type p53, which increased, most likely favouring apoptosis. Silencing experiments confirmed that the response to ITF2357 in BRAF-mutated cells depends on p53 status, thus providing a rationale for melanoma-targeted therapy.

Inhibition of histone deacetylases attenuates tumor progression and improves immunotherapy in breast cancer

Breast cancer is one of the common malignancies with poor prognosis worldwide. The treatment of breast cancer patients includes surgery, radiation, hormone therapy, chemotherapy, targeted drug therapy and immunotherapy. In recent years, immunotherapy has potentiated the survival of certain breast cancer patients; however, primary resistance or acquired resistance attenuate the therapeutic outcomes. Histone acetyltransferases induce histone acetylation on lysine residues, which can be reversed by histone deacetylases (HDACs). Dysregulation of HDACs via mutation and abnormal expression contributes to tumorigenesis and tumor progression. Numerous HDAC inhibitors have been developed and exhibited the potent anti-tumor activity in a variety of cancers, including breast cancer. HDAC inhibitors ameliorated immunotherapeutic efficacy in cancer patients. In this review, we discuss the anti-tumor activity of HDAC inhibitors in breast cancer, including dacinostat, belinostat, abexinostat, mocetinotat, panobinostat, romidepsin, entinostat, vorinostat, pracinostat, tubastatin A, trichostatin A, and tucidinostat. Moreover, we uncover the mechanisms of HDAC inhibitors in improving immunotherapy in breast cancer. Furthermore, we highlight that HDAC inhibitors might be potent agents to potentiate immunotherapy in breast cancer.

The botanical drug PBI-05204, a supercritical CO2 extract of Nerium oleander, sensitizes alveolar and embryonal rhabdomyosarcoma to radiotherapy in vitro and in vivo

Treatment of rhabdomyosarcoma (RMS), the most common a soft tissue sarcoma in childhood, provides intensive multimodal therapy, with radiotherapy (RT) playing a critical role for local tumor control. However, since RMS efficiently activates mechanisms of resistance to therapies, despite improvements, the prognosis remains still largely unsatisfactory, mainly in RMS expressing chimeric oncoproteins PAX3/PAX7-FOXO1, and fusion-positive (FP)-RMS. Cardiac glycosides (CGs), plant-derived steroid-like compounds with a selective inhibitory activity of the Na+/K+-ATPase pump (NKA), have shown antitumor and radio-sensitizing properties. Herein, the therapeutic properties of PBI-05204, an extract from Nerium oleander containing the CG oleandrin already studied in phase I and II clinical trials for cancer patients, were investigated, in vitro and in vivo, against FN- and FP-RMS cancer models. PBI-05204 induced growth arrest in a concentration dependent manner, with FP-RMS being more sensitive than FN-RMS, by differently regulating cell cycle regulators and commonly upregulating cell cycle inhibitors p21Waf1/Cip1 and p27Cip1/Kip1. Furthermore, PBI-05204 concomitantly induced cell death on both RMS types and senescence in FN-RMS. Notably, PBI-05204 counteracted in vitro migration and invasion abilities and suppressed the formation of spheroids enriched in CD133+ cancer stem cells (CSCs). PBI-05204 sensitized both cell types to RT by improving the ability of RT to induce G2 growth arrest and counteracting the RT-induced activation of both Non‐Homologous End‐Joining and homologous recombination DSBs repair pathways. Finally, the antitumor and radio-sensitizing proprieties of PBI-05204 were confirmed in vivo. Notably, both in vitro and in vivo evidence confirmed the higher sensitivity to PBI-05204 of FP-RMS. Thus, PBI-05204 represents a valid radio-sensitizing agent for the treatment of RMS, including the intrinsically radio-resistant FP-RMS.

ITF2357 induces cell cycle arrest and apoptosis of meningioma cells via the PI3K-Akt pathway

As a type of central nervous system tumor, meningioma usually compresses the nerve center due to its local expansion, further causing neurological deficits. However, there are limited therapeutic approaches for meningiomas. ITF2357, a potent class I and II histone deacetylase inhibitor (HDACi), has been shown to inhibit cell proliferation, promote apoptosis, and block the cell cycle in various sarcoma cells, including glioblastoma and peripheral T-cell lymphoma. Here, we investigated the potential role of ITF2357 on meningioma cancer cells (IOMM-Lee cells). First, we demonstrated that the half-maximal inhibitory concentration (IC50) of ITF2357 was 1.842 μM by MTT assay. In addition, ITF2357 effectively inhibited the proliferation and colonization ability of IOMM-Lee cells. Flow cytometry analysis showed that ITF2357 induced G0/G1 and G2/M phase cell cycle arrest and cell apoptosis. Mechanically, the RNA sequencing data revealed that ITF2357 could affect the PI3K-Akt signaling pathway and the cell cycle progression. Furthermore, the expression levels of Akt, PI3K, p-Akt, and p-PI3K were determined by western blotting. Collectively, our data revealed that ITF2357 induces G0 G1 and G2/M phase arrest and apoptosis by inhibiting hyperactivation of the PI3K-Akt pathway, ultimately inhibiting cell viability and proliferation of meningioma cells, which developed a new approach to the treatment of meningioma.

The Histone Deacetylase Inhibitor ITF2357 (Givinostat) Targets Oncogenic BRAF in Melanoma Cells and Promotes a Switch from Pro-Survival Autophagy to Apoptosis

Histone deacetylase inhibitors (HDACI) are epigenetic compounds that have been widely considered very promising antitumor agents. Here, we focus on the effects of the pan-HDAC inhibitor ITF2357 (Givinostat) in comparison with SAHA (Vorinostat) in melanoma cells bearing BRAF V600E oncogenic mutation. Our results indicate both ITF2357 and SAHA dose-dependently reduce the viability of BRAF-mutated SK-MEL-28 and A375 melanoma cells. The comparison of IC50 values revealed that ITF2357 was much more effective than SAHA. Interestingly, both inhibitors markedly decreased oncogenic BRAF protein expression levels, ITF2357 being the most effective compound. Moreover, the BRAF decrease induced by ITF2357 was accompanied by a decrease in the level of phospho-ERK1/2. The inhibitor of upstream MEK activity, U0126, reduced ERK1/2 phosphorylation and dramatically potentiated the antitumor effect of ITF2357, exacerbating the reduction in the BRAF level. ITF2357 stimulated an early pro-survival autophagic response, which was followed by apoptosis, as indicated by apoptotic markers evaluation and the protective effects exerted by the pan-caspase inhibitor z-VADfmk. Overall, our data indicate for the first time that ITF2357 targets oncogenic BRAF in melanoma cells and induces a switch from autophagy to classic apoptosis, thus representing a possible candidate in melanoma targeted therapy.

Differential molecular mechanistic behavior of HDACs in cancer progression

Genetic aberration including mutation in oncogenes and tumor suppressor genes transforms normal cells into tumor cells. Epigenetic modifications work concertedly with genetic factors in controlling cancer development. Histone acetyltransferases (HATs), histone deacetylases (HDACs), DNA methyltransferases (DNMTs) and chromatin structure modifier are prospective epigenetic regulators. Specifically, HDACs are histone modifiers regulating the expression of genes implicated in cell survival, growth, apoptosis, and metabolism. The majority of HDACs are highly upregulated in cancer, whereas some have a varied function and expression in cancer progression. Distinct HDACs have a positive and negative role in controlling cancer progression. HDACs are also significantly involved in tumor cells acquiring metastatic and angiogenic potential in order to withstand the anti-tumor microenvironment. HDACs' role in modulating metabolic genes has also been associated with tumor development and survival. This review highlights and discusses the molecular mechanisms of HDACs by which they regulate cell survival, apoptosis, metastasis, invasion, stemness potential, angiogenesis, and epithelial to mesenchymal transitions (EMT) in tumor cells. HDACs are the potential target for anti-cancer drug development and various inhibitors have been developed and FDA approved for a variety of cancers. The primary HDAC inhibitors with proven anti-cancer efficacy have also been highlighted in this review.

Small Molecule Inhibitors in Adult High-Grade Glioma: From the Past to the Future

Glioblastoma is the most common primary malignant tumor in the brain and has a dismal prognosis despite patients accepting standard therapies. Alternation of genes and deregulation of proteins, such as receptor tyrosine kinase, PI3K/Akt, PKC, Ras/Raf/MEK, histone deacetylases, poly (ADP-ribose) polymerase (PARP), CDK4/6, branched-chain amino acid transaminase 1 (BCAT1), and Isocitrate dehydrogenase (IDH), play pivotal roles in the pathogenesis and progression of glioma. Simultaneously, the abnormalities change the cellular biological behavior and microenvironment of tumor cells. The differences between tumor cells and normal tissue become the vulnerability of tumor, which can be taken advantage of using targeted therapies. Small molecule inhibitors, as an important part of modern treatment for cancers, have shown significant efficacy in hematologic cancers and some solid tumors. To date, in glioblastoma, there have been more than 200 clinical trials completed or ongoing in which trial designers used small molecules as monotherapy or combination regimens to correct the abnormalities. In this review, we summarize the dysfunctional molecular mechanisms and highlight the outcomes of relevant clinical trials associated with small-molecule targeted therapies. Based on the outcomes, the main findings were that small-molecule inhibitors did not bring more benefit to newly diagnosed glioblastoma, but the clinical studies involving progressive glioblastoma usually claimed “noninferiority” compared with historical results. However, as to the clinical inferiority trial, similar dosing regimens should be avoided in future clinical trials.

Givinostat-Liposomes: Anti-Tumor Effect on 2D and 3D Glioblastoma Models and Pharmacokinetics

Glioblastoma is the most common and aggressive brain tumor, associated with poor prognosis and survival, representing a challenging medical issue for neurooncologists. Dysregulation of histone-modifying enzymes (HDACs) is commonly identified in many tumors and has been linked to cancer proliferation, changes in metabolism, and drug resistance. These findings led to the development of HDAC inhibitors, which are limited by their narrow therapeutic index. In this work, we provide the proof of concept for a delivery system that can improve the in vivo half-life and increase the brain delivery of Givinostat, a pan-HDAC inhibitor. Here, 150-nm-sized liposomes composed of cholesterol and sphingomyelin with or without surface decoration with mApoE peptide, inhibited human glioblastoma cell growth in 2D and 3D models by inducing a time- and dose-dependent reduction in cell viability, reduction in the receptors involved in cholesterol metabolism (from -25% to -75% of protein levels), and reduction in HDAC activity (-25% within 30 min). In addition, liposome-Givinostat formulations showed a 2.5-fold increase in the drug half-life in the bloodstream and a 6-fold increase in the amount of drug entering the brain in healthy mice, without any signs of overt toxicity. These features make liposomes loaded with Givinostat valuable as potential candidates for glioblastoma therapy.

Have molecular hybrids delivered effective anti-cancer treatments and what should future drug discovery focus on?

INTRODUCTION

Cancer continues to be a big threat and its treatment is a huge challenge among the medical fraternity. Conventional anti-cancer agents are losing their efficiency which highlights the need to introduce new anti-cancer entities for treating this complex disease. A hybrid molecule has a tendency to act through varied modes of action on multiple targets at a given time. Thus, there is the significant scope with hybrid compounds to tackle the existing limitations of cancer chemotherapy.

AREA COVERED

This perspective describes the most significant hybrids that spring hope in the field of cancer chemotherapy. Several hybrids with anti-proliferative/anti-tumor properties currently approved or in clinical development are outlined, along with a description of their mechanism of action and identified drug targets.

EXPERT OPINION

The success of molecular hybridization in cancer chemotherapy is quite evident by the number of molecules entering into clinical trials and/or have entered the drug market over the past decade. Indeed, the recent advancements and co-ordinations in the interface between chemistry, biology, and pharmacology will help further the advancement of hybrid chemotherapeutics in the future.List of abbreviations: Deoxyribonucleic acid, DNA; national cancer institute, NCI; peripheral blood mononuclear cells, PBMC; food and drug administration, FDA; histone deacetylase, HDAC; epidermal growth factor receptor, EGFR; vascular endothelial growth factor receptor, VEGFR; suberoylanilide hydroxamic acid, SAHA; farnesyltransferase inhibitor, FTI; adenosine triphosphate, ATP; Tamoxifen, TAM; selective estrogen receptor modulator, SERM; structure activity relationship, SAR; estrogen receptor, ER; lethal dose, LD; half maximal growth inhibitory concentration, GI₅₀; half maximal inhibitory concentration, IC₅₀.

Advances in Epigenetic Cancer Therapeutics

Cancer has traditionally been hailed a genetic disease, dictated by successive genetic aberrations which alter gene expression. Yet, recent advances in molecular sequencing technologies, enabling the characterisation of cancer patient phenotypes on a large scale, have highlighted epigenetic changes as a hallmark of cancer. Epigenetic modifications, including DNA methylation and demethylation and histone modifications, have been found to play a key role in the pathogenesis of a wide variety of cancers through the regulation of chromatin state, gene expression and other nuclear events. Targeting epigenetic aberrations offers remarkable promise as a potential anti-cancer therapy given the reversible nature of epigenetic changes. Hence, epigenetic therapy has emerged as a rapidly advancing field of cancer research. A plethora of epigenetic therapies which inhibit enzymes of post-translational histone modifications, so-called 'writers', 'erasers' and 'readers', have been developed, with several epigenetic inhibitor agents approved for use in routine clinical practice. Epigenetic therapeutics inhibit the methylation or demethylation and acetylation or deacetylation of DNA and histone proteins. Their targets include writers (DNA methyltransferases [DNMT], histone acetyltransferases [HAT] and histone deacetylases [HDAC]) and erasers (histone demethylases [HDM] and histone methylases [HMT]). With new epigenetic mechanisms increasingly being elucidated, a vast array of targets and therapeutics have been brought to the fore. This review discusses recent advances in cancer epigenetics with a focus on molecular targets and mechanisms of action of epigenetic cancer therapeutics.

An immunochemistry-based screen for chemical inhibitors of DNA-protein interactions and its application to human CGGBP1

BACKGROUND

Inhibition of DNA-binding of proteins by small-molecule chemicals holds immense potential in manipulating the activities of DNA-binding proteins. Such a chemical inhibition of DNA-binding of proteins can be used to modulate processes such as replication, transcription, DNA repair and maintenance of epigenetic states. This prospect is currently challenged with the absence of robust and generic protocols to identify DNA-protein interactions. Additionally, much of the current approaches to designing inhibitors requires structural information of the target proteins.

METHODS

We have developed a simple dot blot and immunodetection-based assay to screen chemical libraries for inhibitors of DNA-protein interactions. The assay has been applied to a library of 1685 FDA-approved chemicals to discover inhibitors of CGGBP1, a multifunctional DNA-binding protein with no known structure. Additional in vitro and in cellulo assays have been performed to verify and supplement the findings of the screen.

RESULTS

Our primary screen has identified multiple inhibitors of direct or indirect interactions between CGGBP1 and genomic DNA. Of these, one inhibitor, Givinostat, was found to inhibit direct DNA-binding of CGGBP1 in the secondary screen using purified recombinant protein as the target. DNA and chromatin immunoprecipitation assays reinforced the findings of the screen that Givinostat inhibits CGGBP1-DNA binding.

CONCLUSIONS

The assay we have described successfully identifies verifiable inhibitors of DNA-binding of protein; in this example, the human CGGBP1. This assay is customizable for a wide range of targets for which primary antibodies are available. It works with different sources of the target protein, cell lysates or purified recombinant preparations and does not require special equipment, DNA modifications or protein structural data. This assay is scalable and highly adaptable with the potential to discover inhibitors of transcription factors with implications in cancer biology.

Advances in histone deacetylase inhibitors in targeting glioblastoma stem cells

Glioblastoma multiforme (GBM) is a lethal grade IV glioma (WHO classification) and widely prevalent primary brain tumor in adults. GBM tumors harbor cellular heterogeneity with the presence of a small subpopulation of tumor cells, described as GBM cancer stem cells (CSCs) that pose resistance to standard anticancer regimens and eventually mediate aggressive relapse or intractable progressive GBM. Existing conventional anticancer therapies for GBM do not target GBM stem cells and are mostly palliative; therefore, exploration of new strategies to target stem cells of GBM has to be prioritized for the development of effective GBM therapy. Recent developments in the understanding of GBM pathophysiology demonstrated dysregulation of epigenetic mechanisms along with the genetic changes in GBM CSCs. Altered expression/activity of key epigenetic regulators, especially histone deacetylases (HDACs) in GBM stem cells has been associated with poor prognosis; inhibiting the activity of HDACs using histone deacetylase inhibitors (HDACi) has been promising as mono-therapeutic in targeting GBM and in sensitizing GBM stem cells to an existing anticancer regimen. Here, we review the development of pan/selective HDACi as potential anticancer agents in targeting the stem cells of glioblastoma as a mono or combination therapy.

Givinostat: an emerging treatment for polycythemia vera

INTRODUCTION

Polycythemia vera (PV), a Philadelphia chromosome-negative myeloproliferative neoplasm, is characterized by panmyelosis, pancytosis, and a JAK2 mutation. Patients are at increased risk of thrombohemorrhagic events, and progression to myelofibrosis or acute leukemia. Current treatments include aspirin, phlebotomy, and cytoreductive drugs (most commonly hydroxyurea). Givinostat is a potent, class I/II histone deacetylase (HDAC) inhibitor that is in phase I/II clinical trials in PV. Givinostat was well tolerated and yielded promising clinico-hematological responses. A phase III study of givinostat versus hydroxyurea in high-risk PV patients is planned.

AREAS COVERED

We present an overview of PV, current treatment guidelines, and the putative mechanism(s) of action of givinostat. We discuss the preclinical and clinical studies of givinostat in PV and briefly review approved and investigational competitor compounds.

EXPERT OPINION

HDAC inhibitors have long been known to be active in PV, but chronic toxicities can be challenging. Givinostat, however, is active and well tolerated, and is entering a pivotal Phase III randomized trial. Givinostat offers the possibility of replacing hydroxyurea as the standard first-line cytoreductive choice for PV patients. This would completely change the current therapeutic paradigm and guidelines for PV management. Although surrogate clinical study endpoints may suffice for regulatory purposes, thrombosis reduction and prevention of disease progression remain most important to patients and clinicians.

DNA damage response signaling pathways and targets for radiotherapy sensitization in cancer

Radiotherapy is one of the most common countermeasures for treating a wide range of tumors. However, the radioresistance of cancer cells is still a major limitation for radiotherapy applications. Efforts are continuously ongoing to explore sensitizing targets and develop radiosensitizers for improving the outcomes of radiotherapy. DNA double-strand breaks are the most lethal lesions induced by ionizing radiation and can trigger a series of cellular DNA damage responses (DDRs), including those helping cells recover from radiation injuries, such as the activation of DNA damage sensing and early transduction pathways, cell cycle arrest, and DNA repair. Obviously, these protective DDRs confer tumor radioresistance. Targeting DDR signaling pathways has become an attractive strategy for overcoming tumor radioresistance, and some important advances and breakthroughs have already been achieved in recent years. On the basis of comprehensively reviewing the DDR signal pathways, we provide an update on the novel and promising druggable targets emerging from DDR pathways that can be exploited for radiosensitization. We further discuss recent advances identified from preclinical studies, current clinical trials, and clinical application of chemical inhibitors targeting key DDR proteins, including DNA-PKcs (DNA-dependent protein kinase, catalytic subunit), ATM/ATR (ataxia-telangiectasia mutated and Rad3-related), the MRN (MRE11-RAD50-NBS1) complex, the PARP (poly[ADP-ribose] polymerase) family, MDC1, Wee1, LIG4 (ligase IV), CDK1, BRCA1 (BRCA1 C terminal), CHK1, and HIF-1 (hypoxia-inducible factor-1). Challenges for ionizing radiation-induced signal transduction and targeted therapy are also discussed based on recent achievements in the biological field of radiotherapy.

Advances in the Knowledge of the Molecular Biology of Glioblastoma and Its Impact in Patient Diagnosis, Stratification, and Treatment

Gliomas are the most common primary brain tumors in adults. They arise in the glial tissue and primarily occur in the brain. Low-grade tumors of World Health Organization (WHO) grade II tend to progress to high-grade gliomas of WHO grade III and, eventually, glioblastoma of WHO grade IV, which is the most common and deadly glioma, with a median survival of 12-15 months after final diagnosis. Knowledge of the molecular biology and genetics of glioblastoma has increased significantly in the past few years, giving rise to classification methods that can help in management and stratification of glioblastoma patients. However, glioblastoma remains an incurable disease. Glioblastoma cells have acquired genetic and metabolic adaptations in order to sustain tumor growth and progression, including changes in energetic metabolism, invasive capacity, migration, and angiogenesis, that make it very difficult to find suitable therapeutic targets and to develop effective drugs. The current standard of care for glioblastoma patients is surgery followed by radiotherapy plus concomitant and adjuvant chemotherapy with temozolomide. Although progress in glioblastoma therapies in recent years has been more limited than in other tumors, numerous drugs and targets are being proposed and many clinical trials are underway to develop effective subtype-specific treatments.

Epigenetic Control of Autophagy in Cancer Cells: A Key Process for Cancer-Related Phenotypes

Although autophagy is a well-known and extensively described cell pathway, numerous studies have been recently interested in studying the importance of its regulation at different molecular levels, including the translational and post-translational levels. Therefore, this review focuses on the links between autophagy and epigenetics in cancer and summarizes the. following: (i) how ATG genes are regulated by epigenetics, including DNA methylation and post-translational histone modifications; (ii) how epidrugs are able to modulate autophagy in cancer and to alter cancer-related phenotypes (proliferation, migration, invasion, tumorigenesis, etc.) and; (iii) how epigenetic enzymes can also regulate autophagy at the protein level. One noteable observation was that researchers most often reported conclusions about the regulation of the autophagy flux, following the use of epidrugs, based only on the analysis of LC3B-II form in treated cells. However, it is now widely accepted that an increase in LC3B-II form could be the consequence of an induction of the autophagy flux, as well as a block in the autophagosome-lysosome fusion. Therefore, in our review, all the published results describing a link between epidrugs and autophagy were systematically reanalyzed to determine whether autophagy flux was indeed increased, or inhibited, following the use of these potentially new interesting treatments targeting the autophagy process. Altogether, these recent data strongly support the idea that the determination of autophagy status could be crucial for future anticancer therapies. Indeed, the use of a combination of epidrugs and autophagy inhibitors could be beneficial for some cancer patients, whereas, in other cases, an increase of autophagy, which is frequently observed following the use of epidrugs, could lead to increased autophagy cell death.

Discovery of a novel rhein-SAHA hybrid as a multi-targeted anti-glioblastoma drug

Glioblastoma multiforme (GBM) is the most common malignant tumor of the central nervous system (CNS). Effective treatments remain limited. Therefore, novel chemotherapy drugs with high efficiency and few adverse effects are urgently needed. Histone deacetylase (HDAC) and serum and glucocorticoid-regulated protein kinase 1 (SGK1) are targets for the prevention and treatment of GBM. Rhein has antitumor and SGK1 suppression effects, although its biological activity is limited by poor bioavailability. To improve the drug-like properties of rhein, we constructed a novel rhein-hydroxyethyl hydroxamic acid derivative (SYSUP007), which combined rhein with the HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA). In the present study, the human GBM cell lines, T98G, U87 and U251, were used to investigate the anticancer effects of SYSUP007 in vitro. We found that SYSUP007 was more effective in inhibiting glioma cell proliferation, invasion and migration in vitro compared with the effects of rhein and SAHA. We also confirmed that SYSUP007 increased the expression of Ac-K100 and NDRG1 (targets of HDAC and SGK1). The present study indicates the potential that SYSUP007, as a novel rhein and SAHA derivative, for development as an anti-cancer therapy.

The Autophagy Status of Cancer Stem Cells in Gliobastoma Multiforme: From Cancer Promotion to Therapeutic Strategies

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor featuring rapid cell proliferation, treatment resistance, and tumor relapse. This is largely due to the coexistence of heterogeneous tumor cell populations with different grades of differentiation, and in particular, to a small subset of tumor cells displaying stem cell-like properties. This is the case of glioma stem cells (GSCs), which possess a powerful self-renewal capacity, low differentiation, along with radio- and chemo-resistance. Molecular pathways that contribute to GBM stemness of GSCs include mTOR, Notch, Hedgehog, and Wnt/β-catenin. Remarkably, among the common biochemical effects that arise from alterations in these pathways, autophagy suppression may be key in promoting GSCs self-renewal, proliferation, and pluripotency maintenance. In fact, besides being a well-known downstream event of mTOR hyper-activation, autophagy downregulation is also bound to the effects of aberrantly activated Notch, Hedgehog, and Wnt/β-catenin pathways in GBM. As a major orchestrator of protein degradation and turnover, autophagy modulates proliferation and differentiation of normal neuronal stem cells (NSCs) as well as NSCs niche maintenance, while its failure may contribute to GSCs expansion and maintenance. Thus, in the present review we discuss the role of autophagy in GSCs metabolism and phenotype in relationship with dysregulations of a variety of NSCs controlling pathways, which may provide novel insights into GBM neurobiology.

NRF2 orchestrates the redox regulation induced by radiation therapy, sustaining embryonal and alveolar rhabdomyosarcoma cells radioresistance

PURPOSE

Tumor cells generally exhibit higher levels of reactive oxygen species (ROS), however, when stressed, tumor cells can undergo a process of 'Redox Resetting' to acquire a new redox balance with stronger antioxidant systems that enable cancer cells to become resistant to radiation therapy (RT). Here, we describe how RT affects the oxidant/antioxidant balance in human embryonal (RD) and alveolar (RH30) rhabdomyosarcoma (RMS) cell lines, investigating on the molecular mechanisms involved.

METHODS

Radiations were delivered using an x-6 MV photon linear accelerator and their effects were assessed by vitality and clonogenic assays. The expression of specific antioxidant-enzymes, such as Superoxide Dismutases (SODs), Catalase (CAT) and Glutathione Peroxidases 4 (GPx4), miRNAs (miR-22, -126, -210, -375, -146a, -34a) and the transcription factor NRF2 was analyzed by quantitative polymerase chain reaction (q-PCR) and western blotting. RNA interference experiments were performed to evaluate the role of NRF2.

RESULTS

Doses of RT higher than 2 Gy significantly affected RMS clonogenic ability by increasing ROS production. RMS rapidly and efficiently brought back ROS levels by up-regulating the gene expression of antioxidant enzymes, miRNAs as well as of NRF2. Silencing of NRF2 restrained the RMS ability to counteract RT-induced ROS accumulation, antioxidant enzyme and miRNA expression and was able to increase the abundance of γ-H2AX, a biomarker of DNA damage, in RT-treated cells.

CONCLUSIONS

Taken together, our data suggest the strategic role of oxidant/antioxidant balance in restraining the therapeutic efficiency of RT in RMS treatment and identify NRF2 as a new potential molecular target whose inhibition might represent a novel radiosensitizing therapeutic strategy for RMS clinical management.