Inhibitory activities of trichostatin a in U87 glioblastoma cells and tumorsphere-derived cells

Introducing HDAC-Targeting Radiopharmaceuticals for Glioblastoma Imaging and Therapy

Despite recent advances in multimodality therapy for glioblastoma (GB) incorporating surgery, radiotherapy, chemotherapy and targeted therapy, the overall prognosis remains poor. One of the interesting targets for GB therapy is the histone deacetylase family (HDAC). Due to their pleiotropic effects on, e.g., DNA repair, cell proliferation, differentiation, apoptosis and cell cycle, HDAC inhibitors have gained a lot of attention in the last decade as anti-cancer agents. Despite their known underlying mechanism, their therapeutic activity is not well-defined. In this review, an extensive overview is given of the current status of HDAC inhibitors for GB therapy, followed by an overview of current HDAC-targeting radiopharmaceuticals. Imaging HDAC expression or activity could provide key insights regarding the role of HDAC enzymes in gliomagenesis, thus identifying patients likely to benefit from HDACi-targeted therapy.

Pharmacological Properties of Trichostatin A, Focusing on the Anticancer Potential: A Comprehensive Review

Trichostatin A (TSA), a natural derivative of dienohydroxamic acid derived from a fungal metabolite, exhibits various biological activities. It exerts antidiabetic activity and reverses high glucose levels caused by the downregulation of brain-derived neurotrophic factor (BDNF) expression in Schwann cells, anti-inflammatory activity by suppressing the expression of various cytokines, and significant antioxidant activity by suppressing oxidative stress through multiple mechanisms. Most importantly, TSA exhibits potent inhibitory activity against different types of cancer through different pathways. The anticancer activity of TSA appeared in many in vitro and in vivo investigations that involved various cell lines and animal models. Indeed, TSA exhibits anticancer properties alone or in combination with other drugs used in chemotherapy. It induces sensitivity of some human cancers toward chemotherapeutical drugs. TSA also exhibits its action on epigenetic modulators involved in cell transformation, and therefore it is considered an epidrug candidate for cancer therapy. Accordingly, this work presents a comprehensive review of the most recent developments in utilizing this natural compound for the prevention, management, and treatment of various diseases, including cancer, along with the multiple mechanisms of action. In addition, this review summarizes the most recent and relevant literature that deals with the use of TSA as a therapeutic agent against various diseases, emphasizing its anticancer potential and the anticancer molecular mechanisms. Moreover, TSA has not been involved in toxicological effects on normal cells. Furthermore, this work highlights the potential utilization of TSA as a complementary or alternative medicine for preventing and treating cancer, alone or in combination with other anticancer drugs.

Molecular Mechanisms of Vascular Damage During Lung Injury

A variety of pulmonary and systemic insults promote an inflammatory response causing increased vascular permeability, leading to the development of acute lung injury (ALI), a condition necessitating hospitalization and intensive care, or the more severe acute respiratory distress syndrome (ARDS), a disease with a high mortality rate. Further, COVID-19 pandemic-associated ARDS is now a major cause of mortality worldwide. The pathogenesis of ALI is explained by injury to both the vascular endothelium and the alveolar epithelium. The disruption of the lung endothelial and epithelial barriers occurs in response to both systemic and local production of pro-inflammatory cytokines. Studies that evaluate the association of genetic polymorphisms with disease risk did not yield many potential therapeutic targets to treat and revert lung injury. This failure is probably due in part to the phenotypic complexity of ALI/ARDS, and genetic predisposition may be obscured by the multiple environmental and behavioral risk factors. In the last decade, new research has uncovered novel epigenetic mechanisms that control ALI/ARDS pathogenesis, including histone modifications and DNA methylation. Enzyme inhibitors such as DNMTi and HDACi may offer new alternative strategies to prevent or reverse the vascular damage that occurs during lung injury. This review will focus on the latest findings on the molecular mechanisms of vascular damage in ALI/ARDS, the genetic factors that might contribute to the susceptibility for developing this disease, and the epigenetic changes observed in humans, as well as in experimental models of ALI/ADRS.

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.

Combined Inhibition of HDAC and EGFR Reduces Viability and Proliferation and Enhances STAT3 mRNA Expression in Glioblastoma Cells

Changes in expression of histone deacetylases (HDACs), which epigenetically regulate chromatin structure, and mutations and amplifications of the EGFR gene, which codes for the epidermal growth factor receptor (EGFR), have been reported in glioblastoma (GBM), the most common and malignant type of brain tumor. There are likely interplays between HDACs and EGFR in promoting GBM progression, and HDAC inhibition can cooperate with EGFR blockade in reducing the growth of lung cancer cells. Here, we found that either HDAC or EGFR inhibitors dose-dependently reduced the viability of U87 and A-172 human GBM cells. In U87 cells, the combined inhibition of HDACs and EGFR was more effective than inhibiting either target alone in reducing viability and long-term proliferation. In addition, HDAC or EGFR inhibition, alone or combined, led to G0/G1 cell cycle arrest. The EGFR inhibitor alone or combined with HDAC inhibition increased mRNA expression of the signal transducer and activator of transcription 3 (STAT3), which can act either as an oncogene or a tumor suppressor in GBM. These data provide early evidence that combining HDAC and EGFR inhibition may be an effective strategy to reduce GBM growth, through a mechanism possibly involving STAT3.

Molecular imaging HDACs class IIa expression-activity and pharmacologic inhibition in intracerebral glioma models in rats using PET/CT/(MRI) with [18F]TFAHA

HDAC class IIa enzymes (HDAC4, 5, 7, 9) are important for glioma progression, invasion, responses to TMZ and radiotherapy, and prognosis. In this study, we demonstrated the efficacy of PET/CT/(MRI) with [¹⁸F]TFAHA for non-invasive and quantitative imaging of HDAC class IIa expression-activity in intracerebral 9L and U87-MG gliomas in rats. Increased accumulation of [¹⁸F]TFAHA in 9L and U87-MG tumors was observed at 20 min post radiotracer administration with SUV of 1.45 ± 0.05 and 1.08 ± 0.05, respectively, and tumor-to-cortex SUV ratios of 1.74 ± 0.07 and 1.44 ± 0.03, respectively. [¹⁸F]TFAHA accumulation was also observed in normal brain structures known to overexpress HDACs class IIa: hippocampus, n.accumbens, PAG, and cerebellum. These results were confirmed by immunohistochemical staining of brain tissue sections revealing the upregulation of HDACs 4, 5, and 9, and HIF-1α, hypoacetylation of H2AK5ac, H2BK5ac, H3K9ac, H4K8ac, and downregulation of KLF4. Significant reduction in [¹⁸F]TFAHA accumulation in 9L tumors was observed after administration of HDACs class IIa specific inhibitor MC1568, but not the SIRT1 specific inhibitor EX-527. Thus, PET/CT/(MRI) with [¹⁸F]TFAHA can facilitate studies to elucidate the roles of HDAC class IIa enzymes in gliomagenesis and progression and to optimize therapeutic doses of novel HDACs class IIa inhibitors in gliomas.

Under explored epigenetic modulators: role in glioma chemotherapy

Patients with somatic mutations of epigenetic regulators are characterized by aberrant chromatin modification patterns. Recent mechanistic studies pairing chemical tool compounds and deep-sequencing technology have greatly broadened our understanding of epigenetic regulation in glioma progression and underpinned alternative treatment of epigenetic inhibitors. However, the effect of most inhibitors is condition-dependent, and the overall results of clinical trials still have not been applied to patients. There is an intense need to develop more potent and specific compounds as well as identify the population who may achieve clinical benefits. Besides, combination therapy with conventional therapeutics is another alternative strategy. In this review, we summarize well-characterized chemical probes in glioma research and clinical translation. We also discuss the target population and combination of therapy regimens of various agents. In a holistic sense, we try to provide guidance for selecting targeted chemical probes and pave the way for personalized rational therapy.

Combination Therapy with Sulfasalazine and Valproic Acid Promotes Human Glioblastoma Cell Death Through Imbalance of the Intracellular Oxidative Response

Glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor and still lacks effective therapeutic strategies. It has already been shown that old drugs like sulfasalazine (SAS) and valproic acid (VPA) present antitumoral activities in glioma cell lines. SAS has also been associated with a decrease of intracellular glutathione (GSH) levels through a potent inhibition of xc- glutamate/cystine exchanger leading to an antioxidant deprotection. In the same way, VPA was recently identified as a histone deacetylase (HDAT) inhibitor capable of activating tumor suppression genes. As both drugs are widely used in clinical practice and their profile of adverse effects is well known, the aim of our study was to investigate the effects of the combined treatment with SAS and VPA in GBM cell lines. We observed that both drugs were able to reduce cell viability in a dose-dependent manner and the combined treatment potentiated these effects. Combined treatment also increased cell death and inhibited proliferation of GBM cells, while having no effect on human and rat cultured astrocytes. Also, we observed high protein expression of the catalytic subunit of xc- in all the examined GBM cell lines, and treatment with SAS blocked its activity and decreased intracellular GSH levels. Noteworthy, SAS but not VPA was also able to reduce the [¹⁴C]-ascorbate uptake. Together, these data indicate that SAS and VPA exhibit a substantial effect on GBM cell's death related to an intracellular oxidative response imbalance, making this combination of drugs a promising therapeutic strategy.

RNAi for contactin 2 inhibits proliferation of U87-glioma stem cells by downregulating AICD, EGFR, and HES1

Glioblastoma is the most common form of malignant brain tumors and has a poor prognosis. Glioma stem cells (GSCs) are thought to be responsible for the aberrant proliferation and invasion. Targeting the signaling pathways that promote proliferation in GSCs is one of the strategies for glioma treatment. In this study, we found increased expression of contactin 2 (CNTN2) and amyloid β precursor protein (APP) in U87-derived GSCs (U87-GSCs). RNA interference (RNAi) for CNTN2 downregulated the expression of APP intracellular domain (AICD), which is the proteolytic product of APP. Treatment with CNTN2 RNAi inhibited the proliferation of U87-GSCs. CNTN2 RNAi decreased the expression of epidermal growth factor receptor and HES1, which are potential targets of AICD. In summary, inhibition of the CNTN2/APP signaling pathway may repress the proliferation in U87-GSCs via downregulating the expression of HES1 and epidermal growth factor receptor. CNTN2/APP/AICD signaling pathway plays an important role in U87 glial tumorigenesis. Further studies are warranted to elucidate the role of these signaling pathways in other sources of GSCs. Depending on their role in proliferation in other sources of GSCs, members of the CNTN2/APP/AICD signaling pathway may provide novel targets for the development of therapy for glioblastomas.

Inhibition of histone deacetylases sensitizes glioblastoma cells to lomustine

PURPOSE

Glioblastoma (GBM) ranks among the deadliest solid cancers worldwide and its prognosis has remained dismal, despite the use of aggressive chemo-irradiation treatment regimens. Limited drug delivery into the brain parenchyma and frequent resistance to currently available therapies are problems that call for a prompt development of novel therapeutic strategies. While only displaying modest efficacies as mono-therapy in pre-clinical settings, histone deacetylase inhibitors (HDACi) have shown promising sensitizing effects to a number of cytotoxic agents. Here, we sought to investigate the sensitizing effect of the HDACi trichostatin A (TSA) to the alkylating agent lomustine (CCNU), which is used in the clinic for the treatment of GBM.

METHODS

Twelve primary GBM cell cultures grown as neurospheres were used in this study, as well as one established GBM-derived cell line (U87 MG). Histone deacetylase (HDAC) expression levels were determined using quantitative real-time PCR and Western blotting. The efficacy of either CCNU alone or its combination with TSA was assessed using various assays, i.e., cell viability assays (MTT), cell cycle assays (flow cytometry, FACS), double-strand DNA break (DSB) quantification assays (microscopy/immunofluorescence) and expression profiling assays of proteins involved in apoptosis and cell stress (Western blotting and protein array).

RESULTS

We found that the HDAC1, 3 and 6 expression levels were significantly increased in GBM samples compared to non-neoplastic brain control samples. Additionally, we found that pre-treatment of GBM cells with TSA resulted in an enhancement of their sensitivity to CCNU, possibly via the accumulation of DSBs, decreased cell proliferation and viability rates, and an increased apoptotic rate.

CONCLUSION

From our data we conclude that the combined administration of TSA and CCNU eradicates GBM cells with a higher efficacy than either drug alone, thereby opening a novel avenue for the treatment of GBM.

Spheres from cervical cancer cells display stemness and cancer drug resistance

Cervical cancer is one of the most common gynecological malignant tumors and is the cause of a serious health problem worldwide. An increasing amount of evidence has shown that cancer stem cells (CSCs) are present in tumors, and that these CSCs may be responsible for tumor metastasis and relapse. The present study aimed to identify and characterize a CSC population from the CaSki cell line. First, a stem cell culture medium was used to selectively expand the cancer stem-like cell spheres, and the putative stemness markers, Oct4 and Sox2, were identified. These markers were all highly expressed in the CaSki sphere-forming cells. Next, target region amplified polymorphism-polymerase chain reaction was performed and the CaSki sphere-forming cells were found to exhibit higher telomerase activity than the CaSki control cells cultured in non-stem cell medium. Using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, it was found that the CaSki sphere-forming cells were more resistant to chemotherapeutic drugs than the control CaSki cells. Using the tumor invasive assay, it was shown that the CaSki sphere-forming cells were more invasive than the control CaSki cells. These characteristics all suggested that the tumor sphere-forming cells mirrored the acknowledged CSC phenotypes. Overall, the use of a suspended sphere culture of CaSki cells may be an easy and feasible approach for enriching cancer stem-like cells in cervical cancer research.

Histone deacetylase inhibitors for the treatment of cancer stem cells

HDAC inhibitors are a promising group of epigenetic drugs that show the ability to induce apoptosis in cancer stem cells.

Epigenetic modifiers reduce inflammation and modulate macrophage phenotype during endotoxemia-induced acute lung injury

Acute lung injury (ALI) during sepsis is characterized by bilateral alveolar infiltrates, lung edema and respiratory failure. Here, we examined the efficacy the DNA methyl transferase (DNMT) inhibitor 5-Aza 2-deoxycytidine (Aza), the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), as well as the combination therapy of Aza and TSA (Aza+TSA) provides in the protection of ALI. In LPS-induced mouse ALI, post-treatment with a single dose of Aza+TSA showed substantial attenuation of adverse lung histopathological changes and inflammation. Importantly, these protective effects were due to substantial macrophage phenotypic changes observed in LPS-stimulated macrophages treated with Aza+TSA as compared with untreated LPS-induced macrophages or LPS-stimulated macrophages treated with either drug alone. Further, we observed significantly lower levels of pro-inflammatory molecules and higher levels of anti-inflammatory molecules in LPS-induced macrophages treated with Aza+TSA than in LPS-induced macrophages treated with either drug alone. The protection was ascribed to dual effects by an inhibition of MAPK-HuR-TNF and activation of STAT3-Bcl2 pathways. Combinatorial treatment with Aza+TSA reduces inflammation and promotes an anti-inflammatory M2 macrophage phenotype in ALI, and has a therapeutic potential for patients with sepsis.

Combinatorial therapy with acetylation and methylation modifiers attenuates lung vascular hyperpermeability in endotoxemia-induced mouse inflammatory lung injury

Impairment of tissue fluid homeostasis and migration of inflammatory cells across the vascular endothelial barrier are crucial factors in the pathogenesis of acute lung injury (ALI). The goal for treatment of ALI is to target pathways that lead to profound dysregulation of the lung endothelial barrier. Although studies have shown that chemical epigenetic modifiers can limit lung inflammation in experimental ALI models, studies to date have not examined efficacy of a combination of DNA methyl transferase inhibitor 5-Aza 2-deoxycytidine and histone deacetylase inhibitor trichostatin A (herein referred to as Aza+TSA) after endotoxemia-induced mouse lung injury. We tested the hypothesis that treatment with Aza+TSA after lipopolysaccharide induction of ALI through epigenetic modification of lung endothelial cells prevents inflammatory lung injury. Combinatorial treatment with Aza+TSA mitigated the increased endothelial permeability response after lipopolysaccharide challenge. In addition, we observed reduced lung inflammation and lung injury. Aza+TSA also significantly reduced mortality in the ALI model. The protection was ascribed to inhibition of the eNOS-Cav1-MLC2 signaling pathway and enhanced acetylation of histone markers on the vascular endothelial-cadherin promoter. In summary, these data show for the first time the efficacy of combinatorial Aza+TSA therapy in preventing ALI in lipopolysaccharide-induced endotoxemia and raise the possibility of an essential role of DNA methyl transferase and histone deacetylase in the mechanism of ALI.