An ensemble machine learning model generates a focused screening library for the identification of CDK8 inhibitors.

The identification of an effective inhibitor is an important starting step in drug development. Unfortunately, many issues such as the characterization of protein binding sites, the screening library, materials for assays, etc., make drug screening a difficult proposition. As the size of screening libraries increases, more resources will be inefficiently consumed. Thus, new strategies are needed to preprocess and focus a screening library towards a targeted protein. Herein, we report an ensemble machine learning (ML) model to generate a CDK8-focused screening library. The ensemble model consists of six different algorithms optimized for CDK8 inhibitor classification. The models were trained using a CDK8-specific fragment library along with molecules containing CDK8 activity. The optimized ensemble model processed a commercial library containing 1.6 million molecules. This resulted in a CDK8-focused screening library containing 1,672 molecules, a reduction of more than 99.90%. The CDK8-focused library was then subjected to molecular docking, and 25 candidate compounds were selected. Enzymatic assays confirmed six CDK8 inhibitors, with one compound producing an IC50 value of ≤100 nM. Analysis of the ensemble ML model reveals the role of the CDK8 fragment library during training. Structural analysis of molecules reveals the hit compounds to be structurally novel CDK8 inhibitors. Together, the results highlight a pipeline for curating a focused library for a specific protein target, such as CDK8.

Anticancer Study of a Novel Pan-HDAC Inhibitor MPT0G236 in Colorectal Cancer Cells.

Colorectal cancer (CRC) is one of the most commonly diagnosed malignancies and a leading cause of cancer worldwide. Histone deacetylases (HDACs), which regulate cell proliferation and survival, are associated with the development and progression of cancer. Moreover, HDAC inhibitors are promising therapeutic targets, with five HDAC inhibitors approved for cancer treatment to date. However, their safety profile necessitates the exploration of well-tolerated HDAC inhibitors that can be used in cancer therapeutic strategies. In this study, the pan-HDAC inhibitor MPT0G236 reduced the viability and inhibited the proliferation of human colorectal cancer cells, and normal human umbilical vein endothelial cells (HUVECs) showed reduced sensitivity. These findings indicated that MPT0G236 specifically targeted malignant tumor cells. Notably, MPT0G236 significantly inhibited the activities of HDAC1, HDAC2, and HDAC3, Class I HDACs, as well as HDAC6, a Class IIb HDAC, at low nanomolar concentrations. Additionally, it promoted the accumulation of acetyl-α-tubulin and acetyl-histone H3 in HCT-116 and HT-29 cells in a concentration-dependent manner. Furthermore, MPT0G236 treatment induced G2/M cell cycle arrest in CRC cells by initially regulating the levels of cell-cycle-related proteins, such as p-MPM2; specifically reducing p-cdc2 (Y15), cyclin B1, and cdc25C levels; and subsequently inducing apoptosis through the caspase-dependent pathways and PARP activation. Our findings demonstrate that MPT0G236 exhibits significant anticancer activity in human colorectal cancer cells.

The study of a novel CDK8 inhibitor E966-0530-45418 that inhibits prostate cancer metastasis in vitro and in vivo.

Prostate cancer is a prevalent malignancy among men globally, and androgen deprivation therapy is the conventional first-line treatment for metastatic prostate cancer. While androgen deprivation therapy is efficacious in castration-sensitive prostate cancer, it remains less effective in castration-resistant cases. Transcriptional dysregulation is a well-established hallmark of cancer, and targeting proteins involved in transcriptional regulation, such as cyclin-dependent kinase 8 (CDK8), has become an attractive therapeutic strategy. CDK8, a nuclear serine-threonine kinase, is a key component of the mediator complex and plays a critical role in transcriptional regulation. Recent studies have highlighted the promising role of CDK8 as a target in the treatment of metastatic prostate cancer. Our study assessed the efficacy of a novel CDK8 inhibitor, E966-0530-45418, which exhibited potent CDK8 inhibition (IC50 of 129 nM) and high CDK8 selectivity. Treatment with E966-0530-45418 significantly inhibited prostate cancer cell migration and epithelial-to-mesenchymal transition (EMT) at both the RNA and protein levels. Further mechanistic analysis indicated that E966-0530-45418 suppresses prostate cancer metastasis by decreasing CDK8 activity and inhibiting TGF-ß1-mediated Smad3/RNA polymerase II linker phosphorylation and Akt/GSK3ß/ß-catenin signaling. The results in animal model also showed that E966-0530-45418 exhibited anti-metastatic properties in vivo. Our study demonstrated that E966-0530-45418 has great therapeutic potential in the treatment of metastatic prostate cancer.

Design, synthesis, and biological evaluation of indolin-2-one derivatives as novel cyclin-dependent protein kinase 8 (CDK8) inhibitors.

Cyclin-dependent protein kinase 8 (CDK8) plays important roles in regulating fibrotic growth factors and inflammatory signaling pathways. Long-term chronic inflammation of the lungs can lead to idiopathic pulmonary fibrosis (IPF). Abnormal alveolar epithelial regeneration leads to the release of various fibrotic growth factors and the activation of inflammatory cells. CDK8 regulates profibrotic cytokines broadly implicated in the pathogenesis of fibrosis. Therefore, inhibition of CDK8 is considered a promising strategy for treating IPF. Here, CDK8 inhibitors were designed and optimized using a fragment-based drug design strategy. Testing results revealed that 71% of the synthesized compounds inhibited CDK8 activity better than the original compound E966-0530. Of these compounds, compound 4k exhibited the strongest CDK8 enzyme-inhibiting activity (IC50 =129 nM). Notably, it displayed a 13-fold increase in potency when compared to E966-0530. Experiments on toxicity and inhibition of epithelial-mesenchymal transition (EMT) protein expressions showed that compound 4k can inhibit EMT protein expressions, but with no significant cytotoxicity for alveolar epithelial cells. Compound 4k showed a potent inhibitory effect in cell migration assays. Furthermore, compound 4k significantly inhibited the phosphorylation of p-Smad3 and RNA Pol II, which are critical mediators in the fibrotic response signaling pathway. Compound 4k remarkably reduced TGF-ß1-induced oxidative stress. The above results reveal optimized CDK8 inhibitors with potential use for IPF therapeutic treatment.

Ibuprofen treatment ameliorates memory deficits in rats with collagen-induced arthritis by normalizing aberrant MAPK/NF-κB and glutamatergic pathways.

Many studies have indicated that the risk of cognitive impairment is higher in patients with rheumatoid arthritis (RA). Additionally, patients with RA may have a lower incidence of cognitive impairment with long-term use of ibuprofen. This study was aimed at investigating the impacts of RA on memory function and the mechanisms that ibuprofen may exhibit to improve memory function in rats with collagen-induced arthritis (CIA). Ibuprofen (30 mg/kg) was given twice daily to CIA rats for two weeks starting from Day 18 following the first immunization. Memory function was measured by the Morris water maze (MWM) test and long-term potentiation (LTP). The proinflammatory cytokine levels and downstream signaling pathways, including mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB), were examined. Furthermore, the glutamatergic system, including glutamate transporters/receptors and brain extracellular levels of glutamate, was investigated. The results showed that the impaired learning memory in CIA rats, examined by the MWM test and LTP, can be ameliorated by ibuprofen treatment. Along with the improvement in memory deficits, ibuprofen attenuated both neuroinflammation and the associated elevated levels of phosphorylated p38, JNK, and p65 in the hippocampus of CIA rats. In addition, the decreased excitatory amino acid transporter 2 level, the increased extracellular glutamate, and the upregulated hippocampal NMDA receptor 2B of CIA rats were all normalized by ibuprofen treatment. These findings suggest that the effect of ibuprofen on the memory improvement in CIA rats is associated with the normalization of the activated MAPK and NF-κB pathways and the aberrant glutamatergic system.

O-methylated flavonol as a multi-kinase inhibitor of leukemogenic kinases exhibits a potential treatment for acute myeloid leukemia.

BACKGROUND: Acute myeloid leukemia (AML) is a heterogeneous disease with poor overall survival characterized by various genetic changes. The continuous activation of oncogenic pathways leads to the development of drug resistance and limits current therapeutic efficacy. Therefore, a multi-targeting inhibitor may overcome drug resistance observed in AML treatment. Recently, groups of flavonoids, such as flavones and flavonols, have been shown to inhibit a variety of kinase activities, which provides potential opportunities for further anticancer applications. PURPOSE: In this study, we evaluated the anticancer effects of flavonoid compounds collected from our in-house library and investigated their potential anticancer mechanisms by targeting multiple kinases for inhibition in AML cells. METHODS: The cytotoxic effect of the compounds was detected by cell viability assays. The kinase inhibitory activity of the selected compound was detected by kinase-based and cell-based assays. The binding conformation and interactions were investigated by molecular docking analysis. Flow cytometry was used to evaluate the cell cycle distribution and cell apoptosis. The protein and gene expression were estimated by western blotting and qPCR, respectively. RESULTS: In this study, an O-methylated flavonol (compound 11) was found to possess remarkable cytotoxic activity against AML cells compared to treatment in other cancer cell lines. The compound was demonstrated to act against multiple kinases, which play critical roles in survival signaling in AML, including FLT3, MNK2, RSK, DYRK2 and JAK2 with IC50 values of 1 - 2 µM. Compared to our previous flavonoid compounds, which only showed inhibitions against MNKs or FLT3, compound 11 exhibited multiple kinase inhibitory abilities. Moreover, compound 11 showed effectiveness in inhibiting internal tandem duplications of FLT3 (FLT3-ITDs), which accounts for 25% of AML cases. The interactions between compound 11 and targeted kinases were investigated by molecular docking analysis. Mechanically, compound 11 caused dose-dependent accumulation of leukemic cells at the G0/G1 phase and followed by the cells undergoing apoptosis. CONCLUSION: O-methylated flavonol, compound 11, can target multiple kinases, which may provide potential opportunities for the development of novel therapeutics for drug-resistant AMLs. This work provides a good starting point for further compound optimization.

Identification and analysis of a selective DYRK1A inhibitor.

The dysregulation of DYRK1A is implicated in many diseases such as cancer, diabetes, and neurodegenerative diseases. Alzheimer's disease is one of the most common neurodegenerative disease and has elevated interest in DYRK1A research. Overexpression of DYRK1A has been linked to the formation of tau aggregates. Currently, an effective therapeutic treatment that targets DYRK1A is lacking. A specific small-molecule inhibitor would further our understanding of the physiological role of DYRK1A in neurodegenerative diseases and could be presented as a possible therapeutic option. In this study, we identified pharmacological interactions within the DYRK1A active site and performed a structure-based virtual screening approach to identify a selective small-molecule inhibitor. Several compounds were selected in silico for enzymatic and cellular assays, yielding a novel inhibitor. A structure-activity relationship analysis was performed to identify areas of interactions for the compounds selected in this study. When tested in vitro, reduction of DYRK1A dependent phosphorylation of tau was observed for active compounds. The active compounds also improved tau turbidity, suggesting that these compounds could alleviate aberrant tau aggregation. Testing the active compound against a panel of kinases across the kinome revealed greater selectivity towards DYRK1A. Our study demonstrates a serviceable protocol that identified a novel and selective DYRK1A inhibitor with potential for further study in tau-related pathologies.

Structure-based virtual screening and biological evaluation of novel small-molecule BTK inhibitors.

Bruton tyrosine kinase (BTK) is linked to multiple signalling pathways that regulate cellular survival, activation, and proliferation. A covalent BTK inhibitor has shown favourable outcomes for treating B cell malignant leukaemia. However, covalent inhibitors require a high reactive warhead that may contribute to unexpected toxicity, poor selectivity, or reduced effectiveness in solid tumours. Herein, we report the identification of a novel noncovalent BTK inhibitor. The binding interactions (i.e. interactions from known BTK inhibitors) for the BTK binding site were identified and incorporated into a structure-based virtual screening (SBVS). Top-rank compounds were selected and testing revealed a BTK inhibitor with >50% inhibition at 10 µM concentration. Examining analogues revealed further BTK inhibitors. When tested across solid tumour cell lines, one inhibitor showed favourable inhibitory activity, suggesting its potential for targeting BTK malignant tumours. This inhibitor could serve as a basis for developing an effective BTK inhibitor targeting solid cancers.

Discovery of a novel cyclin-dependent kinase 8 inhibitor with an oxindole core for anti-inflammatory treatment.

Chronic inflammation is an underlying cause in a number of diseases. Cyclin-dependent kinase 8 (CDK8) has been implicated as an inflammatory mediator, indicating its potential as an anti-inflammatory target. Herein, we performed structure-based virtual screening (SBVS) to identify novel CDK8 inhibitors. The pharmacological interactions for CDK8 were identified and incorporated into a SBVS protocol. Selected compounds were tested in enzymatic assays, and one compound was confirmed to be a CDK8 inhibitor with a 50% inhibitory concentration (IC50) value of 1684.4 nM. Comparing structural analogs identified a compound, F059-1017, with greater potency (IC50 558.1 nM). When tested in cell lines, the compounds displayed low cytotoxicity. Cellular assays revealed that the identified CDK8 inhibitors can reduce phosphorylation and expression of signaling mediators associated with inflammation. In addition, results of kinase profiling showed that compound F059-1017 is selective towards CDK8. These findings suggest that the new inhibitors have great potential as lead compounds for developing novel anti-inflammatory therapeutics.

Neuroprotective Studies of Evodiamine in an Okadaic Acid-Induced Neurotoxicity.

BACKGROUND: Alzheimer's disease (AD) is the most common neurodegenerative disease, and it manifests as progressive memory loss and cognitive decline. However, there are no effective therapies for AD, which is an urgent problem to solve. Evodiamine, one of the main bioactive ingredients of Evodia rutaecarpa, has been reported to ameliorate blood-brain barrier (BBB) permeability and improve cognitive impairment in ischemia and AD mouse models. However, whether evodiamine alleviates tauopathy remains unclear. This study aimed to examine whether evodiamine ameliorates tau phosphorylation and cognitive deficits in AD models. METHODS: A protein phosphatase 2A inhibitor, okadaic acid (OA), was used to induce tau phosphorylation to mimic AD-like models in neuronal cells. Protein expression and cell apoptosis were detected using Western blotting and flow cytometry, respectively. Spatial memory/cognition was assessed using water maze, passive avoidance tests, and magnetic resonance imaging assay in OA-induced mice models, and brain slices were evaluated further by immunohistochemistry. RESULTS: The results showed that evodiamine significantly reduced the expression of phosphor-tau, and further decreased tau aggregation and neuronal cell death in response to OA treatment. This inhibition was found to be via the inhibition of glycogen synthase kinase 3ß, cyclin-dependent kinase 5, and mitogen-activated protein kinase pathways. In vivo results indicated that evodiamine treatment ameliorated learning and memory impairments in mice, whereas Western blotting and immunohistochemical analysis of the mouse brain also confirmed the neuroprotective effects of evodiamine. CONCLUSIONS: Evodiamine can decrease the neurotoxicity of tau aggregation and exhibit a neuroprotective effect. Our results demonstrate that evodiamine has a therapeutic potential for AD treatment.

A novel dual HDAC and HSP90 inhibitor, MPT0G449, downregulates oncogenic pathways in human acute leukemia in vitro and in vivo.

Acute leukemia is a highly heterogeneous disease; therefore, combination therapy is commonly used for patient treatment. Drug-drug interaction is a major concern of combined therapy; hence, dual/multi-target inhibitors have become a dominant approach for cancer drug development. HDACs and HSP90 are involved in the activation of various oncogenic signaling pathways, including PI3K/AKT/mTOR, JAK/STAT, and RAF/MEK/ERK, which are also highly enriched in acute leukemia gene expression profiles. Therefore, we suggest that dual HDAC and HSP90 inhibitors could represent a novel therapeutic approach for acute leukemia. MPT0G449 is a dual effect inhibitor, and it showed cytotoxic effectiveness in acute leukemia cells. Molecular docking analysis indicated that MPT0G449 possessed dual HDAC and HSP90 inhibitory abilities. Furthermore, MPT0G449 induced G2 arrest and caspase-mediated cell apoptosis in acute leukemia cells. The oncogenic signaling molecules AKT, mTOR, STAT3, STAT5, MEK, and ERK were significantly downregulated after MPT0G449 treatment in HL-60 and MOLT-4 cells. In vivo xenograft models confirmed the antitumor activity and showed the upregulation of acetyl-histone H3 and HSP70, biomarkers of pan-HDAC and HSP90 inhibition, with MPT0G449 treatment. These findings suggest that the dual inhibition of HDAC and HSP90 can suppress the expression of oncogenic pathways in acute leukemia, and MPT0G449 represents a novel therapeutic for anticancer treatment.

Identification of a dual TAOK1 and MAP4K5 inhibitor using a structure-based virtual screening approach.

The STE20 kinase family is a complex signalling cascade that regulates cytoskeletal organisation and modulates the stress response. This signalling cascade includes various kinase mediators, such as TAOK1 and MAP4K5. The dysregulation of the STE20 kinase pathway is linked with cancer malignancy. A small-molecule inhibitor targeting the STE20 kinase pathway has therapeutic potential. In this study, a structure-based virtual screening (SBVS) approach was used to identify potential dual TAOK1 and MAP4K5 inhibitors. Enzymatic assays confirmed three potential dual inhibitors (>50% inhibition) from our virtual screening, and analysis of the TAOK1 and MAP4K5 binding sites indicated common interactions for dual inhibition. Compound 1 revealed potent inhibition of colorectal and lung cancer cell lines. Furthermore, compound 1 arrested cancer cells in the G0/G1 phase, which suggests the induction of apoptosis. Altogether, we show that the STE20 signalling mediators TAOK1 and MAP4K5 are promising targets for drug research.

Anti-Inflammatory and Tau Phosphorylation-Inhibitory Effects of Eupatin.

Alzheimer's disease (AD), which is among the most prevalent neurodegenerative diseases, manifests as increasing memory loss and cognitive decline. Tau phosphorylation and aggregation are strongly linked to neurodegeneration, as well as associated with chronic neuroinflammatory processes. The anti-inflammation effects of natural products have led to wide recognition of their potential for use in treating and preventing AD. This study investigated whether eupatin, a polymethoxyflavonoid found in Artemisia species, has inhibitory effects on neuroinflammation and tau phosphorylation. We treated mouse macrophages and microglia cells with lipopolysaccharides (LPSs) to activate inflammatory signals, and we treated neuronal cells with a protein phosphatase 2A inhibitor, okadaic acid (OA), or transfection with pRK5-EGFP-Tau P301L plasmid to induce tau phosphorylation. The results indicated that eupatin significantly reduced the LPS-induced protein expression and phosphorylation of p65 and inducible nitric oxide synthase as well as downstream products interleukin 6 and nitrite, respectively. Furthermore, eupatin markedly inhibited the expression of phospho-tau in response to OA treatment and plasmid transfection. We discovered that this inhibition was achieved through the inhibition of glycogen synthase kinase 3ß (GSK3ß), and molecular docking results suggested that eupatin can sufficiently bind to the GSK3ß active site. Our results demonstrate that eupatin has neuroprotective effects, making it suitable for AD treatment.

4-Substituted 2-amino-3,4-dihydroquinazolines with a 3-hairpin turn side chain as novel inhibitors of BACE-1.

Herein, we report the identification, design, and synthesis of a series of 4-substituted 2-amino-3,4-dihydroquinazolines with hairpin turn side chains as novel inhibitors of BACE-1. The dihydroquinazoline derivatives were rationally designed by modifying the amide group and relocating the α -hydrophobic substituent on the hairpin turn side chain of lead compound 2 to the C4-position on the 3,4-dihydroquinazoline scaffold to facilitate interactions with the S1, S2 and S1' subsites of BACE-1. Among these derivatives, two compounds exhibited potent BACE-1 inhibitory activity: 4-methyl-substituted (22a, BACE-1 CFA IC50 = 0.38 µM; BACE-1 WCA IC50 = 0.14 µM) and 4-cyclohexylmethyl-substituted (22b, BACE-1 CFA IC50 = 0.49 µM; BACE-1 WCA IC50 = 0.14 µM) 2-amino-3,4-dihydroquinazoline, each bearing a side chain of N-cyclohexyl-N-((1-methyl-1H-pyrazol-4-yl)methyl amide. The results suggest that the structural modifications maintain the hairpin turn topology similar to that of compound 2 and provide an additional interaction with the S2 subsite.

Moscatilin Ameliorates Tau Phosphorylation and Cognitive Deficits in Alzheimer's Disease Models.

Alzheimer's disease (AD) is a neurodegenerative disease and a common cause of dementia, manifesting as progressive memory loss and cognitive decline. Moscatilin, which reportedly reduces fever and is anti-inflammatory, is the bibenzyl extract from Dendrobium loddigesii. This study aimed to examine whether moscatilin ameliorates tau phosphorylation and cognitive deficits in AD models. The first in vitro AD-like model was developed by cotransfection with the pCAX FLAG APP and pRK5-EGFP-Tau P301L plasmids, resulting in the neuronal overexpression of amyloid precursor protein (APP) and tau P301L, a tauopathy-associated tau. The second model was developed by using okadaic acid to induce tau protein phosphorylation. Spatial memory/cognition was assessed using water maze and elevated plus maze tests in a scopolamine-induced mouse model, and brain slices were evaluated further by immunohistochemistry (IHC). Moscatilin significantly reduced phospho-tau expression in a concentration-dependent manner, decreased tau aggregation, and reduced apoptosis. These results indicated that moscatilin reversed tauopathy through GSK3ß inactivation and inhibition of oxidative stress. Furthermore, in vivo data demonstrated that moscatilin ameliorated learning and memory impairments in mice, while IHC and Western blot results of the mouse brain confirmed that moscatilin decreased tau phosphorylation. Our novel findings suggest that moscatilin has neuroprotective effects against AD.

MPT0G413, A Novel HDAC6-Selective Inhibitor, and Bortezomib Synergistically Exert Anti-tumor Activity in Multiple Myeloma Cells.

In multiple myeloma (MM), homeostasis is largely maintained by misfolded protein clearance via the proteasomal and aggresomal pathways. Histone deacetylase 6 (HDAC6) binds polyubiquitinated proteins and dynein motors and transports this protein cargo to the aggresome for further degradation. Accordingly, a combination of an HDAC6 inhibitor and bortezomib (BTZ) could increase ubiquitinated protein accumulation, leading to further apoptosis. Here we evaluated the anti-MM activity of MPT0G413, a novel specific HDAC6 inhibitor, using in vitro and in vivo models. MPT0G413 treatment more significantly inhibited cell growth in MM cells than in normal bone marrow cells. Furthermore, the combination of MPT0G413 and BTZ enhanced polyubiquitinated protein accumulation and synergistically reduced MM viability, increased caspase-3, caspase-8, caspase-9 levels, and cleaved poly (ADP) ribosome polymerase and also inhibited adherence of MM cells to bone marrow stromal cells (BMSC) and reduced VEGF and IL-6 levels and cell growth in a co-culture system. The combination treatment disturbed the bone marrow microenvironment and induced synergic, caspase-dependent apoptosis. Xenograft tumor growth significantly decreased in combination-treated SCID mice. In conclusion, MPT0G413 and BTZ synergistically inhibit MM viability, providing a framework for the clinical evaluation of combined therapies for MM.

Anti-metastatic activity of MPT0G211, a novel HDAC6 inhibitor, in human breast cancer cells in vitro and in vivo.

Triple-negative breast cancer (TNBC) is associated with an increased risk of metastasis and a poor prognosis. The invasive ability of TNBC relies on actin reorganization and is regulated by histone deacetylase 6 (HDAC6). The present study aimed to examine the effect of MPT0G211, a novel HDAC6 inhibitor, on cell migration and microtubule association in both in vitro and in vivo models of TNBC. Here MPT0G211 more selectively and potently targeted and inhibited HDAC6, compared with tubastatin A, another selective HDAC6 inhibitor. In vitro, MPT0G211 decreased the migration of the TNBC cell line MDA-MB-231, particularly when administered together with paclitaxel, and increased heat shock protein 90 (Hsp90) acetylation, leading to the dissociation of Hsp90 from aurora-A and proteasomal degradation. Furthermore, MPT0G211 significantly disrupted F-actin polymerization by increasing cortactin acetylation and downregulating slingshot protein phosphatase 1 (SSH1) and active cofilin expression. In vivo, MPT0G211 treatment significantly ameliorated TNBC metastasis. In conclusion, our results demonstrate that MPT0G211 reduces TNBC cell motility by promoting cortactin acetylation and aurora-A degradation, and inhibiting the cofilin-F-actin pathway via HDAC6 activity attenuation. MPT0G211 therefore demonstrates therapeutic potential for invasive TNBC.

The anticancer effects of MPT0G211, a novel HDAC6 inhibitor, combined with chemotherapeutic agents in human acute leukemia cells.

BACKGROUND: There are some limitations of standard chemotherapy for acute leukemia. Vincristine and doxorubicin are commonly used for acute leukemia, but they may induce serious side effects such as cardiomyopathy and neurotoxicity. Furthermore, chemotherapy resistance occurs more and more frequently. Therefore, effective treatment strategies are needed. Histone deacetylase 6 inhibition is considered as a potential therapeutic strategy for acute leukemia, since it is observed that HDAC6 is overexpressed in acute leukemia and regulates tumor survival. Combination therapy for cancer is used to minimize adverse drug effects, reduce drug dosage, enhance efficacy, and prevent drug resistance. In order to improve efficacy of chemotherapy agents of acute leukemia, this study will investigate the effects of combination MPT0G211, a novel histone deacetylase 6 inhibitor, with doxorubicin or vincristine on human acute leukemia cells. RESULTS: MPT0G211 combined with doxorubicin induces DNA damage response on human acute myeloid leukemia cells. MPT0G211 can additionally increase Ku70 acetylation and release BAX to mitochondria. Ectopic expression of HDAC6 successively reversed the apoptosis triggered by the combined treatment. Moreover, co-treatment of MPT0G211 and vincristine may alter microtubule dynamics, triggering acute lymphoblastic leukemia cells arrest in mitotic phase followed by induction of the apoptotic pathway. Finally, MPT0G211 plus doxorubicin or vincristine can significantly improve the tumor growth delay in a tumor xenograft model. CONCLUSIONS: Collectively, our data highlighted that MPT0G211 in combination with chemotherapy drugs has significant anticancer activity, suggesting a novel strategy for the treatment of acute leukemia.

5-Aroylindoles Act as Selective Histone Deacetylase 6 Inhibitors Ameliorating Alzheimer's Disease Phenotypes.

This paper reports the development of a series of 5-aroylindolyl-substituted hydroxamic acids. N-Hydroxy-4-((5-(4-methoxybenzoyl)-1 H-indol-1-yl)methyl)benzamide (6) has potent inhibitory selectivity against histone deacetylase 6 (HDAC6) with an IC50 value of 3.92 nM. It decreases not only the level of phosphorylation of tau proteins but also the aggregation of tau proteins. Compound 6 also shows neuroprotective activity by triggering ubiquitination. In animal models, compound 6 is able to ameliorate the impaired learning and memory, and it crosses the blood-brain barrier after oral administration. Compound 6 can be developed as a potential treatment for Alzheimer's disease in the future.

The novel histone de acetylase 6 inhibitor, MPT0G211, ameliorates tau phosphorylation and cognitive deficits in an Alzheimer's disease model.

Alzheimer's disease (AD) is a dreadful neurodegenerative disease that leads to severe impairment of cognitive function, leading to a drastic decline in the quality of life. The primary pathological features of AD include senile plaques (SPs) and intracellular neurofibrillary tangles (NFTs), comprising aggregated amyloid ß (Aß) and hyperphosphorylated tau protein, respectively, in the hippocampus of AD patients. Histone deacetylase 6 (HDAC6) is a key enzyme in this neurodegenerative disease, in particular, as it relates to tau hyperphosphorylation. This study aimed to investigate the protective effects and mechanism of the novel HDAC6 inhibitor, MPT0G211, using an AD model. Our results indicated that MPT0G211 significantly reduced tau phosphorylation and aggregation, the processes highly correlated with the formation of NFTs. This HDAC6 inhibitory activity resulted in an increase in acetylated Hsp90, which decreased Hsp90 and HDAC6 binding, causing ubiquitination of phosphorylated tau proteins. In addition, a significant increase of phospho-glycogen synthase kinase-3ß (phospho-GSK3ß) on Ser9 (the inactive form) through Akt phosphorylation was associated with the inhibition of phospho-tau Ser396 in response to MPT0G211 treatment. In AD in vivo models, MPT0G211 appeared to ameliorate learning and memory impairment in animals. Furthermore, MPT0G211 treatment reduced the amount of phosphorylated tau in the hippocampal CA1 region. In summary, MPT0G211 treatment appears to be a promising strategy for improving the AD phenotypes, including tau hyperphosphorylation and aggregation, neurodegeneration, and learning and memory impairment, making it a valuable agent for further investigation.