Development of novel adenosine monophosphate-activated protein kinase activators

Identification of AdipoRon analogues as novel activators of AMPK for the treatment of type 2 diabetes

The activation of AMPK has emerged as a promising therapeutic approach for the treatment of metabolic diseases. AdipoRon, an agonist of the adiponectin receptor, has been identified as a compound capable of activating AMPK via the adiponectin receptor. To identify novel AdipoRon analogues with AMPK activation potential, a total of 17 analogues were designed, synthesized, and subjected to biological evaluation. Among these analogues, X-12 was discovered to exhibit potent activation of AMPK. In experimental studies, X-12 demonstrated dose-dependent improvements in glucose tolerance in normal mice. Furthermore, it significantly reduced fasting blood glucose levels and ameliorated insulin resistance in db/db diabetic mice. These findings highlight the therapeutic potential of X-12 as a novel class of AMPK activators for the treatment of metabolic diseases.

Design, synthesis and evaluation of tetrahydrocarbazole derivatives as potential hypoglycemic agents

Two series of tetrahydrocarbazole derivatives have been designed and synthesized based on ZG02, a promising candidate developed in our previous studies. The newly prepared compounds were screened for glucose consumption activity in HepG2 cell lines. Aza-tetrahydrocarbazole compound 12b showed the most potent hypoglycemic activity with a 45% increase in glucose consumption when compared to the solvent control, which had approximately 1.2-fold higher activity than the positive control compounds (metformin and ZG02). An investigation of the potential mechanism indicated that 12b may exhibit hypoglycemic activity via activation of the AMPK pathway. Metabolic stability assays revealed that 12b showed good stability profiles in both artificial gastrointestinal fluids and blood plasma from SD rats. An oral glucose tolerance test (OGTT) was performed and the results further confirmed that 12b was a potent hypoglycemic agent.

Activation of AMPK by OSU53 protects spinal cord neurons from oxidative stress

The present study tested the potential effect of OSU53, a novel AMPK activator, against hydrogen peroxide (H2O2)-induced spinal cord neuron damages. Treatment with OSU53 attenuated H2O2-induced death and apoptosis of primary murine spinal cord neurons. OSU53 activated AMPK signaling, which is required for its actions in spinal cord neurons. The AMPK inhibitor Compound C or AMPKα1 siRNA almost abolished OSU53-mediated neuroprotection against H2O2. On the other hand, sustained-activation of AMPK by introducing the constitutive-active AMPKα1 mimicked OSU53's actions, and protected spinal cord neurons from oxidative stress. OSU53 significantly attenuated H2O2-induced reactive oxygen species production, lipid peroxidation and DNA damages in spinal cord neurons. Additionally, OSU53 increased NADPH content and heme oxygenase-1 mRNA expression in H2O2-treated spinal cord neurons. Together, we indicate that targeted-activation of AMPK by OSU53 protects spinal cord neurons from oxidative stress.

AMP-activated protein kinase and energy balance in breast cancer

Cancer growth and metastasis depends on the availability of energy. Energy-sensing systems are critical in maintaining a balance between the energy supply and utilization of energy for tumor growth. A central regulator in this process is AMP-activated protein kinase (AMPK). In times of energy deficit, AMPK is allosterically modified by the binding of increased levels of AMP and ADP, making it a target of specific AMPK kinases (AMPKKs). AMPK signaling prompts cells to produce energy at the expense of growth and motility, opposing the actions of insulin and growth factors. Increasing AMPK activity may thus prevent the proliferation and metastasis of tumor cells. Activated AMPK also suppresses aromatase, which lowers estrogen formation and prevents breast cancer growth. Biguanides can be used to activate AMPK, but AMPK activity is modified by many different interacting factors; understanding these factors is important in order to control the abnormal growth processes that lead to breast cancer neoplasia. Fatty acids, estrogens, androgens, adipokines, and another energy sensor, sirtuin-1, alter the phosphorylation and activation of AMPK. Isoforms of AMPK differ among tissues and may serve specific functions. Targeting AMPK regulatory processes at points other than the upstream AMPKKs may provide additional approaches for prevention of breast cancer neoplasia, growth, and metastasis.

OSU53 Rescues Human OB-6 Osteoblastic Cells from Dexamethasone through Activating AMPK Signaling

Excessive dexamethasone (Dex) application causes osteoblast cell death, which could lead to osteoporosis or osteonecrosis. AMP-activated protein kinase (AMPK) activation is shown to protect osteoblasts/osteoblastic cells from Dex. In this report, we tested the potential effect of OSU53, a novel AMPK activator, in Dex-treated osteoblastic cells. We show that OSU53 activated AMPK signaling in human OB-6 osteoblastic cells. Further, Dex-induced osteoblastic OB-6 cell death and apoptosis were largely attenuated with pre-treatment with OSU53. OSU53 was more efficient than other known AMPK activators (A-769662 and Compound 13) in protecting OB-6 cells against Dex. AMPK activation is required for OSU53-induced actions in OB-6 cells. AMPKα shRNA knockdown or dominant-negative mutation (dn-AMPKα T172A) almost completely blocked OSU53-induced AMPK activation and OB-6 cell protection against Dex. Further studies showed that OSU53 increased NADPH (nicotinamide adenine dinucleotide phosphate) activity and alleviated Dex-induced oxidative stress in OB-6 cells. Such effects by OSU53 were again almost abolished with AMPKα shRNA or dn-AMPKα in OB-6 cells. Together, these results demonstrate that OSU53 protects osteoblastic cells from Dex possibly via activating AMPK-dependent signaling.

Targeting myeloid-derived suppressor cells using a novel adenosine monophosphate-activated protein kinase (AMPK) activator

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of early myeloid cells that accumulate in the blood and tumors of patients with cancer. MDSC play a critical role during tumor evasion and promote immune suppression through variety of mechanisms, such as the generation of reactive oxygen and nitrogen species (ROS and RNS) and cytokines. AMPactivated protein kinase (AMPK) is an evolutionarily conserved serine/threonine kinase that regulates energy homeostasis and metabolic stress. However, the role of AMPK in the regulation of MDSC function remains largely unexplored. This study was designed to investigate whether treatment of MDSC with OSU-53, a PPAR-inactive derivative that stimulates AMPK kinase, can modulate MDSC function. Our results demonstrate that OSU-53 treatment increases the phosphorylation of AMPK, significantly reduces nitric oxide production, inhibits MDSC migration, and reduces the levels of IL-6 in murine MDSC cell line (MSC2 cells). OSU53 treatment mitigated the immune suppressive functions of murine MDSC, promoting T-cell proliferation. Although OSU-53 had a modest effect on tumor growth in mice inoculated with EMT-6 cells, importantly, administration of OSU53 significantly (p < 0.05) reduced the levels of MDSC in the spleens and tumors. Furthermore, mouse MDSC from EMT-6 tumor-bearing mice and human MDSC isolated from melanoma patients treated with OSU-53 showed a significant reduction in the expression of immune suppressive genes iNOS and arginase. In summary, these results demonstrate a novel role of AMPK in the regulation of MDSC functions and provide a rationale of combining OSU-53 with immune checkpoint inhibitors to augment their response in cancer patients.

Oestrogen receptors interact with the α-catalytic subunit of AMP-activated protein kinase

We identified a novel interaction between the classical oestrogen receptors (ERα and ERβ) and the catalytic subunit of AMP-activated protein kinase (AMPK) in several cell types. In addition, we demonstrate that oestradiol (E2) activates AMPK through ERα and requires the upstream kinase complex liver kinase B (LKB1).

Normal and pathological stressors engage the AMP-activated protein kinase (AMPK) signalling axis to protect the cell from energetic pressures. Sex steroid hormones also play a critical role in energy metabolism and significantly modify pathological progression of cardiac disease, diabetes/obesity and cancer. AMPK is targeted by 17β-oestradiol (E2), the main circulating oestrogen, but the mechanism by which E2 activates AMPK is currently unknown. Using an oestrogen receptor α/β (ERα/β) positive (T47D) breast cancer cell line, we validated E2-dependent activation of AMPK that was mediated through ERα (not ERβ) by using three experimental strategies. A series of co-immunoprecipitation experiments showed that both ERs associated with AMPK in cancer and striated (skeletal and cardiac) muscle cells. We further demonstrated direct binding of ERs to the α-catalytic subunit of AMPK within the βγ-subunit-binding domain. Finally, both ERs interacted with the upstream liver kinase B 1 (LKB1) kinase complex, which is required for E2-dependent activation of AMPK. We conclude that E2 activates AMPK through ERα by direct interaction with the βγ-binding domain of AMPKα.

Development of Potent Adenosine Monophosphate Activated Protein Kinase (AMPK) Activators

Previously, we reported the identification of a thiazolidinedione-based adenosine monophosphate activated protein kinase (AMPK) activator, compound 1 (N-[4-({3-[(1-methylcyclohexyl)methyl]-2,4-dioxothiazolidin-5-ylidene}methyl)phenyl]-4-nitro-3-(trifluoromethyl)benzenesulfonamide), which provided a proof of concept to delineate the intricate role of AMPK in regulating oncogenic signaling pathways associated with cell proliferation and epithelial-mesenchymal transition (EMT) in cancer cells. In this study, we used 1 as a scaffold to conduct lead optimization, which generated a series of derivatives. Analysis of the antiproliferative and AMPK-activating activities of individual derivatives revealed a distinct structure-activity relationship and identified 59 (N-(3-nitrophenyl)-N'-{4-[(3-{[3,5-bis(trifluoromethyl)phenyl]methyl}-2,4-dioxothiazolidin-5-ylidene)methyl]phenyl}urea) as the optimal agent. Relative to 1, compound 59 exhibits multifold higher potency in upregulating AMPK phosphorylation in various cell lines irrespective of their liver kinase B1 (LKB1) functional status, accompanied by parallel changes in the phosphorylation/expression levels of p70S6K, Akt, Foxo3a, and EMT-associated markers. Consistent with its predicted activity against tumors with activated Akt status, orally administered 59 was efficacious in suppressing the growth of phosphatase and tensin homologue (PTEN)-null PC-3 xenograft tumors in nude mice. Together, these findings suggest that 59 has clinical value in therapeutic strategies for PTEN-negative cancer and warrants continued investigation in this regard.

A novel dual AMPK activator/mTOR inhibitor inhibits thyroid cancer cell growth

CONTEXT

Activated AMP protein kinase (AMPK) is a key regulator of intracellular energy homeostasis and may also function as a tumor suppressor by inhibiting cell growth through suppression of mammalian target of rapamycin (mTOR)/p70S6K signaling. AMPK activating agents, such as metformin and 5-aminoimidazole-4-carboxamide-ribonucleoside, have been demonstrated to inhibit thyroid cancer cell growth in in vitro and in vivo models. OSU-53, a recently developed AMPK activator, was previously shown to exhibit both in vitro and in vivo antitumor activity against aggressive breast cancer cell lines and their xenografts in nude mice.

OBJECTIVE

The objective of the study was to assess the in vitro effects of OSU-53 treatment in a panel of thyroid cancer cells.

DESIGN

Experiments were performed to determine the effects of OSU-53 on cell growth, oncogenic signaling, apoptosis, autophagy, and cell rescue after selective knockdown of AMPK.

RESULTS

OSU-53 inhibited in vitro cell growth of all seven thyroid cancer cells tested and induced activation of AMPK. Cell lines with activating mutations in RAS or BRAF, compared with cells with phosphatase and tensin homolog deleted from chromosome 10 null and RET/papillary thyroid carcinoma mutations, were more sensitive to drug treatment and demonstrated a more robust AMPK activation, inhibition of mTOR signaling, and autophagy stimulation. After selective knockdown of AMPK, cell rescue from OSU-53 treatment was not observed. We demonstrated an off-target effect of direct mTOR inhibition by OSU-53. Increased autophagy was observed in cells with activation RAS or BRAF mutations.

CONCLUSIONS

OSU-53, a novel dual-AMPK activator/mTOR inhibitor, effectively inhibits growth in a variety of thyroid cancer cell lines and is most potent in cells with activating mutations in RAS or BRAF.

AMPK as a potential anticancer target - friend or foe?

Adenosine monophosphate-activated protein kinase (AMPK) is a key player in maintaining energy homeostasis in response to metabolic stress. Beyond diabetes and metabolic syndrome, there is a growing interest in the therapeutic exploitation of the AMPK pathway in cancer treatment in light of its unique ability to regulate cancer cell proliferation through the reprogramming of cell metabolism. Although many studies support the tumor-suppressive role of AMPK, emerging evidence suggests that the metabolic checkpoint function of AMPK might be overridden by stress or oncogenic signals so that tumor cells use AMPK activation as a survival strategy to gain growth advantage. These findings underscore the complexity in the cellular function of AMPK in maintaining energy homeostasis under physiological versus pathological conditions. Thus, this review aims to provide an overview of recent findings on the functional interplay of AMPK with different cell metabolic and signaling effectors, particularly histone deacetylases, in mediating downstream tumor suppressive or promoting mechanisms in different cell systems. Although AMPK activation inhibits tumor growth by targeting multiple signaling pathways relevant to tumorigenesis, under certain cellular contexts or certain stages of tumor development, AMPK might act as a protective response to metabolic stresses, such as nutrient deprivation, low oxygen, and low pH, or as downstream effectors of oncogenic proteins, including androgen receptor, hypoxia-inducible factor-1α, c-Src, and MYC. Thus, investigations to define at which stage(s) of tumorigenesis and cancer progression or for which genetic aberrations AMPK inhibition might represent a more relevant strategy than AMPK activation for cancer treatment are clearly warranted.

Optimization of the transfection of human THP-1 macrophages by application of Nunc UpCell technology

We have established an electroporation protocol for transfection of premature adherent human THP-1 macrophages using Lonza Nucleofector technology. For efficient electroporation, detachment of adherent cells is necessary. We tested the Nunc UpCell product line of Thermo Fisher Scientific, which achieves detachment by a change of ambient temperature, as an alternative to enzymatic detachment. Here we present data verifying proper cell morphology and vitality and high transfection efficiency for macrophages cultured on UpCell plates. Appropriate macrophage behavior was confirmed by measuring markers of macrophage differentiation and polarization by reverse transcription quantitative polymerase chain reaction (RT-qPCR). In conclusion, Nunc UpCell materials are a viable alternative to enzymatic detachment.

Berberine inhibits the metastatic ability of prostate cancer cells by suppressing epithelial-to-mesenchymal transition (EMT)-associated genes with predictive and prognostic relevance

BACKGROUND

Over 70% of cancer metastasis from prostate cancer develops bone metastases that are not sensitive to hormonal therapy, radiation therapy, or chemotherapy. The epithelial-to-mesenchymal transition (EMT) genetic program is implicated as a significant contributor to prostate cancer progression. As such, targeting the EMT represents an important therapeutic strategy for preventing or treating prostate cancer metastasis. Berberine is a natural alkaloid with significant antitumor activities against many types of cancer cells. In this study, we investigated the molecular mechanism by which berberine represses the metastatic potential of prostate cancer.

METHODS

The effects of berberine on cell migration and invasion were determined by transwell migration assay and Matrigel invasion assay. Expressions of EMT-related genes were determined by an EMT PCR Array and a quantitative RT-PCR. The prognostic relevance of berberine's modulation of EMT-related genes in prostate cancer was evaluated using Kaplan-Meier survival analysis.

RESULTS

Berberine exerted inhibitory effects on the migratory and invasive abilities of highly metastatic prostate cancer cells. These inhibitory effects of berberine resulted in significant repression of a panel of mesenchymal genes that regulate the developmental EMT. Among EMT-related genes downregulated by berberine, high BMP7, NODAL and Snail gene expressions of metastatic prostate cancer tissues were associated with shorter survival of prostate cancer patients and provide potential therapeutic interventions.

CONCLUSIONS

We concluded that berberine should be developed as a pharmacological agent for use in combination with other anticancer drug for treating metastatic prostate cancer.

Perivascular fat, AMP-activated protein kinase and vascular diseases

Perivascular adipose tissue (PVAT) is an active endocrine and paracrine organ that modulates vascular function, with implications for the pathophysiology of cardiovascular disease (CVD). Adipocytes and stromal cells contained within PVAT produce mediators (adipokines, cytokines, reactive oxygen species and gaseous compounds) with a range of paracrine effects modulating vascular smooth muscle cell contraction, proliferation and migration. However, the modulatory effect of PVAT on the vascular system in diseases, such as obesity, hypertension and atherosclerosis, remains poorly characterized. AMP-activated protein kinase (AMPK) regulates adipocyte metabolism, adipose biology and vascular function, and hence may be a potential therapeutic target for metabolic disorders such as type 2 diabetes mellitus (T2DM) and the vascular complications associated with obesity and T2DM. The role of AMPK in PVAT or the actions of PVAT have yet to be established, however. Activation of AMPK by pharmacological agents, such as metformin and thiazolidinediones, may modulate the activity of PVAT surrounding blood vessels and thereby contribute to their beneficial effect in cardiometabolic diseases. This review will provide a current perspective on how PVAT may influence vascular function via AMPK. We will also attempt to demonstrate how modulating AMPK activity using pharmacological agents could be exploited therapeutically to treat cardiometabolic diseases.

Prospects on strategies for therapeutically targeting oncogenic regulatory factors by small-molecule agents

Although the Human Genome Project has raised much hope for the identification of druggable genetic targets for cancer and other diseases, this genetic target-based approach has not improved productivity in drug discovery over the traditional approach. Analyses of known human target proteins of currently marketed drugs reveal that these drugs target only a limited number of proteins as compared to the whole proteome. In contrast to genome-based targets, mechanistic targets are derived from empirical research, at cellular or molecular levels, in disease models and/or in patients, thereby enabling the exploration of a greater number of druggable targets beyond the genome and epigenome. The paradigm shift has made a tremendous headway in developing new therapeutic agents targeting different clinically relevant mechanisms/pathways in cancer cells. In this Prospects article, we provide an overview of potential drug targets related to the following four emerging areas: (1) tumor metabolism (the Warburg effect), (2) dysregulated protein turnover (E3 ubiquitin ligases), (3) protein-protein interactions, and (4) unique DNA high-order structures and protein-DNA interactions. Nonetheless, considering the genetic and phenotypic heterogeneities that characterize cancer cells, the development of drug resistance in cancer cells by adapting signaling circuitry to take advantage of redundant pathways or feedback/crosstalk systems is possible. This "phenotypic adaptation" underlies the rationale of using therapeutic combinations of these targeted agents with cytotoxic drugs.

Highly efficient transfection of human THP-1 macrophages by nucleofection

Macrophages, as key players of the innate immune response, are at the focus of research dealing with tissue homeostasis or various pathologies. Transfection with siRNA and plasmid DNA is an efficient tool for studying their function, but transfection of macrophages is not a trivial matter. Although many different approaches for transfection of eukaryotic cells are available, only few allow reliable and efficient transfection of macrophages, but reduced cell vitality and severely altered cell behavior like diminished capability for differentiation or polarization are frequently observed. Therefore a transfection protocol is required that is capable of transferring siRNA and plasmid DNA into macrophages without causing serious side-effects thus allowing the investigation of the effect of the siRNA or plasmid in the context of normal cell behavior. The protocol presented here provides a method for reliably and efficiently transfecting human THP-1 macrophages and monocytes with high cell vitality, high transfection efficiency, and minimal effects on cell behavior. This approach is based on Nucleofection and the protocol has been optimized to maintain maximum capability for cell activation after transfection. The protocol is adequate for adherent cells after detachment as well as cells in suspension, and can be used for small to medium sample numbers. Thus, the method presented is useful for investigating gene regulatory effects during macrophage differentiation and polarization. Apart from presenting results characterizing macrophages transfected according to this protocol in comparison to an alternative chemical method, the impact of cell culture medium selection after transfection on cell behavior is also discussed. The presented data indicate the importance of validating the selection for different experimental settings.

Small molecule adenosine 5'-monophosphate activated protein kinase (AMPK) modulators and human diseases

Adenosine 5'-monophosphate activated protein kinase (AMPK) is a master sensor of cellular energy status that plays a key role in the regulation of whole-body energy homeostasis. AMPK is a serine/threonine kinase that is activated by upstream kinases LKB1, CaMKKβ, and Tak1, among others. AMPK exists as αβγ trimeric complexes that are allosterically regulated by AMP, ADP, and ATP. Dysregulation of AMPK has been implicated in a number of metabolic diseases including type 2 diabetes mellitus and obesity. Recent studies have associated roles of AMPK with the development of cancer and neurological disorders, making it a potential therapeutic target to treat human diseases. This review focuses on the structure and function of AMPK, its role in human diseases, and its direct substrates and provides a brief synopsis of key AMPK modulators and their relevance in human diseases.

Energy restriction mimetic agents to target cancer cells: comparison between 2-deoxyglucose and thiazolidinediones

The use of energy restriction mimetic agents (ERMAs) to selectively target cancer cells addicted to glycolysis could be a promising therapeutic approach. Thiazolidinediones (TZDs) are synthetic agonists of the nuclear receptor peroxisome proliferator-activated receptor (PPAR)γ that were developed to treat type II diabetes. These compounds also display anticancer effects which appear mainly to be independent of their PPARγ agonist activity but the molecular mechanisms involved in the anticancer action are not yet well understood. Results obtained on ciglitazone derivatives, mainly in prostate cancer cell models, suggest that these compounds could act as ERMAs. In the present paper, we introduce how compounds like 2-deoxyglucose target the Warburg effect and then we discuss the possibility that the PPARγ-independent effects of various TZD could result from their action as ERMAs.

AMPK reverses the mesenchymal phenotype of cancer cells by targeting the Akt-MDM2-Foxo3a signaling axis

In cancer cells, the epithelial-mesenchymal transition (EMT) confers the ability to invade basement membranes and metastasize to distant sites, establishing it as an appealing target for therapeutic intervention. Here, we report a novel function of the master metabolic kinase AMPK in suppressing EMT by modulating the Akt-MDM2-Foxo3 signaling axis. This mechanistic link was supported by the effects of siRNA-mediated knockdown and pharmacologic activation of AMPK on epithelial and mesenchymal markers in established breast and prostate cancer cells. Exposure of cells to OSU-53, a novel allosteric AMPK activator, as well as metformin and AICAR, was sufficient to reverse their mesenchymal phenotype. These effects were abrogated by AMPK silencing. Phenotypic changes were mediated by Foxo3a activation, insofar as silencing or overexpressing Foxo3a mimicked the effects of AMPK silencing or OSU-53 treatment on EMT, respectively. Mechanistically, Foxo3a activation led to the transactivation of the E-cadherin gene and repression of genes encoding EMT-inducing transcription factors. OSU-53 activated Foxo3a through two Akt-dependent pathways, one at the level of nuclear localization by blocking Akt- and IKKβ-mediated phosphorylation, and a second at the level of protein stabilization via cytoplasmic sequestration of MDM2, an E3 ligase responsible for Foxo3a degradation. The suppressive effects of OSU-53 on EMT had therapeutic implications illustrated by its ability to block invasive phenotypes in vitro and metastatic properties in vivo. Overall, our work illuminates a mechanism of EMT regulation in cancer cells mediated by AMPK, along with preclinical evidence supporting a tractable therapeutic strategy to reverse mesenchymal phenotypes associated with invasion and metastasis.

Activators of AMPK: not just for Type II diabetes

Recent discoveries of AMPK activators point to the large number of therapeutic candidates that can be transformed to successful designs of novel drugs. AMPK is a universal energy sensor and influences almost all physiological processes in the cells. Thus, regulation of the cellular energy metabolism can be achieved in selective tissues via the artificial activation of AMPK by small molecules. Recently, special attention has been given to direct activators of AMPK that are regulated by several nonspecific upstream factors. The direct activation of AMPK, by definition, should lead to more specific biological activities and as a result minimize possible side effects.

Optimization of troglitazone derivatives as potent anti-proliferative agents: towards more active and less toxic compounds

Δ2-Troglitazone derivatives were shown to exhibit anti-proliferative activity in a PPARγ-independent manner. We prepared various compounds in order to increase their potency and decrease their toxicity towards non-malignant primary cultured hepatocytes. Many compounds induced viabilities less than 20% at 10 μM on various cancer cell lines. Furthermore, five of them showed hepatocyte viability of 80% or more at 200 μM. In addition, compounds 17 and 18 exhibited promising maximum tolerated doses on a murine model, enabling future investigations.

MicroRNA-296-5p (miR-296-5p) functions as a tumor suppressor in prostate cancer by directly targeting Pin1

Upregulation of Pin1 was shown to advance the functioning of several oncogenic pathways. It was recently shown that Pin1 is potentially an excellent prognostic marker and can also serve as a novel therapeutic target for prostate cancer. However, the molecular mechanism of Pin1 overexpression in prostate cancer is still unclear. In the present study, we showed that the mRNA expression levels of Pin1 were not correlated with Pin1 protein levels in prostate cell lines which indicated that Pin1 may be regulated at the post-transcriptional level. A key player in post-transcriptional regulation is represented by microRNAs (miRNAs) that negatively regulate expressions of protein-coding genes at the post-transcriptional level. A bioinformatics analysis revealed that miR-296-5p has a conserved binding site in the Pin1 3'-untranslated region (UTR). A luciferase reporter assay demonstrated that the seed region of miR-296-5p directly interacts with the 3'-UTR of Pin1 mRNA. Moreover, miR-296-5p expression was found to be inversely correlated with Pin1 expression in prostate cancer cell lines and prostate cancer tissues. Furthermore, restoration of miR-296-5p or the knockdown of Pin1 had the same effect on the inhibition of the ability of cell proliferation and anchorage-independent growth of prostate cancer cell lines. Our results support miR-296-5p playing a tumor-suppressive role by targeting Pin1 and implicate potential effects of miR-296-5p on the prognosis and clinical application to prostate cancer therapy.

Chemopreventive drugs: Mechanisms via inhibition of cancer stem cells in colorectal cancer

Recent epidemiological studies, basic research and clinical trials on colorectal cancer (CRC) prevention have helped identify candidates for effective chemopreventive drugs. However, because of the conflicting results of clinical trials or side effects, the effective use of chemopreventive drugs has not been generalized, except for patients with a high-risk for developing hereditary CRC. Advances in genetic and molecular technologies have highlighted the greater complexity of carcinogenesis, especially the heterogeneity of tumors. We need to target cells and processes that are critical to carcinogenesis for chemoprevention and treatment of advanced cancer. Recent research has shown that intestinal stem cells may serve an important role in tumor initiation and formation of cancer stem cells. Moreover, studies have shown that the tumor microenvironment may play additional roles in dedifferentiation, to enable tumor cells to take on stem cell features and promote the formation of tumorigenic stem cells. Therefore, early tumorigenic changes of stem cells and signals for dedifferentiation may be good targets for chemoprevention. In this review, I focus on cancer stem cells in colorectal carcinogenesis and the effect of major chemopreventive drugs on stem cell-related pathways.

Multinuclear ruthenium(ii) complexes as anticancer agents

The dinuclear ruthenium complex with X = H is four-times more cytotoxic than cisplatin against breast cancer cell lines; however, when X = NO₂ the ruthenium complex is less active than cisplatin.

Novel potential agents for ulcerative colitis by molecular topology: suppression of IL-6 production in Caco-2 and RAW 264.7 cell lines

Ulcerative colitis (UC) is an immune-mediated chronic and relapsing intestinal inflammatory disease. Interleukin (IL)-6, a pro-inflammatory cytokine, plays a key role in the uncontrolled intestinal inflammatory process, which is a main characteristic of UC. In this work, a quantitative structure-activity relationship model based on molecular topology (MT) has been built up to predict the IL-6 mediated anti-UC activity. After an external validation of the model, a virtual screening of the MicroSource Pure Natural Products Collection and Sigma-Aldrich databases was carried out looking for potential new active compounds. From the entire set of compounds labeled as active by the model, four of them, namely alizarin-3-methylimino-N,N-diacetic acid (AMA), Calcein, (+)-dibenzyl-L-tartrate (DLT), and Ro 41-0960, were tested in vitro by determination of IL-6 production in two cell lines (RAW 264.7 and Caco-2). The results demonstrate that three of them were able to significantly reduce IL-6 levels in both cell lines and particularly one, namely Ro 41-0960. These results confirm MT's efficacy as a tool for the selection of compounds potentially active in UC.

Development of Novel Alkene Oxindole Derivatives As Orally Efficacious AMP-Activated Protein Kinase Activators

Adenosine 5'-monophosphate-activated protein kinase (AMPK) is emerging as a promising drug target for its regulatory function in both glucose and lipid metabolism. Compound PT1 (5) was originally identified from high throughput screening as a small molecule activator of AMPK through the antagonization of the autoinhibition in α subunits. In order to enhance its potency at AMPK and bioavailability, structure-activity relationship studies have been performed and resulted in a novel series of AMPK activators based on an alkene oxindole scaffold. Following their evaluation in pharmacological AMPK activation assays, lead compound 24 was identified to possess improved potency as well as favorable pharmacokinetic profile. In the diet-induced obesity (DIO) mouse model, compound 24 was found to improve glucose tolerance and alleviate insulin resistance. The in vitro and in vivo data for these alkene oxindoles warrant further studies for their potential therapeutic medications in metabolic associated diseases.

Innovations in organ donation

The growing disparity between organ availability for transplantation and the number of patients in need has challenged the donation and transplantation community of practice to develop innovative processes, ideas, and techniques to bridge the gaps. Advances in the sharing of best practices in the donation community have contributed greatly over the last 8 years. Broader sharing of updated guidelines for declaration of brain death in conjunction with improvements in deceased donor management have increased opportunities for organ donation. New techniques for organ preservation and organ resuscitation have allowed for better utilization of the potential donor pool. This review will highlight processes, ideas, and techniques in organ donation.

AMP-activated protein kinase: new regulation, new roles?

The hydrolysis of ATP drives virtually all of the energy-requiring processes in living cells. A prerequisite of living cells is that the concentration of ATP needs to be maintained at sufficiently high levels to sustain essential cellular functions. In eukaryotic cells, the AMPK (AMP-activated protein kinase) cascade is one of the systems that have evolved to ensure that energy homoeostasis is maintained. AMPK is activated in response to a fall in ATP, and recent studies have suggested that ADP plays an important role in regulating AMPK. Once activated, AMPK phosphorylates a broad range of downstream targets, resulting in the overall effect of increasing ATP-producing pathways whilst decreasing ATP-utilizing pathways. Disturbances in energy homoeostasis underlie a number of disease states in humans, e.g. Type 2 diabetes, obesity and cancer. Reflecting its key role in energy metabolism, AMPK has emerged as a potential therapeutic target. In the present review we examine the recent progress aimed at understanding the regulation of AMPK and discuss some of the latest developments that have emerged in key areas of human physiology where AMPK is thought to play an important role.

Targeting energy metabolic and oncogenic signaling pathways in triple-negative breast cancer by a novel adenosine monophosphate-activated protein kinase (AMPK) activator

The antitumor activities of the novel adenosine monophosphate-activated protein kinase (AMPK) activator, OSU-53, were assessed in in vitro and in vivo models of triple-negative breast cancer. OSU-53 directly stimulated recombinant AMPK kinase activity (EC(50), 0.3 μM) and inhibited the viability and clonogenic growth of MDA-MB-231 and MDA-MB-468 cells with equal potency (IC(50), 5 and 2 μM, respectively) despite lack of LKB1 expression in MDA-MB-231 cells. Nonmalignant MCF-10A cells, however, were unaffected. Beyond AMPK-mediated effects on mammalian target of rapamycin signaling and lipogenesis, OSU-53 also targeted multiple AMPK downstream pathways. Among these, the protein phosphatase 2A-dependent dephosphorylation of Akt is noteworthy because it circumvents the feedback activation of Akt that results from mammalian target of rapamycin inhibition. OSU-53 also modulated energy homeostasis by suppressing fatty acid biosynthesis and shifting the metabolism to oxidation by up-regulating the expression of key regulators of mitochondrial biogenesis, such as a peroxisome proliferator-activated receptor γ coactivator 1α and the transcription factor nuclear respiratory factor 1. Moreover, OSU-53 suppressed LPS-induced IL-6 production, thereby blocking subsequent Stat3 activation, and inhibited hypoxia-induced epithelial-mesenchymal transition in association with the silencing of hypoxia-inducible factor 1a and the E-cadherin repressor Snail. In MDA-MB-231 tumor-bearing mice, daily oral administration of OSU-53 (50 and 100 mg/kg) suppressed tumor growth by 47-49% and modulated relevant intratumoral biomarkers of drug activity. However, OSU-53 also induced protective autophagy that attenuated its antiproliferative potency. Accordingly, cotreatment with the autophagy inhibitor chloroquine increased the in vivo tumor-suppressive activity of OSU-53. OSU-53 is a potent, orally bioavailable AMPK activator that acts through a broad spectrum of antitumor activities.

Pleiotropic effects of glitazones: a double edge sword?

Glitazones (thiazolidinediones) are drugs used for diabetes mellitus type 2. By binding to peroxisome proliferator-activated receptor γ (PPARγ) they modulate transcription of genes of carbohydrate and lipid metabolism. Through PPARγ stimulation, however, glitazones also affect other genes, encompassing inflammation, cell growth and differentiation, angiogenesis, which broads their therapeutic potential. The gene expression profile induced by each glitazone shows peculiarities, which may affect its benefit/risk balance; indeed, troglitazone and rosiglitazone have been associated with liver failure and coronary disease, respectively; whether or not these severe adverse effects are solely related to PPARγ remains yet unclear, since glitazones exert also PPARγ-independent effects. Glitazone chemistry serves as scaffold for synthesizing new compounds with PPARγ-independent pharmacological properties and we report here a preliminary observation of inhibition of vasoconstriction by troglitazone in isolated vessels, an effect that appears fast, reversible, and PPARγ-independent. Pleiotropic effects of glitazones need specific attention in terms of drug safety, but also provide basis for drug development and novel experimental therapeutics.

A Potent and Selective AMPK Activator That Inhibits de Novo Lipogenesis

AMP-activated protein kinase (AMPK) is a heterotrimeric kinase that regulates cellular energy metabolism by affecting energy-consuming pathways such as de novo lipid biosynthesis and glucose production as well as energy-producing pathways such as lipid oxidation and glucose uptake. Accordingly, compounds that activate AMPK represent potential drug candidates for the treatment of hyperlipidemia and type 2 diabetes. Screening of a proprietary library of AMP mimetics identified the phosphonic acid 2 that bears little structural resemblance to AMP but is capable of activating AMPK with high potency (EC50 = 6 nM vs AMP EC50 = 6 μM) and specificity. Phosphonate prodrugs of 2 inhibited de novo lipogenesis in cellular and animal models of hyperlipidemia.

AMPK and vasculoprotection

AMP-activated protein kinase (AMPK) is proposed to be a key regulator of cellular and organismal metabolism and has reported vasculoprotective effects. In addition, many therapeutic agents used in the treatment of diabetes and atherosclerosis such as metformin, thiazolidinediones and statins may exert their vasculoprotective effects through activation of AMPK. Activation of AMPK has a number of potentially beneficial anti-atherosclerotic effects including reducing adhesion of inflammatory cells to the blood vessel endothelium, reducing lipid accumulation and the proliferation of inflammatory cells caused by oxidised lipids, stimulation of gene expression responsible for cellular antioxidant defenses and stimulation of enzymes responsible for nitric oxide formation. In humans and animals the AMPK cascade triggers vascular protective mechanisms that have been shown to reduce myocardial ischaemic injury and mutations in AMPK can cause familial hypertrophic cardiomyopathy. Taken together, these data suggest that activation and function of AMPK contributes to cardiovascular health. In this review we propose to focus on the vasculoprotective effects of AMPK, the evidence for AMPK activation with currently used therapeutic agents and the potential for agents which specifically activate AMPK as a treatment for vascular disease.

AMP-activated protein kinase as a target for preconditioning in transplantation medicine

Graft quality before transplantation is a major factor influencing chronic rejection. Organ preservation and ischemia/reperfusion play an important role in the induction of organ injury. Although both suppression of metabolism by hypothermic preservation and preconditioning before ischemia limit injury, understanding the biochemical signaling pathways will allow us to optimize graft preservation further. Adenosine monophosphate-activated protein kinase (AMPK) is an important enzyme sensing cellular energy balance and regulating downstream signaling pathways, signaling toward an energy-conserving state. In this review, we summarize available literature regarding the protective signaling pathways activated by (hypothermic) ischemia and preconditioning and how they can be activated pharmacologically. Optimizing the graft quality before transplantation improves long-term graft survival. The major factor influencing organ quality is organ preservation, cold storage, currently, being a common practice. Loss of cellular homeostasis, inflammation, and endothelial dysfunction are the major factors inducing injury after cold storage. Adenosine triphosphate depletion and anaerobic metabolism during the cold ischemic period lead to mitochondrial dysfunction, disturbed osmoregulation, and cell death inducing inflammation. Ischemic preconditioning consists of brief periods of ischemia preceding preservation and protects organs against injury because of subsequent ischemia/reperfusion, in which endothelial nitric oxide synthase, nuclear factor-kB, and adenosine play a major role. After conversion of adenosine to AMP, AMPK can be activated, a central kinase involved in sensing cellular [AMP]:[adenosine triphosphate] levels and signaling toward an energy-conserving state. Pharmacologic activation of AMPK demonstrated its ability to activate endothelial nitric oxide synthase and inhibit nuclear factor-kB, thereby limiting endothelial dysfunction and inflammation. Further, studies in knock-out mice lacking ENTDP1 and NT5E (enzymes catalyzing formation and degradation of AMP, respectively) demonstrated a clear protective role for AMP in ischemia/reperfusion. AMPK activation before or during organ preservation might be a promising pharmacologic approach to limit organ injury and maintain graft quality before transplantation.