Pseudolaric acid B inhibits angiogenesis and reduces hypoxia-inducible factor 1alpha by promoting proteasome-mediated degradation

Design, synthesis, and evaluation of antitumor activity in Pseudolaric acid B Azole derivatives: Novel and potent angiogenesis inhibitor via regulation of the PI3K/AKT and MAPK mediated HIF-1/VEGF signaling pathway

Tumor proliferation and metastasis are intricately linked to blood vessel formation, with vascular endothelial growth factor (VEGF) playing a pivotal role in orchestrating angiogenesis throughout tumor progression. Pseudolaric acid B (PAB) has emerged as a potent inhibitor of tumor cell proliferation, migration, and angiogenesis. In efforts to enhance its efficacy, 37 derivatives of PAB were synthesized and assessed for their capacity to suppress VEGF secretion in SiHa cells under hypoxic conditions. Notably, majority of these derivatives exhibited significant inhibition of VEGF protein secretion without inducing cytotoxicity. Among them, compound M2 displayed the most potent inhibitory activity, with an IC50 value of 0.68 μM, outperforming the lead compound PAB (IC50 = 5.44 μM). Compound M2 not only curbed the migration and angiogenesis of HUVECs under hypoxic conditions but also hindered the invasion of SiHa cells. Mechanistic investigations unveiled that compound M2 may impede the accumulation and nuclear translocation of hypoxia-inducible factor 1α (HIF-1α) in SiHa cells, thereby downregulating VEGF expression. This inhibitory effect on HIF-1α was corroborated by experiments utilizing the protease inhibitor MG-132 and protein synthesis inhibitor CHX, indicating that compound M2 diminishes HIF-1α levels by reducing its synthesis. Furthermore, compound M2 was observed to modulate the PI3K/AKT/mTOR and MAPK signaling pathways in tumor cells, thereby regulating HIF-1α translation and synthesis. In vivo studies demonstrated that compound M2 exhibited low toxicity and effectively curbed tumor growth. Immunohistochemistry analyses validated that compound M2 effectively suppressed the expression of HIF-1α and VEGF in tumor tissues, underscoring its potential as a promising therapeutic agent for targeting tumor angiogenesis.

Pseudolaric Acid B Targets CD147 to Selectively Kill Acute Myeloid Leukemia Cells

Acute myeloid leukemia (AML) is an aggressive blood cancer. With low survival rates, new drug targets are needed to improve treatment regimens and patient outcomes. Pseudolaric acid B (PAB) is a plant-derived bioactive compound predicted to interact with cluster of differentiation 147 (CD147/BSG). CD147 is a transmembrane glycoprotein overexpressed in various malignancies with suggested roles in regulating cancer cell survival, proliferation, invasion, and apoptosis. However, the detailed function of PAB in AML remains unknown. In this study, AML cell lines and patient-derived cells were used to show that PAB selectively targeted AML (IC50: 1.59 ± 0.47 µM). Moreover, proliferation assays, flow cytometry, and immunoblotting confirmed that PAB targeting of CD147 resulted in AML cell apoptosis. Indeed, the genetic silencing of CD147 significantly suppressed AML cell growth and attenuated PAB activity. Overall, PAB imparts anti-AML activity through transmembrane glycoprotein CD147.

Hypoxia: syndicating triple negative breast cancer against various therapeutic regimens

Triple-negative breast cancer (TNBC) is one of the deadliest subtypes of breast cancer (BC) for its high aggressiveness, heterogeneity, and hypoxic nature. Based on biological and clinical observations the TNBC related mortality is very high worldwide. Emerging studies have clearly demonstrated that hypoxia regulates the critical metabolic, developmental, and survival pathways in TNBC, which include glycolysis and angiogenesis. Alterations to these pathways accelerate the cancer stem cells (CSCs) enrichment and immune escape, which further lead to tumor invasion, migration, and metastasis. Beside this, hypoxia also manipulates the epigenetic plasticity and DNA damage response (DDR) to syndicate TNBC survival and its progression. Hypoxia fundamentally creates the low oxygen condition responsible for the alteration in Hypoxia-Inducible Factor-1alpha (HIF-1α) signaling within the tumor microenvironment, allowing tumors to survive and making them resistant to various therapies. Therefore, there is an urgent need for society to establish target-based therapies that overcome the resistance and limitations of the current treatment plan for TNBC. In this review article, we have thoroughly discussed the plausible significance of HIF-1α as a target in various therapeutic regimens such as chemotherapy, radiotherapy, immunotherapy, anti-angiogenic therapy, adjuvant therapy photodynamic therapy, adoptive cell therapy, combination therapies, antibody drug conjugates and cancer vaccines. Further, we also reviewed here the intrinsic mechanism and existing issues in targeting HIF-1α while improvising the current therapeutic strategies. This review highlights and discusses the future perspectives and the major alternatives to overcome TNBC resistance by targeting hypoxia-induced signaling.

Anticancer Therapeutic Effects of Green Tea Catechins (GTCs) When Integrated with Antioxidant Natural Components

After decades of research and development concerning cancer treatment, cancer is still at large and very much a threat to the global human population. Cancer remedies have been sought from all possible directions, including chemicals, irradiation, nanomaterials, natural compounds, and the like. In this current review, we surveyed the milestones achieved by green tea catechins and what has been accomplished in cancer therapy. Specifically, we have assessed the synergistic anticarcinogenic effects when green tea catechins (GTCs) are combined with other antioxidant-rich natural compounds. Living in an age of inadequacies, combinatorial approaches are gaining momentum, and GTCs have progressed much, yet there are insufficiencies that can be improvised when combined with natural antioxidant compounds. This review highlights that there are not many reports in this specific area and encourages and recommends research attention in this direction. The antioxidant/prooxidant mechanisms of GTCs have also been highlighted. The current scenario and the future of such combinatorial approaches have been addressed, and the lacunae in this aspect have been discussed.

Role of macrophage polarization in osteoarthritis (Review)

Osteoarthritis (OA) is a disease involving the whole joint that seriously reduces the living standards of individuals. Traditional treatments include physical therapy, administration of anti-inflammatory and analgesic drugs and injection of glucocorticoids or hyaluronic acid into the joints. However, these methods have limited efficacy and it is difficult to reverse the progression of OA, therefore it is urgent to find new effective treatment methods. Immune microenvironment is significant in the occurrence and development of OA. Recent studies have shown that macrophages are important targets for the treatment of OA. Macrophages are polarized into M1 pro-inflammatory phenotype and M2 anti-inflammatory phenotype under stimulation of different factors, which release and regulate inflammatory response and cartilage growth. Accumulating studies have tried to alleviate OA by regulating macrophage homeostasis. The present study summarized the related studies, discuss the mechanism of various therapeutic reagents on OA, expound the molecular mechanism of drug effect on OA and attempted to provide clues for the treatment of OA.

Targeting HIF-1α by Natural and Synthetic Compounds: A Promising Approach for Anti-Cancer Therapeutics Development

Advancement in novel target detection using improved molecular cancer biology has opened up new avenues for promising anti-cancer drug development. In the past two decades, the mechanism of tumor hypoxia has become more understandable with the discovery of hypoxia-inducible factor-1α (HIF-1α). It is a major transcriptional regulator that coordinates the activity of various transcription factors and their downstream molecules involved in tumorigenesis. HIF-1α not only plays a crucial role in the adaptation of tumor cells to hypoxia but also regulates different biological processes, including cell proliferation, survival, cellular metabolism, angiogenesis, metastasis, cancer stem cell maintenance, and propagation. Therefore, HIF-1α overexpression is strongly associated with poor prognosis in patients with different solid cancers. Hence, pharmacological targeting of HIF-1α has been considered to be a novel cancer therapeutic strategy in recent years. In this review, we provide brief descriptions of natural and synthetic compounds as HIF-1α inhibitors that have the potential to accelerate anticancer drug discovery. This review also introduces the mode of action of these compounds for a better understanding of the chemical leads, which could be useful as cancer therapeutics in the future.

Pseudolaric acid B ameliorates synovial inflammation and vessel formation by stabilizing PPARγ to inhibit NF-κB signalling pathway

Synovial macrophage polarization and inflammation are essential for osteoarthritis (OA) development, yet the molecular mechanisms and regulation responsible for the pathogenesis are still poorly understood. Here, we report that pseudolaric acid B (PAB) attenuated articular cartilage degeneration and synovitis during OA. PAB, a diterpene acid, specifically inhibited NF-κB signalling and reduced the production of pro-inflammatory cytokines, which further decreased M1 polarization and vessel formation. We further provide in vivo and in vitro evidences that PAB suppressed NF-κB signalling by stabilizing PPARγ. Using PPARγ antagonist could abolish anti-inflammatory effect of PAB and rescue the activation of NF-κB signalling during OA. Our findings identify a previously unrecognized role of PAB in the regulation of OA and provide mechanisms by which PAB regulates NF-κB signalling through PPARγ, which further suggest targeting synovial inflammation or inhibiting vessel formation at early stage could be an effective preventive strategy for OA.

Identification of pseudolaric acid B as a novel Hedgehog pathway inhibitor in medulloblastoma

Aberrant activation of the Hedgehog (Hh) pathway is implicated in the pathogenesis and development of multiple cancers, especially Hh-driven medulloblastoma (MB). Smoothened (SMO) is a promising therapeutic target of the Hh pathway in clinical cancer treatment. However, SMO mutations frequently occur, which leads to drug resistance and tumor relapse. Novel inhibitors that target both the wild-type and mutant SMO are in high demand. In this study, we identified a novel Hh pathway inhibitor, pseudolaric acid B (PAB), which significantly inhibited the expression of Gli1 and its transcriptional target genes, such as cyclin D1 and N-myc, thus inhibiting the proliferation of DAOY and Ptch1^+/- primary MB cells. Mechanistically, PAB can potentially bind to the extracellular entrance of the heptahelical transmembrane domain (TMD) of SMO, based on molecular docking and the BODIPY-cyclopamine binding assay. Further, PAB also efficiently blocked ciliogenesis, demonstrating the inhibitory effects of PAB on the Hh pathway at multiple levels. Thus, PAB may overcome drug-resistance induced by SMO mutations, which frequently occurs in clinical setting. PAB markedly suppressed tumor growth in the subcutaneous allografts of Ptch1^+/- MB cells. Together, our results identified PAB as a potent Hh pathway inhibitor to treat Hh-dependent MB, especially cases resistant to SMO antagonists.

Natural Products in Cancer Therapy: Past, Present and Future

Natural products, with remarkable chemical diversity, have been extensively investigated for their anticancer potential for more than a half-century. The collective efforts of the community have achieved the tremendous advancements, bringing natural products to clinical use and discovering new therapeutic opportunities, yet the challenges remain ahead. With remarkable changes in the landscape of cancer therapy and growing role of cutting-edge technologies, we may have come to a crossroads to revisit the strategies to understand nature products and to explore their therapeutic utility. This review summarizes the key advancements in nature product-centered cancer research and calls for the implementation of systematic approaches, new pharmacological models, and exploration of emerging directions to revitalize natural products search in cancer therapy.

Pseudolaric Acid B Inhibits Proliferation, Invasion, and Angiogenesis in Esophageal Squamous Cell Carcinoma Through Regulating CD147

Background

Esophageal squamous cell carcinoma (ESCC) is a common malignant tumor of the digestive system. Studies have shown that pseudolaric acid B (PAB) has several pharmacological effects like anti-microtubule, anti-angiogenesis, and antitumor functions, while the effect and mechanism of PAB on esophageal cancer are still unclear. This study was designed to investigate the effects of PAB on ESCC.

Methods

To study the effects of PAB on the biological function through a series of in vitro and in vivo experiments.

Results

The results revealed that PAB inhibited the proliferation, invasion, and migration, but promoted the apoptosis of ESCC. Moreover, PAB restrained the growth of cancer cells in vivo and inhibited the angiogenesis of HUVEC in mice with ESCC. CD147 expression was increased in the esophageal squamous cell lines, and interference with CD147 hindered the proliferation, invasion, and migration of ESCC cells, and inhibited the growth and angiogenesis of the esophageal squamous cell line. PAB reduced the expression of CD147 in vivo and in vitro. The expression of MMP2, 3, and 9 was increased after overexpression of CD147, which provided the opportunity to reverse the role of PAB in inhibiting proliferation, invasion, migration, and angiogenesis of ESCC.

Discussion

The results revealed that PAB inhibited the proliferation, invasion, migration, and angiogenesis of ESCC in vitro and in vivo by CD147. PAB is a promising monomer for therapy of ESCC, providing references for future research on ESCC treatment.

Pharmacologic Targeting of Hypoxia-Inducible Factors

Hypoxia-inducible factors (HIFs) control transcriptional responses to reduced O₂ availability. HIFs are heterodimeric proteins composed of an O₂-regulated HIF-α subunit and a constitutively expressed HIF-1β subunit. HIF-α subunits are subject to prolyl hydroxylation, which targets the proteins for degradation under normoxic conditions. Small molecule prolyl hydroxylase inhibitors, which stabilize the HIF-α subunits and increase HIF-dependent expression of erythropoietin, are in phase III clinical trials for the treatment of anemia in patients with chronic kidney disease. HIFs contribute to the pathogenesis of many cancers, particularly the clear cell type of renal cell carcinoma in which loss of function of the von Hippel-Lindau tumor suppressor blocks HIF-2α degradation. A small molecule inhibitor that binds to HIF-2α and blocks dimerization with HIF-1β is in clinical trials for the treatment of renal cell carcinoma. Targeting HIFs for stabilization or inhibition may improve outcomes in diseases that are common causes of mortality in the US population.

New microtubulin inhibitor MT189 suppresses angiogenesis via the JNK-VEGF/VEGFR2 signaling axis

The microtubulin inhibitor MT189 possesses anticancer activity and has been shown to overcome multidrug resistance. Here, we report that MT189 also inhibits angiogenesis. MT189 inhibited the proliferation, migration and differentiation of endothelial cells, with or without VEGF stimulation, and suppressed microvessel formation ex vivo and in vivo. MT189 reduced VEGF expression and secretion in both tumor and endothelial cells, under either hypoxic or normoxic conditions. The activation of VEGFR2 and downstream Src was thus abrogated in the MT189-treated endothelial cells. MT189 subsequently stabilized endothelial cell-cell junctions consist of VE-cadherin, β-catenin, vinculin, and actin. MT189 also disrupted endothelial cell-matrix junctions by inhibiting the turnover of focal adhesions containing FAK, paxillin, vinculin, and actin. Inhibition of JNK reversed MT189-mediated inhibition of endothelial migration and differentiation, JNK activation, the reduction of VEGF expression and secretion, and the decrease of Src and FAK phosphorylation. These results indicate that MT189 suppresses angiogenesis by reducing endothelial proliferation, migration, and differentiation via the JNK-VEGF/VEGFR2 signaling axis. Together with our previous report showing that MT189 exhibited anticancer activity via the JNK-MCL-1 pathway, these new findings further support MT189-based drug development for cancer therapy.

A Systematic Review of the Immune-Regulating and Anticancer Activities of Pseudolaric Acid B

Cortex pseudolaricis, the root bark of Pseudolarix kaempferi Gord, has been used to treat tinea and other skin diseases for the antimicrobial activities in Traditional Chinese Medicine (TCM). Pseudolaric acid B (PAB) has been identified as the major component responsible for the action of C. pseudolaricis. Recently, PAB has been demonstrated to be used as novel treatments for cancer, immune disorders, inflammatory diseases, and immunosuppression. However, the mechanisms through which PAB exerts its properties are not understood well, and little attention in the literature has been given to review its pharmacological activities before. In this review, we performed a systematic summary of the literature with respect to the anticancer, immunosuppressive and anti-inflammatory properties of PAB and its derivatives. Currently available data suggest that PAB is a promising immunosuppressive and anti-inflammatory agent candidate and should be explored further in cancer treatment and prevention.

Hypoxia inducible factor down-regulation, cancer and cancer stem cells (CSCs): ongoing success stories

In cancers, hypoxia inducible factor 1 (HIF-1) is an over-expressed transcription factor, which regulates a large set of genes involved in tumour vascularization, metastases, and cancer stem cells (CSCs) formation and self-renewal. This protein has been identified as a relevant target in oncology and several HIF-1 modulators are now marketed or in advanced clinical trials. The purpose of this review is to summarize the advances in the understanding of its regulation and its inhibition, from the medicinal chemist point of view. To this end, we selected in the recent literature relevant examples of "hit" compounds, including small-sized organic molecules, pseudopeptides and nano-drugs, exhibiting in vitro and/or in vivo both anti-HIF-1 and anti-tumour activities. Whenever possible, a particular emphasis has been dedicated to compounds that selectively target CSCs.

Chemical proteomics reveal CD147 as a functional target of pseudolaric acid B in human cancer cells

Pseudolaric acid B targets CD147 in human cancer cells.

Naringenin exerts anti-angiogenic effects in human endothelial cells: Involvement of ERRα/VEGF/KDR signaling pathway

Naringenin (Nar), most abundant in oranges and tomatoes, are known for the hypocholesterolemic, anti-estrogenic, hypolipidemic, anti-hypertensive, and anti-inflammatory activities. Here, the present study was designed to investigate the in vitro and in vivo anti-angiogenesis of Nar. Inhibition of angiogenesis was determined in vitro by using proliferation, apoptosis, migration, and tube-formation assays in Nar-treated human endothelial cell. Finally, CAM assays were used to assess inhibitory effect of Nar on physiological angiogenesis in vivo. The data suggest that Nar should be a direct ERRα inhibitor capable of inhibiting angiogenesis in vitro and in vivo, including endothelial cell proliferation, survival, migration and capillary-like structures formation of HUVECs, as well as reduced neovascularization of the CAM. Furthermore, the effects exerted by Nar are cell cycle related and mediated by VEGF/KDR signaling pathway along with downregulation of certain proangiogenic inflammatory cytokines. Our data thus provide potential molecular mechanisms through which Nar manifests it as a promising anti-angiogenic and anti-cancer agent.

Stabilizing versus destabilizing the microtubules: a double-edge sword for an effective cancer treatment option?

Microtubules are dynamic and structural cellular components involved in several cell functions, including cell shape, motility, and intracellular trafficking. In proliferating cells, they are essential components in the division process through the formation of the mitotic spindle. As a result of these functions, tubulin and microtubules are targets for anticancer agents. Microtubule-targeting agents can be divided into two groups: microtubule-stabilizing, and microtubule-destabilizing agents. The former bind to the tubulin polymer and stabilize microtubules, while the latter bind to the tubulin dimers and destabilize microtubules. Alteration of tubulin-microtubule equilibrium determines the disruption of the mitotic spindle, halting the cell cycle at the metaphase-anaphase transition and, eventually, resulting in cell death. Clinical application of earlier microtubule inhibitors, however, unfortunately showed several limits, such as neurological and bone marrow toxicity and the emergence of drug-resistant tumor cells. Here we review several natural and synthetic microtubule-targeting agents, which showed antitumor activity and increased efficacy in comparison to traditional drugs in various preclinical and clinical studies. Cryptophycins, combretastatins, ombrabulin, soblidotin, D-24851, epothilones and discodermolide were used in clinical trials. Some of them showed antiangiogenic and antivascular activity and others showed the ability to overcome multidrug resistance, supporting their possible use in chemotherapy.

Synthesis and biological evaluation of pseudolaric acid B derivatives as potential immunosuppressive agents

Pseudolaric acid B (PB) derivatives with immunosuppressive activity were found by our group. In order to find potential immunosuppressive agents with high efficacy and low toxicity, a series of novel PB derivatives were synthesized and evaluated on their immunosuppressive activities. Most of the synthesized compounds were tested in vitro on murine T and B proliferation. In particular, compound 11 exhibited excellent inhibitory activity toward murine T cells (up to 19-fold enhancement compared to that of mycophenolatemofetil) and little cytotoxicity toward normal murine spleen cells. These experimental data demonstrated that some of these PB derivatives have great potential for future immunosuppressive studies.

Natural compounds regulate glycolysis in hypoxic tumor microenvironment

In the early twentieth century, Otto Heinrich Warburg described an elevated rate of glycolysis occurring in cancer cells, even in the presence of atmospheric oxygen (the Warburg effect). Recently it became a therapeutically interesting strategy and is considered as an emerging hallmark of cancer. Hypoxia inducible factor-1 (HIF-1) is one of the key transcription factors that play major roles in tumor glycolysis and could directly trigger Warburg effect. Thus, how to inhibit HIF-1-depended Warburg effect to assist the cancer therapy is becoming a hot issue in cancer research. In fact, HIF-1 upregulates the glucose transporters (GLUT) and induces the expression of glycolytic enzymes, such as hexokinase, pyruvate kinase, and lactate dehydrogenase. So small molecules of natural origin used as GLUT, hexokinase, or pyruvate kinase isoform M2 inhibitors could represent a major challenge in the field of cancer treatment. These compounds aim to suppress tumor hypoxia induced glycolysis process to suppress the cell energy metabolism or enhance the susceptibility of tumor cells to radio- and chemotherapy. In this review, we highlight the role of natural compounds in regulating tumor glycolysis, with a main focus on the glycolysis under hypoxic tumor microenvironment.

MCL-1 degradation mediated by JNK activation via MEKK1/TAK1-MKK4 contributes to anticancer activity of new tubulin inhibitor MT189

Colchicine site-targeted tubulin inhibitors are a promising type of anticancer drugs. MT189 is a new derivative of MT119, a previously reported colchicine site-binding antitubulin agent. In this study, MT189 was demonstrated to retain the property of MT119 in disrupting microtubulin via binding to the colchicine site, causing mitotic arrest and inducing apoptosis, and to display 8.7-fold enhanced proliferative inhibition in a panel of cancer cells. MT189 was shown to elicit in vivo anticancer effects on MDA-MB-231 xenografts in nude mice, and the tumor growth was suppressed by 35.9% over 14 days. MT189 led to degradation of MCL-1, a member of the antiapoptotic BCL-2 protein family. Its overexpression reduced but its silenced expression increased the apoptotic induction followed by the treatment with MT189. Moreover, the treatment with MT189 caused activation of the MEKK1/TAK1-MKK4-JNK signaling pathway. The activated JNK resulted in phosphorylation of MCL-1, which facilitated its ubiquitination-mediated degradation. Our results show that MT189 inhibits microtubulin polymerization by binding to the colchicine site. Relief of apoptotic suppression by MCL-1 degradation together with mitotic arrest contributes to the anticancer activity of MT189.

Pseudolarenone, an unusual nortriterpenoid lactone with a fused 5/11/5/6/5 ring system featuring an unprecedented bicyclo[8.2.1]tridecane core from Pseudolarix amabilis

A phytochemical investigation of the cone of Pseudolarix amabilis led to the isolation of pseudolarenone (), a structurally novel pentacyclic (5/11/5/6/5) nortriterpenoid lactone with an unprecedented carbon skeleton featuring a unique bicyclo[8.2.1]tridecane core. Its structure and absolute configurations were elucidated by spectroscopic analysis and single crystal X-ray diffraction (CuK(α)).

JNK signaling maintains the mesenchymal properties of multi-drug resistant human epidermoid carcinoma KB cells through snail and twist1

BACKGROUND AND METHODS

In addition to possess cross drug resistance characteristic, emerging evidences have shown that multiple-drug resistance (MDR) cancer cells exhibit aberrant metastatic capacity when compared to parental cells. In this study, we explored the contribution of c-Jun N-terminal kinases (JNK) signaling to the mesenchymal phenotypes and the aberrant motile capacity of MDR cells utilizing a well characterized MDR cell line KB/VCR, which is established from KB human epidermoid carcinoma cells by vincristine (VCR), and its parental cell line KB.

RESULTS

Taking advantage of experimental strategies including pharmacological tool and gene knockdown, we showed here that interference with JNK signaling pathway by targeting JNK1/2 or c-Jun reversed the mesenchymal properties of KB/VCR cells to epithelial phenotypes and suppressed the motile capacity of KB/VCR cells, such as migration and invasion. These observations support a critical role of JNK signaling in maintaining the mesenchymal properties of KB/VCR cells. Furthermore, we observed that JNK signaling may control the expression of both snail and twist1 in KB/VCR cells, indicating that both snail and twist1 are involved in controlling the mesenchymal characteristics of KB/VCR cells by JNK signaling.

CONCLUSION

JNK signaling is required for maintaining the mesenchymal phenotype of KB/VCR cells; and JNK signaling may maintain the mesenchymal characteristics of KB/VCR cells potentially through snail and twist1.

Antitumor activity of histone deacetylase inhibitor trichostatin A in osteosarcoma cells

BACKGROUND

Histone deacetylase (HDAC) inhibitors have been reported to induce cell growth arrest, apoptosis and differentiation of tumor cells. The present study aimed to examine the effects of trichostatin A (TSA), one such inhibitor, on the cell cycle, apoptosis and invasiveness of osteosarcoma cells.

METHODS

MG- 63 cells were treated with TSA at various concentrations. Then, cell growth and apoptosis were determined by 3-(4, 5-dimethyl-2-thiazolyl)-2H-tetrazolium bromide (MTT) and TUNEL assays, respectively; cell cycling was assessed by flow cytometry; invasion assays were performed with the transwell Boyden Chamber system.

RESULTS

MTT assays revealed that TSA significantly inhibited the growth of MG-63 cells in a concentration and time dependent manner. TSA treated cells demonstrated morphological changes indicative of apoptosis and TUNEL assays revealed increased apoptosis of MG-63 cells after TSA treatment. Flow cytometry showed that TSA arrested the cell cycle in G1/G2 phase and annexin V positive apoptotic cells increased markedly. In addition, the invasiveness of MG-63 cells was inhibited by TSA in a concentration dependent manner.

CONCLUSION

Our findings demonstrate that TSA inhibits the proliferation, induces apoptosis and inhibits invasiveness of osteosarcoma cells in vitro. HDAC inhibitors may thus have promise to become new therapeutic agents against osteosarcoma.

Discovery of structurally diverse and bioactive compounds from plant resources in China

This review describes the major discoveries of structurally diverse and/or biologically significant compounds from plant resources in China, mainly from the traditional Chinese medicines (TCMs) since the establishment of our research group in 1999. In the past decade, a large array of biologically significant and novel structures has been identified from plant resources (or TCM) in our laboratory. The structural modification of several biologically important compounds led to more than 400 derivatives, some of which exhibited significantly improved activities and provided opportunities to elucidate the structure-activity relationship of the related compound class. These findings are important for drug discovery and help us understand the biological basis for the traditional applications of these plants in TCM.

Newly discovered angiogenesis inhibitors and their mechanisms of action

In the past decade, the success of angiogenesis inhibitors in clinical contexts has established the antiangiogenic strategy as an important part of cancer therapy. During that time period, we have discovered and reported 17 compounds that exert potent inhibition on angiogenesis. These compounds exhibit tremendous diversity in their sources, structures, targets and mechanisms. These studies have generated new models for further modification and optimization of inhibitory compounds, new information for mechanistic studies and a new drug candidate for clinical development. In particular, through studies on the antiangiogenic mechanism of pseudolaric acid B, we discovered a novel mechanism by which the stability of hypoxia-inducible factor 1α is regulated by the transcription factor c-Jun. We also completed a preclinical study of AL3810, a compound with the potential to circumvent tumor drug resistance to a certain extent. All of these findings will be briefly reviewed in this article.

Pseudolaric acid B induces caspase-dependent apoptosis and autophagic cell death in prostate cancer cells

Previous studies have shown that Pseudolaric acid B (PAB), a medicinal plant-derived terpenoid, is a promising chemopreventive or therapeutic agent against various types of cancer. However, less is known regarding its activity against prostate cancer. The objective of the current study is designed to determine the anti-prostate cancer effects of PAB. We demonstrated here that PAB was highly effective against both androgen-dependent (LNCaP) and androgen-independent prostate cancer cells (PC-3 and DU145) through the mechanisms involved in induction of G2/M cell cycle arrest, caspase-dependent apoptosis and autophagic cell death. Furthermore, PAB can greatly sensitize these two aggressive androgen-independent prostate cancer cells to ABT-737-induced cytotoxicity. Our findings suggest that PAB holds excellent potential as either novel chemopreventive agent or enhancer of therapeutic drug against prostate cancer.

Angiogenesis inhibition and cell cycle arrest induced by treatment with Pseudolarix acid B alone or combined with 5-fluorouracil

Angiogenesis inhibitors combined with chemotherapeutic drugs have significant efficacy in the treatment of a variety of cancers. Pseudolarix acid B (PAB) is a traditional pregnancy-terminating agent, which has previously been shown to reduce tumor growth and angiogenesis. In this study, we used the high content screening assay to examine the effects of PAB on human umbilical vein endothelial cells (HUVECs). Two hepatocarcinoma 22-transplanted mouse models were used to determine PAB efficacy in combination with 5-fluorouracil (5-Fu). Our results suggested that PAB (0.156-1.250 μM) inhibited HUVECs motility in a concentration-dependent manner without obvious cytotoxicity in vitro. In vivo, PAB (25 mg/kg/day) promoted the anti-tumor efficacy of 5-Fu (5 mg/kg/2 days) in combination therapy, resulting in significantly higher tumor inhibition rates, lower microvessel density values, and prolonged survival times. It was also demonstrated that PAB acted by blocking the cell cycle at both the G(1)/S boundary and M phase, down-regulation of vascular endothelial growth factor, hypoxia-inducible factor 1α and cyclin E expression, and up-regulation of cdc2 expression. These observations provide the first evidence that PAB in combination with 5-Fu may be useful in cancer treatment.

Pseudolaric acid B-driven phosphorylation of c-Jun impairs its role in stabilizing HIF-1alpha: a novel function-converter model

We have recently discovered that c-Jun executes a non-transcriptional function to stabilize hypoxia inducible factor 1α (HIF-1α) and that pseudolaric acid B (PAB) accelerates HIF-1α degradation and phosphorylates c-Jun at Ser63/73. In this study, PAB was used as a probe to investigate whether and how the Ser63/73 phosphorylation of c-Jun regulates its functions. The PAB-induced reduction of HIF-1α protein was rescued through supplying additional non-phosphorylated c-Jun. However, c-Jun siRNA, which reduced both the PAB-driven phosphorylated c-Jun and the total c-Jun protein, did not prevent the PAB-induced decrease in HIF-1α. HIF-1α was revealed to be co-immunoprecipitated only with the non-phosphorylated c-Jun. PAB increased the phosphorylated c-Jun while reducing the non-phosphorylated c-Jun at Ser63/73, which impaired its function in stabilizing HIF-1α. Consequently, PAB led to the degradation of HIF-1α, thus resulting in the decreased HIF-1α-dependent expression of mdr-1 and VEGF. We accordingly propose a function-converter model of c-Jun: the Ser63/73 phosphorylation serves as a function converter to convert c-Jun from its non-transcriptional function to its transcriptional function.

Fighting fire with fire: poisonous Chinese herbal medicine for cancer therapy

ETHNOPHARMACOLOGICAL RELEVANCE

Following the known principle of "fighting fire with fire", poisonous Chinese herbal medicine (PCHM) has been historically used in cancer therapies by skilled Chinese practitioners for thousands of years. In fact, most of the marketed natural anti-cancer compounds (e.g., camptothecin derivatives, vinca alkaloids, etc.) are often known in traditional Chinese medicine (TCM) and recorded as poisonous herbs as well. Inspired by the encouraging precedents, significant researches into the potential of novel anticancer drugs from other PCHM-derived natural products have been ongoing for several years and PCHM is increasingly being recognized as a gathering place for promising anti-cancer drugs. The present review aimed at giving a rational understanding of the toxicity of PCHM and, especially, providing the most recent developments on PCHM-derived anti-cancer compounds.

MATERIALS AND METHODS

Information on the toxicity and safety control of PCHM, as well as PCHM-derived anti-cancer compounds, was gathered from the articles, books and monographs published in the past 20 years.

RESULTS

Based on an objective introduction to the CHM toxicity, we clarified the general misconceptions about the safety of CHM and summarized the traditional experiences in dealing with the toxicity. Several PCHM-derived compounds, namely gambogic acid, triptolide, arsenic trioxide, and cantharidin, were selected as representatives, and their traditional usage and mechanism of anti-cancer actions were discussed.

CONCLUSIONS

Natural products derived from PCHM are of extreme importance in devising new drugs and providing unique ideas for the war against cancer. To fully exploit the potential of PCHM in cancer therapy, more attentions are advocated to be focused on their safety evaluation and mechanism exploration.

Anticancer drugs from traditional toxic Chinese medicines

Many anticancer drugs are obtained from natural sources. Nature produces a variety of toxic compounds, which are often used as anticancer drugs. Up to now, there are at least 120 species of poisonous botanicals, animals and minerals, of which more than half have been found to possess significant anticancer properties. In spite of their clinical toxicity, they exhibit pharmacological effects and have been used as important traditional Chinese medicines for the different stages of cancer. The article reviews many structures such as alkaloids of Camptotheca acuminata, Catharanthus roseus and Cephalotaxus fortunei, lignans of Dysosma versipellis and Podophyllum emodi, ketones of Garcinia hanburyi, terpenoids of Mylabris and Ginkgo biloba, diterpenoids of Tripterygium wilfordii, Euphorbia fischeriana, Euphorbia lathyris, Euphorbia kansui, Daphne genkwa, Pseudolarix kaempferi and Brucea javanica, triterpenoids of Melia toosendan, steroids of Periploca sepium, Paris polyphylla and Venenum Bufonis, and arsenic compounds including Arsenicum and Realgar. By comparing their related phytochemistry, toxic effects and the recent advances in understanding the mechanisms of action, this review puts forward some ideals and examples about how to increase antitumour activity and/or reduce the side effects experienced with Chinese medicine.

Optimization of extracellular glucan production from Pleurotus eryngii and its impact on angiogenesis

Pleurotus eryngii, an edible mushroom with therapeutic potential was optimized using response surface methodology of four-factor Box-Behnken design for maximum mycelial biomass and extracellular glucan (EPS) production. The model predicts to gain a maximal mycelial biomass and extracellular polysaccharide at 39.4 g/l; 36.04 g/l of glucose, 8.27 g/l; 7.51 g/l of yeast extract, pH 6.99; 7.07 and temperature 26.2°C; 25.84°C, respectively. The validation experiments showed that the model was significant and in close agreement with the model prediction. The evaluation of extracellular polysaccharide on angiogenesis by ex vivo CAM assay showed that there was significant inhibition in neo-vascularization.

Recent advances in hypoxia-inducible factor (HIF)-1 inhibitors

Tumor hypoxia has been recognized as a common feature of solid tumors and a negative prognostic factor for response to treatment and survival of cancer patients. The discovery of hypoxia-inducible factor-1 (HIF-1), a molecular determinant of responses to hypoxia in mammalian cells, has renewed enthusiasm for discovery and development of targeted therapies exploiting the hypoxic tumor microenvironment. HIF-1 activity in tumors depends on availability of the HIF-1α subunit, the levels of which increase under hypoxic conditions and through activation of oncogenes and/or inactivation of tumor suppressor genes. Increased HIF-1 has been correlated with increased angiogenesis, aggressive tumor growth, and poor patient prognosis, leading to current interest in HIF-1 as promising anticancer drug target. In spite of an ever increasing number of putative small molecule inhibitors of HIF-1, only a few are progressing through preclinical and early clinical development. In this review, we will discuss recent advances in discovery and development of small molecule inhibitors that target the HIF-1 pathway as potential anticancer agents.

Cyclin-dependent kinase inhibitor, P276-00, inhibits HIF-1α and induces G2/M arrest under hypoxia in prostate cancer cells

BACKGROUND

Hypoxia-inducible factor-1 (HIF-1) is a master regulator of the transcriptional response to oxygen deprivation and controls genes involved in glycolysis, angiogenesis, migration and invasion. Overexpression of HIF-1α has been demonstrated in many common human cancers.

METHODS

Luciferase reporter gene assay under hypoxia and normoxia was used to demonstrate transcriptional inhibition of HIF-1 by P276-00. Detailed studies such as western blotting, reverse-transcriptase-PCR and immunofluorescence were carried out to elucidate its mechanism of action. Cytotoxic potential of P276-00 under normoxia and hypoxia was determined on prostate cancer cells using CCK-8 assay, and cell-cycle analysis was carried out using flow cytometry. Antiangiogenic activity of P276-00 was demonstrated by migration assay and tube-formation assay. Efficacy study of P276-00 was performed in a PC-3 xenograft model.

RESULTS

P276-00 inhibits transcriptional activation of HIF-1 under hypoxia. It suppressed hypoxia-mediated nuclear HIF-1α expression, as well as phosphorylation of Akt and 4E-BP1 and abrogated expression of HIF-1-inducible gene viz. vascular endothelial growth factor. Under hypoxia, P276-00 did not exhibit enhanced cytotoxic activity in prostate cancer cells but arrested them in the G2/M phase of the cell cycle. The tubular formation of human umbilical vein endothelial cells and migration of prostate cancer cells were also inhibited by P276-00 in vitro. In addition, it demonstrated significant in vivo efficacy in the PC-3 xenograft model.

CONCLUSIONS

Given its low toxicity profile, its demonstrated antitumor activity and its potential to inhibit the HIF-1 pathway, P276-00 should be considered as antiangiogenic chemotherapy for prostate cancer.

MFTZ-1 reduces constitutive and inducible HIF-1α accumulation and VEGF secretion independent of its topoisomerase II inhibition

The macrolide compound MFTZ-1 has been identified as a novel topoisomerase II (Top2) inhibitor with potent in vitro and in vivo anti-tumour activities. In this study, we further examined the effects of MFTZ-1 on hypoxia-inducible factor-1α (HIF-1α) accumulation, vascular endothelial growth factor (VEGF) secretion and angiogenesis. MFTZ-1 reduced HIF-1α accumulation driven by hypoxia or growth factors in human cancer cells. Mechanistic studies revealed that MFTZ-1 did not affect the degradation of HIF-1α protein or the level of HIF-1α mRNA. By contrast, MFTZ-1 apparently inhibited constitutive and inducible activation of both phosphatidylinositol-3-kinase (PI3K)-Akt and p42/p44 mitogen-activated protein kinase (MAPK) pathways. Further studies revealed that MFTZ-1 abrogated the HIF-1α-driven increase in VEGF mRNA and protein secretion. MFTZ-1 also lowered the basal level of VEGF secretion. The results reveal an important feature that MFTZ-1 can reduce constitutive, HIF-1α-independent VEGF secretion and concurrently antagonize inducible, HIF-1α-dependent VEGF secretion. Moreover, MFTZ-1 disrupted tube formation of human umbilical vein endothelial cells (HUVECs) stimulated by hypoxia with low-concentration serum or by serum at normoxia, and inhibited HUVECs migration at normoxia. MFTZ-1 also prevented microvessel outgrowth from rat aortic ring. These data reflect the potent anti-angiogenesis of MFTZ-1 under different conditions. Furthermore, using specific small interfering RNA targeting Top2α or Top2-defective HL60/MX2 cells, we showed that MFTZ-1 affected HIF-1α accumulation and HUVECs tube formation irrelevant to its Top2 inhibition. Taken together, our data collectively reveal that MFTZ-1 reduces constitutive and inducible HIF-1α accumulation and VEGF secretion possibly via PI3K-Akt and MAPK pathways, eliciting anti-angiogenesis independently of its Top2 inhibition.

Q39, a quinoxaline 1,4-Di-N-oxide derivative, inhibits hypoxia-inducible factor-1α expression and the Akt/mTOR/4E-BP1 signaling pathway in human hepatoma cells

Cumulative evidence has established that hypoxia-inducible factor-1α (HIF-1α) and its downstream target, vascular endothelial growth factor (VEGF), play a critical role in hepatocellular carcinoma angiogenesis, invasiveness and metastasis. 3-(4-bromophenyl)-2-(ethylsulfonyl)-6-methylquinoxaline 1,4-dioxide (Q39) has recently shown great antiproliferative activity in extensive cell lines in normoxia and hypoxia. In this study, Q39 exhibited high antiproliferative activity against hepatoma both in vitro and in vivo, mainly by inducing apoptosis. In addition, suppression of HIF-1α by Q39 resulted in a drastic decrease in VEGF expression. These results indicate that Q39 is an effective inhibitor of HIF-1α and provide new perspectives into the mechanism of its anticancer activity. Interestingly, neither the HIF-1α degradation rate nor the HIF-1α steady-state mRNA level was affected by Q39. Instead, suppression of HIF-1α accumulation by Q39 correlated with prominent dephosphorylation of mTOR and 4E-BP1, a pathway known to regulate protein expression at the translational level.

Q39, a quinoxaline 1,4-Di-N-oxide derivative, inhibits hypoxia-inducible factor-1α expression and the Akt/mTOR/4E-BP1 signaling pathway in human hepatoma cells

Cumulative evidence has established that hypoxia-inducible factor-1α (HIF-1α) and its downstream target, vascular endothelial growth factor (VEGF), play a critical role in hepatocellular carcinoma angiogenesis, invasiveness and metastasis. 3-(4-bromophenyl)-2-(ethylsulfonyl)-6-methylquinoxaline 1,4-dioxide (Q39) has recently shown great antiproliferative activity in extensive cell lines in normoxia and hypoxia. In this study, Q39 exhibited high antiproliferative activity against hepatoma both in vitro and in vivo, mainly by inducing apoptosis. In addition, suppression of HIF-1α by Q39 resulted in a drastic decrease in VEGF expression. These results indicate that Q39 is an effective inhibitor of HIF-1α and provide new perspectives into the mechanism of its anticancer activity. Interestingly, neither the HIF-1α degradation rate nor the HIF-1α steady-state mRNA level was affected by Q39. Instead, suppression of HIF-1α accumulation by Q39 correlated with prominent dephosphorylation of mTOR and 4E-BP1, a pathway known to regulate protein expression at the translational level.

Huperzine a improves chronic inflammation and cognitive decline in rats with cerebral hypoperfusion

Chronic cerebral hypoperfusion has been suggested to contribute to the progression of dementia. Inflammation and white matter lesion (WML) are involved in the pathologic process. This study investigated whether huperzine A, a natural acetylcholinesterase (AChE) inhibitor, has beneficial effects on long-lasting inflammation as well as cognitive impairment in a rat model of cerebral hypoperfusion and how it plays these roles. Chronic cerebral hypoperfusion was induced by occlusion of bilateral common carotid arteries (two-vessel occlusion; 2VO). Huperzine A was initially given 150 min after 2VO and daily for 3, 7, 14, and 28 days. Learning and memory dysfunction as tested by Morris water maze performance was observed in 2VO-operated rats and was significantly improved by huperzine A treatment. WML and activation staining of immune cells were evaluated by Klüver-Barrera (KB) and immunohistochemistry, respectively. Myelin damage and increased immunostains were found in optic tract at all indicated days. Huperzine A treatment significantly ameliorated all these phenomena. Moreover, huperzine A also suppressed overexpression of the inflammatory factor tumor necrosis factor-alpha (TNF-alpha) and overphosphorylation of JNK and p38 mitogen-activated protein kinases (MAPKs) in a cell model of chronic hypoxia. Preincubation with mecamylamine (MEC), a nicotinic acetylcholine receptor (nAChR) antagonist, for 30 min before hypoxia notably reversed the effects of huperzine A on TNF-alpha production and MAPKs phosphorylation. In conclusion, delayed and chronic administration of huperzine A could protect against 2VO-induced cognitive impairment, which might be related to its beneficial effects on WML, and the nAChR-dependent cholinergic anti-inflammation pathway plays an important role.