Triptolide inhibits MDM2 and induces apoptosis in acute lymphoblastic leukemia cells through a p53-independent pathway

Minnelide exhibits antileukemic activity by targeting the Ars2/miR-190a-3p axis

BACKGROUND

The identification of a novel and effective strategy for the clinical treatment of acute leukemia (AL) is a long-term goal. Minnelide, a water-soluble prodrug of triptolide, has recently been evaluated in phase I and II clinical trials in patients with multiple cancers and has shown promise as an antileukemic agent. However, the molecular mechanism underlying minnelide's antileukemic activity remains unclear.

PURPOSE

To explore the molecular mechanisms by which minnelide exhibits antileukemic activity.

METHODS

AL cells, primary human leukemia cells, and a xenograft mouse model were treated with triptolide and minnelide. The molecular mechanism was elucidated using western blotting, immunoprecipitation, flow cytometry, GSEA and liquid chromatography-mass spectrometry analysis.

RESULTS

Minnelide was highly effective in inhibiting leukemogenesis and improving survival in two complementary AL mouse models. Triptolide, an active form of minnelide, causes cell cycle arrest in G1 phase and induces apoptosis in both human AL cell lines and primary AL cells. Mechanistically, we identified Ars2 as a new chemotherapeutic target of minnelide for AL treatment. We found that triptolide directly targeted Ars2, resulting in the downregulation of miR-190a-3p, which led to the disturbance of PTEN/Akt signaling and culminated in G1 cell cycle arrest and apoptosis.

CONCLUSIONS

Our findings demonstrate that targeting Ars2/miR-190a-3p signaling using minnelide could represent a novel chemotherapeutic strategy for AL treatment and support the evaluation of minnelide for the treatment of AL in clinical trials.

Triptolide promotes differentiation of human monocytes into immunosuppressive MDSCs

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) negatively modulate immune activity. Prior investigations have shown much promise in using MDSCs-assisted immunotherapy for organ transplantation patients. Additionally, owing to its immunosuppressive activity, MDSCs can also be used to manage immune-associated disorders.

METHODS

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was employed to stimulate myeloid progenitor cell differentiation. Triptolide (PG490) was introduced toward the later phases of in vitro MDSCs induction. Lastly, real-time PCR (RT-PCR) and flow cytometry were used to assess transcript expression and cell phenotype, and a mouse skin transplantation model was established to evaluate the MDSCs-mediated immune suppression in vivo.

RESULTS

Co-stimulation with PG490 and GM-CSF potently induced myeloid-derived monocytes to form MDSCs, with remarkable immune-suppressive activity. The underlying mechanism involved downregulation of T cell proliferation, activation, enhancement of inflammatory cytokine release, as well as T cell conversion to Treg cells. PG490 strongly enhanced iNOS expression in MDSCs, and iNOS inhibition successfully reversed the immune-suppression. The PG490- and GM-CSF-induced MDSCs substantially extended survival duration of murine skin grafts, thereby validating their strong immune-suppressive activity in vivo.

CONCLUSIONS

Herein, we presented a new approach involving MDSCs-based immunosuppression in vitro. PG490 and GM-CSF co-treatment strongly induced immuno-suppressive activity in MDSCs both in vitro and in vivo. Our findings highlight the promise of applying MDSCs-based therapy in clinical organ transplantation treatment.

Mechanisms of cancer cell death induction by triptolide: A comprehensive overview

The need for naturally occurring constituents is driven by the rise in the cancer prevalence and the unpleasant side effects associated with chemotherapeutics. Triptolide, the primary active component of "Tripterygium Wilfordii", has exploited for biological mechanisms and therapeutic potential against various tumors. Based on the recent pre-clinical investigations, triptolide is linked to the induction of death of cancerous cells by triggering cellular apoptosis via inhibiting heat shock protein expression (HSP70), and cyclin dependent kinase (CDKs) by up regulating expression of P21. MKP1, histone methyl transferases and RNA polymerases have all recently identified as potential targets of triptolide in cells. Autophagy, AKT signaling pathway and various pathways involving targeted proteins such as A-disintegrin & metalloprotease-10 (ADAM10), Polycystin-2 (PC-2), dCTP pyro-phosphatase 1 (DCTP1), peroxiredoxin-I (Prx-I), TAK1 binding protein (TAB1), kinase subunit (DNA-PKcs) and the xeroderma-pigmentosum B (XPB or ERCC3) have been exploited. Besides that, triptolide is responsible for enhancing the effectiveness of various chemotherapeutics. In addition, several triptolide moieties, including minnelide and LLDT8, have progressed in investigations on humans for the treatment of cancer. Targeted strategies, such as triptolide conjugation with ligands or triptolide loaded nano-carriers, are efficient techniques to confront toxicities associated with triptolide. We expect and anticipate that advances in near future, regarding combination therapies of triptolide, might be beneficial against cancerous cells.

Mechanisms of cancer cell death induction by triptolide

Drug resistance is a hot topic issue in cancer research and therapy. Although cancer therapy including radiotherapy and anti-cancer drugs can kill malignant cells within the tumor, cancer cells can develop a wide range of mechanisms to resist the toxic effects of anti-cancer agents. Cancer cells may provide some mechanisms to resist oxidative stress and escape from apoptosis and attack by the immune system. Furthermore, cancer cells may resist senescence, pyroptosis, ferroptosis, necroptosis, and autophagic cell death by modulating several critical genes. The development of these mechanisms leads to resistance to anti-cancer drugs and also radiotherapy. Resistance to therapy can increase mortality and reduce survival following cancer therapy. Thus, overcoming mechanisms of resistance to cell death in malignant cells can facilitate tumor elimination and increase the efficiency of anti-cancer therapy. Natural-derived molecules are intriguing agents that may be suggested to be used as an adjuvant in combination with other anticancer drugs or radiotherapy to sensitize cancer cells to therapy with at least side effects. This paper aims to review the potential of triptolide for inducing various types of cell death in cancer cells. We review the induction or resistance to different cell death mechanisms such as apoptosis, autophagic cell death, senescence, pyroptosis, ferroptosis, and necrosis following the administration of triptolide. We also review the safety and future perspectives for triptolide and its derivatives in experimental and human studies. The anticancer potential of triptolide and its derivatives may make them effective adjuvants for enhancing tumor suppression in combination with anticancer therapy.

Upregulation of p53 through induction of MDM2 degradation: improved potency through the introduction of an alkylketone sidechain on the anthraquinone core

Overexpression of ubiquitin ligase MDM2 causes depletion of the p53 tumour-suppressor and thus leads to cancer progression. In recent years, anthraquinone analogs have received significant attention due to their ability to downregulate MDM2, thereby promoting p53-induced apoptosis. Previously, we have developed potent anthraquinone compounds having the ability to upregulate p53 via inhibition of MDM2 in both cell culture and animal models of acute lymphocytic leukaemia. Earlier work was focussed on mechanistic work, pharmacological validation of this class of compounds in animal models, and mapping out structural space that allows for further modification and optimisation. Herein, we describe our work in optimising the substituents on the two phenol hydroxyl groups. It was found that the introduction of an alkylketone moiety led to a potent series of analogs with BW-AQ-350 being the most potent compound yet (IC₅₀ = 0.19 ± 0.01 µM) which exerts cytotoxicity by inducing MDM2 degradation and p53 upregulation.

Two Species Origins Comparison of Herba Patriniae based on Their Ingredients Profile by UPLC-QTOF/MS/MS and Orthogonal Partial Least Squares Discriminant Analysis

Herba Patriniae (HP) is widely used as a medicinal and edible material in China. Besides food value, HP attracts more attention due to its medicinal potential. Patrinia villosa Juss. ( PV ) and Patrinia scabiosaefolia Fisch. ( PS ) are the two species origins of HP. These two of HP show different effects on cell proliferation, migration, angiogenesis and anti-diabetic. As we have previously reported, PV and PS show significant differences on their anti-inflammatory ability in the same experimental model. Comparing the ingredient profiles of two different sources will not only facilitate the understanding of their medicinal effects, but also help the development and research of new activities. However, still now, there is no systematic and detailed study to compare the components of PV and PS . In present study, ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was employed to achieve a high-throughput qualitative and thorough analysis of the chemical composition spectrum of HP. A total of 164 compounds were identified, among these compounds, 127 compounds were identified from PV , and 107 compounds were identified from PS . Most of the chemical components was discovered for the first time. Flavonoids, saponins, terpenoids and organic acids, as the main ingredients in PV and PS were 45.45%vs 28.46%, 12.61% vs 32.09%, 14.33% vs 22.38% and 14.58% vs 6.79%, respectively. Flavonoids are the main components of PV , while PS is rich in saponins. PV and PS were classified into two groups by principal component analysis (PCA) and screened out the main molecular differences responsible by orthogonal partial least squares discriminant analysis (OPLS-DA). All the results will be a guide for the quality control, functional activity research, or better clinic use based on the ingredients profile between these two species. Besides, this first study on ingredients profile of two species origins will be beneficial for potential and best resources utilization of both PV and PS .

Hinokiflavone, as a MDM2 inhibitor, activates p53 signaling pathway to induce apoptosis in human colon cancer HCT116 cells

Hinokiflavone (HF), a natural biflavonoid that possesses various biological activities, has reported that HF could be a pre-mRNA splicing modulator, whereas its underlying mechanisms remain elusive. In the present study, we identified HF as a potential MDM2 inhibitor. What's more, we found that HF suppressed mdm2 mRNA synthesis at the transcriptional level. Then, this MDM2 inhibition led in turn to increase p53 protein expression and activate p53 pathway, which could decrease the survival of HCT116 colon cells by G2/M phase arrest and apoptosis induction. Then, bioinformatics suggested that ESR1 was a predicted and potential target of HF. Finally, we used molecular docking and molecular dynamics simulation to demonstrate the binding patterns of HF and ESR1. To sum up, our study unearthed that HF was a feasible agent for MDM2 inhibitor through down-regulating mdm2 RNA level and activating p53 signaling pathway.

A Balancing Act: p53 Activity from Tumor Suppression to Pathology and Therapeutic Implications

TP53, encoding the p53 transcription factor, is the most frequently mutated tumor suppressor gene across all human cancer types. While p53 has long been appreciated to induce antiproliferative cell cycle arrest, apoptosis, and senescence programs in response to diverse stress signals, various studies in recent years have revealed additional important functions for p53 that likely also contribute to tumor suppression, including roles in regulating tumor metabolism, ferroptosis, signaling in the tumor microenvironment, and stem cell self-renewal/differentiation. Not only does p53 loss or mutation cause cancer, but hyperactive p53 also drives various pathologies, including developmental phenotypes, premature aging, neurodegeneration, and side effects of cancer therapies. These findings underscore the importance of balanced p53 activity and influence our thinking of how to best develop cancer therapies based on modulating the p53 pathway. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Natural compounds in the regulation of proteostatic pathways: An invincible artillery against stress, ageing, and diseases

Cells have different sets of molecules for performing an array of physiological functions. Nucleic acids have stored and carried the information throughout evolution, whereas proteins have been attributed to performing most of the cellular functions. To perform these functions, proteins need to have a unique conformation and a definite lifespan. These attributes are achieved by a highly coordinated protein quality control (PQC) system comprising chaperones to fold the proteins in a proper three-dimensional structure, ubiquitin-proteasome system for selective degradation of proteins, and autophagy for bulk clearance of cell debris. Many kinds of stresses and perturbations may lead to the weakening of these protective cellular machinery, leading to the unfolding and aggregation of cellular proteins and the occurrence of numerous pathological conditions. However, modulating the expression and functional efficiency of molecular chaperones, E3 ubiquitin ligases, and autophagic proteins may diminish cellular proteotoxic load and mitigate various pathological effects. Natural medicine and small molecule-based therapies have been well-documented for their effectiveness in modulating these pathways and reestablishing the lost proteostasis inside the cells to combat disease conditions. The present article summarizes various similar reports and highlights the importance of the molecules obtained from natural sources in disease therapeutics.

Natural product triptolide induces GSDME-mediated pyroptosis in head and neck cancer through suppressing mitochondrial hexokinase-ΙΙ

Background

Pyroptosis is a lytic cell death form executed by gasdermins family proteins. Induction of tumor pyroptosis promotes anti-tumor immunity and is a potential cancer treatment strategy. Triptolide (TPL) is a natural product isolated from the traditional Chinese herb which possesses potent anti-tumor activity in human cancers. However, its role in pyroptosis remains to be elucidated.

Methods

Cell survival was measured by colony formation assay. Cell apoptosis was determined by Annexin V assay. Pyroptosis was evaluated by morphological features and release of interleukin 1β and lactate dehydrogenase A (LDHA). Immunofluorescence staining was employed to measure subcellular localization of proteins. Tumorigenicity was assessed by a xenograft tumor model. Expression levels of mRNAs or proteins were determined by qPCR or western blot assay, respectively.

Results

Triptolide eliminates head and neck cancer cells through inducing gasdermin E (GSDME) mediated pyroptosis. Silencing GSDME attenuates the cytotoxicity of TPL against cancer cells. TPL treatment suppresses expression of c-myc and mitochondrial hexokinase II (HK-II) in cancer cells, leading to activation of the BAD/BAX-caspase 3 cascade and cleavage of GSDME by active caspase 3. Silencing HK-II sensitizes cancer cells to TPL induced pyroptosis, whereas enforced expression of HK-II prevents TPL induced pyroptosis. Mechanistically, HK-II prevents mitochondrial translocation of BAD, BAX proteins and activation of caspase 3, thus attenuating cleavage of GSDME and pyroptosis upon TPL treatment. Furthermore, TPL treatment suppresses NRF2/SLC7A11 (also known as xCT) axis and induces reactive oxygen species (ROS) accumulation, regardless of the status of GSDME. Combination of TPL with erastin, an inhibitor of SLC7A11, exerts robust synergistic effect in suppression of tumor survival in vitro and in a nude mice model.

Conclusions

This study not only provides a new paradigm of TPL in cancer therapy, but also highlights a crucial role of mitochondrial HK-II in linking glucose metabolism with pyroptosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01995-7.

Minnelide, a prodrug, inhibits cervical cancer growth by blocking HPV-induced changes in p53 and pRb

HPV-induced cervical cancer is one of the prevalent gynecological cancers world-wide. In the present study, we determined the efficacy of Minnelide, a prodrug which is converted to its active form (Triptolide) in vivo against cervical cancer cells. Our studies show that Triptolide inhibited HPV-16 and HPV-18 positive cells at nanomolar concentrations. Tumor cells treated with Triptolide failed to grow in 3-D cultures in a concentration-dependent manner. Triptolide markedly reduced E6 and E7 transcript levels. Further studies revealed that exposure to Triptolide increased the levels of p53 and pRb. As a consequence, Caspase-3/7 activation and apoptosis was induced in cervical cancer cells by Triptolide. Subsequently, we evaluated the efficacy of Minnelide in xenotransplantation models of cervical cancer. Minnelide at very low doses effectively inhibited the growth of established cervical cancers in all the three animal models tested. Furthermore, Minnelide treatment was more effective when combined with platinum-based chemotherapy. These studies show that Minnelide can be used to inhibit the growth of cervical cancer.

Discovery of novel candidates for anti-liposarcoma therapies by medium-scale high-throughput drug screening

Sarcomas are a heterogeneous group of mesenchymal orphan cancers and new treatment alternatives beyond traditional chemotherapeutic regimes are much needed. So far, tumor mutation analysis has not led to significant treatment advances, and we have attempted to bypass this limitation by performing direct drug testing of a library of 353 anti-cancer compounds that are either FDA-approved, in clinical trial, or in advanced stages of preclinical development on a panel of 13 liposarcoma cell lines. We identified and validated six drugs, targeting different mechanisms and with good efficiency across the cell lines: MLN2238 –a proteasome inhibitor, GSK2126458 –a PI3K/mTOR inhibitor, JNJ-26481585 –a histone deacetylase inhibitor, triptolide–a multi-target drug, YM155 –a survivin inhibitor, and APO866 (FK866)–a nicotinamide phosphoribosyl transferase inhibitor. GR50s for those drugs were mostly in the nanomolar range, and in many cases below 10 nM. These drugs had long-lasting effect upon drug withdrawal, limited toxicity to normal cells and good efficacy also against tumor explants. Finally, we identified potential genomic biomarkers of their efficacy. Being approved or in clinical trials, these drugs are promising candidates for liposarcoma treatment.

Testis Toxicants: Lesson from Traditional Chinese Medicine (TCM)

The testis is one of the organs in the mammalian body that is sensitive to toxicants. Accumulating evidence has shown that human exposure to toxic ingredients in Traditional Chinese Medicine (TCM), such as triptolide, gossypol, cannabidol, piperine, α-solanine, matrine, aristolochic acid, and emodin, lead to testis injury and reproductive dysfunction. The most obvious phenotype is reduced sperm counts due to defects in spermatogenesis. Studies have also shown that Sertoli cells in the seminiferous tubule, the functional unit of the testis that supports spermatogenesis, are the cell type that is most sensitive to the disruptive effects of toxicants. Since Sertoli cells are the "mother cells" that nurture germ cell development, Sertoli cell injury thus leads to failure in germ cell development in the seminiferous epithelium. Mounting evidence has shown that the Sertoli cell cytoskeletons, mitochondria function, Leydig cells steroidogenesis pathways and sperm ion channels are some of the prime targets of toxicants from TCM. We carefully evaluate recent findings in this area of research herein, and to provide a summary of these findings, including some insightful information regarding the underlying molecular basis of toxicant-induced testis injury that impede spermatogenesis.

Network pharmacology-based strategy for predicting therapy targets of Tripterygium wilfordii on acute myeloid leukemia

This is a study on the potential therapeutic targets and pharmacological mechanism of Tripterygium wilfordii (TW) in acute myeloid leukemia (AML) based on network pharmacology.Active components of TW were obtained by network pharmacology through oral bioavailability, drug-likeness filtration. Comparative analysis was used to investigate the overlapping genes between active ingredient's targets and AML treatment-related targets. Using STRING database to analyze interactions among overlapping genes. Both KEGG pathway analysis and Gene Ontology enrichment analysis were conducted in DAVID. These genes were analyzed for survival in OncoLnc database.We screened 53 active ingredients; the results of comparative analysis showed that 8 active ingredients had an effect on AML treatment. On the basis of the active ingredients and overlapping genes, we constructed the Drug-Compounds-Genes-Disease Network. Survival analysis of overlapping genes indicated that some targets possessed a significant influence on patients' survival and prognosis. The enrichment analysis showed that the main pathways of targets were Toll-like receptor signaling pathway, NF-kappa B signaling pathway, and HIF-1 signaling pathway.This study, using a network pharmacologic approach, provides another strategy that can help us to understand the mechanisms by which TW treats AML comprehensively.

Triptolide enhances lipolysis of adipocytes by enhancing ATGL transcription via upregulation of p53

Lipolysis is an essential physiological activity of adipocytes. The Patatin Like Phospholipase Domain Containing 2 (PNPLA2) gene encodes the enzyme adipose triglyceride lipase (ATGL) responsible for triglyceride hydrolysis, the first step in lipolysis. In this study, we investigated the potential of triptolide (TP), a natural plant extract, to induce weight loss by examining its effect on ATGL expression. We found that long- and short-term TP administration reduced body weight and fat weight and increased heat production in brown adipose tissue in wild-type C57BL/6 mice. In 3T3-L1 fibroblasts and porcine adipocytes, TP treatment reduced the number of lipid droplets as determined by Oil Red O and BODIPY staining, with concomitant increases in free fatty acid and triglyceride levels in the culture medium. Combined treatment with TP and p53 inhibitor reversed these lipolytic effects. We next amplified the ATGL promoter region and identified conserved p53 binding sites in the sequence by in silico analysis. The results of the dual-luciferase reporter assay using a construct containing the ATGL promoter harboring the p53 binding site showed that p53 induces ATGL promoter activity and consequently, ATGL transcription. These results demonstrate that TP has therapeutic value as an anti-obesity agent and acts by promoting lipolysis via upregulation of p53 and ATGL transcription.

Preclinical Pharmacokinetics of Triptolide: A Potential Antitumor Drug

Background:

Triptolide, a bioactive component in Tripterygium wilfordii extracts, possess strong antiproliferative activity on all 60-National Cancer Institute (NCI) cancer cell lines. However, the widespread use of triptolide in the clinical practice is greatly limited for its multi-organ toxicity and narrow therapeutic window. All the toxic characteristics of triptolide are associated with the pharmacokinetics especially its distribution and accumulation in the target organ.

Methods:

The literature review was done using PubMed search, SciFinder and Google Scholar databases with specific keywords such as triptolide, pharmacokinetics, drug-drug interaction, transporters, metabolism, modification to collect the related full-length articles and abstracts from 2000 to 2018.

Results:

Oral triptolide is rapidly and highly absorbed. Grapefruit juice affects oral absorption, increasing the area under the concentration-time curve (AUC) by 153 % and the maximum concentration (Cmax) by 141 %. The AUC and the Cmax are not dose proportional. Triptolide distributes into the liver, heart, spleen, lung and kidney. Biotransformation of triptolide in rats includes hydroxylation, sulfate, glucuronide, N-acetylcysteine (NAC) and Glutathione (GSH) conjugation and combinations of these pathways. Less than 4 % of triptolide was recovered from the feces, bile and urine within 24 h. After repeating dosage, triptolide was eliminated quickly without accumulation in vivo. As a substrate of P-glycoprotein (P-gp) and CYP3A4, triptolide could have clinically significant pharmacokinetic interactions with those proteins substrates/inhibitors.

Conclusion:

The findings of this review confirm the importance of pharmacokinetic character for understanding the pharmacology and toxicology of triptolide.

The roles of radio-functional natural chemicals for the development of cancer radiation therapy

Ionizing radiation (IR) targeted at killing cancer cells also damages normal human cells and tissues through oxidative stress. Thus, the practical treatment of cancer using radiation therapy (RT) is sometimes limited because of the acute side effects in individual patients. In addition, some radioresistant cancers are difficult to treat with limited doses of IR, which leads to treatment failure. Natural chemicals that have unique physiological functions and low toxicity offer significant advantages for the development of new radiation therapies. Natural chemicals can counteract the oxidative damage caused by IR during RT because of their strong antioxidant ability. Certain natural chemicals can also serve as radiosensitizers that can enhance the cancer-killing effects. This review article discusses the main roles of radio-functional natural chemicals in the development of cancer RT.

Natural products targeting the p53-MDM2 pathway and mutant p53: Recent advances and implications in cancer medicine

The p53 tumor suppressor plays a major role in controlling the initiation and development of cancer by regulating cell cycle arrest, apoptosis, senescence, and DNA repair. The MDM2 oncogene is a major negative regulator of p53 that inhibits the activity of p53 and reduces its protein stability. MDM2, p53, and the p53-MDM2 pathway represent well-documented targets for preventing and/or treating cancer. Natural products, especially those from medicinal and food plants, are a rich source for the discovery and development of novel therapeutic and preventive agents against human cancers. Many natural product-derived MDM2 inhibitors have shown potent efficacy against various human cancers. In contrast to synthetic small-molecule MDM2 inhibitors, the majority of which have been designed to inhibit MDM2-p53 binding and activate p53, many natural product inhibitors directly decrease MDM2 expression and/or MDM2 stability, exerting their anticancer activity in both p53-dependent and p53-independent manners. More recently, several natural products have been reported to target mutant p53 in cancer. Therefore, identification of natural products targeting MDM2, mutant p53, and the p53-MDM2 pathway can provide a promising strategy for the development of novel cancer chemopreventive and chemotherapeutic agents. In this review, we focus our discussion on the recent advances in the discovery and development of anticancer natural products that target the p53-MDM2 pathway, emphasizing several emerging issues, such as the efficacy, mechanism of action, and specificity of these natural products.

DUSP1 induces apatinib resistance by activating the MAPK pathway in gastric cancer

Dual-specificity phosphatase-1 (DUSP1) is an oncogene that is associated with cancer progression following drug resistance. In order to investigate the potential relationship between DUSP1 and apatinib resistance in gastric cancer cells, we preformed many assays to study this problem. DUSP1 gene was detected by RT-qPCR assay, proteins in MAPK pathway were quantified by western blot assay, and CCK-8 assay, flow cytometry and Hoechest 33342 stain were performed to detect the resistance of cells, cell cycles and apoptosis, respectively. Immunohistochemical staining was used to discover the expression of DUSP1 protein in patients' tumor or paratumor tissues. It was found that apatinib (Apa)-resistant gastric cancer (GC) cells showed increased expression of DUSP1, whereas the knockdown of DUSP1 in resistant cells resensitized these cells to Apa. The restored sensitivity to Apa was the result of inactivation of mitogen-activated protein kinase (MAPK) signaling and the induction of apoptosis. The in vitro use of Apa in combination with a DUSP1 inhibitor, triptolide, exerted significant effects on inhibiting the expression of DUSP1, growth inhibition, and apoptosis via the inactivation of MAPK signaling. In patients who did not undergo chemotherapy or targeted therapy, the expression of DUSP1 in adjacent tissues was higher when compared with that observed in tumor tissues. In addition, the expression of DUSP1 was higher in the early stages of GC than in the advanced stages. The expression of DUSP1 in tumor tissues was not associated with the survival rate of the patients. Therefore, increased expression of DUSP1 may be responsible for Apa resistance, and DUSP1 may serve as a biomarker for Apa efficacy. In conclusion, inducing the downregulation of DUSP1 may be a promising strategy to overcome Apa resistance.

Triptolide-induced mitochondrial damage dysregulates fatty acid metabolism in mouse sertoli cells

Triptolide is a major active ingredient of tripterygium glycosides, used for the therapy of immune and inflammatory diseases. However, its clinical applications are limited by severe male fertility toxicity associated with decreased sperm count, mobility and testicular injures. In this study, we determined that triptoide-induced mitochondrial dysfunction triggered reduction of lactate and dysregulation of fatty acid metabolism in mouse Sertoli cells. First, triptolide induced mitochondrial damage through the suppressing of proliferator-activated receptor coactivator-1 alpha (PGC-1α) activity and protein. Second, mitochondrial damage decreased lactate production and dysregulated fatty acid metabolism. Finally, mitochondrial dysfunction was initiated by the inhibition of sirtuin 1 (SIRT1) with the regulation of AMP-activated protein kinase (AMPK) in Sertoli cells after triptolide treatment. Meanwhile, triptolide induced mitochondrial fatty acid oxidation dysregulation by increasing AMPK phosphorylation. Taken together, we provide evidence that the mechanism of triptolide-induced testicular toxicity under mitochondrial injury may involve a metabolic change.

Triptolide has anticancer and chemosensitization effects by down-regulating Akt activation through the MDM2/REST pathway in human breast cancer

Triptolide has been shown to exhibit anticancer activity. However, its mechanism of action is not clearly defined. Herein we report a novel signaling pathway, MDM2/Akt, is involved in the anticancer mechanism of triptolide. We observed that triptolide inhibits MDM2 expression in human breast cancer cells with either wild-type or mutant p53. This MDM2 inhibition resulted in decreased Akt activation. More specifically, triptolide interfered with the interaction between MDM2 and the transcription factor REST to increase expression of the regulatory subunit of PI3-kinase p85 and consequently inhibit Akt activation. We further showed that, regardless of p53 status, triptolide inhibited proliferation, induced apoptosis, and caused G1 phase cell cycle arrest. Triptolide also enhanced the cytotoxic effect of doxorubicin. MDM2 inhibition plays a causative role in these effects. The inhibitory effect of triptolide on MDM2-mediated Akt activation was eliminated with MDM2 overexpression. MDM2-overexpressing tumor cells, in turn, were less susceptible to the anticancer and chemosensitization effects of triptolide than control cells. Triptolide also exhibited anticancer and chemosensitization effects in nude mouse xenograft model. When it was administered to tumor-bearing nude mice, triptolide inhibited tumor growth and enhanced the antitumor effects of doxorubicin. In summary, triptolide has anticancer and chemosensitization effects by down-regulating Akt activation through the MDM2/REST pathway in human breast cancer. Our study helps to elucidate the p53-independent regulatory function of MDM2 in Akt signaling, offering a novel view of the mechanism by which triptolide functions as an anticancer agent.

Aloin promotes A549 cell apoptosis via the reactive oxygen species‑mitogen activated protein kinase signaling pathway and p53 phosphorylation

Aloin has the potential to be a novel anticancer agent in cancer therapies. However, the detailed anticancer effect of Aloin remains to be fully elucidated. The present study analyzed the p53‑dependent mechanisms in response to Aloin treatment. Using the p53‑proficient A549 cells, an Aloin‑induced apoptotic cell model was established, which was used to evaluate the potential underlying molecular mechanisms. The results demonstrated that 200, 300 and 400 µM Aloin induced intrinsic cell apoptosis, which was further confirmed by disruption of the mitochondrial membrane potential, elevation of cytosolic Ca2+ levels, and activation of B‑cell lymphoma 2 (Bcl‑2) homologous antagonist killer, Bcl‑2 X‑associated protein, p53 upregulated modulator of apoptosis and phorbol‑12‑myristate‑13‑acetate‑induced protein 1. Aloin‑induced apoptosis was also accompanied by the induction of p53 phosphorylation on Serine (Ser)15, Threonine 18, Ser20 and Ser392; however, there were no significant differences in the expression of p53 and mouse double minute 2 homolog. Aloin‑induced apoptosis was reactive oxygen species (ROS)‑ and c‑Jun/p38‑dependent, as specific inhibitors for ROS, phosphorylated (p)‑c‑Jun and p‑p38 may attenuate Aloin‑induced A549 cell proliferating inhibition. In conclusion, these results suggested that Aloin may induce apoptosis in A549 cells via the ROS‑mitogen activated protein kinase signaling pathway, with p53 phosphorylation. These results implicate Aloin as a potential therapeutic agent for the treatment of lung cancer.

Discovery of Dual Inhibitors of MDM2 and XIAP for Cancer Treatment

MDM2 and XIAP are mutually regulated. Binding of MDM2 RING protein to the IRES region on XIAP mRNA results in MDM2 protein stabilization and enhanced XIAP translation. In this study, we developed a protein-RNA fluorescence polarization (FP) assay for high-throughput screening (HTS) of chemical libraries. Our FP-HTS identified eight inhibitors that blocked the MDM2 protein-XIAP RNA interaction, leading to MDM2 degradation. The compound-induced MDM2 downregulation resulted not only in inhibition of XIAP expression, but also in activation of p53, which contributed to cancer cell apoptosis in vitro and inhibition of cancer cell proliferation in vivo. Importantly, one of the MDM2/XIAP inhibitors, MX69, showed minimal inhibitory effect on normal human hematopoiesis in vitro and was very well tolerated in animal models.

MDM2 knockdown mediated by a triazine-modified dendrimer in the treatment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and the five-year survival rate is lower in advanced NSCLC patients. Chemotherapy is a widely used strategy in NSCLC treatment, but is usually limited by poor therapeutic efficacy and adverse effects. Therefore, a new therapeutic regimen is needed for NSCLC treatment. Gene therapy is a new strategy in the treatment of NSCLC. However, the lack of efficient and low toxic vectors remains the major obstacle. Here, we developed a biocompatible dendrimer as a non-viral vector for the delivery of mouse double minute2 (MDM2) siRNA in vitro and in vivo to treat NSCLC. The triazine-modified dendrimer efficiently stimulates the down-regulation of MDM2 gene in NSCLC PC9 cells, which induces significant cell apoptosis through the activation of apoptosis markers such as caspase-8 and poly(ADP-ribose) polymerase (PARP) cleavage. Furthermore, the dendrimer/MDM2 siRNA polyplexes showed excellent activity in the inhibition of tumor growth in a PC9 xenograft tumor model. These results suggested that inhibition the expression of MDM2 might be a potential target in NSCLC treatment.

Clinical Overview of MDM2/X-Targeted Therapies

MDM2 and MDMX are the primary negative regulators of p53, which under normal conditions maintain low intracellular levels of p53 by targeting it to the proteasome for rapid degradation and inhibiting its transcriptional activity. Both MDM2 and MDMX function as powerful oncogenes and are commonly over-expressed in some cancers, including sarcoma (~20%) and breast cancer (~15%). In contrast to tumors that are p53 mutant, whereby the current therapeutic strategy restores the normal active conformation of p53, MDM2 and MDMX represent logical therapeutic targets in cancer for increasing wild-type (WT) p53 expression and activities. Recent preclinical studies suggest that there may also be situations that MDM2/X inhibitors could be used in p53 mutant tumors. Since the discovery of nutlin-3a, the first in a class of small molecule MDM2 inhibitors that binds to the hydrophobic cleft in the N-terminus of MDM2, preventing its association with p53, there is now an extensive list of related compounds. In addition, a new class of stapled peptides that can target both MDM2 and MDMX have also been developed. Importantly, preclinical modeling, which has demonstrated effective in vitro and in vivo killing of WT p53 cancer cells, has now been translated into early clinical trials allowing better assessment of their biological effects and toxicities in patients. In this overview, we will review the current MDM2- and MDMX-targeted therapies in development, focusing particularly on compounds that have entered into early phase clinical trials. We will highlight the challenges pertaining to predictive biomarkers for and toxicities associated with these compounds, as well as identify potential combinatorial strategies to enhance its anti-cancer efficacy.

MiR-194, commonly repressed in colorectal cancer, suppresses tumor growth by regulating the MAP4K4/c-Jun/MDM2 signaling pathway

Tumor growth cascade is a complicated and multistep process with numerous obstacles. Until recently, evidences have shown the involvement of microRNAs (miRNAs) in tumorigenesis and tumor progression of various cancers, including colorectal cancer (CRC). In this study, we explored the role of miR-194 and its downstream pathway in CRC. We acquired data through miRNA microarray profiles, showing that the expression of miR-194 was significantly suppressed in CRC tissues compared with corresponding noncancerous tissues. Decreased miR-194 expression was obviously associated with tumor size and tumor differentiation, as well as TNM stage. Both Kaplan-Meier and multivariate survival analysis showed that downregulated miR-194 was associated with overall survival. Moreover, functional assays indicated that overexpression of miR-194 in CRC cell lines inhibited cell proliferation both in vitro and in vivo. In addition, using dual-luciferase reporter gene assay, we found MAP4K4 was the direct target of miR-194. Silencing of MAP4K4 resulted in similar biological behavior changes to that of overexpression of miR-194. We also observed through Human Gene Expression Array that MDM2 was one of the downstream targets of MAP4K4. Knockdown of MAP4K4 downregulated MDM2 expression through transcription factor c-Jun binding to the -1063 to -1057 bp of the promoter. These results suggest that miR-194, regulating the MAP4K4/c-Jun/MDM2 signaling pathway, might act as a tumor suppressor and serve as a novel target for CRC prevention and therapy.

Triptolide disrupts fatty acids and peroxisome proliferator-activated receptor (PPAR) levels in male mice testes followed by testicular injury: A GC-MS based metabolomics study

Triptolide is the major active ingredient of Tripterygium Glycosides (TG), a traditional Chinese medicine with very potent anti-inflammatory effects and has been used in China for the treatment of rheumatoid arthritis and many other inflammatory diseases. However, clinical application of triptolide is restricted due to its multiple side effects, especially male infertility. The mechanism of triptolide on reproduction toxicity remains unclear. In the present study, a GC-MS based metabolomic approach was employed to evaluate the mechanism of triptolide-induced reproductive toxicity as well as identify potential novel biomarkers for the early detection of spermatogenesis dysfunction. In brief, male mice were divided into two groups with or without triptolide intraperitoneal injection at 60 μg/kg/day for 2 weeks and toxic effect of triptolide on testicular tissues were examined by biochemical indicator analysis, testis histopathologic analysis, and sperm quantity analysis. Metabolomics technology was then performed to evaluate systematically the endogenous metabolites profiling. Our results demonstrated that triptolide suppressed the marker-enzymes of spermatogenesis and testosterone levels, decreased sperm counts, reduced the gonad index and destroyed the microstructure of testis. Multivariate data analysis revealed that mice with triptolide induced testicular toxicity could be distinctively differentiated from normal animals and 35 and 39 small molecule metabolites were changed significantly in testis and serum, respectively (Fold-changes >1.5, P<0.05), in triptolide-treated mice. Abnormal level of fatty acids, an important energy source of sertoli cells with critical role in maintaining normal function of the testis tissue, was observed in triptolide-treated mice. Additionally, the protein expressions of PPAR, a transcription factor known to play a pivotal role in lipid and energy metabolism was significantly decreased in the testis tissue of triptolide-treated mice. In summary, our study represents the first comprehensive GC-MS based metabolomics analysis of triptolide-induced testicular toxicity. We reported for the first time that exposure to triptolide led to marked changes of a panel of endogenous metabolites in both testis and serum. The impairment of spermatogenesis may be caused by abnormal lipid and energy metabolism in testis via the down-regulation of PPARs mediated by triptolide. The presence of research suggested that PPARs and its related fatty acids metabolism may serve as potential targets for intervention or treatment of male infertility induced by triptolide.

Genome-wide association analysis identified splicing single nucleotide polymorphism in CFLAR predictive of triptolide chemo-sensitivity

Background

Triptolide is a therapeutic diterpenoid derived from the Chinese herb Tripterygium wilfordii Hook f. Triptolide has been shown to induce apoptosis by activation of pro-apoptotic proteins, inhibiting NFkB and c-KIT pathways, suppressing the Jak2 transcription, activating MAPK8/JNK signaling and modulating the heat shock responses.

Results

In the present study, we used lymphoblast cell lines (LCLs) derived from 55 unrelated Caucasian subjects to identify genetic markers predictive of cellular sensitivity to triptolide using genome wide association study. Our results identified SNPs on chromosome 2 associated with triptolide IC₅₀ (p < 0.0001). This region included biologically interesting genes as CFLAR, PPIl3, Caspase 8/10, NFkB and STAT6. Identification of a splicing-SNP rs10190751, which regulates CFLAR alternatively spliced isoforms predictive of the triptolide cytotoxicity suggests its role in triptolides action. Our results from functional studies in Panc-1 cell lines further demonstrate potential role of CFLAR in triptolide toxicity. Analysis of gene-expression with cytotoxicity identified JAK1 expression to be a significant predictor of triptolide sensitivity.

Conclusions

Overall out results identified genetic factors associated with triptolide chemo-sensitivity thereby opening up opportunities to better understand its mechanism of action as well as utilize these biomarkers to predict therapeutic response in patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1614-1) contains supplementary material, which is available to authorized users.

Up-regulated A20 promotes proliferation, regulates cell cycle progression and induces chemotherapy resistance of acute lymphoblastic leukemia cells

A20, also known as tumor necrosis factor-α (TNFα)-induced protein 3 (TNFAIP3), has been identified as a key regulator of cell survival in many solid tumors. However, little is known about the protein expression level and function of A20 in acute lymphoblastic leukemia (ALL). In this study, we found that A20 is up-regulated in ALL patients and several cell lines. Knockdown of A20 in Jurkat, Nalm-6, and Reh cells resulted in reduced cell proliferation, which was associated with cell cycle arrest. Phospho-ERK (p-ERK) was also down-regulated, while p53 and p21 were up-regulated in A20 knockdown cells. In addition, A20 knockdown induced apoptosis in Jurkat and Reh cells and enhanced the sensitivity of these cell lines to chemotherapeutic drugs. These results indicate that A20 may stimulate cell proliferation by regulating cell cycle progression. A20 inhibited apoptosis in some types of ALL cells, thereby enhancing their resistance to chemotherapy. This effect was abolished through A20 silencing. These findings suggest that A20 may contribute to the pathogenesis of ALL and that it may be used as a new therapeutic target for ALL treatment.

Computational prediction and experimental validation of low-affinity target of triptolide and its analogues

ERα as a novel low affinity target for triptolide and its analogues triptonide and triptriolide.

Enhanced anti-tumor efficacy of aspirin combined with triptolide in cervical cancer cells

BACKGROUND

The non-steroidal anti-inflammatory drug (NSAID) aspirin (acetylsalicylic acid) is an inhibitor of cyclooxygenase enzymes. Recent studies have shown that aspirin could be used as an anti-tumor drug. Triptolide, the major compound extracted from the Chinese herb Tripteryglum wilfordii Hook.f, has now been shown that it can inhibit tumor growth. The aim of this study was to analyze the anti-tumor efficiency of aspirin and triptolide in cervical cancer cells.

METHODS

Viability of cervical cancer cell lines was assessed by the MTT method at various concentrations of aspirin and triptolide. Siha and HeLa cell apoptotic analysis was performed by flow cytometry. Real time-PCR and Western Blotting were used to analyze the expression of Bcl-2/Bax, Cyclin D1 and p16.

RESULTS

Viability in the combination group was significantly decreased as compared with either drug used alone. Expression change of Bcl-2/Bax, CyclinD1 and p16 appeared to play an important role in the synergistic killing effect on cervical cancer cell apoptosis.

CONCLUSION

Aspirin and triptolide combination treatment may have synergistic anti-tumor effects on cervical cancer cells.

Triptolide induces apoptosis of gastric cancer cells via inhibiting the overexpression of MDM2

Triptolide has been reported to exhibit antitumor effects in several cancers. This study investigates the mechanism by which triptolide induces apoptosis of gastric cancer cells. Gastric biopsies were collected for histological evaluation and detection of murine double minute 2 (MDM2) expression. Gastric cancer cells were cultured and treated with different concentrations of triptolide at indicated time points. The expression of MDM2, p53 protein, and target proteins including p21, PUMA, and X-linked inhibitor of apoptosis protein (XIAP) was detected. Apoptosis of cells treated with or without triptolide was evaluated. Our results showed that MDM2 protein was overexpressed in gastric cancer (p < 0.01, resp.). Triptolide induced significant apoptosis of gastric cancer cells in a dose- and time-dependent manner (p < 0.05). In addition, treatment with triptolide strongly inhibited the overexpression of MDM2 in gastric cancer cells, and this MDM2 inhibition led to increased levels of p53 protein and inhibition of XIAP (p < 0.05). However, triptolide failed to increase the expression of p53 target protein p21 and PUMA (p > 0.05). In conclusion, triptolide may induce apoptosis of gastric cancer cells via the inhibition of MDM2 overexpression in a p53-independent manner.

Triptolide: progress on research in pharmacodynamics and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium wilfordii Hook. f. (Tripterygium wilfordii), also known as Huangteng and gelsemium elegan, is a traditional Chinese medicine that has been marketed in China as Tripterygium wilfordii glycoside tablets. Triptolide (TP), an active component in Tripterygium wilfordii extracts, has been used to treat various diseases, including lupus, cancer, rheumatoid arthritis and nephritic syndrome. This review summarizes recent developments in the research on the pharmacodynamics, pharmacokinetics, pharmacy and toxicology of TP, with a focus on its novel mechanism of reducing toxicity. This review provides insight for future studies on traditional Chinese medicine, a field that is both historically and currently important.

MATERIALS AND METHODS

We included studies published primarily within the last five years that were available in online academic databases (e.g., PubMed, Google Scholar, CNKI, SciFinder and Web of Science).

RESULTS

TP has a long history of use in China because it displays multiple pharmacological activities, including anti-rheumatism, anti-inflammatory, anti-tumor and neuroprotective properties. It has been widely used for the treatment of various diseases, such as rheumatoid arthritis, nephritic syndrome, lupus, Behcet׳s disease and central nervous system diseases. Recently, numerous breakthroughs have been made in our understanding of the pharmacological efficacy of TP. Although TP has been marketed as a traditional Chinese medicine, its multi-organ toxicity prevents it from being widely used in clinical practice.

CONCLUSIONS

Triptolide, a biologically active natural product extracted from the root of Tripterygium wilfordii, has shown promising pharmacological effects, particularly as an anti-tumor agent. Currently, in anti-cancer research, more effort should be devoted to investigating effective anti-tumor targets and confirming the anti-tumor spectrum and clinical indications of novel anti-tumor pro-drugs. To apply TP appropriately, with high efficacy and low toxicity, the safety and non-toxic dose range for specific target organs and diseases should be determined, the altered pathways and mechanisms of exposure need to be clarified, and an early warning system for toxicity needs to be established. With further in-depth study of the efficacy and toxicity of TP, we believe that TP will become a promising multi-use drug with improved clinical efficacy and safety in the future.

Inhibition of MDM2 by nilotinib contributes to cytotoxicity in both Philadelphia-positive and negative acute lymphoblastic leukemia

Nilotinib is a selective BCR-ABL tyrosine kinase inhibitor related to imatinib that is more potent than imatinib. Nilotinib is widely used to treat chronic myelogenous leukemia (CML) and Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). The present study identifies Mouse double minute 2 homolog (MDM2) as a target of nilotinib. In studying ALL cell lines, we found that the expression of MDM2 in both Philadelphia positive (Ph+) and Philadelphia negative (Ph-) ALL cells was remarkably inhibited by nilotinib, in a dose- and time-dependent manner. Further studies demonstrated that nilotinib inhibited MDM2 at the post-translational level by inducing MDM2 self-ubiquitination and degradation. Nilotinib-mediated MDM2 downregulation did not result in accumulation and activation of p53. Inhibition of MDM2 in nilotinib-treated ALL cells led to downregulation of the anti-apoptotic protein X-linked inhibitor of apoptosis protein (XIAP), a translational target of MDM2, resulting in activation of caspases. Inhibition of XIAP following nilotinib-mediated downregulation of MDM2 resulted in apoptosis of MDM2-expressing ALL; however, similar nilotinib treatment induced stronger apoptosis in Ph+/MDM2+ ALL than in Ph-/MDM2+ or Ph+/MDM2- ALL. The ALL cells that were Ph-/MDM2- were totally resistant to nilotinib. These results suggested that nilotinib can inhibit MDM2 and induce a p53-independent apoptosis pathway by downregulating XIAP; thus, nilotinib can treat not only Ph+, but also Ph- ALL patients whose cancer cells overexpress MDM2.

Synergism of cytotoxicity effects of triptolide and artesunate combination treatment in pancreatic cancer cell lines

BACKGROUND

Triptolide, extracted from the herb Tripteryglum wilfordii Hook.f that has long been used as a natural medicine in China, has attracted much interest for its anti-cancer effects against some kinds of tumours in recent years. Artesunate, extracted from the Chinese herb Artemisia annua, has proven to be effective and safe as an anti-malarial drug that possesses anticancer potential. The present study attempted to clarify if triptolide enhances artesunate-induced cytotoxicity in pancreatic cancer cell lines in vitro and in vivo.

METHODS

In vitro, to test synergic actions, cell viability and apoptosis were analyzed after treatment of pancreatic cancer cell lines with the two agents singly or in combination. The molecular mechanisms of apoptotic effects were also explored using qRT-PCR and Western blotting. In vivo, a tumor xenograft model was established in nude mice, for assessment of inhibitory effects of triptolide and artesunate.

RESULTS

We could show that the combination of triptolide and artesunate could inhibit pancreatic cancer cell line growth, and induce apoptosis, accompanied by expression of HSP 20 and HSP 27, indicating important roles in the synergic effects. Moreover, tumor growth was decreased with triptolide and artesunate synergy.

CONCLUSION

Our result indicated that triptolide and artesunate in combination at low concentrations can exert synergistic anti-tumor effects in pancreatic cancer cells with potential clinical applications.

BIIB021, an Hsp90 inhibitor, effectively kills a myelodysplastic syndrome cell line via the activation of caspases and inhibition of PI3K/Akt and NF-κB pathway proteins

The novel orally available inhibitor of the molecular chaperone heat shock protein 90 (Hsp90), BIIB021, induces the apoptosis of various types of tumor cell in vitro and in vivo. However, the effects and mechanisms of this agent on myelodysplastic syndrome (MDS) cell lines remain unknown. The aim of this study was to investigate the effects of BIIB021 on SKM-1 cells (a MDS cell line) and examine its mechanisms of action. The results showed that BIIB021 inhibited the growth of SKM-1 cells effectively in vitro. The treatment of SKM-1 cells with BIIB021 resulted in the inhibition of cell growth through G0/G1-phase cell cycle arrest and induced apoptosis by activating caspase-3, -8 and -9. Furthermore, this study also demonstrated that the mechanisms of apoptosis in SKM-1 cells were associated with the suppression of the phosphatidylinositide 3-kinase/Akt and nuclear factor-κB signaling pathways. Therefore, the findings indicate a novel approach for the treatment of high-risk MDS.

Triptolide induces apoptotic cell death of multiple myeloma cells via transcriptional repression of Mcl-1

Triptolide, a diterpenoid trioxide purified from the Chinese herb Tripterygium wilfordii Hook F, has been used as a natural medicine in China for hundreds of years. Several reports have demonstrated that triptolide inhibits the proliferation of cancer cells in vitro and reduces the growth of several types of tumors in vivo. To address the potential of triptolide as a novel therapeutic agent for patients with multiple myeloma, we investigated the effects of triptolide on the induction of apoptosis in human multiple myeloma cells in vitro. Triptolide rapidly induces apoptotic cell death in various myeloma cell lines. Triptolide-induced apoptosis in myeloma cells is associated with the loss of mitochondrial transmembrane potential (∆ψm), the release of cytochrome c and Smac/DIABLO from mitochondria into the cytosol, and the activation of caspase-3 and caspase-9. Furthermore, triptolide induces a rapid decline in the levels of Mcl-1 protein that correlates with caspase activation and induction of apoptosis. Inhibition of Mcl-1 synthesis by triptolide occurs at the level of mRNA transcription and is associated with an inhibition of phosphorylation of RNA polymerase II CTD. These results indicate that Mcl-1 is an important target for triptolide-induced apoptosis in myeloma cells that occurs via inhibition of Mcl-1 mRNA transcription coupled with rapid protein degradation through the ubiquitin-proteasome pathway.

Hsp90 inhibitor BIIB021 enhances triptolide-induced apoptosis of human T-cell acute lymphoblastic leukemia cells in vitro mainly by disrupting p53-MDM2 balance

AIM

To investigate the effects of BIIB021, an inhibitor of heat shock protein 90 (Hsp90) alone or in combination with triptolide (TPL) on T-cell acute lymphoblastic leukemia (T-ALL) and the mechanisms of action.

METHODS

Human T-ALL cells line Molt-4 was examined. The cell viability was measured using MTT assay. Apoptotic cells were studied with Hoechst 33258 staining. Cell apoptosis and cell cycle were analyzed using flow cytometry with Annexin V/PI staining and PI staining, respectively. The levels of multiple proteins, including Akt, p65, CDK4/6, p18, Bcl-2 family proteins, MDM2, and p53, were examined with Western blotting. The level of MDM2 mRNA was determined using RT-PCR.

RESULTS

Treatment of Molt-4 cells with BIIB021 (50-800 nmol/L) inhibited the cell growth in a dose-dependent manner (the IC50 value was 384.6 and 301.8 nmol/L, respectively, at 48 and 72 h). BIIB021 dose-dependently induced G0/G1 phase arrest, followed by apoptosis of Molt-4 cells. Furthermore, BIIB021 increased the expression of p18, decreased the expression of CDK4/6, and activated the caspase pathway in Molt-4 cells. Moreover, BIIB021 (50-400 nmol/L) dose-dependently decreased the phospho-MDM2 and total MDM2 protein levels, but slightly increased the phospho-p53 and total p53 protein levels, whereas TPL (5-40 nmol/L) dose-dependently enhanced p53 activation without affecting MDM2 levels. Co-treatment with BIIB021 and TPL showed synergic inhibition on Molt-4 cell growth. The co-treatment disrupted p53-MDM2 balance, thus markedly enhanced p53 activation. In addition, the co-treatment increased the expression of Bak and Bim, followed by increased activation of caspase-9.

CONCLUSION

The combination of BIIB021 and TPL may provide a novel strategy for treating T-ALL by overcoming multiple mechanisms of apoptosis resistance.

Triptolide induces growth inhibition and apoptosis of human laryngocarcinoma cells by enhancing p53 activities and suppressing E6-mediated p53 degradation

Triptolide, an active compound extracted from Chinese herb Leigongteng (Tripterygium wilfordii Hook F.), shows a broad-spectrum of anticancer activity through its cytotoxicity. However, the efficacy of triptolide on laryngocarcinoma rarely been evaluated, and the mechanism by which triptolide-induced cellular apoptosis is still not well understood. In this study, we found that triptolide significantly inhibited the laryngocarcinoma HEp-2 cells proliferation, migration and survivability. Triptolide induces HEp-2 cell cycle arrest at the G1 phase and apoptosis through intrinsic and extrinsic pathways since both caspase-8 and -9 are activated. Moreover, triptolide enhances p53 expression by increasing its stability via down-regulation of E6 and E6AP. Increased p53 transactivates down-stream target genes to initiate apoptosis. In addition, we found that short time treatment with triptolide induced DNA damage, which was consistent with the increase in p53. Furthermore, the cytotoxicity of triptolide is decreased by p53 knockdown or use of caspases inhibitor. In conclusion, our results demonstrated that triptolide inhibits cell proliferation and induces apoptosis in laryngocarcinoma cells by enhancing p53 expression and activating p53 functions through induction of DNA damage and suppression of E6 mediated p53 degradation. These studies indicate that triptolide is a potential anti-laryngocarcinoma drug.