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.

Nanoparticle-Based Combination Therapy for Ovarian Cancer

Ovarian cancer is one of the most common malignant tumors in gynecology with a high incidence. Combination therapy, eg, administration of paclitaxel followed by a platinum anticancer drug is recommended to treat ovarian cancer due to its advantages in, eg, reducing side effects and reversing (multi)drug-resistance compared to single treatment. However, the benefits of combination therapy are often compromised. In chemo and chemo/gene combinations, co-deposition of the combined therapeutics in the tumor cells is required, which is difficult to achieve due to dramatic pharmacokinetic differences between combinational agents in free forms. Moreover, some undesired properties such as the low-water solubility of chemodrugs and the difficulty of cellular internalization of gene therapeutics also hinder the therapeutic potential. Delivery of dual or multiple agents by nanoparticles provides opportunities to tackle these limits. Nanoparticles encapsulate hydrophobic drug(s) to yield aqueous dispersions facilitating its administration and/or to accommodate hydrophilic genes facilitating its access to cells. Moreover, nanoparticle-based therapeutics can not only improve drug properties (eg, in vivo stability) and ensure the same drug disposition behavior with controlled drug ratios but also can minimize drug exposure of the normal tissues and increase drug co-accumulation at targeted tissues via passive and/or active targeting strategies. Herein, this work summarizes nanoparticle-based combination therapies, mainly including anticancer drug-based combinations and chemo/gene combinations, and emphasizes the advantageous outcomes of nanocarriers in the combination treatment of ovarian cancer. In addition, we also review mechanisms of synergetic effects resulting from different combinations.

Potential of platinum-resensitization by Wnt signaling modulators as treatment approach for epithelial ovarian cancer

PURPOSE

Canonical Wnt/ β-catenin pathway is one mechanism being activated in platinum-resistant epithelial ovarian cancer (EOC). Detecting potential targets for Wnt pathway modulation as a putative future therapeutic approach was the aim of this study.

METHODS

Biological effects of different Wnt modulators (SB216763, XAV939 and triptolide) on the EOC cell lines A2780 and its platinum-resistant clone A2780cis were investigated via multiple functional tests. Immunohistochemistry (IHC) was carried out to compare the expression levels of Wnt marker proteins (β-catenin, snail/ slug, E-cadherin) in patient specimens and to correlate them with lifetime data.

RESULTS

We could show that activated Wnt signaling of the platinum-resistant EOC cell line A2780cis can be reversed by Wnt manipulators through SB216763 or XAV939. All Wnt manipulators tested consecutively decreased cell proliferation and cell viability. Apoptosis of A2780 and A2780cis was enhanced by triptolide in a dose-dependent manner, whereas cell migration was inhibited by SB216763 and triptolide. IHC analyses elucidated significantly different expression patterns for Wnt markers in the serous subtype. Herein, higher plasmatic snail/ slug expression is associated with improved progression-free (PFS) and overall survival (OS).

CONCLUSION

According to the described effects on EOC biology, all three Wnt manipulators seem to have the potential to augment the impact of a platinum-based chemotherapy in EOC. This is promising as a dominance of this pathway was confirmed in serous histology.

Discovery of potential targets of Triptolide through inverse docking in ovarian cancer cells

Triptolide (TPL) is proposed as an effective anticancer agent known for its anti-proliferation of a variety of cancer cells including ovarian cancer cells. Although some studies have been conducted, the mechanism by which TPL acts on ovarian cancer remains to be clearly described. Herein, systematic work based on bioinformatics was carried out to discover the potential targets of TPL in SKOV-3 cells. TPL induces the early apoptosis of SKOV-3 cells in a dose- and time-dependent manner with an IC₅₀ = 40 ± 0.89 nM when cells are incubated for 48 h. Moreover, 20 nM TPL significantly promotes early apoptosis at a rate of 40.73%. Using a self-designed inverse molecular docking protocol, we fish the top 19 probable targets of TPL from the target library, which was built on 2,250 proteins extracted from the Protein Data Bank. The 2D-DIGE assay reveals that the expression of eight genes is affected by TPL. The results of western blotting and qRT-PCR assay suggest that 40 nM of TPL up-regulates the level of Annexin A5 (6.34 ± 0.07 fold) and ATP syn thase (4.08 ± 0.08 fold) and down-regulates the level of β-Tubulin (0.11 ± 0.12 fold) and HSP90 (0.21 ± 0.09 fold). More details of TPL affecting on Annexin A5 signaling pathway will be discovered in the future. Our results define some potential targets of TPL, with the hope that this agent could be used as therapy for the preclinical treatment of ovarian cancer.

Triptolide inhibits Epstein-Barr nuclear antigen 1 expression by increasing sensitivity of mitochondria apoptosis of nasopharyngeal carcinoma cells

BACKGROUND

Epstein-Barr virus (EBV) is widely found in nasopharyngeal carcinoma (NPC) tissue and associated with poor prognosis of patients. EBV nuclear antigen 1 (EBNA1) is expressed in all NPC tumors and plays multiple biological roles in both virus and host cells. Triptolide is a natural product extracted from Tripterygium and shows anti-cancer activities. The goal of this work was to illustrate the anti-cancer effect of triptolide and elucidate a novel anti-apoptotic mechanism of EBNA1 in NPC cells encountered with triptolide.

METHODS

In the present study, a CCK-8 assay was used to analyze the proliferation of NPC cells treated with triptolide in a dose- and time-dependent ways. Effects of triptolide on NPC cell cycle and apoptosis were investigated by flow cytometric analysis. EBNA1 expression in mRNA and protein levels was determined by quantitative real-time PCR and Western blot, respectively.

RESULTS

Our results showed that triptolide effectively inhibited proliferation of NPC cells. Triptolide arrested NPC cell cycles in S phase and induced apoptosis through a caspase-9-dependent apoptosis pathway. Low-dose of triptolide reduced the half-life of EBNA1 and significantly decreased EBNA1 expression by promoting the process of proteasome-ubiquitin pathway. Over-expression of EBNA1, which was independent from EBV genome, effectively attenuated the apoptosis induced by triptolide. In addition, triptolide significantly inhibited proliferations of tumors induced by EBV-positive cells in vivo. Furthermore, EBNA1 were expressed in all NPC biopsies of Chinese patients.

CONCLUSIONS

In summary, our study provides the evidence that triptolide induces EBNA1 degradation and stimulates NPC apoptosis through mitochondria apoptotic pathway. In addition, EBNA1 assists NPC cells to resist triptolide-induced apoptosis through inhibiting caspase-9-dependent apoptotic pathway.

Triptolide Inhibits Proliferation and Migration of Human Neuroblastoma SH-SY5Y Cells by Upregulating MicroRNA-181a

Neuroblastoma is the primary cause of cancer-related death for children 1 to 5 years of age. New therapeutic strategies and medicines are urgently needed. This study aimed to investigate the effects of triptolide (TPL), the major active component purified from Tripterygium wilfordii Hook F, on neuroblastoma SH-SY5Y cell proliferation, migration, and apoptosis, as well as underlying potential mechanisms. We found that TPL inhibited SH-SY5Y cell viability, proliferation, and migration, but induced cell apoptosis. The expression of matrix metalloproteinase-2 (MMP-2) and MMP-9 after TPL treatment in SH-SY5Y cells was decreased. The expression of microRNA-181a (miR-181a) was upregulated after TPL treatment. Moreover, suppression of miR-181a reversed the effects of TPL on SH-SY5Y cell proliferation, apoptosis, and migration. Overexpression of miR-181a enhanced the TPL-induced activation of p38 mitogen-activated protein kinase (p38MAPK) and nuclear factor κ light chain enhancer of activated B cells (NF-κB) pathways. In conclusion, our research verified that TPL inhibited the proliferation and migration of human neuroblastoma SH-SY5Y cells by upregulating the expression of miR-181a.

Triptolide inhibits proliferation, differentiation and induces apoptosis of osteoblastic MC3T3‑E1 cells

Ankylosing spondylitis (AS) is characterized by the formation of bony spurs. Treatment of the resulting ankylosis, excessive bone formation and associated functional impairment, remain the primary therapeutic aims in research regarding this condition. Triptolide is the primary active component of the perennial vine Tripterygium wilfordii Hook. f., and has previously been demonstrated to exert anti-tumor activities including inhibition of cell growth and the induction of apoptosis, however, the effect of triptolide on osteoblasts remains to be elucidated. In the present study, the MC3T3-E1 mouse osteoblast cell line was treated with differing concentrations of triptolide for various intervals. Cell proliferation was detected using the bromodeoxyuridine assay, cell cycle and apoptosis were measured by flow cytometry, nuclear apoptosis was observed by Hoechst staining and associated proteins were determined via western blot analysis. The cells were then further incubated with osteogenic induction medium supplemented with triptolide for 7 or 12 days and the differentiation to osteoblasts was examined by picrosirius staining, observation of alkaline phosphatase activity and a calcium deposition assay. It was demonstrated that treatment with triptolide significantly inhibited osteoblast proliferation and induced cell cycle arrest and apoptosis of the osteoblasts. Furthermore, treatment with triptolide reduced collagen formation, alkaline phosphatase activity and calcium deposition. The present study demonstrated an inhibitory effect of triptolide on osteoblast proliferation and differentiation, and therefore suggests a potential therapeutic agent for the treatment of AS in the future.

Compounds From Celastraceae Targeting Cancer Pathways and Their Potential Application in Head and Neck Squamous Cell Carcinoma: A Review

Squamous cell carcinoma of the head and neck is one of the most common cancer types worldwide. It initiates on the epithelial lining of the upper aerodigestive tract, at most instances as a consequence of tobacco and alcohol consumption. Treatment options based on conventional therapies or targeted therapies under development have limited efficacy due to multiple genetic alterations typically found in this cancer type. Natural products derived from plants often possess biological activities that may be valuable in the development of new therapeutic agents for cancer treatment. Several genera from the family Celastraceae have been studied in this context. This review reports studies on chemical constituents isolated from species from the Celastraceae family targeting cancer mechanisms studied to date. These results are then correlated with molecular characteristics of head and neck squamous cell carcinoma in an attempt to identify constituents with potential application in the treatment of this complex disease at the molecular level.

Triptolide reverses the Taxol resistance of lung adenocarcinoma by inhibiting the NF-κB signaling pathway and the expression of NF-κB-regulated drug-resistant genes

Paclitaxel (or Taxol®) is a first-line chemotherapeutic drug for the treatment of non-small cell lung cancer; however, resistance to the drug is an important factor, which influences the outcome of chemotherapy. The present study aimed to investigate the role of triptolide (TPL) in reversing Taxol‑resistant human lung adenocarcinoma and to elucidate the underlying molecular mechanism of resistance reversal mediated by TPL. It was hypothesized that this experimental approach would assist in solving the problem of chemotherapeutic resistance in non‑small cell lung cancer, thereby improving the clinical outcomes. The human Taxol‑resistant lung adenocarcinoma cell line, A549/Taxol, was established. The resistance index of the cell line was calculated, according to the half maximal inhibitory concentration (IC50) of A549/Taxol IC50 of A549, to be 51.87. The levels of apoptosis and the cell cycle in the A549/Taxol cell line were assessed to confirm the effects of TPL at three different concentrations (0.03, 0.3 and 3 µmol/l) and treatment durations (2, 4, 6 and 12 h) by flow cytometric analysis, and the inhibition of the NF‑κB signaling pathway and the expression of NF‑κB‑regulated drug‑resistant proteins were determined by immunofluorescence and western blotting, respectively. The administration of TPL promoted cell apoptosis in the A549/Taxol lung adenocarcinoma Taxol‑resistant cell line and also promoted cell cycle regulation. The drug was also able to elicit a reversal of the drug resistance. TPL inhibited the nuclear factor‑κB (NF‑κB) signaling pathway and the expression of NF‑κB‑regulated drug‑resistant genes, including those for FLICE‑like inhibitory protein, X‑linked inhibitor of apoptosis protein, Bcl‑2, Bcl‑xL and cyclo‑oxygenase‑2. TPL exerted a marked drug‑resistance‑reversal effect on human lung adenocarcinoma Taxol resistance, and the effect was revealed to be dose‑ and time‑dependent. In conclusion, TPL exerted its role in the process of resistance reversal by inhibiting the NF‑κB signaling pathway, and the transcription and expression of NF-κB-regulated drug-resistant genes.

Targets and molecular mechanisms of triptolide in cancer therapy

Triptolide (TPL/TL) is a natural drug with novel anticancer effects. Preclinical studies indicated that TPL inhibits cell proliferation, induces cell apoptosis, inhibits tumor metastasis and enhances the effect of other therapeutic methods in various cancer cell lines. Multiple molecules and signaling pathways, such as caspases, heat-shock proteins, NF-κB, and deoxyribonucleic acid (DNA) repair-associated factors, are associated with the anti-cancer effect. TPL also improves chemoradiosensitivity in cancer therapy. Phase I trials indicate the potential clinical value of TPL use. However, further trials with larger sample sizes are needed to confirm these results.

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.

Inhibition of epithelial ovarian cancer by Minnelide, a water-soluble pro-drug

OBJECTIVE

Minnelide is a water-soluble pro-drug of triptolide, a natural product. The goal of this study was to evaluate the effectiveness of Minnelide on ovarian cancer growth in vitro and in vivo.

METHODS

The effect of Minnelide on ovarian cancer cell proliferation was determined by real time electrical impedance measurements. Multiple mouse models with C200 and A2780 epithelial ovarian cancer cell lines were used to assess the efficacy of Minnelide in inhibiting ovarian cancer growth.

RESULTS

Minnelide decreased cell viability of both platinum sensitive and resistant epithelial ovarian cancer cells in vitro. Minnelide with carboplatin showed additive effects in vitro. Minnelide monotherapy increased the survival of mice bearing established ovarian tumors. Minnelide, in combination with carboplatin and paclitaxel, improved overall survival of mice.

CONCLUSIONS

Minnelide is a promising pro-drug for the treatment of ovarian cancer, especially when combined with standard chemotherapy.

Multicomponent phytotherapeutic approach gaining momentum: Is the "one drug to fit all" model breaking down?

Natural product based drugs constitute a substantial proportion of the pharmaceutical market particularly in the therapeutic areas of infectious diseases and oncology. The primary focus of any drug development program so far has been to design selective ligands (drugs) that act on single selective disease targets to obtain highly efficacious and safe drugs with minimal side effects. Although this approach has been successful for many diseases, yet there is a significant decline in the number of new drug candidates being introduced into clinical practice over the past few decades. This serious innovation deficit that the pharmaceutical industries are facing is due primarily to the post-marketing failures of blockbuster drugs. Many analysts believe that the current capital-intensive model-"the one drug to fit all" approach will be unsustainable in future and that a new "less investment, more drugs" model is necessary for further scientific growth. It is now well established that many diseases are multi-factorial in nature and that cellular pathways operate more like webs than highways. There are often multiple ways or alternate routes that may be switched on in response to the inhibition of a specific target. This gives rise to the resistant cells or resistant organisms under the specific pressure of a targeted agent, resulting in drug resistance and clinical failure of the drug. Drugs designed to act against individual molecular targets cannot usually combat multifactorial diseases like cancer, or diseases that affect multiple tissues or cell types such as diabetes and immunoinflammatory diseases. Combination drugs that affect multiple targets simultaneously are better at controlling complex disease systems and are less prone to drug resistance. This multicomponent therapy forms the basis of phytotherapy or phytomedicine where the holistic therapeutic effect arises as a result of complex positive (synergistic) or negative (antagonistic) interactions between different components of a cocktail. In this approach, multicomponent therapy is considered to be advantageous for multifactorial diseases, instead of a "magic bullet" the metaphor of a "herbal shotgun" might better explain the state of affairs. The different interactions between various components might involve the protection of an active substance from decomposition by enzymes, modification of transport across membranes of cells or organelles, evasion of multidrug resistance mechanisms among others.

Minnelide: a novel therapeutic that promotes apoptosis in non-small cell lung carcinoma in vivo

BACKGROUND

Minnelide, a pro-drug of triptolide, has recently emerged as a potent anticancer agent. The precise mechanisms of its cytotoxic effects remain unclear.

METHODS

Cell viability was studied using CCK8 assay. Cell proliferation was measured real-time on cultured cells using Electric Cell Substrate Impedence Sensing (ECIS). Apoptosis was assayed by Caspase activity on cultured lung cancer cells and TUNEL staining on tissue sections. Expression of pro-survival and anti-apoptotic genes (HSP70, BIRC5, BIRC4, BIRC2, UACA, APAF-1) was estimated by qRTPCR. Effect of Minnelide on proliferative cells in the tissue was estimated by Ki-67 staining of animal tissue sections.

RESULTS

In this study, we investigated in vitro and in vivo antitumor effects of triptolide/Minnelide in non-small cell lung carcinoma (NSCLC). Triptolide/Minnelide exhibited anti-proliferative effects and induced apoptosis in NSCLC cell lines and NSCLC mouse models. Triptolide/Minnelide significantly down-regulated the expression of pro-survival and anti-apoptotic genes (HSP70, BIRC5, BIRC4, BIRC2, UACA) and up-regulated pro-apoptotic APAF-1 gene, in part, via attenuating the NF-κB signaling activity.

CONCLUSION

In conclusion, our results provide supporting mechanistic evidence for Minnelide as a potential in NSCLC.

Herbal compound triptolide synergistically enhanced antitumor activity of amino-terminal fragment of urokinase

Background

Urokinase (uPA) and its receptor (uPAR) play an important role in tumour growth and metastasis, and overexpression of these molecules is strongly correlated with poor prognosis in a variety of malignant tumours. Targeting the excessive activation of this system as well as the proliferation of the tumour vascular endothelial cell would be expected to prevent tumour neovasculature and halt tumour development. The amino terminal fragment (ATF) of urokinase has been confirmed effective to inhibit the proliferation, migration and invasiveness of cancer cells via interrupting the interaction of uPA and uPAR. Triptolide (TPL) is a purified diterpenoid isolated from the Chinese herb Tripterygium wilfordii Hook F that has shown antitumor activities in various cancer cell types. However, its therapeutic application is limited by its toxicity in normal tissues and complications caused in patients. In this study, we attempted to investigate the synergistic anticancer activity of TPL and ATF in various solid tumour cells.

Methods

Using in vitro and in vivo experiments, we investigated the combined effect of TPL and ATF at a low dosage on cell proliferation, cell apoptosis, cell cycle distribution, cell migration, signalling pathways, xenograft tumour growth and angiogenesis.

Results

Our data showed that the sensitivity of a combined therapy using TPL and ATF was higher than that of TPL or ATF alone. Suppression of NF-κB transcriptional activity, activation of caspase-9/caspase-3, cell cycle arrest, and inhibition of uPAR-mediated signalling pathway contributed to the synergistic effects of this combination therapy. Furthermore, using a mouse xenograft model, we demonstrated that the combined treatment completely suppressed tumour growth by inhibiting angiogenesis as compared with ATF or TPL treatment alone.

Conclusions

Our study suggests that lower concentration of ATF and TPL used in combination may produce a synergistic anticancer efficacy that warrants further investigation for its potential clinical applications.

Triptolide inhibits ovarian cancer cell invasion by repression of matrix metalloproteinase 7 and 19 and upregulation of E-cadherin

Triptolide, a compound extracted from the traditional Chinese medicine preparation of Tripterygium wilfordii Hook F., has been reported to have anti-inflammatory and anti-cancer activities. However, its effect on ovarian cancer invasion is unknown. We observed that MMP7 and MMP19 expression increased in ovarian cancer tissue. Triptolide treatment inhibited the migration and invasion of ovarian cancer cells SKOV3 and A2780 at the concentration of 15 nM. We also observed that triptolide suppressed MMP7 and MMP19 promoter activity in a dose-dependent manner, down-regulating the expressions of these promoters on mRNA and protein level. Moreover, triptolide enhanced E-cadherin expression in ovarian cancer cells. In vivo, triptolide inhibited tumor formation and metastasis in nude mice, and suppressed MMP7 and MMP19 expression; it also enhanced E-cadherin expression in tumor in a dose-dependent manner. Over expression of MMP7 and MMP19, or suppression of E-cadherin expression partially abolished the inhibitory effect of triptolide on invasion of ovarian cancer cells. To summarize, triptolide significantly inhibited the migration and invasion of ovarian cancer cells by suppression of MMP7 and MMP19 and up-regulation of E-cadherin expression. This study shows that triptolide is a good candidate for the treatment of ovarian cancer and reduction of metastasis.

Tectorigenin sensitizes paclitaxel-resistant human ovarian cancer cells through downregulation of the Akt and NFκB pathway

Paclitaxel (Taxol) is currently used as the front-line chemotherapeutic agent for several cancers including ovarian carcinoma; however, the drug frequently induces drug resistance through multiple mechanisms. The new strategy of using natural compounds in combination therapies is highly attractive because those compounds may enhance the efficacy of chemotherapy. In this study, we found that tectorigenin, an isoflavonoid isolated from flower of Pueraria thunbergiana, enhanced the growth-inhibitory effect of paclitaxel in paclitaxel-resistant ovarian cancer cells (MPSC1(TR), A2780(TR) and SKOV3(TR)) as well as their naive counterparts. The combination of tectorigenin with paclitaxel resulted in a synergistic apoptosis compared with either agent alone through activation of caspases-3, -8 and -9. Treatment with tectorigenin inhibited the nuclear translocation of NFκB and the expression of NFκB-dependent genes such as FLIP, XIAP, Bcl-2, Bcl-xL and COX-2, which are known to be associated with chemoresistance. In addition, the tectorigenin-paclitaxel combination inhibited the phosphorylation of IκB and IKK and the activation of Akt in paclitaxel-resistant cancer cells. Moreover, tectorigenin-paclitaxel-induced cell growth inhibition was enhanced by pretreatment with the Akt inhibitor LY294002 or overexpression of the dominant negative Akt (Akt-DN), but reduced by overexpression of constitutively activated Akt (Akt-Myr). Furthermore, we found that Akt-Myr, at least in part, reversed tectorigenin-paclitaxel-induced nuclear translocation of NFκB and the phosphorylation of IκB and IKK. These data suggest that tectorigenin could sensitize paclitaxel-resistant human ovarian cancer cells through inactivation of the Akt/IKK/IκB/NFκB signaling pathway, and promise a new intervention to chemosensitize paclitaxel-induced cytotoxicity in ovarian cancer.

Triptolide: structural modifications, structure-activity relationships, bioactivities, clinical development and mechanisms

Triptolide, a principal bioactive ingredient of Tripterygium wilfordii Hook F, has attracted extensive exploration due to its unique structure of a diterpenoid triepoxide and multiple biological activities. This review will focus on the structural modifications, structure-activity relationships, pharmacology, and clinical development of triptolide in the last forty years.

Triptolide and its expanding multiple pharmacological functions

Triptolide, a diterpene triepoxide, is a major active component of extracts derived from the medicinal plant Tripterygium wilfordii Hook F (TWHF). Triptolide has multiple pharmacological activities including anti-inflammatory, immune modulation, antiproliferative and proapoptotic activity. So, triptolide has been widely used to treat inflammatory diseases, autoimmune diseases, organ transplantation and even tumors. Triptolide cannot only induce tumor cell apoptosis directly, but can also enhance apoptosis induced by cytotoxic agents such as TNF-α, TRAIL and chemotherapeutic agents regardless of p53 phenotype by inhibiting NFκB activation. Recently, the cellular targets of triptolide, such as MKP-1, HSP, 5-Lox, RNA polymerase and histone methyl-transferases had been demonstrated. However, the clinical use of triptolide is often limited by its severe toxicity and water-insolubility. New water-soluble triptolide derivatives have been designed and synthesized, such as PG490-88 or F60008, which have been shown to be safe and potent antitumor agent. Importantly, PG490-88 has been approved entry into Phase I clinical trial for treatment of prostate cancer in USA. This review will focus on these breakthrough findings of triptolide and its implications.

Molecular analyses of the Chinese herb Leigongteng (Tripterygium wilfordii Hook.f.)

Tripterygium wilfordii Hook.f., known as Leigongteng (Thunder God Vine) in traditional Chinese medicine, has attracted much attention for its applications in relieving autoimmune disorders such as rheumatoid arthritis and systemic lupus erythematosus, and for treating cancer. Molecular analyses of the ITS and 5S rDNA sequences indicate that T. hypoglaucum and T. doianum are not distinct from T. wilfordii, while T. regelii should be recognized as a separate species. The results also demonstrate potential value of rDNA sequence data in forensic detection of adulterants derived from Celastrus angulatus in commercial samples of Leigongteng.

Proteomic analysis of cisplatin resistance in human ovarian cancer using 2-DE method

Platinum-based chemotherapy, such as cisplatin, is the primary treatment for human ovarian cancer. However, overcoming drug resistance has become an important issue in cancer chemotherapy. In this study, we performed 2-DE and ESI-Q-TOF MS/MS analysis to identify differential proteins expression between cisplatin-sensitive (A2780S) and cisplatin-resistant (A2780-CP) ovarian cancer cell lines. Of the 14 spots identified as differentially expressed (±over twofold, P < 0.05) between the two cell lines, ten spots (corresponding to ten unique proteins) were positively identified by ESI-Q-TOF MS/MS analysis. These proteins include capsid glycoprotein, fructose-bisphosphate aldolase C, heterogeneous nuclear ribonucleoproteins A2/B1, putative RNA-binding protein 3, Ran-specific GTPase-activating protein, ubiquitin carboxyl-terminal hydrolase isozyme L1, stathmin, ATPSH protein, chromobox protein homolog3 and phosphoglycerate kinase 1. The proteins identified in this study would be useful in revealing the mechanisms underlying cisplatin resistance and also provide some clues for further research.

Biologic activity of triptolide in t(8;21) acute myeloid leukemia cells

Triptolide is a compound isolated from the traditional Chinese medicinal herb Tripterygium wilfordii that shows potent anti-tumor activities, but its effects on acute myeloid leukemia with t(8;21) remain unclear. Here we report that triptolide inhibits cell proliferation and induces apoptosis in a dose- and time-dependent manner of t(8;21)-bearing Kasumi-1, SKNO-1 and CD34+ cells harvested from bone marrow samples of patients with t(8;21) leukemia. We show that triptolide triggers cleavage of the resultant AML1-ETO fusion protein of t(8;21), and causes downregulation of C-KIT followed by inhibition of JAK-STAT signaling. Triptolide downregulates p65 and inhibits the DNA-binding activity of NF-κB. Our data indicate that triptolide might be an effective agent for t(8;21) leukemia.

Novel target genes responsive to the anti-growth activity of triptolide in endometrial and ovarian cancer cells

Triptolide (TPL), a bioactive component of the Chinese medicinal herb Tripterygium wilfordii Hook F, induces apoptosis in some lines of human tumor cells. However, the effect of TPL on gynecologic cancer cells has not yet been well-described. We investigated the effects of TPL on cell growth, cell cycle, and apoptosis in endometrial and ovarian cancer cell lines. Furthermore, we examined global changes in gene expression after treatment with TPL. By using a list of 20 differentially expressed genes, Western blot analyses were performed on five endometrial and ovarian cancer cell lines. All cell lines were sensitive to the growth-inhibitory effect of TPL. TPL increased the proportion of cells in the S-phase of the cell cycle and induced apoptosis. cDNA microarray assay demonstrated that the treatment with TPL changed the expression of cell cycle regulators, apoptosis-related factors and cell proliferation markers. Of the gene expression changes induced by TPL treatment, up-regulation of LRAP, CDH4, and SFRP1 and down-regulation of cystatin, TNNT 1, and L1-CAM were confirmed using Western blot analysis in all the cell lines examined. We found a strong anticancer activity of TPL and identified some potential target genes of this drug, raising hopes that TPL may become a useful therapy for endometrial and ovarian cancers.

Triptolide downregulates Rac1 and the JAK/STAT3 pathway and inhibits colitis-related colon cancer progression

Triptolide, a diterpenoid triepoxide from the traditional Chinese medicinal herb Tripterygium wilfordii Hook. f., is a potential treatment for autoimmune diseases as well a possible anti-tumor agent. It inhibits proliferation of colorectal cancer cells in vitro and in vivo. In this study, its ability to block progress of colitis to colon cancer, and its molecular mechanism of action are investigated. A mouse model for colitis-induced colorectal cancer was used to test the effect of triptolide on cancer progression. Treatment of mice with triptolide decreased the incidence of colon cancer formation, and increased survival rate. Moreover, triptolide decreased the incidence of tumors in nude mice inoculated with cultured colon cancer cells dose-dependently. In vitro, triptolide inhibited the proliferation, migration and colony formation of colon cancer cells. Secretion of IL6 and levels of JAK1, IL6R and phosphorylated STAT3 were all reduced by triptolide treatment. Triptolide prohibited Rac1 activity and blocked cyclin D1 and CDK4 expression, leading to G1 arrest. Triptolide interrupted the IL6R-JAK/STAT pathway that is crucial for cell proliferation, survival, and inflammation. This suggests that triptolide might be a candidate for prevention of colitis induced colon cancer because it reduces inflammation and prevents tumor formation and development.

Triptolide therapy for neuroblastoma decreases cell viability in vitro and inhibits tumor growth in vivo

BACKGROUND

Heat shock protein (Hsp)-70 is overexpressed in several human malignancies, and its inhibition has been shown to kill cancer cells. Our objectives were to assess the effectiveness of triptolide, an Hsp-70 inhibitor, in treating neuroblastoma in vitro and in vivo, and to measure the associated effects on Hsp-70 levels and apoptosis markers.

METHODS

After exposing N2a and SKNSH cell lines to triptolide, cell viability was assessed. Caspase-3 and -9 activities were measured and annexin staining performed to determine if cell death occurred via apoptosis. Hsp-70 protein and mRNA levels were determined using Western blot and real-time polymerase chain reaction. In an orthotopic tumor model, mice received daily triptolide injections and were humanely killed at study completion with tumor measurement.

RESULTS

Triptolide treatment resulted in dose- and time-dependent N2a cell death and dose-dependent SKNSH killing. Triptolide exposure was associated with dose-dependent increases in caspase activity and annexin staining. Triptolide decreased Hsp-70 protein and mRNA levels in a dose-dependent fashion. Mice receiving triptolide therapy had significantly smaller tumors than controls.

CONCLUSION

Triptolide therapy decreased neuroblastoma cell viability in vitro and inhibited tumor growth in vivo. Our studies suggest that triptolide killed cells via apoptosis and in association with inhibition of Hsp-70 expression. Triptolide may provide a novel therapy for neuroblastoma.