Tetrandrine and fangchinoline, bisbenzylisoquinoline alkaloids from Stephania tetrandra can reverse multidrug resistance by inhibiting P-glycoprotein activity in multidrug resistant human cancer cells

Lycorine possesses notable anticancer potentials in on-small cell lung carcinoma cells via blocking Wnt/β-catenin signaling and epithelial-mesenchymal transition (EMT)

Lycorine, an natural isoquinoline alkaloid has reportedly that possesses multi-anticancer activity. However, to date, the anticancer feature of lycorine in non-small cell lung carcinoma (NSCLC) has still not fully been spelled out. The present study mainly focused on the molecular mechanism of lycorine against NSCLC in vitro and vivo. The results showed that lycorine evidently inhibited proliferation of A549 and H460 with IC₅₀ values were 10.83 ± 1.14 μM and 12.35 ± 1.13 μM, while caused slight cytotoxicity in normal pulmonary epithelial Beas-2B cells, and arrested cell cycle in G0/G1 phase. Hoechst DNA-binding staining showed that typical characteristics of nuclear morphology apoptosis, AnnexinV-FITC/PI staining revealed the early-period apoptosis and the dissipation of mitochondrial membrane potential (Δψm) were also captured after lycorine treatment. Moreover, lycorine effectively repressed the Wnt/β-catenin signaling and reversed epithelial-mesenchymal transition (EMT). In addition, lycorine also intervened the caspase-mediated mitochondrial apoptosis pathway. Furthermore, A549/Luc tumor xenograft model was also corroborated that lycorine significantly suppressed the growth and metastasis of the lung tumor. These data highlight the significance of lycorine as potential anti-neoplastic agents to combat NSCLC.

Design and synthesis of novel C14-urea-tetrandrine derivatives with potent anti-cancer activity

Tetrandrine is a dibenzyltetrahydroisoquinoline alkaloid, isolated from traditional Chinese medicinal plant Stephania tetrandra, with anti-tumor activity. Our previous study identified several derivatives of tetrandrine showing better activities than parental compound against human hepatocellular carcinoma cells. To increase diversity and cytotoxic activities of the original compound, a series of novel 14-urea-tetrandrine derivatives were synthesized through structural modification of tetrandrine. These derivaties demonstrated a moderate to strong anti-proliferative activities against human cell lines HEL and K562 (Leukemia), prostate (PC3), breast (MDA-MB-231) and melanoma (WM9). Compound 4g showed strongest cytotoxic effect against PC3 cells with IC₅₀ value of 0.64 μM, which was 12-fold, 31-fold and 26-fold lower than the parental tetrandrine, 5-fluorouracil and cisplatin, respectively. Preliminary structure-activity relationship study indicated that urea subsititution was the key pharmacophore for the enhancement of their antitumor activities. Induction of apoprosis by 4g was associated with the activation of pro-apoptotic protein BAX and inhibition of antiapoptosis proteins survivin as well as Bcl-2. Moreover, activation of caspases led to increase cleavage of PARP, which further accelerates apoptotic cell death. These results reveal that the compound 4g may be used as a potential anticancer drug candidate.

Tetrandrine and cancer - An overview on the molecular approach

Tetrandrine has been known in the treatment of tuberculosis, hyperglycemia, negative ionotropic and chronotropic effects on myocardium, malaria, cancer and fever since years together. It has been known that, tetrandrine could modulate multiple signaling molecules such as kinases of cell cycle and rat sarcoma (RAS) pathway along with proteins of tumor suppressor genes, autophagy related, β-catenins, caspases, and death receptors. Moreover, tetrandrine exhibited reversal of drug resistance by modulating P-glyco protein (P-gp) expression levels in different cancers which is an added advantage of this compound compared to other chemotherapy drugs. Though, bioavailability of tetrandrine is a limiting factor, the anticancer activity was observed in animal models without changing any pharmacokinetic parameters. In the present review, role of tetrandrine as kinase inhibitor, inducer of autophagy and caspase pathways and suppressor of RAS mediated cell proliferation were discussed along with inhibition of angiogenesis. It has also been discussed that how tetrandrine potentiate anticancer effect in different types of cancers by modulating multidrug resistance under in vitro and in vivo trials including the available literature on the clinical trials.

Isaria cicadae conidia possess antiproliferative and inducing apoptosis properties in gynaecological carcinoma cells

Isaria cicadae is an entomogenous fungus that has been used as a traditional Chinese medicinal materials to treat different diseases, including cancer. However, Isaria cicadae conidia for inhibitory activity against breast cancer cells growth are still not systematically studied. The present aim was to elucidate the phytochemical composition of Isaria cicadae conidia and to explore relevant anti-cancer potential in gynaecological carcinoma MCF-7 and Hela cells. Isaria cicadae conidia were identified by UPLC-ESI-Q-TOF-MS: high performance liquid chromatography-electrospray/quadrupole time of flight tandem mass spectrometry technology. Eight main compounds were identified which are nucleosides, cordycepic acid, cordycepin, beauvericin and myriocin by MS fragmentation ions. The nuclear morphology indicated the typical characteristics of apoptosis by Hoechst staining. Annexin V/PI staining revealed that the number of apoptotic cells was increased by Isaria cicadae conidia treatment. Furthermore, Isaria cicadae conidia also induced the caspase-mediated mitochondrial apoptosis pathway. The findings suggest that the full-scale active ingredients highlight the significance of Isaria cicadae conidia as potential anti-cancer agent in China.

Fangchinoline inhibits migration and causes apoptosis of human breast cancer MDA-MB-231 cells

In order to improve outcomes after breast cancer treatment, it is essential to understand the mechanisms of action of potential therapeutic agents. The effect of fangchinoline (FAN) on migration and apoptosis of human breast cancer MDA-MB-231 cells and its underlying mechanisms were investigated. MDA-MB-231 cells were treated with different concentrations of FAN, growth inhibition rates were measured by MTT assay and morphological changes of apoptotic cells were observed by Hoechst staining. The wound-healing assay was used to determine of the effect of FAN on the migration of MDA-MB-231 cells. ELISA was used to detect the expression of MMP-2 and −9 in MDA-MB-231 cells treated with different concentrations of FAN and western blot analysis was used to quantify expression of NF-κβ and Iκβ proteins in the same cells. Our results showed that FAN significantly inhibited the growth of MDA-MB-231 cells in concentration-dependent manner and it induced MDA-MB-231 cell apoptosis. With the high FAN concentrations and long exposure times, the levels of MMP-2 and −9 decreased and the expression of NF-κβ decreased, while the expression of Iκβ protein increased. Based on these results, the antitumor effects of FAN on breast cancer cells can be explained at least partially by inducing apoptosis and inhibiting the migration of MDA-MB-231 cells.

Fangchinoline suppresses growth and metastasis of melanoma cells by inhibiting the phosphorylation of FAK

Melanoma is a malignant tumor with high degree of malignancy, metastasis and high mortality. The etiology of melanoma has not been fully elucidated, and there is no effective drug for the complete treatment of melanoma. In recent years, many traditional Chinese herbal medicines have played an important role in clinical treatment and experimental research on cancer. As a natural product, fangchinoline has the characteristics of enhancing immune function, low toxicity and good liver protection features, so it is considered to be a new type of anticancer drug. In the present study, we found that fangchinoline has inhibitory effects on the proliferation and metastasis of A375 and A875 cells in a concentration-dependent manner. Fangchinoline inhibited the proliferation of A375 and A875 cell activity with IC50 values of 12.41 and 16.20 µM. We also found that fangchinoline could significantly reduce the phosphorylation of Focal adhesion kinase (FAK). In summary, we demonstrated that fangchinoline inhibits the proliferation and metastasis of melanoma cells by suppressing FAK and its downstream signaling pathway. More importantly, we provide a novel mechanism that fangchinoline could be an effective candidate for the treatment of melanoma.

Natural Products as Alternative Choices for P-Glycoprotein (P-gp) Inhibition

Multidrug resistance (MDR) is regarded as one of the bottlenecks of successful clinical treatment for numerous chemotherapeutic agents. Multiple key regulators are alleged to be responsible for MDR and making the treatment regimens ineffective. In this review, we discuss MDR in relation to P-glycoprotein (P-gp) and its down-regulation by natural bioactive molecules. P-gp, a unique ATP-dependent membrane transport protein, is one of those key regulators which are present in the lining of the colon, endothelial cells of the blood brain barrier (BBB), bile duct, adrenal gland, kidney tubules, small intestine, pancreatic ducts and in many other tissues like heart, lungs, spleen, skeletal muscles, etc. Due to its diverse tissue distribution, P-gp is a novel protective barrier to stop the intake of xenobiotics into the human body. Over-expression of P-gp leads to decreased intracellular accretion of many chemotherapeutic agents thus assisting in the development of MDR. Eventually, the effectiveness of these drugs is decreased. P-gp inhibitors act by altering intracellular ATP levels which are the source of energy and/or by affecting membrane contours to increase permeability. However, the use of synthetic inhibitors is known to cause serious toxicities. For this reason, the search for more potent and less toxic P-gp inhibitors of natural origin is underway. The present review aims to recapitulate the research findings on bioactive constituents of natural origin with P-gp inhibition characteristics. Natural bioactive constituents with P-gp modulating effects offer great potential for semi-synthetic modification to produce new scaffolds which could serve as valuable investigative tools to recognize the function of complex ABC transporters apart from evading the systemic toxicities shown by synthetic counterparts. Despite the many published scientific findings encompassing P-gp inhibitors, however, this article stand alones because it provides a vivid picture to the readers pertaining to Pgp inhibitors obtained from natural sources coupled with their mode of action and structures. It provides first-hand information to the scientists working in the field of drug discovery to further synthesise and discover new P-gp inhibitors with less toxicity and more efficacies.

Mechanism Underlying the Reversal of Drug Resistance in P-Glycoprotein-Expressing Leukemia Cells by Pinoresinol and the Study of a Derivative

P-glycoprotein (P-gp) is a membrane protein associated with multidrug resistance (MDR) due to its key role in mediating the traffic of chemotherapeutic drugs outside cancer cells, leading to a cellular response that hinders efforts toward successful therapy. With the aim of finding agents that circumvent the MDR phenotype mediated by P-gp, 15 compounds isolated from native and naturalized plants of Argentina were screened. Among these, the non-cytotoxic lignan (±) pinoresinol successfully restored sensitivity to doxorubicin from 7 μM in the P-gp overexpressed human myelogenous leukemia cells, Lucena 1. This resistance-reversing effect was confirmed by competitively increasing the intracellular doxorubicin accumulation and by significantly inhibiting the efflux of doxorubicin and, to a lesser extent, that of rhodamine 123. The activity obtained was similar to that observed with verapamil. No such results were observed in the sensitive parental K562 cell line. To gain deeper insight into the mode of action of pinoresinol, its effect on P-gp function and expression was examined. The docking simulations indicated that the lignan bound to P-gp at the apex of the V-shaped transmembrane cavity, involving transmembrane helices 4, 5, and 6, and partially overlapped the binding region of tariquidar, which was used as a positive control. These results would shed some light on the nature of its interaction with P-gp at molecular level and merit further mechanistic and kinetic studies. In addition, it showed a maximum 29% activation of ATP hydrolysis and antagonized verapamil-stimulated ATPase activity with an IC₅₀ of 20.9 μM. On the other hand, pinoresinol decreased the presence of P-gp in the cell surface. Derivatives of pinoresinol with improved activity were identified by docking studies. The most promising one, the non-cytotoxic 1-acetoxypinoresinol, caused a reversion of doxorubicin resistance from 0.11 μM and thus higher activity than the lead compound. It also caused a significant increase in doxorubicin accumulation. Results were similar to those observed with verapamil. The results obtained positioned these compounds as potential candidates for effective agents to overcome P-gp-mediated MDR, leading to better outcomes for leukemia chemotherapy.

Effect of traditional Chinese medicine components on multidrug resistance in tumors mediated by P-glycoprotein

Multidrug resistance (MDR) is a major cause of chemotherapy failure. It occurs when an organism is resistant to one type of drug, but also develops resistance to other drugs with different structures and targets. There is a high incidence of MDR in cancer chemotherapy, therefore, finding an effective and non-toxic MDR reversal agent is an important goal, particularly for P-glycoprotein-mediated MDR in cancer. Improvements continue to be made to the status and understanding of traditional Chinese medicine (TCM), due to the advantages of low toxicity and relatively minor side effects. Therefore TCM is currently being used in the treatment of various types of diseases. In recent years, numerous components of TCM have been identified to be effective in reversing MDR by downregulating expression of the drug transporter membrane protein, recovering changes in enzymes involved in detoxification and metabolism and repairing the cell apoptosis pathway. The present study summarizes the anticancerous properties and MDR reversing components of traditional medicinal plants commonly used in the treatment of cancer.

Stephania Tetrandra and Ginseng-Containing Chinese Herbal Formulation NSENL Reverses Cisplatin Resistance in Lung Cancer Xenografts

Chinese Herbal Formulation, supplement energy and nourish lung (SENL), effectively enhances chemotherapeutic efficacy in lung cancer treatment and reverses multi-drug resistance (MDR) in lung cancer cells in vitro. The present study is designed to assess the effect of a New SENL (NSENL, modification of SENL) formulation on resistance to chemotherapy of cisplatin (DDP)-resistant human lung cancer cell line (A549/DDP) xenografts in nude mice. We assessed six constituents in NSENL by high performance liquid chromatography (HPLC). BALB/c nude mice harboring A549/DDP cell xenografts were established to assess the antitumor effect of NSENL and its impact on the expression of MDR related genes. The six constituents in NSENL, including ginsenoside Rg1, ginsenoside Rb1, ginsenoside Rg3, astragaloside IV, ophiopogonin D and tetrandrine were quantitated simultaneously by HPLC. The combination of NSENL with DDP significantly inhibited tumor growth at a rate of up to 66.8% ([Formula: see text]). In addition, NSENL as monotherapy or combined with DDP downregulated multidrug resistance-associated protein 1 (MRP1), basic fibroblast growth factor (bFGF) and fibroblast growth factor receptor 1 (FGFR1) at both the mRNA and protein levels ([Formula: see text]), reduced glutathione S-transferase π (GST-π) protein expression and tumor microvascular density as well as decreased phosphorylation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR) ([Formula: see text]). These findings demonstrated that NSENL can reverse MDR in A549/DDP cells in vivo, an effect possibly associated with downregulation of MDR-associated genes as well as inhibition of bFGF/FGFR and phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR signaling pathways.

A 20(S)-protopanoxadiol derivative overcomes multi-drug resistance by antagonizing ATP-binding cassette subfamily B member 1 transporter function

In cancer cells, failure of chemotherapy is often caused by the ATP-binding cassette subfamily B member 1 (ABCB1), and few drugs have been successfully developed to overcome ABCB1-mediated multi-drug resistance (MDR). To suppress ABCB1 activity, we previously designed and synthesized a new series of derivatives based on 20(S)-protopanoxadiol (PPD). In the present study, we investigated the role of PPD derivatives in the function of ABC transporters. Non-toxic concentrations of the PPD derivative PPD12 sensitized ABCB1-overexpressing cells to their anti-cancer substrates better than either the parental PPD or inactive PPD11. PPD12 increased intracellular accumulation of adriamycin and rhodamine123 in resistant cancer cells. Although PPD12 did not suppress the expression of ABCB1 mRNA or protein, it stimulated the activity of ABCB1 ATPase. Because PPD12 is a competitive inhibitor, it was predicted to bind to the large hydrophobic cavity of homology-modeled human ABCB1. PPD12 also enhanced the efficacy of adriamycin against ABCB1-overexpressing KB/VCR xenografts in nude mice. In conclusion, PPD12 enhances the efficacy of substrate drugs in ABCB1-overexpressing cancer cells. These findings suggest that a combination therapy consisting of PPD12 with conventional chemotherapeutic agents may be an effective treatment for ABCB1-mediated MDR cancer patients.

Isochondodendrine and 2′-norcocsuline: additional alkaloids from Triclisia subcordata induce cytotoxicity and apoptosis in ovarian cancer cell lines

Triclisia subcordata Oliv (Menispermeaceae) is used in herbal medicine for the treatment of cancer and other diseases in Africa.

Geniposide reverses multidrug resistance in vitro and in vivo by inhibiting the efflux function and expression of P-glycoprotein

Geniposide is a water-soluble iridoid glucoside with anti-oxidant and anti-inflammatory biological functions. It has been indicated that geniposide may increase doxorubicin (DOX) accumulation in drug-resistant tumor cells. The present study aimed to investigate the resistance-reversing effect of geniposide in DOX-resistant cells and assess the underlying mechanisms of its action. The results revealed that geniposide itself weakly inhibited tumor cell growth. Furthermore, geniposide effectively reversed DOX resistance in a dose-dependent manner in human osteosarcoma DOX-resistant (MG63/DOX) cells. The action of geniposide was confirmed by increased accumulation of intracellular DOX detected in MG63/DOX cells. Notably, geniposide enhanced the efficacy of DOX against MG63/DOX cancer cell-derived xenografts in nude mice. To study the mechanism, intracellular accumulation of rhodamine 123 was measured using flow cytometry. At concentrations that reversed multidrug resistance (MDR), geniposide significantly downregulated P-glycoprotein (P-gp) expression. Therefore, geniposide reverses P-gp-mediated MDR by reducing the expression of P-gp and its transport function. The present study therefore indicated that geniposide may be administered in combination with conventional anti-neoplastic drugs to prevent MDR.

Design and synthesis of new tetrandrine derivatives and their antitumor activities

A series of tetrandrine derivatives were designed and synthesized using Suzuki coupling reaction. Eleven targeted compounds with over 50% inhibition against HL60 and A549 human cancer cell lines at 10 μM were further evaluated for the in vitro antitumor activities by MTT or SRB assay. The biological results revealed that some compounds exhibited potent antitumor activities. Thiophene derivative 6 and acetylphenyl derivative 5 were the most active ones against HL60 and A549 cell lines, with IC50 values less than 5 μM, which thus could be considered as useful candidate for further development of new antitumor agents.

Cytotoxicity Effects and Apoptosis Induction by Bisbenzylisoquinoline Alkaloids from Triclisia subcordata

Triclisia subcordata Oliv (Menispermeaceae) is a medicinal plant traditionally used for the treatment of various diseases in West Africa. The ethanol extract of T. subcordata and its fractions were screened for in vitro anti-ovarian cancer activities using the Sulforhodamine B assay. The crude alkaloids showed the strongest activity in cell growth assays on Ovcar-8 and A2780 cell lines (IC50  < 2.4 µg/mL). A bisbenzylisoquinoline alkaloid-cycleanine was isolated using HPLC and identified by mass spectrometry and nuclear magnetic resonance analyses. The IC50 values of cycleanine and tetrandrine (an alkaloid previously reported from this plant) ranged from 7 to 14 μM on Ovcar-8, A2780, Ovcar-4, and Igrov-1 ovarian cancer cell lines. The IC50 of cycleanine on human normal ovarian surface epithelial cells was 35 ± 1 μM, hinting at modest selectivity toward cancer cells. Both cycleanine and tetrandrine caused apoptosis as shown by activation of caspases 3/7 and cleavage of poly(ADP-ribose) polymerase to form poly(ADP-ribose) polymerase-1 by using western blot analysis. Flow cytometry analyses showed that the percentages of apoptotic cells and cells in subG1 phase increased after exposure of cycleanine and tetrandrine to Ovcar-8 cells for 48 h compared with control. Cycleanine, like its isomer tetrandrine isolated from T. subcordata, could be a potential new anti-ovarian cancer agent acting through the apoptosis pathway. Copyright © 2016 John Wiley & Sons, Ltd.

Hernandezine, a Bisbenzylisoquinoline Alkaloid with Selective Inhibitory Activity against Multidrug-Resistance-Linked ATP-Binding Cassette Drug Transporter ABCB1

The overexpression of ATP-binding cassette (ABC) drug transporter ABCB1 (P-glycoprotein, MDR1) is the most studied mechanism of multidrug resistance (MDR), which remains a major obstacle in clinical cancer chemotherapy. Consequently, resensitizing MDR cancer cells by inhibiting the efflux function of ABCB1 has been considered as a potential strategy to overcome ABCB1-mediated MDR in cancer patients. However, the task of developing a suitable modulator of ABCB1 has been hindered mostly by the lack of selectivity and high intrinsic toxicity of candidate compounds. Considering the wide range of diversity and relatively nontoxic nature of natural products, developing a potential modulator of ABCB1 from natural sources is particularly valuable. Through screening of a large collection of purified bioactive natural products, hernandezine was identified as a potent and selective reversing agent for ABCB1-mediated MDR in cancer cells. Experimental data demonstrated that the bisbenzylisoquinoline alkaloid hernandezine is selective for ABCB1, effectively inhibits the transport function of ABCB1, and enhances drug-induced apoptosis in cancer cells. More importantly, hernandezine significantly resensitizes ABCB1-overexpressing cancer cells to multiple chemotherapeutic drugs at nontoxic, nanomolar concentrations. Collectively, these findings reveal that hernandezine has great potential to be further developed into a novel reversal agent for combination therapy in MDR cancer patients.

Tetrandrine--A molecule of wide bioactivity

Stephania tetrandra and other related species of Menispermaceae form the major source of the bisbenzylisoquinoline alkaloid - tetrandrine. The plant is extensively referenced in the Chinese Pharmacopoeia for its use in the Chinese medicinal system as an analgesic and diuretic agent and also in the treatment of hypertension and various other ailments, including asthma, tuberculosis, dysentery, hyperglycemia, malaria, cancer and fever. Tetrandrine, well-known to act as a calcium channel blocker, has been tested in clinical trials and found effective against silicosis, hypertension, inflammation and lung cancer without any toxicity. Recently, the efficacy of tetrandrine was tested against Mycobaterium tuberculosis, Candida albicans, Plasmodium falciparum and Ebola virus. Tetrandrine's pharmacological property has been proved to be through its action on different signalling pathways like reactive oxygen species, enhanced autophagic flux, reversal of multi drug resistance, caspase pathway, cell cycle arrest and by modification of calcium channels. The present review summarises current knowledge on the synthesis, distribution, extraction, structural elucidation, pharmacological properties and the mechanism of action of tetrandrine. Future perspectives in the clinical use of tetrandrine as a drug are also considered.

Hurdles in selection process of nanodelivery systems for multidrug-resistant cancer

PURPOSE

Most of the nanomedicines for treatment of multidrug-resistant cancer do not reach Phase III trials and many are terminated or withdrawn or are in an indeterminate state since long without any study results being presented. Extensive perusal of nanomedicine development research revealed that one of the critical aspects influencing clinical outcomes and which requires diligent scrutiny is selection process of nanodelivery system.

METHODS

Research papers and articles published on development of nanodelivery systems for treatment of multidrug-resistant cancer were analyzed. Observations and conclusions noted by these researchers which might shed some light on poor clinical performance of nanocarriers were collated and summarized under observation section. Further research articles were studied to find possible solutions which may be applied to these particular problems for resolving them. The inferences of these findings were composed in Result section.

RESULT

Plausible solutions for the observed obstacles were noted as examples of novel formulations that can yield the following: better in vivo imaging, precise targeting and dosing of a specific site and specific cell type in a particular cancer, modulation of tumor surroundings, intonation of systemic effects and high reproducibility.

CONCLUSION

The angle of approach to the development of best nanosystem for a specific type of tumor needs to be spun around. Some of these changes can be brought about by individual scientists, some need to be established by collated efforts of scientists globally and some await advent of better technologies. Regardless of the stratagem, it can be said decisively that the schematics of development phase need rethinking.

Tetrandrine reverses epithelial-mesenchymal transition in bladder cancer by downregulating Gli-1

Hedgehog (Hh) signaling pathway is considered to play a crucial role in vertebrate development and carcinogenesis. Additionally, epithelial-mesenchymal transition (EMT) is a cellular process during which epithelial cells become mesenchymal-appearing cells, facilitating cancer metastasis and invasion. Accumulating evidence has indicated that the Hh signaling pathway could potentiate the epithelial-mesenchymal transition (EMT). In the present study, we demonstrated that tetrandrine, a bisbenzylisoquinoline alkaloid isolated from Stephaniae, exerts its anti-metastatic ability in bladder cancer cells by regulating GLI family zinc finger 1 (Gli-1), a key factor of Hedgehog signaling pathway. In our study, we confirmed that tetrandrine could impede migration and invasion in bladder cancer 5637 and T24 cells. Additionally, tetrandrine reverses EMT by increasing the expression of E-cadherin and reducing the N-cadherin, vimentin and Slug expression in a dose-dependent manner. Interestingly, tetrandrine also decreases mobility and reduces the expression of Gli-1 in bladder cancer cells. Moreover, we verified that tetrandrine inhibits metastasis and induces mesenchymal-epithelial transition (MET) of bladder cancer through downregulation of Gli-1, which could be partially reversed by Gli-1 overexpression. In conclusion, our findings show that tetrandrine inhibits migration and invasion, and reverses EMT of bladder cancer cells through negatively regulating Gli-1. It indicates that Gli-1 may be a potential therapeutic target of tetrandrine against bladder cancer.

Advances in plant-based inhibitors of P-glycoprotein

Multidrug resistance (MDR) has emerged as the main problem in anti-cancer therapy. Although MDR involves complex factors and processes, the main pivot is the expression of multidrug efflux pumps. P-glycoprotein (P-gp) belongs to the family of adenosine triphosphate (ATP)-binding cassette (ABC) transporters. It functions in cellular detoxification, pumping a wide range of xenobiotic compounds out of the cell. An attractive therapeutic strategy for overcoming MDR is to inhibit the transport function of P-gp and thus, increase intracellular concentration of drugs. Recently, various types of P-gp inhibitors have been found and used in experiments. However, none of them has passed clinical trials due to their high side-effects. Hence, the search for alternatives, such as plant-based P-gp inhibitors have gained attention recently. Therefore, we give an overview of the source, function, structure and mechanism of plant-based P-gp inhibitors and give more attention to cancer-related studies. These products could be the future potential drug candidates for further research as P-gp inhibitors.

Isotetrandrine Reduces Astrocyte Cytotoxicity in Neuromyelitis Optica by Blocking the Binding of NMO-IgG to Aquaporin 4

OBJECTIVE

Neuromyelitis optica (NMO) is a severe neurological demyelinating autoimmune disease that affects the optic nerves and spinal cord with no cure and no FDA-approved therapy. Research over the last decade revealed that the binding of NMO-IgG to the water channel protein astrocyte aquaporin 4 (AQP4) might be the primary cause of NMO pathogenesis. The purpose of this study was to identify potential blockers of NMO-IgG and AQP4 binding.

METHODS

We developed a two-step screening platform consisting of a reporter cell-based high-throughput screen assay and a cell viability-based assay. Purified NMO-IgG from NMO patient serum and transfected Chinese hamster lung fibroblast V79 cells stably expressing human M23-AQP4 were used for primary screening of 40,000 small molecule fractions from 500 traditional Chinese herbs.

RESULTS

Thirty-six positive fractions were identified, of which 3 active fractions (at 50 μg/ml) were found to be from the same Chinese traditional herb Mahonia japonica (Thunb.). A bioactivity-guided method based on a primary screening assay for blocking activity led to the isolation of an active single natural compound, isotetrandrine, from the 3 fractions. Our immunofluorescence staining results showed that isotetrandrine can block NMO-IgG binding to AQP4 without affecting the expression and function of AQP4. It can also inhibit NMO-IgG binding to astrocyte AQP4 in NMO patient sera and block NMO-IgG-dependent complement-mediated cytotoxicity with the IC50 at ∼3 μM.

CONCLUSIONS

The present study developed a cell-based high-throughput screen to identify small molecule inhibitors for NMO-IgG and AQP4 binding, and suggests a potential therapeutic value of isotetrandrine in NMO.

Inhibition on Proteasome β1 Subunit Might Contribute to the Anti-Cancer Effects of Fangchinoline in Human Prostate Cancer Cells

Fangchinoline is a bisbenzylisoquinoline alkaloid isolated from Radix Stephaniae tetrandrae S. Moore. Fangchinoline and its structure analogue, tetrandrine, exhibited direct binding affinity with recombinant human proteasome β1 subunit and also inhibited its activity in vitro. In cultured prostate PC-3 cells and LnCap cells, fangchinoline could dose-dependently inhibit cell proliferation and caspase-like activity of cellular proteasome which was mediated by proteasome β1 subunit. The inhibitive effect of fangchinoline on caspase-like activity of proteasome was also observed in purified human erythrocyte 20S proteasome. In PC-3 cells, fangchinoline induced cell cycle arrest at G0/G1 phase and apoptosis. Treatment of PC-3 tumor-bearing nude mice with fangchinoline inhibited tumor growth, induced apoptosis and also caused decrease in proteasome activities in tumor xenografts. Dose-dependent and time-dependent accumulation of ubiquitinated proteins and important proteasome substrates such as p27, Bax and IκB-α were observed in fangchinoline-treated cells. Over-expression of proteasome β1 subunit by plasmid transfection increased sensitivity of cells to the cytotoxicity of fangchinoline while knockdown of proteasome β1 subunit ameliorated cytotoxicity of fangchinoline in PC-3 cells. Results of the present study suggested that proteasome inhibition was involved in the anti-cancer effects of fangchinoline. Fangchinoline and its structure analogues might be new natural proteasome inhibitors targeting β1 subunit.

Modes of Action of Herbal Medicines and Plant Secondary Metabolites

Plants produce a wide diversity of secondary metabolites (SM) which serve them as defense compounds against herbivores, and other plants and microbes, but also as signal compounds. In general, SM exhibit a wide array of biological and pharmacological properties. Because of this, some plants or products isolated from them have been and are still used to treat infections, health disorders or diseases. This review provides evidence that many SM have a broad spectrum of bioactivities. They often interact with the main targets in cells, such as proteins, biomembranes or nucleic acids. Whereas some SM appear to have been optimized on a few molecular targets, such as alkaloids on receptors of neurotransmitters, others (such as phenolics and terpenoids) are less specific and attack a multitude of proteins by building hydrogen, hydrophobic and ionic bonds, thus modulating their 3D structures and in consequence their bioactivities. The main modes of action are described for the major groups of common plant secondary metabolites. The multitarget activities of many SM can explain the medical application of complex extracts from medicinal plants for more health disorders which involve several targets. Herbal medicine is not a placebo medicine but a rational medicine, and for several of them clinical trials have shown efficacy.

In silico identified targeted inhibitors of P-glycoprotein overcome multidrug resistance in human cancer cells in culture

Failure of cancer chemotherapies is often linked to the over expression of ABC efflux transporters like the multidrug resistance P-glycoprotein (P-gp). P-gp expression in cells leads to the elimination of a variety of chemically unrelated, mostly cytotoxic compounds. Administration of chemotherapeutics during therapy frequently selects for cells that over express P-gp and are therefore capable of robustly exporting diverse compounds, including chemotherapeutics, from the cells. P-gp thus confers multidrug resistance to a majority of drugs currently available for the treatment of cancers and diseases like HIV/AIDS. The search for P-gp inhibitors for use as co-therapeutics to combat multidrug resistances has had little success to date. In a previous study (Brewer et al., Mol Pharmacol 86: 716–726, 2014), we described how ultrahigh throughput computational searches led to the identification of four drug-like molecules that specifically interfere with the energy harvesting steps of substrate transport and inhibit P-gp catalyzed ATP hydrolysis in vitro. In the present study, we demonstrate that three of these compounds reversed P-gp-mediated multidrug resistance of cultured prostate cancer cells to restore sensitivity comparable to naïve prostate cancer cells to the chemotherapeutic drug, paclitaxel. Potentiation concentrations of the inhibitors were <3 μmol/L. The inhibitors did not exhibit significant toxicity to noncancerous cells at concentrations where they reversed multidrug resistance in cancerous cells. Our results indicate that these compounds with novel mechanisms of P-gp inhibition are excellent leads for the development of co-therapeutics for the treatment of multidrug resistances.

Tetrandrine is a potent cell autophagy agonist via activated intracellular reactive oxygen species

Background

Autophagy is an evolutionarily conserved cellular process that involves the lysosomal degradation of proteins and organelles and the recycling of cellular components to ensure cellular survival under external or internal stress. Numerous data has indicated that autophagy can be successfully targeted for the treatment of multiple cancers. We have previously demonstrated that tetrandrine, a bisbenzylisoquinoline alkaloid isolated from the broadly used Chinese medicinal herb Stephaniae tetrandrae, exhibits potent antitumor effects when used either alone or in combination with other drugs.

Results

In the present study, we showed that tetrandrine is a broad-spectrum potent autophagy agonist. Although low-dose tetrandrine treatment does not affect cell viability, it can potently induce autophagy in a variety of cell lines, including cancerous cells and nontumorigenic cells. The autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ), effectively blocked tetrandrine-induced autophagy. Moreover, tetrandrine significantly triggered the induction of mitophagy. The underlying mechanisms are associated with the tetrandrine-induced production of intracellular reactive oxygen species (ROS), which plays a critical role in tetrandrine-induced autophagy.

Conclusions

Here, we report that tetrandrine is a potent cell autophagy agonist and may have a wide range of applications in the fields of antitumor therapy and basic scientific research.

Significance of multidrug resistance gene-related proteins in the postoperative chemotherapy of gastric cancer

BACKGROUND

Multidrug resistance (MDR) is a serious problem in chemotherapy and is one of the main reasons for a poor outcome of gastric cancer. Study on the key proteins in multidrug resistance is necessary for the treatment of gastric cancer.

METHODS

The expression of ToPo II, MRP and GST-π in 119 gastric cancers was retrospectively examined, and the results were analyzed in correlation with clinicopathological data. ToPo II negative, MRP positive and GST-π positive were regarded as three risk factors which may be associated with chemotherapy resistance and poor prognosis. Patients were divided into two groups: high-risk group (≥2 risk factors) and the low-risk group (<2 risk factors), and the tumor recurrence and patients' survival time of the two groups were also analyzed.

RESULTS

The positive rates of ToPo II, MRP and GST-π were 73.9%, 42.9% and 51.3%, respectively. The positively correlation between the expression of MRP and GST-π had been found. A significant correlation was shown between ToPo II expression and the level of differentiation. Significant differences with GST-π expression were also found in relation to the sex and differentiation. In the high-risk group, the 3-year survival rate of patients with/without chemotherapy were 62.1% and 52.0%, 5-year survival rates were 44.8% and 40.0%, but the difference was not statistically significant (P>0.05). In the low-risk group, the 3-year survival rate of patients with/without chemotherapy were 81.2% and 51.5%, 5-year survival rates were 71.9% and 45.5%, and the difference was statistically significant (P<0.05).

CONCLUSIONS

Combined detection of MDR-related proteins ToPo II, MRP and GST-π may be prospectively valuable for postoperative individualized chemotherapy, and further predict the outcomes of gastric cancer patients.