Compounds from Chinese herbal medicines as reversal agents for P-glycoprotein-mediated multidrug resistance in tumours

Panax notoginseng saponins reverse steroid resistance in lupus nephritis: Involvement of the suppression of exosomal P-gp levels from lymphocytes to glomerular endothelial cells

Microangiopathy is the most basic pathological manifestation of lupus nephritis (LN), and glomerular endothelial cells (GECs) injury is an important pathological mechanism. LN patients with microangiopathy are prone to steroid resistance (SR). Our previous studies confirmed that Panax notoginseng saponins (PNS) could reverse SR by downregulating the expression of P-gp in SR lymphocytes of LN mice (SLCsL/S). However, the mechanism of how circulating lymphocytes transmit SR information to GECs and thus affect the efficacy of kidney treatment is not clear. Recent studies have found that exosomes (exos) are an important carrier for intercellular bioactive substance communication. But whether exosomes derived from SLCsL/S mediate SR in GECs and PNS interventions. To solve this problem, Exosomes isolated from SLCsL/S were characterized, and in vitro cell coculture was further conducted to investigate the effect of SLCsL/S-derived exosomes in the SR of GECs and PNS intervention. Sequencing was used to define the exosomal miRNA expression profiling of SR GECs. Moreover, the in vivo experiments were performed through the injection of exosomes extracted from SLCsL/S into the tail vein of mice. Our research results indicate that exosomes derived from SLCsL/S could transmit SR information to GECs and lead to the aggravation of inflammatory injury through conferring P-gp, which were negated by a P-gp inhibitor. Further, we identified higher levels of exosomal miR-125b-5p from SR GECs were associated with SR in LN and could serve as biomarker for the risk of developing SR. PNS could reverse the SR of GECs and alleviate inflammatory injury by suppressing exosomal P-gp levels from lymphocytes to GECs in vitro and in vivo. However, the specific molecular mechanism by which PNS regulates exosomes has not yet been elucidated, and we need to conduct more in-depth research in the future. Overall, Our findings suggest that exosomal transfer of SLCsL/S derived P-gp confer SR to GECs, and PNS can target exosome communication to reverse SR in LN, which provides new ideas and a scientific basis for improving the clinical efficacy of traditional Chinese medicine in the treatment of refractory LN.

Biodiversity: the overlooked source of human health

Biodiversity is the measure of the variation of lifeforms in a given ecological system. Biodiversity provides ecosystems with the robustness, stability, and resilience that sustains them. This is ultimately essential for our survival because we depend on the services that natural ecosystems provide (food, fresh water, air, climate, and medicine). Despite this, human activity is driving an unprecedented rate of biodiversity decline, which may jeopardize the life-support systems of the planet if no urgent action is taken. In this article we show why biodiversity is essential for human health. We raise our case and focus on the biomedicine services that are enabled by biodiversity, and we present known and novel approaches to promote biodiversity conservation.

A Novel Drug Modulator Diarylheptanoid (trans-1,7-Diphenyl-5-hydroxy-1-heptene) from Curcuma comosa Rhizomes for P-glycoprotein Function and Apoptosis Induction in K652/ADR Leukemic Cells

Curcuma comosa has been used in traditional Thai medicine to treat menstrual cycle-related symptoms in women. This study aims to evaluate the diarylheptanoid drug modulator, trans-1,7-diphenyl-5-hydroxy-1-heptene (DHH), in drug-resistant K562/ADR human leukemic cells. This compound was studied due to its effects on cell cytotoxicity, multidrug resistance (MDR) phenotype, P-glycoprotein (P-gp) expression, and P-gp function. We show that DHH itself is cytotoxic towards K562/ADR cells. However, DHH did not impact P-gp expression. The impact of DHH on the MDR phenotype in the K562/ADR cells was determined by co-treatment of cells with doxorubicin (Dox) and DHH using an MTT assay. The results showed that the DHH changed the MDR phenotype in the K562/ADR cells by decreasing the IC₅₀ of Dox from 51.6 to 18.2 µM. Treating the cells with a nontoxic dose of DHH increased their sensitivity to Dox in P-gp expressing drug-resistant cells. The kinetics of P-gp mediated efflux of pirarubicin (THP) was used to monitor the P-gp function. DHH was shown to suppress THP efflux and resulted in enhanced apoptosis in the K562/ADR cells. These results demonstrate that DHH is a novel drug modulator of P-gp function and induces drug accumulation in the Dox-resistant K562 leukemic cell line.

Fabrication of Ginsenoside-Based Nanodrugs for Enhanced Antitumor Efficacy on Triple-Negative Breast Cancer

There is an urgent need to identify chemotherapeutic agents with improved efficacy and safety against triple-negative breast cancer (TNBC). Ginsenosides can reportedly induce tumor cell death, invasion, and metastasis; however, poor water solubility, low oral absorption rate, and rapid blood clearance limit their clinical application. Utilizing the amphiphilic property of ginsenosides as building blocks of biomaterials, we fabricated a carrier-free nanodrug composed of ginsenosides Rg3 and Rb1 using a nano-reprecipitation method without any additional carriers. After characterizing and demonstrating their uniform morphology and pH-sensitive drug release properties, we observed that Rg3-Rb1 nanoparticles (NPs) exhibited stronger antitumor and anti-invasive effects on TNBCs in vitro than those mediated by free ginsenosides. Consequently, Rg3-Rb1 NPs afforded superior inhibition of tumor growth and reduction of pulmonary metastasis than the Rg3 and Rb1 mixture, with no obvious systematic toxicity in vivo. Collectively, our results provide a proof-of-concept that self-assembled engineered ginsenoside nanodrugs may be efficient and safe for TNBC therapy.

Panax notoginseng saponins reverse P-gp-mediated steroid resistance in lupus: involvement in the suppression of the SIRT1/FoxO1/MDR1 signalling pathway in lymphocytes

Background

P-glycoprotein (P-gp)-mediated steroid resistance (SR) has been suggested to play a significant role in lupus nephritis (LN) treatment failure. Panax notoginseng saponins (PNS), the main effective components of the traditional Chinese medicine notoginseng, exhibited potent reversal capability of P-gp-mediated SR, but its mechanism remains unknown. This study aimed to investigate the effect of PNS on reversing SR in lupus and its underlying mechanism in vivo and in vitro.

Methods

In this study, an SR animal and splenic lymphocyte model were established using low-dose methylprednisolone (MP). Flow cytometry was used to detect the effect of PNS on reversing P-gp-mediated SR and the expression of P-gp in different T-cells phenotypes. Serum levels of ANA and dsDNA in lupus mice were measured by ELISA. Apoptosis was identified by Annexin V-FITC/PI staining. RT–PCR and Western blotting were used to detect the protein and mRNA expression levels of SIRT1, FoxO1, and MDR1 in SR splenic lymphocytes from lupus mice (SLCs/MPs).

Results

PNS could reverse the SR in lupus mice. Simultaneously, PNS increased the apoptotic effect of MP on SLCs/MP cells. The increased accumulation of rhodamine-123 (Rh-123) indicated that intracellular steroid accumulation could be increased by the action of PNS. Moreover, PNS decreased the expression of P-gp levels. Further experiments elucidated that the SIRT1/FoxO1/MDR1 signalling pathway existed in SLCs/MP cells, and PNS suppressed its expression level to reverse SR. The expression of P-gp in Th17 from SLCs/MP cells was increased, while PNS could reduce its level in a more obvious trend.

Conclusion

The present study suggested that PNS reversed P-gp-mediated SR via the SIRT1/FoxO1/MDR1 signalling pathway, which might become a valuable drug for the treatment of SR in lupus. Th17 might be the main effector cell of PNS reversing SR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03499-5.

New Advances in the Research of Resistance to Neoadjuvant Chemotherapy in Breast Cancer

Breast cancer has an extremely high incidence in women, and its morbidity and mortality rank first among female tumors. With the increasing development of medicine today, the clinical application of neoadjuvant chemotherapy has brought new hope to the treatment of breast cancer. Although the efficacy of neoadjuvant chemotherapy has been confirmed, drug resistance is one of the main reasons for its treatment failure, contributing to the difficulty in the treatment of breast cancer. This article focuses on multiple mechanisms of action and expounds a series of recent research advances that mediate drug resistance in breast cancer cells. Drug metabolizing enzymes can mediate a catalytic reaction to inactivate chemotherapeutic drugs and develop drug resistance. The drug efflux system can reduce the drug concentration in breast cancer cells. The combination of glutathione detoxification system and platinum drugs can cause breast cancer cells to be insensitive to drugs. Changes in drug targets have led to poorer efficacy of HER2 receptor inhibitors. Moreover, autophagy, epithelial–mesenchymal transition, and tumor microenvironment can all contribute to the development of resistance in breast cancer cells. Based on the relevant research on the existing drug resistance mechanism, the current treatment plan for reversing the resistance of breast cancer to neoadjuvant chemotherapy is explored, and the potential drug targets are analyzed, aiming to provide a new idea and strategy to reverse the resistance of neoadjuvant chemotherapy drugs in breast cancer.

Replacing the eleven native tryptophans by directed evolution produces an active P-glycoprotein with site-specific, non-conservative substitutions

P-glycoprotein (Pgp) pumps an array of hydrophobic compounds out of cells, and has major roles in drug pharmacokinetics and cancer multidrug resistance. Yet, polyspecific drug binding and ATP hydrolysis-driven drug export in Pgp are poorly understood. Fluorescence spectroscopy using tryptophans (Trp) inserted at strategic positions is an important tool to study ligand binding. In Pgp, this method will require removal of 11 endogenous Trps, including highly conserved Trps that may be important for function, protein-lipid interactions, and/or protein stability. Here, we developed a directed evolutionary approach to first replace all eight transmembrane Trps and select for transport-active mutants in Saccharomyces cerevisiae. Surprisingly, many Trp positions contained non-conservative substitutions that supported in vivo activity, and were preferred over aromatic amino acids. The most active construct, W(3Cyto), served for directed evolution of the three cytoplasmic Trps, where two positions revealed strong functional bias towards tyrosine. W(3Cyto) and Trp-less Pgp retained wild-type-like protein expression, localization and transport function, and purified proteins retained drug stimulation of ATP hydrolysis and drug binding affinities. The data indicate preferred Trp substitutions specific to the local context, often dictated by protein structural requirements and/or membrane lipid interactions, and these new insights will offer guidance for membrane protein engineering.

The Application of Nanotechnology in the Codelivery of Active Constituents of Plants and Chemotherapeutics for Overcoming Physiological Barriers during Antitumor Treatment

Antitumor therapy using a combination of drugs has shown increased clinical efficacy. Active constituents derived from plants can offer several advantages, such as high efficiacy, low toxicity, extensive effects, and multiple targets. At present, the combination of plants' active constituents and chemotherapeutic drugs has attracted increased attention. Nanodrug delivery systems (NDDSs) have been widely used in tumor-targeted therapy because of their efficacy of delivering antitumor drugs. The in vivo process of tumor-targeted NDDSs has several steps. They include blood circulation, tumor accumulation and penetration, target cell internalization and uptake, and drug release and drug response. In each step, NDDSs encounter multiple barriers that prevent their effective delivery to target sites. Studies have been performed to find alternative strategies to overcome these barriers. We reviewed the recent progress of codelivery of active constituents of plants and chemotherapeutics using NDDSs. Progress into transversing the physiological barriers for more effective in vivo antitumor delivery will be discussed in this review.

Interactions between artemisinin derivatives and P-glycoprotein

BACKGROUND

Artemisinin was isolated and identified in 1972, which was the starting point for a new era in antimalarial drug therapy. Furthermore, numerous studies have demonstrated that artemisinin and its derivatives exhibit considerable anticancer activity both in vitro, in vivo, and even in clinical Phase I/II trials. P-glycoprotein (P-gp) mediated multi-drug resistance (MDR) is one of the most serious causes of chemotherapy failure in cancer treatment. Interestingly, many artemisinin derivatives exhibit excellent ability to overcome P-gp mediated MDR and even show collateral sensitivity against MDR cancer cells. Furthermore, some artemisinin derivatives show P-gp-mediated MDR reversal activity. Therefore, the interaction between P-gp and artemisinin derivatives is important to develop novel combination treatment protocols with artemisinin derivatives and established anticancer drugs that are P-gp substrates.

PURPOSE

This systematic review provides an updated overview on the interaction between artemisinin derivatives and P-gp and the effect of artemisinin derivatives on the P-gp expression level.

RESULTS

Artemisinin derivatives exhibit multi-specific interactions with P-gp. The currently used artemisinin derivatives are not transported by P-gp. However, some of novel synthetized artemisinin derivatives exhibit P-gp substrate properties. Furthermore, many artemisinin derivatives act as P-gp inhibitors, which exhibit the potential to reverse MDR towards clinically used anticancer drugs.

CONCLUSION

Therefore, studies on the interaction between artemisinin derivatives and P-gp provide important information for the development of novel anti-cancer artemisinin derivatives to reverse P-gp mediated MDR and for the design of rational artemisinin-based combination therapies against cancer.

A candidate for lung cancer treatment: arsenic trioxide

Arsenic trioxide (ATO), a highly effective drug in treating acute promyelocytic leukemia with low toxicity, demonstrates a significant effect on lung cancer. The anti-cancer mechanisms of ATO include inhibition of cancer stem-like cells, induction of apoptosis, anti-angiogenesis, sensitization of chemotherapy and radiotherapy, anti-cancer effects of hypoxia, and immunoregulation properties. In addition, some studies have reported that different lung cancers respond differently to ATO. It was concluded on numerous studies that the rational combination of administration and encapsulation of ATO have promising potentials in increasing drug efficacy and decreasing adverse drug effects. We reviewed the efficacy of ATO in the treatment of lung cancer in recent years to provide some views for further study.

Galbanic acid potentiates TRAIL induced apoptosis in resistant non-small cell lung cancer cells via inhibition of MDR1 and activation of caspases and DR5

Galbanic acid (GBA) is known a sesquiterpene coumarin to have apoptotic, anti-hypoxic, anti-proliferative, anti-hepatitis, anti-angiogenic, anti-bacteria and anti-thrombotic effects. Also, antitumor effect of GBA was reported in prostate, ovary, breast and lung cancers. Nevertheless, the underlying molecular mechanism of GBA was not fully understood to overcome chemoresistance in resistant lung cancer so far. Thus, synergistic antitumor mechanism of GBA and TNF-related apoptosis-inducing ligand (TRAIL) was elucidated in H460 and resistant H460/R non-small cell lung cancer cells (NSCLCs). Combination of GBA and TRAIL significantly exerted cytotoxicity in a dose dependent manner compared to GBA or TRAIL alone in H460/R cells. Also, GBA and TRAIL significantly increased the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cells and sub-G1 population in a dose dependent manner in H460/R cells. Consistently, GBA and TRAIL induced cleavages of poly (ADP-ribose) polymerase (PARP), caspase-9 and caspase-8 along with upregulation of death receptor 5 (DR5) and also attenuated the expression of B-cell lymphoma-extra-large (Bcl-x_L), B-cell lymphoma 2 (Bcl-2), X-linked inhibitor of apoptosis protein (XIAP) in H460/R cells. Furthermore, combination of GBA and TRAIL remarkably inhibited the expression of decoy receptor 1 (DcR1) and multidrug resistance 1(MDR1) in H460/R cells. Consistently, GBA and TRAIL effectively maintained Rhodamine 123 accumulation in H460/R cells compared to GBA or TRAIL alone by blocking multidrug efflux pump from the cells. Overall, our findings suggest that galbanic acid enhances TRAIL induced apoptosis via inhibition of MDR1 and activation of caspases and DR5 in H460/R cells as a potent TRAIL sensitizer.

Reversal Effect of Oxypeucedanin on P-glycoprotein-mediated Drug Transport

P-glycoprotein affects the transport of numerous drugs including chemotherapeutic drugs vincristine sulfate (VCR) and docetaxel (DTX), and is one of the main causes for multidrug resistance. Our previous studies have shown that oxypeucedanin (OPD) can enhance the intestinal transit of puerarin and VCR. However, the underlying mechanism is unclear. This study investigated the potential mechanism by which OPD improves P-gp-mediated drug transport. Molecular docking was performed to predict the binding force between OPD and P-gp and the contribution of OPD on P-gp activity. We observed the effect of OPD on the transport of VCR in MDCK-MDR1 cell monolayer and also measured the plasma pharmacokinetic parameters of DTX in the presence and absence of OPD by LC-MS/MS. Moreover, we further investigated the reversal mechanism of OPD on P-gp-mediated drug transport by determining the intracellular accumulation of Rhodamine-123 (Rh123) and P-gp ATPase activity as well as protein expression and mRNA level of P-gp. Our molecular docking results revealed that the binding force between OPD and P-gp was much lower than that between P-gp and verapamil (a P-gp substrate). The transport study in vitro indicated that OPD increased the flux of VCR across MDCK-MDR1 cell monolayer. The in vivo pharmacokinetic parameters data showed OPD increased the absorption of DTX. OPD activated P-gp ATPase activity and enhanced intracellular accumulation of Rh123 in MDCK-MDR1 cells. Western blotting and qRT-PCR outcomes indicated that OPD suppressed P-gp protein expression as well as downregulated P-gp mRNA level. Thus, OPD reverse P-gp-mediated drug transport via inhibition of P-gp activity and P-gp protein expression as well as downregulation of P-gp mRNA level. Our results suggest that OPD could reverse P-gp-mediated drug resistance in tumor cells.

Research Progress on Reversing Multidrug Resistance in Tumors by Using Chinese Medicine

Multidrug resistance (MDR) is a major cause of cancer chemotherapy failure, and it is important to develop suitable reversal agents to overcome MDR. A majority of chemical reversal agents have acceptable reversal effects. However, the toxicity and adverse reactions associated with these agents restricts their clinical use. Chinese medicines (CMs) have lower toxicities and adverse reactions and are associated with multiple components, multiple targets and reduced toxicity. CMs have several advantages and could reverse MDR, decrease drug dosage, enhance patient compliance and increase efficacy. This review summarizes the current progress of CM reversal agents..

Euphorbia lunulata extract acts on multidrug resistant gastric cancer cells to inhibit cell proliferation, migration and invasion, arrest cell cycle progression, and induce apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

The milky sap or the aboveground part of the plant Euphorbia lunulata has long been used by Chinese people to treat noncancerous growths and cancerous ailments but the specific mode of action and the action mechanism remain to be elucidated.

AIM OF THE STUDY

To investigate the effects of Euphorbia lunulata extract on cell proliferation, migration, invasion, cell cycle progression, and apoptosis of multidrug resistant human gastric cancer cells; To study the mechanism of apoptosis induction by Euphorbia lunulata extract in multidrug resistant human gastric cancer cells.

MATERIALS AND METHODS

The aboveground part of fresh Euphorbia lunulata plant was extracted first with ethanol and then with n-hexane. The aseptic extract at varying concentrations was used to treat the multidrug resistant human gastric cancer SGC7901/ADR cells. After treatment, the inhibition of cell proliferation was examined by MTT assay. The inhibitions of cell migration and invasion were detected by Transwell method. The alteration of cell cycle progression was studied by flow cytometry. The morphological changes of cell nuclei were observed with fluorescence microscopy following Hoechst 33258 staining and the apoptotic indexes were calculated. The activation of caspase enzymes was analyzed by spectrophotometry. The sub-cellular distribution of cytochrome complex and the expression of Bax and Bcl-2 proteins were determined by Western blot.

RESULTS

The proliferation, migration, and invasion of SGC7901/ADR cells were significantly inhibited by Euphorbia lunulata extract, which showed time- and dose-dependent manners. Cell cycle was arrested in G2/M phase. Significant apoptotic morphological changes were observed in the nuclei of the treated cells, and apoptotic indexes were increased significantly; these changes were diminished when Z-VAD-FMK, a caspase inhibitor, was also presented. The activities of caspase-3, caspase-8, and caspase-9 were increased. The sub-cellular distribution of cytochrome complex was altered----reduced in the mitochondria and increased in the cytoplasm. The expression of Bax was upregulated, while that of Bcl-2 was downregulated.

CONCLUSION

Euphorbia lunulata extract inhibited the proliferation, migration, and invasion of SGC7901/ADR cells, arrested cell cycle progression, and induced cell apoptosis; the mechanism of apoptosis induction involved both the extrinsic and the intrinsic pathways.

Targeting P-glycoprotein: Investigation of piperine analogs for overcoming drug resistance in cancer

P-glycoprotein (P-gp) is a drug transporter that effluxes chemotherapeutic drugs and is implicated in the development of resistance of cancer cells to chemotherapeutic drugs. To date, no drug has been approved to inhibit P-gp and restore chemotherapy efficacy. Moreover, majority of the reported inhibitors have high molecular weight and complex structures, making it difficult to understand the basic structural requirement for P-gp inhibition. In this study, two structurally simple, low molecular weight piperine analogs Pip1 and Pip2 were designed and found to better interact with P-gp than piperine in silico. A one step, acid-amine coupling reaction between piperic acid and 6,7-dimethoxytetrahydroisoquinoline or 2-(3,4-dimethoxyphenyl)ethylamine afforded Pip1 and Pip2, respectively. In vitro testing in drug resistant P-gp overexpressing KB (cervical) and SW480 (colon) cancer cells showed that both analogs, when co-administered with vincristine, colchicine or paclitaxel were able to reverse the resistance. Moreover, accumulation of P-gp substrate (rhodamine 123) in the resistant cells, a result of alteration of the P-gp efflux, was also observed. These investigations suggest that the natural product analog - Pip1 ((2E,4E)-5-(benzo[d][1,3]dioxol-5-yl)-1-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1 H)-yl)penta-2,4-dien-1-one) - is superior to piperine and could inhibit P-gp function. Further studies are required to explore the full potential of Pip1 in treating drug resistant cancer.

Codelivery of dihydroartemisinin and doxorubicin in mannosylated liposomes for drug-resistant colon cancer therapy

Multidrug resistance (MDR) is a major hurdle in cancer chemotherapy and makes the treatment benefits unsustainable. Combination therapy is a commonly used method for overcoming MDR. In this study we investigated the anti-MDR effect of dihydroartemisinin (DHA), a derivative of artemisinin, in combination with doxorubicin (Dox) in drug-resistant human colon tumor HCT8/ADR cells. We developed a tumor-targeting codelivery system, in which the two drugs were co-encapsulated into the mannosylated liposomes (Man-liposomes). The Man-liposomes had a mean diameter of 158.8 nm and zeta potential of -15.8 mV. In the HCT8/ADR cells that overexpress the mannose receptors, the Man-liposomes altered the intracellular distribution of Dox, resulting in a high accumulation of Dox in the nuclei and thus displaying the highest cytotoxicity (IC₅₀=0.073 μg/mL) among all the groups. In a subcutaneous HCT8/ADR tumor xenograft model, administration of the Man-liposomes resulted in a tumor inhibition rate of 88.59%, compared to that of 47.46% or 70.54%, respectively, for the treatment with free Dox or free Dox+DHA. The mechanisms underlying the anti-MDR effect of the Man-liposomes involved preferential nuclear accumulation of the therapeutic agents, enhanced cancer cell apoptosis, downregulation of Bcl-xl, and the induction of autophagy.

Inhibition of paclitaxel resistance and apoptosis induction by cucurbitacin B in ovarian carcinoma cells

Ovarian cancer is the leading cause of mortality among all gynecological malignancies. Drug resistance is a cause of ovarian cancer recurrence and low rate of overall survival. There is a requirement for more effective treatment approaches. Cucurbitacin B (CuB) is an antineoplastic agent derived from traditional Chinese medicinal herbs. Its activity against paclitaxel-resistant human ovarian cancer cells has, however, not yet been established. The purpose of the present study was to investigate the effect and mechanism of CuB on human paclitaxel-resistant ovarian cancer A2780/Taxol cells. Cell viability was evaluated by a cell counting assay, while cell cycle arrest and apoptosis were assessed by microscopy and flow cytometry, and proteins associated with apoptotic pathways and drug resistance were evaluated by western blotting. The present results demonstrated that CuB exerts dose- and time-dependent cytotoxicity against the ovarian cancer A2780 cell line, with half-maximal inhibitory concentration (IC₅₀) values 0.48, 0.25 and 0.21 µM following 24, 48 and 72 h of incubation, respectively. Compared with its sensitive counterpart, A2780, paclitaxel-resistant A2780/Taxol cells had almost identical IC₅₀ values. Cell cycle analysis demonstrated that treatment with CuB may induce cell cycle arrest at the G₂/M phase of the cell cycle in the two cell lines. As revealed by Annexin V/propidium iodide-labeled flow cytometry and Hoechst 33258 staining, CuB-induced apoptosis was accompanied by activation of caspase-3 and downregulation of B-cell lymphoma-2. Western blotting demonstrated that CuB may enhance the expression of p53 and p21 in the two cell lines. CuB may also downregulate the expression of P-glycoprotein. These results indicate that CuB may exert a therapeutic effect on paclitaxel-resistant human ovarian cancer.

Tuberostemonine reverses multidrug resistance in chronic myelogenous leukemia cells K562/ADR

Objective: To investigate the reversal effect of tuberostemonine on MDR in myelogenous leukemia cells K562/ADR.

Methods: Human myelogenous leukemia cells K562 and their adriamycin-resistance cells K562/ADR were used. The growth curve of cells treated by tuberostemonine and the Non-toxic concentration of tuberostemonine were determined by MTT, Cell apoptosis was determined by MTT and flow cytometry. The expression of MDR1, Survivin and Livin was detected by RT-PCR. The activity of P-gp was detected by flow cytometry. Western blot was used to detect the expression of NF-κB and Survivin.

Results: The effect of tuberostemonine on K562/ADR showed a dose-dependence, and 350μg/mL and 500μg/mL of tuberostemonine could inhibit the expression of MDR1 (P<0.05). While no function difference of P-gp was detected. With the increased concentration of tuberostemonine, the inhibitory effect were enhanced to the expression of NF-κB. Tuberostemonine combined with adriamycin could time-dependently inhibit the cell proliferation (P<0.05) and obviously promoted the cell apoptosis (P<0.05). Also the tuberostemonine could inhibit the expression of Survivin.

Conclusion: There are no direct relations between tuberostemonine and P-gp, but tuberostemonine could reverse the multidrug resistance of K562/ADR via down-regulating the expression of Nf-κB and inhibiting th1e expression of Survivin.

Reversal of P-glycoprotein-mediated multidrug resistance is induced by saikosaponin D in breast cancer MCF-7/adriamycin cells

Multidrug resistance (MDR) cells over expressing P-glycoprotein (P-gp) encoded by the MDR1 gene is major obstacles for successful cancer chemotherapy. P-gp could extrude anti-cancer drugs out of cancer cells and decrease effective intracellular drug concentrations. MDR reversal agents for P-gp can restore the sensitivity of MDR cells to such drugs. Saikosaponin D (SSd), one of the major triterpenoid saponins derived from Bupleurum chinense DC (BCDC), has been shown to possess anti-inflammatory, anti-infectious and anti-tumor properties. The aim of the present study was to investigate the reversal effect of SSd on MDR in MCF-7/adriamycin (ADR) human breast cancer cells and investigate the underlying mechanisms of SSd. The results demonstrated that SSd inhibited the proliferation of MCF-7/ADR and MCF-7 cells in a dose-dependent manner. Moreover, SSd increased the cytotoxicity of ADR on MCF-7/ADR cells and the resistance fold of SSd treatment was demonstrated to be significantly higher when compared with that of the group without SSd treatment. Additionally, the effects of the drug combination showed that SSd and ADR combination were synergistic. Accumulation and efflux studies with the P-gp substrate, rhodamine 123 (Rh123), demonstrated that SSd restored Rh123 accumulation and inhibited P-gp-mediated drug efflux. Importantly, we found that SSd could enhance the sensitivity of MCF-7/ADR cells towards ADR by down-regulating MDR1 and P-gp expression. In conclusion, the results of the present study indicated that SSd may represent a potent reversal agent for P-gp-mediated MDR in breast cancer therapy.

Triptolide exerts pro-apoptotic and cell cycle arrest activity on drug-resistant human lung cancer A549/Taxol cells via modulation of MAPK and PI3K/Akt signaling pathways

Multidrug resistance (MDR) is a major obstacle in the effective chemotherapeutic treatment of cancers. Triptolide (TPL) is a diterpenoid isolated from Tripterygium wilfordii Hook. f., a traditional Chinese medicine. It was demonstrated in our previous study that TPL exerts anti-MDR cancers on various MDR cell lines (including A549/Taxol, MCF-7/ADR and Bel7402/5-Fu). The present study was designed to investigate its anti-proliferative activity on A549/Taxol cells, and explore the underlying mechanism of action. The anti-proliferative activity of TPL on A549/Taxol cells was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Its pro-apoptosis and cell cycle arrest activities were analyzed by flow cytometry. Western blot assay was employed to investigate the levels of mitogen-activated protein kinases (MAPKs) and apoptosis-related proteins in cells. TPL efficiently suppressed the proliferation of A549/Taxol cells. Co-treatment with MAPK inhibitors in the MTT assay indicated that the extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) pathways were involved in the process. Upregulation of p-p38, p-ERK, p-GSK-3β, Bax and cleaved caspases-3 and -9, and downregulation of p-JNK, p-Akt and Bcl-2 were observed upon treatment with TPL in the A549/Taxol cells. The results from flow cytometry assay revealed that TPL induced apoptosis and S-phase arrest in A549/Taxol cells. This occurred as a result of the upregulation of p-ERK and p-GSK-3β, and the downregulation of p-JNK and p-Akt, and was responsible for the subsequent anti-proliferative activity.

A polymethoxyflavone from Laggera pterodonta induces apoptosis in imatinib-resistant K562R cells via activation of the intrinsic apoptosis pathway

Background

Treatment with imatinib mesylate (IM) (a tyrosine kinase inhibitor) is the first line of standard care for patients newly diagnosed with CML. Despite the success of IM and other tyrosine kinase inhibitors (TKIs), chronic myeloid leukemia (CML) remains largely incurable, and a number of CML patients die due to Abl mutation-related drug resistance and blast crisis. 3, 5-Dihydroxy-6, 7, 3′4′-tetramethoxyflavone (DHTMF) is a polymethoxyflavone isolated from Laggera pterodonta which is a herbal medicine used to treat cancer in the Chinese folk. In the previous study, we found DHTMF demonstrated good antiproliferative activities against a number of cancer cell lines and induced the apoptosis of CNE cells in vitro in a time- and dose-dependent manner while exhibiting low cytotoxicity in the two normal cell lines Vero and EVC304. The aim of the present study was to evaluate the proliferation inhibition and apoptosis induced by DHTMF alone and in combination with IM in the IM-resistant CML cell line K562R.

Methods

Cell proliferation was assayed with the cell counting kit-8 (CCK8) method. The apoptosis percentage was determined by flow cytometry (FCM). Mitochondrial transmembrane potential was detected using FCM and confocal laser-scanning microscopy. The level of proteins involved in apoptosis was detected by Western blotting.

Results

DHTMF suppressed K562R cell viability in both time- and dose-dependent manners. DHTMF combined with IM enhanced the inhibitory effects and apoptosis in K562R cells as compared with DHTMF alone. DHTMF alone and in combination with IM significantly decreased the mitochondrial membrane potential and increased the levels of cleaved caspase-9, caspase-7, caspase-3, and PARP in K562R cells.

Conclusions

We demonstrated that DHTMF could inhibit IM-resistant K562R cell proliferation and induces apoptosis via the intrinsic mitochondrial apoptotic pathway. These results suggest that DHTMF may be a potential therapeutic drug with lower side effects against IM resistance in CML cells.