Reversal effect of tyroservatide (YSV) tripeptide on multi-drug resistance in resistant human hepatocellular carcinoma cell line BEL-7402/5-FU

Enzyme-instructed self-assembly (EISA) assists the self-assembly and hydrogelation of hydrophobic peptides

Enzyme-instructed self-assembly (EISA) has several advantages in the preparation of supramolecular self-assembly materials for biomedical applications. In this study, we demonstrated that the enzyme-instructed self-assembly (EISA) strategy could assist the self-assembly and hydrogelation of two hydrophobic and bioactive peptides, tyroservatide (YSV) and laminin pentapeptide (YIGSR). We first synthesized the peptide derivatives of Nap-GFFYSV (peptide 1) and Nap-GFFYIGSR (peptide 2) and found that both peptides could not self-assemble into hydrogels due to their poor solubility. We therefore designed the phosphorylated precursors of the two hydrophobic peptides, Nap-GFFpYSV (precursor 1) and Nap-GFFpYIGSR (precursor 2), respectively, which had good solubility and can be dephosphorylated by alkaline phosphatase (ALP) to form supramolecular hydrogels. In addition, we found that the EISA could also occur on the surface of cells that overexpress ALP. The EISA strategy was a powerful method to generate hydrogels of hydrophobic compounds. We envision the big promise of the strategy in the preparation of biomaterials and nanomaterials of hydrophobic bioactive molecules.

FV-429 enhances the efficacy of paclitaxel in NSCLC by reprogramming HIF-1α-modulated FattyAcid metabolism

Solid tumors often exhibit hypoxia in their centers, which has been associated with a marked reduction in the sensitivity of the tumor cells to anti-tumor and chemotherapeutic interventions. Here, we found that the occurrence and progress of hypoxic insensitivity to paclitaxel in non-small cell lung cancer (NSCLC) are closely associated with the HIF-1α pathway. The HIF-1α protein upregulated the expression of adipose differentiation-related protein (ADRP), fatty acid synthase (FASN), and sterol regulatory element binding protein 1(SREBP1), while simultaneously downregulating carnitine palmitoyltransferase 1 (CPT1), thereby leading to a more pronounced uptake of lipids and reduced oxidation of fatty acids. Diminished levels of fatty acids led to reduced Wnt pathway activation and β-catenin nuclear translocation, leading to G2/M cell cycle arrest. In this study, FV-429, a derivative of the natural flavonoid wogonin, reprogrammed metabolism of cancer cells and decreased fatty acid levels. Moreover, paclitaxel-induced G2/M phase arrest in hypoxia-resistant NSCLC was hampered but FV-429 improved the sensitivity of these cancer cells to paclitaxel. FV-429 activated and modulated fatty acid metabolism in NSCLC cells, significantly reduced levels of fatty acids within cells and increased the oxidation of these fatty acids. The results of our study demonstrated that FV-429 could reshape fatty acid metabolism in hypoxia-induced paclitaxel-resistant NSCLC and enhance the sensitivity of NSCLC cells to paclitaxel through G2/M phase arrest deterioration, by inactivating the Wnt pathway, and suggested the possibility of using FV-429 as a promising candidate therapeutic agent for advanced NSCLC.

Enhanced anticancer effect of doxorubicin by TPGS-coated liposomes with Bcl-2 siRNA-corona for dual suppression of drug resistance

Multiple drug resistance (MDR) is a tough problem in developing hepatocellular carcinoma (HCC) therapy. Here, we developed TPGS-coated cationic liposomes with Bcl-2 siRNA corona to load doxorubicin (Dox) i.e., Bcl-2 siRNA/Dox-TPGS-LPs, to enhance anticancer effect of Dox in HCC-MDR. TPGS i.e., d-α-tocopheryl polyethylene glycol 1000 succinate, inhibited P-glycoprotein (P-gp) efflux pump and Bcl-2 siRNA suppressed anti-apoptotic Bcl-2 protein. The Bcl-2 siRNA loaded in the liposomal corona was observed under transmission electron microscopy. The stability and hemolysis evaluation demonstrated Bcl-2 siRNA/Dox-TPGS-LPs had good biocompatibility and siRNA-corona could protect the liposomal core to avoid the attachment of fetal bovine serum. In drug-resistant cells, TPGS effectively prolonged intracellular Dox retention time and siRNA-corona did improve the internalization of Dox from liposomes. In vitro and in vivo anticancer effect of this dual-functional nanostructure was examined in HCC-MDR Bel7402/5-FU tumor model. MTT assay confirmed the IC₅₀ value of Dox was 20–50 fold higher in Bel7402/5-FU MDR cells than that in sensitive Bel7402 cells. Bcl-2 siRNA corona successfully entered the cytosol of Bel7402/5-FU MDR cells to downregulate Bcl-2 protein levels in vitro and in vivo. Bcl-2 siRNA/Dox-TPGS-LPs showed superior to TPGS- (or siRNA-) linked Dox liposomes in cell apoptosis and cytotoxicity assay in Bel7402/5-FU MDR cells, and 7-fold greater effect than free Dox in tumor growth inhibition of Bel7402/5-FU xenograft nude mice. In conclusion, TPGS-coated cationic liposomes with Bcl-2 siRNA corona had the capacity to inhibit MDR dual-pathways and subsequently improved the anti-tumor activity of the chemotherapeutic agent co-delivered to a level that cannot be achieved by inhibiting a MDR single way.

Piperlongumine Inhibits Akt Phosphorylation to Reverse Resistance to Cisplatin in Human Non-Small Cell Lung Cancer Cells via ROS Regulation

Resistance is a major concern when administering chemotherapy to patients with non-small cell lung cancer (NSCLC). Chemosensitizer are agents that can reverse resistance to chemotherapeutic drugs, thereby enhancing the chemosensitivity of tumor cells. Thus, their development will improve therapeutic efficacy in cancer. However, few effective chemosensitizer have been identified to date. Piperlongumine (PL) has been shown to effectively reverse resistance to chemotherapeutic drugs in several types of cancers. However, the mechanisms associated with the chemotherapy resistance reversal effect of PL and its regulation of target factors in chemotherapy resistance cells are still unclear. This study investigated the reversal effect of PL both in vitro and in vivo, and provided evidence that PL inhibited the phosphorylation of Akt via the accumulation of reactive oxygen species in chemotherapy resistance cells. Consequently, various Akt activation-dependent genes caused a reduction of drug efflux and induction of apoptosis in cisplatin-resistant A549 NSCLC cells. Our results indicate that Akt phosphorylation may play a functional role in the reversal effect of PL and contribute, at least in part, to the treatment outcomes of patients with chemotherapy resistance.

Spica Prunellae Extract Enhances Fluorouracil Sensitivity of 5-Fluorouracil-Resistant Human Colon Carcinoma HCT-8/5-FU Cells via TOP2α and miR-494

The use of 5-fluorouracil (5-FU) has been proven benefits, but it also has adverse events in colorectal cancer (CRC) chemotherapy. In this study, we explored the mechanism of 5-FU resistance by bioinformatics analysis of the NCBI public dataset series GSE81005. Fifteen hub genes were screened out of 582 different expressed genes. Modules of the hub genes in protein-protein interaction networks gathered to TOP2α showed a decrease in HCT-8 cells but an increase in 5-FU-resistant HCT-8/5-FU cells with 5-FU exposure. Downregulation of TOP2α with siRNA or miR-494 transfection resulted in an increase of cytotoxicity and decrease of cell colonies to 5-FU for HCT-8/5-FU cells. Moreover, we found that an ethanol extract of Spica Prunellae (EESP), which is a traditional Chinese medicine with clinically beneficial effects in various cancers, was able to enhance the sensitivity of 5-FU in HCT-8/5-FU cells and partly reverse the 5-FU resistance effect. It significantly helped suppress cell growth and induced cell apoptosis in HCT-8/5-FU cells with the expression of TOP2α being significantly suppressed, which increased by 5-FU. Consistently, miR-494, which reportedly regulates TOP2α, exhibited reverse trends in EESP/5-FU combination treatment. These results suggested that Spica Prunellae may be beneficial in the treatment of 5-FU-resistant CRC patients.

Carrier-Free Supramolecular Hydrogel Composed of Dual Drugs for Conquering Drug Resistance

The resistance of tumor cells to anticancer drugs has become one of the principal causes of the failure in clinical chemotherapy. To overcome this issue, developing feasible drug delivery systems for effective cancer therapy is urgently needed. In this work, we construct an amphiphilic drug self-delivery system consisting of Taxol and tyroservatide (YSV) to overcome drug resistance. The carrier-free supramolecular hydrogel composed of nanofibers is formed by the involved ester bond self-hydrolysis process, which has high drug loading efficiency and facilitates the delivery of both the hydrophobic Taxol and hydrophilic YSV. Because of the dual inhibitory function of YSV on histone deacetylase and P-glycoprotein, an improved combinational anticancer effect of the molecule against drug-resistant tumor cells in vitro is achieved. Furthermore, the designed drug self-delivery system exhibited enhanced antitumor efficiency and favorable biocompatibility in vivo when administered by tail vein injection. Our study provides a new strategy for fabricating a carrier-free supramolecular hydrogel to overcome drug resistance, which might open up an alternative avenue for the tumor combinational therapy.

Natural products as multidrug resistance modulators in cancer

Cancer is a prominent cause of death globally. Currently, many drugs that are in clinical practice are having a high prevalence of side effect and multidrug resistance. Risk of tumors acquiring resistance to chemotherapy (multidrug resistance) remains a significant hurdle to the successful treatment of various types of cancer. Membrane-embedded drug transporters, generally overexpressed in cancer, are the leading cause among multiple mechanisms of multidrug resistance (MDR). P-glycoprotein (P-gp) also MDR1/ABCB1, multidrug resistance associated protein 1 (MRP1/ABCC1), MRP2 and breast cancer resistance protein (BCRP/ABCG2) are considered to be a prime factor for induction of MDR. To date, several chemical substances have been tested in a number of clinical trials for their MDR modulatory activity which are not having devoid of any side effects that necessitates to find newer and safer way to tackle the current problem of multidrug resistance in cancer. The present study systematically discusses the various classes of natural products i.e flavonoids, alkaloids, terpenoids, coumarins (from plants, marine, and microorganisms) as potential MDR modulators and/or as a source of promising lead compounds. Recently a bisbenzyl isoquinoline alkaloid namely tetrandrine, isolated from Chinese herb Stephania tetrandra (Han-Fang-Chi) is in clinical trials for its MDR reversal activity.

Supramolecular Hydrogel Based on Chlorambucil and Peptide Drug for Cancer Combination Therapy

Supramolecular hydrogels of self-assembling peptide-drug conjugates have been considered as effective self-delivery drug systems for cancer therapy in recent years. Here, a novel self-assembling peptide-based supramolecular hydrogel was developed by simultaneously conjugating small-molecule drug chlorambucil (CRB) and peptide drug tyroservatide (YSV) to the self-assembling peptide. The resulting hydrogel with a nanofiber structure showed enhanced stability against proteinase K degradation and an improved cellular uptake performance in comparison with the free molecules. As a consequence, it exhibited enhanced antitumor efficiency both in vitro and in vivo with favorable biocompatibility. This biocompatible self-delivery drug system could not only significantly improve the delivery efficiency of the small-molecule drugs but also adequately synergize the antitumor effect of CRB and YSV, inspiring the design of new strategies of cancer combination therapy.

Reversal effect of quercetin on multidrug resistance via FZD7/β-catenin pathway in hepatocellular carcinoma cells

BACKGROUND

Chemotherapy has been widely used to treat cancer, but the appearance of multidrug resistance (MDR) is the biggest obstacle to successful chemotherapy. One of the conventional mechanisms of MDR is overexpression of ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp/ABCB1) and multidrug resistance-associated proteins (MRPs/ABCCs) that limits the prolonged and efficient use of chemotherapeutic drugs. To enhance the chemosensitivity of tumor cells, attentions have been focused on effective MDR modulators.

PURPOSE

This study aimed to investigate the reversal effect of quercetin on MDR, and explored its mechanism of action in vitro.

STUDY DESIGN/METHODS

The effect and mechanism of quercetin on MDR was examined by using MTT assay, flow cytometry, real-time PCR and western blot analysis in human hepatocellular carcinoma cells.

RESULTS

Our data found that the intracellular accumulation of rhodamine-123 (Rh123) and doxorubicin (ADR) were increased, the sensitivity of BEL/5-FU cells to chemotherapeutic drugs were increased, and the expressions of ABCB1, ABCC1 and ABCC2 were all down-regulated, which indicated that the functions and expressions of ABCB1, ABCC1 and ABCC2 efflux pump were inhibited by quercetin treatment. Moreover, the suppression of ABCB1, ABCC1 and ABCC2 by quercetin was dependent on the FZD7 through the Wnt/β-catenin pathway. Further research revealed that reduction of FZD7 by RNA interference (siFZD7) enhanced the sensitivity to chemotherapeutic drugs, increased the cellular accumulation of Rh123 and ADR, and induced inhibitory effects on the expression of FZD7, ABCB1, ABCC1, ABCC2 and β-catenin, similar to quercetin. In the meanwhile, overexpression of FZD7 showed the inversely effect on the expressions. Interesting, it was confirmed that quercetin could inhibit the expression levels of FZD7, ABCB1, ABCC1, ABCC2 and β-catenin in BEL-7402 cells; furthermore, treatment by quercetin combined with siFZD7 in BEL/5-FU cells, the expressions of these genes were effectively decreased in comparison to quercetin combined with siRNA negative control (sncRNA).

CONCLUSION

Overall, these data suggested the effectiveness of using quercetin, at least in part, via inhibiting FZD7 to combat chemoresistance and showed that quercetin could be developed into an efficient natural sensitizer for resistant human hepatocellular carcinoma.

USP22 knockdown enhanced chemosensitivity of hepatocellular carcinoma cells to 5-Fu by up-regulation of Smad4 and suppression of Akt

USP22, a member of the deubiquitinases (DUBs) family, is known to be a key subunit of the human Spt-Ada-Gcn5 acetyltransferase (hSAGA) transcriptional cofactor complex. Within hSAGA, USP22 removes ubiquitin from histone proteins, thus regulating the transcription and expression of downstream genes. USP22 plays important roles in many cancers; however, its effect and the mechanism underlying HCC chemoresistance remain unclear. In the present study, we found that USP22 was highly expressed in chemoresistant HCC tissues and cells and was correlated with the prognosis of HCC patients who received chemotherapy. Silencing USP22 in chemoresistant HCC Bel/Fu cells dramatically inhibited proliferation, migration, invasion and epithelial-mesenchymal transition in vitro; suppressed tumorigenic and metastatic capacities in vivo; and inhibited drug resistance-related proteins (MDR1, LRP, MRP1). Mechanistically, we found that USP22 knockdown exerts its function through down-regulating PI3K and activating Smad4, which inhibited phosphorylation of Akt. Silencing Smad4 blocked USP22 knockdown-induced Akt inhibition in Bel/Fu cells. Our results, for the first time, provide evidence that USP22 plays a critical role in the development of chemoresistant HCC cells and that high USP22 expression serves as a molecular marker for the prognosis of HCC patients who undergo chemotherapy.

Influence of c-Src on hypoxic resistance to paclitaxel in human ovarian cancer cells and reversal of FV-429

SRC family kinase was documented to have vital roles in adjusting cancer cell malignant behaviors. To date, the role of c-Src, a member of SRC family kinase, in resistance to paclitaxel in human ovarian cancer cells under hypoxia has not been investigated. In the present study, we discovered that hypoxic environment suppressed paclitaxel-induced G2/M phase arrest and blockade of c-Src improved ovarian cancer cells’ sensitivity to paclitaxel. FV-429, a derivative of natural flavonoid wogonin, could suppress gene expression and activation of c-Src, followed by deteriorated Stat3 nuclear translocation and its binding to HIF-1α, resulting in paclitaxel resistance reversal through G2/M arrest potentiation. Our study demonstrated that c-Src contributed to hypoxic microenvironment-rendered paclitaxel resistance in human epithelial ovarian cancer cells by G2/M phase arrest deterioration, and through c-Src suppression, FV-429 was capable of reversing the resistance by blocking c-Src/Stat3/HIF-1α pathway.

Natural alkaloids as P-gp inhibitors for multidrug resistance reversal in cancer

The biggest challenge associated with cancer chemotherapy is the development of cross multi-drug resistance to almost all anti-cancer agents upon chronic treatment. The major contributing factor for this resistance is efflux of the drugs by the p-glycoprotein pump. Over the years, inhibitors of this pump have been discovered to administer them in combination with chemotherapeutic agents. The clinical failure of first and second generation P-gp inhibitors (such as verapamil and cyclosporine analogs) has led to the discovery of third generation potent P-gp inhibitors (tariquidar, zosuquidar, laniquidar). Most of these inhibitors are nitrogenous compounds and recently a natural alkaloid CBT-01^® (tetrandrine) has advanced to the clinical phase. CBT-01 demonstrated positive results in Phase-I study in combination with paclitaxel, which warranted conducting it's Phase II/III trial. Apart from this, there exist a large number of natural alkaloids possessing potent inhibition of P-gp efflux pump and other related pumps responsible for the development of resistance. Despite the extensive contribution of alkaloids in this area, has never been reviewed. The present review provides a comprehensive account on natural alkaloids possessing P-gp inhibition activity and their potential for multidrug resistance reversal in cancer.

Inside the biochemical pathways of thymidylate synthase perturbed by anticancer drugs: Novel strategies to overcome cancer chemoresistance

Our current understanding of the mechanisms of action of antitumor agents and the precise mechanisms underlying drug resistance is that these two processes are directly linked. Moreover, it is often possible to delineate chemoresistance mechanisms based on the specific mechanism of action of a given anticancer drug. A more holistic approach to the chemoresistance problem suggests that entire metabolic pathways, rather than single enzyme targets may better explain and educate us about the complexity of the cellular responses upon cytotoxic drug administration. Drugs, which target thymidylate synthase and folate-dependent enzymes, represent an important therapeutic arm in the treatment of various human malignancies. However, prolonged patient treatment often provokes drug resistance phenomena that render the chemotherapeutic treatment highly ineffective. Hence, strategies to overcome drug resistance are primarily designed to achieve either enhanced intracellular drug accumulation, to avoid the upregulation of folate-dependent enzymes, and to circumvent the impairment of DNA repair enzymes which are also responsible for cross-resistance to various anticancer drugs. The current clinical practice based on drug combination therapeutic regimens represents the most effective approach to counteract drug resistance. In the current paper, we review the molecular aspects of the activity of TS-targeting drugs and describe how such mechanisms are related to the emergence of clinical drug resistance. We also discuss the current possibilities to overcome drug resistance by using a molecular mechanistic approach based on medicinal chemistry methods focusing on rational structural modifications of novel antitumor agents. This paper also focuses on the importance of the modulation of metabolic pathways upon drug administration, their analysis and the assessment of their putative roles in the networks involved using a meta-analysis approach. The present review describes the main pathways that are modulated by TS-targeting anticancer drugs starting from the description of the normal functioning of the folate metabolic pathway, through the protein modulation occurring upon drug delivery to cultured tumor cells as well as cancer patients, finally describing how the pathways are modulated by drug resistance development. The data collected are then analyzed using network/netwire connecting methods in order to provide a wider view of the pathways involved and of the importance of such information in identifying additional proteins that could serve as novel druggable targets for efficacious cancer therapy.

The overexpression and nuclear translocation of Trx-1 during hypoxia confers on HepG2 cells resistance to DDP, and GL-V9 reverses the resistance by suppressing the Trx-1/Ref-1 axis

Microenvironmental hypoxia gives many tumor cells the capacity for drug resistance. Thioredoxin family members play critical roles in the regulation of cellular redox homeostasis in a stressed environment. In this study, we established a hypoxia-drug resistance (hypoxia-DR) model using HepG2 cells and discovered that the overexpression and nuclear translocation of thioredoxin-1 (Trx-1) are closely associated with this resistance through the regulation of the metabolism by the oxidative stress response to glycolysis. Intranuclear Trx-1 enhances the DNA-binding activity of HIF-1α via its interaction with and reducing action on Ref-1, resulting in increased expression of glycolysis-related proteins (PDHK1, HKII, and LDHA), glucose uptake, and lactate generation under hypoxia. Meanwhile, we found that GL-V9, a newly synthesized flavonoid derivative, shows an ability to reverse the hypoxia-DR and has low toxicity both in vivo and in vitro. GL-V9 could inhibit the expression and nuclear translocation of Trx-1 and then suppress HIF-1α DNA-binding activity by inhibiting the Trx-1/Ref-1 axis. As a result, glycolysis is weakened and oxidative phosphorylation is enhanced. Thus, GL-V9 leads to an increment in intracellular ROS generation and consequently intensified apoptosis induced by DDP.

Doxorubicin and curcumin co-delivery by lipid nanoparticles for enhanced treatment of diethylnitrosamine-induced hepatocellular carcinoma in mice

At present, the treatment of hepatocellular carcinoma (HCC) is an international problem. The delivery of a chemotherapeutic agent and chemosensitizer using nanocarriers has been suggested as a novel and promising strategy in cancer treatment. However, such studies in HCC remain very limited. In this study, we developed doxorubicin (DOX) and curcumin (Cur) co-delivery lipid nanoparticles (DOX/Cur-NPs) and examined its inhibitory effect on diethylnitrosamine (DEN)-induced HCC in mice. DOX/Cur-NPs displayed the physicochemical characterizations with uniform particle size, high encapsulation efficacy and sustained release profile. In DNE-induced HCC mice treated with DOX/Cur-NPs, we observed decreased liver damage assessed by serum ALT and AST levels, liver/body weight ratio, and histopathological analysis. Compared with DOX-loaded nanoparticles (DOX-NPs), DOX/Cur-NPs induced increased Caspase-3 and Bax/Bcl-2 ratio, and decreased C-myc, PCNA and VEGF. The results revealed the synergistic effect of DOX/Cur-NPs on the apoptosis, proliferation and angiogenesis of HCC. The mRNA levels of MDR1, bcl-2 and HIF-1α, and protein levels of P-gp, Bcl-2 and HIF-1α were decreased in DOX/Cur-NPs than those in DOX-NPs, indicating that Cur might reverse multidrug resistance (MDR) through these pathways. In HCC cells, enhanced cytotoxicity and decreased IC50 and resistant index further confirmed the synergistic effects of DOX/Cur-NPs than DOX-NPs. Our studies suggest that simultaneous delivery of DOX and Cur by DOX/Cur-NPs may be a promising treatment for HCC.

Reversal of multidrug resistance in gastric cancer cells by E2F-1 downregulation in vitro and in vivo

Transcription Factor E2F-1 plays a critical role in cell cycle regulation and other biological processes in cells. However whether or not it is involved in the multi-drug resistance (MDR) process of gastric cancer has not been fully elucidated yet. To explore the role of E2F-1 in the MDR process of gastric cancer in vitro and in vivo, a cisplatin-resistant gastric cancer cell line with stable downregulation of E2F-1 was established. E2F-1 shRNA led to downregulation of endogenous E2F-1 mRNA and protein. It significantly promoted the sensitivity of SGC7901/DDP cells to cisplatin, doxorubicin, and fluorouracil. Flow cytometry confirmed that the percentage of apoptotic cells increased after E2F-1 downregulation. This notion was further supported by the observation that downregulation of E2F-1 blocked entry into the S-phase of the cell cycle. Furthermore, downregulation of E2F-1 significantly increased intracellular accumulation of doxorubicin. In addition, we determined the in vivo effects of E2F-1 small interfering RNA (shRNA) on tumor size, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining. In molecular studies, semiquantitative RT-PCR and western blotting revealed that E2F-1 downregulation could inhibit expression of MDR1, MRP, Bcl-2/Bax, c-Myc, Skp2, Survivin, and Cyclin D1.

IN CONCLUSION

E2F-1 may be involved in regulating multiple signaling pathways in reversing MDR, suggesting that E2F-1 may represent a novel target for gastric cancer therapy.

CXCL12/CXCR4 axis confers adriamycin resistance to human chronic myelogenous leukemia and oroxylin A improves the sensitivity of K562/ADM cells

This study was aimed at investigating the reversal effect of oroxylin A, a naturally bioactive monoflavonoid separated and purified from Scutellaria baicalensis Georgi, in human chronic myeloid leukemia (CML) and the underlying mechanisms. The results showed that CXCL12 could enhance the resistance of K562 cells to adriamycin (ADM) by increasing the expression of CXCR4, up-regulating the downstream PI3K/Akt pathway, and promoting translocation of NF-κB dimers into nucleus and subsequently decreasing the expression of apoptosis-related proteins in K562 cells. And we found that ADM resistance was partially reversed by CXCR4 siRNA transfection. Moreover, the sensitivity enhancement of oroxylin A was demonstrated by decreasing the expression of CXCR4 at both protein and mRNA levels, via PI3K/Akt/NF-κB pathway and triggering the apoptosis pathway in vitro. In addition, the in vivo study showed that oroxylin A increased apoptosis of leukemic cells with low systemic toxicity, and the mechanism was the same as in vitro study. In conclusion, all these results showed that oroxylin A improved the sensitivity of K562/ADM cells by increasing apoptosis in leukemic cells and decreasing the expression of CXCR4 and PI3K/Akt/NF-κB pathway, and probably served as a most promising agent for CML treatment.

A hydrogel-based tumor model for the evaluation of nanoparticle-based cancer therapeutics

Three-dimensional (3D) tissue-engineered tumor models have the potential to bridge the gap between monolayer cultures and patient-derived xenografts for the testing of nanoparticle (NP)-based cancer therapeutics. In this study, a hydrogel-derived prostate cancer (PCa) model was developed for the in vitro evaluation of doxorubicin (Dox)-loaded polymer NPs (Dox-NPs). The hydrogels were synthesized using chemically modified hyaluronic acid (HA) carrying acrylate groups (HA-AC) or reactive thiols (HA-SH). The crosslinked hydrogel networks exhibited an estimated pore size of 70-100 nm, similar to the spacing of the extracellular matrices (ECM) surrounding tumor tissues. LNCaP PCa cells entrapped in the HA matrices formed distinct tumor-like multicellular aggregates with an average diameter of 50 μm after 7 days of culture. Compared to cells grown on two-dimensional (2D) tissue culture plates, cells from the engineered tumoroids expressed significantly higher levels of multidrug resistance (MDR) proteins, including multidrug resistance protein 1 (MRP1) and lung resistance-related protein (LRP), both at the mRNA and the protein levels. Separately, Dox-NPs with an average diameter of 54 ± 1 nm were prepared from amphiphilic block copolymers based on poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) bearing pendant cyclic ketals. Dox-NPs were able to diffuse through the hydrogel matrices, penetrate into the tumoroid and be internalized by LNCaP PCa cells through caveolae-mediated endocytosis and macropinocytosis pathways. Compared to 2D cultures, LNCaP PCa cells cultured as multicellular aggregates in HA hydrogel were more resistant to Dox and Dox-NPs treatments. Moreover, the NP-based Dox formulation could bypass the drug efflux function of MRP1, thereby partially reversing the resistance to free Dox in 3D cultures. Overall, the engineered tumor model has the potential to provide predictable results on the efficacy of NP-based cancer therapeutics.

DLJ14, a novel chemo-sensitization agent, enhances therapeutic effects of adriamycin against MCF-7/A cells both in vitro and in vivo

OBJECTIVES

We investigated the chemo-sensitization of a ligustrazine derivate, (E)-2-(2, 4-dimethoxystyryl)-3, 5, 6-trimethylpyrazine (DLJ14) on Adriamycin (Adr, Wanle, Shenzhen, China)-resistant human breast cancer (MCF-7/A) cells both in vivo and in vitro.

METHODS

The antitumour effects of DLJ14 and Adr was observed in MCF-7/A cells by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay in vitro and was evaluated by MCF-7/A xenografts in nude mice. The intracellular Adr accumulation was assessed by mean fluorescence intensity of Adr. The messenger RNA level of glutathione (GSH) S-transferase (GST)π in MCF-7/A cells was determined by real-time reverse transcription PCR assay. The expression of GSTπ, c-jun NH2 -terminal kinase (JNK) and phosphor-JNK (p-JNK) was detected by Western blotting method.

KEY FINDINGS

The MTT results showed that DLJ14 exhibited a weak inhibition on proliferation of both MCF-7 and MCF-7/A cells, in contrast with the strong inhibition of verapamil. When DLJ14 is combined with Adr, the inhibitory effect on MCF-7/A cells and MCF-7/A xenografts was enhanced significantly through increasing intracellular accumulation of Adr by inhibition of GSH level and the activity of GSH peroxidase and GST. Moreover, DLJ14 could downregulate the expression of GSTπ and increase the expression of JNK and p-JNK in MCF-7/A cells or in xenografts.

CONCLUSION

DLJ14 is a promising chemo-sensitization candidate for the reversal of multidrug resistance in cancers.

Reversal effect of bufalin on multidrug resistance in human hepatocellular carcinoma BEL-7402/5-FU cells

Multidrug resistance (MDR) is a major obstacle to chemotherapy in patients with hepatocellular carcinoma (HCC). To overcome MDR and improve chemotherapeutic efficacy, novel reversal agents with higher efficacy and lower toxicity are urgently needed for HCC. The present study was designed to examine the potential reversal activity of bufalin, a toxic ligand isolated from the traditional Chinese medicine 'Chansu' and to elucidate the possible related mechanisms. A multidrug-resistant HCC cell line, BEL-7402/5-FU, was used as the cell model. The working concentration of bufalin as an effective reversal agent, and the cell viability in the reversal experiments were determined by MTT assay. The effects of bufalin at a non-cytotoxic dose on cell cycle distribution, apoptosis and drug efflux pump activity were measured by flow cytometry. Qualitative observation of apoptosis was also carried out by confocal microscopy. Furthermore, the effects of bufalin on the expression of potential genes involved in MDR of BEL-7402/5-FU cells, including thymidylate synthase (TS), P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), B-cell lymphoma-extra large (Bcl-xL) and Bcl-2-associated X protein (Bax), were determined using real-time PCR and western blot analysis. The results showed that bufalin at a concentration of 1 nM enhanced the chemosensitivity of BEL-7402/5-FU cells to 5-FU with a reversal fold of 3.8 which was similar to that of 1 µM verapamil. Bufalin significantly arrested the cell cycle at the G₀/G₁ phase, induced apoptosis through an increase in the Bax/Bcl-xL ratio, inhibited drug efflux pump activity via downregulation of MRP1, and reduced the expression of TS in BEL-7402/5-FU cells. The present study revealed that bufalin effectively reversed MDR in BEL-7402/5-FU cells through multiple pathways. The combination of bufalin with cytotoxic drugs may serve as a promising strategy for the chemotherapy of HCC.

Reversal effects of Rabdosia rubescens extract on multidrug resistance of MCF-7/Adr cells in vitro

CONTEXT

Rabdosia rubescens (Hemsl.) Hara (Lamiaceae) is widely used in traditional Chinese medicines for the treatment of antitumor, antimicrobial, anti-inflammatory and antioxidation. It is also used as a supplement in the treatment of many cancers, such as esophagus, mammary gland, liver and prostate cancers.

OBJECTIVE

To investigate the multidrug resistance (MDR) reversal effects and its possible mechanism of R. rubescens extracts on human breast cancer cell line MCF-7/Adr (Michigan Cancer Foundation--7/adriamycin resistance).

MATERIALS AND METHODS

Rabdosia rubescens were extracted by reflux extraction method with different solvent such as petroleum ether, chloroform, ethyl acetate, n-butyl alcohol and water in order and obtain petroleum ether fraction (PEF), chloroform fraction (CF), ethyl acetate fraction (EAF), n-butyl alcohol fraction (BAF) and aqueous fraction (AF). The active extract fractions of R. rubescens were screened by rhodamine123 (Rh123) accumulation assay. Cytotoxicity of the effect fraction was examined by the MTT assay; the intracellular accumulation of adriamycin and expression of P-gp were examined by flow cytometry; the gene transcription of MDR1 was determined by RT-PCR.

RESULTS

CF and EAF fractions could increase the intracellular accumulation of adriamycin in MCF-7/Adr cells, PEF, BAF and AF fractions showed little effect on the intracellular accumulation of adriamycin or Rh123. When adriamycin was used in combination with CF and EAF fractions at non-toxic concentration on MCF-7/Adr cells, CF and EAF fractions can reverse MDR of MCF-7/Adr cells, and the reverse folds were 2.16 (CF, 4 μg/mL), 4.60 (CF, 20 μg/mL), 1.87 (EAF, 4 μg/mL) and 4.02 (EAF, 20 μg/mL), respectively. After treatment with CF (4.20 μg/mL) and EAF (4.20 μg/mL) for 48 h, the MDR1 gene expression level in MCF-7/Adr cells was decreased by 40.17, 48.14, 33.86 and 42.52%, and the abundance of P-gp also decreased by 8.63, 24.53, 27.50 and 34.91% in MCF-7/Adr cells, respectively.

DISCUSSION AND CONCLUSION

These results indicate the therapeutic value of chloroform fraction (CF) and ethyl acetate fraction (EAF) from R. rubescens as potential MDR reversing agents and warranted further investigation.

The noncytotoxic dose of sorafenib sensitizes Bel-7402/5-FU cells to 5-FU by down-regulating 5-FU-induced Nrf2 expression

BACKGROUND

Acquired resistance to 5-fluorouracil (5-FU) is a serious therapeutic obstacle in advanced hepatocellular carcinoma (HCC) patients.

AIM

To investigate whether nuclear factor erythroid 2-related factor 2 (Nrf2) was associated with drug resistance in 5-FU resistant Bel-7402 (Bel-7402/5-FU) cells, and if sorafenib, an oral multikinase inhibitor targeting the tumor and vasculature, could reverse drug resistance in Bel-7402/5-FU cells at the noncytotoxic dosage.

METHODS

We used MTT to detect the resistance reversal activity of sorafenib, compared Nrf2 expression in various conditions by western blot and qRT-PCR, and analyzed subcellular localization of Nrf2 by immunofluorescence.

RESULTS

The endogenous expression of Nrf2 in Bel-7402/5-FU cells was similar to that observed in Bel-7402 cells. However, Nrf2 expression levels were increased by 5-FU treatment in Bel-7402/5-FU cells higher than that in Bel-7402 cells, which is to highlight the Nrf2 contribution to the enhanced resistance of Bel-7402/5-FU cells to 5-FU. Moreover, intracellular Nrf2 protein level was significantly down-regulated by Nrf2-shRNA in Bel-7402/5-FU cells, resulting in partial reversal of 5-FU resistance. Sorafenib down-regulated the increased expression of Nrf2 induced by 5-FU treatment and partly reversed 5-FU resistance in Bel-7402/5-FU cells.

CONCLUSIONS

These results suggested that more sensitive cell defense mediated by Nrf2 was associated with drug resistance of Bel-7402/5-FU cells. Sorafenib reversed drug resistance, and its reversal mechanism might be due to the suppression of Nrf2 expression induced by 5-FU, indicating the feasibility of using Nrf2 inhibitors to increase efficacy of chemotherapeutic drugs in HCC patients.

Effect of curcumin on human colon cancer multidrug resistance in vitro and in vivo

OBJECTIVE

To determine whether curcumin reverses the multidrug resistance of human colon cancer cells in vitro and in vivo.

METHODS

In a vincristine-resistant cell line of human colon cancer, the cell viability of curcumin-treated cells was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Rhodamine123 efflux was evaluated to detect P-glycoprotein transporter activity, and expression of the multidrug resistance protein 1 and survivin genes was analyzed by reverse transcription polymerase chain reaction and western blotting. In addition, xenograft mouse tumors were grown and treated with curcumin. The morphology of the xenografts was investigated by hematoxylin-eosin staining. The in vivo expression of the multidrug resistance gene and P-glycoprotein and survivin genes and proteins was observed using reverse transcription-polymerase chain reaction and western blotting, respectively.

RESULTS

Curcumin was not obviously toxic to the vincristine-resistant human colon cancer cells at concentrations less than 25 μM, but the growth of cells was significantly inhibited. At concentrations greater than 25 μM, curcumin was toxic in a concentration-dependent manner. The sensitivity of cells to vincristine, cisplatin, fluorouracil, and hydroxycamptothecin was enhanced, intracellular Rhodamine123 accumulation was increased (p<0.05), and the expression of the multidrug resistance gene and P-glycoprotein were significantly suppressed (p<0.05). The combination of curcumin and vincristine significantly inhibited xenograft growth. The expression of the multidrug resistance protein 1 and survivin genes was significantly reduced in xenografts of curcumin-treated mice and mice treated with both curcumin and vincristine relative to control mice.

CONCLUSION

Curcumin has strong reversal effects on the multidrug resistance of human colon carcinoma in vitro and in vivo.

Silence of p15 expression by RNAi enhances cisplatin resistance in hepatocellular carcinoma cells

The insensitivity of hepatocellular carcinoma to chemotherapy is associated with alternation in tumor cell cycling. This current study was designed to investigate the impact of p15 silencing on the sensitivity of Human hepatocellular carcinoma HepG2 cells to cisplatin. HepG2/CDDP/1.6 and HepG2/CDDP/2.0 cells were induced by culture with increased doses of cisplatin and their sensitivities to cis-Diamine dichloroplatinum (CDDP) were determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The impacts of p15 silencing on the cell cycling and P-gp expression were characterized by flow cytometry, RT-PCR and Western blot assays, respectively. Knockdown of p15 expression dramatically reduced the relative levels of p15 expression and the frequency of phase G1, promoting cell cycling. On the other hand, knockdown of p15 expression significantly up-regulated the expression of P-glycoprotein (P-gp) in HepG2/CDDP/2.0 cells, associated with the increased resistance of HepG2 cells to CDDP in vitro. In conclusion, the p15 may be a critical regulator of the development of CDDP resistance in HepG2 cells.

Regulation of hepatic ABCC transporters by xenobiotics and in disease states

The subfamily of ABCC transporters consists of 13 members in mammals, including the multidrug resistance-associated proteins (MRPs), sulfonylurea receptors (SURs), and the cystic fibrosis transmembrane conductance regulator (CFTR). These proteins play roles in chemical detoxification, disposition, and normal cell physiology. ABCC transporters are expressed differentially in the liver and are regulated at the transcription and translation level. Their expression and function are also controlled by post-translational modification and membrane-trafficking events. These processes are tightly regulated. Information about alterations in the expression of hepatobiliary ABCC transporters could provide important insights into the pathogenesis of diseases and disposition of xenobiotics. In this review, we describe the regulation of hepatic ABCC transporters in humans and rodents by a variety of xenobiotics, under disease states and in genetically modified animal models deficient in transcription factors, transporters, and cell-signaling molecules.

Riccardin D, a novel macrocyclic bisbibenzyl, induces apoptosis of human leukemia cells by targeting DNA topoisomerase II

We studied the effect of riccardin D, a macrocyclic bisbibenzyl, which was isolated from the Chinese liverwort plant, on human leukemia cells and the underlying molecular mechanism. Riccardin D had a significant antiproliferative effect on human leukemia cell lines HL-60, K562 and its multidrug resistant (MDR) counterpart K562/A02 cells, but showed no effect on the topoisomerase-II-deficient HL-60/MX2 cells, as measured by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. The pBR322 DNA relaxation assay revealed that riccardin D selectively inhibited the activity of topoisomerase II (topo II). The suppression of topo II activity by riccardin D was stronger than that of etoposide, a known topo II inhibitor. After treatment with riccardin D, nuclear extracts of leukemia K562 and K562/A02 cells left the majority of pBR322 DNA in a supercoiled form. Further examination showed that riccardin D effectively induced HL-60, K562 and K562/A02 apoptosis as evidenced by externalization of phosphatidylserine and formation of DNA ladder fragments. The activation of cytochrome c, caspase-9, caspase-3 and cleaved poly ADP-ribose polymerase (PARP) was also enhanced, as estimated by Western blot analysis. By contrast, riccardin D was unable to induce apoptosis in the topoisomerase-II-deficient HL-60/MX2 cells, indicating that the induction of apoptosis by riccardin D was due to the inhibition of topo II activity. In addition, riccardin D was able to significantly decrease P-glycoprotein (P-gp) expression in K562/A02 cells. Taken together, our data demonstrate that riccardin D is a novel DNA topo II inhibitor which can induce apoptosis of human leukemia cells and that it has therapeutic potential for both regular and MDR strains of leukemia cells.

Reversal of P-glycoprotein-mediated multidrug resistance in vitro by milbemycin compounds in adriamycin-resistant human breast carcinoma (MCF-7/adr) cells

The effects of milbemycin A(4) (MB A(4)), milbemycin oxime A(4) (MBO A(4)) and milbemycin beta(1) (MB beta(1)) on reversing multidrug resistance (MDR) of tumor cells were firstly conducted according to the following research, including MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, the accumulation of adriamycin, the accumulation and efflux of rhodamine 123 (Rh123), the regulations of MDR1 gene, and expression of P-gp. The three milbemycins (5muM) showed strong potency to increase adriamycin cytotoxicity toward adriamycin-resistant human breast carcinoma cells MCF-7/adr with reversal fold (RF) of 21.42, 19.06 and 14.89, respectively. In addition, the mechanisms of milbemycins on P-glycoprotein (P-gp)-mediated MDR demonstrated that the milbemycins significantly increased the intracellular accumulations of adriamycin and Rh123 via inhibiting P-gp transport function. Based on the analysis of the P-gp and MDR1 gene expression using flow cytometry and RT-PCR, the results revealed that milbemycin compounds, particularly MB A(4), could regulate down the expression of the P-gp and MDR1 gene. These findings suggest that the milbemycins probably represent promising agents for overcoming MDR in cancer therapy, and especially MB A(4) is better modulator with the lowest toxicity.

Inhibition of oligopeptide transporter suppress growth of human pancreatic cancer cells

Oligopeptide transporters are abundantly expressed in various types of cancer cells. We here synthesized two novel dipeptides, l-phenylalanyl sarcosine (Phe-Sar) and 4-(4-methoxyphenyl)-l-phenylalanyl sarcosine (Bip(OMe)-Sar), and examined their effect on the growth of human pancreatic cancer AsPC-1 cells, which are known to highly express oligopeptide transporter PEPT1/SLC15A1. Growth of AsPC-1 cells was inhibited by these two peptides and a typical PEPT1/SLC15A1 substrate Gly-Sar. Growth inhibition by Gly-Sar, Phe-Sar and Bip(OMe)-Sar was concentration-dependent with half-maximal inhibitory concentration of 50, 0.91 and 0.55mM, respectively. These peptides also inhibited PEPT1-mediated [(3)H]Gly-Sar uptake with half-maximal inhibitory concentration of 2.6, 0.81 and 0.27mM, respectively. Thus, the rank order of the tumor cell growth inhibition by these three peptides was the same as that of PEPT1-inhibitory activity. Growth of AsPC-1 cells was also inhibited by 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH), which is a typical inhibitor of amino acid transporter system L. The growth inhibition by BCH and Gly-Sar was additive, suggesting that these compounds act at distinct loci. Oligopeptide transporters thus appear to be a promising target for inhibition of pancreatic cancer progression. These results also proposed the idea that oligopeptide transporter is required for growth of AsPC-1 cells.

5-Fluorouracil: mechanisms of resistance and reversal strategies

The purpose of this work is to review the published studies on the mechanisms of action and resistance of 5-fluorouracil. The review is divided into three main sections: mechanisms of anti-tumor action, studies of the resistance to the drug, and procedures for the identification of new genes involved in resistance with microarray techniques. The details of the induction and reversal of the drug resistance are also described.