Jianwen Liu

Reversal of cancer multidrug resistance by green tea polyphenols

The aim of this study was to examine the effect and mechanism of green tea polyphenols (TP) on reversal of multidrug resistance (MDR) in a carcinoma cell line. Using the MTT assay, TP was examined for its modulating effects on the drug‐resistant KB‐A‐1 cells and drug‐sensitive KB‐3–1 cells. When 10 μg mL−1 (‐)‐epigallocatechin gallate (EGCG) or 40 μg mL−1 TP were present simultaneously with doxorubicin (DOX), the IC50 of DOX on KB‐A‐1 cells decreased from 10.3 ± 0.9 μg mL−1 to 4.2 ± 0.2 and 2.0 ± 0.1 μg mL−1, respectively. TP and EGCG enhanced the DOX cytotoxicity on KB‐A‐1 cells by 5.2‐and 2.5‐times, respectively, but did not show a modulating effect on KB‐3–1 cells. This indicated that both TP and EGCG had reversal effects on the MDR phenotype in‐vitro. A KB‐A‐1 cell xenograft model was established, and the effect of TP on reversing MDR in‐vivo was determined. Mechanistic experiments were conducted to examine the uptake, efflux and accumulation of DOX. Cloning and expression of the nucleotide binding domain of the human MDR1 gene in Escherichia coli was established, and by using colorimetry to examine the activity of ATPase to hydrolyse ATP, the ATPase activity of target nucleotide binding domain protein was determined. TP exerted its reversal effects through the inhibition of ATPase activity, influencing the function of P‐glycoprotein, and causing a decreased extrusion of anticancer drug and an increased accumulation of anticancer drug in drug resistant cells. Using reverse transcription‐polymerase chain reaction, the inhibitory effect of TP on MDR1 gene expression was investigated. Down‐regulation of MDR1 gene expression was the main effect, which resulted in the reversal effect of TP on the MDR phenotype. TP is a potent MDR modulator with potential in the treatment of P‐glycoprotein mediated MDR cancers.

In vivo antitumor activity by 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone in a solid human carcinoma xenograft model

Previously, we showed that 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC), isolated from the buds of Cleistocalyx operculatus, significantly inhibited the growth of human liver cancer SMMC-7721xa0cells and could induce SMMC-7721xa0cells apoptosis in vitro. Here, we report the antitumor effects of DMC in vivo, using a solid human tumor xenograft model with a human liver cancer SMMC-7721xa0cell line. Our results revealed that the average tumor weight in a control group and a 150-mg/kg DMC injection group was 1.42±0.11xa0g and 0.59±0.12xa0g, respectively. Flow cytometric analysis of the tumor cell population demonstrated the existence of an aneuploid peak (representing 33.60±0.80% of the total in the 150-mg/kg DMC injection group). To our knowledge, this is the first time that chalcone compounds were applied to a human tumor xenograft model.

Reversal of multidrug resistance in KB cells with tea polyphenol antioxidant capacity

Tea polyphenol (TP), (-)-epigallocatechin gallate (EGCG) in particular, were examined for their reversal effects on multidrug resistance (MDR) with their antioxidant capacities. TP and EGCG were proved to exert reversal effects on drug resistance of KB-A-1 cells by 5.2 and 2.5 times, respectively, but no such effects were found on KB-3-1 cells. With a redox indicator 6 – carboxy - 2’,7’ - dichlorodihydrofluorescein (CDCFH), it could be found that the intracellular reactive oxygen species (ROS) was in a decreasing manner in the KB-3-1 cells, which was induced by defferent concentrations of doxorubicin, whereas the intracellular ROS induced by doxorubicin in KB-A-1 cells maintained at a high level. Such observation suggests that drug resistance cells undergo oxidantive stress. Furthermore, this elevated redox level in KB-A-1 cells is inhibited by either TP or EGCG. Thus, these results demonstrate that the reversal effect of TP and EGCG on MDR through, at least in part, regulating the doxorubicin induced intracellular concentration of ROS.

Quantification of doxorubicin and validation of reversal effect of tea polyphenols on multidrug resistance in human carcinoma cells

HPLC was used to analyze doxorubicin in multidrug-resistance (MDR) human carcinoma cells. This method is novel, simple, sensitive, linear, accurate and precise. The minimal detectable concentration is 0.2xa0μgxa0ml−1. The reversal effects of tea polyphenols on MDR are elucidated by this method. The results indicate that the tea polyphenol, (−)-epigallocatechin gallate, is a potential modulator of MDR.

Refolding and purification of Apo2l/TRAIL produced as inclusion bodies in high-cell-density cultures of recombinant Escherichia coli.

As a new member of tumor necrosis factor (TNF) superfamily, TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) was produced mainly as inclusion bodies by recombinant Escherichia coli with a temperature-inducible expression system. High concentrations of both biomass (65xa0g dry cellsxa0l−1) and inactive TRAIL (4.8xa0gxa0l−1) were obtained by applying a high-cell-density cultivation procedure. After the inclusion bodies were washed and solubilized, TRAIL refolded when at 1xa0mgxa0ml−1 by a simple pulse dilution method with a 35% yield. Renatured TRAIL was purified to electrophoretic homogeneity by one-step immobilized metal affinity chromatography. The purified TRAIL showed strong cytotoxicity activity against human pancreatic 1990 tumor cells, with ED50 about 1.6xa0μgxa0ml−1.

Inhibitive Effect of Prodigiosin on the Proliferation of Human Malignant Pancreatic Cancer Cells

AbstractPancreatic cancer is not only common, but also extremely difficult to treat, for which it has been called the challenge of the twenty-first century. In this study, we find that prodigiosin could effectively inhibit the proliferation of human pancreatic cancer cells H8898 in a dose-and-time-dependent manner, with an IC50 of 75μmol according to the results of MTT and cell proliferation assays. This inhibitive effect may relate to two factors: mitotic arrest and cell death. Results of clone formation and Flow cytometry analysis (FCAS) suggested that prodigiosin has the capability of restraining mitosis by regulating the cell cycle. Prodigiosin also could induce apoptosis of pancreatic cancer cells at low concentration and results in the fragmentation pattern of DNA. Prodigiosin may effectively enter cells and promote the level of intracellular reactive oxygen species (ROSin) in a dose-dependent manner. The generation of ROS may play an important role in the cytotoxic effect. All these results demonstrate that prodigiosin can obviously inhibit the proliferation of pancreatic cancer cells H8898 by arresting the cell cycle and inducing apoptosis. Increased ROS lead this cytotoxic effect.n