Xian-Jun Qu

High expression of α 2, 3-linked sialic acid residues is associated with the metastatic potential of human gastric cancer.

BACKGROUND Sialic acid, as a terminal saccharide residue on cell surface glycoconjugates, plays an important role in a variety of biological processes. However, the precise nature of the molecules in gastric cancers has not been unveiled nor documented to be of clinical relevance. Herein, we measured the expression of alpha 2, 3-linked sialic acid residues by using a specific lectin as well as the potential of invasion and metastasis of gastric cancer was analyzed. METHODS The expression of alpha 2, 3-linked sialic acid residues in 100 cases of gastric cancer samples was evaluated using Maackia amurensis leukoagglutinin (MAL) histochemical staining analysis. The assays of cytochemical staining and flow cytometry were employed to determine the MAL positive cells in the gastric cancer cell lines. The activities of invasion and migration were evaluated using the assays of cell adhesion and transwell chamber. RESULTS The staining of MAL in gastric cancer tissues showed that high levels of alpha 2, 3-linked sialic acid residues were closely associated with the invasive depth (P=0.0003) and lymph node metastasis (P=0.0441). In gastric adenocarcinoma cell lines, SGC-7901, the highly metastatic cell line, displayed the most positive reaction with MAL among the selected cell lines. The potential of invasion and migration was confirmed using the assays of adhesion and transwell chamber that SGC-7901 exhibited the high activity of adhesion to extracellular matrix (ECM) and penetration to Matrigel. CONCLUSION These results suggested that high level of alpha 2, 3-linked sialic acid residues was associated with metastatic potential of gastric cancer cells.

Reversal effect of a macrocyclic bisbibenzyl plagiochin E on multidrug resistance in adriamycin-resistant K562/A02 cells

Plagiochin E is a new macrocyclic bisbibenzyl compound isolated from Marchantia polymorpha. In the previous studies, we reported that when combined with fluconazole, plagiochin E had synergetic effects against the resistant strain of Candida albicans. Herein, we examined the reversal effect of plagiochin E on multidrug resistance in adriamycin-induced resistant K562/A02 cells and the parental K562 cells. Its cytotoxicity and reversal effects on multidrug resistance were assessed by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide) assay. Apoptosis percentage of cells was obtained from Annexin V/fluorescein isothiocyanate (FITC) and propridium iodide (PI) double-staining. The effects of plagiochin E on P-glycoprotein activity were evaluated by measuring rhodamine 123 (Rh123)-associated mean fluorescence intensity and P-glycoprotein expression on the basis of the flow cytometric technology, respectively. The results showed that plagiochin E ranging from 2 to 12 mug/ml had little cytotoxicity against K562/A02 cells. When combined with adriamycin, it significantly promoted the sensitivity of K562/A02 cells toward adriamycin through increasing intracellular accumulation of adriamycin in a dose-dependent manner. Further study demonstrated that the inhibitory effect of plagiochin E on P-glycoprotein activity was the major cause of increased stagnation of adriamycin inside K562/A02 cells, indicating that plagiochin E, as a new class of mutidrug resistance inhibitor, may effectively reverse the multidrug resistance in K562/A02 cells via inhibiting expression and drug-transport function of P-glycoprotein.

Protective effects of Salvia plebeia compound homoplantaginin on hepatocyte injury.

Salvia plebeia R. Br is a traditional Chinese herb which has been considered as an inflammatory mediator used for treatment of many infectious diseases including hepatitis. Previously, the compound homoplantaginin was isolated in our group. Hence, we evaluated the protective effects of homoplantaginin on hepatocyte injury. Homoplantaginin displayed an antioxidant property in a cell-free system and showed IC(50) of reduction level of DPPH radical at 0.35 microg/ml. In human hepatocyte HL-7702 cells exposed to H(2)O(2), the addition of 0.1-100 microg/ml of homoplantaginin, which did not have a toxic effect on cell viability, significantly reduced lactate dehydrogenase (LDH) leakage, and increased glutathione (GSH), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in supernatant. In vivo assay, we employed the model of Bacillus Calmette-Guérin (BCG)/lipopolysaccharide (LPS)-induced hepatic injury mice to evaluate efficacy of homoplantaginin. Homoplantaginin (25-100mg/kg) significantly reduced the increase in serum alanine aminotranseferase (ALT) and aspartate aminotransferase (AST), decreased the levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1). The same treatment also reduced the content of thiobarbituric acid-reactive substances (TBARS), elevated the levels of GSH, GSH-Px and SOD in hepatic homogenate. The histopathological analysis showed that the grade of liver injury was ameliorated with reduction of inflammatory cells and necrosis of liver cells in homoplantaginin treatment mice. These results suggest that homoplantaginin has a protective and therapeutic effect on hepatocyte injury, which might be associated with its antioxidant properties.

Strategies to overcome or circumvent P-glycoprotein mediated multidrug resistance.

Cancer patients who receive chemotherapy often experience intrinsic or acquired resistance to a broad spectrum of chemotherapeutic agents. The phenomenon, termed multidrug resistance (MDR), is often associated with the over-expression of P-glycoprotein, a transmembrane protein pump, which can enhance efflux of a various chemicals structurally unrelated at the expense of ATP depletion, resulting in decrease of the intracellular cytotoxic drug accumulation. The MDR has been a big threaten to the human health and the war fight for it continues. Although several other mechanisms for MDR are elucidated in recent years, considerable efforts attempting to inverse MDR are involved in exploring P-glycoprotein modulators and suppressing P-glycoprotein expression. In this review, we will report on the recent advances in various strategies for overcoming or circumventing MDR mediated by P-glycoprotein.

Marchantin C, a novel microtubule inhibitor from liverwort with anti-tumor activity both in vivo and in vitro.

Microtubules are long-standing targets in cancer chemotherapy. Previously, we reported that marchantin C triggers apoptosis of human tumor cells. We show here that marchantin C induced cell cycle arrest at G(2)/M phase in A172 and HeLa cells. In addition, marchantin C decreased the quantity of microtubules in a time- and dose-dependent manner in these cells. Exposure of purified bovine brain tubulin to marchantin C inhibited polymerization of gross tubulin in vitro. Moreover, marchantin C potently suppressed the growth of human cervical carcinoma xenografts in nude mice. Marchantin C-treated xenografts showed decreased microtubules, Bcl-2 and increased cyclin B1, Bax, caspase-3, indicating that marchantin C possess the same ability to induce microtubules depolymerization and tumor cell apoptosis in tumor-bearing mice as in vitro. In conclusion, marchantin C is a novel microtubule inhibitor that induces mitotic arrest of tumor cells and suppresses tumor cell growth, exhibiting promising antitumor therapeutic potential.

Marchantin C, a macrocyclic bisbibenzyl, induces apoptosis of human glioma A172 cells

Macrocyclic bisbibenzyls, a class of characteristic components derived from liverworts, are attracting more and more attention because of their wide range of biological significance, including anti-bacterial, anti-fungus, anti-oxidation and cytotoxicity. Herein, we investigated the pro-apoptotic effect of marchantin C on human glioma A 172 cells. The results demonstrated that marchantin C conferred dose-dependent inhibitory effects onto cell growth, viability and colony formation ability of A 172 cells. Morphological observation and DNA laddering assay showed that marchantin C-treated A172 cells displayed outstanding apoptosis characteristics, such as nuclear fragmentation, the appearance of membrane-enclosed apoptotic bodies and DNA laddering fragment. Moreover, flow cytometric detection of phosphatidylserine externalization indicated that marchantin C-induced apoptosis occurred in a dose-dependent manner. RT-PCR and western blot assay further substantiated that marchantin C, as a promising pro-apoptotic agent, had strong effects to induce A172 cell apoptosis, suggesting that the action was achieved through up-regulating Bax and down-regulating Bcl-2.

Des-γ-carboxy prothrombin stimulates human vascular endothelial cell growth and migration

Des-γ-carboxy prothrombin (DCP) is an aberrant prothrombin produced by hepatocellular carcinoma (HCC) cells. Serum and tissue DCP expressions are thought to reflect the biological malignant potential of HCC. However, the role of DCP in the development of angiogenesis is not well understood. Herein, we report the effects of DCP on growth and migration of human vascular endothelial cells. DCP significantly stimulated the proliferation of HUVEC (ECV304) cells in a dose and time dependent manner, as measured by the MTT assay. A continuous rapid migration of ECV304 cells was observed in the presence of DCP measured by the scratch wound assay. The continuous rapid invasive activity, measured by transwell chamber assay also showed that DCP increased endothelial cells migration through the reconstituted extracellular matrix (Matrigel). Further, the tube formation of vascular endothelial cells on 3-D Matrigel showed an increased number of branch points of ECV304 cells induced by DCP in a dose dependent manner. The levels of vascular endothelial cell growth-related angiogenic factors and matrix metalloproteinase were also examined. DCP significantly stimulated the expression levels of epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)-2 (latent and active). Together, these data suggest that DCP is a novel type of vascular endothelial growth factor that possesses potent mitogenic and migrative activities in angiogenesis of HCC.

Recent Advances in P-Glycoprotein-Mediated Multidrug Resistance Reversal Mechanisms

Expression of the multidrug resistance (MDR) phenotype is responsible for chemotherapy failure in numerous cancers. Overexpression of mdr1 gene-encoded permeability glycoprotein (P-gp) is known to play a pivotal role in the development of this phenotype. The role of P-gp has been proposed as an important goal in the design of chemotherapy strategies. However, modulation of P-gp activity by chemotherapy has limited possibilities because of toxicity and poor specificity. In this article, we review the latest advancements in different potential P-gp-mediated MDR reversal mechanisms as well as the methods of evaluating MDR reversal activity, which would be helpful in finding novel MDR reversal agents (or chemosensitizers).

Anti-metastatic and anti-angiogenic activities of sulfated polysaccharide of Sepiella maindroni ink.

A previous study demonstrated that SIP-SII, a sulfated Sepiella maindroni ink polysaccharide, suppressed the invasion and migration of cancer cells via the inhibition of the proteolytic activity of matrix metalloproteinase-2 (MMP-2). Therefore, this study investigated the anti-metastatic effect of SIP-SII in vivo. SIP-SII (15 and 30 mg/kg d) markedly decreased B16F10 pulmonary metastasis in mice models by 85.9% and 88.0%, respectively. Immunohistochemistry showed that SIP-SII decreased the expression of the intercellular adhesion molecule 1 (ICAM-1) and basic fibroblast growth factor (bFGF) in lung metastasis nodules. In addition, SIP-SII inhibited neovascularization in chick chorioallantoic membrane assay at 0.08-2 mg/mL. In the in vitro experiments, SIP-SII (0.8-500 μg/mL) significantly decreased the protein and mRNA expression of ICAM-1 and bFGF in SKOV3 and EA.hy926 cells, respectively. These results suggested that SIP-SII might suppress melanoma metastasis via the inhibition of the tumor adhesion mediated by ICAM-1 and the angiogenesis mediated by bFGF, as well as resulting in depression of the invasion and migration of carcinoma cells.

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

SummaryWe 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.