Human DNA Topoisomerase I (hTopo I) has been identified to be an efficient target of many effective antitumor drugs. Natural hTopo I is not convenient to be used in screening because of its low concentration in cells. In order to fast screen new anticancer drugs targeting at hTopo I from natural compounds in vitro, hTopo I gene open reading frame (ORF) has been successfully cloned and overexpressed in Pichia pastoris. Total RNA extracted from Hela cells was reversely transcripted to synthesize cDNA with the hTopo I specific antisense primer and the hTopo I ORF was synthesized by PCR. After digestion with EcoR I and Kpn I, the synthesized fragment was inserted into pPICZaA, gave rise to pPICZalpha-hTopoI. After digestion with Sac I, the lined pPICZalpha-hTopoI was transformed into Pichia pastoris strains (KM71, X33 and SMD1168) by electroporation and integrated into their genome. After screened on YPDS plates (containing 1000 ug/mL zeocin), the high-copy recombinant strains (KM-hTopoI, X33-hTopoI and SMD-hTopol) could overexpress recombinant hTopo I, which was fused to the alpha-factor secretion signal and could be secreted into the supernatant in the culture. alpha-factor could be cleaved from the expressed protein during secretion. A higher activity amount of the enzyme was secreted by the particular strain SMD-hTopoI because of its absence of proteimase A than by other strains which possess proteinase A activity. After optimizing the fermentation conditions, a relatively higher enzyme activity in the culture supernatant could be obtained when SMD-hTopoI was induced in BMMY (pH7.25) at 20 degrees C , with addition of 0.5% (V/V) methanol and 3% (V/V) nutrient liquid every 24h. The enzyme activity reached 43 000 u/mL, the yield reached 11 mg/L, achieving approximate 10% of total protein in the culture supernatant. SDS-PAGE and Western blot analyses showed that the mass of the recombinant hTopo I was 91 kD with no glycosylation.
DNA Topoisomerases, Type I ; biosynthesis ; genetics ; Fermentation ; Humans ; Pichia ; genetics ; metabolism ; Recombinant Proteins ; biosynthesis ; genetics

Individualized tailored therapy is a currently pursuing direction for improving the outcome of patients with colorectal cancer. Targeted therapy is the potential strategy to reach this goal by evaluating status of the presumed targets and their related effector molecules and by maximizing the efficacy of chemotherapeutic agents with less toxicity in individual patient. Numerous hurdles should be overcome, however, because therapeutic outcome can be affected by multiple components; tumor characteristics such as somatic mutations at the DNA, RNA, and protein levels; patient characteristics like germline genetic polymorphisms in enzymes linked to drug metabolism; and environmental factors that include diet and physical activity. Currently, large numbers of potential biomarkers have been proposed but have not yet accomplished supporting evidences for their routine usage in clinics. Therefore, clinical trials driven by molecular targets and relevant biomarkers for the understanding of the conflicting data are needed to make markers available in clinical practice.
Colorectal Neoplasms/*drug therapy/radiotherapy ; Combined Modality Therapy ; CpG Islands/genetics ; DNA Topoisomerases, Type I/genetics ; Humans ; Receptor, Epidermal Growth Factor/genetics ; Thymidylate Synthase/genetics ; Tumor Markers, Biological/*genetics

OBJECTIVETo investigate the effect of topotecan (TPT) on human myelodysplastic syndrome (MDS) cells in vitro and in vivo.

METHODSCell growth was measured by a MTT assay. The percentage of cells undergoing apoptosis was determined by flow cytometry after staining with annexin V-FITC and propidium iodide. The morphology of apoptotic cells was observed by transmission electron microscopy (TEM). Furthermore, the antitumor effect on MDS cells in xenotransplanted severe combined immunodeficiency (SCID) mice was evaluated by tumor volume and survival. Western blot was used for determining the expression of topoisomerase I (Top1) protein.

RESULTThe growth of Mutz-1 cells was suppressed by TPT treatment in a dose-dependent manner. The 50% inhibition in Mutz-1 cell growth (IC(50)) of TPT for 72 h was 272 ng/L. The percentage of apoptotic cells observed in the Mutz-1 cells after exposure to TPT (160 ng/L) in 48 h and 72 h was (54.16 +/-4.29)% and (72.97+/-6.12)%, respectively. TEM showed the characteristics of apoptosis in Mutz-1 cells treated with TPT. The xenotransplanted SCID mice treated with TPT showed inhibited tumor growth compared with control group. TPT treatment resulted in a longer survival as compared with the control group (P<0.001) and with the As2O3-treated group (P<0.001). The cells exposed to TPT exhibited a time-dependent decrease of Top1 protein expression.

CONCLUSIONTPT can inhibit Mutz-1 cell growth and induce apoptosis in vitro.The downregulation of Top1 may be involved in the apoptosis induced by TPT. TPT has a significant antitumor effect in vivo.

Animals ; Antineoplastic Agents ; pharmacology ; therapeutic use ; Apoptosis ; drug effects ; DNA Topoisomerases, Type I ; biosynthesis ; genetics ; Down-Regulation ; Humans ; Mice ; Mice, SCID ; Myelodysplastic Syndromes ; drug therapy ; pathology ; Neoplasm Transplantation ; Topotecan ; pharmacology ; therapeutic use ; Tumor Cells, Cultured

OBJECTIVETo investigate the influence of Lewis y antigen on the gene expression of partial drug resistance associated proteins in human ovarian cancer cell line RMG-I-H.

METHODSRT-PCR was used to determine the gene expressions of partial drug resistance associated proteins in RMG-I-H cell line transfected with alpha1, 2-fucosyltransferases gene and RMG-I cell line, as well as in RMG-I-H treated with or without anti-Lewis y monoclonal antibody at the concentration of 10 micro/g/ml. The immunocytochemical method was used to detect the expression of P-glycoprotein (P-gp) in RMG-I and RMG-I-H cell lines. RMG-I and RMG-I-H cells were transplanted into nude mice and the expression of P-gp in the tissues was measured by immunohistochemistry.

RESULTSThe mRNA expressions of protein kinase C-alpha (PKC-alpha), topoismerase I ( Topo I ), multidrug resistance-associated protein-1 (MRP-1), and MRP-2 were significantly higher in RMG-I-H cells than those in RMG-I cells (0.46 +/- 0.02 vs. 0.27 +/- 0.05, 0.82 +/- 0.08 vs. 0.52 +/- 0.04, 0.66 +/- 0.07 vs. 0.34 +/- 0.12, and 0.44 +/- 0.08 vs. 0.23 +/- 0.05; all P < 0.05). However, the mRNA expression of multi-drug resistance 1 (MDR-1) was significantly lower in RMG-I-H cells than that in RMG-I cells (0.26 +/- 0.05 vs. 0.45 +/- 0.08, P < 0.05). The P-gp level increased in RMG-I-H cells compared with that in RMG-I cells both in vivo and in vitro (P < 0.05). Expressions of MDR-1, MRP-1, MRP-2, PKC-alpha, and Topo I mRNA decreased by the time in RMG-I-H cells treated with anti-Lewis y monoclonal antibody (all P < 0.05), while mRNA expressions of those genes in the control group did not statistically change (P > 0.05). In addition, MDR-1, MRP-1, MRP-2, PKC-alpha, and Topo I mRNA expressions were significantly lower in RMG-I-H cells treated with anti-Lewis y monoclonal antibody than those in the control group at 6 hours (all P < 0.05) and the inhibition ratios were 48.55%, 77.50%, 70.18%, 45.86%, and 46.13%, respectively.

CONCLUSIONThe Lewis y antigen of the human ovarian cancer cell surface is closely correlated with the regulation on the gene expression of partial drug resistance associated proteins.

ATP-Binding Cassette, Sub-Family B, Member 1 ; genetics ; metabolism ; Animals ; Cell Line ; Cell Line, Tumor ; DNA Topoisomerases, Type I ; genetics ; metabolism ; Drug Resistance, Multiple ; Drug Resistance, Neoplasm ; genetics ; Female ; Fucosyltransferases ; Gene Expression ; Gene Expression Regulation ; physiology ; Gene Expression Regulation, Neoplastic ; physiology ; Humans ; Lewis Blood-Group System ; physiology ; Mice ; Mice, Nude ; Multidrug Resistance-Associated Proteins ; genetics ; metabolism ; Ovarian Neoplasms ; Transfection

OBJECTIVETo investigate the expressions of TopI gene in small cell lung cancer cell line H446, and explore the influence of TopI on the chemosensitivity of the cell line to topotecan (TPT).

METHODSWestern blot was performed to detect the TopI expression in H446 cells. Lipofectamine 2000 was used for the transient transfection of H446 cells by siRNA, and the transfection efficacy was detected. TopI mRNA was analyzed by quantitative RT-PCR and TopI protein was detected by Western blot to selected effective siRNA. The drug-sensitivity to topotecan (TPT) was evaluated by MTT assay.

RESULTSTopI gene was expressed in H446 cells. Lipofectamine 2000 mediated the siRNA effectively (88.67%). Compared with its parental cells, RT-PCR results showed that TopI mRNAs in transfected cells were reduced by (95.7 +/- 1.6)%, (90.8 +/- 1.6)%, (96.1 +/- 2.7)% and (96.3 +/- 1.8)%, respectively, and decreased significantly at protein level. By MTT assay, the inhibition rate of TPT to H446 cells transfected by siRNA was lower than that of control group at same concentrations (P < 0.01).

CONCLUSIONsiRNAs can silence the expression of TopI and decrease the drug-sensitivity of H446 cells to TPT.

Antineoplastic Agents ; pharmacology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; DNA Topoisomerases, Type I ; genetics ; metabolism ; Down-Regulation ; Drug Resistance, Neoplasm ; Humans ; Lung Neoplasms ; metabolism ; pathology ; RNA Interference ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; genetics ; Small Cell Lung Carcinoma ; metabolism ; pathology ; Topotecan ; pharmacology ; Transfection