Objective To investigate the effect of TGF-β1/SMAD signaling pathway on K562 cells growth inhibition caused by HMBA. Methods After establishing the in vitro differentiation model with HMBA on K562 cells, the MTT assay was used to detect the proliferation of K562 cells, the cell cycle profile was detected by flow cytometry, and the mRNA expression of TGF-β1, SMAD3, SMAD4 and EVI1 was measured by RT-PCR assay. Results HMBA could inhibit the proliferation and promote the differentiation of K562 cells obviously, which was time and concentration-dependent, and the 72 h corresponding IC50, was about 2 mmol/L. Within 72 h, flow cytometry assay indicated that the ration of G0-G1 phase cells was up-regulated, and the results of RT-PCR showed that relative mRNA expression of TGF-β1, SMAD3 and SMAD4 at mRNA level was increased gradually while that of EVI1 was decreased gradually. Conclusion HMBA can inhibit K562 cells proliferation through TGF-β1/SMAD signaling pathway.

Objective To study effect and mechanism of fungus polysaccharide PSM-a of Polyporus sp.M05 on S180 bearing mice. Methods MTT method was used to detect the inhibiting role of PSM-a on S180 cells proliferation in vitro. S180 mice model was established,and was administered by gavage. Tumor volume was detected, and the ratio of tumor to mile weight and inhibiting tumor rate. The activity of NK and LAK cells on the target cells was analyzed by MTT colorimetric assay ;HE stain was used to detect the necrosis of tumor cells. Results PSM-a could inhibit S180 cells grouth in vitro. PSM-a could decrease the tumor weight and increase the ratio of tumor volume and mice weight; Tumor inhibiting rate reached 80% and above when treated with 250 μg/nml PSM-a. PSM-a could increase the activity of NK and LAK cells, and necrosis happened. Conclusion PSM-a could significantly inhibit the growth of S180 cells, and the mechanism bnay be related with the increased killing activity of immunne cells to tumor cells.

Objective To detect the proliferation inhibition and apoptosis of HL-60 cell induced by APS-1 and APS-2 isolated from Polyporus sp. M05 and to investigate its mechanism. Methods The proliferation inhibition was detected by living cells count method,and chosed proper concentration.Flow cytometry with propidium iodide staining was used to detect cell apoptosis. Semi-quantitative RT-PCR was used to detect the expression of apoptosis related gene. Results APS-1 and APS-2 could significantly inhibit the proliferation of HL-60 cells on a time and dose dependent manner. Apoptosis ratio increased to 47. 9% and 26. 8% after HL-60 cells were exposed to APS-1 and APS-2 respectively for 48 h,and the differences had statistical significance (P <0.01). After being induced by APS-1,mRNA of Bax,Fas,Caspase-3 was upregulated. And after being induced by APS-2,mRNA of Bax,Caspase-3 was upregulated,while Fas mRNA did not change. Conclusion APS-1 and APS-2 can inhibit the proliferation and induce apoptosis of HL-60 cells. Mechanism of HL-60 cell apoptosis induced by APS-1 is related to both mitochondrial pathway and Fas signaling pathway,while apoptosis induced by APS-2 is only related to mitochondrial pathway.

Objective To evaluate the positive effects of cisplatin on sensitivity of human glioma U251 to tumor necrosis factor-related apoptosis inducing ligand and to investigate the potential mechanism. Methods The expression of green fluorescent protein (GFP) in U251 which was transfected with pAdxsi-GFP-TRAIL was observed by inverted fluorescent microscope ×400) and to ascertain the MOI. The proliferation inhibition was studied by MTT method. Morphological change was detected through inverted florescent microscope and the Hoechst33342 staining assay was used to verify whether cell apoptosis could be induced or not. The cell apoptosis was also analyzed by flow cvtometry with propidium iodide staining. Semi-quantitative RT-PCR was introduced to detect the mRNA expression of apoptosis related gene.Results The expression of TRAIL mRN A was significantly upregulated after transfection. Compared with treatment group of cisplatin and TRAIL alone, the proliferation of U2S1 was significantly inhibited in the cisplatin sensitizing TRAIL group (P < 0.05 ). Nuclear shrinkage and pyknosis fragmentation were observed by Hoechst 33342 staining assay; Apoptotic peak was detected from the results of flow cvtometry and there were significant differences between the sensitizing group and the other two groups ( P < 0.05 ) ; Moreover, the relatively high expression of TRAIL, DR5, caspaseS and down - regulated survivin genes were also observed. There was no significant changes in DR4 expression. Conclusion Cisplatin could extremely enhance the sensitivity of U251 cells to TRAIL And the potential mechanism may related to the increase of TRAIL, DRS, caspaseS genes while the reduction of surivivin gene.

Proteolytic processing of viral polyproteins is indispensible for the lifecycle of coronaviruses. The main protease (M(pro)) of SARS-CoV is an attractive target for anti-SARS drug development as it is essential for the polyprotein processing. M(pro) is initially produced as part of viral polyproteins and it is matured by autocleavage. Here, we report that, with the addition of an N-terminal extension peptide, M(pro) can form a domain-swapped dimer. After complete removal of the extension peptide from the dimer, the mature M(pro) self-assembles into a novel super-active octamer (AO-M(pro)). The crystal structure of AO-M(pro) adopts a novel fold with four domain-swapped dimers packing into four active units with nearly identical conformation to that of the previously reported M(pro) active dimer, and 3D domain swapping serves as a mechanism to lock the active conformation due to entanglement of polypeptide chains. Compared with the previously well characterized form of M(pro), in equilibrium between inactive monomer and active dimer, the stable AO-M(pro) exhibits much higher proteolytic activity at low concentration. As all eight active sites are bound with inhibitors, the polyvalent nature of the interaction between AO-M(pro) and its polyprotein substrates with multiple cleavage sites, would make AO-M(pro) functionally much more superior than the M(pro) active dimer for polyprotein processing. Thus, during the initial period of SARS-CoV infection, this novel active form AOM(pro) should play a major role in cleaving polyproteins as the protein level is extremely low. The discovery of AOM(pro) provides new insights about the functional mechanism of M(pro) and its maturation process.
Coronavirus ; metabolism ; Cysteine Endopeptidases ; Endopeptidases ; metabolism ; Humans ; Peptides ; chemistry ; metabolism ; Polyproteins ; chemistry ; metabolism ; Protein Binding ; SARS Virus ; chemistry ; metabolism ; Viral Proteins