Expression of recombinant human BMP6 in CHO cells by fused to the signal peptide and propeptide of another homologue protein / 生物工程学报

BMP6 is a member of TGF-beta superfamily, represent more effective osteogenic activity. Two recombinant plasmids were constructed to expression rhBMP6 in mammalian cells, one contained the cDNA encoding the signal peptide, propeptide and mature peptide of human BMP6, wich was named pcDNA-BMP6, the other contained the recombinant DNA encoding the signal peptide, propeptide of human BMP2 and the mature peptide of BMP6, which was named pcDNA-BMP2/6. Transient expression in Cos7 cells demonstrated that the pcDNA-BMP2/6 produced more rhBMP6 than pcDNA-BMP6. For stable expression, the CHO-dhfr- cells were transfected with pcDNA-BMP2/6 and pSV2-dhfr, then screened by G418 and treated with MTX for targeting gene amplification. The partially purified rhBMP6 by heparin affinity chromatography was shown to possess bone induction activity tested by the induction of alkaline phosphatase activity in C2C12 cells.

Expression, characterization and biological activity analysis of recombinant human bone morphogenetic protein 2 in CHO cells / 生物工程学报

Bone morphogenetic protein 2(BMP-2) is a member of the of BMPs family, its osteoinductive capacity has already been demonstrated. We tried to express hBMP-2 in CHO cell. In this study, we inserted hBMP-2 cDNA into vector pCDNA3.1(+) to construct hBMP-2 eukaryotic expression vector pCDNA3.1(+)-hBMP-2. Recombinant Chinese hamster ovary (rCHO) cell line expressing high-level recombinant human bone morphogenetic protein 2(rhBMP-2) was constructed by co-transfecting the expression vectors pCDNA3.1(+)-hBMP-2 and plasmid pSV2-dhfr into dihydrofolate reductase (dhfr)-deficient CHO cells and the subsequent gene amplification in medium containing stepwise increments in methotrexate level such as 0.1 and 1 micromol/L. Western blot analyses showed a specific band of about 18 kD in reduced sample lane and a specific band of about 32 kD in non-reduced sample lane, this indicated that rCHO cells secret rhBMP-2 as a homodimeric glycoprotein form. Finally, we obtained a single clone cell strain expressing a high level (7.83 microg/24 h/10(6) cells) of rhBMP-2 tested by ELISA. Biological activity of rhBMP-2 was tested by the induction of alkaline phosphatase(ALP) activity in C2C12 cells. We treated C2C12 with different concentration of rhBMP-2 condition medium(CM) for 5d. The results showed that the rhBMP-2 could significantly increase the ALP activity of C2C12.

Activation of bone morphogenetic protein-6 gene transcription in MCF-7 cells by estrogen / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Bone morphogenetic protein-6 (BMP-6) is closely correlated with tumor differentiation and skeletal metastasis. Estrogen is considered as a stimulant for the initiation and promotion of breast cancer. Previous studies demonstrated that 17beta-estadiol (E2) can selectively increase the expression of BMP-6. This experiment is designed to detect the molecular mechanism of estrogen activating BMP-6 gene transcription in human estrogen receptor positive (ER+) breast cancer cell line MCF-7.</p><p><b>METHODS</b>After the treatment of MCF-7 cells with E2 at different concentrations (10(-11) mol/L, 10(-9) mol/L, 10(-7) mol/L), the BMP-6 expression level was examined through real-time polymerase chain reaction. Through restriction enzyme digestion, human BMP-6 1.2 kb long promoter, BMP-6 0.7 kb long promoter was cloned into pGL-3 basic vector; after the treatment with 10(-7) mol/L E2, luciferase activities of the two promoters were detected. Site-directed mutagenesis was performed to obtain the mutant forms of estrogen response element half-site (1/2 ERE) element and Sp1 sites in the BMP-6 promoter, the activities of these mutant form promoters were detected following the methods mentioned above. Chromatin immunoprecipitation (ChIP) assay was also used to confirm the binding of estrogen receptor alpha (ERalpha) on BMP-6 promoter in the presence of E2.</p><p><b>RESULTS</b>E2 dose dependently increased BMP-6 mRNA expression in human ER+ breast cancer cell line MCF-7. At a dose of 10(-7) mol/L E2, human BMP-6 1.2 kb promoter activity was increased by 90% compared with the control group treated with ethanol (P < 0.05). Both the 1/2 ERE response element mutant form and the Sp1 site mutant form of the BMP-6 promoter abolished the activation of the BMP-6 promoter's response to E2. Through ChIP assay, the binding of ERalpha on 1/2 ERE response element in BMP-6 promoter was further validated.</p><p><b>CONCLUSION</b>Estrogen induces BMP-6 expression in human ER+ breast cancer cell line MCF-7 through its receptor ERalpha binding on 1/2 ERE element in the BMP-6 promoter.</p>