ABSTRACT
HER2, a member of epidermal growth factor receptor family proteins, is overexpressed in about 30% of human breast cancer. Increased levels of HER2 are associated with poor patient prognosis and enhanced metastasis. RNA interference (RNAi) is developed recently as a new technique which can inhibit gene expression specifically in mammalian cells. On the basis of previous study,in which two target sequences with favorable RNAi effect on HER2 were identified, a series of dual promoter siRNA-expressing vectors containing two opposing U6 and H1 promoters were constructed. After transfection of HER2-overexpressing SKBR3 breast cancer cells with the siRNA-expressing vectors, downregulation of HER2 was identified quantitatively. Subsequently, the siRNA-expressing cassettes were subcloned into lentiviral vectors by LR recombination reaction and lentivirus was prepared successfully. The results from infection of SKBR3 cells with siRNA-expressing lentivirus demonstrated that lentiviral-mediated RNAi could downregulate HER2 expression efficiently through fluorescent quantitative PCR (FQ-PCR), western blot, and FACS analysis. Furthermore, cell growth was inhibited in cell proliferation assay after treatment with siRNA lentivirus.A new tool for clarifying the function of HER2 in cancer metastasis and developing the gene therapy drug was offered.
ABSTRACT
The Her-2 proto-oncogene encodes a 185kDa transmenbrane glycoprotein p185 which has intrinsic tyrosine kinase activity. It is overexpressed in several malignant human tumors like breast cancer. A chimeric antibody by assembling a single-chain Fv antibody and a human IgG1 Fc fragment was constructed. This chimeric antibody reacts with tumor surface antigen p185c-erbB-2 specifically. In order to put the antibody into clinical application, two steps purification method was used to attain the antibody’s purity more than 95%. Both the lyophilized pharmaceutical formulations of the antibody were found. The formulations can keep the stability and activity of the antibody for at least one year. These results were the foundation of the chimeric antibody for cancer therapy.
ABSTRACT
Transmembrane protein p185 (the product of Her2/c-erbB-2 gene) is a member of the epidermal growth factor receptor (EGFR) family. Its overexpression was found in about 30% of breast cancer. It is essential to obtain soluble extracellular domain (ECD) of p185, especially disulfide bond rich domains, for identifying the epitopes of anti-p185 antibodies and researching the interrelationship between the antigen and antibody. The disulfide bond rich domain I-II and domain IV of p185 ECD were amplified from plasmid pBabe/erbB-2 by PCR respectively. These two fragments were inserted into pGEX/4T-1 vector, transfected into E. coli Origami B (DE3) pLysS and expressed inductively by low concentration of IPTG and low temperature overnight. After the pressure lysis of cells, the supernatants were analyzed by SDS-PAGE and the result demonstrated that this GST-fusion protein was expressed solubly in the amount of 10-15 mg/L. By the ELISA, Western blot and other immunological assays, the fusion proteins and their GST cut-off derivates both showed binding activities with several anti-p185 antibodies respectively. These results indicated that it was a feasible and effectual method to express disulfide bond rich domain I-II and domain IV of p185 ECD and this method may also be used to express other disulfide bond rich proteins.