[Preparation and characterization of monoclonal antibody against HCCR protein].

AIM: Preparation of monoclonal antibody (mAb) to HCCR, which is a candidate biomarker for human hepatocellular carcinoma (HCC). METHODS: The recombinant protein HCCR-1(167-360); was expressed and was used as immunogen to immunize mouse for generation of mAb against HCCR. The protein Ep-HCCR, which displayed a epitope of HCCR, was also expressed and purified to use to detect serum antibody titer and to screen the positive clones of hybridmas. The properties of HCCR antibody were analyzed by ELISA, Western blot, immunofluorescence and immunohistochemistry. RESULTS: A hybridmas clone, which secreted anti-HCCR mAb, was obtained. The affinity constant (Kaff) of the mAb is 5.4×10(6); L/mol analyzed by ELISA; Western blot showed that the mAb could specifically recognize HCCR-1 and HCCR-2 expressed in HepG2 cells; The mAb was also used to detect the expression of HCCR proteins in hepatoma cells and HCC tissues. The results of immunofluorescence indicated that HCCR proteins mainly localized on the plasma membrane and cytoplasm of HepG2 cells. In addition, HCCR was found high-expressed in HCC tissues but not in normal liver tissue detected by Immunohistochemistry. CONCLUSION: A specific mAb against HCCR was successfully generated, which laid the foundation for establishing HCC detection method based on HCCR.

[Generation of monoclonal antibody to GP73 based on antigen epitope].

AIM: Preparation of monoclonal antibody (mAb) against GP73 protein. METHODS: The N-terminal peptide (AAAERGAVELK) of GP73 protein was displayed on T7 phage, the recombinant phage was amplified and used as the immunogen to immunize mouse to produce antibody. The titer of the antiserum and the positive hybridoma clones which secreted the mAb against GP73 protein were detected by ELISA. The mAb specificity was assayed by ELISA and Western blot. RESULTS: The high specificity mAb against GP73 protein was selected from the mouse immunized with the recombinant T7 phages displaying the epitope of GP73 by cell fusion and screening. CONCLUSION: The appropriate protein epitope displayed on T7 phage could be used as alternative antigen to immunize animals to make specific antibody against the corresponding native protein.

[Production and identification of a monoclonal antibody against human HPPCn].

AIM: To make monoclonal antibody(mAb) against human HPPCn for the use in research on HPPCn's function and its relationship with liver diseases. METHODS: The female BALB/c mice were immunized with the recombinant HPPCn proteins. Splenocytes and Sp2/0 cells were fused with PEG-1500. The positive clone was identified through indirect ELISA and then subcloned by limited dilution. Indirect ELISA, Western blot and Ig sub-class identification kit were used to identify the mAb's properties. By immunofluorescence experiments, we studied the cellular localization of HPPCn. The mAb epitope was also analyzed using peptide phage display technology. RESULTS: An anti-HPPCn mAb, named W2-D5, was obtained. It belongs to IgG1 subclass. It could specially bind to human HPPCn. Furthermore, by immunofluorescence results, wo confirmed HPPCn located in the nucleus and our mAb could combined with the natural protein. With the mAb, the minimal detectable concentration was 0.1 µg/L for HPPCn; The peptide sequence of HPPCn7₋13;(IHLELRN)was identified as the epitope of the mAb. CONCLUSION: An anti-HPPCn mAb with high specificity and high affinity was successfully obtained.

[Proteomic analysis of paclitaxel-induced apoptosis in MCF-7 human breast carcinoma cells].

OBJECTIVE: To investigate the mechanism of paclitaxel-induced apoptosis in MCF-7 human breast carcinoma cells. METHODS: In this study, the proteins extracted from paclitaxel-induced apoptotic MCF-7 cells were analyzed by 2-dimentional gel electrophoresis (2-DE), and compared with those from untreated MCF-7 cells. The differential proteins were identified by mass spectrometry. RESULTS: At 24 hour after paclitaxel (100 nmol/L) treatment, MCF-7 cells were collected and extracted the whole proteins. Seventeen up-regulated or down-regulated proteins were found by analysis of the differential proteomic 2-DE map. Six of them were identified by mass spectrometry. They were enolase 1, chloride intracellular channel 1, keratin 8, ribosomal protein S12, galectin-1 and histidine triad nucleotide binding protein, respectively. CONCLUSION: We effectively found the changed proteins in the process of paclitaxel-induced apoptosis in MCF-7 human breast carcinoma cells by proteomic techniques. These up-regulated or down-regulated proteins are important molecules for our further research about the mechanism of paclitaxel-induced apoptosis.

A putative NES mediates cytoplasmic localization of Apoptin in normal cells.

Apoptin, a protein expressed by chicken anemia virus, is found predominantly in the cytoplasm in normal cells, whereas it localizes in the nucleus in transformed and malignant cells. However, the mechanisms that regulate the different subcellular localization of Apoptin in normal and tumor cells have not been fully clarified. In this work, a putative nuclear export signal (NES) in Apoptin was predicted. It was testified that the putative NES (pNES) of Apoptin was not a functional NES, but actually acted as a cytoplasmic retention signal. Deletion of the pNES led to the nuclear accumulation of Apoptin in normal cells. In addition, when a strong nuclear localization signal was introduced into Apoptin, it exclusively translocated to the nucleus in normal cells. These observations indicated that the cytoplasmic localization of Apoptin in normal cells results from the balance between cytoplasmic retention and nuclear import. On the other hand, the pNES was also proved to be necessary for Apoptin multimerization. Mutants lacking the pNES did not form obviously visible globular aggregates in normal or tumor cells.

[Construction of phage display antibody library to MCF-7 cells and screening of single-chain antibodies against breast cancer cells].

The aim of this study is to construct a phage display single-chain variable fragment (scFv) library against breast cancer cells and screen the specific antibodies against MCF-7 cells from the library. The BALB/C mice were immunized with MCF-7 cells. Total RNA of spleens was isolated. The heavy-chain (VH) and light-chain variable region genes (VL) of the antibodies were amplified by RT-PCR and joined into a single chain by overlapping PCR with a linker DNA encoding the peptide (Gly4Ser)3. The assembled scFv fragments were cloned into the phagemids(pCANTAB5E) and the recombinant phagemids were used to transform competent E. coli TG1. The transformed TG1 cells were infected by helper phage M13KO7 and the recombinant phagemids were rescued. The scFv fusion proteins were displayed on the surfaces of the recombinant phages. A phage display antibody library of repertoire of 1.2 x 10(6) clones was constructed. The specific antibodies against MCF-7 cells were enriched by 75 times after five rounds of affinity selection. Ten recombinant phages clones that exhibited specific binding to MCF-7 cells were identified. The specificity of those phage clones was analyzed by reactivity against HepG2 cells and Hela cells by ELISA. One of the selected phage clones against MCF-7cells was used to infect E. coli TOP10 to produce the soluble scFv antibodies after induction with IPTG. The strategy of construction and screening of antibody library directed against the whole tumor cells described in this report should be generally applicable to generate tumor cell-specific antibodies.