OBJECTIVETo better understand the molecular mechanism of tumorigenesis and progression, the monoclonal antibody against G3BP (Ras-GAP SH3 binding protein), which serves as an important downstream effector of Ras signaling, was prepared, characterized and utilized in analysis of various human tumors.

METHODSBy using the prokaryotic expression vector pGEX-5X1, GST-G3BP fusion protein was expressed in E. coli BL21 under induction of IPTG. Purified GST-G3BP fusion protein was used to immunize BALB/c mice. The monoclonal antibody against G3BP was produced through conventional hybridoma method and characterized by ELISA, Western blot and immunohistochemical staining.

RESULTSA hybridoma cell line secreting anti-G3BP IgG1 subtype antibody was obtained. Western blot and competitive inhibition assay showed that the antibody was G3BP-specific. Immunohistochemical staining demonstrated that G3BP was over-expressed in formalin-fixed and paraffin-embedded tissues of some human tumors, such as lung cancer, colon cancer, gastric cancer and breast cancer. In breast cancer specimens, the degree of G3BP expression correlated positively with the presence of lymph node metastasis and c-erbB2 expression.

CONCLUSIONSThe G3BP-specific monoclonal antibody derived from recombination protein can be used in ELISA, Western blot and immunohistochemical assay. It may provide an important tool in analysis of G3BP in in vitro and in vivo experiments. Besides, G3BP may serve as another prognostic marker for breast cancer.

Animals ; Antibodies, Monoclonal ; biosynthesis ; immunology ; Biomarkers, Tumor ; Breast Neoplasms ; metabolism ; pathology ; Carrier Proteins ; genetics ; immunology ; metabolism ; DNA Helicases ; Female ; Genetic Vectors ; Humans ; Hybridomas ; secretion ; Lymphatic Metastasis ; Male ; Mice ; Mice, Inbred BALB C ; Poly-ADP-Ribose Binding Proteins ; RNA Helicases ; RNA Recognition Motif Proteins ; Receptor, ErbB-2 ; metabolism ; Recombinant Fusion Proteins ; genetics ; metabolism ; Tumor Cells, Cultured

Tumor hypoxia contributes to the progression of a malignant phenotype and resistance to ionizing radiation and anticancer drug therapy. Many of these effects in hypoxic tumor cells are mediated by expression of specific set of genes whose relation to therapy resistance is poorly understood. In this study, we revealed that DNA-dependent protein kinase (DNA-PK), which plays a crucial role in DNA double strand break repair, would be involved in regulation of hypoxia inducible factor-1 (HIF-1). HIF-1beta-deficient cells showed constitutively reduced expression and DNA-binding activity of Ku, the regulatory subunit of DNA-PK. Under hypoxic condition, the expression and activity of DNA- PK were markedly induced with a concurrent increase in HIF-1alpha expression. Our result also demonstrated that DNA-PK could directly interact with HIF- and especially DNA-PKcs, the catalytic subunit of DNA-PK, could be involved in phosphorylation of HIF-1alpha, suggesting the possibility that the enhanced expression of DNA- PK under hypoxic condition might attribute to modulate HIF-1alpha stabilization. Thus, the correlated regulation of DNA-PK with HIF-1 could contribute to therapy resistance in hypoxic tumor cells, and it provides new evidence for developing therapeutic strategies enhancing the efficacy of cancer therapy in hypoxic tumor cells.
Antibodies/immunology ; Cell Hypoxia ; Cell Line, Tumor ; DNA Helicases/immunology/metabolism ; DNA-Binding Proteins/genetics/*metabolism/*physiology ; Deferoxamine/pharmacology ; Drug Resistance, Neoplasm/*physiology ; Humans ; Immunoprecipitation ; Neoplasms/enzymology/*metabolism ; Nuclear Proteins/genetics/*metabolism/physiology ; Phosphorylation ; Protein-Serine-Threonine Kinases/metabolism/*physiology ; Research Support, Non-U.S. Gov't ; Transcription Factors/genetics/*metabolism/physiology ; Up-Regulation

In order to identify rat ovarian germ cells, we expressed and purified rat RVLG protein in Escherichia coli cells and prepared a mouse anti-rat RVLG polyclonal antibody. The rat RVLG cDNA was obtained from rat testicle tissue by RT-PCR and was cloned into the vector pMD19-T. Sequence analysis proves that the cloned RVLG cDNA fragment was 60 bp longer than that released in the GenBank (NM_001077647), resulting from an alternative splicing of the RVLG pre-mRNA. The RVLG cDNA was double digested with the restriction endonucleases BamH I and EcoR I, and then was extracted from gel and inserted into the prokaryotic expression vector pGEX-4T-1. The recombinant expression plasmid pGEX-RVLG was verified for successful construction and then was transformed into Escherichia coli BL21(DE3) for induction to express the GST-RVLG fusion protein by IPTG. The GST-RVLG fusion protein was expressed in Escherichia coli BL21 (DE3) at a high level which accounts for more than 10% of the total bacterial cellular protein. The purified RVLG protein was used as an antigen to immunize KM mouse for the production of polyclonal antibody in ascetic fluid followed by celiacly injecting the mouse with S180 cells. The mouse anti-rat RVLG antibody was analyzed by ELISA, Western blotting and immunohistochemistry for its specificity and titer. The antibody could recognize RVLG protein specifically and its titer was about 1:20 000. These results confirm that the mouse anti-rat RVLG polyclonal antibody with high affinity and specificity has been prepared successfully, and lay a foundation for our ongoing research on the specific expression of RVLG in rat ovary.
Animals ; Antibodies, Monoclonal ; biosynthesis ; Base Sequence ; Cloning, Molecular ; DEAD-box RNA Helicases ; biosynthesis ; genetics ; immunology ; DNA, Complementary ; biosynthesis ; genetics ; Escherichia coli ; genetics ; metabolism ; Female ; Mice ; Molecular Sequence Data ; Ovary ; cytology ; metabolism ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; immunology