Herceptin-NKG2D Ligand Fusion Protein In Anti-tumor Research

Malignant tumors are the serious threat to human health. Traditional treatment methods include: surgical therapy, radiotherapy and chemotherapy. Surgical therapy does not have effect on the metastatic tumor or cancer cells in the blood; radiotherapy and chemotherapy can not only kill cancer cells in short term, but also normal cells.It is difficult to cure cancer with the traditional therapies. Therefore, the tumor targeted therapy has become an important strategy to cure the malignant tumors.With the development of monoclonal antibody technology, antibody therapy has become a new way to treat cancer. Antibody therapy compared with other treatment methods is more specificity, lower toxicity and easier to take other anti-tumor drugs to target cells for inducing immune responses. There are already a variety of antibodies through clinical trials, Herceptin is an antibody drug firstly approved by the U.S. Food and Drug Administration (FDA) for treatment of solid tumor in cancer therapy. Although the antibody therapy has many advantages compared with conventional treatment, there are still many deficiencies: firstly, the cost of antibody drug production is too much; secondly, the technology is difficult to be grasped; thirdly, the dose used for solid tumors is much.Natural killer cells (NK cells) are a class of lymphocytes in innate immune system. Its surface is dotted with activated receptor of NKG2D. Breast cancer, ovarian cancer and mostly the epithelial tumor cells express NKG2D ligands, such as MIC-I chain related protein: MICA and MICB. FcγRIII (CD16) on surface of NK cells recognises Fc fragment of antibody and induces antibody-dependent cell-mediated cytotoxicity (ADCC).The research through the transformation of the table contains the treatment of solid tumors and efficient anti-HER-2 humanized monoclonal antibody Herceptin gene in adenovirus type 5, in the antibody heavy chain constant region 3 (CH3) gene connected to NKG2D ligand MICB genes, composition of a Herceptin-NKG2D ligand fusion protein gene. The pupose of this study to prove whether Herceptin-NKG2D ligand fusion protein has stronger anti-tumor effects than Herceptin. Further, fusion protein combined with NK cells could induce ADCC to kill tumor cells efficiently. We hoped that the Herceptin-NKG2D ligand fusion protein could have a effect of"fusion protein combine with NK cells".The novel idea of this subject: We cloned the full-length antibody (Herceptin) gene and NKG2D ligand (MICB) gene into vector pDC339-AT5, then recombined to adenovirus vector (pBHGloxΔE1,3Cr). The recombinant adenovirus named Ad-AT5-MICB expressed fusion protein, then propagated in 293 cells, purified and measured virus titers. In vitro, lactate dehydrogenase (LDH) release method was used to prove if fusion protein has the effect in killing ovarian cancer cells (SK-OV-3).In this project, the fusion protein were highly expressed by adenovirus both have full-length antibodies gene and MICB gene in vitro. The fusion protein is effective to kill tumor cell. Anti-tumor effect of the fusion protein in mice is need to be proved through more experiments. As a result, adenovirus mediated gene therapy based the fusion protein is a viable method in tumor targeted therapy.