Tn-targeted antibody and immunotoxin for cancer therapy

Alteration in the carbohydrate present on the cell surface will lead to cell dysfunction and cell transformation as demonstrated by over-expression of carbohydrate antigen (Tumor-Associated Carbohydrate Antigens, TACAs) presented on the cell surfaces of malignant cells. The truncated O-glycans, Tn, are correlated with metastatic potential and poor prognosis in many cancers, such as ovary, prostate cancer and breast cancer. Our previous developed anti-Tn vaccine can effectively induce high affinity anti-Tn IgG antibody and increase the survival rate of Prostate Cancer in Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) mice. We also performed immunohistochemical (IHC) staining of 26 prostate cancer and 50 breast cancer samples with anti-Tn antibody. We observed that the intensity of IHC staining with anti-Tn antibody is proportional to the malignancy of cancer. Actually, in health tissue, O-linked N-acetylgalactosamine (Tn) is generally masked by covalently bound terminal carbohydrate moieties, but its expression often associated with human carcinomas. Thus, Tn is an excellent candidate for cancer immunotherapy. In this study, we have successfully cloned the cDNA of the heavy chain and light chain of anti-Tn mouse monoclonal antibody and expressed the recombinant anti-Tn antibody. We also cloned the cDNA encoding the single chain anti-Tn antibody (anti-Tn scFv Ab) and engineered it to Tn-targeted specific toxin. Thus, the following experiments are proposed: (1) To prove the concept that anti-Tn antibody can be used for cancer immunotherapy and to examine the therapeutic effectiveness of anti-Tn antibody in syngeneic mice tumor model. Once the concept is demonstrated, we will humanize anti-Tn antibody for further examination of clinical trial. (2)To develop Tn-targeted immunotoxin for cancer therapy in syngeneic mice tumor model.