ABSTRACT
Mucin1 (MUC1) is a highly glycosylated transmembrane protein that plays a crucial role in the lubrication and protection of normal epithelial cells. However, MUC1 has emerged as a potential target for cancer therapy because it is overexpressed and functions in several types of cancers. Recently, we produced a monoclonal antibody (the anti-hMUC1 antibody) specific to the extracellular region of the MUC1 subunit MUC1-C to evaluate the utility of using anti-MUC1 antibodies in pancreatic cancer models. The anti-hMUC1 antibody recognized the MUC1-C protein in pancreatic cancer cells. Based on immunostaining and confocal image analyses, the anti-hMUC1 antibody initially bound to the cell membrane then was internalized in cancer cells that express MUC1. The anti-hMUC1 antibody suppressed epidermal growth factor (EGF)-mediated extracellular signalâ»regulated kinase (ERK) phosphorylation and cyclin D1 expression. When the anti-hMUC1 antibody was injected into a xenograft mouse model and traced using an in vivo imaging system, we observed that the anti-hMUC1 antibody was localized to MUC1-expressing pancreatic tumors. Importantly, the anti-hMUC1 monoclonal antibody suppressed pancreatic tumor growth in mice. According to immunohistochemistry analysis using a pancreatic cancer tissue array and the anti-hMUC1 antibody, MUC1 was highly expressed in human pancreatic cancer tissues compared to normal tissues. Therefore, we conclude that the anti-hMUC1 antibody specifically targets MUC1 and suppresses its function in pancreatic cancer in vitro and in vivo and can be further developed as a promising targeted therapy to treat pancreatic cancer.
Subject(s)
Antibodies, Monoclonal/administration & dosage , Antineoplastic Agents, Immunological/administration & dosage , Mucin-1/metabolism , Pancreatic Neoplasms/drug therapy , Up-Regulation/drug effects , Animals , Antibodies, Monoclonal/pharmacology , Antineoplastic Agents, Immunological/pharmacology , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Extracellular Signal-Regulated MAP Kinases/metabolism , Gene Expression Regulation, Neoplastic/drug effects , Humans , Mice , Pancreatic Neoplasms/immunology , Phosphorylation/drug effects , Treatment Outcome , Xenograft Model Antitumor AssaysABSTRACT
Background: Mucin1 (MUC1) is a highly glycosylated transmembrane protein that has gained attention because of its overexpression in various cancers. However, MUC1-targeted therapeutic antibodies have not yet been approved for cancer therapy. MUC1 is cleaved to two subunits, MUC1-N and MCU1-C. MUC1-N is released from the cell surface, making MUC1-C a more reasonable target for cancer therapy. Therefore, we produced a monoclonal antibody (anti-hMUC1) specific to the extracellular region of MUC1-C and evaluated its effects in vitro and in vivo. Methods: We produced a monoclonal antibody (anti-hMUC1) using a purified recombinant human MUC1 polypeptide and our novel immunization protocol. The reactivity of anti-hMUC1 was characterized by ELISA, western blotting and immunoprecipitation analyses. The localization of the antibody in the breast cancer cells after binding was determined by confocal image analysis. The effects of the antibody on the growth of cells were also investigated. We injected anti-hMUC1 and performed in vivo tracing analysis in xenograft mouse models. In addition, expression of MUC1 in tissue sections from patients with breast cancer was assessed by immunohistochemistry with anti-hMUC1. Results: The anti-hMUC1 antibody recognized recombinant MUC1 as well as native MUC1-C protein in breast cancer cells. Anti-hMUC1 binds to the membrane surface of cells that express MUC1 and is internalized in some cancer cell lines. Treatment with anti-hMUC1 significantly reduced proliferation of cells in which anti-hMUC1 antibody is internalized. Furthermore, the anti-hMUC1 antibody was specifically localized in the MUC1-expressing breast cancer cell-derived tumors in xenograft mouse models. Based on immunohistochemistry analysis, we detected significantly higher expression of MUC1 in cancer tissues than in normal control tissues. Conclusion: Our results reveal that the anti-hMUC1 antibody targets the extracellular region of MUC1-C subunit and may have utility in future applications as an anti-breast cancer agent.