Nystatin Regulates The Endocytosis And Uptake Of Endostatin And EGFR Antibody

In eukaryotic cells, endocytosis is an important cellular process whichparticipates in the regulation of various cell signaling pathways and the uptake ofmultiple materials. In the field of tumor biology, endocytosis also plays a crucial rolein the uptake and biodistribution of antitumor drugs.Tumor induces the formation of new blood vessels (angiogenesis) inside tumortissue in order to sustain its growth and metastasis. Inhibition of tumor angiogenesishas been intensely investigated as an effective strategy of antitumor therapy.Endostatin is a potent inhibitor of tumor angiogenesis. Although the internalization ofendostatin in endothelial cells has been widely observed, the specific mechanism ofendostatin endocytosis still remains elusive. In this study, we establish for the firsttime that endostatin internalization involves two classic endocytic pathways: lipidraft-dependant pathway and clathrin-dependant pathway. In addition, nystatin, acholesterol chelator, significantly enhances endostatin internalization via facilitatingthe translocation of endostatin out from lipid raft pathway into clathrin-dependantpathway. More importantly, we demonstrate that the combined treatment of nystatinand endostatin promotes the uptake of endostatin in tumor tissue, resulting in elevatedantiangiogenesis and antitumor efficacies of endostatin in vivo.The use of tumor-targeting agents is another promising strategy in the treatmentof tumor. We identify that the monoclonal antibody against tumor epidermal growthfactor receptor (EGFR) shares a similar endocytic pattern with endostatin. Nystatinalso promotes the internalization and uptake of EGFR mAb (cetuximab) in tumorcells and tumor tissues. Nystatin-enhanced EGFR mAb uptake leads to dramaticallyelevated antitumor efficacies of EGFR mAb in vivo. Nystatin also enhances theuptake and efficacy of an antibody-drug conjugate (ADC) which is synthesized byconjugating cytotoxic drug doxorubicin to EGFR mAb (cetuximab-doxorubicin).