title: GUCY2C lysosomotropic endocytosis delivers immunotoxin therapy to metastatic colorectal cancer.
abstract: The emergence of targeted cancer therapy has been limited by the paucity of determinants which are tumor-specific and generally associated with disease, and have cell dynamics which effectively deploy cytotoxic payloads. Guanylyl cyclase C (GUCY2C) may be ideal for targeting because it is normally expressed only in insulated barrier compartments, including intestine and brain, but over-expressed by systemic metastatic colorectal tumors. Here, we reveal that GUCY2C rapidly internalizes from the cell surface to lysosomes in intestinal and colorectal cancer cells. Endocytosis is independent of ligand binding and receptor activation, and is mediated by clathrin. This mechanism suggests a design for immunotoxins comprising a GUCY2C-directed monoclonal antibody conjugated through a reducible disulfide linkage to ricin A chain, which is activated to a potent cytotoxin in lysosomes. Indeed, this immunotoxin specifically killed GUCY2C-expressing colorectal cancer cells in a lysosomal- and clathrin-dependent fashion. Moreover, this immunotoxin reduced pulmonary tumors>80% (p<0.001), and improved survival 25% (p<0.001), in mice with established colorectal cancer metastases. Further, therapeutic efficacy was achieved without histologic evidence of toxicity in normal tissues. These observations support GUCY2C-targeted immunotoxins as novel therapeutics for metastatic tumors originating in the GI tract, including colorectum, stomach, esophagus, and pancreas.
authors.affiliation: School of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, PA.
authors.forename: Glen P
authors.initials: GP
authors.lastname: Marszalowicz
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA USA.
authors.forename: Adam E
authors.initials: AE
authors.lastname: Snook
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Magee
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA USA.
authors.forename: Dante
authors.initials: D
authors.lastname: Merlino
authors.affiliation: Cancer Biology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Lisa D
authors.initials: LD
authors.lastname: Berman-Booty
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Waldman
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000276:immunology*; D022461:Caveolins / Q000378:metabolism; D045744:Cell Line, Tumor; D002966:Clathrin / Q000378:metabolism; D004337:Drug Carriers; D004705:Endocytosis; D005770:Gastrointestinal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D007167:Immunotherapy; D000922:Immunotoxins / Q000008:administration & dosage / Q000494:pharmacology*; D008247:Lysosomes; D051379:Mice; D058990:Molecular Targeted Therapy; D021381:Protein Transport; D034622:RNA Interference; D034741:RNA, Small Interfering; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled / Q000378:metabolism*; D018000:Receptors, Peptide / Q000378:metabolism*; D012276:Ricin / Q000008:administration & dosage / Q000235:genetics / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D022461:Caveolins; D002966:Clathrin; D004337:Drug Carriers; D000922:Immunotoxins; D034741:RNA, Small Interfering; D018000:Receptors, Peptide; D012276:Ricin; C000613655:Gucy2c protein, mouse; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled