title: Tumor regression mechanisms by IL-13 receptor-targeted cancer therapy involve apoptotic pathways.
abstract: IL-13 cytotoxin, composed of IL-13 and a truncated form of Pseudomonas exotoxin, targets IL-13R-overexpressing tumor cell lines in vitro and in vivo. To reveal the molecular mechanism of IL-13 cytotoxin-induced cell death in vivo, we demonstrate activation of apoptotic pathways in 2 s.c. growing human SCCHN tumor models in immunodeficient mice after i.t. administration of IL-13 cytotoxin. Treatment of HN12 tumor bearing mice with i.p. or i.t. administration of IL-13 cytotoxin mediated marked regression of established tumors with complete remission. Interestingly, after a single i.t. administration, IL-13 cytotoxin disappeared within 6 hr but accumulation of caspase-3, -8 and -9 and cleavage of procaspase-3 and PARP continued within the tumors for a prolonged period. We further demonstrate that IL-13 cytotoxin also utilizes an alternate pathway of cell death via the release of cytochrome c from mitochondria to the cytosol. Our results indicate that IL-13 cytotoxin induces 2 major pathways of apoptosis, which may play a role in tumor regression. In addition, apoptotic molecules may serve as surrogate molecular markers of tumor response to IL-13R-directed cytotoxin therapy.
authors.affiliation: Laboratory of Molecular Tumor Biology, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
authors.forename: Mariko
authors.initials: M
authors.lastname: Kawakami
authors.forename: Koji
authors.initials: K
authors.lastname: Kawakami
authors.forename: Raj K
authors.initials: RK
authors.lastname: Puri
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001427:Bacterial Toxins / Q000235:genetics; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D005098:Exotoxins / Q000235:genetics; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D020287:In Situ Nick-End Labeling; D018793:Interleukin-13 / Q000494:pharmacology*; D053661:Interleukin-13 Receptor alpha1 Subunit; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008928:Mitochondria / Q000378:metabolism; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000628:therapy*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011550:Pseudomonas aeruginosa; D018123:Receptors, Interleukin / Q000378:metabolism; D053660:Receptors, Interleukin-13; D011993:Recombinant Fusion Proteins / Q000494:pharmacology*; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured; D037521:Virulence Factors / Q000235:genetics; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D020169:Caspases; D003574:Cytochrome c Group; D005098:Exotoxins; D018793:Interleukin-13; D053661:Interleukin-13 Receptor alpha1 Subunit; D011065:Poly(ADP-ribose) Polymerases; D018123:Receptors, Interleukin; D053660:Receptors, Interleukin-13; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C508181:IL13RA1 protein, human; C508183:Il13ra1 protein, mouse