title: Apoptotic pathways of cell death induced by an interleukin-13 receptor-targeted recombinant cytotoxin in head and neck cancer cells.
abstract: Interleukin 13 receptor (IL-13R)-targeted cytotoxin, IL13-PE38QQR, composed of IL-13 and a mutated form of Pseudomonas exotoxin (PE), is found to be highly and specifically cytotoxic to human solid cancer cell lines. However, the mechanism of tumor cell death mediated by IL-13 toxin is still not known. To elucidate the mechanism, we utilized four head and neck cancer cell lines (SCC-25, HN12, KCCT873, and YCUM911), which express high levels of IL-13R, and IL-13 toxin is highly cytotoxic to these cells. We observed chromatin condensation and DNA fragmentation, indicating apoptotic cell death, after treatment with IL-13 toxin, as determined by bis-benzimide staining and DNA ladder assays. However, IL-13 did not induce cell death. Flow cytometric analysis suggested that these cancer cell lines increased the sub-G1/G0 phase DNA population in a dose- and time-dependent manner (ranged between 10 and 30%) after treatment with IL-13 toxin. By Western blot analysis, cleavage of caspase-3 and PARP was observed after treatment with a high concentration of IL-13 toxin, also suggesting apoptotic cell death. In addition, the results of immunofluorescence and RT-PCR assays showed that the apoptosis-regulator, Bcl-2 was downregulated after treatment with IL-13 toxin, while Bax was upregulated. Moreover, significant nitrite production was detected in the HN12 cell line after treatment with IL-13 toxin for 48--96 h. Taken together, our results suggest that IL-13 toxin-induced cytotoxicity is at least partially mediated by the apoptosis and nitric oxide pathways. This information may be useful in developing specific approaches where apoptotic bodies from tumor cells may be used to pulse antigen-presenting cells for immunotherapy of cancer.
authors.affiliation: Laboratory of Molecular Tumor Biology, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, NIH Building 29B, Room 2NN10, 29 Lincoln Drive MSC 4555, 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: D017209:Apoptosis / Q000187:drug effects*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D018793:Interleukin-13 / Q000494:pharmacology*; D053661:Interleukin-13 Receptor alpha1 Subunit; D009569:Nitric Oxide / Q000096:biosynthesis; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D018123:Receptors, Interleukin / Q000187:drug effects*; D053660:Receptors, Interleukin-13; D011993:Recombinant Fusion Proteins / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: C508181:IL13RA1 protein, human; D018793:Interleukin-13; D053661:Interleukin-13 Receptor alpha1 Subunit; D018123:Receptors, Interleukin; D053660:Receptors, Interleukin-13; D011993:Recombinant Fusion Proteins; D009569:Nitric Oxide; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases