title: Internalization property of interleukin-4 receptor alpha chain increases cytotoxic effect of interleukin-4 receptor-targeted cytotoxin in cancer cells.
abstract: Although the receptor for interleukin-4 (IL-4R) is highly expressed on solid human cancer cells, its significance and internalization function is still unclear. To address these issues, we reconstituted Chinese hamster ovarian (CHO-K1) cells with various components of the IL-4R by transient transfection and performed internalization assays using radiolabeled IL-4. Radiolabeled IL-4 internalized through the IL-4Ralpha chain in a time-dependent manner. When the IL-4Ralpha chain was cotransfected with the IL-13Ralpha1 or -gamma(c) chain, the IL-4 internalization level was identical to IL-4Ralpha transfectants, suggesting that the IL-4Ralpha chain plays a major role in IL-4 internalization. These results were confirmed by determining the cytotoxicity of a chimeric protein composed of IL-4 and a mutated form of Pseudomonas exotoxin [IL4(38-37)-PE38KDEL] in CHO-K1 cells transfected with increasing concentrations of IL-4Ralpha cDNA. To use the internalization property of the IL-4Ralpha chain in the context of IL-4R-targeted cytotoxin therapy, we transiently transfected pancreatic and brain tumor cells with IL-4Ralpha chain. Surprisingly, these tumor cells acquired 4-75-fold higher binding activity to IL-4 compared with control cells. Consequently, the cytotoxic activity of IL-4 toxin to these cancer cells was enhanced 5-13-fold compared with control cells as assessed by protein synthesis inhibition and clonogenic assays. Taken together, a combination approach that involves transfer of the IL-4Ralpha gene and IL-4R-targeted cytotoxin therapy may serve as a novel approach for cancer 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, Maryland 20892, USA.
authors.forename: Koji
authors.initials: K
authors.lastname: Kawakami
authors.forename: Mariko
authors.initials: M
authors.lastname: Kawakami
authors.forename: Pamela
authors.initials: P
authors.lastname: Leland
authors.forename: Raj K
authors.initials: RK
authors.lastname: Puri
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D003603:Cytotoxins / Q000494:pharmacology*; D004705:Endocytosis; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D000922:Immunotoxins / Q000494:pharmacology*; D015847:Interleukin-4 / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000378:metabolism; D011869:Radioligand Assay; D019948:Receptors, Interleukin-4 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000378:metabolism
chemical_list: D003603:Cytotoxins; D000922:Immunotoxins; D011500:Protein Synthesis Inhibitors; D019948:Receptors, Interleukin-4; C120228:interleukin 4 (38-37)-PE38KDEL; D015847:Interleukin-4