title: Soluble human MDA-7/IL-24: characterization of the molecular form(s) inhibiting tumor growth and stimulating monocytes.
abstract: Interleukin-24 (IL-24), also known as melanoma differentiation-associated gene-7 (mda-7), is a member of the IL-10 family that exhibits both tumor suppressor and proinflammatory properties. We describe the purification of this novel dual-function tumor suppressor/cytokine from the supernatant of IL-24 gene-transfected HEK 293 cells and define the biochemical and functional properties of the soluble human IL-24 protein. Size exclusion chromatography demonstrates that an IL-24 macromolecular complex fractionates in a broad peak with a median of 110 kDa and comprises several IL-24 isoforms, identified by immunoblotting with anti-IL-24 polyclonal antibody after reducing SDS-PAGE analysis. IL-24 was found to associate with two serum components, albumin and C1q. Cation exchange purification results in the isolation of at least two N-linked glycosylated IL-24 dimers covalently associated via intermolecular disulfide bonds. These molecularly defined N-glycosylated IL-24 dimers elicited dose-dependent secretion of tumor necrosis factor-alpha (TNF-alpha) and IL-6 from human monocytes, as well as cytotoxicity to human melanoma cell lines. Thus, we demonstrated that the secreted, glycosylated, dimeric, human IL-24 is immunomodulatory to monocytes and exhibits tumor cell growth inhibition.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas, M.D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Mumm
authors.forename: Suhendan
authors.initials: S
authors.lastname: Ekmekcioglu
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Poindexter
authors.forename: Sunil
authors.initials: S
authors.lastname: Chada
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Grimm
mesh_terms: D000276:Adjuvants, Immunologic / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology*; D000418:Albumins / Q000302:isolation & purification; D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002852:Chromatography, Ion Exchange; D019281:Dimerization; D006031:Glycosylation; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D007378:Interleukins / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology*; D008545:Melanoma / Q000276:immunology*; D009000:Monocytes / Q000187:drug effects* / Q000276:immunology; D020033:Protein Isoforms / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000099180:Interleukin-24
chemical_list: D000276:Adjuvants, Immunologic; D000418:Albumins; D015850:Interleukin-6; D007378:Interleukins; D020033:Protein Isoforms; D014409:Tumor Necrosis Factor-alpha; D000099180:Interleukin-24