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- Title
A novel isoform of pro-interleukin-18 expressed in ovarian tumors is resistant to caspase-1 and -4 processing.
- Authors
Gaggero, Alessia; Ambrosis, Alessandro De; Mezzanzanica, Delia; Piazza, Tiziana; Rubartelli, Anna; Figini, Mariangela; Canevari, Silvana; Ferrini, Silvano
- Abstract
Interleukin-18 (IL-18) is a proinflammatory cytokine synthesized as a 24?kDa inactive precursor (pro-IL-18) by several cell types, and is processed to a bioactive molecule of 18?kDa by the proteinases caspase-1 or caspase-4. All ovarian carcinoma cell lines express pro-IL-18, only in some instances coexpress caspase-1, and always express caspase-4; in any case, they display a defective processing of IL-18. We analysed whether pro-IL-18, present in two ovarian carcinoma cell lysates, could be processed‘in vitro’by recombinant active caspase-1. While most of pro-IL-18 could be cleaved by caspase-1, a residual of pro-IL-18 appeared to be resistant. Cloning and sequence analysis of the whole pro-IL-18 open reading frame demonstrated the existence of an alternatively spliced mRNA variant, which lacked exon-3 (?3pro-IL-18). The 12?bp exon-3 encodes for the AEDD amino-acid sequence, which is N-terminal with respect to the cleavage site of caspase-1. Both pro-IL-18 and?3pro-IL-18 mRNA isoforms were detected in all ovarian cancer cell lines analysed, while?3pro-IL-18 mRNA was undetectable in normal ovarian epithelial cells. The?3pro-IL-18 cDNA induced synthesis of an alternative?3pro-IL-18 protein upon transfection into a murine cell line. The?3pro-IL-18 protein was resistant to proteolytic activation by caspase-1 and -4, although it was capable to bind caspase-1. Aternative splicing of pro-IL-18 exon-3 may represent a novel mechanism of regulation of bioactive IL-18 production in human ovarian tumors.Oncogene (2004) 23, 7552-7560. doi:10.1038/sj.onc.1208036 Published online 23 August 2004
- Subjects
OVARIAN tumors; INTERLEUKINS; GROWTH factors; CYTOKINES; IMMUNOREGULATION; CANCER cells; CELL lines
- Publication
Oncogene, 2004, Vol 23, Issue 45, p7552
- ISSN
0950-9232
- Publication type
Article
- DOI
10.1038/sj.onc.1208036