Expression of interleukin-18 in human ovarian carcinoma and normal ovarian epithelium: evidence for defective processing in tumor cells.
Interleukin-18 (IL-18) is a proinflammatory monokine structurally related to IL-1beta that stimulates interferon-gamma (IFN-gamma) production. IL-18 is synthesized as an inactive precursor, pro-IL-18, which is cleaved by IL-1beta-converting enzyme (ICE)/caspase-1 in a mature protein. In view of the proposed use of IL-18 in cancer immuno/gene therapy, we have studied the expression of IL-18 in tumor cells. IL-18 mRNA was detected by reverse transcriptase polymerase chain reaction in all human ovarian carcinoma cell lines tested (9/9) and in one-half of tumor cell populations obtained from ovarian carcinoma patients (4/8). ICE mRNA was expressed in a smaller fraction of samples (3/9 cell lines and 3/8 samples from patients). IL-18 protein was also found in 7/13 ovarian carcinoma solid tumors by immunohistochemic analysis. In tumor cell lines we were able to detect abundant intracellular pro-IL-18 (24 kDa) by Western blotting, whereas the mature form of IL-18 was undetectable, irrespective of the presence of ICE mRNA and protein. Only pro-IL-18 was also found in the ovarian carcinoma cell supernatants, which did not display any IL-18 biologic activity in functional assays. Normal cultured ovarian epithelial cells revealed the presence of both IL-18 and ICE mRNA in all samples (5/5) and IL-18 protein was expressed by the thin epithelial cell layer surrounding normal ovary. More importantly, normal ovarian epithelial cells released low but detectable amounts of mature IL-18 in the culture supernatant, which displayed IL-18-like biologic activity in functional assays. These data suggest that mature biologically active IL-18 production is a feature of the normal ovarian surface epithelium lost during neoplastic transformation.
Wang
Zhao Yuan
ZY
Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.
Gaggero
Alessia
A
Rubartelli
Anna
A
Rosso
Ombretta
O
Miotti
Silvia
S
Mezzanzanica
Delia
D
Canevari
Silvana
S
Ferrini
Silvano
S
D015153:Blotting, Western; D018269:Carcinoma, Endometrioid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020170:Caspase 1 / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D018284:Cystadenocarcinoma, Serous / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D017931:DNA Primers / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D020382:Interleukin-18 / Q000235:genetics / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010053:Ovary / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D020382:Interleukin-18; D012333:RNA, Messenger; D020170:Caspase 1