Wang Zhao Yuan, Gaggero Alessia, Rubartelli Anna, Rosso Ombretta, Miotti Silvia, Mezzanzanica Delia, Canevari Silvana, Ferrini Silvano
Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.
Int J Cancer. 2002 Apr 20;98(6):873-8. doi: 10.1002/ijc.10268.
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.
白细胞介素-18（IL-18）是一种促炎单核因子，在结构上与刺激γ干扰素（IFN-γ）产生的IL-1β相关。IL-18以无活性前体即前IL-18的形式合成，前IL-18在成熟蛋白中被IL-1β转换酶（ICE）/半胱天冬酶-1切割。鉴于IL-18在癌症免疫/基因治疗中的应用前景，我们研究了IL-18在肿瘤细胞中的表达。通过逆转录聚合酶链反应在所有检测的人卵巢癌细胞系（9/9）以及从卵巢癌患者获得的一半肿瘤细胞群体（4/8）中检测到了IL-18 mRNA。ICE mRNA在较少比例的样本中表达（3/9个细胞系和3/8个患者样本）。通过免疫组织化学分析在13个卵巢癌实体瘤中的7个中也发现了IL-18蛋白。在肿瘤细胞系中，我们能够通过蛋白质印迹法检测到丰富的细胞内前IL-18（24 kDa），而无论ICE mRNA和蛋白是否存在，均未检测到成熟形式的IL-18。在卵巢癌细胞上清液中也仅发现了前IL-18，其在功能测定中未显示任何IL-18生物活性。正常培养的卵巢上皮细胞在所有样本（5/5）中均显示存在IL-18和ICE mRNA，并且围绕正常卵巢的薄上皮细胞层表达IL-18蛋白。更重要的是，正常卵巢上皮细胞在培养上清液中释放出少量但可检测到的成熟IL-18，其在功能测定中显示出IL-18样生物活性。这些数据表明，成熟的具有生物活性的IL-18的产生是正常卵巢表面上皮在肿瘤转化过程中丧失的一个特征。
