Yan Y, Mahotka C, Heikaus S, Shibata T, Wethkamp N, Liebmann J, Suschek C V, Guo Y, Gabbert H E, Gerharz C D, Ramp U
Institute of Pathology, University Hospital, Duesseldorf, Germany.
Br J Cancer. 2004 Oct 4;91(7):1349-57. doi: 10.1038/sj.bjc.6602127.
Dysregulation of apoptosis plays an important role in tumour progression and resistance to chemotherapy. The X-linked inhibitor of apoptosis (XIAP) is considered to be the most potent caspase inhibitor of all known inhibitor of apoptosis-family members. Only recently, an antagonist of XIAP has been identified, termed Smac/DIABLO. To explore the relevance of antiapoptotic XIAP and proapoptotic Smac/DIABLO for tumour progression in renal cell carcinomas (RCCs), we analysed XIAP and Smac/DIABLO mRNA and protein expression in the primary tumour tissue from 66 RCCs of all major histological types by quantitative real-time PCR, Western blot and ELISA. X-linked inhibitor of apoptosis and Smac/DIABLO mRNA expression was found in all RCCs. Importantly, the relative XIAP mRNA expression levels significantly increased from early (pT1) to advanced (pT3) tumour stages (P=0.0002) and also with tumour dedifferentiation (P=0.04). Western blot analysis confirmed the tumour stage-dependent increase of XIAP expression on the protein level. In contrast, mRNA and protein expression levels of Smac/DIABLO did not significantly change between early and advanced tumour stages or between low and high tumour grades. Consequently, the mRNA expression ratio between antiapoptotic XIAP and proapoptotic Smac/DIABLO markedly increased during progression from early (pT1) to advanced (pT3) tumour stages. Moreover, RCCs confined within the organ capsule (pT1 and pT2) exhibited a significantly lower XIAP to Smac/DIABLO expression ratio when compared with RCCs infiltrating beyond the kidney (pT3; P=0.01). Thus, our investigation demonstrates that the delicate balance between XIAP and Smac/DIABLO expression is gradually disturbed during progression of RCCs, resulting in a relative increase of antiapoptotic XIAP over proapoptotic Smac/DIABLO, thereby probably contributing to the marked apoptosis resistance of RCC.
细胞凋亡失调在肿瘤进展和化疗耐药中起重要作用。X连锁凋亡抑制蛋白（XIAP）被认为是所有已知凋亡抑制蛋白家族成员中最有效的半胱天冬酶抑制剂。直到最近，才鉴定出一种XIAP拮抗剂，称为Smac/DIABLO。为了探究抗凋亡的XIAP和促凋亡的Smac/DIABLO与肾细胞癌（RCC）肿瘤进展的相关性，我们通过定量实时PCR、蛋白质印迹法和酶联免疫吸附测定法，分析了66例所有主要组织学类型的RCC原发肿瘤组织中XIAP和Smac/DIABLO的mRNA和蛋白质表达。在所有RCC中均发现了X连锁凋亡抑制蛋白和Smac/DIABLO的mRNA表达。重要的是，XIAP mRNA相对表达水平从早期（pT1）肿瘤阶段到晚期（pT3）肿瘤阶段显著升高（P=0.0002），并且也随着肿瘤去分化而升高（P=0.04）。蛋白质印迹分析证实了XIAP表达在蛋白质水平上随肿瘤阶段的增加。相比之下，Smac/DIABLO的mRNA和蛋白质表达水平在早期和晚期肿瘤阶段之间或低级别和高级别肿瘤之间没有显著变化。因此，在从早期（pT1）到晚期（pT3）肿瘤阶段的进展过程中，抗凋亡的XIAP与促凋亡的Smac/DIABLO之间的mRNA表达比率显著增加。此外，与浸润至肾外的RCC（pT3；P=0.01）相比，局限于器官包膜内的RCC（pT1和pT2）的XIAP与Smac/DIABLO表达比率显著更低。因此，我们的研究表明，在RCC进展过程中，XIAP和Smac/DIABLO表达之间的微妙平衡逐渐被打破，导致抗凋亡的XIAP相对于促凋亡的Smac/DIABLO相对增加，从而可能导致RCC显著的凋亡抗性。
