Gaedicke Simone, Firat-Geier Elke, Constantiniu Oana, Lucchiari-Hartz Maria, Freudenberg Marina, Galanos Chris, Niedermann Gabriele
Department of Cellular Immunology, Max-Planck Institute of Immunobiology, D-79108 Freiburg, Germany.
Cancer Res. 2002 Dec 1;62(23):6901-8.
Ritonavir is an HIV protease inhibitor used in the therapy of HIV infection. Ritonavir has also been shown to inhibit the chymotrypsin-like activity of isolated 20S proteasomes. Here, we demonstrate that ritonavir, like classical proteasome inhibitors, has antitumoral activities. In vitro, ritonavir strongly reduced the rate of proliferation of several tumor cell lines and induced their apoptosis. Nontransformed cell lines and terminally differentiated bone-marrow macrophages were comparatively resistant to the apoptosis-inducing effect. In vivo, ritonavir, administered p.o. for a week at doses of 6-8.8 mg/mouse/day, caused significant growth inhibition (76-79% after 7 days of treatment) of established EL4-T cell thymomas growing s.c. in syngeneic C57BL/6 mice. Unexpectedly, we found that ritonavir activates the chymotrypsin-like activity of isolated 26S proteasomes, in strong contrast to its effect on isolated 20S proteasomes. The net effect of low micromolar concentrations of ritonavir on the chymotrypsin-like activity in cells and cell lysates was a weak inhibition, consistent with marginal alterations of polyubiquitinated proteins, marginal alterations in acid-soluble proteolytic peptide levels, and a small accumulation of the tumor suppressor protein p53, in cells treated with ritonavir. In contrast, we found a relatively strong accumulation of the cyclin-dependent kinase inhibitor p21(WAF-1), a sign of deregulation of cell-cycle progression typical for apoptosis induction in transformed cells by classical proteasome inhibitors. We demonstrate that p21 accumulation in the presence of ritonavir is attributable to the inhibition of proteolytic degradation. Accumulation of p21 most likely reflects a selective inhibition of proteasomes, in line with the atypical degradation of p21, which does not require ubiquitination. These findings suggest that selective perturbation of proteasomal protein degradation may play a role in the antitumoral activities of ritonavir.
利托那韦是一种用于治疗HIV感染的HIV蛋白酶抑制剂。研究还表明，利托那韦可抑制分离的20S蛋白酶体的类胰凝乳蛋白酶活性。在此，我们证明，利托那韦与经典蛋白酶体抑制剂一样，具有抗肿瘤活性。在体外，利托那韦能显著降低多种肿瘤细胞系的增殖速率并诱导其凋亡。未转化的细胞系和终末分化的骨髓巨噬细胞对凋亡诱导作用相对耐药。在体内，利托那韦以6 - 8.8毫克/小鼠/天的剂量口服给药一周，可显著抑制同基因C57BL/6小鼠皮下生长的已建立的EL4 - T细胞胸腺瘤的生长（治疗7天后生长抑制率达76 - 79%）。出乎意料的是，我们发现利托那韦可激活分离的26S蛋白酶体的类胰凝乳蛋白酶活性，这与其对分离的20S蛋白酶体的作用形成强烈对比。低微摩尔浓度的利托那韦对细胞和细胞裂解物中类胰凝乳蛋白酶活性的净效应是微弱抑制，这与多泛素化蛋白的轻微改变、酸溶性蛋白水解肽水平的轻微改变以及利托那韦处理的细胞中肿瘤抑制蛋白p53的少量积累一致。相比之下，我们发现细胞周期蛋白依赖性激酶抑制剂p21（WAF - 1）有相对较强的积累，这是经典蛋白酶体抑制剂诱导转化细胞凋亡时典型的细胞周期进程失调的迹象。我们证明，利托那韦存在时p21的积累归因于蛋白水解降解的抑制。p21的积累很可能反映了蛋白酶体的选择性抑制，这与p21的非典型降解一致，其降解不需要泛素化。这些发现表明，蛋白酶体蛋白降解的选择性扰动可能在利托那韦的抗肿瘤活性中起作用。
