Kudo Daisuke, Rayman Patricia, Horton Claudine, Cathcart Martha K, Bukowski Ronald M, Thornton Mark, Tannenbaum Charles, Finke James H
Department of Immunology, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Cancer Res. 2003 Apr 1;63(7):1676-83.
It is now understood that the genetic plasticity of cancer cells can lead to alterations that confer selective growth advantages to the tumor, some of which play a role in immune escape. A number of mutations veiling tumor cells from host immune defenses have been well characterized but more recent studies suggest that a variety of tumors can also express products that are actually toxic for the immune effectors. A component of this tumor-induced T-cell death has been attributed to receptor-mediated apoptosis. Some tumors, however, synthesize soluble factors that mediate similar effects. In this regard, we previously showed that supernatants from explanted renal cell carcinoma (RCC) tumors sensitized normal T cells to activation induced cell death, and the responsible products had the features of gangliosides. We have also shown that renal tumor lines, including SK-RC-45, induce apoptosis of both Jurkat cells and normal T lymphocytes. Here, we used the ganglioside synthesis inhibitor PPPP to define the role of gangliosides in RCC cell line (SK-RC-45)-mediated T cell and Jurkat cell apoptosis and to elucidate the proapoptotic molecular events by which the glycosphingolipids produce their effects. The ganglioside-synthesizing SK-RC-45 line stimulated the TUNEL (terminal deoxynucleotidyl transferase-mediated nick end labeling) positivity of cocultured T cells by a mechanism that involved decreasing lymphocyte expression levels of Bcl-2 and Bcl-(XL), inducing cytochrome c release from their mitochondria and activating caspases 9 and 3. These proapoptotic events were partially or completely abrogated when tumor cells were pretreated with PPPP for 5 days before the SK-RC-45/T lymphocyte coincubation, a regimen that reduced tumor-associated ganglioside levels by 70-80%. Our results suggest that gangliosides may be key mediators of RCC-induced T-cell apoptosis and imply that they contribute to the T-cell dysfunction in the tumor microenvironment.
现在人们已经认识到，癌细胞的基因可塑性可导致一些改变，这些改变赋予肿瘤选择性生长优势，其中一些在免疫逃逸中发挥作用。许多掩盖肿瘤细胞使其免受宿主免疫防御的突变已得到充分表征，但最近的研究表明，多种肿瘤还可表达对免疫效应器实际上有毒性的产物。这种肿瘤诱导的T细胞死亡的一个组成部分归因于受体介导的凋亡。然而，一些肿瘤会合成介导类似效应的可溶性因子。在这方面，我们之前表明，来自外植肾细胞癌（RCC）肿瘤的上清液使正常T细胞对激活诱导的细胞死亡敏感，并且起作用的产物具有神经节苷脂的特征。我们还表明，包括SK-RC-45在内的肾肿瘤细胞系可诱导Jurkat细胞和正常T淋巴细胞凋亡。在此，我们使用神经节苷脂合成抑制剂PPPP来确定神经节苷脂在RCC细胞系（SK-RC-45）介导的T细胞和Jurkat细胞凋亡中的作用，并阐明糖鞘脂产生其效应的促凋亡分子事件。合成神经节苷脂的SK-RC-45细胞系通过一种机制刺激共培养T细胞的TUNEL（末端脱氧核苷酸转移酶介导的缺口末端标记）阳性，该机制涉及降低淋巴细胞中Bcl-2和Bcl-(XL)的表达水平，诱导细胞色素c从其线粒体释放并激活半胱天冬酶9和3。当在SK-RC-45/T淋巴细胞共孵育前5天将肿瘤细胞用PPPP预处理时，这些促凋亡事件被部分或完全消除，该方案使肿瘤相关神经节苷脂水平降低70-80%。我们的结果表明，神经节苷脂可能是RCC诱导的T细胞凋亡的关键介质，并暗示它们促成肿瘤微环境中的T细胞功能障碍。
