Mitsiades Constantine S, Poulaki Vassiliki, Fanourakis Galinos, Sozopoulos Elias, McMillin Douglas, Wen Zhaoqin, Voutsinas Gerassimos, Tseleni-Balafouta Sophia, Mitsiades Nicholas
Department of Medical Oncology, Dana-Farber Cancer Institute, Room M555, Mayer Building, 44 Binney Street, Boston, MA 02115, USA.
Clin Cancer Res. 2006 Jun 15;12(12):3705-12. doi: 10.1158/1078-0432.CCR-05-2493.
The death receptor Fas is present in thyroid carcinomas, yet fails to trigger apoptosis. Interestingly, Fas has been reported to be actually overexpressed in papillary thyroid carcinomas, suggesting that it may confer a survival advantage.
We investigated the expression and activation status of Fas pathway mediators in thyroid carcinoma cell lines and tumor specimens.
All cell lines tested express Fas-associated death domain, procaspase-8, procaspase-9, and procaspase-3; resistance to Fas-mediated apoptosis could not be attributed to lack of any of these apoptosis mediators. Moreover, Fas death domain mutations were not found in our study. The proteasome inhibitors MG132 and PS-341 (bortezomib, Velcade), which lead to accumulation of the nuclear factor kappaB (NF-kappaB) inhibitor IkappaB, did not sensitize SW579 cells to Fas-mediated apoptosis, suggesting that resistance to Fas-mediated apoptosis is not due to proteasome or NF-kappaB activity. Cross-linking of Fas in vitro induced recruitment of Fas-associated death domain-like interleukin-1beta-converting enzyme inhibitory protein (FLIP) instead of procaspase-8. Inhibition of FLIP expression with a FLIP antisense oligonucleotide resulted in significant sensitization to Fas-mediated apoptosis. Fas cross-linking promoted BrdUrd incorporation; activated the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase, NF-kappaB, and activator protein-1 pathways in thyroid carcinoma cells in vitro; and protected cells from tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. We also found that good prognosis papillary thyroid carcinoma specimens exhibited higher immunoreactivity for cleaved (activated) caspase-8 than poor prognosis tumors.
In thyroid carcinomas, the proteolytic cleavage and activation of caspase-8 depends on the balance between expression levels for procaspase-8 and FLIP and correlates with favorable clinical prognosis. Fas may actually stimulate proliferation and confer a survival advantage to thyroid cancer cells.
死亡受体Fas存在于甲状腺癌中，但未能触发细胞凋亡。有趣的是，据报道Fas在甲状腺乳头状癌中实际上是过表达的，这表明它可能赋予生存优势。
我们研究了甲状腺癌细胞系和肿瘤标本中Fas通路介质的表达和激活状态。
所有测试的细胞系均表达Fas相关死亡结构域、procaspase-8、procaspase-9和procaspase-3；对Fas介导的细胞凋亡的抗性不能归因于缺乏这些凋亡介质中的任何一种。此外，在我们的研究中未发现Fas死亡结构域突变。蛋白酶体抑制剂MG132和PS-341（硼替佐米，万珂）可导致核因子κB（NF-κB）抑制剂IkappaB积累，但并未使SW579细胞对Fas介导的细胞凋亡敏感，这表明对Fas介导的细胞凋亡的抗性并非由于蛋白酶体或NF-κB活性。体外Fas交联诱导Fas相关死亡结构域样白细胞介素-1β转化酶抑制蛋白（FLIP）而非procaspase-8的募集。用FLIP反义寡核苷酸抑制FLIP表达导致对Fas介导的细胞凋亡显著敏感。Fas交联促进BrdUrd掺入；在体外激活甲状腺癌细胞中的丝裂原活化蛋白激酶/细胞外信号调节激酶激酶/细胞外信号调节激酶、NF-κB和活化蛋白-1通路；并保护细胞免受肿瘤坏死因子相关凋亡诱导配体诱导的细胞凋亡。我们还发现，预后良好的甲状腺乳头状癌标本比预后不良的肿瘤对裂解（活化）的caspase-8表现出更高的免疫反应性。
在甲状腺癌中，caspase-8的蛋白水解切割和激活取决于procaspase-8和FLIP表达水平之间的平衡，并与良好的临床预后相关。Fas实际上可能刺激甲状腺癌细胞增殖并赋予其生存优势。
