Restoration of transforming growth factor-β signaling enhances radiosensitivity by altering the Bcl-2/Bax ratio in the p53 mutant pancreatic cancer cell line MIA PaCa-2
Restoration of transforming growth factor-β signaling enhances radiosensitivity by altering the Bcl-2/Bax ratio in the p53 mutant pancreatic cancer cell line MIA PaCa-2
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DOI：
10.1074/jbc.m110168200
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发表时间：
2002-01-18
影响因子：
4.8
通讯作者：
Freeman, JW
中科院分区：
文献类型：
--
作者：
Ahmed, MM;Alcock, A;Freeman, JW
在这项研究中，我们研究了转化生长因子β（TGF-β）II型受体（RII）表达的缺乏和TGF-β信号转导的丢失是否在具有突变的p53基因的胰腺癌细胞MIA PaCa-2的辐射抗性中发挥作用。用RII cDNA转染该细胞系导致对TGF-β响应性报告构建体p3 TP-Lux的转录活性的刺激。与MIA PaCa-2/载体细胞相比，RII转染子（MIA PaCa-2/RII）显示对辐射的敏感性显著增加。对辐射敏感性的增加被TGF-β的中和抗体逆转，表明这些变化依赖于TGF-β信号传导。与MIA PaCa-2/vector细胞相比，MIA PaCa-2/RII细胞在辐射后显示出大于3倍的凋亡增加。MIA PaCa-2/RII细胞的辐射敏感性增强与Bax mRNA和蛋白的诱导相关，随后是细胞色素c的释放和caspase-3和聚（ADPribose）聚合酶裂解的激活。过表达Bcl-x（L）或用靶向Bax的反义寡脱氧核苷酸处理显著抑制MIA PaCa-2/RII中辐射诱导的凋亡，但在MIA PaCa-2/Vector细胞中不抑制，表明Bax诱导对于辐射诱导的TGF-β信号介导的凋亡是必需的。因此，TGF-β信号的恢复使这些细胞对电离辐射敏感，尽管这些细胞具有突变的p53基因。此外，RII显性失活突变体对RII功能的破坏抑制了小鼠胚胎成纤维细胞原代培养物中辐射诱导的TGF-β信号传导和凋亡。总之，这些观察结果意味着RII是辐射诱导的TGF-β信号传导的重要组成部分，并且RII功能的丧失可以增强对辐射诱导的细胞凋亡的抗性。
In this study, we investigated whether lack of transforming growth factor beta (TGF-beta) type II receptor (RII) expression and loss of TGF-beta signaling played a role in radiation resistance of pancreatic cancer cells MIA PaCa-2 that possess a mutated p53 gene. Transfection of this cell line with a RII cDNA led to a stimulation of the transcriptional activity of p3TP-Lux, a TGF-beta-responsive reporter construct. The RII transfectants (MIA PaCa-2/RII) showed a significant increase in sensitivity to radiation when compared with MIA PaCa-2/vector cells. The increase in sensitivity to radiation was reversed by neutralizing antibodies to TGF-beta, indicating that these changes were dependent on TGF-beta signaling. Compared with MIA PaCa-2/vector cells, MIA PaCa-2/RII cells showed a greater than 3-fold increase in apoptosis after radiation. Enhanced radiation sensitivity of MIA PaCa-2/RII cells was associated with an induction of Bax mRNA and protein that was followed by a release of cytochrome c and activation of caspase-3 and poly(ADPribose) polymerase cleavage after radiation exposure. Overexpression of Bcl-x(L) or treatment with antisense oligodeoxynucleotides targeted against Bax significantly inhibited radiation-induced apoptosis in MIA PaCa-2/RII but not in MIA PaCa-2/Vector cells, suggesting that Bax induction is necessary for radiation-induced TGF-beta signaling-mediated apoptosis. Thus, restoration of TGF-beta signaling sensitized these cells to ionizing radiation, although these cells possess a mutated p53 gene. In addition, disruption of RII function by dominant negative mutant of RII inhibited the radiation-induced TGF-beta signaling and apoptosis in primary cultures of mouse embryonic fibroblasts. Together these observations imply that RII is an important component of radiation-induced TGF-beta signaling, and loss of function of RII may enhance resistance to radiation-induced apoptosis.