CD47 mediates killing of breast tumor cells via Gi-dependent inhibition of protein kinase A
CD47 mediates killing of breast tumor cells via Gi-dependent inhibition of protein kinase A
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DOI：
10.1158/0008-5472.can-03-1708
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发表时间：
2004-02-01
期刊：
影响因子：
11.2
通讯作者：
Frazier, WA
中科院分区：
文献类型：
--
作者：
Manna, PP;Frazier, WA
血栓反应蛋白（tsp）被认为是乳腺癌的抗肿瘤和抗转移因子。虽然这种作用归因于tsp的抗血管生成活性，但最近的观察表明，其他机制可能也在起作用。TSP受体CD47（整合素相关蛋白）最近被报道介导一种新的细胞凋亡形式。在这里，我们研究了乳腺癌细胞对CD47配体TSP-1、由TSP-1衍生的CD47激动剂肽4N1K和抗CD47单克隆抗体1F7的反应。所有这些配体杀死了四种不同的乳腺癌细胞系。这种cd47介导的细胞死亡不需要活性半胱天冬酶或Bcl-2降解，也不引起DNA阶梯或细胞色素c释放。百日咳毒素（PTX）阻止cd47介导的死亡，表明Gialpha. 4N1K的参与显著降低了细胞内cAMP水平，PTX逆转了这一作用。福斯克林、8-溴cAMP和异丁基甲基黄嘌呤（IBMX）均能阻止cd47介导的细胞凋亡，表明cAMP参与其中。H89和蛋白激酶A （PKA）抑制剂肽阻止PTX、8-Br-cAMP和forskolin对乳腺癌细胞的拯救，表明cAMP的作用是通过PKA依赖性磷酸化事件介导的。表皮生长因子也通过pkc依赖而erk独立的途径抑制cd47诱导的细胞凋亡。因此，cd47介导的乳腺癌细胞杀伤是通过异源三聚体Gi调控cAMP水平的新途径发生的，随后的效应由PKA介导。
Thrombospondins (TSPs) have been implicated as antitumor and antimetastasis factors in breast cancer. Although this effect has been attributed to the antiangiogenic activity of TSPs, recent observations suggest other mechanisms may be at work. The TSP receptor CD47 (integrin-associated protein) has recently been reported to mediate a novel form of apoptosis. Here, we have studied the response of breast cancer cells to CD47 ligands TSP-1, the CD47 agonist peptide 4N1K derived from TSP-1, and the anti-CD47 monoclonal antibody 1F7. All of these ligands killed four different breast cancer cell lines. This CD47-mediated cell death did not require active caspases or Bcl-2 degradation and did not cause DNA laddering or cytochrome c release. Pertussis toxin (PTX) prevented CD47-mediated death, indicating the involvement of Gialpha. 4N1K dramatically reduced intracellular cAMP levels, an effect reversed with PTX. Forskolin, 8-bromo cAMP, and isobutylmethylxanthine (IBMX) all prevented CD47-mediated apoptosis, indicating the involvement of cAMP. H89 and protein kinase A (PKA) inhibitor peptide prevented rescue of breast cancer cells by PTX, 8-Br-cAMP, and forskolin, suggesting that the effects of cAMP are mediated via PKA-dependent phosphorylation events. Epidermal growth factor also inhibited CD47-induced apoptosis via a PKC-dependent but ERK-independent pathway. Thus, CD47-mediated killing of breast cancer cells occurs by a novel pathway involving regulation of cAMP levels by heterotrimeric Gi with subsequent effects mediated by PKA.