Renner G, Janouskova H, Noulet F, Koenig V, Guerin E, Bär S, Nuesch J, Rechenmacher F, Neubauer S, Kessler H, Blandin A-F, Choulier L, Etienne-Selloum N, Lehmann M, Lelong-Rebel I, Martin S, Dontenwill M
Integrins and Cancer, Faculté de Pharmacie, UMR7213 CNRS, LBP, Tumoral Signaling and Therapeutic Targets Department, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France.
EA3430, Université de Strasbourg, Strasbourg, France.
Cell Death Differ. 2016 Apr;23(4):640-53. doi: 10.1038/cdd.2015.131. Epub 2015 Oct 16.
Integrin α5β1 expression is correlated with a worse prognosis in high-grade glioma. We previously unraveled a negative crosstalk between integrin α5β1 and p53 pathway, which was proposed to be part of the resistance of glioblastoma to chemotherapies. The restoration of p53 tumor-suppressor function is under intensive investigations for cancer therapy. However, p53-dependent apoptosis is not always achieved by p53-reactivating compounds such as Nutlin-3a, although full transcriptional activity of p53 could be obtained. Here we investigated whether integrin α5β1 functional inhibition or repression could sensitize glioma cells to Nutlin-3a-induced p53-dependent apoptosis. We discovered that α5β1 integrin-specific blocking antibodies or small RGD-like antagonists in association with Nutlin-3a triggered a caspase (Casp) 8/Casp 3-dependent strong apoptosis in glioma cells expressing a functional p53. We deciphered the molecular mechanisms involved and we showed the crucial role of two anti-apoptotic proteins, phosphoprotein enriched in astrocytes 15 (PEA-15) and survivin in glioma cell apoptotic outcome. PEA-15 is under α5β1 integrin/AKT (protein kinase B) control and survivin is a p53-repressed target. Moreover, interconnections between integrin and p53 pathways were revealed. Indeed PEA-15 repression by specific small-interfering RNA (siRNA)-activated p53 pathway to repress survivin and conversely survivin repression by specific siRNA decreased α5β1 integrin expression. This pro-apoptotic loop could be generalized to several glioma cell lines, whatever their p53 status, inasmuch PEA-15 and survivin protein levels were decreased. Our findings identify a novel mechanism whereby inhibition of α5β1 integrin and activation of p53 modulates two anti-apoptotic proteins crucially involved in the apoptotic answer of glioma cells. Importantly, our results suggest that high-grade glioma expressing high level of α5β1 integrin may benefit from associated therapies including integrin antagonists and repressors of survivin expression.
整合素α5β1的表达与高级别胶质瘤的预后较差相关。我们之前揭示了整合素α5β1与p53通路之间的负性相互作用，这被认为是胶质母细胞瘤对化疗产生耐药性的部分原因。恢复p53肿瘤抑制功能是癌症治疗领域正在深入研究的内容。然而，尽管可以获得p53的完全转录活性，但p53激活化合物（如Nutlin-3a）并不总能实现p53依赖的细胞凋亡。在此，我们研究了整合素α5β1的功能抑制或表达抑制是否能使胶质瘤细胞对Nutlin-3a诱导的p53依赖的细胞凋亡敏感。我们发现，α5β1整合素特异性阻断抗体或小的类RGD拮抗剂与Nutlin-3a联合使用时，可在表达功能性p53的胶质瘤细胞中引发半胱天冬酶（Casp）8/Casp 3依赖的强烈细胞凋亡。我们解析了其中涉及的分子机制，并表明两种抗凋亡蛋白，即星形胶质细胞富集磷酸蛋白15（PEA-15）和生存素在胶质瘤细胞凋亡结果中起关键作用。PEA-15受α5β1整合素/AKT（蛋白激酶B）调控，生存素是一个受p53抑制的靶点。此外，还揭示了整合素与p53通路之间的相互联系。事实上，特异性小干扰RNA（siRNA）对PEA-15的抑制激活了p53通路，从而抑制生存素；相反，特异性siRNA对生存素的抑制降低了α5β1整合素的表达。无论胶质瘤细胞系的p53状态如何，这种促凋亡环均可推广至多种胶质瘤细胞系，因为PEA-15和生存素的蛋白水平均降低。我们的研究结果确定了一种新机制，即抑制α5β1整合素和激活p53可调节两种抗凋亡蛋白，这两种蛋白在胶质瘤细胞的凋亡反应中起关键作用。重要的是，我们的结果表明，高表达α5β1整合素的高级别胶质瘤可能受益于包括整合素拮抗剂和生存素表达抑制剂在内的联合治疗。
