Schumacher Y, Aparicio T, Ourabah S, Baraille F, Martin A, Wind P, Dentin R, Postic C, Guilmeau S
Inserm U1016, Institut Cochin, Paris, France.
CNRS UMR 8104, Paris, France.
Oncogene. 2016 May 19;35(20):2602-14. doi: 10.1038/onc.2015.283. Epub 2015 Aug 24.
First identified as a dedicated CREB (cAMP response element-binding protein) co-activator, CRTC1 (CREB-regulated transcription co-activator 1) has been widely implicated in various neuronal functions because of its predominant expression in the brain. However, recent evidences converge to indicate that CRTC1 is aberrantly activated in an expanding number of adult malignancies. In this study, we provide strong evidences of enhanced CRTC1 protein content and transcriptional activity in mouse models of sporadic (APC(min/+) mice) or colitis-associated colon cancer azoxymethane/dextran sulfate sodium (AOM/DSS-treated mice), and in human colorectal tumors specimens compared with adjacent normal mucosa. Among signals that could trigger CRTC1 activation during colonic carcinogenesis, we demonstrate that treatment with cyclooxygenase 2 (COX2) inhibitors reduced nuclear CRTC1 active form levels in colonic tumors of APC(min/+) or AOM/DSS mice. In accordance, prostaglandins E2 (PGE2) exposure to human colon cancer cell lines promoted CRTC1 dephosphorylation and parallel nuclear translocation, resulting in enhanced CRTC1 transcriptional activity, through EP1 and EP2 receptors signaling and consecutive calcineurin and protein kinase A activation. In vitro CRTC1 loss of function in colon cancer cell lines was associated with reduced viability and cell division rate as well as enhanced chemotherapy-induced apoptosis on PGE2 treatment. Conversely, CRTC1 stable overexpression significantly increased colonic xenografts tumor growth, therefore demonstrating the role of CRTC1 signaling in colon cancer progression. Identification of the transcriptional program triggered by enhanced CRTC1 expression during colonic carcinogenesis, revealed some notable pro-tumorigenic CRTC1 target genes including NR4A2, COX2, amphiregulin (AREG) and IL-6. Finally, we demonstrate that COX2, AREG and IL-6 promoter activities triggered by CRTC1 are dependent on functional AP1 and CREB transcriptional partners. Overall, our study establishes CRTC1 as new mediator of PGE2 signaling, unravels the importance of its dysregulation in colon cancer and strengthens its use as a bona fide cancer marker.
CRTC1（CREB调节的转录共激活因子1）最初被鉴定为一种专门的CREB（环磷酸腺苷反应元件结合蛋白）共激活因子，因其在大脑中大量表达而广泛参与各种神经元功能。然而，最近的证据表明，CRTC1在越来越多的成人恶性肿瘤中被异常激活。在本研究中，我们提供了强有力的证据，表明在散发性（APC(min/+)小鼠）或结肠炎相关结肠癌（氧化偶氮甲烷/葡聚糖硫酸钠处理的小鼠）的小鼠模型中，以及与相邻正常黏膜相比的人类结直肠癌标本中，CRTC1蛋白含量和转录活性增强。在结肠癌变过程中可能触发CRTC1激活的信号中，我们证明用环氧合酶2（COX2）抑制剂处理可降低APC(min/+)或AOM/DSS小鼠结肠肿瘤中核CRTC1活性形式的水平。相应地，前列腺素E2（PGE2）作用于人类结肠癌细胞系可促进CRTC1去磷酸化和平行的核转位，通过EP1和EP2受体信号传导以及连续的钙调神经磷酸酶和蛋白激酶A激活，导致CRTC1转录活性增强。结肠癌细胞系中CRTC1的体外功能丧失与活力和细胞分裂率降低以及PGE2处理后化疗诱导的凋亡增强有关。相反，CRTC1的稳定过表达显著增加结肠异种移植瘤的生长，因此证明了CRTC1信号传导在结肠癌进展中的作用。对结肠癌变过程中CRTC1表达增强所触发的转录程序的鉴定，揭示了一些显著的促肿瘤CRTC1靶基因，包括NR4A2、COX2、双调蛋白（AREG）和IL-6。最后，我们证明CRTC1触发的COX2、AREG和IL-6启动子活性依赖于功能性AP1和CREB转录伙伴。总体而言，我们的研究将CRTC1确立为PGE2信号传导的新介质，揭示了其失调在结肠癌中的重要性，并加强了其作为真正癌症标志物的确立。
