CREB1 directly activates the transcription of ribonucleotide reductase small subunit M2 and promotes the aggressiveness of human colorectal cancer

// Zejun Fang 1 , Aifen Lin 2 , Jiaoe Chen 1 , Xiaomin Zhang 1 , Hong Liu 3 , Hongzhang Li 1 , Yanyan Hu 1 , Xia Zhang 2 , Jiangang Zhang 2 , Lanlan Qiu 1 , Lingming Mei 1 , Jimin Shao 4 , Xiang Chen 1 1 Central Laboratory, Sanmen People’s Hospital of Zhejiang, Sanmen, Zhejiang, 317100, China 2 Human Tissue Bank, Taizhou Hospital of Zhejiang Province, Wenzhou Medical University, Linhai, Zhejiang, 317000, China 3 Zhejiang Normal University - Jinhua People’s Hospital Joint Center for Biomedical Research, Jinhua, Zhejiang, 321004, China 4 Department of Pathology and Pathophysiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China Correspondence to: Xiang Chen, email: sychenxiang@126.com Jimin Shao, email: shaojimin@zju.edu.cn Keywords: CREB1, ribonucleotide reductase small subunit M2, aggressiveness, colorectal cancer Received: March 16, 2016 Accepted: October 17, 2016 Published: October 27, 2016 ABSTRACT As the small subunit of Ribonucleotide reductase (RR), RRM2 displays a very important role in various critical cellular processes such as cell proliferation, DNA repair, and senescence, etc. Importantly, RRM2 functions like a tumor driver in most types of cancer but little is known about the regulatory mechanism of RRM2 in cancer development. In this study, we found that the cAMP responsive element binding protein 1 (CREB1) acted as a transcription factor of RRM2 gene in human colorectal cancer (CRC). CREB1 directly bound to the promoter of RRM2 gene and induced its transcriptional activation. Knockdown of CREB1 decreased the expression of RRM2 at both mRNA and protein levels. Moreover, knockdown of RRM2 attenuated CREB1-induced aggressive phenotypes of CRC cells in vitro and in vivo . Analysis of the data from TCGA database and clinical CRC specimens with immunohistochemical staining also demonstrated a strong correlation between the co-expression of CREB1 and RRM2. Decreased disease survivals were observed in CRC patients with high expression levels of CREB1 or RRM2. Our results indicate CREB1 as a critical transcription factor of RRM2 which promotes tumor aggressiveness, and imply a significant correlation between CREB1 and RRM2 in CRC specimens. These may provide the possibility that CREB1 and RRM2 could be used as biomarkers or targets for CRC diagnosis and treatment.