Background Mitogen/extracellular signal-regulated kinase kinase-5 (MEK5) has been confirmed to play

Background Mitogen/extracellular signal-regulated kinase kinase-5 (MEK5) has been confirmed to play a pivotal role in tumor carcinogenesis and progression. node metastasis, distant metastasis and histological grade. Survival analysis revealed that MEK5 overexpression negatively correlated with cancer-free survival (hazard ratio 1.64, P?=?0.017). RNA interference-mediated knockdown of MEK5 in SW480 colon cancer cells decreased their proliferation, division, migration and invasiveness in vitro and slowed down tumors growth in mice engrafted with the cells. Conclusion MEK5 plays an important role in CRC progression and may be a potential molecular target for the treatment of CRC. Keywords: MEK5, Colorectal malignancy, Univariate analyses, RNA interference, Tumor growth Background Colorectal malignancy (CRC) is usually a common malignant disease and remains one of the leading causes of cancer mortality worldwide [1]. With the development of Chinas economy, the incidence of CRC in China is usually increasing and now causes a substantial malignancy burden in China, particularly in the more developed areas such as Guangdong and Shanghai [2C4]. The carcinogenesis of CRC is often a multistep process and possibly consequent of a complex conversation between multiple factors, both endogenous and environmental stressors [5]. The environmental stressors such as drinking buy Spectinomycin HCl and smoking could lead to activation of many crucial molecular pathways, such as mitogen-activated protein kinases (MAPKs) [6], and the Wnt/Wingless signaling pathway [7], eliciting a variety of biological responses. MAP kinase kinases (MEKs/MAPKKs) represent a family of protein kinases upstream of the MAP kinases, which play an important role in cell proliferation and apoptosis [8]. Mitogen/extracellular signal regulated kinase kinase-5 (MEK5), a key kinase of the MEK5-ERK5 pathway, in turn specifically phosphorylates and activates extracellular signal-regulated kinase-5 (ERK5) [9], which directly phosphorylates and activates several transcription factors including c-Myc, Sap-1, c-Fos, Fra-1, and myocyte enhancer factor family members [10, 11], eliciting a variety of biological responses to extracellular signals that include cytokines, growth factors, and various stress stimuli [12]. The MEK5 cDNA encodes a 444-amino acid protein, which displays approximately 40?% identity to known MEKs [13]. The alternative splicing of the mRNA produces two isoforms with different N-termini, MEK5 (50?kDa) and MEK5 (40?kDa) [14]. The expression of the MEK5 protein is greater than that of MEK5 in terminally differentiated tissues, while MEK5 expression is usually greater in mitotically active tissues such as the liver. MEK5 directly stimulates ERK5 kinase activity, whereas MEK5 plays a kinase-dead dominant-negative role that suppresses ERK5 signaling [15]. A growing number of studies have shown that overexpression of MEK5 is usually associated with tumorgenesis and malignancies [16, 17] and the expression ratio of MEK5 to MEK5 is usually higher in malignancy cell lines, while overexpression of MEK5 inhibits serum-induced DNA synthesis [17]. Therefore, option splicing of MEK5 and MEK5 may play a pivotal role in ERK5 activation and subsequent carcinogenesis. There buy Spectinomycin HCl are many studies suggesting that MEK5 plays a critical role in malignancy occurrence and development, such as prostate malignancy [18], breast malignancy [19], hepatocellular malignancy [20] and lung malignancy [21]. We have previously shown the -163?T?>?C polymorphism in the MEK5 promoter might affect the risk of developing CRC, and further research indicated that this possible mechanism of action might be the effect of -163?T?>?C variation around the MEK5 expression [22]. Recently, we found that expression of the phosphorylated MEK5 protein was associated with TNM staging buy Spectinomycin HCl of colorectal malignancy [23]. In this study, we further investigated the biological role of MEK5 in CRC. We analyzed the relationship between the MEK5 expression and clinicopathological parameters of colorectal carcinoma and assessed the prognostic value of MEK5 in colorectal carcinoma in a large number of patients. Furthermore, we silenced the MEK5 expression in colon cancer cell collection SW480 and evaluated the influence of MEK5 around the biological behaviors of colon cancer cells. Methods Patients and tissue specimens In this study, immunohistochemstry analysis was conducted on two buy Spectinomycin HCl groups of paraffin-embedded samples. The first group included 24 normal colorectal CD2 mucosa, 24 adenomas and 84 main colorectal adenocarcinomas, which were randomly collected from archival tissues surgically removed at the Sixth Affiliated Hospital of Sun Yat-sen University or college, between 2007 and 2010. All of buy Spectinomycin HCl these samples were pathologically confirmed. The second group included 342 archival tissues specimens of CRC, which were histologically and clinically diagnosed, from your First Affiliated Hospital of Sun Yat-sen University, between January 2000 and November 2006. The cases selected were based.