CRC is a frequently diagnosed malignant tumor worldwide, with high morbidity and mortality [16]. In China, the incidence of CRC shows increasing tread, posing a great threat to human health [17]. Despite of the various available treatments for CRC, the long term outcomes of CRC patients still remain unsatisfactory, which may be attributed to high occurrence of postoperative recurrence and metastasis [18]. Tumor progression prediction represents a challenge for CRC patients in clinic, due to the lack of credible biomarkers [19]. Therefore, identification of effective prognostic biomarkers for CRC may be a promising approach to improve management and prognosis of patients with CRC.
The development and progression of CRC is a complex process, with the involvement of a variety of molecules and signaling pathways, such as oncogene activation, suppressor gene inactivation, and epigenetic modifications [20]. Up to now, the molecular mechanisms underlying CRC is still unclear. In order to improve the management and prognosis of CRC, various researches were devoted to explore the genetic biomarkers for prognosis prediction in CRC. For instance, Zhu et al., found that Twist1 could enhance proliferation and chemoresistance of CRC cells which might be a potential prognostic marker and a molecular therapeutic target for the cancer [21]. Zhang et al. indicated that up-regulation of nemo-like kinase (NLK) was positively correlated with recurrence and distant metastasis of CRC patients, predicting poor prognosis for patients with the disease [22]. The clinical significance of MTA2 expression for prognosis of CRC was investigated by Ding et al. They found the expression profile of MTA2 exhibited high in CRC tissues specimens, and significantly correlated with overall survival of the patients, suggesting its possible as a prognostic biomarker for CRC [23]. These cancer-related molecules might provide reliable information for tumor progression of CRC. In the current study, we investigated the prognostic value of EYA4 for CRC.
EYA4, a member of EYA family, has recently been identified as a tumor suppressor gene in many kinds of cancers, including hepatocellular carcinoma, acute myeloid leukemia, oral cancer, etc [14, 24, 25]. In the current study, we investigated the functional roles of EYA4 in CRC. We detected the expression of EYA4 at mRNA level in CRC tumor tissues and the adjacent normal tissues. Our results showed that the level of EYA4 was significantly down-regulated in tissues compared with adjacent normal tissues. Then we further investigated the effects of EYA4 expression level on the development of CRC. The results indicated that EYA4 was negatively associated with DUKE stage, differentiation and vascular invasion. All the data revealed the anti-tumor action of EYA4 in CRC, and its reduced expression could contribute to malignant progression of the disease.
Given its function in tumorigenesis, EYA4 was identified as a biomarker for several cancers. In pancreatic ductal adenocarcinoma, down-regulation of EYA4 predicted short overall survival for the patients [26]. The expression pattern of EYA4 also held referenced significance for prognosis of patients with intrahepatic cholangiocarcinoma [27]. In CRC, Liu et al. reported that the serum methylation levels of EYA4 were significantly different between stage I CRC patients and healthy individuals that might be an useful biomarker for early detection of CRC [28]. However, the prognostic value of EYA4 in CRC was still unclear. In this study, Kaplan-Meier analysis showed that patients with low expression of EYA4 had a shorter overall survival than those with high expression. According to cox regression analysis, EYA4 might be employed as an independent prognostic factor for CRC. Low expression of EYA4 predicted poor prognosis for the patients.