International Scholarly Research Network ISRN Gastroenterology Volume 2012, Article ID 394545, 6 pages doi:10.5402/2012/394545 Research Article Lowly Expressed Ribosomal Protein S19 in the Feces of Patients with Colorectal Cancer Chih-Cheng Chien, 1, 2 Tien-Chien Tu, 3, 4 Chi-Jung Huang, 2, 5, 6 Shung-Haur Yang, 7, 8 and Chia-Long Lee 4, 9 1 Department of Anesthesiology, Sijhih Cathay General Hospital, New Taipei 22174, Taiwan 2 School of Medicine, Fu Jen Catholic University, New Taipei 24257, Taiwan 3 Department of Internal Medicine, Cathay General Hospital, Taipei 10630, Taiwan 4 School of Medicine, Taipei Medical University, Taipei 11031, Taiwan 5 Department of Medical Research, Cathay General Hospital, Taipei 10630, Taiwan 6 Department of Biochemistry, National Defense Medical Center, Taipei 11490, Taiwan 7 Department of Surgery, Taipei-Veterans General Hospital, Taipei 11217, Taiwan 8 School of Medicine, National Yang Ming University, Taipei 11221, Taiwan 9 Department of Internal Medicine, Hsinchu Cathay General Hospital, Hsinchu 30060, Taiwan Correspondence should be addressed to Chia-Long Lee, cghleecl@hotmail.com Received 16 August 2011; Accepted 4 October 2011 Academic Editors: A. Amedei and S. Gr¨ osch Copyright © 2012 Chih-Cheng Chien et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Colorectal cancer (CRC) has become one of the most common fatal cancers. CRC tumorigenesis is a complex process involving multiple genetic changes to several sequential mutations or molecular alterations. P53 is one of the most significant genes; its mutations account for more than half of all CRC. Therefore, understanding the cellular genes that are directly or indirectly related to p53 is particularly crucial for investigating CRC tumorigenesis. In this study, a p53-related ribosomal protein, ribosomal protein S19 (RPS19), obtained from the feces of CRC patients is evaluated by using specifically quantitative real-time PCR and knocked down in the colonic cell line by gene silencing. This study found that CRC patients with higher expressions of RPS19 in their feces had a better prognosis and consistent expressions of RPS19 and BAX in their colonic cells. In conclusion, the potential mechanism of RPS19 in CRC possibly involves cellular apoptosis through the BAX/p53 pathway, and the levels of fecal RPS19 may function as a prognostic predictor for CRC patients. 1. Introduction Despite progress in reducing the incidence and mortality rate and improving patient survival, human cancers still account for numerous deaths [1]. Colorectal cancer (CRC) has be- come one of the most common fatal cancers, involving a complex process with multiple genetic changes [2–4]. This molecular heterogeneity possibly results from multi- ple sequential mutations or molecular alterations during tumorigenesis [5]. Therefore, the identification of CRC-re- lated genes will assist in cancer prevention, detection, and prognostic prediction [6–8]. One important tumor suppressor, p53, is known to pre- vent cancer, but is also involved in CRC progression [9, 10]. Mutations of p53 account for more than half of all CRCs, particularly in patients at the more advanced stages [11]. Numerous cellular genes are also out of control because of the abnormal p53 expression during tumor progression [12, 13]. For example, the p53-related ribosomal proteins (RPs) were identified as cancer-related molecules [14, 15], indicating that the oncogenic potential of RPs result from the relationship between p53 and RPs [16–18]. Moreover, the p53-inducible modulator RPS27-like (RPS27L), which responds to genotoxic stress, was recently evaluated in CRC [19]. Feces can serve as the material for detecting genetic al- terations in CRC [20–22]. Numerous ribosomal proteins