The overexpression of AUF1 in colorectal cancer predicts a poor prognosis and promotes cancer progression by activating ERK and AKT pathways.

BACKGROUND: AUF1 is one of the AU-rich binding proteins, which promotes rapid ARE-mRNA degradation. Recently, it has been reported that AUF1 is involved in regulating the antioxidant system because of its capacity to bind specifically to RNA containing oxidized bases and degrade oxidized RNA. Many antioxidant proteins have been reported to be overexpressed in colorectal cancer (CRC), however, the role of AUF1 in the progression of CRC has not been explored. METHODS: The expression level of AUF1 protein in human CRC cell lines and CRC tissues was detected by western blotting and immunohistochemistry (IHC. The effects of AUF1 knockdown on CRC cell proliferation, migration, invasion and changes in the signaling pathways were evaluated using a cell counting kit-8 (CCK-8), Transwell assays and western blotting. Subcutaneous xenograft tumor model was employed to further substantiate the role of AUF1 in CRC. RESULTS: AUF1 protein was upregulated in CRC tissues and CRC cells, and high expression of AUF1 was significantly associated with advanced AJCC stage (P = .001), lymph node metastasis (P = .007), distant metastasis (P = .038) and differentiation (P = .009) of CRC specimens. CRC patients with the high expression of AUF1 had an extremely poor prognosis. The knockdown of AUF1 suppressed CRC cell line proliferation, migration and invasion, inhibited CRC cells tumorigenesis and growth in nude mice, and reduced phosphorylated-ERK1/2 and phosphorylated AKT in CRC cells. CONCLUSION: Our findings demonstrate that AUF1 is probably involved in the progression of CRC via the activation of the ERK1/2 and AKT pathways. AU-rich RNA-binding factor 1 could be used as a novel prognostic biomarker and a potential therapeutic target for CRC.

MutT-related proteins are novel progression and prognostic markers for colorectal cancer.

BACKGROUND: MutT-related proteins, including MTH1, MTH2, MTH3 and NUDT5, can effectively degrade 8-oxoGua-containing nucleotides. The MTH1 expression is elevated in many types of human tumors and MTH1 overexpression correlates with the tumor pathological stage and poor prognosis. However, the expression of other MutT-related proteins in human cancers remains unknown. The present study systematically investigated the expression of MTH1, MTH2, MTH3 and NUDT5 in human colorectal cancer to establish its clinical significance. METHODS: Amounts of MutT-related mRNA and protein in CRC cell lines were assessed by qRT-PCR and Western blotting, respectively. Furthermore, the MutT-related protein expression was evaluated by immunohistochemical staining of tissue microarrays containing 87 paired CRC tissues and by Western blotting of 44 CRC tissue samples. Finally, the effect of knockdown of MutT-related proteins on CRC cell proliferation was investigated. RESULTS: The expression of MTH1, MTH2, MTH3 and NUDT5 was significantly higher in CRC cells and CRC tissues than normal cells and tissues, and this phenomenon was significantly associated with AJCC stage and lymph node metastasis of CRC specimens. CRC patients with high expression of MTH1, MTH2 or NUDT5 had an extremely poor overall survival after surgical resection. Notably, NUDT5 was an independent prognostic factor of CRC patients. We found that knockdown of MutT-related proteins inhibited CRC cell proliferation. CONCLUSIONS: We showed for the first time that MutT-related proteins play an important role in CRC progression and prognosis. Further investigations are needed to elucidate the role of these proteins in CRC progression and their potential use for therapeutic targets.

Expression of miR-21, miR-31, miR-96 and miR-135b is correlated with the clinical parameters of colorectal cancer.

The aim of this study was to determine the expression of miR-21, miR-31, miR-96 and miR-135b in 52 paired colorectal cancer (CRC) tissues and to analyze the correlation between microRNAs (miRNAs) and clinicopathological features. We developed a quantification method that relies on a standard plot, constructed from known concentrations of standards, in order to measure the number of miRNAs. In addition to this, we analyzed the expression levels of miR-21, miR-31, miR-96 and miR-135b in 52 cases of primary CRC and corresponding normal mucosal tissue using real-time PCR with SYBR-Green I. An independent sample t-test was used to compare the differential expression between tumor tissues and normal mucosal tissues. The Mann-Whitney U and Kruskall-Wallis tests were used to compare the correlation between miRNA expression levels and clinicopathological features. The expression of miR-21, miR-31, miR-96 and miR-135b was upregulated in the CRC tissues compared to normal mucosal tissues (P<0.05). Furthermore, miR-21 and miR-135b were positively correlated with the clinical stage (P=0.048 and P=0.029, respectively), while miR-96 and miR-135b were correlated with liver metastasis (P=0.006 and P=0.013, respectively). Our results suggest that miR-21, miR-31, miR-96 and miR-135b may function in the process of CRC development and progression. miR-135b levels in particular may correlate with the degree of malignancy.

DNA alterations of microsatellite DNA, p53, APC and K-ras in Chinese colorectal cancer patients.

BACKGROUND: Colorectal cancer is one of the most rapidly increasing cancers in the world, and accumulation of alterations in oncogenes, tumour suppressor genes and mismatch repair (MMR) genes contributes to colorectal tumorigenesis. Thus, we investigated the alterations of 14 microsatellite loci adjacent to MMR genes, p53, adenomatous polyposis coli (APC) and K-ras in 52 Chinese patients with colorectal cancer. MATERIALS AND METHODS: We performed fluorescent polymerase chain reaction and capillary electrophoresis to analyse microsatellite instability (MSI) and loss of heterozygosity (LOH) in microsatellite loci, which included a panel of nine dinucleotide repeats and the Bethesda consensus panel. Additionally, we screened for mutations in exons 4-9 of p53 and the mutation cluster region (MCR) in APC by DHPLC. Codons 12, 13 and 61 in K-ras were analysed using direct sequencing. All variations were confirmed using clone sequencing. RESULTS: The alteration frequency of microsatellite DNA was 55·8% (29/52). Among the microsatellites, five loci exhibited MSI and another nine loci exhibited LOH. The mutation rates of p53, APC and K-ras were 42·3%, 38·5% and 36·5%, respectively. All patients (n = 7) with liver metastasis had a mutation in p53, APC or K-ras. APC mutation was correlated with clinical stage and the presence of lymph node metastasis (P = 0·001 and P = 0·006, respectively). CONCLUSIONS> A total of 80·8% of Chinese patients with colorectal cancer show variations in microsatellite DNA, p53, APC or K-ras. It appears that these microsatellite DNA alterations could be a new biomarker for colorectal cancer.