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The aim of the present study was to investigate the PAQR3 gene expression and its methylation level in colorectal cancer tissues, as well as the association with colorectal cancer clinical data. In total, 54 cases of colorectal cancer tissue samples and normal adjacent tissue samples were collected between June, 2013 and July, 2014. RT-PCR and western blot analysis were used to detect the mRNA and protein levels of PAQR3 in colorectal samples, respectively. MSP was used to detect the methylation level of PAQR3 gene in colorectal samples, which was compared with colorectal data. The results showed that a decreased expression level of PAQR3 mRNA in colorectal cancer tissues and the expression reduction rate was 57.4% (31/54). Similarly, the expression level of PAQR3 protein was reduced in cancer tissues, and the reduction rate was 46.3% (25/54), while the protein expression reduction rate in cancer adjacent tissue was 5.6% (3/54), and the difference was statistically significant (P<0.05). Furthermore, the methylation rates of PAQR3 in cancer tissues and cancer adjacent tissues were 33.3% (18/54) and 5.6% (3/54), respectively. In addition, PAQR3 mRNA and protein levels in colorectal cancer tissues were associated with the differentiation degree, lymphatic metastasis and tumor infiltration depth. The methylation level of PAQR3 was associated with age, differentiated degree, lymphatic metastasis and tumor infiltration depth. In conclusion, the expression of PAQR3 mRNA and protein in colorectal cancer was reduced and methylation of PAQR3 occurred. Although the PAQR3 mRNA and protein levels were not associated with gender, age or the location of tumor, there was an association with differentiation degree, lymphatic metastasis and tumor infiltration depth. In addition, the methylation level of PAQR3 was not correlated with gender or tumor location, but was correlated with age, differentiation degree, lymphatic metastasis and tumor infiltration depth. [ABSTRACT FROM AUTHOR]

BACKGROUND: Rectal cancer is an important contributor to cancer mortality. OBJECTIVE: The objective of this paper is to identify key genes across three phenotypes (fungating, polypoid and polypoid & small-ulcer) of rectal cancer based on multiple differential expression networks (DENs). METHODS: Differential interactions and non-differential interactions were evaluated according to Spearman correlation coef- ficient (SCC) algorithm, and were selected to construct DENs. Topological analysis was performed for exploring hub genes in largest components of DENs. Key genes were denoted as intersections between nodes of DENs and rectal cancer associated genes from Genecards. Finally, we utilized hub genes to classify phenotypes of rectal cancer on the basis of support vector machines (SVM) methodology. RESULTS:We obtained 19 hub genes and total 12 common key genes of three largest components of DENs, and EGFR was the common element. The SVMresults revealed that hub genes could classify phenotypes, and validated feasibility of DEN methods. CONCLUSIONS: We have successfully identified significant genes (such as EGFR and UBC) across fungating, polypoid and polypoid & small-ulcer phenotype of rectal cancer. They might be potential biomarkers for classification, detection and therapy of this cancer. [ABSTRACT FROM AUTHOR]