EED gene polymorphism in patients with colorectal cancer

Significant association of EED promoter hypomethylation with colorectal cancer

Colorectal cancer (CRC) is one of the most common and serious types of malignancy worldwide. The embryonic ectoderm development (EED) gene is important to maintain transcriptional repressive states of genes over successive cell generations. The present study aimed to investigate the association between EED methylation and CRC. A total of 111 CRC tissue samples, 111 paired para-tumor tissues and 20 colorectal normal tissues were obtained for EED methylation assay, which was performed using a quantitative methylation-specific polymerase chain reaction. The percentage of methylated reference was calculated to represent the DNA methylation level. A dual-luciferase reporter gene assay was used to detect the gene promoter activity of a EED fragment. The current results revealed a significant difference in the EED methylation levels among tumor, para-tumor and normal colorectal tissues (tumor vs. para-tumor vs. normal, 5.03±4.61 vs. 8.65±11.50 vs. 40.12±45.31; F=45.014; P<0.0001). The dual-luciferase reporter gene assay demonstrated that the transcriptional activity of recombinant pGL3-EED plasmid was significantly higher compared with that of the pGL3-Basic control vector (fold-change, 3.15; P=0.014), which suggests the EED fragment can promote gene expression. In conclusion, the present study demonstrated that EED hypomethylation may be an important factor associated with CRC.

Transcriptome‑wide piRNA profiling in human gastric cancer

Piwi-interacting RNAs (piRNAs) comprise the largest class of non-coding RNAs. They represent a molecular feature shared by all non-aging biological systems, including germline and somatic cancer stem cells, which display an indefinite capacity of renewal and proliferation and are potentially immortal. They have been identified in animal stomachs, but their relationship with human gastric cancers remains largely unclear. The present study aimed to identify the piRNAs associated with human gastric cancers across the whole transcriptome. Fresh tumor tissues and adjacent non-tumorous tissues from stomachs were examined using a piRNA microarray (23,677 piRNAs) that was then validated by qPCR. The differential expression of piRNAs between cases and controls was analyzed. The transposable elements (TEs) that are potentially targeted by the risk piRNAs were searched. The expression of the nearest genes that are complementary to the sequences of the piRNAs was examined in the stomach tissue. The regulatory effects of genome-wide significant and replicated cancer-risk DNA variants on the piRNA expression in stomach were tested. Based on the findings, we identified a total of 8,759 piRNAs in human stomachs. Of all, 50 were significantly (P<0.05) and differentially (>2-fold change) expressed between the cases and controls, and 64.7% of the protein-coding genes potentially regulated by the gastric cancer-associated piRNAs were expressed in the human stomach. The expression of many cancer-associated piRNAs was correlated with the genome-wide and replicated cancer-risk SNPs. In conclusion, we conclude that piRNAs are abundant in human stomachs and may play important roles in the etiological processes of gastric cancers.

Expression and clinicopathological significance of EED, SUZ12 and EZH2 mRNA in colorectal cancer

BACKGROUND AND OBJECTIVES

Enhancer of zeste 2 (EZH2), embryonic ectoderm development (EED), and suppressor of zeste 12 homolog (SUZ12), the key component of polycomb repressive complex 2, are of great importance in human cancer pathogenesis. This study was designed to investigate the clinical and prognostic significances of EZH2, EED and SUZ12 in colorectal cancer (CRC) patients.

METHODS

The expression of EZH2, EED and SUZ12 mRNA was evaluated in 82 primary CRC and paired non-cancerous mucosa samples by qRT-PCR.

RESULTS

We found that overall EZH2, EED and SUZ12 mRNA expression in the CRC tissues was significantly increased than in the non-cancerous tissue (p < 0.05). Increased EZH2, EED and SUZ12 mRNA expression was directly correlated with primary tumor size, regional lymph node metastases, distant metastasis and AJCC stage. Furthermore, CRC patients with higher level of EED, SUZ12 or EZH2 showed a worse disease-free survival (DFS) (p < 0.01). In multivariate analysis, the increased EZH2 expression may be a risk factor for the patients' 3-year DFS (HR 2.517; 95% CI 1.104, 5.736; p = 0.028). Furthermore, the k-means cluster analysis showed that high mRNA expression of EED, SUZ12 and EZH2 was significantly correlated with the aggressive clinical behavior and poor prognosis.

CONCLUSIONS

High expression of EED, SUZ12 and EZH2 might contribute to the CRC development/progression.

Neurokinin-2 receptor polymorphism predicts lymph node metastasis in colorectal cancer patients

To analyze the single nucleotide polymorphisms (SNPs) of two subtypes of neurokinin (NK) receptors, NK1R and NK2R (also known as TAC1R and TAC2R), in colorectal cancer (CRC), peripheral blood samples were collected from 199 CRC patients. Direct-sequencing was performed to identify the NK1R rs10198644 and NK2R rs4644560 SNPs. Genotype results were correlated with clinical factors. The allele frequencies of NK1R rs10198644 GC, CC and GG were 52, 17 and 31%, respectively, while that of NK2R rs4644560 GC, CC, and GG were 36, 50 and 14%, respectively. Patients with NK2R rs4644560 GC exhibited more positive lymph nodes than those with CC (mean, 2.2 vs. 1.3; P=0.016). Further analysis highlighted that the number of positive lymph nodes was also increased in the NK2R rs4644560 GC/NK1R rs10198644 GG group compared with the NK2R rs4644560 GG/NK1R rs10198644 GG group (mean, 2.2 vs. 0.9; P=0.04). These data suggested that the NK2R rs4644560 GC polymorphism alone or combination with NK1R rs10198644 GG may be a promising prognostic marker of lymph node metastasis in CRC patients.