|Year : 2018 | Volume
| Issue : 3 | Page : 604-607
Up-regulated expression of miR-155 in human colonic cancer
Hongliang Cao1, Shaojun Huang2, Aihua Liu3, Zhidan Chen1
1 Department of General Surgery, Affiliated Xiangyang Central Hospital of Hubei University of Arts and Science, Xiangyang, Hubei Province, P.R. China
2 Department of Clinical Laboratory, Affiliated Xiangyang Central Hospital of Hubei University of Arts and Science, Xiangyang, Hubei Province, P.R. China
3 Department of Tumor, Affiliated Xiangyang Central Hospital of Hubei University of Arts and Science, Xiangyang, Hubei Province, P.R. China
|Date of Web Publication||12-Jun-2018|
Dr. Zhidan Chen
Department of General Surgery, Affiliated Xiangyang Central Hospital of Hubei University of Arts and Science, 136 Jinzhou Road, Xiangyang, Hubei Province
Source of Support: None, Conflict of Interest: None
Objective: The aim of this study is to investigate the expression of miR-155 in colonic cancer tissue and to assess the potential predictive value of miR-155 in colonic cancer patients.
Materials and Methods: From March to September of 2011, we included 57 patients with primary colonic cancer who underwent curative surgical resection. Total RNAs were extracted from colonic cancer tissues and adjacent normal tissues. Then the expression of miR-155 in colonic cancer and paracancerous tissues was investigated using real time quantitative reverse transcription-polymerase chain reaction. And the relationship between miR-155 expression level and the clinical, pathological parameters of colonic cancer was analyzed.
Results: The relative expression level of miR-155 in colonic cancer tissues was significantly higher than that in paracancerous tissues and related to tumor-node-metastasis staging, tumor invasion, metastasis, and differentiation.
Conclusion: The expression of miR-155 is up-regulated in colonic cancer tissues. MiR-155 may acts as proto-oncogenes involved in carcinogenesis, development, and invasion of colon cancer making it a potential target for gene therapy of colon cancer.
Keywords: Colonic cancer, micro RNA, miR-155
|How to cite this article:|
Cao H, Huang S, Liu A, Chen Z. Up-regulated expression of miR-155 in human colonic cancer. J Can Res Ther 2018;14:604-7
| > Introduction|| |
miR-155 is located in chromosome 21q21 and encoded by the highly conserved regions in the third exon of the B-cell integration cluster. Recent studies indicated that miR-155 is abnormally expressed in many kinds of human tumors and is correlated with the development and the prognosis of tumor.,,, In this study, we used real time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to analyze the expression level of miR-155 in colon cancer tissues, which were collected from 57 patients from March to September of 2011. Then we explored the relationship between miR-155 expression and the clinical, pathological parameters of colon cancer patients.
| > Materials and Methods|| |
Patients and tissue specimens
Between March and September of 2011, 57 primary colon cancer patients who did not receive radiotherapy and chemotherapy before surgical treatment were recruited. The median age of enrolled patients was 59 years (range: 35–78 years). The resected specimens of cancer tissue and corresponding adjacent normal mucosa, which is 5 cm away from the edge of the tumor were frozen in liquid nitrogen within 30 min of resection and then were stored in a refrigerator with a temperature setting of −70°C. This study protocol was reviewed and approved by the Ethics Review Board of Our Hospital.
TRizol RNA extraction reagents and reverse transcription (RT) kit were purchased from Invitrogen Corporation, and the miR-155 and U6 snRNA qRT-PCR assay kit were purchased from Shanghai GenePharma Co., Ltd.
Real time fluorescence quantitative polymerase chain reaction
Tissue RNA was isolated using TRizol (Life Technologies) according to manufacturer's instructions. RT and qRT-PCR were performed using Hairpin-itTM microRNAs (miRNAs) RT-polymerase chain reaction quantitation kit (GenePharma) according to the manufacturer's instruction. Normalizations were done using U6 snRNA levels, and the fold changes were calculated by the ΔΔCT method. For qRT-PCR, the following primers were used miR-155: Forward, 5'-ACG CTC AGT TAA TGC TAA TCG TGA TA-3', reverse 5'-ATT CCA TGT TGT CCA CTG TCT CTG-3'; U6 snRNA: Forward, 5'-ATT GGA ACG ATA CAG AGA AGA TT-3', reverse, 5'-GGA ACG CTT CAC GAA TTT G-3'. The reaction conditions were as follows: 95°C for 3 min, followed by 40 cycles at 95°C for 20 s, 60°C for 50 s each.
The SPSS software (version 13.0, SPSS Inc.) was used to perform statistical analysis. For comparison of the expressional difference of miR-155 between colonic cancerous and paracancerous ones, we applied a Wilcoxon signed rank test. For comparison of the expressional difference of miR-155 between patients in different clinic-pathological status [Table 1], we applied a Student's t-test. Correlations between miR-155 expression and clinical, pathological parameters were calculated using Spearman's rank correlation coefficients. Significance was defined as P < 0.05.
|Table 1: Relationship between miR-155 expression and pathological factors in colon cancer patients|
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| > Results|| |
Expression of miR-155 in colon cancer tissue and normal tissues
We identified gene expression levels of the miR-155 in 57 colonic tumor tissues and paracancerous ones. Enhanced expression of miR-155 was detected in 45 of 57 (78.9%) colonic cancer tissues, compared with paracancerous tissues. The mean relative expression of miR-155 in the colonic cancer tissues was 0.421 (range: 0.016–1.241), while in paracancerous tissues was 0.128 (range: 0.000–0.337). Differences between the two groups were evaluated using the Wilcoxon test for 57 paired samples. We found that miR-155 was significantly higher expressed in colonic cancerous, compared with paracancerous tissues (P < 0.001). At the annealing temperatures used in the qRT-PCR experiments, unimodal melting curves were observed, validating the specificity of the gene targets [Figure 1].
Association between miR-155 and clinical, pathological parameters of colonic cancer
Tumors expressed higher levels of miR-155, suggesting that mi155 up-regulation was somewhat associated with colonic cancer progression. To further evaluate whether miR-155 high-expression was linked to the clinical progression of colonic cancer, we analyzed the association of miR-155 with the clinic-pathological status of colonic cancer patients. Indeed, miR-155 expression was positively correlated with tumor invasion (P = 0.018) andpathological tumor-node-metastasis (pTNM) stage (P = 0.026) of the patients, and negatively correlated with tumor differentiation (P = 0.022). Furthermore, miR-155 expression in patients with lymph node metastasis was significantly higher than those without lymph node metastasis. However, no significant correlation was observed between miR-155 expression and gender, age and serum carcinoembryonic antigen (CEA) level of the patients [Table 1].
| > Discussion|| |
Colonic cancer is the most common malignancy of the digestive tract, estimated to cause 9–12% of all cancer deaths in the USA, Canada, and Europe. miRNAs are approximately 22nt, endogenous and noncoding RNAs that play important roles in RNA silencing and posttranscriptional regulation of gene expression. miRNAs are increasingly being recognized as oncogenes and tumor suppressors in cancer. It has been observed that miR-155 is up-regulated in numerous solid cancers including breast cancer, thyroid cancer, endometrial cancer, and lung cancer suggesting a correlation between miR-155 and tumor genesis, development and prognosis.,,,,
In this study, we found that up-regulation of miR-155 expression was observed in 78.9% (45 out of 57) colonic cancer tissues, suggesting a potential pathogenesis role of miR-155 in colonic cancer. Furthermore, we revealed that miR-155 expression was positively correlated with colonic cancer invasion, lymph node metastasis and pTNM stage of the patients, and negatively correlated with tumor differentiation. Our data suggested that miR-155 may act as proto-oncogene involved in the genesis and development of colon cancer, making miR-155 a useful marker for molecular typing of colon cancer and a new target for gene therapy.
CEA is a kind of adhesion factor of tumor cells, dynamically detecting serum CEA level is important to monitor recurrence and metastasis after the operation. About two-third patients who were confirmed recurrence has serum CEA level increased. Serum CEA level can indicate tumor recurrence and metastasis median 3–9 months earlier than observable morphological changes. It cannot be proved that miR-155 expression level has nothing to do with tumor recurrence and metastasis though it was not significantly related with serum CEA level in this study. We will take dynamically observation on serum CEA level of postoperative patients and strict follow-up of them to speculate the relationship between miR-155 expression and postoperative serum CEA level, and the relationship between miR-155 expression and prognosis.
Although there are many studies describing the direct correlation between the expression of miR-155 and tumor occurrence, the precise mechanisms underlying these observations are not as yet fully understood. In many human cancer cell lines, expression of miR-155 is induced by factors that promote tumor inflammation such as hypoxia, interleukin 6, or interferon gamma. Currently, more than 100 genes are confirmed to be directly targeted by miR-155, making it acts in the middle of oncogenic loops that repress the activity of several tumor suppressors. It has been reported that miR-155 inhibits SOCS1 and accordingly stimulates the activity of the JAK2/STAT3 pathway, thus promoting tumor inflammation and growth. MiR-155 also contributes to the oncogenic metabolism by stimulating glycolysis through induction of a glycolytic enzyme, hexokinase 2, by directly targets C/enhancer binding protein-β, a transcription activator of miR-143, which in turn directly inhibits translation of hexokinase 2. Other crucial targets of miR-155 includes the pro-apoptotic transcription factor FOXO3a and a tumor suppressor tumor protein p53 inducible nuclear protein 1., Recently, Chiang's group identified a novel pathway regulated by miR-155 and demonstrated that miR-155 promotes the activity of hypoxia-inducible factor transcription factors and angiogenesis through targeting von Hippel-Lindau tumor suppressor in breast cancer. It will be of interest to know whether the oncogenic mechanisms promoted by miR-155 discussed above also works in colon cancer.
The miR-155 is not only involved in diversity of cancers, but also as a regulator of the immune system. An initial study reported that both the number of germinal centers and antibody production have been greatly reduced in miR-155-deficient mice. In contrast to miR-155-deficient mice, a transgenic mouse model expressing miR-155 has been investigated and found that dysregulated B-cell development caused the marked accumulation of pre-B-cells in these mice, showing a critical role of miR-155 on B-cell development. Besides B-cells, the biological behaviors of T-cells are also both positively and negatively controlled by miR-155. A recent study revealed that augmented expression of miR-155 down-regulated CTLA-4 expression in patients with atopic dermatitis. In CD8 T-cells, miR-155 expression increases in response to T-cell receptor and is maintained with interleukin-2 (IL) and IL-15. Upon viral infection, miR-155 expression is elevated in effector and effector memory CD8 T-cell compartments. Animal studies have shown that the antiviral response in CD8 T-cells decreases and virus eradication does not occur properly in miR-155-deficient mice.
| > Conclusions|| |
The results of this study indicated that the expression difference of miR-155 levels between colonic tissues and paracancerous tissues was statistically significant. The miR-155 levels were quite correlated with clinic-pathological characteristics of patients with colonic cancer. The results of this study were consistent with the literature and support the notion that miR-155 was an oncogenic miRNAs.
Financial support and sponsorship
This study was supported by the Municipal Science and Technology Bureau of Xiangyang (2010GG3A).
Conflicts of interest
There are no conflicts of interest.
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