NLK, a novel target of miR-199a-3p, functions as a tumor suppressor in colorectal cancer.

We previously reported that miR-199a-3p is a newly biomarker for diagnosis and novel prognostic indicator in colorectal cancer. However, the miR-199a-3p regulatory mechanism and its target genes are still unclear. In our present study, we demonstrated miR-199a-3p could directly target 3'-UTR of NLK gene by luciferase reporter assay and western blot analysis. We detected NLK expressions in 92 colorectal cancer cases to evaluate its clinicopathologic characteristics in colorectal cancer. Our results showed that NLK expression was significantly downregulated in cancer tissues than NATs, and NLK low-expression was associated with lymph node metastasis, venous invasion, liver metastasis and the TNM stage (P<0.05). Moreover, Kaplan-Meier analysis showed that low expression of NLK correlated with a shorter overall survival rates of patients with CRC (P<0.05). In vitro, we also found that NLK suppressed the biological behaviors of colorectal cancer cells, including the abilities of cell proliferation, clone formation, wound healing, migration and invasion (P<0.05), while overexpression of NLK increased the apoptotic rate of colorectal cancer cells. All these results suggested that NLK was an identified miR-199a-3p target gene and functioned as a tumor suppressor gene in colorectal cancer. NLK could be a novel direction for developing diagnostic and therapeutic approaches in colorectal cancer.

Han Y ，Kuang Y ，Xue X ，Guo X ，Li P ，Wang X ，Guo X ，Yuan B ，Zhi Q ，Zhao H ... -  《-》

Downregulation of microRNA-409-3p promotes aggressiveness and metastasis in colorectal cancer: an indication for personalized medicine.

Liu M ，Xu A ，Yuan X ，Zhang Q ，Fang T ，Wang W ，Li C ... -  《Journal of Translational Medicine》

The deoxycholic acid targets miRNA-dependent CAC1 gene expression in multidrug resistance of human colorectal cancer.

There is evidence indicating that bile acid is a promoter of colorectal cancer. Deoxycholic acid modifies apoptosis and proliferation by affecting intracellular signaling and gene expression. We are interested in revealing the relationship between deregulated miRNAs and deoxycholic acid in colorectal cancer development. We found that miR-199a-5p was expressed at a low level in human primary colonic epithelial cells treated with deoxycholic acid compared with control, and miR-199a-5p was significantly down-regulated in colorectal cancer tissues. The miR-199a-5p expression in colorectal cancer cells led to the suppression of tumor cell growth, migration and invasion. We further identified CAC1, a cell cycle-related protein expressed in colorectal cancer, as a miR-199a-5p target. We demonstrated that CAC1 is over-expressed in malignant tumors, and cellular CAC1 depletion resulted in cancer growth suppression. HCT-8 cells transfected with a miR-199a-5p mimic or inhibitor had a decrease or increase in CAC1 protein levels, respectively. The results of the luciferase reporter gene analysis demonstrated that CAC1 was a direct miR-199a-5p target. The high miR-199a-5p expression and low CAC1 protein expression reverse the tumor cell drug resistance. We conclude that miR-199a-5p can regulate CAC1 and function as a tumor suppressor in colorectal cancer. Therefore, the potential roles of deoxycholic acid in carcinogenesis are to decrease miR-199a-5p expression and/or increase the expression of CAC1, which contributes to tumorigenesis in patients with CRC. These findings suggest that miR-199a-5p is a useful therapeutic target for colorectal cancer.

Kong Y ，Bai PS ，Sun H ，Nan KJ ，Chen NZ ，Qi XG ... -  《-》

Up-regulation of miR-592 correlates with tumor progression and poor prognosis in patients with colorectal cancer.

miR-592, as a potential biomarker, has been linked to several cancers. However, the expression level and prognostic value of miR-592 in CRC have not been elucidated. In this study, we detected the miR-592 expression in CRC serum, tumor tissues, adjacent non-tumor tissues (NATs) and four colorectal cancer cell lines by RT-PCR. Our data proved that miR-592 expression was up-regulated in clinical CRC serum and tissues (P<0.05). Serum or tissue miR-592 in CRC metastatic patients also maintained a high level, compared to that in non-metastatic CRC patients (P<0.05). After radical surgery, postoperative serum miR-592 level in CRC patients significantly decreased (P<0.05). Our clinicopathological analysis revealed that high miR-592 was significant associated with the tumor size (P=0.008), TNM stage (P=0.026), distant metastasis (P=0.004) and preoperative CEA level (P=0.022), which led to a shorter overall survival rate in CRC patients (P=0.032). Furthermore, we designed and transfected miR-592 mimics or inhibitors into the corresponding CRC lines, and our experiments in vitro demonstrated that miR-592 could promote cell proliferation, wound healing and invasion ability of CRC cells (P<0.05), while miR-592 did not influence the CRC cell apoptosis (P>0.05). All these results suggested that miR-592 functioned as a novel and potential carcinogen-initiated and metastasis-related biomarker in CRC, and down-regulation of miR-592 might be considered as a potentially significant molecular treatment strategy for CRC patients.

Liu M ，Zhi Q ，Wang W ，Zhang Q ，Fang T ，Ma Q ... -  《-》

MiR-199a/b-3p suppresses migration and invasion of breast cancer cells by downregulating PAK4/MEK/ERK signaling pathway.

MicroRNA-199a/b-3p is downregulated in several types of aggressive cancer, and its decrement significantly correlates with poor survival. Here, we aim to investigate the biological function of miR-199a/b-3p and its regulation of target genes in breast cancer cells with highly metastatic potential. In addition, we found that miR-199a/b-3p expression was much lower in MDA-MB-231, CAL120, and HCC1395 breast cancer cells with highly metastatic potential. Functional assays showed that restored miR-199a/b-3p expression inhibited MDA-MB-231 cell growth, cell-cycle progression, migration, and invasion. In addition, we experimentally demonstrated that PAK4 was the direct target of miR-199a/b-3p, hypo-expression of PAK4 suppressed proliferation, migration and invasion of MDA-MB-231 cells, and overexpression of PAK4 significantly rescued the inhibitory effect of miR-199a/b-3p on MDA-MB-231 cell growth, migration, and invasion. Further, we also observed that miR-199a/b-3p could inactivate the PAK4/MEK/ERK signaling pathway. Thus, miR-199a/b-3p functions as a tumor suppressor and has an important role in breast cancer metastasis through PAK4/MEK/ERK signaling pathway.

Li SQ ，Wang ZH ，Mi XG ，Liu L ，Tan Y ... -  《-》