Colorectal cancer (CRC) has become the third most common cause of cancer-related deaths. CRC occurs because of abnormal growth of cells that can invade other tissues and cause distant metastases. Researchers have suggested that aberrant microRNA (miRNA) expression is involved in the initiation and progression of cancers. However, the key miRNAs that regulate the growth and metastasis of CRC remain unclear. The circulating miRNAs from BALB/c mice with CRC CT26 cell implantation were assayed by microarray. Then, Mus musculus (house mouse) mmu-miR-762 mimic and inhibitor were transfected to CT26 cells for analysis of cell viability, invasion, and epithelial-mesenchymal transition (EMT), cell cycle, and regulatory molecule expression. Human subjects were included for comparison the circulating Homo sapiens (human) has-miR-762 levels in CRC patients and control donors, as well as the patients with and without distant metastasis. The result for miRNA levels in mice with CRC cell implantation indicated that plasma mmu-miR-762 was upregulated. Transfection of mmu-miR-762 mimic to CT26 cells increased cell viability, invasion, and EMT, whereas transfection of mmu-miR-762 inhibitor decreased the above abilities. Cells treated with high-concentration mmu-miR-762 inhibitor induced cell cycle arrest at G0/G1 phase. However, mmu-miR-762 did not cause apoptosis of cells. Western blot analysis showed that mmu-miR-762 mimic transfection upregulated the expression of Wnt-1 and β-catenin, as well as increased the nuclear translocation of β-catenin. Further analysis was performed to demonstrate the correlation of miR-762 with CRC, and blood samples were collected from CRC patients and control donors. The results showed that serum has-miR-762 levels in CRC patients were higher than in control donors. Among the CRC patients (n= 20), six patients with distant metastasis showed higher serum has-miR-762 levels than patients without distant metastasis. Conclusions, the present study suggests that circulating miR-762 might be a potential biomarker for upregulation of CRC cell growth and invasion, and may be accompanied by the Wnt/β-catenin signaling.
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