miRNA-1260b Promotes Breast Cancer Cell Migration and Invasion by Downregulating CCDC134

Background: Breast cancer (BRCA) is the most common type of cancer among women worldwide. MiR-1260b has been widely demonstrated to participate in multiple crucial biological functions of cancer tumorigenesis, but its functional effect and mechanism in human breast cancer have not been fully understood.

Methods: qRT-PCR was used to detect miR-1260b expression in 29 pairs of breast cancer tissues and normal adjacent tissues. Besides, the expression level of miR-1260b in BRCA cells was also further validated by qRT-PCR. miR-1260b played its role in the prognostic process by using Kaplan-Meier curves. In addition, miR-1260b knockdown and target gene CCDC134 overexpression model was constructed in cell line MDA-MB-231. Transwell migration and invasion assay was performed to analyze the effect of miR-1260b and CCDC134 on the biological function of BRCA cells. TargetScan and miRNAWalk were used to find possible target mRNAs. The relationship between CCDC134 and immune cell surface markers was analyzed using TIMER and database and the XIANTAO platform. GSEA analysis was used to identify possible CCDC134-associated molecular mechanisms and pathways.

Results: In the present study, miR-1260b expression was significantly upregulated in human breast cancer tissue and a panel of human breast cancer cell lines, while the secretory protein coiled-coil domain containing 134 (CCDC134) exhibited lower mRNA expression. High expression of miR-1260b was associated with poor overall survival among the patients by KM plot. Knockdown of miR-1260b significantly suppressed breast cancer cell migration and invasion and yielded the opposite result. In addition, overexpression of CCDC134 could inhibit breast cancer migration and invasion, and knockdown yielded the opposite result. There were significant positive correlations of CCDC134 with CD25 (IL2RA), CD80 and CD86. GSEA showed that miR-1260b could function through the MAPK pathway by downregulating CCDC134.

Conclusion: Collectively, these results suggested that miR-1260b might be an oncogene of breast cancer and might promote the migration and invasion of BRCA cells by down-regulating its target gene CCDC134 and activating MAPK signaling pathway as well as inhibiting immune function and causing immune escape in human breast cancer.