Abstract:

Background and purpose: Breast cancer is the most common malignancy in women, and it is also the cancer with the highest number of new cases worldwide in 2020. Human epidermal growth factor receptor 2 (HER2)-positive breast cancer accounts for approximately 20% of all breast cancers, which indicates higher rate of recurrence and metastasis and a poor prognosis. Therefore, it is of great significance to explore the biomarkers related to HER2-positive breast cancer. This study aimed to investigate the expression of circ-0003910 in HER2-positive breast cancer tissues and cells, and to clarify the effect of circ-0003910 on the migration and invasion of breast cancer cells. Methods: Circular RNA (circRNA) microarray was used to screen circRNA differentially expressed in HER2-positive breast cancer cells, and significantly overexpressed circRNA was selected as the research target. Fluorescence in situ hybridization (FISH) assay was used to detect the subcellular localization of circ-0003910. BaseScope assay was used to analyze the expression and clinical significance of circ-0003910 in breast cancer tissues. Circ-0003910 overexpressed and knockdown breast cancer cells were constructed by transfection of cloned plasmid and siRNA in vitro. The effect of circ-0003910 on the migration and invasion ability of breast cancer cells was detected by transwell assay. The molecular mechanism of circ-0003910 promoting the migration and invasion of breast cancer cells was preliminarily explored by TMT quantitative proteomics techniques. Results: CircRNA microarray analysis showed that a total of 1 843 differentially expressed circRNAs were screened in HER2-positive breast cancer cells (fold change≥2, P<0.05), including 845 upregulated circRNAs and 998 downregulated circRNAs. Compared with normal breast epithelial cells, the differential expression ratio of circ-0003910 in HER2-positive breast cancer cells was 24.39. Real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) results showed that the expression of circ-0003910 was higher in HER2-positive breast cancer cells than in other molecular types of breast cancer cells, and BaseScope assay verified that circ-0003910 was mainly located in the cytoplasm of HER2-positive breast cancer tissue cells. Overexpression of circ-0003910 promoted the migration and invasion of breast cancer cells, while circ-0003910 knockdown produced the opposite effects. Proteomics identification showed that 197 proteins were changed after overexpression of circ-0003910, of which 104 proteins were upregulated and 93 proteins were downregulated. GO and KEGG enrichment analysis suggested that circ-0003910 may be involved in biological processes such as cell adhesion molecule synthesis, transcriptional dysregulation in cancer, and protein digestion and absorption. Conclusion: Circ-0003910 is upregulated in breast cancer cells and can promote the migration and invasion of breast cancer cells, which may be a new biomarker and target for the treatment of metastatic breast cancer.

Key words: Breast cancer, Circ-0003910, Migration and invasion, Functional enrichment analysis