Profiling mRNA and miRNA expression variations associated with cyclin-dependent kinase pathway in the low-grade luminal early breast cancer.

Luminal A and B subtypes of breast tumors have fluctuated in proliferation rates, which arise from cell cycle dysregulation in cancer. Besides, microRNAs can regulate various cell processes through integration with mRNA. miRNAs that target the cell cycle are significant because of their prediction capability of prognosis. The objective of this study is to discover the integration between miRNA-mRNA and miRNA-miRNA related to cyclin-dependent kinase. Thirty-four pairs of human primary breast cancer and tumor margin samples from luminal breast cancer patients were investigated to assess the expression levels of CCND1, E2F1, miR-124, miR-503, miR-449a, and miR-449b. Afterward, the expression levels of mRNAs and miRNAs were investigated by real-time PCR. Statistical analysis was conducted to compare the expression levels between breast cancer and corresponding normal tissues. The protein expressions of E2F1 and CCND1 were verified by western blotting. Further, the correlation between mRNAs and miRNAs was calculated. E2F1 was significantly increased in both luminal A and B patients, while CCND1 was upregulated only in luminal B. Significant differences in all miRNAs were detected in both luminal A and B biopsy specimens (p < 0.0001). The correlation analysis revealed a positive strong correlation between miR-124 and E2F1 in luminal A patient. Moreover, the correlation test confirmed the ability of miR-449a to increase the CCND1 gene in luminal B subtypes. Also, miRNA correlation exhibited the miRNA-miRNA interaction in luminal breast cancer. This study demonstrated the novel miRNA-mRNA and miRNA-miRNA interactions, providing new insights into the molecular integration in luminal A and B patients. The authors propose that this research could contribute to introducing valuable biomarkers for luminal cancerous cells.