Regulation of CDK inhibitor p27 by microRNA 222 in breast cancer patients

Breast cancer is the most common of all cancers and the second leading cause of cancer-related deaths among women worldwide. MicroRNAs regulate at least 60% of the human genes, including tumor suppressor genes and oncogenes, and can thereby affect cancer risk. In this study, the prognostic values of the CDK inhibitor p27 and miR-222 as biomarkers for breast cancer were evaluated.

The real-time quantitative polymerase chain reaction method was employed to measure the expression level of miR-222, whereas the serum levels of the CDK inhibitor p27 were measured via enzyme-linked immunosorbent assay. The levels were determined in sera from 110 participants representing three different groups.

Patients with breast cancer exhibited significantly higher expression levels of miR-222 and lower levels of CDK inhibitor p27 than the control group. In addition, a statistically significant inverse correlation between miR-222 and the CDK inhibitor p27 was observed. The receiver operating characteristic curves plotted for serum p27 and miR-222 helped in significantly differentiating between breast cancer patients and controls but could not discriminate between those with stage II and stage III cancer.

Thus, a significant upregulation in the serum miR-222 levels was observed in cancer patients, and a significant inverse correlation was noted between the miR-222 and CDK inhibitor p27 expression levels. These findings indicate that miR-222 may be used as a useful noninvasive screening biomarker for human breast cancer.

Novel biomarkers for prognosis, prediction, and therapeutic purposes are essential as the prognosis and therapeutic targets of breast cancer are dependent on traditional markers, such as the tumor stage and hormonal receptor status. This study aimed to evaluate the diagnostic and prognostic values of the CDK inhibitor p27 and miR-222 in breast cancer. Our results indicated that miR-222 and the CDK inhibitor p27 may be used as noninvasive biomarkers to screen for human breast cancer but cannot discriminate between patients with early breast cancer and patients with advanced breast cancer.