Examining the miR-93-5p and miR-17-5p Expression in Plasma and Breast Cancer Tissue as Possible Markers in Breast Cancer Prognosis

MicroRNAs (miRNAs) are a class of small non-coding RNAs (17-25 nucleotides) that have been studied in many diseases. miRNAs studies in different cancers have shown that miRNAs may be considered oncogene or tumor suppressor. So far, many studies have shown that miR-17-5p and miR-93-5p are important regulatory molecules in some biological processes, such as cell proliferation, associated with cancer formation. This study aimed to investigate and compare the tissue and plasma expression levels of miR-17-5p and miR-93-5p in patients with ductal carcinoma breast cancer with the normal control group.

The total RNA (including miRNA) was extracted from breast and plasma tissue samples of cancerous and normal samples. The RNA concentration and purity were confirmed using optical absorbance measurements. cDNA was synthesized, and the expression levels of miR-17-5p and miR-93-5p were assessed semi-quantitatively by SYBR Green-based real-time RT-PCR assay in plasma and breast tissues of ductal carcinoma breast cancer compared with the control normal samples with SNORD47 as internal normalizer. Data were statistically evaluated using GraphPad Prism 8.0.2.

This study was approved by the Ethics Committee of the institute (IRAN 52d/4922, 6.10.2016). All study individuals signed a consent form to use their clinical samples and personal data under the physician’s supervision.

The expression level of miR-17-5p showed significantly higher expression in tissues and plasma of the cancer group compared with the control group (P<0.0001). It was also significantly associated with tumor stage and lymph node, and ER (estrogen receptor) and PR (progesterone receptor) status (P<0.0001). While decreased expression of miR-93-5p in plasma and tumor tissues was shown to be significantly associated with tumor stage and lymph node involvement (P<0.0001).

The data revealed that high expression of miR-17-5p and low expression of miR-93-5p in both plasma and breast tumor might be associated with poor prognosis in breast cancer. However, miR-17-5p, due to the greater change in expression and ease of plasma detection, may serve as a possible non-invasive biomarker for breast cancer’s poor prognosis. Further follow-up studies are required to confirm this finding.