The Diagnostic Value of miR-155 Expression in the Serum of Patients with Breast Cancer According to Molecular Subtypes of Breast Cancer

Background: microRNAs (miRNAs) have been highlighted as potential circulating biomarkers and therapeutic targets for breast cancer (BC). miRNAs have emerged as an extremely promising new class of biomarkers. They have been demonstrated to be remarkably stable in human blood. miR-155 has more than 4 hundred predicted gene targets. The miR-155 plays an essential role in the pathogenesis of breast cancer. The aim of this study was to assess the diagnostic value of miR-155 expression in the serum of patients with breast cancer according to the molecular subtypes of BC. Methods: 90 samples were classified into different groups with respect to their immunohistochemical (IHC) characteristics: estrogen receptor (ER) positive and/or progesterone receptor (PR) positive group (Luminal A), human epidermal growth factor receptor2 (HER2) positive group (as Luminal B), and Triple negative group (TNBC). The complementary DNA (cDNA) was synthesized in line with the guidelines of the Kit Company. A real-time PCR method was performed as the expression assay. Results: A substantial difference was observed between the phrase standard of miR-155 in patients with the molecular subtypes of breast cancer. The subtypes of Luminal A, Luminal B, and TNBC showed respectively 6 fold, 7 fold, and 14 fold increased expression (P < 0.001). Receiver operating characteristic (ROC) analysis revealed that miR-155 had a considerable diagnostic accuracy for Luminal A with area under the curve (AUC) of 0.875 (sensitivity 100%, specificity 68.63%), for Luminal B with AUC of 0.886 (sensitivity 100%, specificity 62.75%), and for TNBC with AUC of 0.982 (sensitivity 100%, specificity 92.16%) Conclusions: The study found that increased mir-155 expression was significantly associated with BC. The study results showed the mir-155 expression has extremely high sensitivity and specificity for the diagnosis of subtypes of breast tumor. Therefore, checking the serum levels of miR-155 expression in patients with breast cancer may be helpful. Yet, more studies are required to investigate this relationship.