Serum microRNA-155 in early diagnosis and prognosis of breast cancer

miR-155 regulates the expression of some 147 targets that are implicated in cancer pathways, and its expression has been shown to be up-regulated in breast cancer. Here, the value of serum expression of miR-155 as a non-invasive biomarker for early diagnosis and prognosis of breast cancer was assessed. RNA was extracted from blood samples from 148 patients with breast cancer and 142 control individuals without cancer, and miR-155 expression was measured via fluorescent real-time quantitative PCR and subsequently correlated with patients' clinical characteristics. Patient follow-up was performed for up to 48 months to identify outcomes including recurrence and death. miR-155 expression was up-regulated 2.62-fold in serum of subjects with breast cancer compared to control subjects (t = 11.338; P < 0.001). Relative serum miR-155 expression significantly differed with cancer stage (F = 68.145; P < 0.001), and expression directly increased with advancing cancer stage. Linear regression analysis indicated that miR-155 expression was linearly related to subjects' number of artificial abortions (r = 0.54; P = 0.01), BMI (r = 0.39; P = 0.03), family history of breast cancer (r = 0.62; P = 0.01), and breast cancer stage (r = 0.48; P = 0.02). Subjects with breast cancer with high serum miR-155 expression had a relatively poor prognosis, and a serum miR-155 concentration of 1.24 U/mL was determined to be the optimal critical point for breast cancer diagnosis. Thus, detection of serum miR-155 expression facilitates early diagnosis and prognosis assessment of breast cancer.