Circulating microRNAs as blood-based markers for patients with primary and metastatic breast cancer

Abstract

Introduction: MicroRNAs (miRs) are interesting new diagnostic targets that may provide important insights into the molecular pathogenesis of breast cancer. Here we evaluated, for the first time, the feasibility and clinical utility of circulating miRs as biomarkers for the detection and staging of breast cancer.

Methods: The relative concentrations of breast cancer-associated miR10b, miR34a, miR141 and miR155 were measured in the blood serum of 89 patients with primary breast cancer (M0, n = 59) and metastatic disease (M1, n = 30), and 29 healthy women by a TaqMan MicroRNA Assay.

Results: The relative concentrations of total RNA (P = 0.0001) and miR155 (P = 0.0001) in serum significantly discriminated M0-patients from healthy women, whereas miR10b (P = 0.005), miR34a (P = 0.001) and miR155 (P = 0.008) discriminated M1-patients from healthy controls. In breast cancer patients, the changes in the levels of total RNA (P = 0.0001), miR10b (P = 0.01), miR34a (P = 0.003) and miR155 (P = 0.002) correlated with the presence of overt metastases. Within the M0-cohort, patients at advanced tumor stages (pT3 to 4) had significantly more total RNA (P = 0.0001) and miR34a (P = 0.01) in their blood than patients at early tumor stages (pT1 to 2).

Conclusions: This pilot study provides first evidence that tumor-associated circulating miRs are elevated in the blood of breast cancer patients and associated with tumor progression.

Figure 1

MiR expression in breast cancer cell lines as determined by quantitative real-time PCR. Basal expression levels of miR10b (A), miR34a (B), miR141 (C) and miR155 (D) in breast cancer cell lines MDA-MB-231 and GI-101, and micrometastatic breast cancer cell lines BC-M1 and BC-S1. The relative transcript levels of the miRs were determined by the low cycle threshold (Ct) values.

Figure 2

Levels of total RNA and miRs in blood of breast cancer patients and healthy controls. The box plot and the additionally integrated box plot of miR141 show the different, relative amounts of total RNA, miR10b, miR34a, miR141 and miR155 which circulate in blood of healthy individuals (n = 29), M0 patients (n = 59) and M1 patients (n = 30). The relative transcript levels of miRs were determined by the low cycle threshold (Ct) values. As determined by Mann and Whitney-U test, the significant P-values of the statistical evaluations of serum RNA and miR levels are indicated above the blots.