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

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.