Bmi-1 mRNA in plasma from breast cancer patients as possible prognosis marker in advanced pathological stages

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PURPOSE: Deregulation of Polycomb member Bmi-1 is involved in cell proliferation and human oncogenesis. Modulation of Bmi-1 is found in several tumor tissues, including primary breast carcinomas; however,analysis of Bmi-1 in plasma of cancer patients has not been reported. This is the first study that evaluates Bmi-1 in plasma by using a large series of primary breast carcinomas to investigate the presence at diagnosis of detectable Bmi-1 mRNA in plasma and possible correlations between this event and a series of clinical pathological parameters of the tumors. MATERIALS AND METHODS: Bmi-1 expression levels were quantified in plasma of 111 breast cancer patients and in 20 healthy controls by Real-Time Quantitative PCR. RESULTS: Cancer patients with presence of Bmi-1 mRNA in plasma had higher levels of Bmi-1 expression than healthy controls with Bmi-1 mRNA in plasma. Higher expression levels of Bmi-1 correlated with well-established markers of poor clinical outcome in breast cancer such as positive p53 immunostaining and negative progesterone receptors. Moreover, we described for the first time a statistically significant correlation between Bmi-1 expression in plasma of breast cancer patients and disease-free and overall survival in advanced stages. CONCLUSIONS: Our results suggest levels of Bmi-1 expression could be a surrogate marker of poor prognosis and become clinically useful as non-invasive diagnostic markers.