Cell free methylated DNA levels of 8 genes (APC, BIN1, BRCA1, CST6, GSTP1, P16, P21 and TIMP3) were significantly higher in the plasma samples from patients with breast cancer in comparison with those from normal controls (P<0.01), while the other two genes BMP6 and ESR-b showed the same tendency but was not significant (P>0.05) (Fig. 2a; Dataset S1). The gene discussed is CST6; the disease is breast cancer.