Detection of MUC1-expressing mammary carcinoma cells in the peripheral blood of breast cancer patients by real-time polymerase chain reaction

We have prospectively analyzed blood samples of 122 patients with breast di sease for the presence of circulating expressing MUC1 cells before and afte r treatment. Among them, 28 patients had histologically confirmed benign br east disease (group 1), 34 patients had operable breast cancer (group 2), a nd 60 patients had advanced breast cancer (group 3), Circulating epithelial cells were isolated with BerEP4-coated immunomagnetic beads, Total RNA was extracted and reverse transcribed before analysis by real-time PCR of a MU C1-specific cDNA sequence, The sensitivity of the reverse transcription-PCR tested with blood spiked w ith MCF7 cells was one cell in 5 mi of blood, The immunomagnetic separation step was mandatory to obtain the maximum specificity. Control samples from healthy donors never displayed cycle threshold (Ct) values for MUC1 lower than 38, Circulating cells (Ct, <38) were detected in 3 of 28 (11%) cases i n group 1, in 8 of 34 (24%) cases in group 2, and in 27 of 60 cases (45%) i n group 3, A semiquantitative estimate of blood-borne cells could be derive d from the Ct value when below 32 (the lowest was 28) or by the number of p ositive aliquots of the same blood sample, Thus, immunomagnetic separation, followed by MUC1-specific RT-PCR, allows the semiquantitative detection of circulating mammary cells. A significant correlation between the presence of MUC1-positive cells and the group of breast tumors was observed. The cli nical significance of blood-borne cells in breast cancer, especially at the operable stage, may be investigated by following these patients.