Sensitive detection of micrometastases in bone marrow from patients with breast cancer using immunomagnetic isolation of tumor cells in combination with reverse transcriptase/polymerase chain reaction for cytokeratin-19

Abstract

We report a highly sensitive method to detect rare human breast cancer cells, which combines an immunomagnetic separation (IMS) using antibody BM2 against MUC-1 with cytokeratin-19 (CK19) and the reverse transcriptase/polymerase chain reaction (RT-PCR). The IMS-RT-PCR technique allows the detection of 1 tumor cell/10⁷–10⁸ mononuclear cells. This is at least ten times more sensitive than CK19 RT-PCR alone, or immunocytochemistry. All 117 peripheral blood and 8 bone marrow samples obtained from healthy donors as negative controls were positive for β2-microglobulin by RT-PCR but negative for CK19 by IMS-RT-PCR or RT-PCR alone. Out of 26 bone marrow samples from breast cancer patients, 18 had CK19 transcripts detectable by IMS-RT-PCR. In contrast, only 14 and 13 samples from the 26 were found to be positive by RT-PCR alone or by routine immunocytochemical staining. In conclusion, IMS-RT-PCR for CK19 is a highly sensitive and specific method for detecting very low numbers of micrometastatic breast cancer cells in bone marrow amidst an excess of non-malignant cells. For the early diagnosis of disseminating disease, this assay is more efficient than RT-PCR alone and routine immunocytochemistry.