Detection of Circulating Mammary Carcinoma Cells in the Peripheral Blood of Breast Cancer Patients Via a Nested Reverse Transcriptase Polymerase Chain Reaction Assay for Mammaglobin mRNA

Abstract

PURPOSE: According to current medical research, mammaglobin (hMAM) is expressed exclusively in the mammary glands of adult women and in mammary tumor cell lines. Therefore, we examined hMAM expression as a marker for the detection of carcinoma cells in the peripheral blood of patients with breast cancer (BC). PATIENTS AND METHODS: Blood samples obtained from 114 BC patients at the various stages of their disease and from 68 individuals without BC were screened for hMAM mRNA by a nested reverse transcriptase polymerase chain reaction (RT-PCR) assay. RESULTS: The assay exhibited a calculated analytical limit of one tumor cell per 106 to 107 WBCs. None of the samples from peripheral blood of 27 healthy individuals were positive, whereas 29 (25%) of 114 samples from BC patients were positive for hMAM mRNA. hMAM mRNA expression was detected in five (28%) of 18 BC patients at diagnosis, in three (6%) of 53 with no evidence of disease, and in 21 (49%) of 43 with metastatic disease. These results correlate with patients' carcinoembryonic antigen (CEA) plasma level and, to some extent, with estrogen receptor status. Two of 41 samples from patients with malignancies other than BC were also positive. CONCLUSION: In contrast to healthy volunteers, hMAM transcripts were detected in the peripheral blood of BC patients. The percentage of positivity relates to the clinical stages of disease, CEA plasma level, and estrogen receptor status. Aberrant hMAM expression might occur occasionally in malignancies other than BC. The clinical relevance of hMAM RT-PCR–based tumor cell detection in the peripheral blood of BC patients should be further evaluated in prospective studies.