DETECTION OF METASTATIC BREAST-CANCER BY BETA-HCG POLYMERASE CHAIN-REACTION

Reverse transcriptase-polymerase chain reaction (RT-PCR) for detection of occult malignancies in breast cancer patients is evolving as a use ful diagnostic tool. However, no reliable molecular mRNA markers are a vailable. We developed an RT-PCR plus Southern blot assay using beta-h CG (beta-subunit of human chorionic gonadotropin) gene expression as a tumor marker for detection of breast malignancies metastatic to tumor -draining lymph nodes and blood. Breast carcinoma cell lines, primary breast malignancies and human placenta were used as positive controls for establishing the beta-hCG RT-PCR assay. Peripheral blood leukocyte s (PBL) from normal volunteer donors, normal breast tissue and lymph n odes from cancer-free patients were used as negative controls. beta-hC G RT-PCR was used to assess tumor cell presence in PBL and tumor-drain ing axillary nodes from patients with AJCC stage I-IV breast cancer. T he assay sensitivity and specificity were enhanced by restriction endo nuclease digestion of an Sty I site of the RT-PCR cDNA product followe d by Southern blot analysis. beta-hCG mRNA was expressed in all breast cancer cell lines and 80% of primary breast cancers; it was not expre ssed in negative controls. The assay reliably detected one cancer cell in > 10(7) PBL, with a sensitivity of 10(-5) mu g RNA. Eighty percent of PBL and 61% of tumor-draining axillary nodes from breast cancer pa tients expressed beta-hCG mRNA. The assay is a sensitive and specific method of identifying breast cancer cells in breast tissues, lymph nod es and blood. (C) 1996 Wiley-Liss, Inc.