LIMITATIONS OF REVERSE-TRANSCRIPTASE POLYMERASE CHAIN-REACTION ANALYSES FOR DETECTION OF MICROMETASTATIC EPITHELIAL CANCER-CELLS IN BONE-MARROW

Purpose: This study was designed to evaluate the potential of reverse- transcriptase polymerase chain reaction (RT-PCR) analyses for the dete ction of micrometastatic carcinoma cells in bone marrow (BM). Patients and Methods: The specificity of RT-PCR assays with primers specific f or various tumor-associated and organ-specific mRNA species was examin ed by analysis of 53 BM aspirates from control patients with no epithe lial malignancy, In addition, BM samples from 63 patients with prostat e cancer (n = 53) or breast cancer (n = 10) were analyzed by RT-PCR wi th primers specific for prostate-specific antigen (PSA) mRNA. As a ref erence method, all samples were analyzed simultaneously by on establis hed immunocytochemical assay, using monoclonal antibodies (mAbs) again st cytokeratins (CK) for tumor-cell detection. Results: Seven of eight marker species could be detected in a considerable number of BM sampl es from control patients: epithelial glycoprotein-40 (EGP-40; 53 of 53 samples), desmoplakin I (DPI I; five of five), carcinoembryonic antig en (CEA; five of 19), erb-B2 (five of seven), erb-B3 (six of seven), p rostate-specific membrane antigen (PSM; four of nine), and CK18 (five of seven). Only PSA mRNA was not detected in any of the 53 control BM samples. In serial dilution experiments, the PSA RT-PCR assay was able to detect five LNCaP prostate carcinoma cells in 4 x 10(6) BM cells. CK-positive cells were found in 20 patients (37.7%) with prostate canc er, while PSA mRNA was found in only 15 (28.3%; P = .04). Moreover, de spite the recent observation that PSA is also expressed in mammary car cinomas, none of the 10 CK-positive BM samples were PSA mRNA-positive. Conclusion: Limiting factors in the detection of micrometastatic tumo r cells by RT-PCR are (1) the illegitimate transcription of tumor-asso ciated or epithelial-specific genes in hematopoietic cells, and (2) th e deficient expression of the marker gene in micrometastatic tumor cel ls. (C) 1997 by American Society of Clinical Oncology.