Molecular detection of occult cancer cells in human lung cancer

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The detachment of tumor cells from the primary site and the release of them into the circulation is one of the early events in the metastatic cascade. Although the presence of circulating tumor cells does not necessarily correlate with the subsequent appearance of systemic disease, some such tumor cells may have the potential to establish metastases and so may have a negative influence on patient prognosis. Since the number of circulating cells may be very small, methods for their detection need to be both sensitive and specific. Morphology, flow cytometry, conventional cytogenetics, and immunocytochemistry have been used to detect circulating tumor cells. However, these techniques are relatively insensitive and dependent upon the interaction of antibodies with tumor-associated cell-surface antigens. These methods may yield false-positive results if the antibodies cross-react with normal antigens or if the tumor antigens are presented on host immune cells. Recent developments in molecu … More lar technology including the advent of the polymerase chain reaction (PCR) have permitted the sensitive detection of circulating tumor cells in the peripheral blood. Several researchers have used carcinoembryonic antigen (CEA) as the target gene because CEA mRNA can be detected in almost all epithelial cells, including cancer cells, but not in non-epithelial cells. The reverse transcriptase-polymerase chain reaction (RT-PCR) amplification method for CEA mRNA is an efficient means of detecting circulating cancer cells in the peripheral blood. If CEA mRNA is detected in blood samples, this implies the presence of ectopic epithelial cells, and hence presumably cancer cells. Patients with positive CEA mRNA in the preoperative blood samples had a poor survival when compared to those with negative CEA mRNA ; of these patients, the worst survival rate was seen in those with positive CEA mRNA in the postoperative blood samples. The molecular detection of CEA mRNA in the preoperative peripheral blood is an independent prognostic factor in patients with lung cancer who undergo a curative surgery. Less