Detection of amplifiable messenger RNA in the serum of patients with lung cancer.

Recently, in addition to the detection of circulating tumor cells in peripheral blood of patients with solid tumors, the presence of free circulating nucleic acids in the plasma and serum has also been described. We have focused on the possibility of isolating and amplifying intact extracellular, tumor-related mRNA from the plasma/serum of patients with lung cancer. For this purpose, we established several RT-PCR-based amplification systems for the detection of a panel of five different genes. The expression of these genes was either shown to be restricted to lung tissue or associated with malignancy. We examined two small groups of 18 patients with lung cancer before and during chemotherapy, respectively. The message for beta-actin (control for integrity of the RNA) was detected in all of the analyzed sera from the control group and patients with lung cancer. Analysis of CK-19 expression was positive in the majority of tumor patients, but positive results were also shown in all of the control sera. The expression of MAGE-2 and TTF-1 genes was not observed in any of the patients in either the lymphocyte preparations or serum samples. Expression of the PGP 9.5 gene was observed in the cells of all 18 patients, but mRNA in the serum was only detectable in one case. The hnRNP-B1 mRNA was detectable in 14/18 sera, and Her2/neu-specific mRNA could be amplified from the serum of 7/18 patients. Combining the last two markers, we were able to detect all patients with a malignant lung tumor.