Sensitive detection of rare cancer cells in sputum and peripheral blood samples of patients with lung cancer by preproGRP-specific RT-PCR

RT-PCR-based amplification of transcripts expressed in cancer but not in no rmal non-neoplastic cells is increasingly used for the sensitive detection of rare disseminated or exfoliated cancer cells to improve cancer staging a nd early detection protocols. However, these assays are frequently hampered by false-positive test results due to tow-level transcription of the marke r genes in normal cells. To overcome these limitations, target transcripts have to be identified that are tightly suppressed in normal non-neoplastic tissues, whereas they should be actively transcribed in the respective canc er cells. Here, we tested RT-PCR assays for 7 neuroendocrine marker transcr ipts including NCAM, PGP 9.5, gastrin, gastrin receptor, synaptophysin, pre progastrin-releasing peptide (preproGRP) and GRP-receptor to detect rare ex foliated tumor cells in peripheral venous blood and sputum samples from pat ients with lung cancer. Among these preproGRP RT-PCR was the only assay wit h which illegitimate transcription in blood or sputum samples from healthy donors or patients with unrelated diseases did not interfere. However, it r eproducibly detected up to 10 small-cell lung cancer cells diluted in eithe r 10 mi blood or 5 mt sputum samples. Single blood and sputum samples were collected directly before diagnostic bronchoscopy from 175 patients suspect ed to have lung cancer. Twenty-six of these had small-cell lung cancer (SCL C). Thereof, 13 patients (50%) tested positive in the blood sample and 5 of 23 patients (22%) tested positive in the sputum sample. Moreover, among 92 patients with non-small-cell lung cancer (NSCLC) 25 patients (27%) had dis seminated cancer cells in peripheral blood, Amplification of preproGRP tran scripts from clinical samples is a sensitive and specific assay to detect d isseminated or exfoliated lung cancer cells either in peripheral blood or s putum samples, (C) 2001 Wiley-Liss, Inc.