Prognostic impact of the number of viable circulating cells with high telomerase activity in gastric cancer patients: A prospective study

The identification of circulating tumor cells (CTCs) in peripheral blood is a useful approach to estimate prognosis, monitor disease progression and measure treatment effects in several types of malignancies. We have previously used OBP-401, a telomerase-specific, replication-selective, oncolytic adenoviral agent carrying the green fluorescent protein (GFP) gene. GFP-positive cells (GFP(+) cells) were counted under a fluorescence microscope. Our results showed that the number of at least 7.735 mu m in diameter GFP(+) cells (L-GFP(+) cells) in the peripheral blood was a significant marker of prognosis in gastric cancer patients. However, tumor cells undergoing epithelial-mesenchymal transition (EMT) have been reported to be smaller in size than cells without EMT features; thus, CTCs undergoing EMT may escape detection with this technique. Therefore, in this study, we analyzed the relationship between patient outcome and the number of GFP(+) cells of any size. We obtained peripheral blood samples from 65 patients with gastric cancer. After infection of OBP-401, GFP(+) cells were counted and measured. The relationship between the number of GFP(+) cells and surgical outcome was analyzed. The median follow-up period of the surviving patients was 36 months. A significant difference in overall survival was found between patients with 0-5 and patients with >= 6 L-GFP(+) cells. No clear relationship was established between the number of small-sized GFP(+) cells and patient prognosis. The number of L-GFP-E cells was significantly related to overall survival in patients with gastric cancer. The detection of L-GFP(+) cells using OBP-401 may be a useful prognostic marker in gastric cancer.