Pitfalls in detection of contaminating neuroblastoma cells by tyrosine hydroxylase RT-PCR due to catecholamine-producing hematopoietic cells

Background: RT-PCR analysis of compounds of catecholamine metabolism (in particular tyrosine hydroxylase, TH) is widely used for the detection of contaminating neuroblastoma cells in hematopoietic stem cell preparations. Due to reports in the literature showing that hematopoietic cells are also able to produce catecholamines, we investigated whether TH-RT-PCR is really suitable for this purpose. Materials and Methods: Besides neuroblastoma cells, mononuclear blood cells, apheresis preparations and hematopoietic stem cells were used for single and nested RT-PCR. In addition to TH, the expressions of dopamine-beta-hydroxylase and noradrenaline transporter were analyzed. Results: Using single RT-PCR, a clear discrimination between neuroblastoma and hematopoietic cells was possible. However, by using nested RT-PCR, the "neuroblastoma markers" were also detected in a significant percentage of non-mobilized motion it clear blood cells, in mononuclear blood cells of healthy donors mobilized with G-CSF, and in highly purified CD34(+) and CD133(+) stem cells from healthy mobilized donors. Conclusion: Our results raise the question of whether the RT-PCR analysis of compounds of catecholamine metabolism is suitable and selective enough to detect the contamination of hematopoietic stem cells by a low, number of neuroblastoma cells.