MOLECULAR MONITORING OF TUMOR-CELL CONTAMINATION IN LEUKAPHERESIS PRODUCTS FROM STAGE-IV NEUROBLASTOMA PATIENTS BEFORE AND AFTER POSITIVE CD34 SELECTION

Background. Autologous peripheral blood stem cells (PBSCs) are frequen tly used to reconstitute hematopoiesis following administration oi meg atherapy in children with advanced stage IV neuroblastoma. Some center s prefer the use oi autografts enriched for CD34+ progenitor cells bec ause the positive selection procedure is believed to reduce indirectly tumor cell contamination. Procedure. In this study, we monitored the efficiency of tumor cell purging following CD34 selection in PBSCs fro m seven patients with advanced neuroblastoma by using a highly sensiti ve reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Amplification or tissue-specific mRNA transcript of tyrosine hydroxyla se gene with nested primers enabled the detection of residual neurobla stoma cells with a sensitivity oi one malignant-cell per 10(6) normals . Results. Using this method, contaminating tumor cells were detected in seven of nine leukapheresis products oi the patients. After positiv e immunoselection of CD34+ cells on Ceprate(TM) column, only one of ni ne enriched stem cell fraction still contained tumor cells detectable by RT-PCR. In six cases, PCR positive PBSCs became PCR negative after selection. Conclusions. We conclude that tumor cell contamination may be frequently detected in PBSC harvests oi stage IV neuroblastoma pati ents by sensitive molecular analysis. The load of contaminating malign ant cells might be reduced following CD34 selection. (C) 1998 Wiley-Li ss, Inc.