HPRT1 and neuroblastoma: To avoid the inevitable interpretational difficulties caused by genetic heterogeneity of individual patient and normal control samples, we have now examined the transcriptional aberrations in the less complex system of wild type (WT) human fibroblasts and human SH-SY5Y neuroblastoma cells in which HPRT expression is efficiently knocked down by transduction with a retrovirus vector expressing a short hairpin RNA targeted to HPRT.