Detection of white cell chimerism in profoundly leucopaenic patients following allogenic BMT

amplified along with N-myc in 4/6 (67%) cell lines and 6/16(38%) of the N-myc amplified turnouts. Coamplification of DDX1 and Nmye was found more frequently in high stage (4 or 4S) tumours than low stage (1-3) tumours. No amplification of DDX1, ODC, RRM2, or sydecan-1 was found in the absence of N-myc amplification. Patients with DDX1 coamplification tended to have a poorer prognosis than those with N-myc amplification alone although the numbers are too few to achieve statistical significance. These observations indicate that the N-myc amplicon is of varied size and/or position relative to the N-myc gene and that Nmyc is not the only gene on the amplicon, with DDX1 representing at least one other gene frequently coamplified with N-myc. Further studies are required to confirm the bioligical and prognostic significance of DDX1 coamplification and to elucidate the role that DDX1 plays in tumour genesis and progression.