QUANTITATIVE-ANALYSIS OF AML1 ETO TRANSCRIPTS IN PERIPHERAL-BLOOD STEM-CELL HARVESTS FROM PATIENTS WITH T(8-21) ACUTE MYELOGENOUS LEUKEMIA/

Peripheral blood stem cells (PBSC) have been used increasingly for hae mopoietic reconstitution after marrow-ablative chemotherapy in patient s with acute leukaemia because of the possibility that there is a lowe r risk of leukaemic contamination, We have developed a titration assay using a competitive reverse transcriptase polymerase chain reaction ( RT-PCR) which is able to estimate the number of AML1/ETO transcripts s o that minimal residual disease (MRD) can be monitored quantitatively in patients with t(8;21) acute myelogenous leukaemia (AML). Using a qu alitative RT-PCR method, AML1/ETO transcripts could be detected in all samples from 15 first PBSC harvests and 11 second PBSC harvests obtai ned from 15 patients with t(8;21) AML, With our competitive RT-PCR ass ay, the number of AML1/ETO transcripts was found to be lower in the se cond PBSC harvest than that in the first in every individual, Furtherm ore, MRD in PBSC harvests was less than that in the corresponding bone marrow obtained on the day of PBSC collection in the individual patie nts studied. In 10 patients who received autologous blood stem cell tr ansplantation (ABSCT), we could not find a relationship between the nu mber of AML1/ETO transcripts in the infused PBSC harvests and the clin ical outcome after ABSCT. The present: study clearly indicates that al though PBSC harvests collected after consolidation chemotherapy are co ntaminated by leukaemic cells, the degree of leukaemic contamination m ay decrease as chemotherapy is repeated, The mobilization of PBSC by r epeated chemotherapy may provide an advantageous source of haemopoieti c stem cells for ABSCT.