DETECTION OF CHIMERIC MESSENGER-RNAS BY REVERSE-TRANSCRIPTASE POLYMERASE CHAIN-REACTION FOR DIAGNOSIS AND MONITORING OF ACUTE LEUKEMIAS WITH 11Q23 ABNORMALITIES

Recurrent translocations involving chromosome band 11q23 are often fou nd in human acute leukemias. Recently, the MLL gene on 11q23 and 10 pa rtner genes involved in these translocations have been cloned and char acterized. We performed a reverse transcriptase-polymerase chain react ion (RT-PCR) to detect the resultant der(11) chimeric mRNAs of the 3 t ypes of 11q23 translocations including t(4;11), t(9;11), or t(11;19), in 14 leukemia patients with MLL gene rearrangements. At diagnosis or relapse, chimeric mRNA could be detected in all of the 4 patients with t(4;11), 2 of 3 with t(9;11), 2 of 3 with t(11;19), and 1 of 4 with u nsuccessful karyotype. In 5 patients, we could monitor minimal residua l disease (MRD) serially through the clinical course. One patient, in whom chi-meric mRNA was detected during complete remission (CR) just a fter the induction chemotherapy, relapsed within 2 months and died, wh ile 2 patients in which chimeric mRNA was not detected remained in CR from 10-23 months. These findings suggest that RT-PCR is a useful appr oach for detecting which partner gene is involved in the translocation and monitoring MRD in patients with MLL gene rearrangement. Nonethele ss, the clinical relevance of MRD evaluation by RT-PCR monitoring rema ins controversial. Long-term and prospective investigation of a larger series of patients is needed to confirm the clinical significance of monitoring MRD by RT-PCR method. (C) 1997 Wiley-Liss. Inc.