[Monitoring bcr-abl mRNA levels by real-time quantitative RT-PCR in chronic myeloid leukemia patients after hematopoietic stem cell transplantation].

Objective To evaluate the value of real time quantitative RT-PCR(Q-PCR)for monito- ring ber-abl mRNA levels in chronic myeloid leukemia(CML)patients after allogeneic hematopoietic stem cell transplantation(allo-HSCT).Methods Quantification of ber-abl mRNA was performed on 316 hone marrow samples from 112 patients with CML after HSCT by Q-PCR using the TaqMan probe system.The ber- abl mRNA level was normalized hy control gene abl.Cytogenetic response was evaluated with fluorescent in- situ hybridization(FISH).Results The reproducible sensitivity of Q-PCR was 5 copies.The coefficients C_r of interassay and intraassay variation for abl and ber-abl were all below 2.0%.289 bone marrow samples were collected from 101 CML patients who achieved a sustained complete cytogenetic response(CCyR)one month post allo-HSCT in a period of 6～60 months(median 12 months)at different intervals.In general,the median ber-abl levels gradually decreased with the prolongation of time alter HSCT:the median ber-abl levels were 0.035%(0～0.406%)at 1 month post allo-HSCT(+1 month),0.006%(0～0.683%)at +3 month, 0%(0～0.225%)at +6 month and remained 0% till +24 months.The highest level in CCyR patients de- tected at +6 month was 0.068%.The ber-abl mRNA level was deereased by 3 log in sustained CCyR pa- tients at +1 month compared with the newly diagnosed CML-CP patients(33.0%,data unpublished).On the contrary,Q-PCR results ranged from 0.12% to 13.45% in 8 cytogenetiv non-responders or relapsed pa- tients post allo-HSCT.Among them,5 patients' samples were collected 1～2 months before cytogenetic re- lapse,the results were ranged from 0.09% to 3.42%.If 0.09% was assumed 0.09% as a threshold,9 sus- tained CCyR patients(8.9%)were tested once higher than that within 6 month after HSCT but decreased to 0% eventually.2 blast crisis patients achieved CCyR within 1.6 and 3 months,after HSCT,but hematological relapse occurred after 1 and 1.5 months,and their bcr-abl mRNA levels increased dramatically from 0% and 0.14% to 46.9% and 75.9% respectively.Conclusions Q-PCR is a sensitive,precise and reliable tech- nique,and can be used to monitor CML patients post allo-HSCT regularly.Patients in blast phase of CML should be monitored more frequently.