Background: Specific gene rearrangements are used for minimal residual disease (MRD) assessment, but are frequently lacking in leukaemias. In these cases, the quantification of PRAME (preferentially expressed antigen of melanoma) transcripts could be useful.
Methods: PRAME transcripts were quantified by real-time RT-PCR in normal and leukaemic samples, and the results were compared with those of conventional RT-PCR. Basal expression of PRAME was determined in 25 blood samples and 25 bone marrow samples from healthy donors, as well as in 12 haematological cell lines (Jurkat, K562, HL60, DOHH2, IM9, Daudi, CEM, KG1, DG75, 8226, U937, Raji).
Results: In paediatric acute myeloid leukaemia (AML) (n=22) and acute lymphoblastic leukaemia (ALL) (n=17), and in adult AML (n=20), abnormal PRAME expression was found in 41%, 35% and 40% of cases, respectively. To assess the sensitivity of PRAME for monitoring MRD, PRAME-positive t(8;21) AML samples with detectable AML1/ETO expression by conventional RT-PCR (n=17) were assessed for quantitative expression of AML1/ETO and PRAME. The expression of these genes was closely correlated. To confirm that PRAME expression was correlated with clinical data, the expression of PRAME was also sequentially followed in patients (n=13) from onset to cytological remission or relapse. The cytological and molecular data were highly correlated in all patients.
Conclusions: Our data confirm that PRAME quantification by real-time RT-PCR appears suitable for monitoring MRD in PRAME-positive leukaemia.