PRAME mRNA levels in cases with acute leukemia: clinical importance and future prospects.

The PRAME (preferentially expressed antigen of melanoma) gene has been shown to be expressed in high levels in some solid tumors and hemopoietic neoplasias but not or only weakly expressed in normal tissues. It encodes an antigen recognized by autologous cytolytic T lymphocytes. PRAME is a good candidate for tumor immunotherapy and is a useful marker gene for detection of minimal residual disease (MRD). In this study, PRAME mRNA using real-time RT-PCR was studied in 74 adult cases with acute leukemia-68 had de-novo acute leukemia, 3 had chronic myeloid leukemia-blastic crisis (CML-BC), and 3 had myelodysplastic/myeloproliferative syndrome-blastic transformation (MDS/MPD-BT)-and the results were compared with 30 age-matched healthy volunteers. Nineteen of 74 cases with leukemia expressed PRAME, while only 2 controls showed weak expression. The prevalence of PRAME expression in AML and ALL cases was 30% and 17%, respectively. We did not find any important correlation between PRAME expression and clinical characteristics, such as age, sex, organomegaly/lymphadenopathy, Hb, WBC count, platelet count, LDH level, alkaline phosphatase, albumin, cell-surface antigens, response to therapy, or progression-free and overall survival. PRAME was monitored in 15 cases during remission and/or relapse. There was a good correlation between PRAME mRNA and hematological remission and/or relapse. Interestingly, PRAME was very high in one case with AML but was not found 3 months after allogeneic transplantation. PRAME mRNA is observed in about one-third of AML cases; it may be a useful marker to detect MRD, and it may also be a good predictor for the timing of donor lymphocyte infusions (DLI) in the post-transplant period in cases of molecular relapse. Copyright (c) 2005 Wiley-Liss, Inc.