Quantitative monitoring of the PRAME gene for the detection of minimal residual disease in leukaemia

Abstract

Summary. PRAME (Preferentially expressed antigen of melanoma) has been previously identified as a melanoma antigen recognized by cytotoxic T cells (CTLs) and found to be expressed in a variety of cancer cells including leukaemic cells. We have screened 98 Japanese patients with leukaemia and lymphoma for expression of the PRAME gene using semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Forty-one patients (42%) showed high levels of PRAME expression. Eight of these patients were then monitored using real-time PCR for a period of 10±37 months. Significant reductions in the PRAME expression were observed in all patients after chemotherapy. An increased expression was detected in the two patients who relapsed, one of which was before cytological diagnosis. These changes were correlated with those of other known genetic markers, such as the bcr-abl gene. Therefore, quantitative monitoring of the PRAME gene using real-time PCR method may be useful for detecting minimal residual disease and to predict subsequent relapse, especially in patients without known genetic markers. In addition, a PRAME-positive leukaemia cell line and fresh leukaemic cells were found to be susceptible to lysis by PRAME-specific CTLs established from a patient with melanoma, suggesting that the PRAME peptide can also be a target leukaemia antigen for T cells.

Cancer‐testis antigen expression and its epigenetic modulation in acute myeloid leukemia

“…PRAME, which was first described in 1997 by Ikeda et al [36], has previously been shown to be expressed in 35-64% of AML patients [29,30,[37][38][39]. On the other hand, we have shown here that PRAME is absent from non-malignant hematopoetic cells, which is in line with our previous analysis of a panel of 23 healthy tissues including PBMC, BM samples, and CD341 progenitor cells from healthy donors [16].…”

Evaluation of candidate control genes for diagnosis and residual disease detection in leukemic patients using ‘real-time’ quantitative reverse-transcriptase polymerase chain reaction (RQ-PCR) – a Europe against cancer program

“…The choice of a CG remains a crucial issue and a consensus has still to be found. 14 To date, numerous CGs for MRD detection by RQ-PCR are still used: Abelson gene (ABL), [16][17][18][19][20] beta-actin gene (ACTB), 21,22 beta-2-microglobulin (B2M), 16,23,24 glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH), 16,22,25 porphobilinogen deaminase gene (PBGD), 26 transcription factor IID gene (TBP), 27 and 18S rRNA. 28 Inclusion of CG analysis should significantly enhance the reliability of MRD detection in leukemic patients.…”

What do we mean by sensitivity when we talk about detecting minimal residual disease?

“…Flow cytometry or real-time PCR for leukemia-associated genes (WT1, PRAME and others) always give a certain amount of positivity in leukemiafree samples (Lapillone et al; 3 Steinbach et al; 4 Matsushita et al; 5 Kern et al; 6 San Miguel et al; 8 Venditti et al; 9 and others). Therefore, the relevant question is what is the lowest proportion of leukemic cells that gives a test result that is higher than the one in any healthy bone marrow?…”

“…This was performed in a number of studies for flow cytometry (Kern et al; 6 San Miguel et al; 8 Venditti et al; 9 and others) and also for leukemia-specific genes (Lapillone et al; 3 Steinbach et al; 4 Matsushita et al; 5 …”

“…They depend on the copy numbers of the leukemia-associated genes (WT1, PRAME and others [3][4][5] ) that are used for PCR or the quality of the leukemiaassociated phenotypes that are used for flow cytometry. 6 Therefore, any statement on the quality of a method of monitoring MRD should include the following data: the threshold that is used for clinical decision-making, sensitivity, specificity and the proportion of patients for whom this level of quality can be achieved.…”