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RT-PCR method with increased sensitivity shows persistence of PML-RARA fusion transcripts in patients in long-term
1University Department of Haematology, Manchester Royal Infirmary, UK.
Abstract:
RT-PCR methods have been developed, to date, by various groups to amplify the PML-RARA fusion gene produced by the t(15;17) in APL patients. However, these methods lack the necessary sensitivity to detect minimal residual disease (MRD) below the level of 1 leukaemic cell in 10(4) cells. Patients who test positive by these methods after treatment are likely to relapse. However, up to 25% of patients who test negative after treatment relapse within a short period. We have developed a 'hot-start' RT-PCR method for the amplification of PML-RARA with increased sensitivity at the level of two leukaemic cells in 10(6) cells. Using this method we were able to detect MRD in seven out of 15 patients tested in remission. Of the 11 patients in medium to long-term remission, five patients tested positive. None of these 11 patients tested positive with the standard RT-PCR. These results show that some patients in remission of APL continue to express PML-RARA even in long-term remission, when they can be considered clinically 'cured' of their disease.
Insights
A new
Area of Science:
- Hematology
- Molecular Biology
- Oncology
Background:
- Standard RT-PCR methods for detecting the PML-RARA fusion gene in Acute Promyelocytic Leukemia (APL) patients lack the sensitivity to identify minimal residual disease (MRD).
- Current methods can miss low-level disease, leading to potential relapse in patients who test negative post-treatment.
- A significant percentage of APL patients (up to 25%) who test negative for MRD still relapse, indicating limitations in current detection techniques.
Purpose of the Study:
- To develop a more sensitive RT-PCR method for detecting the PML-RARA fusion gene.
- To improve the detection of minimal residual disease (MRD) in Acute Promyelocytic Leukemia (APL) patients.
- To assess the persistence of PML-RARA expression in APL patients in remission.
Main Methods:
- Development of a 'hot-start' RT-PCR technique for amplifying the PML-RARA fusion gene.
- Increased sensitivity achieved to detect two leukaemic cells in 10(6) cells, a significant improvement over previous methods.
- Testing of the new method on APL patients in various stages of remission.
Main Results:
- The enhanced 'hot-start' RT-PCR method demonstrated significantly increased sensitivity for PML-RARA detection.
- MRD was detected in seven out of 15 APL patients who were in remission.
- Five out of 11 patients in medium to long-term remission tested positive for PML-RARA using the new method, while all tested negative with standard RT-PCR.
Conclusions:
- The developed 'hot-start' RT-PCR method offers superior sensitivity for detecting minimal residual disease in APL.
- Persistent PML-RARA expression can be detected in some APL patients even in long-term remission, challenging the definition of clinical cure.
- This sensitive method is crucial for accurate MRD assessment and potentially for refining treatment strategies in APL.