RT-PCR method with increased sensitivity shows persistence of PML-RARA fusion transcripts in patients in long-term remission of APL

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 10⁴ 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 10⁶ 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.