Development and Validation of a 3-Plex RT-qPCR Assay for the Simultaneous Detection and Quantitation of the Three PML-RARa Fusion Transcripts in Acute Promyelocytic Leukemia

Rapid diagnosis of acute promyelocytic leukemia (APL) with promyelocytic leukemia-retinoic acid receptor alpha (PML-RARa) contributes to a highly effective therapy with all-trans retinoic acid (ATRA). Real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) is a valuable tool to diagnose APL with PML-RARa. However, a single RT-qPCR analysis, which is laborious and costly, has to be performed in three reactions to determine whether one of the three PML-RARa transcripts is present and to quantify the involved transcript. This paper describes a novel TaqMan MGB probe-based 3-plex RT-qPCR assay in a single reaction to detect simultaneously the three PML-RARa transcripts. Specific primers and probe were designed, and the results were further normalized to the Abelson gene. The detection results for the serially diluted plasmid indicate that the analytical sensitivity was 10 copies per reaction for PML-RARa bcr1, bcr2, and bcr3. A relatively high sensitivity of 10-4 was achieved with this assay when analyzing the bcr1 transcripts obtained from the NB4 cell line. The reproducibility was satisfactory because the coefficients of variation of cycle threshold values were less than 3% for both inter- and intra-assays. After testing 319 newly diagnosed patients with leukemia (including 61 APL cases), the results of the 3-plex RT-qPCR assay completely agreed with the traditional methods used for the detection of PML-RARa. The quantitative results of the 3-plex RT-qPCR were highly correlated with the single RT-qPCR and showed similar assay sensitivity for 60 PML-RARa positive APL samples at diagnosis and 199 samples from 57 patients during follow-up. Interestingly, one PML-RARa bcr2 case at diagnosis with breakpoint at 1579, which was not detected by the single RT-q-PCR, was detected by the 3-plex RT-qPCR assay. The 3-plex RT-qPCR assay is a specific, sensitive, stable, and cost-effective method that can be used for the rapid diagnosis and treatment monitoring of APL with PML-RARa.