Quantitative PCR Detection of PML-RARA Fusion Transcripts in Acute Promyelocytic Leukemia (APL)

The TRUPCR® PML-RARA Quantitative Kit is a real-time RT-PCR-based in vitro diagnostic assay developed for the qualitative and quantitative detection of PML-RARA fusion transcripts in patients with acute promyelocytic leukemia (APL or AML-M3). This multi-tube assay detects and differentiates the three main fusion isoforms—long (bcr1), variant (bcr2), and short (bcr3)—originating from the t(15;17) chromosomal translocation. The kit also amplifies the ABL gene as an internal control for RNA quality and normalization.

This assay provides sensitive, isoform-specific quantification, and is the first commercial kit to accurately differentiate 5’ and 3’ breakpoints within bcr2, making it a valuable tool for diagnosis, treatment prediction, and minimal residual disease (MRD) monitoring in APL.

Molecular Background

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML), characterized by a reciprocal translocation between chromosomes 15 and 17—t(15;17)—which results in the fusion of the PML gene on chromosome 15 with the RARA gene on chromosome 17. This genetic alteration is found in approximately 99% of APL patients and is a keydiagnostic marker.

Depending on the breakpoint within the PML gene, three different PML-RARA fusion transcripts can form:

• BCR1 (long form): Breakpoint in intron 6 (~50–55% of cases)
• BCR3 (short form): Breakpoint in intron 3 (~30–40% of cases)
• BCR2 (variant form): Breakpoint in exon 6 (~5–10% of cases)

The exact location of these breakpoints may impact prognosis and response to treatment. Some studies suggest that BCR3 is associated with shorter remission durations, while certain BCR2 subtypes may show reduced sensitivity to all-trans retinoic acid (ATRA).

Therefore, accurate differentiation and quantification of these isoforms not only aids in diagnosis and classification but also supports treatment planning and MRD tracking.

Assay Performance & Utility

The TRUPCR® PML-RARA Quantitative Kit enables sensitive detection and quantification of bcr1, bcr2, and bcr3 isoforms in a single workflow. The assay is ideal for:

• Diagnosis of APL via t(15;17) detection
• Monitoring treatment response and MRD
• Predicting ATRA therapy response based on isoform type
• Longitudinal disease tracking post-therapy or transplantation

Its multi-tube design allows independent amplification and clear identification of each isoform while ensuring high specificity and reproducibility.

Technical Specifications

• Assay Type: Real-time RT-PCR (quantitative)
• Target Transcripts: PML-RARA bcr1 (long), bcr2 (variant), bcr3 (short)
• RNA Control Gene: ABL (for quality control and quantification)
• Sample Type: Total RNA extracted from bone marrow or peripheral blood
• Input Requirement: Typically 50–200 ng RNA per reaction
• Detection Capability: Detects and differentiates 5′ and 3′ forms of bcr2
• Compatible Instruments: ABI 7500, Bio-Rad CFX96™, Roche LightCycler®, and similar platforms