What is BCR-ABL?

BCR-ABL1 is a fusion gene resulting from a reciprocal translocation between chromosomes 9 and 22, t(9;22)(q34;q11), commonly referred to as the Philadelphia chromosome. This abnormality leads to the formation of a chimeric gene that encodes a constitutively active tyrosine kinase. The aberrant kinase activity disrupts normal hematopoiesis and plays a central role in the pathogenesis of several hematological malignancies.

There are three clinically relevant BCR-ABL fusion transcript variants:

• p210 (major BCR-ABL, M-BCR), most prevalent in chronic myeloid leukemia (CML)

• p190 (minor BCR-ABL, m-BCR), frequently observed in Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL)

• p230 (micro BCR-ABL, μ-BCR), occasionally seen in atypical CML or some AML subtypes

Accurate detection and quantification of these variants is essential for both diagnosis and molecular follow-up.

Role of BCR-ABL in Leukemia

The BCR-ABL1 fusion gene produces a protein with unregulated tyrosine kinase activity, promoting cellular proliferation and inhibiting apoptosis. This mechanism underlies several types of leukemia:

• Chronic myeloid leukemia (CML): Present in approximately 95% of cases, characterized by excessive proliferation of myeloid cells

• Ph-positive acute lymphoblastic leukemia (Ph+ ALL): More frequent in adult ALL; typically associated with the p190 variant

• Acute myeloid leukemia (AML): Rarely, BCR-ABL1 fusion transcripts—particularly p230—may be detected

Quantitative assessment of BCR-ABL1 levels is critical in monitoring response to therapy, especially in patients receiving tyrosine kinase inhibitors (TKIs). International guidelines recommend the use of RT-qPCR aligned with the International Scale for reliable minimal residual disease (MRD) tracking.

About the TRUPCR® BCR-ABL Quantitative PCR Testing Kit

The TRUPCR® BCR-ABL Quantitative PCR Testing Kit is a CE-IVD marked molecular diagnostic assay developed for the quantitative detection, differentiation, and monitoring of BCR-ABL1 fusion transcripts in bone marrow or peripheral blood samples.

The assay distinguishes between major (p210), minor (p190), and micro (p230) BCR-ABL transcripts using three independent RT-qPCR reactions. The inclusion of an ABL1 internal control ensures accurate normalization and transcript quantification. Results are traceable to the First WHO International Genetic Reference Panel (NIBSC code: 09/138) and the ERM-AD623a–f reference material, enabling harmonization across laboratories.

The kit is validated for use in:

• Diagnostic confirmation of CML, Ph+ ALL, and select AML cases

• Molecular monitoring of TKI therapy response

• Determination of deep molecular response in line with EUTOS guidelines

All required reagents for reverse transcription and real-time PCR are included, minimizing pre-analytical variability.

Principle and Workflow

The TRUPCR® BCR-ABL Quantitative Kit follows a two-step RT-qPCR workflow:

1. RNA Isolation and Reverse Transcription
   Total RNA is extracted from peripheral blood or bone marrow, followed by reverse transcription to generate complementary DNA (cDNA) using the supplied RT enzyme.

2. Quantitative PCR Amplification
   Three parallel reactions are carried out to detect and quantify:

   • p210 (major BCR-ABL)

   • p190 (minor BCR-ABL)

   • p230 (micro BCR-ABL)

   The assay includes specific primers and probes for each transcript, along with an ABL1 reference gene for normalization.

The inclusion of PCR mastermix, cDNA synthesis reagents, and controls ensures lot-to-lot consistency and reduces hands-on preparation time. Results can be interpreted using software capable of standard curve analysis and International Scale conversion.

Clinical Application

The TRUPCR® BCR-ABL Quantitative Kit is intended for routine molecular diagnostics in hospital laboratories. It is suited for:

• Initial diagnosis of Philadelphia chromosome-positive leukemias

• Transcript differentiation to support appropriate clinical classification

• Baseline measurement and longitudinal monitoring during TKI treatment

• Assessment of minimal residual disease, with sensitivity for detection of molecular responses up to 4.7-log reduction

Standardization to international reference panels supports inter-laboratory comparability, facilitating participation in multicenter clinical studies and alignment with global treatment guidelines.