t(15;17) PML/RARA Quantification for Acute Promyelocytic Leukemia

Background

Acute promyelocytic leukemia (APL), a subset of acute myeloid leukemia (FAB-M3), is cytogenetically characterized by the non-random, balanced t(15;17)(q22;q11,2-21) chromosome translocation. The chromosome 17 breakpoint occurs consistently in the second intron region of the structural retinoic acid receptor alpha (RARα) gene. RARα is a member of a nuclear receptor superfamily, and its disruption is thought to be directly linked to the interruption of normal myeloid differentiation. A transcription factor gene (PML1) is situated at the chromosome 15 breakpoint region. The chromosome 15 breakpoint can occur in intron 3 of the PML1 gene or in a downstream breakpoint region consisting of variable breakpoints in exon/intron 6. The t15;17 translocation generates a PML/RARα chimeric gene which is transcribed as a fusion PML/RARα mRNA. Detection of t(15;17) or its consequence, the fusion PML/RARα mRNA, is critical for patients with suspected APL. Its presence is the best predictor of a favorable response to retinoids, such as all-trans retinoic acid (ATRA), in combination with chemotherapy.

Clinical Utility

Quantification of expression of the t(15;17) PML/RARα chromosomal translocation is done on for confirmation of clinical diagnosis and monitoring of treatment efficacy.

Methodology

The presence of the PML/RARα mRNA in a patient’s bone marrow or peripheral blood is detected using a real-time quantitative PCR to detect transcript levels of PML/RARα at breakpoints in intron 3 or inron/exon 6 of PML and exon 3 of RARα. We quantify transcript levels with relative quantification using a homogeneous cell line (UF1 or NB4) as the calibrator

Performed

Twice a week

Turnaround time

Within 4-10 business days of receipt

CPT

81316

Specimen Requirements

  1. Peripheral Blood: 3-5 ml, collected in EDTA (purple top) tube, store at room temperature 24 hours
  2. Bone Marrow: 0.5-1 ml, collected in EDTA (purple top)tube, store at room temperature, 24 hours
  3. Unacceptable Specimens: Frozen blood or bone marrow specimens are unacceptable as are tissue samples that have undergone a freeze/thaw cycle(s).

Shipment Must Include

Specimen
Requisition form
Patient pathology report

References

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  2. Gabert, J., E. Beillard, V.H.J. van der Velden, W. Bi, D. Grimwade, N. Pallisgaard, G. Barnaby, G. Cazzaniga, J.M. Cayuela, H. Cave, F. Pane, J.L.E. Aerts D. De Micheli, X. Thirion, V. Pradel, M. Gonzalez, S. Viehmann, M. Malec, G. Saglio and J.J.M. van Dongen. 2003. Standardization and quality control studies of "real-time" quantitative reverse transcriptase polymerase chain reaction of fusion gene transcripts for residual disease detection in leukemia – A Europe Against Cancer Program. Leukemia 17: 2318-2357.
  3. Livak, K.J. and T.D. Schmittgen. 2001. Analysis of relative gene expression data using real-time quantitative PCR and the 2−ΔΔCT method. Methods 25: 402-408.
  4. Lowenberg, B. 2004. Minimal residual disease in chronic myeloid leukemia. N. Engl. J. Med. 349: 1399-1401.