t(15;17) — oncology-focused definition
t(15;17) is a reciprocal chromosomal translocation between chromosome 15 and chromosome 17, which creates the PML–RARA fusion gene.
- Chromosomes involved:
- 15q24 → PML (promyelocytic leukemia) gene
- 17q21 → RARA (retinoic acid receptor alpha) gene
Oncology relevance:
- Pathognomonic for acute promyelocytic leukemia (APL).
- The PML–RARA fusion protein blocks differentiation of promyelocytes, leading to accumulation of immature leukemic cells.
- Unique among leukemias because it is treatable with differentiation therapy.
Clinical significance (for oncology pharmacists):
- Diagnostic marker: Detected by FISH, RT-PCR, or karyotyping.
- Therapeutic relevance:
- All-trans retinoic acid (ATRA) + arsenic trioxide induces differentiation and apoptosis.
- Rapid treatment is critical due to high risk of coagulopathy/DIC.
- Prognosis: Excellent if diagnosed and treated promptly.
Key takeaway:
t(15;17) drives the PML–RARA fusion, which blocks differentiation in APL but also makes it highly targetable with ATRA/arsenic therapy, demonstrating a unique example of molecularly guided treatment.
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