Definition

PML-RARA is the fusion oncoprotein resulting from the t(15;17)(q24;q21) chromosomal translocation, the hallmark genetic alteration in acute promyelocytic leukemia (APL). This aberrant protein drives leukemogenesis and is the primary therapeutic target in APL.

Key Points

1. Molecular Pathogenesis:
   • PML (Promyelocytic Leukemia gene) on chromosome 15 fuses with RARA (Retinoic Acid Receptor Alpha) on chromosome 17.
   • The fusion protein disrupts:
     • Normal myeloid differentiation (blocks RARA-mediated transcription).
     • PML nuclear body function (impairs tumor suppression).
2. Role in APL Therapy:
   • ATRA (All-Trans Retinoic Acid): Binds RARA moiety, releasing transcriptional repression and allowing differentiation.
   • Arsenic Trioxide (ATO): Degrades PML-RARA via SUMOylation/proteasomal pathways.
3. Diagnostic Utility:
   • PCR for PML-RARA transcript monitors minimal residual disease (MRD).
   • Fluorescence in situ hybridization (FISH) confirms t(15;17) at diagnosis.
4. Clinical Implications:
   • High-risk APL: Variant transcripts (e.g., STAT5B-RARA) may confer resistance to ATRA/ATO.
   • Relapse: Re-emergence of PML-RARA by PCR prompts preemptive therapy.