Identification of atypical PML-RARA breakpoint in a patient with acute promyelocytic leukemia.
Acute promyelocytic leukemia (APL) of the M3 subtype is characterized by translocation t(15;17) that generates the PML-RARA fusion gene. Depending on the breakpoint position in the PML gene, 3 main fusion transcripts usually result. These breakpoints are bcr1 and bcr3 in introns 6 and 3, respectively, and bcr2 in exon 6. This report describes a rare atypical bcr2 breakpoint in a patient with morphological, cytogenetic and molecular features of APL. The presence of t(15;17) was first revealed by fluorescent in situ hybridization. Molecular analysis by reverse transcription polymerase chain reaction using primers for different PML-RARA junctions showed bands with different sizes compared with those generated from the three classical breakpoints, namely bcr1, bcr2 and bcr3. However, sequence analysis confirmed the presence of a bcr2 transcript with an atypical breakpoint within exon 6. The patient responded well to treatment and is now in complete remission. However, suggesting a favorable prognosis associated with such a rare transcript is difficult as more similar cases are needed to confirm such a conclusion. This article also stresses the importance of sequencing unusual polymerase chain reaction products to confirm their nature.
Ismail
Said
S
Faculty of Medicine, University of Jordan, Amman, Jordan. sismail@ju.edu.jo
Ababneh
Nidaa
N
Awidi
Abdalla
A
D000328:Adult; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics*; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D005260:Female; D006801:Humans; D007438:Introns / Q000235:genetics; D015473:Leukemia, Promyelocytic, Acute / Q000175:diagnosis / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D011379:Prognosis; D017434:Protein Structure, Tertiary / Q000235:genetics; D014178:Translocation, Genetic / Q000235:genetics*
D015514:Oncogene Proteins, Fusion; C093476:promyelocytic leukemia-retinoic acid receptor alpha fusion oncoprotein