Four-chromosomes complex translocations in acute promyelocytic leukemia: description of two cases

Cryptic t(15;17) acute promyelocytic leukemia with a karyotype of add(11)(p15) and t(13,20)- A case report with a literature review

Most acute promyelocytic leukemias (APL) are characterized by reciprocal translocations t(15;17)(q22;21), which results in the fusion of the promyelocytic leukemia protein (PML) gene at 15q22 with retinoic acid receptor a (RARα) gene at 17q21. However, several complex variant translocations also have been reported. Here, we report a 62-year-old man with typical morphology and clinical features of APL with a complex karyotype including add(11)(p15) and t(13;20)(q12;q11.2) without typical t(15;17) assayed by the G-banding analysis. The fluorescence in situ hybridization with a PML/RARα dual-color DNA probe showed an atypical fusion signal, quantitative real-time polymerase chain reaction analysis showed PML/RARα fusion transcripts, and NGS detected FLT3, WT1, and KRAS mutations. The patient achieved complete remission after treatment with conventional chemotherapy combined with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). Although the mechanism of this kind of cryptic variant remains unknown, we conclude that the cryptic PML/RARα fusion with add(11)(p15) and t(13;20)(q12;q11.2) seems not to alter the effectiveness of chemotherapy combined with ATRA and ATO.

A complex translocation (3;17;15) in acute promyelocytic leukemia confirmed by fluorescence in situ hybridization

Acute promyelocytic leukemia (APL) is typified by t(15;17)(q22;q21), generating the promyelocytic leukemia (PML) gene at 15q22 with the retinoic acid α-receptor (RARA) gene at 17q21. The PML-RARA fusion gene is believed to play a vital role in leukemogenesis. A sizeable minority of patients with complex variants of APL have been reported. The present study reports the case of a 33-year-old male with APL carrying a potential complex translocation. The initial symptom was bleeding gums. Chromosomal analysis of the bone marrow cells revealed an atypical 17q aberration. Fluorescence in situ hybridization further indicated that 92% of analyzed cells were positive for the PML-RARA fusion gene. The patient experienced complete remission following treatment with arsenic trioxide and chemotherapy. The atypical translocations in acute promyelocytic leukemia require further investigation.

Coexistence of t(15;17) and t(15;16;17) detected by fluorescence in situ hybridization in a patient with acute promyelocytic leukemia: A case report and literature review

Acute promyelocytic leukemia (APL) is characterized by the t(15;17)(q22;q21), which results in the fusion of the promyelocytic leukemia (PML) gene at 15q22 with the retinoic acid α-receptor (RARA) gene at 17q21. The current study presents the case of a 54-year-old female with APL carrying the atypical PML/RARA fusion signal due to a novel complex variant translocation t(15;16;17)(q22;q24;q21), as well as the classical PML/RARA fusion signal. Subsequent array comparative genomic hybridization revealed somatic, cryptic deletions on 3p25.3, 8q23.1 and 12p13.2-p13.1, and a duplication on 8q11.2; however, no genetic material loss or gain was observed in the breakpoint regions of chromosomes 15, 16 or 17. To the best of our knowledge, this is the first report of the coexistence of two abnormal clones, one classical and one variant, presenting simultaneously in addition to cryptic chromosome segmental imbalances in an adult APL patient.

A t(17;20)(q21;q12) masking a variant t(15;17)(q22;q21) in a patient with acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is genetically characterized by a reciprocal translocation between chromosomes 15 and 17, the t(15;17)(q22;q21), which results in the fusion gene PML/RARA. A small proportion of patients with APL have complex or simple variants of this translocation. We report the case of a 31-year-old woman with APL (FAB-M3 classical form) carrying an apparently balanced translocation t(17;20)(q21;q12) masking a t(15;17)(q22;q21) confirmed by fluorescence in situ hybridization (FISH) and molecular studies. The patient was treated with an all-trans-retinoic acid (ATRA) plus anthracycline-based protocol and achieved complete remission, with no recurrence to date. These results illustrate the usefulness of combining cytogenetics, FISH, and reverse transcription-polymerase chain reaction (RT-PCR) methods to evidence the PML/RARA fusion gene in cases with morphologic suspicion of APL with variant or cryptic t(15;17).

A complex, four-way variant t(15;17) in acute promyelocytic leukemia

Complex variant 15;17 translocations are increasingly recognized in acute promyelocytic leukemia (APL). We report the case of a 47-year-old woman with APL harboring a novel four-way translocation. She presented with persistent bleeding after a tooth extraction. Blood cell counts at admission were hemoglobin at 9.0 g/dL, platelets at 15 x 10(9)/L, and white blood cells at 0.460 x 10(9)/L with abnormal promyelocytes. Most nucleated cells of bone marrow aspirates were abnormal promyelocytes with Auer rods. Chromosome analysis of unstimulated bone marrow cell cultures revealed a variant t(15;17) in the form of t(10;17;15;22)(q22;q21;q22;q11.2). Fluorescence in situ hybridization with a PML/RARA dual-color DNA probe showed the fusion signals on der(15) and the residual PML signals on der(22). RT-PCR showed long-form PML/RARA fusion transcripts. A complete remission was attained with a course of conventional chemotherapy including ATRA. A literature review revealed that our case is one of the very rare four-way translocations and the first report of the involvement of chromosomes 10 and 22 in a variant t(15;17).

Cryptic translocation of PML/RARA on 17q. A rare event in acute promyelocytic leukemia

Cryptic translocations in acute promyelocytic leukemia are rare. Usually the gene fusion PML/RARA is located on chromosome 15. Combined cytogenetic, fluorescence in situ hybridization (FISH), and molecular (polymerase chain reaction [PCR]) analysis were employed for the diagnosis and precise localization of the fusion gene. Conventional cytogenetics showed a normal karyotype; PCR showed a typical PML/RARA rearrangement in exon 1. FISH analysis revealed that a submicroscopic part of chromosome 15 had been inserted into 17q. This case adds further information on alternative ways of rearrangement of the PML/RARA genes, possibly correlated with all-trans retinoic acid resistance.

A new complex variant t(4;15;17) in acute promyelocytic leukemia: fluorescence in situ hybridization confirmation and literature review

We report a 37-year-old male with acute promyelocytic leukemia (APL) harboring a complex translocation (4;15;17). Karyotypic analysis with R-banding of bone marrow cells revealed 46,XY,t(4;15;17)(q21;q22;q21). Fluorescence in situ hybridization analysis using painting probes for chromosomes 4, 15 and 17 and reverse transcriptase polymerase chain reaction analysis revealed three derivative chromosomes: der(4)t(4;15)(q21;q22), der(15)t(4;15;17)(q21;q22;q21), and del(17)(q21q22). This is the third report of such a translocation and the first confirmed by molecular methods. Considering reported similar cases, it is possible that 4q21 is a nonrandom breakpoint in APL with complex translocations and the gene involved in 4q21 should be investigated.

Molecular cytogenetic characterization and clinical relevance of additional, complex and/or variant chromosome abnormalities in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by typical morphological manifestation, t(15;17) translocation and active response to all-trans retinoic acid (ATRA) in the great majority of patients. However, a subset of APL cases may present atypical phenotypic, cytogenetic or molecular features at different stages of the disease. The biological and clinical significance of these features sometimes remains obscure. In this study, 284 APL patients were cytogenetically analyzed and precise diagnosis was performed according to the molecular cytogenetic results. Twenty-six APL patients were identified as having additional, complex and/or variant chromosomal abnormalities at diagnosis or at relapse, 16 of them being further analyzed using fluorescence in situ hybridization (FISH) or chromosome painting (CP). Interestingly, some of these chromosomal aberrations were found to be associated with atypical morphology and/or drug response, indicating a genotype-phenotype correlation. Analysis of the complex karyotype may also allow a better understanding of the levels of cellular origin of the leukemogenesis. Examination of the remission induction and survival data showed that the presence of the additional/complex chromosome abnormalities was related to the prognosis in both primarily diagnosed and relapsed patients in this series.

A new variant translocation of t(15;17) in a patient with acute promyelocytic leukemia (M3): t(15;19;17)(q22;p13;q12)

The reciprocal translocation (15;17) is specifically associated with acute promyelocytic leukemia [APL; M3 subtype according to French-American-British (FAB) classification]. A few patients with this disease have complex variant translocations. We describe a patient with M3 carrying t(15;19;17)(q22;p13;q12), which is a new type of variant translocation. The karyotypic interpretation was confirmed by Southern blot analysis with the use of RAR alpha and by fluorescence in situ hybridization (FISH) with the use of painting probes of chromosomes 15, 17, and 19 and a (15;17) translocation DNA probe. The results support the idea that the key event in APL is the formation of fusion gene PML/RAR alpha on the der(15).

A new complex translocation (15;20;17)(q22;p13;q21) in acute promyelocytic leukemia

We describe here a 39-year-old male with acute promyelocytic leukemia (APL) carrying a new complex translocation (15;20;17). A chromosomal analysis of the bone marrow cells showed 46, XY, t(15;20;17)(q22;p13;q21). Fluorescence in situ hybridization (FISH) analysis using plasmid DNA libraries of chromosomes 15, 17, and 20 revealed three derivative chromosomes, der(15)t(15;17), der(17)t(17;20), and der(20)t(15;20). Fluorescence in situ hybridization with cosmid DNA probes flanking the breakpoints of t(15;17) did not show the retinoic acid receptor alpha (RAR alpha)/PML fusion signal usually generated on the der(17)t(15;17). However, rearrangement of the RAR alpha gene and expression of the PML/RAR alpha chimeric transcript were identified by Southern blot and reverse-transcriptase polymerase chain reaction (RT-PCR) analyses, respectively. Our results confirmed that the PML/RAR alpha gene on the der(15)t(15;17), not the RAR alpha/PML gene, must be essential to leukemogenesis in APL. Furthermore, considering another reported case with a 20p13 aberration, it is possible that 20p13 is a nonrandom breakpoint in APL with a complex translocation.

Acute promyelocytic leukemia with t(15;16;17;19) and unusual fluorescence in situ hybridization pattern with PML and RARA probes

We report a 58-year-old female with typical morphological and clinical features of acute promyelocytic leukemia in whom a complex translocation involving chromosomes 15, 16, 17 and 19 was detected using conventional cytogenetics and fluorescence in situ hybridization (FISH) with chromosome specific paints. RARA-PML fusion was not evident by FISH, but the RARA signal was split in 74.5% of cells. GTL-banding and FISH with probes for PML, RARA and chromosome 15 specific paint raise the possibility of PML-RARA fusion on the abnormal chromosome 19 in the complex translocation. The unusual PML-RARA fusion may be related to this patient's poor response to induction therapy with all-trans-retinoic acid.

Molecular analysis of PML-RAR alpha fusion mRNA detected by reverse transcription-polymerase chain reaction assay in long-term disease-free acute promyelocytic leukaemia patients

By use of RT-PCR of PML/RAR alpha, we evaluated bone marrow aspirates in 10 patients with APL in long-term disease-free status after induction chemotherapy and consolidation (median 54 months: range 33-101 months from complete remission). All patients were in clinical and cytogenetic remission at the time of molecular evaluation (range 32-96 months from CR). All patients but one were found to be RT-PCR negative at the molecular level for the expression of PML-RAR alpha transcript, confirming that the majority of the patients with long-term survival of APL are characterized by the eradication of the neoplastic clone.