A variant of acute promyelocytic leukemia with t(4;17)(q12;q21) showed two different clinical symptoms

Acute promyelocytic leukemia with FIP1L1::RARA fusion gene: The clinical utility of transcriptome sequencing and bioinformatic analyses

Background

Acute promyelocytic leukemia (APL) is typically characterized by the presence of coagulopathy and the PML::RARA fusion gene. The FIP1L1::RARA has been reported as a novel fusion gene, but studies on its pathogenesis are limited.

Objectives

A FIP1L1::RARA fusion in a child finally diagnosed as APL was reported. RNA sequencing (RNA-seq) of six patients (three cases of acute lymphoblastic leukemia (ALL), one case of myelodysplastic syndrome (MDS), one case of acute megakaryoblastic leukemia (M7), and one case of APL with FIP1L1::RARA) were performed.

Methods

Transcriptome analysis of six patients was performed by RNA-seq. The heat map was used for showing the RNA expression profile, the volcano plot for identifying differential expression genes (DEGs), and the KEGG Orthology-Based Annotation System (KOBAS) online biological information database for KEGG pathway enrichment analysis.

Results

Obvious differences between APL with FIP1L1::RARA and hematologic malignancies were identified. 1060 common differentially expressed genes (co-DEGs) were detected between APL with FIP1L1::RARA vs ALL and APL with FIP1L1::RARA vs myeloid neoplasms (MDS, M7), the up-regulated genes were mainly mapped into platelet activation, cancer, AMPK signaling pathway, PI3K-Akt signaling pathway, and MAPK signaling pathway. The down-regulated genes were significantly associated with TNF signaling pathway, Rap1 signaling pathway, Age-RAGE signaling pathway, and apoptosis.

Conclusion

A FIP1L1::RARA fusion in a child finally diagnosed as APL was reported. RNA-seq may provide a new diagnostic method when RARA rearrangements fail to be identified by conventional methods. In the analysis of co-DEGs between case vs ALL and case vs myeloid neoplasms, the up-regulated and down-regulated genes were enriched in different signaling pathways. Further experimental studies are needed to identify pathogenesis and treatment for APL with FIP1L1::RARA.

Atypical Rearrangements in APL-Like Acute Myeloid Leukemias: Molecular Characterization and Prognosis

Acute promyelocytic leukemia (APL) accounts for 10–15% of newly diagnosed acute myeloid leukemias (AML) and is typically caused by the fusion of promyelocytic leukemia with retinoic acid receptor α (RARA) gene. The prognosis is excellent, thanks to the all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) combination therapy. A small percentage of APLs (around 2%) is caused by atypical transcripts, most of which involve RARA or other members of retinoic acid receptors (RARB or RARG). The diagnosis of these forms is difficult, and clinical management is still a challenge for the physician due to variable response rates to ATRA and ATO. Herein we review variant APL cases reported in literature, including genetic landscape, incidence of coagulopathy and differentiation syndrome, frequent causes of morbidity and mortality in these patients, sensitivity to ATRA, ATO, and chemotherapy, and outcome. We also focus on non-RAR rearrangements, complex rearrangements (involving more than two chromosomes), and NPM1-mutated AML, an entity that can, in some cases, morphologically mimic APL.

Genotypic and Phenotypic Characteristics of Acute Promyelocytic Leukemia Translocation Variants

Acute promyelocytic leukemia (APL) is a special disease entity of acute myeloid leukemia (AML). The clinical use of all-trans retinoic acid (ATRA) has transformed APL into the most curable form of AML. The majority of APL cases are characterized by the fusion gene PML-RARA. Although the PML-RARA fusion gene can be detected in almost all APL cases, translocation variants of APL have been reported. To date, this is the most comprehensive review of these translocations, discussing 15 different variants. Reviewed genes involved in APL variants include: ZBTB16, NPM, NuMA, STAT5b, PRKAR1A, FIP1L1, BCOR, NABP1, TBLR1, GTF2I, IRF2BP2, FNDC3B, ADAMDTS17, STAT3, and TFG. The genotypic and phenotypic features of APL translocations are summarized. All reported studies were either case reports or case series indicating the rarity of these entities and limiting the ability to drive conclusions regarding their characteristics. However, reported variants have shown variable clinical and morphological features, with diverse responsiveness to ATRA.