Recurrent Novel P2RY8/IGH Translocations in B-Lymphoblastic Leukemia/Lymphoma

Abstract

Translocations involving the immunoglobulin heavy chain (IGH) locus are common abnormalities in B-lymphoblastic leukemia/lymphoma (B-ALL) and multiple myeloma. These rearrangements result in a juxtaposition of IGH enhancers to the vicinity of oncogenes, such as MYC and CRLF2, leading to the upregulation of oncogenes. Here, we identified recurrent novel P2RY8/IGH translocations in three B-ALL patients by transcriptome sequencing. Noncoding exon 1 of P2RY8 was translocated to different sites of the IGH gene, resulting in transcripts of P2RY8/IGHM, P2RY8/IGHV, and P2RY8/IGHD. However, a high expression level of truncated P2RY8 was observed in the patients compared with healthy donors, which might be related to the aggressive clinical course and inferior outcome. In summary, we described recurrent novel P2RY8/IGH translocations with high expression levels of P2RY8, which may contribute to the guidelines for clinical diagnosis and treatment.

Keywords: B-lymphoblastic leukemia/lymphoma; IGH; P2RY8; fusion gene; translocation.

Figure 1

Identification of novel recurrent P2RY8/IGH fusions. (A) Bone marrow aspirate at diagnosis or relapse (Wright’s staining ×1,000). (B) Fluorescence in situ hybridization results with a CRLF2 break-apart probe, which detected split signals of CRLF2. (C) Immunophenotyping of bone marrow cells at diagnosis or relapse. Flow cytometric analyses of leukemic cells revealed that the blast cells in Case 2 were positive for CRLF2. (D) RNA sequencing analysis revealed one breakpoint in exon 1 of the P2RY8 gene and breakpoints in different exons of the IGH gene in three patients. (E) A 139 bp product for Case 1 and a 508 bp product for Case 2 were detected by RT–PCR in samples taken at diagnosis. A product of 504 bp for Case 3 was detected by RT–PCR in samples taken at relapse. (F) Sequence alignment of the amplified product revealed breakpoints between exon 1 of the P2RY8 gene and different exons of the IGH gene at diagnosis or relapse. (G) Structure of the primers designed for the RT–qPCR of P2RY8. The amount of P2RY8 mRNA in BMNC cell fractions purified from P2RY8-IGH patients, healthy volunteers (normal) and B-ALL patients was determined by real-time RT–PCR analysis. Each fold change was calculated by the 2^(-△Ct) method (left) and 2^(-△△Ct) method (right). Values are the mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.