[1399] Structural Abnormalities of JAK2 in Peripheral T-Cell Lymphomas

Andrew L Feldman, George Vasmatzis, Sarah H Johnson, Rhett P Ketterling, Ryan A Knudson, Stephen M Ansell, Ahmet Dogan, Marshall E Kadin. Mayo Clinic, Rochester, MN; Roger Williams Medical Center, Providence, RI

Background: Constitutive JAK/STAT pathway activation promotes growth in peripheral T-cell lymphomas (PTCLs) and other hematologic neoplasms. Unlike myeloid neoplasms, however, PTCLs lack JAK2 mutations. Structural JAK2 abnormalities might contribute to JAK/STAT signaling in PTCL. A previous study of 32 PTCLs identified 2 JAK2 translocations and 4 JAK2 copy number abnormalities (CNAs). In addition, Mac-1 and Mac-2A cell lines derived from cutaneous anaplastic large cell lymphoma (ALCL) have a t(8;9)(p22;p24) similar to translocations causing PCM1/JAK2 fusion in other hematologic neoplasms. We characterized the nature of the t(8;9) in Mac-1 and Mac-2A and investigated the frequency of JAK2 translocations and CNAs in 217 PTCLs.
Design: Mate-pair Next Generation sequencing (Illumina HiSeq) was performed on genomic DNA from Mac-1 and Mac-2A and sequence data were mapped to the hg19 reference genome using our published binary indexing algorithm. Mate pairs mapping to both 8p22 and 9p24 were identified, PCR primers were designed in these areas, and amplicons were Sanger sequenced. JAK2 exons 12 and 14 were Sanger sequenced. Breakapart fluorescence in situ hybridization (FISH) for JAK2 was performed on cell lines and paraffin sections of PTCLs.
Results: Sequencing confirmed a balanced t(8;9)(p22;p24) involving PCM1 and JAK2 and localized the 9p24 breakpoint to intron 16 of JAK2 with an associated 38 base-pair microdeletion. No exon 12 or 14 mutations were identified in Mac-1, Mac-2A, Karpas 299, FE-PD, SUDHL-1, MyLa, SeAx, HUT78, Jurkat, or CCRF-CEM. Metaphase FISH confirmed the t(8;9)(p22;p24) in Mac-1 and Mac-2A. Interphase FISH did not identify JAK2 translocations in 217 PTCLs from 200 patients with: angioimmunoblastic TCL, 60; ALCL, 53 (15 ALK-positive, 23 ALK-negative, and 15 cutaneous); PTCL, NOS, 59; extranodal NK/TCL, 11; mycosis fungoides, 5; and other cytotoxic PTCLs, 12. Three tumors from 2 patients (ALK-negative ALCL and PTCL, NOS) had amplifications of JAK2 (>10 copies/cell).
Conclusions: We confirmed a balanced PCM1/JAK2 translocation in Mac-1 and Mac-2A, corroborating similar sequencing studies performed elsewhere. FISH analysis in 217 primary PTCL samples did not identify additional cases with JAK2 translocations. JAK2 amplifications were rare (1%). Since JAK2 mutations have not been identified in PTCL, constitutive JAK/STAT activation in PTCL is unlikely to derive from genetic abnormalities of JAK2. Further studies to identify the origin of JAK/STAT signaling in PTCL may help optimize the development and use of specific inhibitors of this pathway in PTCL patients.
Category: Hematopathology

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 198, Wednesday Morning

 

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