Overexpression of NPM–ALK induces different types of malignant lymphomas in IL-9 transgenic mice

Abstract

Anaplastic large-cell lymphoma (ALCL) comprises approximately 25% of all non-Hodgkin lymphomas (NHL) in children and young adults, and up to 15% of high-grade NHL in older patients. Over 50% of these tumours carry the translocation t(2;5)(p23;q35). The result of this translocation is the fusion of the nucleophosmin (NPM) gene to the anaplastic lymphoma kinase (ALK) gene. The resulting hybrid protein contains the ALK catalytic domain that consequently confers transforming potential, which contributes to the pathogenesis of ALCL. To further analyse the transforming activity in an animal model, a cDNA encoding the protein product, NPM-ALK, was inserted into the retrovirus vector pLXSN and transduced into mouse bone marrow progenitors. These cells were subsequently used in a bone marrow transplant with the aim of reconstituting the haematopoietic compartments of lethally irradiated recipients. IL-9 transgenic mice were chosen as the animal model system, because dysregulated expression of the IL-9 gene in transgenic mice results in the sporadic development of spontaneous thymic lymphomas. Moreover, IL-9 is known to be expressed in cases of human ALCL. We used 15 IL-9 transgenic mice and eight corresponding wild-type mice (FVB/N) and transplanted them with NPM/ALK infected bone marrow cells. Eight IL-9 transgenic mice, serving as a control group, received pLXSN (vector only)-infected marrow. Reconstituted mice developed NPM-ALK-positive lymphomas, including lymphoblastic lymphomas of Tcell type (T-LB), mature and immature plasmacytoma (PC), and plasmoblastic/anaplastic diffuse large-B-cell lymphoma after about 19-20 weeks. The combined overexpression of NPM-ALK and IL-9 led to the transformation of murine lymphoid cells with accelerated and enhanced development of T-LB in 46% of the mice, which only very rarely occurs in IL-9 transgenic mice only. Of the 15 animals, five (33%) developed plasmacytic/plasmoblastic neoplasms, of which the most aggressive tumours share many features with anaplastic/plasmoblastic diffuse large-B-cell lymphoma on the basis of morphology, a characteristic growth pattern and ALK expression.

What have we learnt from mouse models of NPM-ALK-induced lymphomagenesis?

“…Expression of NPM-ALK in IL-9 transgenic mouse bone marrow by retroviral transduction followed by implantation of the transduced bone marrow into IL-9 transgenic mice resulted in tumours of variable phenotypes. 21 In some cases, T lymphoblastic lymphomas (46%) were observed and in others plasmacytomas (46%) or plasmablastic lymphomas (33%), similar to the heterogeneous range of human tumours expressing ALK. It is therefore possible that differentiation of T cells to the TH2 phenotype, or secondary mutations that elevate IL-9 by other mechanisms, might contribute to NPM-ALK-induced oncogenesis.…”

“…The fact that the t(2;5) translocation has been detected in the lymphocytes of healthy individuals suggests that secondary events are critical for disease progression, [30][31][32] consistent with the relatively long disease latency (13-38 weeks) in the CD4-and Vav-promoter transgenic NPM-ALK mouse lines. For example, regulation of IL-9 expression has been implicated in NPM-ALK-mediated disease progression based on an interesting mouse system developed by Lange et al 21 IL-9 expression has been noted in some cases of ALCL and its expression in transgenic mice results in the development of T cell tumours with a phenotype similar to ALCL but with a long latency. 33 IL-9 is a multifunctional cytokine produced by activated T cells of T-Helper Type-2 (TH2) phenotype and is also involved in mast cell proliferation and differentiation.…”

The R1275Q Neuroblastoma Mutant and Certain ATP-competitive Inhibitors Stabilize Alternative Activation Loop Conformations of Anaplastic Lymphoma Kinase

“…However, ALK was initially discovered as part of a fusion protein identified in a subset of anaplastic large cell lymphoma patients wherein the entire ALK cytoplasmic domain was fused to nucleophosmin (NPM) via a cytogenetic translocation (1). The NPM-ALK fusion protein possesses constitutive kinase activity resulting from NPM-derived oligomerization and subsequent ALK autoactivation, and it has strong transforming potential both in vitro and in vivo (2)(3)(4)(5)(6). More recently, additional ALK fusion proteins have been discovered in inflammatory myofibroblastic tumors (6 -8), diffuse large B-cell lymphomas (9,10), certain squamous cell carcinomas (11,12), and non-small cell lung cancer (NSCLC) (13,14).…”

Identification of differential and functionally active miRNAs in both anaplastic lymphoma kinase (ALK)+and ALK−anaplastic large-cell lymphoma

“…The consequence of the fusion is constitutive ALK expression, which leads to the activation of many different growth-promoting and antiapoptotic pathways, including PI3K/Akt1/mTOR (5)(6)(7)(8), Jak/Stat (9-11), cJun, JunB (12)(13)(14), and c-myc (12,15). The transforming capacity of the NPM-ALK fusion was shown for the first time in murine chimeras in which lethally irradiated recipients were rescued with NPM-ALK-transduced bone marrow (4,16,17) as well as in several transgenic mouse models that expressed the NPM-ALK fusion protein in hematopoietic cells (14,18,19). Specifically, NPM-ALK transgenic mice in which gene expression is directed by the T-cellspecific CD4 promoter develop aggressive T-cell lymphomas with a median survival of 18 wk (18).…”