PML/RARα and FLT3-ITD induce an APL-like disease in a mouse model

Abstract

Acute promyelocytic leukemia (APL) cells invariably express aberrant fusion proteins involving the retinoic acid receptor ␣ (RAR␣). The most common fusion partner is promyelocytic leukemia protein (PML), which is fused to RAR␣ in the balanced reciprocal chromosomal translocation, t(15;17)(q22:q11). Expression of PML͞ RAR␣ from the cathepsin G promoter in transgenic mice causes a nonfatal myeloproliferative syndrome in all mice; about 15% go on to develop APL after a long latent period, suggesting that additional mutations are required for the development of APL. A candidate target gene for a second mutation is FLT3, because it is mutated in approximately 40% of human APL cases. Activating mutations in FLT3, including internal tandem duplication (ITD) in the juxtamembrane domain, transform hematopoietic cell lines to factor independent growth. FLT3-ITDs also induce a myeloproliferative disease in a murine bone marrow transplant model, but are not sufficient to cause AML. Here, we test the hypothesis that PML͞RAR␣ can cooperate with FLT3-ITD to induce an APL-like disease in the mouse. Retroviral transduction of FLT3-ITD into bone marrow cells obtained from PML͞RAR␣ transgenic mice results in a short latency APL-like disease with complete penetrance. This disease resembles the APL-like disease that occurs with long latency in the PML͞RAR␣ transgenics, suggesting that activating mutations in FLT3 can functionally substitute for the additional mutations that occur during mouse APL progression. The leukemia is transplantable to secondary recipients and is ATRA responsive. These observations document cooperation between PML͞RAR␣ and FLT3-ITD in development of the murine APL phenotype.A cute promyelocytic leukemia (APL) comprises 5-10% of cases of AML and is almost always associated with rearrangement of the retinoic acid receptor ␣ (RAR␣) gene as a consequence of balanced reciprocal chromosomal translocations. The t(15;17)(q22;q11.2) is the most common such translocation and most APL cells with this translocation express both the promyelocytic leukemia (PML)͞RAR␣ and RAR␣͞PML fusion proteins. Mouse models and cell culture assays have demonstrated that the PML͞RAR␣ fusion protein contributes to the leukemic phenotype in part by inhibiting differentiation and promoting survival of hematopoietic progenitor cells (1-6).Data from murine models and analysis of human APL genotypes indicate that the PML͞RAR␣ fusion protein is necessary, but not sufficient for the APL disease phenotype. Transgenic mice expressing PML͞RAR␣ under the control of the cathepsin G promoter can develop acute myeloid leukemia (AML) with many of the features of APL (1, 2, 7, 8). All transgenic animals expressing this transgene display a myeloproliferative syndrome characterized by elevated numbers of myeloid cells in the marrow and spleen. After a latency of 6-13 months, 15-20% of animals develop an APL-like disease. However, the penetrance increases to about 60% when both the PML͞RAR␣ and the reciprocal RAR␣͞PML cDNAs are expressed in early myeloid cel...

Potent co-operation between the NUP98-NSD1 fusion and the FLT3-ITD mutation in acute myeloid leukemia induction

“…Similar observations have been made upon co-expression of FLT3-ITD with the PML-RARα or MLL-AF9 fusions. 7,10 In addition, we found that the length of the latency period for AML induction by co-expression of NUP98-NSD1 and FLT3-ITD correlated with the ratio of FLT3-ITD to wild-type Flt3 mRNA expression ( Figure 5B). Phosphoflow experiments suggested that increased FLT3-ITD expression resulted in increased FLT3-derived cellular signals ( Figure 5C).…”

“…Several previous studies have clearly demonstrated that Balb/C mice are more prone to transformation of hematopoietic cells, but the underlying mechanism is poorly understood. 7 The observed strain-dependent differences of NUP8-NSD1 in hematopoietic cells suggest that Balb/C-derived cells might carry alterations that are functionally linked to NUP98-NSD1-induced transformation in vitro. 25,26 In 2 independent experiments, we observed that mice transplanted with NUP98-NSD1 immortalized cells developed myeloid hyperplasia in the bone marrow and spleen, associated with increased neutrophil counts in the majority of the mice.…”

“…[4][5][6] Clinical observations and experimental studies have shown that FLT3-ITD can co-operate strongly in leukemia induction with a variety of leukemia-initiating gene fusions such as MLL-AF9, MLL-GAS7, AML1-ETO, PML-RARα or NUP98-HOXD13. [7][8][9][10][11][12][13] Several studies have shown that FLT3-ITD alone can cause a myeloproliferative disorder in mice, but is not sufficient to induce AML. [14][15][16] NUP98-NSD1 is the product of a cytogenetically silent chromosomal translocation t(5;11) (q35;p15.5) that generates a fusion between the N-terminus of nucleoporin 98 (NUP98) and the C-terminal part of the nuclear receptor-binding SETdomain-containing protein NSD1.…”

Review: genetic models of acute myeloid leukaemia

“…Subsequently, AML/ETO t(8;21) was transduced to bone marrow derived from mice deficient of the interferon regulatory factor ICSBP (Schwieger et al, 2002), implicated as a suppressor of myeloid neoplasia (Holtschke et al, 1996;Gabriele et al, 1999;Scheller et al, 1999) and was found to synergize with ICSBP deficiency to incite myeloblastic conditions evocative of AML. Furthermore, activating mutations in receptor tyrosine kinases, for example TEL/PDGFbR and Flt3, were found to cooperate with AML/ETO (Grisolano et al, 2003), NUP98/HOXA9 t(7;11) (Dash et al, 2002) and PML/RARa t(15;17) (Kelly et al, 2002) causing AML (FAB M2)-type leukaemia, AML and APL, respectively in transduced mice. Concurrently, cotransduction of murine HSCs with mutated tyrosine kinase BCR/ABL and translocation of NUP98/HOXA9 resulted in AML following transplantation into syngeneic mice (Dash et al, 2002).…”

Gene expression changes in normal haematopoietic cells

“…Like many other cancers, multiple genetic, epigenetic, and/or transcriptional events are required to transform normal hematopoietic progenitor/stem cells. [136][137][138][139] Therefore, dysfunctional HPCs/HSCs may acquire the necessary and sufficient transforming events over time, leading to the development of hematopoietic malignancies and explaining the increased incidence of hematopoietic malignancies in older adults. 16 If so, the characterization of the nature and identity of ARECs may provide insight into the biology of normal aging and the development of age-associated diseases such as cancer.…”