Suppression of SOX7 by DNA methylation and its tumor suppressor function in acute myeloid leukemia.

SOX7 belongs to the SOX (Sry-related high-mobility group [HMG] box) gene family, a group of transcription factors containing in common a HMG box domain. Its role in hematologic malignancies and, in particular, acute myeloid leukemia (AML) is completely unknown. Here, we showed that SOX7 expression was regulated by DNA hypermethylation in AML but not in acute lymphoblastic leukemia or normal bone marrow cells. In cell lines (KG1, ML2, and K562) and in primary CD34(+) AML samples, SOX7 expression could be induced by the DNA demethylating agent 5-aza-2'-deoxycytidine. Overexpression of SOX7 in K562 cells inhibited cell proliferation, with cell cycle delay in S/G2/M phases and reduced clonogenic activity. Apoptosis was unaffected. Ectopic expression of SOX7 in K562 and THP-1 cells, as well as primary CD33(+)CD34(+) AML cells, abrogated leukemia engraftment in xenogeneic transplantation. SOX7 expression inhibited the Wnt/ß-catenin pathway through direct protein binding to ß-catenin, and the antileukemia effects of SOX7 in THP-1 cells were significantly reduced by deletion of its ß-catenin binding site. The results provided unequivocal evidence for a novel tumor suppressor role of SOX7 in AML via a negative modulatory effect on the Wnt/ß-catenin pathway.

Successful engraftment by leukemia initiating cells in adult acute lymphoblastic leukemia after direct intrahepatic injection into unconditioned newborn NOD/SCID mice.

OBJECTIVE: Xenogeneic transplantation has been the gold standard for enumeration of leukemia initiating cells in acute myeloid and lymphoblastic leukemia (ALL). Most transplantation models have required conditioning in which the recipients were either irradiated or treated with chemotherapy prior to injection of human leukemia cells. In this study, we reported an undescribed model in which adult ALL cells were injected into unconditioned newborn nonobese diabetic severe combined immunodeficient mice via an intrahepatic route. MATERIALS AND METHODS: Bone marrow (BM) and peripheral blood were collected from patients with ALL at diagnosis or relapse. CD34(+) selected lymphoblasts or mononuclear cells were transplanted as mentioned previously. Cells were also transplanted into sublethally irradiated adult mice via intravenous route for comparison. Leukemia engraftment was enumerated from mouse BM 6 to 18 weeks after transplantation. Clonality of the engrafting cells was examined based on IGH rearrangement and fluorescent in situ hybridization. RESULTS: Five of 13 ALL samples engrafted into the recipient BM 6 to 18 weeks after transplantation. Engrafted cells recapitulated the immunophenotype and cytogenetic characteristics of the original samples. Engraftment in BM and peripheral blood was significantly correlated. Importantly, there was significant correlation of engraftment between this and the conventional adult nonobese diabetic severe combined immunodeficient mouse model involving irradiation. CONCLUSION: Our results demonstrated that this unconditioned newborn mouse model could be used for enumeration of leukemia initiating cells in ALL and should be further evaluated.

A novel zebrafish jak2a(V581F) model shared features of human JAK2(V617F) polycythemia vera.

OBJECTIVE: The Janus kinase 2 (JAK2) is important for embryonic primitive hematopoiesis. A gain-of-function JAK2 (JAK2(V617F)) mutation in human is pathogenetically linked to polycythemia vera (PV). In this study, we generated a zebrafish ortholog of human JAK2(V617F) (referred herewith jak2a(V581F)) by site-directed mutagenesis and examined its relevance as a model of human PV. MATERIALS AND METHODS: Zebrafish embryos at one-cell stage were injected with jak2a(V581F) mRNA (200pg/embryo). In some experiments, the embryos were treated with a specific JAK2 inhibitor, TG101209. The effects of jak2a stimulation on hematopoiesis, jak/stat signaling, and erythropoietin signaling were evaluated at 18-somites. RESULTS: Injection with jak2a(V581F) mRNA significantly increased erythropoiesis, as enumerated by flow cytometry based on gfp(+) population in dissociated Tg(gata1:gfp) embryos. The response was reduced by stat5.1 morpholino coinjection (control: 4.37% +/- 0.08%; jak2a(V581F) injected: 5.71% +/- 0.07%, coinjecting jak2a(V581F) mRNA and stat5.1 morpholino: 4.66% +/- 0.13%; p<0.01). jak2a(V581F) mRNA also upregulated gata1 (1.83 +/- 0.08 fold; p=0.005), embryonic alpha-hemoglobin (1.61 +/- 0.12 fold; p=0.049), and beta-hemoglobin gene expression (1.65 +/- 0.13-fold; p=0.026) and increased stat5 phosphorylation. These responses were also ameliorated by stat5.1 morpholino coinjection or treatment with a specific JAK2 inhibitor, TG101209. jak2a(V581F) mRNA significantly reduced erythropoietin gene (0.24 +/- 0.03 fold; p=0.006) and protein expression (control: 0.633+/-0.11; jak2a(V581F) mRNA: 0.222+/-0.07 mIU/mL; p=0.019). CONCLUSION: The zebrafish jak2a(V581F) model shared many features with human PV and might provide us with mechanistic insights of this disease.