Quantitative trait loci associated with susceptibility to therapy-related acute murine promyelocytic leukemia in hCG-PML/RARA transgenic mice

Dunaliella salina exhibits an antileukemic immunity in a mouse model of WEHI-3 leukemia cells

Dunaliella salina has been shown to have antioxidant property and induce apoptotic cell death of human cancer cells in vitro. However, there is no information available on D. salina showing an antileukemia effect or immunomodulatory activity in vivo. This study applied D. salina to syngeneic leukemia-implanted mice (BALB/c and WEHI-3) to investigate its immunological and antileukemia properties. Oral administration of D. salina (184.5, 369, and 922.5 mg/kg) inhibited spleen metastasis and prolonged the survival in BALB/c mice that had received an intravenous injection of WEHI-3 cells. The results revealed that D. salina had reduced spleen enlargement in murine leukemia. It had also increased the population and proliferation of T-cells (CD3) and B-cells (CD19) following Con A/LPS treatment on flow cytometry and MTT assay, respectively. Furthermore, D. salina increased the phagocytosis of macrophages and enhanced the cytotoxicity of natural killer cells on flow cytometry and LDH assay. Moreover, D. salina enhanced the levels of interferon-γ and interleukin 2 (IL-2) but reduced the levels of IL-4 and IL-10 in leukemic mice. In conclusion, these results demonstrated that the application of D. salina had beneficial effects on WEHI-3 leukemic mice by prolonging survival via modulating the immune responses.

Murine xenogeneic models of myelodysplastic syndrome: an essential role for stroma cells

The objective of is this article is to review murine xenotransplantation models for myelodysplastic syndromes (MDS). The difficulties in achieving sustained engraftment of MDS cells in immunodeficient mice may lie in innate characteristics of the MDS clones and microenvironmental factors. Engraftment of very low numbers of CD45(+) clonal MDS cells has been achieved with intravenous injection; higher rates of engraftment are obtained via the intramedullary route. Coinjection of certain stroma components with hematopoietic cells overcomes limitations of intravenous (IV) administration, allowing for engraftment of high proportions of human CD45(+) cells in mouse spleen and marrow. Expression of CD146 on stroma cells conveys an engraftment-facilitating effect. Clonal MDS cells have been propagated for periods beyond 6 months and have been transplanted successfully into secondary recipients. Engraftment of human clonal MDS cells with stem cell characteristics in immunodeficient mice is greatly facilitated by coinjection of stroma/mesenchymal cells, particularly with IV administration. CD146 expression on stroma is an essential factor; however, no model develops the laboratory and clinical features of human MDS. Additional work is needed to determine cellular and noncellular factors required for the full evolution of MDS.

Role and fate of SP100 protein in response to Rep-dependent nonviral integration system

Previously, we studied an AAVS1 site-specific non-viral integration system with a Rep-donor plasmid and a plasmid containing adeno-associated virus integration element. Our earlier study focused on the plasmid vector itself, but the cellular response to the system was still unknown. SP100 is a member of the promyelocytic leukemia nuclear bodies. It is involved in many cellular processes such as transcriptional regulation and the cellular intrinsic immune response against viral infection. In this study, we revealed that SP100 inhibited the Rep-dependent nonviral integration. Conversely, transient expression of Rep78 increased the degradation of SP100. This degradation was inhibited by treatment with MG132, an inhibitor of the ubiquitin proteasome. SP100 and Rep78 are both located in the nucleolus, which provides the spatial possibility for their interaction. Rep78 was coimmunoprecipitated with the enhanced green fluorescent protein (EGFP)-SP100 fusion protein but not EGFP, which verified the interaction between Rep78 and SP100. These results have enriched our knowledge about the cellular protein SP100 and Rep-dependent nonviral integration. It may lead to an improvement in the application of Rep-related transgene integration method and in the selection of target cells.

The origin and evolution of mutations in acute myeloid leukemia

Most mutations in cancer genomes are thought to be acquired after the initiating event, which may cause genomic instability and drive clonal evolution. However, for acute myeloid leukemia (AML), normal karyotypes are common, and genomic instability is unusual. To better understand clonal evolution in AML, we sequenced the genomes of M3-AML samples with a known initiating event (PML-RARA) versus the genomes of normal karyotype M1-AML samples and the exomes of hematopoietic stem/progenitor cells (HSPCs) from healthy people. Collectively, the data suggest that most of the mutations found in AML genomes are actually random events that occurred in HSPCs before they acquired the initiating mutation; the mutational history of that cell is "captured" as the clone expands. In many cases, only one or two additional, cooperating mutations are needed to generate the malignant founding clone. Cells from the founding clone can acquire additional cooperating mutations, yielding subclones that can contribute to disease progression and/or relapse.

Novel quinazolinone MJ-29 triggers endoplasmic reticulum stress and intrinsic apoptosis in murine leukemia WEHI-3 cells and inhibits leukemic mice

The present study was to explore the biological responses of the newly compound, MJ-29 in murine myelomonocytic leukemia WEHI-3 cells in vitro and in vivo fates. We focused on the in vitro effects of MJ-29 on ER stress and mitochondria-dependent apoptotic death in WEHI-3 cells, and to hypothesize that MJ-29 might fully impair the orthotopic leukemic mice. Our results indicated that a concentration-dependent decrease of cell viability was shown in MJ-29-treated cells. DNA content was examined utilizing flow cytometry, whereas apoptotic populations were determined using annexin V/PI, DAPI staining and TUNEL assay. Increasing vital factors of mitochondrial dysfunction by MJ-29 were further investigated. Thus, MJ-29-provaked apoptosis of WEHI-3 cells is mediated through the intrinsic pathway. Importantly, intracellular Ca²⁺ release and ER stress-associated signaling also contributed to MJ-29-triggered cell apoptosis. We found that MJ-29 stimulated the protein levels of calpain 1, CHOP and p-eIF2α pathways in WEHI-3 cells. In in vivo experiments, intraperitoneal administration of MJ-29 significantly improved the total survival rate, enhanced body weight and attenuated enlarged spleen and liver tissues in leukemic mice. The infiltration of immature myeloblastic cells into splenic red pulp was reduced in MJ-29-treated leukemic mice. Moreover, MJ-29 increased the differentiations of T and B cells but decreased that of macrophages and monocytes. Additionally, MJ-29-stimulated immune responses might be involved in anti-leukemic activity in vivo. Based on these observations, MJ-29 suppresses WEHI-3 cells in vitro and in vivo, and it is proposed that this potent and selective agent could be a new chemotherapeutic candidate for anti-leukemia in the future.

PML-RARA can increase hematopoietic self-renewal without causing a myeloproliferative disease in mice

Acute promyelocytic leukemia (APL) is characterized by the t(15;17) translocation that generates the fusion protein promyelocytic leukemia-retinoic acid receptor α (PML-RARA) in nearly all cases. Multiple prior mouse models of APL constitutively express PML-RARA from a variety of non-Pml loci. Typically, all animals develop a myeloproliferative disease, followed by leukemia in a subset of animals after a long latent period. In contrast, human APL is not associated with an antecedent stage of myeloproliferation. To address this discrepancy, we have generated a system whereby PML-RARA expression is somatically acquired from the mouse Pml locus in the context of Pml haploinsufficiency. We found that physiologic PML-RARA expression was sufficient to direct a hematopoietic progenitor self-renewal program in vitro and in vivo. However, this expansion was not associated with evidence of myeloproliferation, more accurately reflecting the clinical presentation of human APL. Thus, at physiologic doses, PML-RARA primarily acts to increase hematopoietic progenitor self-renewal, expanding a population of cells that are susceptible to acquiring secondary mutations that cause progression to leukemia. This mouse model provides a platform for more accurately dissecting the early events in APL pathogenesis.

Treatment-related myelodysplastic syndrome: molecular characteristics and therapy

PURPOSE OF REVIEW

Treatment-related myelodysplastic syndrome (t-MDS) is a serious complication of cancer treatment. Here we review recent advances in knowledge of the risk factors, pathogenesis, and treatment of t-MDS.

RECENT FINDINGS

Recent studies have provided important new information regarding genetic risk factors that may predispose individual patients to develop t-MDS after exposure to cytotoxic therapeutic agents and that may be used to predict individuals at enhanced risk for this complication. The role of specific candidate genes associated with commonly involved genetic lesions in the pathogenesis of t-MDS has also been investigated. Finally, factors determining outcomes of transplantation treatment for this disorder have been elucidated. Hematopoietic cell transplantation provides potentially curative therapy for t-MDS, but additional improvements are necessary to improve outcomes.

SUMMARY

Improved understanding of genetic risk factors is expected to facilitate early identification of patients at risk for t-MDS, guiding therapeutic decision making, and allowing early application of preventive or therapeutic strategies.

Mouse models of myelodysplastic syndromes

Three general approaches have been used to model myelodysplastic syndrome (MDS) in mice, including treatment with mutagens or carcinogens, xenotransplantation of human MDS cells, and genetic engineering of mouse hematopoietic cells. This article discusses the phenotypes observed in available mouse models for MDS with a concentration on a model that leads to aberrant expression of conserved homeobox genes that are important regulators of normal hematopoiesis. Using these models of MDS should allow a more complete understanding of the disease process and provide a platform for preclinical testing of therapeutic approaches.