Engraftment, fate, and function of HoxB8-conditional neutrophil progenitors in the unconditioned murine host

The development and use of murine myeloid progenitor cell lines that are conditionally immortalized through expression of HoxB8 has provided a valuable tool for studies of neutrophil biology. Recent work has extended the utility of HoxB8-conditional progenitors to the in vivo setting via their transplantation into irradiated mice. Here, we describe the isolation of HoxB8-conditional progenitor cell lines that are unique in their ability to engraft in the naïve host in the absence of conditioning of the hematopoietic niche. Our results indicate that HoxB8-conditional progenitors engraft in a β1 integrin-dependent manner and transiently generate donor-derived mature neutrophils. Furthermore, we show that neutrophils derived in vivo from transplanted HoxB8-conditional progenitors are mobilized to the periphery and recruited to sites of inflammation in a manner that depends on the C-X-C chemokine receptor 2 and β2 integrins, the same mechanisms that have been described for recruitment of endogenous primary neutrophils. Together, our studies advance the understanding of HoxB8-conditional neutrophil progenitors and describe an innovative tool that, by virtue of its ability to engraft in the naïve host, will facilitate mechanistic in vivo experimentation on neutrophils.

Therapeutic targeting of preleukemia cells in a mouse model of NPM1 mutant acute myeloid leukemia

The initiating mutations that contribute to cancer development are sometimes present in premalignant cells. Whether therapies targeting these mutations can eradicate premalignant cells is unclear. Acute myeloid leukemia (AML) is an attractive system for investigating the effect of preventative treatment because this disease is often preceded by a premalignant state (clonal hematopoiesis or myelodysplastic syndrome). In Npm1c/Dnmt3a mutant knock-in mice, a model of AML development, leukemia is preceded by a period of extended myeloid progenitor cell proliferation and self-renewal. We found that this self-renewal can be reversed by oral administration of a small molecule (VTP-50469) that targets the MLL1-Menin chromatin complex. These preclinical results support the hypothesis that individuals at high risk of developing AML might benefit from targeted epigenetic therapy in a preventative setting.

Human Cytomegalovirus Decreases Major Histocompatibility Complex Class II by Regulating Class II Transactivator Transcript Levels in a Myeloid Cell Line

ABSTRACT Human cytomegalovirus (HCMV) is a ubiquitous pathogen that encodes many proteins to modulate the host immune response. Extensive efforts have led to the elucidation of multiple strategies employed by HCMV to effectively block NK cell targeting of virus-infected cells and the major histocompatibility complex (MHC) class I-primed CD8+ T cell response. However, viral regulation of the MHC class II-mediated CD4+ T cell response is understudied in endogenous MHC class II-expressing cells, largely because the popular cell culture systems utilized for studying HCMV do not endogenously express MHC class II. Of the many cell types infected by HCMV in the host, myeloid cells, such as monocytes, are of particular importance due to their role in latency and subsequent dissemination throughout the host. We investigated the impact of HCMV infection on MHC class II in Kasumi-3 cells, a myeloid-progenitor cell line that endogenously expresses the MHC class II gene, HLA-DR. We observed a significant reduction in the expression of surface and total HLA-DR at 72 h postinfection (hpi) and 120 hpi in infected cells. The decrease in HLA-DR expression was independent of the expression of previously described viral genes that regulate the MHC class II complex or the unique short (US) region of HCMV, a region expressing many immunomodulatory genes. The altered surface level of HLA-DR was not a result of increased endocytosis and degradation but was a result of a reduction in HLA-DR transcripts due to a decrease in the expression of the class II transactivator (CIITA). IMPORTANCE Human cytomegalovirus (HCMV) is an opportunistic herpesvirus that is asymptomatic for healthy individuals but that can lead to severe pathology in patients with congenital infections and immunosuppressed patients. Thus, it is important to understand the modulation of the immune response by HCMV, which is understudied in the context of endogenous MHC class II regulation. Using Kasumi-3 cells as a myeloid progenitor cell model endogenously expressing MHC class II (HLA-DR), this study shows that HCMV decreases the expression of HLA-DR in infected cells by reducing the transcription of HLA-DR transcripts early during infection independently of the expression of previously implicated genes. This is an important finding, as it highlights a mechanism of immune evasion utilized by HCMV to decrease the expression of MHC class II in a relevant cell system that endogenously expresses the MHC class II complex.

Association of Nucleophosmin-1 (NPM1) Expression with Leucocyte Count, Blast Count, and Gingiva Hypertrophy in Acute Myeloid Leukemia De Novo Patients in General Hospital of Dr M Djamil Padang Indonesia

Acute myeloid leukemia (AML) is a malignant disease derived from hematopoietic system characterized by neoplastic transformation of myeloid progenitor cell, present as excessive proliferation and differentiation alteration leading to inhibition of myeloid maturation. From various studies, incident and prevalence of AML these days is increasing in morbidity and mortality. This make AML known with poor prognosis. Nucleophosmin-1 (NPM-1) was established by WHO revision 2016 as prognostic gene marker in AML. Nucleophosmin-1 gene is mutated in 35-60% of AML cases. Recently, molecular biologic development suggests that prognostic gene examination is needed to reduce morbidity and mortality of AML patients. If myeloid progenitor cell encounters carcinogenic/leukemogenic stresses, mutation of several genes could happen. NPM1 gene is a likely mutated gene and predominantly located in nucleolus. Overexpression of NPM1 will promote activities of tumor suppressors like P53, ARF and MDM2. Interactions of those tumor suppressors promote proliferation, differentiation, cell survival, apoptosis and DNA repair, which give a better prognosis in AML patients. To study about association of NPM1 expression with leucocyte count, blast count, and gingiva hypertrophy in AML de novo patients in general hospital of Dr M Djamil Padang, Indonesia. Analytic observational study with cross-sectional approach to 25 adult AML patients from Policlinic and Inpatient Installation of Dr M Djamil Hospital from March to August 2018 who met inclusion and exclusion criteria. Expression of NPM1 was measured with qRT-PCR. We found significant increase of NPM1 expression in AML in the amount of 22.62x107 copies/ml. There was a significant very strong correlation between NPM1 expression and leucocyte count (p<0.05 & r=0.870) and blast count (p<0.05 & r=0.828). There was also significant differences of NPM1 expression in AML patients with gingival hypertrophy and without gingival hypertrophy (31.3 x 107 copies/ml dan 9.6 x 107 copies/ml). There was a significant very strong correlation between NPM1 expression with leucocyte count and blast count. There was significant increases of NPM1 expression in AML patients with gingival hypertrophy. Keywords: acute myeloid leukemia, Nucleophosmin-1, leucocyte, blast, gingival hypertrophy Disclosures No relevant conflicts of interest to declare.