Imatinib and nilotinib inhibit hematopoietic progenitor cell growth, but do not prevent adhesion, migration and engraftment of human cord blood CD34+ cells

Drug-Induced Mast Cell Eradication: A Novel Approach to Treat Mast Cell Activation Disorders?

Mast cell activation is a key event in allergic reactions, other inflammatory states, and mast cell activation syndromes. Mast cell-stabilizing agents, mediator-targeting drugs and drugs interfering with mediator effects are often prescribed in these patients. However, the clinical efficacy of these drugs varies, depending on the numbers of involved mast cells and the underlying pathology. One straightforward approach would be to eradicate the primary target cell. However, to date, no mast cell-eradicating treatment approach has been developed for patients suffering from mast cell activation disorders. Nevertheless, recent data suggest that long-term treatment with agents that effectively inhibit KIT-function results in the virtual eradication of tissue mast cells and a sustained decrease in serum tryptase levels. In many of these patients, mast cell depletion is associated with a substantial improvement in mediator-induced symptoms. In patients with an underlying KIT D816V+ mastocytosis, such mast cell eradication requires an effective inhibitor of KIT D816V, such as avapritinib. However, the use of KIT inhibitors must be balanced against potential side effects. We here discuss mast cell-eradicating strategies in various disease models, the feasibility of this approach, available clinical data, and future prospects for the use of KIT-targeting drugs in mast cell activation disorders.

Imatinib-mesylate enhances the maintenance of chronic myeloid leukemia stem cell potential in the absence of glucose

The introduction of BCR/Abl tyrosine kinase inhibitors (TKI), such as imatinib-mesylate (IM), has revolutioned the treatment of chronic myeloid leukemia (CML). However, although extremely effective in inducing CML remission, IM is unable to eliminate leukemia stem cells (LSC). This is largely due to the suppression of BCR/Abl protein, driven by the reduction of energy supply due to oxygen or glucose shortage, in stem cell niches of bone marrow. Here, we investigated whether, in K562 and KCL22 CML cell cultures, glucose shortage induces refractoriness of stem cell potential to IM. In the absence of glucose, IM, while maintaining its detrimental effect on CML cell bulk, actually enhanced colony formation ability and stem cell potential. This was paralleled by an increased expression of the Nanog and Sox-2 stem cell markers. These evidences stress further the importance of developing strategies alternative to TKI capable to target LSC of CML.

Limited Impact of Imatinib in a Murine Model of Sclerodermatous Chronic Graft-versus-Host Disease

BACKGROUND

Sclerodermatous chronic Graft-versus-Host Disease (scl-cGVHD) is one of the most severe form of cGVHD. The Platelet-derived Grotwth Factor (PDGF) and the Transforming Growth Factor-β (TGF-β) play a significant role in the fibrosing process occurring in scl-cGVHD. This prompted us to assess the impact of the PDGF-r and c-Abl tyrosine kinase inhibitor imatinib on scl-cGVHD.

METHODS

To assess the impact of imatinib on T cell subset proliferation in vivo, Balb/cJ recipient mice were lethally (7 Gy) irradiated and then injected with 10x106 bone marrow cells from B10.D2 mice on day 0. Fourteen days later, 70x106 carboxyfluorescein succinimidyl ester (CFSE)-labeled splenocytes from B10.D2 mice were infused and imatinib or sterile water was administered for 5 days. To induce severe scl-cGVHD, Balb/cJ mice were injected i.v. with 10.106 bone marrow cells and 70.106 splenocytes from B10.D2 donor mice after 7 Gy irradiation. Mice were then given sterile water or imatinib from day +7 after transplantation to the end of the experiment (day +52).

RESULTS

Imatinib decreased the proliferation of total T cells (P = 0.02), CD8+ T cells (P = 0.01), and of regulatory T cells (Tregs) (P = 0.02) in the spleen. In the severe scl-cGVHD model, imatinib-treated mice had significantly lower levels of PDGF-r phosphorylation than control mice on day 29 after transplantation (P = 0.008). However, scl-cGVHD scores were similar between vehicle- and imatinib-treated mice during the whole experiment, while there was a suggestion for less weight loss in imatinib-treated mice that reached statistical significance at day +52 following transplantation (P = 0.02).

CONCLUSIONS

Imatinib had a limited impact in murine scl-cGVHD despite significant inhibition of PDGF-r.

miR-17 promotes expansion and adhesion of human cord blood CD34(+) cells in vitro

Introduction

We have recently found that miR-17 is necessary in the cell-extrinsic control of cord blood (CB) CD34⁺ cell function. Here, we demonstrated that the proper level of miR-17 is also necessary in the cell-intrinsic control of the hematopoietic properties of CB CD34⁺ cells.

Methods

The miR-17 overexpression and knockdown models were created using primary CB CD34⁺ cells transfected by the indicated vectors. Long-term culture, colony forming, adhesion and trans-well migration assays were carried out to investigate the function of miR-17 on CB CD34⁺ cells in vitro. NOD prkdc^scid Il2rg^null mice were used in a SCID repopulating cell assay to investigate the function of miR-17 on CB CD34⁺ cells in vivo. A two-tailed Student’s t-test was used for statistical comparisons.

Results

In vitro assays revealed that ectopic expression of miR-17 promoted long-term expansion, especially in the colony-forming of CB CD34⁺ cells and CD34⁺CD38⁻ cells. Conversely, downregulation of miR-17 inhibited the expansion of CB CD34⁺ cells. However, the overexpression of miR-17 in vivo reduced the hematopoietic reconstitution potential of CB CD34⁺ cells compared to that of control cells. The increased expression of major adhesion molecules in miR-17 overexpressed CB CD34⁺ cells suggests that the adhesion between miR-17 overexpressed CB CD34⁺ cells and their niche in vivo is regulated abnormally, which may further lead to the reduced hematopoietic reconstitution capability of 17/OE cells in engrafted mice.

Conclusion

We conclude that the proper expression of miR-17 is required, at least partly, for normal hematopoietic stem cell–niche interaction and for the regulation of adult hematopoiesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0159-1) contains supplementary material, which is available to authorized users.

Alternative methods in toxicology: CFU assays application, limitation and future prospective

Blood is a fluid connective tissue which plays a vital role for normal body function. It consist different type of blood cells which is continuously reproduce inside the bone marrow from hematopoietic system. Xenobiotics could be specifically toxic to the hematopoietic system and they can cause hematological disorders by disturbing the normal functions. In vitro hematopoietic colony-forming cell assays play a crucial role to evaluate potential toxic effects of new xenobiotics and also helpful in bridging the gap between preclinical toxicology studies in animal models and clinical investigations. Use of these assays in conjunction with, high-throughput screening reduces the cost and time associated with these assays. This article provides a critical view over in vitro hematopoietic colony-forming cell assays in assessment of hematotoxicity.