Kindlin-3 loss curbs chronic myeloid leukemia in mice by mobilizing leukemic stem cells from protective bone marrow niches.

Kindlin-3 (K3)-mediated integrin adhesion controls homing and bone marrow (BM) retention of normal hematopoietic cells. However, the role of K3 in leukemic stem cell (LSC) retention and growth in the remodeled tumor-promoting BM is unclear. We report that loss of K3 in a mouse model of chronic myeloid leukemia (CML) triggers the release of LSCs from the BM into the circulation and impairs their retention, proliferation, and survival in secondary organs, which curbs CML development, progression, and metastatic dissemination. We found de novo expression of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) on CML-LSCs but not normal hematopoietic stem cells and this enabled us to specifically deplete K3 with a CTLA-4-binding RNA aptamer linked to a K3-siRNA (small interfering RNA) in CTLA-4+ LSCs in vivo, which mobilized LSCs in the BM, induced disease remission, and prolonged survival of mice with CML. Thus, disrupting interactions of LSCs with the BM environment is a promising strategy to halt the disease-inducing and relapse potential of LSCs.

The Bone's Role in Myeloid Neoplasia.

The interaction of hematopoietic stem and progenitor cells with their direct neighboring cells in the bone marrow (the so called hematopoietic niche) evolves as a key principle for understanding physiological and malignant hematopoiesis. Significant progress in this matter has recently been achieved making use of emerging high-throughput techniques that allow characterization of the bone marrow microenvironment at single cell resolution. This review aims to discuss these single cell findings in the light of other conventional niche studies that together define the current notion of the niche's implication in i) normal hematopoiesis, ii) myeloid neoplasms and iii) disease-driving pathways that can be exploited to establish novel therapeutic strategies in the future.

Female reproductive potential after oncological treatment: a rare case report of acute myeloid leukemia in monozygotic twin sisters with literature review.

BACKGROUND: Acute myeloid leukemia (AML) in monozygotic twins is a rare event and, until now, only a few cases have been reported. Due to improved oncological treatment and cancer survival rates, quality of life considerations post-treatment have become an important aspect in the treatment regime. The ability to have their own biological children is considered one of the most important indicators of quality of life by cancer survivors. As fertility following oncological treatment is often impaired, fertility preservation methods should be offered to these patients prior to the treatment. Here, we present a very rare case in which we can in vivo observe the impact of oncological treatment on female fertility when applied before and after puberty. CASE PRESENTATION: This is a very rare case of concordant AML in monozygotic twin sisters. Twin A became sick at the age of 21 months. She was treated with cytostatic medications and then underwent bone marrow transplantation (BMT), the donor being her twin sister B. After 27 years, she is disease free and has regular periods. After trying to conceive for 4 years, she was seen by an infertility specialist. She underwent hysteroscopic uterine septum removal and laparoscopic enucleation of bilateral paraovarian cysts. Following those procedures, she immediately conceived naturally. Twin B became sick at 15 years of age. She was treated with chemotherapy and cranial radiation and relapsed after 10 years. She then received chemotherapy and had a BMT. Until relapse, she had normal menstrual cycles. After the second treatment she became amenorrhoeic and is now part of an oocyte donation program. CONCLUSIONS: This is a case of AML in monozygotic twins who, after treatment, have completely different reproductive potential. They both received oncological treatment, and one of them conceived conceived naturally while the other suffered premature ovarian failure and is not able to have a biological child. Based on the outcome of this case, it appears that the pre-pubertal state truly serves as protection against ovarian failure.

Mixture regression models for the gap time distributions and illness-death processes.

The aim of this study is to provide an analysis of gap event times under the illness-death model, where some subjects experience "illness" before "death" and others experience only "death." Which event is more likely to occur first and how the duration of the "illness" influences the "death" event are of interest. Because the occurrence of the second event is subject to dependent censoring, it can lead to bias in the estimation of model parameters. In this work, we generalize the semiparametric mixture models for competing risks data to accommodate the subsequent event and use a copula function to model the dependent structure between the successive events. Under the proposed method, the survival function of the censoring time does not need to be estimated when developing the inference procedure. We incorporate the cause-specific hazard functions with the counting process approach and derive a consistent estimation using the nonparametric maximum likelihood method. Simulations are conducted to demonstrate the performance of the proposed analysis, and its application in a clinical study on chronic myeloid leukemia is reported to illustrate its utility.

Two myeloid leukemia cases with rare FLT3 fusions.

Genetic rearrangements involving FLT3 are rare and only recently have been detected in myeloid/lymphoid neoplasms associated with eosinophilia (MLN-eos) and chronic myeloproliferative disorders. Here we report two cases with FLT3 fusions in patients demonstrating mixed features of myelodysplastic/myeloproliferative neoplasms. In the first case, FLT3 was fused with a new fusion partner MYO18A in a patient with marrow features most consistent with atypical chronic myeloid leukemia; the second case involving ETV6-FLT3 fusion was observed in a case with bone marrow features most consistent with chronic myelomonocytic leukemia. Notably, we observed that samples from both patients demonstrated FLT3 inhibitor (quizartinib and sorafenib) sensitivity in ex vivo drug screening assay.

Insulin Substrate Receptor (IRS) proteins in normal and malignant hematopoiesis.

The insulin receptor substrate (IRS) proteins are a family of cytoplasmic proteins that integrate and coordinate the transmission of signals from the extracellular to the intracellular environment via transmembrane receptors, thus regulating cell growth, metabolism, survival and proliferation. The PI3K/AKT/mTOR and MAPK signaling pathways are the best-characterized downstream signaling pathways activated by IRS signaling (canonical pathways). However, novel signaling axes involving IRS proteins (noncanonical pathways) have recently been identified in solid tumor and hematologic neoplasm models. Insulin receptor substrate-1 (IRS1) and insulin receptor substrate-2 (IRS2) are the best-characterized IRS proteins in hematologic-related processes. IRS2 binds to important cellular receptors involved in normal hematopoiesis (EPOR, MPL and IGF1R). Moreover, the identification of IRS1/ABL1 and IRS2/JAK2V617F interactions and their functional consequences has opened a new frontier for investigating the roles of the IRS protein family in malignant hematopoiesis. Insulin receptor substrate-4 (IRS4) is absent in normal hematopoietic tissues but may be expressed under abnormal conditions. Moreover, insulin receptor substrate-5 (DOK4) and insulin receptor substrate-6 (DOK5) are linked to lymphocyte regulation. An improved understanding of the signaling pathways mediated by IRS proteins in hematopoiesis-related processes, along with the increased development of agonists and antagonists of these signaling axes, may generate new therapeutic approaches for hematological diseases. The scope of this review is to recapitulate and review the evidence for the functions of IRS proteins in normal and malignant hematopoiesis.

The BMP pathway: A unique tool to decode the origin and progression of leukemia.

The microenvironment (niche) governs the fate of stem cells (SCs) by balancing self-renewal and differentiation. Increasing evidence indicates that the tumor niche plays an active role in cancer, but its important properties for tumor initiation progression and resistance remain to be identified. Clinical data show that leukemic stem cell (LSC) survival is responsible for disease persistence and drug resistance, probably due to their sustained interactions with the tumor niche. Bone morphogenetic protein (BMP) signaling is a key pathway controlling stem cells and their niche. BMP2 and BMP4 are important in both the normal and the cancer context. Several studies have revealed profound alterations of the BMP signaling in cancer SCs, with major deregulations of the BMP receptors and their downstream signaling elements. This was illustrated in the hematopoietic system by pioneer studies in chronic myelogenous leukemia that may now be expanded to acute myeloid leukemia and lymphoid leukemia, as reviewed here. At diagnosis, cells from the leukemic microenvironment are the major providers of soluble BMPs. Conversely, LSCs display altered receptors and downstream BMP signaling elements accompanied by altered functional responses to BMPs. These studies reveal the role of BMPs in tumor initiation, in addition to their known effects in later stages of transformation and progression. They also reveal the importance of BMPs in fueling cell transformation and expansion by overamplifying a natural SC response. This mechanism may explain the survival of LSCs independently of the initial oncogenic event and therefore may be involved in resistance processes.

Insulin Substrate Receptor (IRS) proteins in normal and malignant hematopoiesis

The insulin receptor substrate (IRS) proteins are a family of cytoplasmic proteins that integrate and coordinate the transmission of signals from the extracellular to the intracellular environment via transmembrane receptors, thus regulating cell growth, metabolism, survival and proliferation. The PI3K/AKT/mTOR and MAPK signaling pathways are the best-characterized downstream signaling pathways activated by IRS signaling (canonical pathways). However, novel signaling axes involving IRS proteins (noncanonical pathways) have recently been identified in solid tumor and hematologic neoplasm models. Insulin receptor substrate-1 (IRS1) and insulin receptor substrate-2 (IRS2) are the best-characterized IRS proteins in hematologic-related processes. IRS2 binds to important cellular receptors involved in normal hematopoiesis (EPOR, MPL and IGF1R). Moreover, the identification of IRS1/ABL1 and IRS2/JAK2V617F interactions and their functional consequences has opened a new frontier for investigating the roles of the IRS protein family in malignant hematopoiesis. Insulin receptor substrate-4 (IRS4) is absent in normal hematopoietic tissues but may be expressed under abnormal conditions. Moreover, insulin receptor substrate-5 (DOK4) and insulin receptor substrate-6 (DOK5) are linked to lymphocyte regulation. An improved understanding of the signaling pathways mediated by IRS proteins in hematopoiesis-related processes, along with the increased development of agonists and antagonists of these signaling axes, may generate new therapeutic approaches for hematological diseases. The scope of this review is to recapitulate and review the evidence for the functions of IRS proteins in normal and malignant hematopoiesis.

Myeloid leukemia factor 1 interfered with Bcl-XL to promote apoptosis and its function was regulated by 14-3-3

Myeloid leukemia factor 1 (MLF1) was involved in t(3;5) chromosomal rearrangement and aberrantly expressed in myelodysplastic syndromes/acute myeloid leukemia patients. Ex vivo experiments showed that the lymphocytes from the Mlf1-deficient mice were more resistant to apoptotic stimulations than the wild-type cells. Furthermore, the ectopically expressed MLF1 induced apoptosis in the cell models. These findings revealed that MLF1 was required for the cells to respond to the apoptotic stimulations. Ex vivo experiments also demonstrated that cytokine withdrawal significantly up-regulated Mlf1’s expression and promoted its association with B cell lymphoma-extra large (Bcl-XL) in the lymphocytes, at the same time reduced the association of Bax with Bcl-XL The same effects were also observed in the cells that over-expressed MLF1. However, these effects were observed in Mlf1 null lymphocytes as well as the cells over-expressing Bcl-XL. In addition, MLF1’s proapoptosis could be completely prevented by co-expression of Bcl-XL and significantly attenuated in Bax/Bak double null cells. These data, taken together, strongly suggested that in response to the stresses, up-regulated Mlf1 promoted its association with Bcl-XL and reduced the available Bcl-XL for associating with Bax, which resulted in releasing Bax from the Bcl-XL and apoptosis in turn. Lastly, we showed that MLF1 was negatively regulated by 14-3-3 and revealed that 14-3-3 bound to MLF1 and physically blocked MLF1’s Bcl-2 homology domain 3 (BH3) as well as Bcl-XL from associating with MLF1. Our findings suggested that ectopically expressed MLF1 could be responsible for the pathological apoptosis in early myelodysplastic syndrome (MDS) patients

Neural regulation of hematopoiesis, inflammation, and cancer.

Although the function of the autonomic nervous system (ANS) in mediating the flight-or-fight response was recognized decades ago, the crucial role of peripheral innervation in regulating cell behavior and response to the microenvironment has only recently emerged. In the hematopoietic system, the ANS regulates stem cell niche homeostasis and regeneration and fine-tunes the inflammatory response. Additionally, emerging data suggest that cancer cells take advantage of innervating neural circuitry to promote their progression. These new discoveries outline the need to redesign therapeutic strategies to target this underappreciated stromal constituent. Here, we review the importance of neural signaling in hematopoietic homeostasis, inflammation, and cancer.

Loss of c-Cbl E3 ubiquitin ligase activity enhances the development of myeloid leukemia in FLT3-ITD mutant mice.

Mutations in the Fms-like tyrosine kinase 3 (FLT3) receptor tyrosine kinase (RTK) occur frequently in acute myeloid leukemia (AML), with the most common involving internal tandem duplication (ITD) within the juxtamembrane domain. Fms-like tyrosine kinase 3-ITD mutations result in a mislocalized and constitutively activated receptor, which aberrantly phosphorylates signal transducer and activator of transcription 5 (STAT5) and upregulates the expression of its target genes. c-Cbl is an E3 ubiquitin ligase that negatively regulates RTKs, including FLT3, but whether it can downregulate mislocalized FLT3-ITD remains to be resolved. To help clarify this, we combined a FLT3-ITD mutation with a loss-of-function mutation in the RING finger domain of c-Cbl that abolishes its E3 ligase activity. Mice transplanted with hematopoietic stem cells expressing both mutations rapidly develop myeloid leukemia, indicating strong cooperation between the two. Although the c-Cbl mutation was shown to cause hyperactivation of another RTK, c-Kit, it had no effect on enhancing FLT3-ITD protein levels or STAT5 activation. This indicates that c-Cbl does not downregulate FLT3-ITD and that the leukemia is driven by independent pathways involving FLT3-ITD's activation of STAT5 and mutant c-Cbl's activation of other RTKs, such as c-Kit. This study highlights the importance of c-Cbl's negative regulation of wild-type RTKs in suppressing FLT3-ITD-driven myeloid leukemia.

Stem cell fate regulation by dynein motor protein Lis1.

Cell fate regulation is a central component of maintaining tissue homeostasis, yet the mechanisms instructing cell division diversity in tissue-specific stem cells have not been well understood. A new study uncovers a central role for microtubule motor-regulating protein Lis1 in hematopoietic stem cell fate determination and in leukemogenesis.

Lis1 regulates asymmetric division in hematopoietic stem cells and in leukemia.

Cell fate can be controlled through asymmetric division and segregation of protein determinants, but the regulation of this process in the hematopoietic system is poorly understood. Here we show that the dynein-binding protein Lis1 is critically required for hematopoietic stem cell function and leukemogenesis. Conditional deletion of Lis1 (also known as Pafah1b1) in the hematopoietic system led to a severe bloodless phenotype, depletion of the stem cell pool and embryonic lethality. Further, real-time imaging revealed that loss of Lis1 caused defects in spindle positioning and inheritance of cell fate determinants, triggering accelerated differentiation. Finally, deletion of Lis1 blocked the propagation of myeloid leukemia and led to a marked improvement in survival, suggesting that Lis1 is also required for oncogenic growth. These data identify a key role for Lis1 in hematopoietic stem cells and mark its directed control of asymmetric division as a critical regulator of normal and malignant hematopoietic development.

The ecology in the hematopoietic stem cell niche determines the clinical outcome in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is a blood disease that disrupts normal function of the hematopoietic system. Despite the great progress made in terms of molecular therapies for CML, there remain large gaps in our understanding. By comparing mathematical models that describe CML progression and etiology we sought to identify those models that provide the best description of disease dynamics and their underlying mechanisms. Data for two clinical outcomes--disease remission or relapse--are considered, and we investigate these using Bayesian inference techniques throughout. We find that it is not possible to choose between the models based on fits to the data alone; however, by studying model predictions we can discard models that fail to take niche effects into account. More detailed analysis of the remaining models reveals mechanistic differences: for one model, leukemia stem cell dynamics determine the disease outcome; and for the other model disease progression is determined at the stage of progenitor cells, in particular by differences in progenitor death rates. This analysis also reveals distinct transient dynamics that will be experimentally accessible, but are currently at the limits of what is possible to measure. To resolve these differences we need to be able to probe the hematopoietic stem cell niche directly. Our analysis highlights the importance of further mapping of the bone marrow hematopoietic niche microenvironment as the "ecological" interactions between cells in this niche appear to be intricately linked to disease outcome.

[Clinical and functional symptoms of funicular myelosis and chronic gastritis in patients with B12-deficiency anemia].

The aim of this work was to study clinical and functional symptoms of funicular myelosis (FM) and chronic gastritis (CG) in patients with B12-deficiency anemia. A total of 77 patients with diagnosis verified by finding megaloblasts in bone marrow biopsies were examined. Clinical symptoms of FM were found in 57% of the patients. The most characteristic subjective ones were paresthesia (83.3%) and limb weakness (60%) while objective symptoms included impaired limb sensitivity (100%). All patients suffered CG with lesions in both antrum and fundus.

Tempranillo-derived grape seed extract induces apoptotic cell death and cell growth arrest in human promyelocytic leukemia HL-60 cells.

Although grape seed extract (GSE) has proven to be effective against various cancers, few studies have investigated the effects of GSE on human leukemia. In this study, we analysed the mechanisms involved in the apoptotic effects induced by GSE on human promyelocytic leukemia HL-60 cells. Thus, GSE treatment succeeded in activating caspase-3 (P < 0.05), the activation being dose-dependent and time-dependent. Activation of caspase-3 induced by GSE was accompanied by mitochondrial membrane depolarization (P < 0.05). Moreover, disruption of mitochondrial integrity caused by GSE treatment subsequently led to activation of caspase-9 (P < 0.05), and also produced a slight increase in ROS levels (P < 0.05). Cytotoxic effects elicited by GSE treatment ultimately resulted in extensive S-phase arrest (P < 0.05) and a substantial increase in the intrinsic rate of apoptosis (P < 0.05). Our findings suggest that the GSE induces apoptotic cell death and cell growth inhibition in human leukemic HL-60 cells, which seems to be dependent on mitochondrial damage. Therefore, the GSE obtained from Tempranillo cultivars could be an effective approach to restrain uncontrolled cell proliferation and survival in leukemia cells.

BMP4 is involved in the chemoresistance of myeloid leukemia cells through regulating autophagy-apoptosis balance.

This study showed that silencing BMP4 expression significantly activated caspase-2, 3, and 9, while decreasing Matrigel colony formation in Cytarabine (Ara-C)-treated leukemia HL-60 cells. In contrast, Ara-C significantly upregulated Atg5 and Beclin-1 expression, the ratio of LC3-II/LC3-I, and CDK1 and cyclin B1 expression in leukemia cells expressing BMP4. BafA significantly sensitized the apoptotic effect of Ara-C in leukemia cells. Injection of Ara-C significantly inhibited tumor growth in mice inoculated with leukemia cells with BMP4 silenced. In conclusion, BMP4 plays a crucial role in the chemoresistance of leukemia cells through the activation of autophagy and subsequent inhibition of apoptosis.

Antiproliferative effect of H2O2 against human acute myelogenous leukemia KG1 cell line.

It has clearly been established that oxidative stress leads to perturbation of various cellular processes resulting in either inhibition of cell proliferation or cell death. In addition, there is a growing body of evidence indicating that reactive oxygen species (ROS) are required as signal molecules that regulate different physiological processes including survival or death. Free radicals, particularly ROS, have been proposed as general mediators for apoptosis and recent studies have established that the mode of cell death depends on the severity of the oxidative damage. In this study, we determined the effect of oxidative stress on cell proliferation and characterization of cell death in human KG1 cells treated with H2O2. Our results indicated that oxidative stress leads to a significant decrease in cell proliferation and induction of apoptosis. Moreover, our study suggests that antiproliferative and apoptotic cell death effects of H2O2 took place via activation of caspase-3, affecting the expression of Bcl-2 and Bax (an antiapoptotic and a proapoptotic factor, respectively), and through deactivation of catalase enzyme, leading to accumulation of intracellular ROS and depletion of intracellular ATP level.

Ant 4,4, a polyamine-anthracene conjugate, induces cell death and recovery in human promyelogenous leukemia cells (HL-60).

One of the major problems in cancer therapy is the lack of specificity of chemotherapeutic agents towards cancer cells, resulting in adverse side effects. One means to counter this is to selectively deliver the drug to the cancer cell. Cancer cells accumulate increased concentrations of polyamines compared to normal cells, mainly through an increased uptake of preformed polyamines via the polyamine transport system (PTS). Furthermore, the non-stringent structural requirements of the PTS enable the transport of a range of polyamine-based molecules. Thus, the PTS can be used to transport compounds linked to polyamines selectively to cancer cells. In our laboratory, polyamine-anthracene conjugates have shown potent anti-tumour activity towards HL-60 cells. The aim of this study was to determine the cytotoxicity of Ant-4,4, a homospermidine-anthracene conjugate, and assess the long-term effects by determining whether cancer cells were able to recover from treatment. During exposure, Ant-4,4 was an effective growth-inhibitory agent in HL-60 cells decreasing viable cell number, protein and polyamine content. Evidence indicates concomitant cell-cycle arrest and increased apoptosis. Once the drug was removed, HL-60 cells recovered gradually over time. Increasing cell number, protein content and polyamine content, as well as diminished effects on cell-cycle and apoptotic stimuli were observed over time. These data suggest that, despite being an effective way of delivering anthracene, these polyamine conjugates do not exert long-lasting effects on HL-60 cells.