IGF binding protein 2 is a cell-autonomous factor supporting survival and migration of acute leukemia cells

Extracellular vesicles from type-2 macrophages increase the survival of chronic lymphocytic leukemia cells ex vivo

The resistance of Chronic Lymphocytic Leukemia (CLL) B-cells to cell death is mainly attributed to interactions within their microenvironment, where they interact with various types of cells. Within this microenvironment, CLL-B-cells produce and bind cytokines, growth factors, and extracellular vesicles (EVs). In the present study, EVs purified from nurse-like cells and M2-polarized THP1 cell (M2-THP1) cultures were added to CLL-B-cells cultures. EVs were rapidly internalized by B-cells, leading to a decrease in apoptosis (P = 0.0162 and 0.0469, respectively) and an increased proliferation (P = 0.0335 and 0.0109). Additionally, they induced an increase in the resistance of CLL-B-cells to Ibrutinib, the Bruton kinase inhibitor in vitro (P = 0.0344). A transcriptomic analysis showed an increase in the expression of anti-apoptotic gene BCL-2 (P = 0.0286) but not MCL-1 and an increase in the expression of proliferation-inducing gene APRIL (P = 0.0286) following treatment with EVs. Meanwhile, an analysis of apoptotic protein markers revealed increased amounts of IGFBP-2 (P = 0.0338), CD40 (P = 0.0338), p53 (P = 0.0219) and BCL-2 (P = 0.0338). Finally, exploration of EVs protein content by mass spectrometry revealed they carry various proteins involved in known oncogenic pathways and the RNAseq analysis of CLL-B-cells treated or not with NLCs EVs show various differentially expressed genes.

The role of IGF/IGF-1R signaling in the regulation of cancer stem cells

Cancer stem cells (CSCs) are a group of tumor cells with high tumorigenic ability and self-renewal potential similar to those of normal stem cells. CSCs are the key "seeds" for tumor development, metastasis, and recurrence. A better insight into the key mechanisms underlying CSC survival improves the efficiency of cancer therapy via specific targeting of CSCs. Insulin-like growth factor (IGF)/IGF-1 receptor (IGF-1R) signaling plays an important role in the maintenance of cancer stemness. However, the effect of IGF/IGF-1R signaling on stemness and CSCs and the underlying mechanisms are still controversial. Based on the similarity between CSCs and normal stem cells, this review discusses emerging data on the functions of IGF/IGF-1R signaling in normal stem cells and CSCs and dissects the underlying mechanisms by which IGF/IGF-1R signaling is involved in CSCs. On the other hand, this review highlighted the role of IGF/IGF-1R signaling blockade in multiple CSCs as a potential strategy to improve CSC-based therapy.

A machine learning model identifies M3-like subtype in AML based on PML/RARα targets

The typical genomic feature of acute myeloid leukemia (AML) M3 subtype is the fusion event of PML/RARα, and ATRA/ATO-based combination therapy is current standard treatment regimen for M3 subtype. Here, a machine-learning model based on expressions of PML/RARα targets was developed to identify M3 patients by analyzing 1228 AML patients. Our model exhibited high accuracy. To enable more non-M3 AML patients to potentially benefit from ATRA/ATO therapy, M3-like patients were further identified. We found that M3-like patients had strong GMP features, including the expression patterns of M3 subtype marker genes, the proportion of myeloid progenitor cells, and deconvolution of AML constituent cell populations. M3-like patients exhibited distinct genomic features, low immune activity and better clinical survival. The initiative identification of patients similar to M3 subtype may help to identify more patients that would benefit from ATO/ATRA treatment and deepen our understanding of the molecular mechanism of AML pathogenesis.

A novel AML1-ETO/FTO positive feedback loop promotes leukemogenesis and Ara-C resistance via stabilizing IGFBP2 in t(8;21) acute myeloid leukemia

BACKGROUND

t(8;21)(q22;q22) is one of the most frequent chromosomal abnormalities in acute myeloid leukemia (AML), leading to the generation of the fusion protein AML1-ETO. Despite t(8;21) AML being considered as a subtype with a favorable prognosis, approximately 30-50% of patients experience drug resistance and subsequent relapse. N6-methyladenosine (m6A) is demonstrated to be involved in the development of AML. However, the regulatory mechanisms between AML1-ETO and m6A-related enzymes and the roles of dysregulated m6A modifications in the t(8;21)-leukemogenesis and chemoresistance remain elusive.

METHODS

Chromatin immunoprecipitation, dual-luciferase reporter assay, m6A-qPCR, RNA immunoprecipitation, and RNA stability assay were used to investigate a regulatory loop between AML1-ETO and FTO, an m6A demethylase. Gain- and loss-of-function experiments both in vitro and in vivo were further performed. Transcriptome-wide RNA sequencing and m6A sequencing were conducted to identify the potential targets of FTO.

RESULTS

Here we show that FTO is highly expressed in t(8;21) AML, especially in patients with primary refractory disease. The expression of FTO is positively correlated with AML1-ETO, which is attributed to a positive regulatory loop between the AML1-ETO and FTO. Mechanistically, AML1-ETO upregulates FTO expression through inhibiting the transcriptional repression of FTO mediated by PU.1. Meanwhile, FTO promotes the expression of AML1-ETO by inhibiting YTHDF2-mediated AML1-ETO mRNA decay. Inactivation of FTO significantly suppresses cell proliferation, promotes cell differentiation and renders resistant t(8;21) AML cells sensitive to Ara-C. FTO exerts functions by regulating its mRNA targets, especially IGFBP2, in an m6A-dependent manner. Regain of Ara-C tolerance is observed when IGFBP2 is overexpressed in FTO-knockdown t(8;21) AML cells.

CONCLUSION

Our work reveals a therapeutic potential of targeting AML1-ETO/FTO/IGFBP2 minicircuitry in the treatment for t(8;21) patients with resistance to Ara-C.

Secreted insulin-like growth factor binding protein 5 functions as a tumor suppressor and chemosensitizer through inhibiting insulin-like growth factor 1 receptor/protein kinase B pathway in acute myeloid leukemia

BACKGROUND

In addition to being secreted into the intercellular spaces by exocytosis, insulin-like growth factor binding protein 5 (IGFBP5) may also remain in the cytosol or be transported to the nucleus. Depending on the different cellular context and subcellular distribution, IGFBP5 can act as a tumor suppressor or promoter through insulin-like growth factor -dependent or -independent mechanisms. Yet, little is known about the impacts of IGFBP5 on acute myeloid leukemia (AML) and its underlying mechanism.

METHODS

Here we investigated the roles of IGFBP5 in human AML by using recombinant human IGFBP5 (rhIGFBP5) protein and U937 and THP1 cell lines which stably and ectopically expressed IGFBP5 or mutant IGFBP5 (mtIGFBP5) with the lack of secretory signal peptide. Cell counting kit-8 and flow cytometry assay were conducted to assess the cell viability, cell apoptosis and cell cycle distribution. Cytotoxicity assay was used to detect the chemosensitivity. Leukemia xenograft model and hematoxylin-eosin staining were performed to evaluate AML progression and extramedullary infiltration in vivo.

RESULTS

In silico analysis demonstrated a positive association between IGFBP5 expression and overall survival of the AML patients. Both IGFBP5 overexpression and extrinsic rhIGFBP5 suppressed the growth of THP1 and U937 cells by inducing cell apoptosis and arresting G1/S transition and promoted the chemosensitivity of U937 and THP1 cells to daunorubicin and cytarabine. However, overexpression of mtIGFBP5 failed to demonstrate these properties. An in vivo xenograft mouse model of U937 cells also indicated that overexpression of IGFBP5 rather than mtIGFBP5 alleviated AML progression and extramedullary infiltration. Mechanistically, these biological consequences depended on the inactivation of insulin-like growth factor 1 receptor -mediated phosphatidylinositol-3-kinase/protein kinase B pathway.

CONCLUSIONS

Our findings revealed secreted rather than intracellular IGFBP5 as a tumor-suppressor and chemosensitizer in AML. Upregulation of serum IGFBP5 by overexpression or addition of extrinsic rhIGFBP5 may serve as a suitable therapeutic approach for AML.

Satellite cells sourced from bull calves and dairy cows differs in proliferative and myogenic capacity - Implications for cultivated meat

Cultivated meat produced with primary muscle satellite cells (SCs) will need a continuous supply of isolated cell material from relevant animal donors. Factors such as age, sex, and breed, along with the sustainability and availability of donor animals, could determine the most appropriate donor type for an efficient production. In this study, we focus on the proliferation and differentiation of bovine SCs isolated from bull calf and dairy cow muscle samples. The proliferative performance of bull calf SCs was significantly better than SCs from dairy cows, however a dynamic differentiation assay revealed that the degree of fusion and formation of myotubes were similar between donor types. Furthermore, the proliferation of SCs from both donor types was enhanced using an in-house developed serum-free media compared to 10% FBS, which also delayed myogenic differentiation and increased final cell population density. Using gene chip transcriptomics, we identified several differentially expressed genes between the two donor types, which could help explain the observed cellular differences. This data also revealed a high biological variance between the three replicate animals within donor type, which seemed to be decreased when using our in-house serum-free media. With the use of the powerful imaging modalities of Cytation 5, we developed a novel high contrast brightfield-enabled label-free myotube quantification method along with a more efficient end-point fusion analysis using Phalloidin-staining. The results give new insights into the bovine SC biology and potential use of bull calves and dairy cows as relevant donor animals for cultivated beef cell sourcing. The newly developed differentiation assays will further enhance future research within the field of cultivated meat and SC biology.

Several cell-intrinsic effectors drive type I interferon-mediated restriction of HIV-1 in primary CD4+ T cells

Type I interferon (IFN) upregulates proteins that inhibit HIV within infected cells. Prior studies have identified IFN-stimulated genes (ISGs) that impede lab-adapted HIV in cell lines, yet the ISG(s) that mediate IFN restriction in HIV target cells, primary CD4+ T cells, are unknown. Here, we interrogate ISG restriction of primary HIV in CD4+ T cells by performing CRISPR-knockout screens with a custom library that specifically targets ISGs expressed in CD4+ T cells. Our investigation identifies previously undescribed HIV-restricting ISGs (HM13, IGFBP2, LAP3) and finds that two factors characterized in other HIV infection models (IFI16 and UBE2L6) mediate IFN restriction in T cells. Inactivation of these five ISGs in combination further diminishes IFN's protective effect against diverse HIV strains. This work demonstrates that IFN restriction of HIV is multifaceted, resulting from several effectors functioning collectively, and establishes a primary cell ISG screening model to identify both single and combinations of HIV-restricting ISGs.

Several cell-intrinsic effectors drive type I interferon-mediated restriction of HIV-1 in primary CD4 + T cells

Type I interferon (IFN) upregulates proteins that inhibit HIV within infected cells. Prior studies have identified IFN-stimulated genes (ISGs) that impede lab-adapted HIV in cell lines, yet the ISG(s) that mediate IFN restriction in HIV target cells, primary CD4 + T cells, are unknown. Here, we interrogate ISG restriction of primary HIV in CD4 + T cells. We performed CRISPR-knockout screens using a custom library that specifically targets ISGs expressed in CD4 + T cells and validated top hits. Our investigation identified new HIV-restricting ISGs (HM13, IGFBP2, LAP3) and found that two previously studied factors (IFI16, UBE2L6) are IFN effectors in T cells. Inactivation of these five ISGs in combination further diminished IFN’s protective effect against six diverse HIV strains. This work demonstrates that IFN restriction of HIV is multifaceted, resulting from several effectors functioning collectively, and establishes a primary cell ISG screening model to identify both single and combinations of HIV-restricting ISGs.

Prognostic value of IGFBP2 in various cancers: a systematic review and meta-analysis

BACKGROUND

The prognostic significance of insulin-like growth factor binding protein 2 (IGFBP2) expression has been explored in plenty of studies in human cancers. Because of the controversial results, the meta-analysis was carried out to evaluate the relevance of IGFBP2 expression with the prognosis in various tumors.

METHODS

The data searched from four databases (Pubmed, Embase, Cochrane library, and Web of science) was used to calculate pooled hazard ratios (HRs) in this meta-analysis. Subgroup analyses were stratified by ethnicity, cancer type, publication year, Newcastle-Ottawa Scale score, treatments, and populations.

RESULTS

Twenty-one studies containing 5560 patients finally met inclusion criteria. IGFBP2 expression was associated with lower overall survival (HR = 1.57, 95% CI = 1.31-1.88) and progression-free survival (HR = 1.18, 95% CI = 1.04-1.34) in cancer patients, but not with disease-free survival (HR = 1.50, 95% CI = 0.91-2.46) or recurrence-free survival (HR = 1.50, 95% CI = 0.93-2.40). The subgroup analyses indicated IGFBP2 overexpression was significantly correlated with overall survival in Asian patients (HR = 1.42, 95% CI = 1.18-1.72), Caucasian patients (HR = 2.20, 95% CI = 1.31-3.70), glioma (HR = 1.36, 95% CI = 1.03-1.79), and colorectal cancer (HR = 2.52, 95% CI = 1.43-4.44) and surgery subgroups (HR = 1.97, 95% CI = 1.50-2.58).

CONCLUSION

The meta-analysis showed that IGFBP2 expression was associated with worse prognosis in several tumors, and may serve as a potential prognostic biomarker in cancer patients.

Hymeglusin Enhances the Pro-Apoptotic Effects of Venetoclax in Acute Myeloid Leukemia

Venetoclax is used for the priority treatment of elderly patients with acute myeloid leukemia (AML). Resistance or intolerance to venetoclax offsets its clinical benefits in some patients. Combination strategies with other drugs are promising alternatives to overcome the current complications associated with venetoclax use. Hymeglusin, a specific inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A synthase 1 (HMGCS1), regulates the mevalonate pathway, which is vital for AML growth and chemosensitivity. The effects of the combination of venetoclax and hymeglusin on AML were explored in this study. The correlations between HMGCS1 and apoptosis-related genes were analyzed using the Gene Expression Profiling Interactive Analysis 2 and The Cancer Genome Atlas databases. Apoptosis and cell viability were detected in HL-60 and KG-1 cells after treatment with gradient concentrations of venetoclax or hymeglusin. The transcriptomic profiles of HL-60 and KG-1 cells were compared via RNA-Seq analysis. The effects of venetoclax and hymeglusin on apoptosis were validated in primary cells. The results showed that HMGCS1 expression was closely associated with apoptosis-related genes based on the data from large clinical databases. B cell lymphoma (BCL)-2 expression was elevated in AML and negatively associated with overall survival. Hymeglusin decreased BCL2 expression levels in HL-60 and KG-1 cells. Venetoclax and hymeglusin inhibited cell viability in both cell lines, but induced apoptosis in HL-60 cells. This discrepancy in sensitivity to hymeglusin may be attributed to the positive increase in the expression levels of HMGCS1 and multiple upregulated pro-leukemia genes in KG-1 cells. Combination treatment with venetoclax and hymeglusin significantly increased the apoptotic rates compared to single-agent treatment in both AML cell lines and primary AML cells. Furthermore, the combination strategy did not result in remarkably enhanced toxicity in normal mononuclear cells. Collectively, hymeglusin enhanced the effects of venetoclax on apoptosis. This combination strategy showed enhanced antileukemic activity with acceptable toxicity in AML.

RHOA-regulated IGFBP2 promotes invasion and drives progression of BCR-ABL1 chronic myeloid leukemia

The Philadelphia 9;22 chromosome translocation has two common isoforms that are preferentially associated with distinct subtypes of leukemia. The p210 variant is the hallmark of chronic myeloid leukemia (CML) whereas p190 is frequently associated with B-cell acute lymphoblastic leukemia. The only sequence difference between the two isoforms is the guanidine exchange factor domain. This guanidine exchange factor is reported to activate RHO family GTPases in response to diverse extracellular stimuli. It is not clear whether and, if so, how RHOA contributes to progression of p210 CML. Here we show that knockout of RHOA in the K562 and KU812, p210-expressing cell lines leads to suppression of leukemogenesis in animal models in vivo. RNA-sequencing analysis of the mock control and null cells demonstrated a distinct change in the gene expression profile as a result of RHOA deletion, with significant downregulation of genes involved in cell activation and cell adhesion. Cellular analysis revealed that RHOA knockout leads to impaired cell adhesion and migration and, most importantly, the homing ability of leukemia cells to the bone marrow, which may be responsible for the attenuated leukemia progression. We also identified IGFBP2 as an important downstream target of RHOA. Further mechanistic investigation showed that RHOA activation leads to relocation of the serum response factor (SRF) into the nucleus, where it directly activates IGFBP2. Knockout of IGFBP2 in CML cells suppressed cell adhesion/invasion, as well as leukemogenesis in vivo. This elevated IGFBP2 expression was confirmed in primary CML samples. Thus, we demonstrate one mechanism whereby the RHOA-SRF-IGFBP2 signaling axis contributes to the development of leukemia in cells expressing the p210 BCR-ABL1 fusion kinase.

METTL3 mediates chemoresistance by enhancing AML homing and engraftment via ITGA4

Chemoresistant leukemia relapse is one of the most common causes of death for acute myeloid leukemia (AML) patients and the homing/engraftment in bone marrow (BM) are crucial steps for AML cells to acquire chemoresistance by interacting with stromal cell components. No crosstalk between m⁶A modification and homing/engraftment has been reported. Here, we performed comprehensive high-throughput analyses, including RNA sequencing of CR (complete remission) and relapsed AML patients, and reverse-phase protein arrays of chemoresistant cells to identify METTL3 as a key player regulating AML chemoresistance. Then, METTL3-mediated m⁶A modification was proved to induce the chemoresistance in vitro and in vivo. Furthermore, AML homing/engraftment was discovered being enhanced by upregulated-METTL3 in chemoresistant cells. And the homing/engraftment and drug-resistance associated phenotypes of chemoresistant cells could be reversed by a METTL3 inhibitor. Mechanistically, METTL3 extended the half-life of ITGA4 mRNA by m⁶A methylation, and then, increased expression of ITGA4 protein to enhance homing/engraftment of AML cells. The results provide insights into the function of m⁶A modification on the interaction between AML cells and BM niches and clarify the relationship between METTL3 and AML homing/engraftment, suggesting a therapeutic strategy for the treatment of refractory/relapsed AML with METTL3 inhibitors.

Targeting the HIF-1α-IGFBP2 axis therapeutically reduces IGF1-AKT signaling and blocks the growth and metastasis of relapsed anaplastic Wilms tumor

For patients with anaplastic Wilms tumor (WiT), metastasis and recurrence are common, and prognosis is generally poor. Novel therapies are needed to improve outcomes for patients with this high-risk WiT. A potential contributor to WiT development is constitutive activation of AKT by insulin-like growth factor 1 (IGF1) and its receptor (IGF1R) signaling pathway, but the complete underlying mechanism remains unclear. Here, we demonstrate that the hypoxia-inducible factor 1α (HIF-1α)-IGF binding protein 2 (IGFBP2) axis and the tumor-specific IGF1A are key players for constitutive activation of IGF1-AKT signaling leading to the tumor malignancy. HIF-1α and IGFBP2 are highly expressed in a majority of WiT patient samples. Deficiency of either HIF-1α or IGFBP2 or IGF1 in the tumor cells significantly impairs tumor growth and nearly abrogates metastasis in xenografted mice. Pharmacologic targeting of HIF-1α by echinomycin delivered via nanoliposomes can efficiently restrain growth and metastasis of patient-derived relapsed anaplastic WiT xenografts. Liposomal echinomycin is more potent and effective in inhibiting WiT growth than vincristine in an anaplastic WiT mouse model, and eliminates metastasis by suppressing HIF-1α targets and the HIF-1α-IGFBP2 axis, which governs IGF1-AKT signaling.

Gene expression signature that predicts early molecular response failure in chronic-phase CML patients on frontline imatinib

In chronic-phase chronic myeloid leukemia (CP-CML) patients treated with frontline imatinib, failure to achieve early molecular response (EMR; EMR failure: BCR-ABL1 >10% on the international scale at 3 months) is predictive of inferior outcomes. Identifying patients at high-risk of EMR failure at diagnosis provides an opportunity to intensify frontline therapy and potentially avoid EMR failure. We studied blood samples from 96 CP-CML patients at diagnosis and identified 365 genes that were aberrantly expressed in 13 patients who subsequently failed to achieve EMR, with a gene signature significantly enriched for stem cell phenotype (eg, Myc, β-catenin, Hoxa9/Meis1), cell cycle, and reduced immune response pathways. We selected a 17-gene panel to predict EMR failure and validated this signature on an independent patient cohort. Patients classified as high risk with our gene expression signature (HR-GES) exhibited significantly higher rates of EMR failure compared with low-risk (LR-GES) patients (78% vs 5%; P < .0001), with an overall accuracy of 93%. Furthermore, HR-GES patients who received frontline nilotinib had a relatively low rate of EMR failure (10%). However, HR-GES patients still had inferior deep molecular response achievement rate by 24 months compared with LR-GES patients. This novel multigene signature may be useful for selecting patients at high risk of EMR failure on standard therapy who may benefit from trials of more potent kinase inhibitors or other experimental approaches.

IGFBP-2 acts as a tumour suppressor and plays a role in determining chemosensitivity in bladder cancer cells

There are mixed reports on the role that IGFBP-2 plays in cancer progression, with some indicating a tumour suppressive role and others showing that IGFBP-2 may act as an oncogene. These apparent contradictions may be context and tissue specific. In this study we determined the role that IGFBP-2 played on the phenotype and chemosensitivity of a selection of bladder cancer cell lines and investigated how the abundance of IGFBP-2 was regulated. We found that IGFBP-2 was more abundant in the epithelial bladder cancer cells, RT4 and UMUC3 and absent in the more mesenchymal T24 and TCCSUP cells. Silencing IGFBP-2 using siRNA in epithelial RT4 cells promoted cell proliferation, invasion, colony formation, resulted in a reduction in epithelial (E-cadherin) and an increase in mesenchymal (N-cadherin) markers and increased sensitivity to cisplatin-induced cell death. Conversely, we observed the opposite effects when adding exogenous IGFBP-2 to the mesenchymal T24 cells. We determined that IGFBP-2 was epigenetically silenced via DNA methylation as the cells adopted a mesenchymal phenotype. Collectively these data suggest that IGFBP-2 acts as a tumour suppressor and marker of chemosensitivity in epithelial bladder cancer cells and that IGFBP-2 is epigenetically silenced by methylation to promote bladder cancer progression.

IGFBP2 promotes vasculogenic mimicry formation via regulating CD144 and MMP2 expression in glioma

Vasculogenic mimicry (VM) refers to the fluid-conducting channels formed by aggressive tumor cells rather than endothelial cells (EC) with elevated expression of genes associated with vascularization. VM has been considered as one of the reasons that glioblastoma becomes resistant to anti-VEGF therapy. However, the molecular basis underlying VM formation remains unclear. Here we report that the insulin-like growth factor-binding protein 2 (IGFBP2) acts as a potent factor to enhance VM formation in glioma. Evidence showed that elevated IGFBP2 expression was positively related with VM formation in patients with glioma. Enforced expression of IGFBP2 increased network formation of glioma cells in vitro by activating CD144 and MMP2 (Matrix Metalloproteinase 2). U251 cells with stable knockdown of IGFBP2 led to decreased VM formation and tumor progression in orthotopic mouse model. Mechanistically, IGFBP2 interacts with integrin α5 and β1 subunits and augments CD144 expression in a FAK/ERK pathway-dependent manner. Luciferase reporter and ChIP assay suggested that IGFBP2 activated the transcription factor SP1, which could bind to CD144 promoter. Thus, IGFBP2 acts as a stimulator of VM formation in glioma cells via enhancing CD144 and MMP2 expression.

CAMKs support development of acute myeloid leukemia

Background

We recently identified the human leukocyte immunoglobulin-like receptor B2 (LILRB2) and its mouse ortholog-paired Ig-like receptor (PirB) as receptors for several angiopoietin-like proteins (Angptls). We also demonstrated that PirB is important for the development of acute myeloid leukemia (AML), but exactly how an inhibitory receptor such as PirB can support cancer development is intriguing.

Results

Here, we showed that the activation of Ca (2+)/calmodulin-dependent protein kinases (CAMKs) is coupled with PirB signaling in AML cells. High expression of CAMKs is associated with a poor overall survival probability in patients with AML. Knockdown of CAMKI or CAMKIV decreased human acute leukemia development in vitro and in vivo. Mouse AML cells that are defective in PirB signaling had decreased activation of CAMKs, and the forced expression of CAMK partially rescued the PirB-defective phenotype in the MLL-AF9 AML mouse model. The inhibition of CAMK kinase activity or deletion of CAMKIV significantly slowed AML development and decreased the AML stem cell activity. We also found that CAMKIV acts through the phosphorylation of one of its well-known target (CREB) in AML cells.

Conclusion

CAMKs are essential for the growth of human and mouse AML. The inhibition of CAMK signaling may become an effective strategy for treating leukemia.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0574-8) contains supplementary material, which is available to authorized users.

Novel Gene and Network Associations Found for Acute Lymphoblastic Leukemia Using Case-Control and Family-Based Studies in Multiethnic Populations

Background: Acute lymphoblastic leukemia (ALL) is the most common childhood cancer, suggesting that germline variants influence ALL risk. Although multiple genome-wide association (GWA) studies have identified variants predisposing children to ALL, it remains unclear whether genetic heterogeneity affects ALL susceptibility and how interactions within and among genes containing ALL-associated variants influence ALL risk.Methods: Here, we jointly analyzed two published datasets of case-control GWA summary statistics along with germline data from ALL case-parent trios. We used the gene-level association method PEGASUS to identify genes with multiple variants associated with ALL. We then used PEGASUS gene scores as input to the network analysis algorithm HotNet2 to characterize the genomic architecture of ALL.Results: Using PEGASUS, we confirmed associations previously observed at genes such as ARID5B, IKZF1, CDKN2A/2B, and PIP4K2A, and we identified novel candidate gene associations. Using HotNet2, we uncovered significant gene subnetworks that may underlie inherited ALL risk: a subnetwork involved in B-cell differentiation containing the ALL-associated gene CEBPE, and a subnetwork of homeobox genes, including MEIS1Conclusions: Gene and network analysis uncovered loci associated with ALL that are missed by GWA studies, such as MEIS1 Furthermore, ALL-associated loci do not appear to interact directly with each other to influence ALL risk, and instead appear to influence leukemogenesis through multiple, complex pathways.Impact: We present a new pipeline for post hoc analysis of association studies that yields new insight into the etiology of ALL and can be applied in future studies to shed light on the genomic underpinnings of cancer. Cancer Epidemiol Biomarkers Prev; 26(10); 1531-9. ©2017 AACR.

Sorting protein VPS33B regulates exosomal autocrine signaling to mediate hematopoiesis and leukemogenesis

Certain secretory proteins are known to be critical for maintaining the stemness of stem cells through autocrine signaling. However, the processes underlying the biogenesis, maturation, and secretion of these proteins remain largely unknown. Here we demonstrate that many secretory proteins produced by hematopoietic stem cells (HSCs) undergo exosomal maturation and release that is controlled by vacuolar protein sorting protein 33b (VPS33B). Deletion of VPS33B in either mouse or human HSCs resulted in impaired exosome maturation and secretion as well as loss of stemness. Additionally, VPS33B deficiency led to a dramatic delay in leukemogenesis. Exosomes purified from either conditioned medium or human plasma could partially rescue the defects of HSCs and leukemia-initiating cells (LICs). VPS33B co-existed in exosomes with GDI2, VPS16B, FLOT1, and other known exosome markers. Mechanistically, VPS33B interacted with the GDI2/RAB11A/RAB27A pathway to regulate the trafficking of secretory proteins as exosomes. These findings reveal an essential role for VPS33B in exosome pathways in HSCs and LICs. Moreover, they shed light on the understanding of vesicle trafficking in other stem cells and on the development of improved strategies for cancer treatment.

IGFBP2 modulates the chemoresistant phenotype in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) patients commonly present with advanced stage disease and demonstrate resistance to therapy, with response rates below 40%. Understanding the molecular mechanisms of resistance is crucial for improvement of clinical outcomes. IGFBP2 is a member of the IGFBP family of proteins that has been reported to modulate both IGF and integrin signaling and is a mediator of cell growth, invasion and resistance in other tumor types. In this study, high IGFBP2 expression was observed in a subset of primary EACs and was found to be significantly higher in patients with shorter disease-free intervals as well as in treatment-resistant EACs as compared to chemonaive EACs. Modulation of IGFBP2 expression in EAC cell lines promoted cell proliferation, migration and invasion, implicating a role in the metastatic potential of these cells. Additionally, knockdown of IGFBP2 sensitized EAC cells to cisplatin in a serum-dependent manner. Further in vitro exploration into this chemosensitization implicated both the AKT and ERK pathways. Silencing of IGFBP2 enhanced IGF1-induced immediate activation of AKT and reduced cisplatin-induced ERK activation. Addition of MEK1/2 (selumetinib or trametinib) or AKT (AKT Inhibitor VIII) inhibitors enhanced siIGFBP2-induced sensitization of EAC cells to cisplatin. These results suggest that targeted inhibition of IGFBP2 alone or together with either the MAPK or PI3K/AKT signaling pathway in IGFBP2-overexpressing EAC tumors may be an effective approach for sensitizing resistant EACs to standard neoadjuvant chemotherapy.

IGF-binding protein 2 is a candidate target of therapeutic potential in cancer

Insulin-like growth factor (IGF)-binding protein 2(IGFBP2), a key member of IGF family, has been reported as a notable oncogene in most human epithelium cancers. Increasing evidences suggested that IGFBP2 might be a candidate target of therapuetic potential by regulating key cancer metastasis and invasion-associated signaling networks, but there is still confusion about the mechanism on how IGFBP2 takes part in these processes. In this review, we summarized the current points of view that IGFBP2 functions in signaling pathways during tumorigenesis and tumor progression and discussed its potential clinical applications as a therapeutic target.

Ex vivo expansion of hematopoietic stem cells

Ex vivo expansion of hematopoietic stem cells (HSCs) would benefit clinical applications in several aspects, to improve patient survival, utilize cord blood stem cells for adult applications, and selectively propagate stem cell populations after genetic manipulation. In this review we summarize and discuss recent advances in the culture systems of mouse and human HSCs, which include stroma/HSC co-culture, continuous perfusion and fed-batch cultures, and those supplemented with extrinsic ligands, membrane transportable transcription factors, complement components, protein modification enzymes, metabolites, or small molecule chemicals. Some of the expansion systems have been tested in clinical trials. The optimal condition for ex vivo expansion of the primitive and functional human HSCs is still under development. An improved understanding of the mechanisms for HSC cell fate determination and the HSC culture characteristics will guide development of new strategies to overcome difficulties. In the future, development of a combination treatment regimen with agents that enhance self-renewal, block differentiation, and improve homing will be critical. Methods to enhance yields and lower cost during collection and processing should be employed. The employment of an efficient system for ex vivo expansion of HSCs will facilitate the further development of novel strategies for cell and gene therapies including genome editing.

ADCY7 supports development of acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common adult acute leukemia. Despite treatment, the majority of the AML patients relapse within 5 years. In silico analysis of several available databases of AML patients showed that the expression of adenylate cyclase 7 (ADCY7) significantly inversely correlates with the overall survival of AML patients. To determine whether ADCY7 supports AML development, we employed an shRNA-encoding lentivirus system to inhibit adcy7 expression in human AML cells including U937, MV4-11, and THP-1 cells. The ADCY7 deficiency resulted in decreased cell growth, elevated apoptosis, and lower c-Myc expression of these leukemia cells. This indicates that G protein-coupled receptor signaling contributes to AML pathogenesis. Our study suggests that inhibition of ADCY7 may be novel strategy for treating leukemia.

TRIB3 enhances cell viability during glucose deprivation in HEK293-derived cells by upregulating IGFBP2, a novel nutrient deficiency survival factor

Glucose deprivation occurs in several human diseases, including infarctions and solid tumors, and leads to cell death. In this article, we investigate the role of the pseudokinase Tribbles homolog 3 (TRIB3) in the cellular stress response to glucose starvation using cell lines derived from HEK293, which is highly glycolytic under standard conditions. Our results show that TRIB3 mRNA and protein levels are strongly upregulated in glucose-deprived cells via the induction of activating transcription factor 4 (ATF4) by the endoplasmic reticulum (ER) stress sensor kinase PERK. Cell survival in glucose-deficient conditions is enhanced by TRIB3 overexpression and reduced by TRIB3 knockdown. Genome-wide gene expression profiling uncovered approximately 40 glucose deprivation-responsive genes that are affected by TRIB3, including several genes involved in signaling processes and metabolism. Based on transcription factor motif analysis, the majority of TRIB3-downregulated genes are target genes of ATF4, which TRIB3 is known to inhibit. The gene most substantially upregulated by TRIB3 is insulin-like growth factor binding protein 2 (IGFBP2). IGFBP2 mRNA and protein levels are downregulated in cells subjected to glucose deprivation, and reduced IGFBP2 expression aggravates cell death during glucose deficiency, while overexpression of IGFBP2 prolongs cell survival. Moreover, IGFBP2 silencing abrogates the pro-survival effect of TRIB3. Since TRIB3 augments IGFBP2 expression in glucose-starved cells, the data indicate that IGFBP2 contributes to the attenuation of cell death by TRIB3. These results implicate TRIB3 and IGFBP2, both of which are known to be overexpressed in several types of cancers, as pro-survival modulators of cell viability in nutrient-deficient microenvironments.

IGF-IR determines the fates of BCR/ABL leukemia

Background

The tyrosine kinase receptor insulin-like growth factor 1 receptor (IGF-IR) contributes to the initiation and progression of many types of malignancies. We previously showed that IGF-2, which binds IGF-IR, is an extrinsic factor that supports the ex vivo expansion of hematopoietic stem cells (HSCs). We also demonstrated that IGF-IR is not required for HSC activity in vivo.

Methods and results

Here we investigated the role of IGF-IR in chronic myeloid leukemia (CML) using the retroviral BCR/ABL transplantation mouse model. Existing antibodies against IGF-IR are not suitable for flow cytometry; therefore, we generated a fusion of the human IgG Fc fragment with mutant IGF-2 that can bind to IGF-IR. We used this fusion protein to evaluate mouse primary hematopoietic populations. Through transplantation assays with IGF-IR⁺ and IGF-IR⁻ cells, we demonstrated that IGF-IR is expressed on all mouse HSCs. The expression of IGF-IR is much higher on CML cells than on acute lymphoblastic leukemia (ALL) cells. The depletion of IGF-IR expression in BCR/ABL⁺ cells led to the development of ALL (mostly T cell ALL) but not CML. Lack of IGF-IR resulted in decreased self-renewal of the BCR/ABL⁺ CML cells in the serial replating assay.

Conclusion

IGF-IR regulates the cell fate determination of BCR/ABL⁺ leukemia cells and supports the self-renewal of CML cells.

A HIF-1 network reveals characteristics of epithelial-mesenchymal transition in acute promyelocytic leukemia

Background

Acute promyelocytic leukemia (APL) is a sub-type of acute myeloid leukemia (AML) characterized by a block of myeloid differentiation at the promyelocytic stage and the predominant t(15:17) chromosomal translocation. We have previously determined that cells from APL patients show increased expression of genes regulated by hypoxia-inducible transcription factors (HIFs) compared to normal promyelocytes. HIFs regulate crucial aspects of solid tumor progression and are currently being implicated in leukemogenesis.

Methods

To investigate the contribution of hypoxia-related signaling in APL compared to other AML sub-types, we reverse engineered a transcriptional network from gene expression profiles of AML patients’ samples, starting from a list of direct target genes of HIF-1. A HIF-1-dependent subnetwork of genes specifically dysregulated in APL was derived from the comparison between APL and other AMLs.

Results

Interestingly, this subnetwork shows a unique involvement of genes related to extracellular matrix interaction and cell migration, with decreased expression of genes involved in cell adhesion and increased expression of genes implicated in motility and invasion, thus unveiling the presence of characteristics of epithelial-mesenchymal transition (EMT). We observed that the genes of this subnetwork, whose dysregulation shows a peculiar pattern across different AML sub-types, distinguish malignant from normal promyelocytes, thus ruling out dependence on a myeloid developmental stage. Also, expression of these genes is reversed upon treatment of APL-derived NB4 cells with all-trans retinoic acid and cell differentiation.

Conclusions

Our data suggest that pathways related to EMT-like processes can be implicated also in hematological malignancies besides solid tumors, and can identify specific AML sub-types.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-014-0084-4) contains supplementary material, which is available to authorized users.

(Lymph)angiogenic influences on hematopoietic cells in acute myeloid leukemia

The purpose of this review is to provide an overview of the effect of (lymph)angiogenic cytokines on hematopoietic cells involved in acute myeloid leukemia (AML). Like angiogenesis, lymphangiogenesis occurs in pathophysiological conditions but not in healthy adults. AML is closely associated with the vasculature system, and the interplay between lymphangiogenic cytokines maintains leukemic blast survival in the bone marrow (BM). Once AML is induced, proangiogenic cytokines function as angiogenic or lymphangiogenic factors and affect hematopoietic cells, including BM-derived immune cells. Simultaneously, the representative cytokines, VEGFs and their receptors are expressed on AML blasts in vascular and osteoblast niches in both the BM and the peripheral circulation. After exposure to (lymph)angiogenic cytokines in leukemogenesis and infiltration, immune cell phenotypes and functions are affected. These dynamic behaviors in the BM reflect the clinical features of AML. In this review, we note the importance of lymphangiogenic factors and their receptors in hematopoietic cells in AML. Understanding the functional characterization of (lymph)angiogenic factors in the BM niche in AML will also be helpful in interrupting the engraftment of leukemic stem cells and for enhancing immune cell function by modulating the tumor microenvironment.