Evi1 defines leukemia-initiating capacity and tyrosine kinase inhibitor resistance in chronic myeloid leukemia

Outcome of 3q26.2/MECOM rearrangements in chronic myeloid leukemia

STUDY AIMS

To evaluate the outcomes of patients with 3q26.2/MECOM-rearranged chronic myeloid leukemia (CML).

METHODS

We reviewed consecutive adult patients with 3q26.2/MECOM-rearranged CML between January 1, 1998 and February 16, 2023. Rearrangements of 3q26.2/MECOM were confirmed by conventional cytogenetics, and fluorescence in situ hybridization starting in 2015.

RESULTS

We identified 55 patients with MECOM-rearranged CML, including 23 in chronic phase (CP) or accelerated phase (AP) and 32 in blast phase (BP). Nine patients (16%) achieved a major cytogenetic response (MCyR) or deeper. At a median follow-up of 89 months, median survival was 14 months. The 5-year survival rate was 19% overall, 23% in CML-CP/AP, and 15% in CML-BP. In the 6-month landmark analysis, the 5-year survival rate was 41% for allogeneic stem cell transplantation (allo-SCT) recipients versus 17% for non-recipients (P = 0.050). Multivariate analysis showed that the percentage of marrow blasts and achievement of MCyR or deeper could predict survival.

CONCLUSION

Outcomes of 3q26.2/MECOM-rearranged CML are poor despite the availability of multiple BCR::ABL1 tyrosine kinase inhibitors (TKIs). Third-generation TKIs in combination with novel agents and possible allo-SCT could be considered given the poor outcomes and resistance to second-generation TKIs.

EVI1-mediated Programming of Normal and Malignant Hematopoiesis

Ecotropic viral integration site 1 (EVI1), encoded at the MECOM locus, is an oncogenic zinc finger transcription factor with diverse roles in normal and malignant cells, most extensively studied in the context of hematopoiesis. EVI1 interacts with other transcription factors in a context-dependent manner and regulates transcription and chromatin remodeling, thereby influencing the proliferation, differentiation, and survival of cells. Interestingly, it can act both as a transcriptional activator as well as a transcriptional repressor. EVI1 is expressed, and fulfills important functions, during the development of different tissues, including the nervous system and hematopoiesis, demonstrating a rigid spatial and temporal expression pattern. However, EVI1 is regularly overexpressed in a variety of cancer entities, including epithelial cancers such as ovarian and pancreatic cancer, as well as in hematologic malignancies like myeloid leukemias. Importantly, EVI1 overexpression is generally associated with a very poor clinical outcome and therapy-resistance. Thus, EVI1 is an interesting candidate to study to improve the prognosis and treatment of high-risk patients with "EVI1high" hematopoietic malignancies.

EVI1 upregulates PTGS1 (COX1) and decreases the action of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia cells

Tyrosine kinase inhibitors (TKIs) are highly effective in treating chronic myelogenous leukemia (CML). However, primary and acquired drug resistance to TKIs have been reported. In this study, we used RNA sequencing followed by RQ-PCR to show that the proto-oncogene EVI1 targets the drug-metabolizing gene PTGS1 in CML. The PTGS1 promoter element had an EVI1 binding site, and CHIP assay confirmed its presence. Data from a publicly available CML microarray dataset and an independent set of CML samples showed a significant positive correlation between EVI1 and PTGS1 expression in CML. Downregulation of EVI1 in K562 cells and subsequent treatment with TKIs resulted in a lower IC₅₀ in the control cells. Furthermore, combined inhibition of BCR-ABL with imatinib and PTGS1 with FR122047 (PTGS1 inhibitor) synergistically reduced the viability of imatinib-resistant K562 cells. We conclude that elevated EVI1 expression contributes to TKIs resistance and that combined inhibition of PTGS1 and BCR-ABL may represent a novel therapeutic approach.

CAMK2G is identified as a novel therapeutic target for myelofibrosis

Although JAK1/2 inhibition is effective into alleviating symptoms of myelofibrosis (MF), it does not result in the eradication of MF clones, which can lead to inhibitor-resistant clones emerging during the treatment. Here we established iPS cells derived from MF patient samples (MF-iPSCs) harboring JAK2 V617F, CALR type 1, or CALR type 2 mutations. We demonstrated that these cells faithfully recapitulate the drug sensitivity of the disease. These cells were utilized for chemical screening and calcium/calmodulin-dependent protein kinase 2 (CAMK2) was identified as a promising therapeutic target. MF model cells and mice induced by MPL W515L, another type of mutations recurrently detected in MF patients were used to elucidate the therapeutic potential of CAMK2 inhibition. CAMK2 inhibition was effective against JAK2 inhibitor-sensitive and JAK2 inhibitor-resistant cells. Further research revealed CAMK2 gamma subtype was important in MF model cells induced by MPL W515L. We showed that CAMK2G hetero knockout in the primary bone marrow cells expressing MPL W515Ldecreased colony-forming capacity. CAMK2G inhibition with berbamine, a CAMK2G inhibitor, significantly prolonged survival and reduced disease phenotypes such as splenomegaly and leukocytosis in a MF mouse model induced by MPL W515L. We investigated the molecular mechanisms underlying the therapeutic effect of CAMK2G inhibition and found that CAMK2G is activated by MPL signaling in MF model cells and is an effector in the MPL-JAK2 signaling pathway in these cells. These results indicate CAMK2G plays an important role in MF, and CAMK2G inhibition may be a novel therapeutic strategy that overcomes resistance to JAK1/2 inhibition.

A single-cell atlas of the healthy breast tissues reveals clinically relevant clusters of breast epithelial cells

Single-cell RNA sequencing (scRNA-seq) is an evolving technology used to elucidate the cellular architecture of adult organs. Previous scRNA-seq on breast tissue utilized reduction mammoplasty samples, which are often histologically abnormal. We report a rapid tissue collection/processing protocol to perform scRNA-seq of breast biopsies of healthy women and identify 23 breast epithelial cell clusters. Putative cell-of-origin signatures derived from these clusters are applied to analyze transcriptomes of ~3,000 breast cancers. Gene signatures derived from mature luminal cell clusters are enriched in ~68% of breast cancers, whereas a signature from a luminal progenitor cluster is enriched in ~20% of breast cancers. Overexpression of luminal progenitor cluster-derived signatures in HER2+, but not in other subtypes, is associated with unfavorable outcome. We identify TBX3 and PDK4 as genes co-expressed with estrogen receptor (ER) in the normal breasts, and their expression analyses in >550 breast cancers enable prognostically relevant subclassification of ER+ breast cancers.

BCR-ABL1 positive AML or CML in blast crisis? A pediatric case report with inv(3) and t(9;22) in the initial clone

The co-occurrence of an inversion inv(3)(q21q26)/GATA2-MECOM and a Philadelphia translocation t(9;22)(q34;q11)/BCR-ABL1 in the context of chronic myeloid leukemia (CML) in blast crisis or acute myeloid leukemia (AML) has only rarely been described. To our knowledge, this co-occurrence has been reported in six pediatric patients with CML but not in pediatric patients with AML. Here, we report on a 7-year-old girl, who, presented with a t(9;22) and inv(3) in 14 of 15 metaphases and an additional monosomy 7 was detected in 5 of these metaphases (ISCN: 46,​XX,​inv(3)(q21q26),​t(9;22)(q34q11)[9]/45,​idem,​-7[5]/46,​XX[1]). The p190 BCR-ABL1 fusion transcript was detected by multiplex PCR and targeted RNA sequencing. Due to these results, a clear distinction between a CML in blast crisis and a BCR-ABL1 positive AML was not possible. The patient was treated according to the treatment recommendations of the AML-BFM study group and additionally received tyrosine kinase inhibitor therapy (Dasatinib). The treatment with Dasatinib was successful in eliminating the inv(3)/t(9;22) clone, but the ancestral inv(3) clone persisted. Based upon these findings we diagnosed an AML with inv(3) and a secondary acquisition of t(9;22). This treatment as well as an allogenic transplantation has led to a complete remission of the disease up to this date (21 months post diagnosis).

EVI1 in Leukemia and Solid Tumors

Simple Summary

Ecotropic viral integration site 1 (EVI1) is transcriptionally activated in a subset of myeloid leukemias. Since its discovery, other isoforms of EVI1 have been identified. It has been shown that EVI1 and its isoforms mainly function as transcription factors and to play important roles not only in leukemia but also in a variety of solid tumors. To provide a comprehensive understanding of this family of proteins, we summarize the currently available knowledge of expression and function of EVI1 and its isoforms in leukemia and solid tumors and provide insights of future studies.

Abstract

The EVI1 gene encodes for a transcription factor with two zinc finger domains and is transcriptionally activated in a subset of myeloid leukemias. In leukemia, the transcriptional activation of EVI1 usually results from chromosomal rearrangements. Besides leukemia, EVI1 has also been linked to solid tumors including breast cancer, lung cancer, ovarian cancer and colon cancer. The MDS1/EVI1 gene is encoded by the same locus as EVI1. While EVI1 functions as a transcription repressor, MDS1/EVI1 acts as a transcription activator. The fusion protein encoded by the AML1/MDS1/EVI1 chimeric gene, resulting from chromosomal translocations in a subset of chronic myeloid leukemia, exhibits a similar function to EVI1. EVI1 has been shown to regulate cell proliferation, differentiation and apoptosis, whereas the functions of MDS1/EVI1 and AML1/MDS1/EVI1 remain elusive. In this review, we summarize the genetic structures, biochemical properties and biological functions of these proteins in cancer.

EVI1 induces autophagy to promote drug resistance via regulation of ATG7 expression in leukemia cells

Ecotropic viral integration site 1 (EVI1) is an oncogenic transcription factor, which is abnormally expressed in myeloid leukemia and other several solid cancers. It is associated with short survival as well as anticancer drug resistance. Autophagy is a protective mechanism that promotes cancer cell growth and survival under stressed conditions including clinical drug treatment. Here evidences are provided that EVI1 induces autophagy and mediated drug resistance in myeloid leukemia cells. Both knockdown using RNAi and pharmacological inhibition of autophagy significantly increase sensitivity to cytotoxic drug treatment in EVI1high cells. Mechanistic studies revealed that EVI1 regulated autophagy by directly binding to autophagy-related gene autophagy related 7 (ATG7) promoter and transcriptionally upregulating its expression. Notably, ATG7 expression was positively correlated with EVI1 in bone marrow mononuclear cells from myeloid leukemia patients. Acute myeloid leukemia patients with high level of EVI1 are associated with unfavorable overall survival, which was aggravated by simultaneous high expression of ATG7 in these patients. Furthermore, ChIP and firefly luciferase reporter assay identified an EVI1-binding site at 227 upstream promoter region of ATG7 which regulated its transcription. In addition, enforced expression of EVI1 also increased intracellular reactive oxygen species and ATG7 mRNA levels as well as autophagy activity, whereas the increase was attenuated after treatment with reactive oxygen species scavenger, suggesting the involvement of reactive oxygen species in EVI1-induced autophagy. These findings demonstrate that EVI protects myeloid leukemia cell from anticancer drug treatment by inducing autophagy through dual control of ATG7. These results might present a new therapeutic approach for improving treatment outcome in myelogenous leukemia with EVI1high.

EVI1 as a Marker for Lymph Node Metastasis in HNSCC

BACKGROUND

HNSCC is the sixth most common cancer in humans and has still a very poor prognosis. The treatment methods so far are very often associated with mutilation and impairment in the quality of life. Except for p16 expression, there are no reliable prognostic markers in HNSCC so far. Ecotropic Viral Integration Site 1 (EVI1) is a well-described prognostic marker in leukemia and different types of solid cancers. In these, a high EVI1 expression is associated with a poor prognosis. In HNSCC, it is not known so far if EVI1 has any prognostic relevance.

MATERIALS AND METHODS

We used our representative tissue cohort of 389 primary HNSCCs, of which 57.2% had one or more lymph node metastases. Here EVI1 expression was analyzed via immunohistochemistry and correlated with the clinical characteristics of these patients.

RESULTS

Although in HNSCC EVI1 expression does not predict poor survival, a high EVI1 expression in the primary tumor correlates with a lymph node metastatic disease.

CONCLUSION

Consequently, EVI1 may serve as a biomarker to predict an occult lymph node metastasis in a clinical nodal negative (cN0) HNSCC.

All-trans retinoic acid enhances, and a pan-RAR antagonist counteracts, the stem cell promoting activity of EVI1 in acute myeloid leukemia

Ecotropic virus integration site 1 (EVI1), whose overexpression characterizes a particularly aggressive subtype of acute myeloid leukemia (AML), enhanced anti-leukemic activities of all-trans retinoic acid (atRA) in cell lines and patient samples. However, the drivers of leukemia formation, therapy resistance, and relapse are leukemic stem cells (LSCs), whose properties were hardly reflected in these experimental setups. The present study was designed to address the effects of, and interactions between, EVI1 and retinoids in AML LSCs. We report that Evi1 reduced the maturation of leukemic cells and promoted the abundance, quiescence, and activity of LSCs in an MLL-AF9-driven mouse model of AML. atRA further augmented these effects in an Evi1 dependent manner. EVI1 also strongly enhanced atRA regulated gene transcription in LSC enriched cells. One of their jointly regulated targets, Notch4, was an important mediator of their effects on leukemic stemness. In vitro exposure of leukemic cells to a pan-RAR antagonist caused effects opposite to those of atRA. In vivo antagonist treatment delayed leukemogenesis and reduced LSC abundance, quiescence, and activity in Evi1^high AML. Key results were confirmed in human myeloid cell lines retaining some stem cell characteristics as well as in primary human AML samples. In summary, our study is the first to report the importance of EVI1 for key properties of AML LSCs. Furthermore, it shows that atRA enhances, and a pan-RAR antagonist counteracts, the effects of EVI1 on AML stemness, thus raising the possibility of using RAR antagonists in the therapy of EVI1^high AML.

Myeloid leukemia with high EVI1 expression is sensitive to 5-aza-2'-deoxycytidine by targeting miR-9

PURPOSE

High expression of ecotropic viral integration site 1 (EVI1) has been associated with a poor prognosis in leukemia patients, but the underlying mechanism remains unclear. Aberrant expression of microRNAs plays critical roles in leukemia development. MiR-9 is a putative potential target of EVI1. We have investigated the regulating mechanism of miR-9 by EVI1 in leukemia cells.

METHODS

We first examined the relationship between miR-9 and EVI1 expression levels in nine leukemia cell lines by RT-PCR. Then we forced high expression of EVI1 in UoCM1 and K562 cells to confirm the downregulation of miR-9 by EVI1. Methylation of the miR-9 promoter region was detected by DNA bisulfite sequencing. We treated the EVI1-overexpressing cells with the hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA) to reverse EVI1-induced hypermethylation of miR-9.

RESULTS

EVI1 and miR-9 expression was negative related. Forced expression of EVI1 downregulated miR-9 by inducing hypermethylation of the miR-9 promoter. 5-AZA reversed high EVI1-induced hypermethylation of the miR-9 promoter and restored the expression of miR-9. 5-AZA induced extensive apoptosis and inhibited proliferation through cell cycle arrest in EVI1-overexpressing leukemia cells.

CONCLUSIONS

Our results suggest that EVI1 may be involved in leukemia cell proliferation and apoptosis via the regulation of miR-9 promoter methylation. 5-AZA may represent a promising therapeutic option for EVI1-high leukemia patients.

Chronic myelogenous leukemia, a still unsolved problem: pitfalls and new therapeutic possibilities

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of hematopoietic stem cells. At the molecular level, the disorder results from t(9;22)(q34;q11) reciprocal translocation between chromosomes, which leads to the formation of an oncogenic BCR–ABL gene fusion. Instead of progress in the understanding of the molecular etiology of CML and the development of novel therapeutic strategies, clinicians still face many challenges in the effective treatment of patients. In this review, we discuss the pathways of diagnosis and treatment of patients, as well as the problems appearing in the course of disease development. We also briefly refer to several aspects regarding the current knowledge on the molecular basis of CML and new potential therapeutic targets.

EVI1 promotes epithelial-to-mesenchymal transition, cancer stem cell features and chemo-/radioresistance in nasopharyngeal carcinoma

BACKGROUND

Aberrant EVI1 expression is frequently reported in cancer studies; however, its role in nasopharyngeal carcinoma (NPC) has not been examined in detail. The aim of the present study is to investigate the involvement of EVI1 in progression and prognosis of NPC.

METHODS

RT-PCR, immunohistochemistry and western blot assays were used to examine the expression of EVI1 in NPC tissues and cell lines. Fluorescence in situ hybridization assay was used to examine the amplification of EVI1 in NPC tissues. The biological effect of EVI1 was determined by both in vitro and in vivo studies. The dual-luciferase reporter assay was performed to confirm that EVI1 bind at E-cadherin andβ-catenin promoters. The ChIP, EMSA, and coimmunoprecipitation combined with mass spectrometry assays were used to analyze the EVI1 regulated proteins.

RESULTS

EVI1 expression level was up-regulated in NPC tissues and cell lines. EVI1 was amplificated in NPC tissues. We observed that EVI1 down-regulation decreased the cell proliferation and invasive capacity of NPC cells in vitro and in vivo. EVI1, snail, and HDAC1 formed a co-repressor complex to repress E-cadherin expression and ultimately contributed to epithelial mesenchymal transition (EMT) phenotype in NPC cells. In another way, EVI1 directly bound at β-catenin promoter and activated its expression. β-catenin mediated EVI1's function on cancer stem cells (CSCs) properties. EVI1 up-regulation predicted unfavorable prognosis and contributed to chemo/radio-resistance in NPC cells. Finally, we constructed arsenic trioxide-loaded nanoparticles (ALNPs) and revealed that ALNPs exerted anti-tumor effect in NPC cells.

CONCLUSIONS

Our data indicated that EVI1 played an oncogenic role in NPC growth and metastasis and that EVI1 might serve as a novel molecular target for the treatment of NPC.

A modified DAW-22 compound F-B1 inhibits Bcr/Abl and induces apoptosis in chronic myelogenous leukemia cells

The Bcr/Abl kinase is an oncogenic fusion protein that plays a central role in the pathogenesis of chronic myeloid leukemia (CML). Some small-molecule kinase inhibitors such as imatinib were developed in the treatment of CML; however, resistant to imatinib is an emerging problem of CML therapy. Hence, additional approaches or compounds targeting leukemogenic cells are required. F-B1 is a new compound obtained by modifying DAW-22, a natural sesquiterpenoid coumarin, which was isolated from traditional Chinese medicine Ferula ferulaeoides (Steud.) Korov. F-B1 was found to inhibit the growth of myelogenous leukemia cell lines, that is, K562 cells bearing wild-type Bcr/Abl and imatinib-resistant K562G cells. F-B1 potently down-regulated the mRNA and protein levels of Bcr/Abl, followed by suppression of the downstream molecules such as Akt, externally regulated kinases, and nuclear factor κB. In addition, F-B1 also induced cell apoptosis by impairing the balance between proapoptotic protein Bax and antiapoptotic proteins Bcl-2 and Bcl-XL and increased the activity of mitochondrial-dependent apoptosis in nude mouse xenografts. Experimental validation results together demonstrated that F-B1 can inhibit Bcr/Abl fusion proteins in K562 and K562G cells, implying that F-B1 might be a promising drug to treat CML, especially the imatinib-resistant CML.

Systemic Virus Infections Differentially Modulate Cell Cycle State and Functionality of Long-Term Hematopoietic Stem Cells In Vivo

Quiescent long-term hematopoietic stem cells (LT-HSCs) are efficiently activated by type I interferon (IFN-I). However, this effect remains poorly investigated in the context of IFN-I-inducing virus infections. Here we report that both vesicular stomatitis virus (VSV) and murine cytomegalovirus (MCMV) infection induce LT-HSC activation that substantially differs from the effects triggered upon injection of synthetic IFN-I-inducing agents. In both infections, inflammatory responses had to exceed local thresholds within the bone marrow to confer LT-HSC cell cycle entry, and IFN-I receptor triggering was not critical for this activation. After resolution of acute MCMV infection, LT-HSCs returned to phenotypic quiescence. However, non-acute MCMV infection induced a sustained inflammatory milieu within the bone marrow that was associated with long-lasting impairment of LT-HSC function. In conclusion, our results show that systemic virus infections fundamentally affect LT-HSCs and that also non-acute inflammatory stimuli in bone marrow donors can affect the reconstitution potential of bone marrow transplants.

Identification of novel MECOM gene fusion and personalized therapeutic targets through integrative clinical sequencing in secondary acute myeloid leukemia in a patient with severe congenital neutropenia: a case report and literature review

Severe congenital neutropenia (SCN) is a rare hematologic disorder characterized by defective myelopoiesis and a high incidence of malignant transformation to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). SCN patients who develop MDS/AML have excessive toxicities to traditional chemotherapy, and safer therapies are needed to improve overall survival in this population. In this report, we outline the use of a prospective integrative clinical sequencing trial (PEDS-MIONCOSEQ) in a patient with SCN and AML to help identify oncogenic targets for less toxic agents. Integrative sequencing identified two somatic cis-mutations in the colony stimulating factor 3 receptor (CSF3R) gene, a p.T640N mutation in the transmembrane region and a p.Q768* truncation mutation in the cytoplasmic domain. A somatic mutation p.H105Y, in the runt homology domain (RHD) of runt-related transcription factor 1 (RUNX1), was also identified. In addition, sequencing discovered a unique in-frame EIF4A2-MECOM (MDS1 and ectopic viral integration site 1 complex) chromosomal translocation with high MECOM expression. His mutations in CSF3R served as potential targets for tyrosine kinase inhibition and therefore provided an avenue to avoid more harmful therapy. This study highlights the utility of integrative clinical sequencing in SCN patients who develop leukemia and outlines a strategy on how to approach these patients in a future clinical sequencing trial to improve historically poor outcomes. A thorough review of leukemia in SCN and the role of CSF3R mutations in oncologic therapy are provided to support a new strategy on how to approach MDS/AML in SCN.

ADAM8 Is an Antigen of Tyrosine Kinase Inhibitor-Resistant Chronic Myeloid Leukemia Cells Identified by Patient-Derived Induced Pluripotent Stem Cells

Properties of cancer stem cells involved in drug resistance and relapse have significant effects on clinical outcome. Although tyrosine kinase inhibitors (TKIs) have dramatically improved survival of patients with chronic myeloid leukemia (CML), TKIs have not fully cured CML due to TKI-resistant CML stem cells. Moreover, relapse after discontinuation of TKIs has not been predicted in CML patients with the best TKI response. In our study, a model of CML stem cells derived from CML induced pluripotent stem cells identified ADAM8 as an antigen of TKI-resistant CML cells. The inhibition of expression or metalloproteinase activity of ADAM8 restored TKI sensitivity in primary samples. In addition, residual CML cells in patients with optimal TKI response were concentrated in the ADAM8+ population. Our study demonstrates that ADAM8 is a marker of residual CML cells even in patients with optimal TKI response and would be a predictor of relapse and a therapeutic target of TKI-resistant CML cells.

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We established a model of CML stem cells derived from CML-iPSCs

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ADAM8 is identified as an antigen of TKI-resistant CML cells

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The inhibition of ADAM8 restored TKI sensitivity in primary samples

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ADAM8 is a marker of residual CML cells in patients with optimal TKI response

Cellular and Molecular Networks in Chronic Myeloid Leukemia: The Leukemic Stem, Progenitor and Stromal Cell Interplay

The use of imatinib, second and third generation ABL tyrosine kinase inhibitors (TKI) (i.e. dasatinib, nilotinib, bosutinib and ponatinib) made CML a clinically manageable and, in a small percentage of cases, a cured disease. TKI therapy also turned CML blastic transformation into a rare event; however, disease progression still occurs in those patients who are refractory, not compliant with TKI therapy or develop resistance to multiple TKIs. In the past few years, it became clear that the BCRABL1 oncogene does not operate alone to drive disease emergence, maintenance and progression. Indeed, it seems that bone marrow (BM) microenvironment-generated signals and cell autonomous BCRABL1 kinase-independent genetic and epigenetic alterations all contribute to: i. persistence of a quiescent leukemic stem cell (LSC) reservoir, ii. innate or acquired resistance to TKIs, and iii. progression into the fatal blast crisis stage. Herein, we review the intricate leukemic network in which aberrant, but finely tuned, survival, mitogenic and self-renewal signals are generated by leukemic progenitors, stromal cells, immune cells and metabolic microenvironmental conditions (e.g. hypoxia) to promote LSC maintenance and blastic transformation.

Regulation of Hematopoiesis and Hematological Disease by TGF-β Family Signaling Molecules

Throughout the lifetime of an individual, hematopoietic stem cells (HSCs) maintain the homeostasis of normal hematopoiesis through the precise generation of mature blood cells. Numerous genetic studies in mice have shown that stem-cell quiescence is critical for sustaining primitive long-term HSCs in vivo. In this review, we first examine the crucial roles of transforming growth factor β (TGF-β) and related signaling molecules in not only regulating the well-known cytostatic effects of these molecules but also governing the self-renewal capacity of HSCs in their in vivo microenvironmental niche. Second, we discuss the current evidence indicating that TGF-β signaling has a dual function in disorders of the hematopoietic system. In particular, we examine the paradox that, although intrinsic TGF-β signaling is essential for regulating the survival and resistance to therapy of chronic myelogenous leukemia (CML) stem cells, genetic changes that abrogate TGF-β signaling can lead to the development of several hematological malignancies.

Molecular analysis of more than 140 gene fusion variants and aberrant activation of EVI1 and TLX1 in hematological malignancies

Gene fusions are observed in abnormal chromosomal rearrangements such as translocations in hematopoietic malignancies, especially leukemia subtypes. Hence, it is critical to obtain correct information about these rearrangements in order to apply proper treatment techniques. To identify abnormal molecular changes in patients with leukemia, we developed a multiplex reverse transcriptase polymerase chain reaction (MRT-PCR) protocol and investigated more than 140 gene fusions resulting from variations of 29 prevalent chromosomal rearrangements along with EVI1 and TLX1 oncogenic expression in the presence of optimized primers. The potential of the MRT-PCR method was approved by evaluating the available cell lines as positive control and confirmed by sequencing. Samples from 53 patients afflicted with hematopoiesis malignancies were analyzed. Results revealed at least one chromosomal rearrangement in 69% of acute myeloid leukemia subjects, 64% of acute lymphoblastic leukemia subjects, and 81% of chronic myeloid leukemia subjects, as well as a subject with hypereosinophilic syndrome. Also, five novel fusion variants were detected. Results of this study also showed that chromosomal rearrangements, both alone and in conjunction with other rearrangements, are involved in leukemogenesis. Moreover, it was found that EVI1 is a suitable hallmark for hematopoietic malignancies.

Overexpression of ecotropic viral integration site-1 is a prognostic factor of lung squamous cell cancer

AIM

To explore the expression and clinical significance of ecotropic viral integration site-1 (EVI1) of lung squamous cell cancer (SCC).

METHODS

The expression of EVI1 in SCC was detected by immunohistochemistry and the validation cohort was divided into EVI1 high-expression group and low-expression group according to the cutoff of immunohistochemical score. The correlations between EVI1 expression and the clinicopathological factors were analyzed by χ² test. The relation between EVI1 expression and overall survival rate was evaluated by univariate analysis with Kaplan-Meier method. The independent prognostic factor was identified by multivariate analysis with Cox regression model.

RESULTS

In this study, the EVI1 high-expression percentage was 32.32% (53/164). EVI1 high expression was significantly associated with a poorer overall 5-year survival rate of SCC (P=0.021). Moreover, EVI1 high expression was identified as an independent prognostic factor of SCC, predicting the unfavorable prognosis (P=0.013).

CONCLUSION

High expression of EVI1 was significantly associated with a poorer prognosis and it was identified as an independent prognostic factor of SCC.

Ecotropic viral integration site I regulates alpha1, 6-fucosyl transferase expression and blocks erythropoiesis in chronic myeloid leukemia

Although BCR-ABL is the hallmark genetic abnormality of chronic myeloid leukemia (CML), secondary molecular events responsible for the evolution of the disease to blast crisis are yet to be deciphered. Taking into account the significant association of ecotropic viral integration site I (EVI1) in CML drug resistance, it is necessary to decipher the other roles played by EVI1 in CML disease progression. In this regard, we cross-hybridized three microarray datasets and deduced a set of 11 genes that seems to be regulated by EVI1 in CML. We observed a strong correlation between EVI1 and alpha1, 6-fucosyltransferase (FUT8) in the chronic phase of the disease and both of them were found to be up-regulated with the progression of the disease. Knockdown of EVI1 in a CML cell line not only down-regulated FUT8, but also rendered the cells towards erythroid differentiation. Our study shows the involvement of EVI1 and FUT8 axis in blocking erythropoiesis in CML.

Activation of EVI1 transcription by the LEF1/β-catenin complex with p53-alteration in myeloid blast crisis of chronic myeloid leukemia

The presence of a BCR-ABL1 fusion gene is necessary for the pathogenesis of chronic myeloid leukemia (CML) through t(9;22)(q34;q11) translocation. Imatinib, an ABL tyrosine kinase inhibitor, is dramatically effective in CML patients; however, 30% of CML patients will need further treatment due to progression of CML to blast crisis (BC). Aberrant high expression of ecotropic viral integration site 1 (EVI1) is frequently observed in CML during myeloid-BC as a potent driver with a CML stem cell signature; however, the precise molecular mechanism of EVI1 transcriptional regulation during CML progression is poorly defined. Here, we demonstrate the transcriptional activity of EVI1 is dependent on activation of lymphoid enhancer-binding factor 1 (LEF1)/β-catenin complex by BCR-ABL with loss of p53 function during CML-BC. The activation of β-catenin is partly dependent on BCR-ABL expression through enhanced GSK3β phosphorylation, and EVI1 expression is directly enhanced by the LEF1/β-catenin complex bound to the EVI1 promoter region. Moreover, the loss of p53 expression is inversely correlated with high expression of EVI1 in CML leukemia cells with an aggressive phase of CML, and a portion of the activation mechanism of EVI1 expression is dependent on β-catenin activation through GSK3β phosphorylation by loss of p53. Therefore, we found that the EVI1 activation in CML-BC is dependent on LEF1/β-catenin activation by BCR-ABL expression with loss of p53 function, representing a novel selective therapeutic approach targeting myeloid blast crisis progression.

Relationship between gene mutation and lung cancer metastasis

Cancer is a genetic disease occurring through a multi-step process. Many important genes responsible for the genesis of various cancers have been discovered, their mutations precisely identified and the pathways through which they act characterized. One question that remains unanswered is whether the development of new, more specific therapeutic agents is the best way to minimize cancer morbidity and mortality in the long-term. Metastasis is the relentless pursuit of cancer to escape its primary site and colonize distant organs. Phenotypic changes during cancer progression reflect the sequential accumulation of genetic alterations, which endow cancer cells with the ability to undergo their own divergent evolution and create distinct metastatic species. In order to understand this process, it is crucial to identify genes whose alterations accumulate during cancer progression and correlate with metastatic phenotypes of cancer cells.

Cytoprotective autophagy maintains leukemia-initiating cells in murine myeloid leukemia

Autophagy is required for maintenance of AML-initiating cells and peripheral myeloblast survival. Loss of autophagy potentiates the therapeutic effects of AraC in vivo.

Evi1 regulates Notch activation to induce zebrafish hematopoietic stem cell emergence

During development, hematopoietic stem cells (HSCs) emerge from aortic endothelial cells (ECs) through an intermediate stage called hemogenic endothelium by a process known as endothelial-to-hematopoietic transition (EHT). While Notch signaling, including its upstream regulator Vegf, is known to regulate this process, the precise molecular control and temporal specificity of Notch activity remain unclear. Here, we identify the zebrafish transcriptional regulator evi1 as critically required for Notch-mediated EHT In vivo live imaging studies indicate that evi1 suppression impairs EC progression to hematopoietic fate and therefore HSC emergence. evi1 is expressed in ECs and induces these effects cell autonomously by activating Notch via pAKT Global or endothelial-specific induction of notch, vegf, or pAKT can restore endothelial Notch and HSC formations in evi1 morphants. Significantly, evi1 overexpression induces Notch independently of Vegf and rescues HSC numbers in embryos treated with a Vegf inhibitor. In sum, our results unravel evi1-pAKT as a novel molecular pathway that, in conjunction with the shh-vegf axis, is essential for activation of Notch signaling in VDA endothelial cells and their subsequent conversion to HSCs.

Pediatric chronic myeloid leukemia with inv(3)(q21q26.2) and T lymphoblastic transformation: a case report

Background

Chronic myeloid leukemia (CML) comprises ~3 % of pediatric leukemia. Although therapy with tyrosine kinase inhibitors (TKIs) is highly effective for CML, multiple factors have been identified as predictive of treatment failure. Chromosomal abnormalities involving the MECOM locus at 3q26 portend therapy resistant disease in adults, yet have never been described in pediatric patients and have not been associated with T lymphoblastic progression.

Case presentation

We present a case of an 11-year-old boy with CML possessing the unique combination of T lymphoblastic transformation and a subclone harboring inv(3)(q21q26.2) at diagnosis. This is the first reported case of pediatric CML with inv(3)(q21q26.2) and the first case of T lymphoblastic progression associated with this karyotype. The patient was treated with single agent TKI therapy with robust initial response. Marrow histology at one month showed restoration of trilineage hematopoiesis and BCR-ABL RT-PCR at three months showed a 1.4 log reduction in transcript levels.

Conclusions

The karyotypic abnormality of inv(3)(q21q26.2) in CML is not restricted to adult patients. Moreover, while chromosome 3 abnormalities are markers of TKI resistance in adults, our patient showed a robust early response to single agent TKI therapy. This finding suggests pediatric CML with inv(3)(q21q26.2) may have distinct features and more favorable treatment responses than those described in adults.

Isolated Ocular Manifestation of Relapsed Chronic Myelogenous Leukemia Presenting as Myeloid Blast Crisis in a Patient on Imatinib Therapy: A Case Report and Review of the Literature

Blast phase in chronic myelogenous leukemia (CML) has rarely been reported to involve extramedullary sites like skin, lymph nodes, and central nervous system. Clinical history, characteristic hematologic findings (elevated leukocyte counts, myelocytic predominance, and basophilia), and Philadelphia chromosome are of high diagnostic significance especially in isolated extramedullary presentations. We describe a unique case of CML relapse with blast phase involving the eye. A 66-year-old man with a known diagnosis of CML on imatinib and in molecular remission for 3 years presented with a painful blind eye. Histologic examination revealed diffuse involvement of choroid, iris, vitreous humor, and the optic nerve by blast cells. The blasts expressed CD34, aberrant TdT, and a myeloid phenotype (CD13, CD33, and CD117). Fluorescence in situ hybridization (FISH) of vitreous fluid detected BCR-ABL1 gene rearrangement. Additionally, trisomy 8 and gains of 9 and 22 were seen which were not present in the initial diagnostic marrow study 3 years ago. At relapse, the bone marrow, peripheral blood, and the cerebrospinal fluid were not involved by CML. Patient received induction chemotherapy and single dose prophylactic intrathecal methotrexate and was maintained on antityrosine kinase therapy and eventually underwent allogenic stem cell transplantation.

Clinical and prognostic significance of 3q26.2 and other chromosome 3 abnormalities in CML in the era of tyrosine kinase inhibitors

Chromosome 3q26.2 abnormalities in acute myeloid leukemia, including inv(3)/t(3;3) and t(3;21), have been studied and are associated with a poor prognosis. Their prevalence, response to tyrosine kinase inhibitor (TKI) treatment, and prognostic significance in chronic myelogenous leukemia (CML) are largely unknown. In this study, we explored these aspects using a cohort of 2013 patients with CML diagnosed in the era of TKI therapy. Chromosome 3 abnormalities were observed in 116 (5.8%) of 2013 cases. These cases were divided into 5 distinct groups: A, inv(3)(q21q26.2)/t(3;3)(q21;q26.2), 26%; B, t(3;21)(q26.2;q22), 17%; C, other 3q26.2 rearrangements, 7%; D, rearrangements involving chromosome 3 other than 3q26.2 locus, 32%; and E, gain or loss of partial or whole chromosome 3, 18%. In all, 3q26.2 rearrangements were the most common chromosome 3 abnormalities (50%, groups A-C). 3q26.2 rearrangements emerged at different leukemic phases. For cases with 3q26.2 rearrangements that initially emerged in chronic or accelerated phase, they had a high rate of transformation to blast phase. Patients with 3q26.2 abnormalities showed a marginal response to TKI treatment, and no patients achieved a long-term sustainable response at a cytogenetic or molecular level. Compared with other chromosomal abnormalities in CML, patients with 3q26.2 rearrangements had poorer overall survival. The presence or absence of other concurrent chromosomal abnormalities did not affect survival in these patients, reflecting the predominant role of 3q26.2 rearrangements in determining prognosis. Interestingly, although heterogeneous, chromosome 3 abnormalities involving non-3q26.2 loci (groups D, E) also conferred a worse prognosis compared with changes involving other chromosomes in this cohort.

Novel drug candidates for blast phase chronic myeloid leukemia from high-throughput drug sensitivity and resistance testing

Chronic myeloid leukemia in blast crisis (CML BC) remains a challenging disease to treat despite the introduction and advances in tyrosine kinase inhibitor (TKI) therapy. In this study we set out to identify novel candidate drugs for CML BC by using an unbiased high-throughput drug testing platform. We used three CML cell lines representing different types of CML blast phases (K562, EM-2 and MOLM-1) and primary leukemic cells from three CML BC patients. Profiling of drug responses was performed with a drug sensitivity and resistance testing platform comprising 295 anticancer agents. Overall, drug sensitivity scores and the drug response profiles of cell line and primary cell samples correlated well and were distinct from other types of leukemia samples. The cell lines were highly sensitive to TKIs and the clinically TKI-resistant patient samples were also resistant ex vivo. Comparison of cell line and patient sample data identified new candidate drugs for CML BC, such as vascular endothelial growth factor receptor and nicotinamide phosphoribosyltransferase inhibitors. Our results indicate that these drugs in particular warrant further evaluation by analyzing a larger set of primary patient samples. The results also pave way for designing rational combination therapies.

Translational horizons in the tumor microenvironment: harnessing breakthroughs and targeting cures

Chemotherapy and targeted therapy have opened new avenues in clinical oncology. However, there is a lack of response in a substantial percentage of cancer patients and diseases frequently relapse in those who even initially respond. Resistance is, at present, the major barrier to conquering cancer, the most lethal age-related pathology. Identification of mechanisms underlying resistance and development of effective strategies to circumvent treatment pitfalls thereby improving clinical outcomes remain overarching tasks for scientists and clinicians. Growing bodies of data indicate that stromal cells within the genetically stable but metabolically dynamic tumor microenvironment confer acquired resistance against anticancer therapies. Further, treatment itself activates the microenvironment by damaging a large population of benign cells, which can drastically exacerbate disease conditions in a cell nonautonomous manner, and such off-target effects should be well taken into account when establishing future therapeutic rationale. In this review, we highlight relevant biological mechanisms through which the tumor microenvironment drives development of resistance. We discuss some unsolved issues related to the preclinical and clinical trial paradigms that need to be carefully devised, and provide implications for personalized medicine. In the long run, an insightful and accurate understanding of the intricate signaling networks of the tumor microenvironment in pathological settings will guide the design of new clinical interventions particularly combinatorial therapies, and it might help overcome, or at least prevent, the onset of acquired resistance.

Genomic quantitative real-time PCR proves residual disease positivity in more than 30% samples with negative mRNA-based qRT-PCR in Chronic Myeloid Leukemia

Imatinib mesylate (IM) is the first line therapy against Chronic Myeloid Leukemia, effectively prolonging overall survival. Because discontinuation of treatment is associated with relapse, IM is required indefinitely to maintain operational cure. To assess minimal residual disease, cytogenetic analysis is insensitive in a high background of normal lymphocytes. The qRT-PCR provides highly sensitive detection of BCR-ABL1 transcripts, but mRNA levels are not directly related to the number of leukemic cells, and undetectable results are difficult to interpret. We developed a sensitive approach to detect the number of leukemic cells by a genomic DNA (gDNA) Q-PCR assay based on the break-point sequence, with a formula to calculate the number of Ph-positive cells. We monitored 8 CML patients treated with IM for more than 8 years. We tested each samples by patient specific gDNA Q-PCR in parallel by the conventional techniques. In all samples positive for chimeric transcripts we showed corresponding chimeric gDNA by Q-PCR, and in 32.8% (42/128) of samples with undetectable levels of mRNA we detected the persistence of leukemic cells. The gDNA Q-PCR assay could be a new diagnostic tool used in parallel to conventional techniques to support the clinician's decision to vary or to STOP IM therapy.