Id1 transcription inhibitor-matrix metalloproteinase 9 axis enhances invasiveness of the breakpoint cluster region/abelson tyrosine kinase-transformed leukemia cells

Bioinformatics analysis and identification of hub genes and immune-related molecular mechanisms in chronic myeloid leukemia

BACKGROUND

Chronic myeloid leukemia (CML) is a malignant hyperplastic tumor of the bone marrow originating from pluripotent hematopoietic stem cells. The advent of tyrosine kinase inhibitors (TKIs) has greatly improved the survival rate of patients with CML. However, TKI-resistance leads to the disease recurrence and progression. This study aimed to identify immune-related genes (IRGs) associated with CML progression.

METHODS

We extracted the gene's expression profiles from the Gene Expression Omnibus (GEO). Bioinformatics analysis was used to determine the differentially expressed IRGs of CML and normal peripheral blood mononuclear cells (PBMCs). Functional enrichment and gene set enrichment analysis (GSEA) were used to explore its potential mechanism. Hub genes were identified using Molecular Complex Detection (MCODE) and the CytoHubba plugin. The hub genes' diagnostic value was evaluated using the receiver operating characteristic (ROC). The relative proportions of infiltrating immune cells in each CML sample were evaluated using CIBERSORT. Quantitative real-time PCR (RT-qPCR) was used to validate the hub gene expression in clinical samples.

RESULTS

A total of 31 differentially expressed IRGs were identified. GO analyses revealed that the modules were typically enriched in the receptor ligand activity, cytokine activity, and endopeptidase activity. KEGG enrichment analysis of IRGs revealed that CML involved Th17 cell differentiation, the NF-kappa B signaling pathway, and cytokine-cytokine receptor interaction. A total of 10 hub genes were selected using the PPI network. GSEA showed that these hub genes were related to the gamma-interferon immune response, inflammatory response, and allograft rejection. ROC curve analysis suggested that six hub genes may be potential biomarkers for CML diagnosis. Further analysis indicated that immune cells were associated with the pathogenesis of CML. The RT-qPCR results showed that proteinase 3 (PRTN3), cathepsin G (CTSG), matrix metalloproteinase 9 (MMP9), resistin (RETN), eosinophil derived neurotoxin (RNase2), eosinophil cationic protein (ECP, RNase3) were significantly elevated in CML patients' PBMCs compared with healthy controls.

CONCLUSION

These results improved our understanding of the functional characteristics and immune-related molecular mechanisms involved in CML progression and provided potential diagnostic biomarkers and therapeutic targets.

ID1 and ID3 are Negative Regulators of TGFβ2-Induced Ocular Hypertension and Compromised Aqueous Humor Outflow Facility in Mice

Purpose

In POAG, elevated IOP remains the major risk factor in irreversible vision loss. Increased TGFβ2 expression in POAG aqueous humor and in the trabecular meshwork (TM) amplifies extracellular matrix (ECM) deposition and reduces ECM turnover in the TM, leading to a decreased aqueous humor (AH) outflow facility and increased IOP. Inhibitor of DNA binding proteins (ID1 and ID3) inhibit TGFβ2-induced fibronectin and PAI-1 production in TM cells. We examined the effects of ID1 and ID3 gene expression on TGFβ2-induced ocular hypertension and decreased AH outflow facility in living mouse eyes.

Methods

IOP and AH outflow facility changes were determined using a mouse model of Ad5-hTGFβ2C226S/C288S-induced ocular hypertension. The physiological function of ID1 and ID3 genes were evaluated using Ad5 viral vectors to enhance or knockdown ID1/ID3 gene expression in the TM of BALB/cJ mice. IOP was measured in conscious mice using a Tonolab impact tonometer. AH outflow facilities were determined by constant flow infusion in live mice.

Results

Over-expressing ID1 and ID3 significantly blocked TGFβ2-induced ocular hypertension (P < 0.0001). Although AH outflow facility was significantly decreased in TGFβ2-transduced eyes (P < 0.04), normal outflow facility was preserved in eyes injected concurrently with ID1 or ID3 along with TGFβ2. Knockdown of ID1 or ID3 expression exacerbated TGFβ2-induced ocular hypertension.

Conclusions

Increased expression of ID1 and ID3 suppressed both TGFβ2-elevated IOP and decreased AH outflow facility. ID1 and/or ID3 proteins thus may show promise as future candidates as IOP-lowering targets in POAG.

Inhibitor of DNA Binding 2 (ID2): A Novel Marker for Lymph Node Metastasis in Head and Neck Squamous Cell Carcinoma

BACKGROUND

Although aggressive invasion and sequential lymph node metastasis (LNM) significantly affect the prognosis of patients with head and neck squamous cell carcinoma (HNSCC), studies on identifying the factors that regulate this process remain scarce. This study found an inhibitor of DNA binding 2 (ID2) as a novel molecule involved in the regulation of invasion and LNM of HNSCC and further verified its functional role.

METHODS

The study examined the translational significance between ID2 expression levels and the presence of LNM as well as the prognosis for 119 patients with HNSCC after treatment. In addition, in vitro and in vivo experiments were performed using ID2 gene-modulated HNSCC cell lines to determine the functional role of ID2 in the invasion and LNM of HNSCC.

RESULTS

Elevated levels of ID2 expression were closely associated with the presence of LNM in 119 patients with HNSCC, resulting in a poor prognosis. Overexpression of ID2-induced invasion and LNM of HNSCC cells was observed in vitro and in vivo. By contrast, knockdown of the ID2 gene diminished invasion and LNM of HNSCC cells. In addition, the ID2 expression level increased the expression level of matrix metalloproteinase 1 (MMP1), a molecule downstream to ID2. Furthermore, silencing of MMP1 in ID2-overexpressed HNSCC cells rescued the elevated invasion and LNM capabilities of these cells, suggesting that ID2 enhances invasion and LNM partly via MMP1 activation.

CONCLUSION

In the invasion and LNM of HNSCC, ID2 plays an important role by modulating MMP1 expression, suggesting ID2-MMP1 axis to be a novel alternative therapeutic target for invasion and LNM of HNSCC.

BMP4 promotes the metastasis of gastric cancer by inducing epithelial-mesenchymal transition via ID1

Epithelial-mesenchymal transition (EMT) is a crucial process for cancer cells to acquire metastatic potential, which primarily causes death in gastric cancer (GC) patients. Bone morphogenetic protein 4 (BMP4) is a member of the TGF-β family that plays an indispensable role in human cancers. However, little is known about its roles in GC metastasis. In this study, BMP4 was found to be frequently overexpressed in GC tissues and was correlated with poor patient's prognosis. BMP4 was upregulated in GC cell lines and promoted EMT and metastasis of GC cells both in vitro and in vivo, whereas knockdown of BMP4 significantly inhibited EMT and metastasis of GC cells. Furthermore, the inhibitor of DNA binding 1 (also known as DNA-binding protein inhibitor ID1) was identified as a downstream target of BMP4 using PCR arrays and was upregulated via SMAD1/5/8 phosphorylation. ID1 knockdown attenuated BMP4-induced EMT and invasion in GC cells. Moreover, ID1 overexpression in BMP4 knockdown cells restored the promotion of EMT and cell invasion. In summary, BMP4 induced EMT and promoted GC metastasis by upregulating ID1 expression. Antagonizing BMP4 could be a potential therapeutic strategy for GC metastasis.

miR-433 suppresses tumor progression via Smad2 in non-small cell lung cancer

The role of transforming growth factor beta (TGF-β) in lung cancer is well known. TGF-β-mediated cellular proliferation and angiogenesis through similar to mothers against decapentaplegic homolog 2 (Smad2) protein has also been well elucidated. Smad2 is a predicted target for a microRNAs, namely miR-433. microRNAs are a significant class of non-coding RNAs which play an important role in epigenetic regulation. Here, we show that miR-433 directly binds to Smad2, which is shown to be upregulated in non-small cell lung carcinomas (NSCLC). miR-433 expression is downregulated in NSCLC tissues and cells. Overexpression of miR-433 is associated with decreased expression of proteins - namely Cyclin D1, MMP-2/TIMP-2, and MMP-9, and consequently reduced cell proliferation and invasion phenotypes. Complementation of miR-433 leads to rescue of these disrupted phenotypes. miR-433 mediates its action via Smad2 and Id-1. miR-433 may be a candidate worth further exploration for its prognostic and therapeutic potential in NSCLC.

Role of FoxO Proteins in Cellular Response to Antitumor Agents

FoxO proteins (FoxOs) are transcription factors with a common DNA binding domain that confers selectivity for DNA interaction. In human cells, four proteins (FoxO1, FoxO3, FoxO4 and FoxO6), with redundant activity, exhibit mainly a positive effect on genes involved in cell cycle, apoptosis regulation and drug resistance. Thus, FoxOs can affect cell response to antitumor agent treatment. Their transcriptional activity depends on post-translational modifications, including phosphorylation, acetylation, and mono/poly-ubiquitination. Additionally, alterations in microRNA network impact on FoxO transcripts and in turn on FoxO levels. Reduced expression of FoxO1 has been associated with resistance to conventional agents (e.g., cisplatin) and with reduced efficacy of drug combinations in ovarian carcinoma cells. FoxO3 has been shown as a mediator of cisplatin toxicity in colorectal cancer. A requirement for FoxO3-induced apoptosis has been reported in cells exposed to targeted agents (e.g., gefitinib). Recently, the possibility to interfere with FoxO1 localization has been proposed as a valuable approach to improve cell sensitivity to cisplatin, because nuclear retention of FoxO1 may favor the induction of pro-apoptotic genes. This review focuses on the role of FoxOs in drug treatment response in tumor cells and discusses the impact of the expression of these transcription factors on drug resistance/sensitivity.

Chronic myeloid leukaemia cells require the bone morphogenic protein pathway for cell cycle progression and self-renewal

Leukaemic stem cell (LSC) persistence remains a major obstacle to curing chronic myeloid leukaemia (CML). The bone morphogenic protein (BMP) pathway is deregulated in CML, with altered expression and response to the BMP ligands shown to impact on LSC expansion and behaviour. In this study, we determined whether alterations in the BMP pathway gene signature had any predictive value for therapeutic response by profiling 60 CML samples at diagnosis from the UK SPIRIT2 trial and correlating the data to treatment response using the 18-month follow-up data. There was significant deregulation of several genes involved in the BMP pathway with ACV1C, INHBA, SMAD7, SNAIL1 and SMURF2 showing differential expression in relation to response. Therapeutic targeting of CML cells using BMP receptor inhibitors, in combination with tyrosine kinase inhibitor (TKI), indicate a synergistic mode of action. Furthermore, dual treatment resulted in altered cell cycle gene transcription and irreversible cell cycle arrest, along with increased apoptosis compared to single agents. Targeting CML CD34⁺ cells with BMP receptor inhibitors resulted in fewer cell divisions, reduced numbers of CD34⁺ cells and colony formation when compared to normal donor CD34⁺ cells, both in the presence and absence of BMP4. In an induced pluripotent stem cell (iPSC) model generated from CD34⁺ hematopoietic cells, we demonstrate altered cell cycle profiles and dynamics of ALK expression in CML-iPSCs in the presence and absence of BMP4 stimulation, when compared to normal iPSC. Moreover, dual targeting with TKI and BMP inhibitor prevented the self-renewal of CML-iPSC and increased meso-endodermal differentiation. These findings indicate that transformed stem cells may be more reliant on BMP signalling than normal stem cells. These changes offer a therapeutic window in CML, with intervention using BMP inhibitors in combination with TKI having the potential to target LSC self-renewal and improve long-term outcome for patients.

Neural crest delamination and migration: Looking forward to the next 150 years

Neural crest (NC) cells were described for the first time in 1868 by Wilhelm His. Since then, this amazing population of migratory stem cells has been intensively studied. It took a century to fully unravel their incredible abilities to contribute to nearly every organ of the body. Yet, our understanding of the cell and molecular mechanisms controlling their migration is far from complete. In this review, we summarize the current knowledge on epithelial-mesenchymal transition and collective behavior of NC cells and propose further stops at which the NC train might be calling in the near future.

Increased phosphorylation of eIF2α in chronic myeloid leukemia cells stimulates secretion of matrix modifying enzymes

Recent studies underscore the role of the microenvironment in therapy resistance of chronic myeloid leukemia (CML) cells and leukemia progression. We previously showed that sustained mild activation of endoplasmic reticulum (ER) stress in CML cells supports their survival and resistance to chemotherapy. We now demonstrate, using dominant negative non-phosphorylable mutant of eukaryotic initiation factor 2 α subunit (eIF2α), that phosphorylation of eIF2α (eIF2α-P), which is a hallmark of ER stress in CML cells, substantially enhances their invasive potential and modifies their ability to secrete extracellular components, including the matrix-modifying enzymes cathepsins and matrix metalloproteinases. These changes are dependent on the induction of activating transcription factor-4 (ATF4) and facilitate extracellular matrix degradation by CML cells. Conditioned media from CML cells with constitutive activation of the eIF2α-P/ATF4 pathway induces invasiveness of bone marrow stromal fibroblasts, suggesting that eIF2α-P may be important for extracellular matrix remodeling and thus leukemia cells-stroma interactions. Our data show that activation of stress response in CML cells may contribute to the disruption of bone marrow niche components by cancer cells and in this way support CML progression.

Id-1 promotes migration and invasion of non-small cell lung cancer cells through activating NF-κB signaling pathway

Background

Numerous studies have shown that Id-1 (Inhibitor of differentiation 1) is upregulated in several cancers and associated with tumor malignant characters. However, the clinical significance and biological role of Id-1 in non-small cell lung cancer (NSCLC) remains unclear.

Methods

We used RT-PCR, Western blot and Immunohistochemistry to measure Id-1 expression in NSCLC tissues and matched adjacent noncancerous tissues. The expression pattern of Id-1 in NSCLC tissues was determined by scoring system of immunohistochemical analysis. The Kaplan-Meier method was used to calculate the survival curve, and log-rank test to determine statistical significance. The Id-1 gene was overexpressed or downreuglated with Lentiviral vectors in NSCLC cells. And, the migration ability of NSCLC cells was tested in a Transwell Boyden Chamber.

Results

We found that Id-1 is generally expressed higher in NSCLC tissues compared with matched adjacent noncancerous tissues. We also found that high Id-1 expression in tumor tissues is significantly correlated with tumor progression and poor survival in NSCLC patients. Furthermore, our experimental data revealed that knockdown of Id-1 significantly suppressed the proliferation, migration and invasion of NSCLC cells, whereas ectopic expression of Id-1 promoted the malignant phenotype of NSCLC cells. Mechanistic study showed that NF-κB signaling pathway contributed to the effects of Id-1 in NSCLC cells. Moreover, blocking the NF-κB pathway significantly inhibited the tumor-promoting actions of Id-1 in NSCLC cells.

Conclusions

We identified a tumorigenic role of Id-1 in NSCLC and provided a novel therapeutic target for NSCLC patients.

CDC27 Induces Metastasis and Invasion in Colorectal Cancer via the Promotion of Epithelial-To-Mesenchymal Transition

Distant metastasis is the primary cause of cancer-related death among patients with colorectal cancer (CRC), and the discovery of novel therapeutic targets by further exploring the molecular mechanisms of CRC metastasis is therefore urgently needed. We previously illustrated that CDC27 overexpression promoted proliferation in CRC, but no studies have emphasized the role of CDC27 in cancer metastasis thus far. Our previous data indicated that the expression of CDC27 was significantly associated with distant metastasis in patient tissues, and therefore, in this study, we focused on the investigation of the potential mechanisms of CDC27 in CRC metastasis. The results revealed that CDC27 promoted the metastasis, invasion and sphere-formation capacity of DLD1 cells, but that the inhibition of CDC27 in HCT116 cells suppressed metastasis both in vitro and in vivo. Mechanistic analyses revealed that CDC27 promoted epithelial-to-mesenchymal transition (EMT), as demonstrated by the reduced expression of the epithelial markers ZO-1 and E-cadherin and the enhanced expression of the mesenchymal markers ZEB1 and Snail in HCT116 and DLD1 cells. Further mechanistic investigation indicated that CDC27 promoted metastasis and sphere-formation capacity in an ID1-dependent manner. In conclusion, we first demonstrated the role of CDC27 in cancer metastasis and showed that CDC27 may serve as a promising therapeutic target for CRC.

Prognostic stratification improvement by integrating ID1/ID3/IGJ gene expression signature and immunophenotypic profile in adult patients with B-ALL

Background

Survival of adults with B-Acute Lymphoblastic Leukemia requires accurate risk stratification of patients in order to provide the appropriate therapy. Contemporary techniques, using clinical and cytogenetic variables are incomplete for prognosis prediction.

Methods

To improve the classification of adult patients diagnosed with B-ALL into prognosis groups, two strategies were examined and combined: the expression of the ID1/ID3/IGJ gene signature by RT-PCR and the immunophenotypic profile of 19 markers proposed in the EuroFlow protocol by Flow Cytometry in bone marrow samples.

Results

Both techniques were correlated to stratify patients into prognostic groups. An inverse relationship between survival and expression of the three-genes signature was observed and an immunophenotypic profile associated with clinical outcome was identified. Markers CD10 and CD20 were correlated with simultaneous overexpression of ID1, ID3 and IGJ. Patients with simultaneous expression of the poor prognosis gene signature and overexpression of CD10 or CD20, had worse Event Free Survival and Overall Survival than patients who had either the poor prognosis gene expression signature or only CD20 or CD10 overexpressed.

Conclusion

By utilizing the combined evaluation of these two immunophenotypic markers along with the poor prognosis gene expression signature, the risk stratification can be significantly strengthened. Further studies including a large number of patients are needed to confirm these findings.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0506-4) contains supplementary material, which is available to authorized users.

High expression of ID family and IGJ genes signature as predictor of low induction treatment response and worst survival in adult Hispanic patients with B-acute lymphoblastic leukemia

Background

B-Acute lymphoblastic leukemia (B-ALL) represents a hematologic malignancy with poor clinical outcome and low survival rates in adult patients. Remission rates in Hispanic population are almost 30 % lower and Overall Survival (OS) nearly two years inferior than those reported in other ethnic groups. Only 61 % of Colombian adult patients with ALL achieve complete remission (CR), median overall survival is 11.3 months and event-free survival (EFS) is 7.34 months. Identification of prognostic factors is crucial for the application of proper treatment strategies and subsequently for successful outcome. Our goal was to identify a gene expression signature that might correlate with response to therapy and evaluate the utility of these as prognostic tool in hispanic patients.

Methods

We included 43 adult patients newly diagnosed with B-ALL. We used microarray analysis in order to identify genes that distinguish poor from good response to treatment using differential gene expression analysis. The expression profile was validated by real-time PCR (RT-PCT).

Results

We identified 442 differentially expressed genes between responders and non-responders to induction treatment. Hierarchical analysis according to the expression of a 7-gene signature revealed 2 subsets of patients that differed in their clinical characteristics and outcome.

Conclusions

Our study suggests that response to induction treatment and clinical outcome of Hispanic patients can be predicted from the onset of the disease and that gene expression profiles can be used to stratify patient risk adequately and accurately. The present study represents the first that shows the gene expression profiling of B-ALL Colombian adults and its relevance for stratification in the early course of disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0333-z) contains supplementary material, which is available to authorized users.

Nucleophosmin Mutants Promote Adhesion, Migration and Invasion of Human Leukemia THP-1 Cells through MMPs Up-regulation via Ras/ERK MAPK Signaling

Acute myeloid leukemia (AML) with mutated nucleophosmin (NPM1) has been defined as a unique subgroup in the new classification of myeloid neoplasm, and the AML patients with mutated NPM1 frequently present extramedullary infiltration, but how NPM1 mutants regulate this process remains elusive. In this study, we found that overexpression of type A NPM1 gene mutation (NPM1-mA) enhanced the adhesive, migratory and invasive potential in THP-1 AML cells lacking mutated NPM1. NPM1-mA had up-regulated expression and gelatinolytic matrix metalloprotease-2 (MMP-2)/MMP-9 activity, as assessed by real-time PCR, western blotting and gelatin zymography. Following immunoprecipitation analysis to identify the interaction of NPM1-mA with K-Ras, we focused on the effect of NPM1-mA overexpression on the Ras/Mitogen-activated protein kinase (MAPK) signaling axis and showed that NPM1-mA increased the MEK and ERK phosphorylation levels, as evaluated by western blotting. Notably, a specific inhibitor of the ERK/MAPK pathway (PD98059), but not p38/MAPK, JNK/MAPK or PI3-K/AKT inhibitors, markedly decreased the cell invasion numbers in a transwell assay. Further experiments demonstrated that blocking the ERK/MAPK pathway by PD98059 resulted in reduced MMP-2/9 protein levels and MMP-9 activity. Additionally, NPM1-mA overexpression had down-regulated gene expression and protein production of tissue inhibitor of MMP-2 (TIMP-2) in THP-1 cells. Furthermore, evaluation of gene expression data from The Cancer Genome Atlas (TCGA) dataset revealed that MMP-2 was overexpressed in AML patient samples with NPM1 mutated and high MMP-2 expression associated with leukemic skin infiltration. Taken together, our results reveal that NPM1 mutations contribute to the invasive potential of AML cells through MMPs up-regulation via Ras/ERK MAPK signaling pathway activation and offer novel insights into the potential role of NPM1 mutations in leukemogenesis.

Krüppel-like factor 17, a novel tumor suppressor: its low expression is involved in cancer metastasis

Krüppel-like factor (KLF) family is highly conserved zinc finger transcription factors that regulate cell proliferation, differentiation, apoptosis, and migration. KLF17 is a member of the KLF family. Recent studies have demonstrated that KLF17 low expression and inactivation are caused by microRNA, gene mutation, and loss of heterozygosity in human tumors, which participates in tumor progression. KLF17 low expression increases cancer metastatic viability; its mechanism is that low KLF17 mediates epithelial-mesenchymal transition (EMT) through regulating EMT-related genes expression; the reduced-KLF17 also increases cancer metastasis though upregulating inhibitor of DNA binding 1 (ID1). Additionally, mutant p53 proteins are capable of developing a complex with KLF17, which mediate the depletion of KLF17 inhibiting EMT gene transcription and increases cancer metastasis. KLF17 downregulation also mediates the activation of TGF-β pathway.

ID proteins regulate diverse aspects of cancer progression and provide novel therapeutic opportunities

The inhibitor of differentiation (ID) proteins are helix-loop-helix transcriptional repressors with established roles in stem cell self-renewal, lineage commitment, and niche interactions. While deregulated expression of ID proteins in cancer was identified more than a decade ago, emerging evidence has revealed a central role for ID proteins in neoplastic progression of multiple tumor types that often mirrors their function in physiological stem and progenitor cells. ID proteins are required for the maintenance of cancer stem cells, self-renewal, and proliferation in a range of malignancies. Furthermore, ID proteins promote metastatic dissemination through their role in remodeling the tumor microenvironment and by promoting tumor-associated endothelial progenitor cell proliferation and mobilization. Here, we discuss the latest findings in this area and the clinical opportunities that they provide.

Acute lymphoid leukemia cells with greater stem cell antigen-1 (Ly6a/Sca-1) expression exhibit higher levels of metalloproteinase activity and are more aggressive in vivo

Stem cell antigen-1 (Ly6a/Sca-1) is a gene that is expressed in activated lymphocytes, hematopoietic stem cells and stem cells of a variety of tissues in mice. Despite decades of study its functions remain poorly defined. These studies explored the impact of expression of this stem cell associated gene in acute lymphoid leukemia. Higher levels of Ly6a/Sca-1 expression led to more aggressive leukemia growth in vivo and earlier death of hosts. Leukemias expressing higher levels of Ly6a/Sca-1 exhibited higher levels of matrix metalloproteinases. The results suggest the hypothesis that the more aggressive behavior of Ly6a/Sca-1 expressing leukemias is due at least in part to greater capacity to degrade microenvironmental stroma and invade tissues.

The ID proteins: master regulators of cancer stem cells and tumour aggressiveness

Inhibitor of DNA binding (ID) proteins are transcriptional regulators that control the timing of cell fate determination and differentiation in stem and progenitor cells during normal development and adult life. ID genes are frequently deregulated in many types of human neoplasms, and they endow cancer cells with biological features that are hijacked from normal stem cells. The ability of ID proteins to function as central 'hubs' for the coordination of multiple cancer hallmarks has established these transcriptional regulators as therapeutic targets and biomarkers in specific types of human tumours.

Id proteins: small molecules, mighty regulators

The family of inhibitor of differentiation (Id) proteins is a group of evolutionarily conserved molecules, which play important regulatory roles in organisms ranging from Drosophila to humans. Id proteins are small polypeptides harboring a helix-loop-helix (HLH) motif, which are best known to mediate dimerization with other basic HLH proteins, primarily E proteins. Because Id proteins do not possess the basic amino acids adjacent to the HLH motif necessary for DNA binding, Id proteins inhibit the function of E protein homodimers, as well as heterodimers between E proteins and tissue-specific bHLH proteins. However, Id proteins have also been shown to have E protein-independent functions. The Id genes are broadly but differentially expressed in a variety of cell types. Transcription of the Id genes is controlled by transcription factors such as C/EBPβ and Egr as well as by signaling pathways triggered by different stimuli, which include bone morphogenic proteins, cytokines, and ligands of T cell receptors. In general, Id proteins are capable of inhibiting the differentiation of progenitors of different cell types, promoting cell-cycle progression, delaying cellular senescence, and facilitating cell migration. These properties of Id proteins enable them to play significant roles in stem cell maintenance, vasculogenesis, tumorigenesis and metastasis, the development of the immune system, and energy metabolism. In this review, we intend to highlight the current understanding of the function of Id proteins and discuss gaps in our knowledge about the mechanisms whereby Id proteins exert their diverse effects in multiple cellular processes.

Small-molecule inhibitors of USP1 target ID1 degradation in leukemic cells

Inhibitor of DNA binding 1 (ID1) transcription factor is essential for the proliferation and progression of many cancer types, including leukemia. However, the ID1 protein has not yet been therapeutically targeted in leukemia. ID1 is normally polyubiquitinated and degraded by the proteasome. Recently, it has been shown that USP1, a ubiquitin-specific protease, deubiquitinates ID1 and rescues it from proteasome degradation. Inhibition of USP1 therefore offers a new avenue to target ID1 in cancer. Here, using a ubiquitin-rhodamine-based high-throughput screening, we identified small-molecule inhibitors of USP1 and investigated their therapeutic potential for leukemia. These inhibitors blocked the deubiquitinating enzyme activity of USP1 in vitro in a dose-dependent manner with an IC50 in the high nanomolar range. USP1 inhibitors promoted the degradation of ID1 and, concurrently, inhibited the growth of leukemic cell lines in a dose-dependent manner. A known USP1 inhibitor, pimozide, also promoted ID1 degradation and inhibited growth of leukemic cells. In addition, the growth of primary acute myelogenous leukemia (AML) patient-derived leukemic cells was inhibited by a USP1 inhibitor. Collectively, these results indicate that the novel small-molecule inhibitors of USP1 promote ID1 degradation and are cytotoxic to leukemic cells. The identification of USP1 inhibitors therefore opens up a new approach for leukemia therapy.

Do stress responses promote leukemia progression? An animal study suggesting a role for epinephrine and prostaglandin-E2 through reduced NK activity

In leukemia patients, stress and anxiety were suggested to predict poorer prognosis. Oncological patients experience ample physiological and psychological stress, potentially leading to increased secretion of stress factors, including epinephrine, corticosteroids, and prostaglandins. Here we tested whether environmental stress and these stress factors impact survival of leukemia-challenged rats, and studied mediating mechanisms. F344 rats were administered with a miniscule dose of 60 CRNK-16 leukemia cells, and were subjected to intermittent forced swim stress or to administration of physiologically relevant doses of epinephrine, prostaglandin-E₂ or corticosterone. Stress and each stress factor, and/or their combinations, doubled mortality rates when acutely applied simultaneously with, or two or six days after tumor challenge. Acute administration of the β-adrenergic blocker nadolol diminished the effects of environmental stress, without affecting baseline survival rates. Prolonged β-adrenergic blockade or COX inhibition (using etodolac) also increased baseline survival rates, possibly by blocking tumor-related or normal levels of catecholamines and prostaglandins. Searching for mediating mechanisms, we found that each of the stress factors transiently suppressed NK activity against CRNK-16 and YAC-1 lines on a per NK basis. In contrast, the direct effects of stress factors on CRNK-16 proliferation, vitality, and VEGF secretion could not explain or even contradicted the in vivo survival findings. Overall, it seems that environmental stress, epinephrine, and prostaglandins promote leukemia progression in rats, potentially through suppressing cell mediated immunity. Thus, patients with hematological malignancies, which often exhibit diminished NK activity, may benefit from extended β-blockade and COX inhibition.

The effect of a DNA repair gene on cellular invasiveness: XRCC3 over-expression in breast cancer cells

Over-expression of DNA repair genes has been associated with resistance to radiation and DNA-damage induced by chemotherapeutic agents such as cisplatin. More recently, based on the analysis of genome expression profiling, it was proposed that over-expression of DNA repair genes enhances the invasive behaviour of tumour cells. In this study we present experimental evidence utilizing functional assays to test this hypothesis. We assessed the effect of the DNA repair proteins known as X-ray complementing protein 3 (XRCC3) and RAD51, to the invasive behavior of the MCF-7 luminal epithelial-like and BT20 basal-like triple negative human breast cancer cell lines. We report that stable or transient over-expression of XRCC3 but not RAD51 increased invasiveness in both cell lines in vitro. Moreover, XRCC3 over-expressing MCF-7 cells also showed a higher tumorigenesis in vivo and this phenotype was associated with increased activity of the metalloproteinase MMP-9 and the expression of known modulators of cell-cell adhesion and metastasis such as CD44, ID-1, DDR1 and TFF1. Our results suggest that in addition to its' role in facilitating repair of DNA damage, XRCC3 affects invasiveness of breast cancer cell lines and the expression of genes associated with cell adhesion and invasion.

Increased serum levels of neutrophil gelatinase-associated lipocalin in patients with essential thrombocythemia and polycythemia vera

Neutrophil gelatinaase-associated lipocalin (NGAL) is a glycoprotein bound with matrix metalloproteinase-9 (MMP-9) in human neutrophils, and elevated tissue NGAL expression has been documented in different infectious and inflammatory conditions. Recent evidence suggests that NGAL expression is induced in many types of human cancer. Moreover, NGAL is required for BCR-ABL-induced tumorigenesis. The aim of the present study was to measure serum levels of NGAL in patients with essential thrombocythemia (ET) and polycythemia vera (PV). We also evaluated NGAL levels in patients with ET and PV with and without thrombotic events, to explore a possible correlation of NGAL with platelet and leukocyte activation, and in patients with sepsis. Serum NGAL levels in the study population were significantly higher than in healthy adults and in subjects with sepsis. A correlation between NGAL and the number of white cells and neutrophils was found in patients with PV and ET. NGAL serum levels were not different depending on the presence or not of the JAK2 mutation, and a mutant allele dosage effect was not observed for NGAL levels. Patients with PV and ET with thrombosis did not have significantly higher levels of NGAL. We were unable to demonstrate a significant association between serum NGAL levels and CD11b or CD62 expression. In conclusion, our study reports evidence demonstrating that increased levels of NGAL appear to be a characteristic of patients with PV and ET.

The stem cell gene "inhibitor of differentiation 1" (ID1) is frequently expressed in non-small cell lung cancer

AIMS

Inhibitor of differentiation 1 (ID1) plays a role in cellular differentiation, proliferation, angiogenesis and tumor invasion. As shown recently, ID1 is positively regulated by the tyrosine kinase SRC in lung carcinoma cell lines and with that appears as a potential new therapeutic target in non-small cell carcinoma (NSCLC). To substantiate this hypothesis we examined ID1, SRC and matrix metalloproteinase-9 (MMP-9) immunohistochemically in human NSCLC specimens.

METHODS

From 61 consecutive patient tissue samples of a tumor tissue bank a one core tissue microarray (TMA) was produced and whole slide tissue samples of preinvasive lesions used. The staining of commercial antibodies was assessed by the H-score. Statistical analyses based on Spearman's rank correlation coefficient.

RESULTS

ID1 was expressed in the nucleus in 70% of squamous cell carcinomas and 50% of non-squamous cell carcinomas and in vascular endothelium of non-tumor tissue. Cytoplasmic staining was found in all samples for SRC and in 93% for MMP-9. ID1-positive tissue samples co-expressed SRC and MMP-9 in 94%. In non-squamous cell carcinomas, H-scores of ID1 and SRC correlated with each other (p=0.04). H-score of MMP-9 correlated with tumor grade (p=0.04). The carcinoma findings were reflected in preinvasive lesions.

CONCLUSIONS

We describe for the first time the immunohistochemical expression of ID1 in the majority of NSCLC samples. The almost general co-expression of ID1, SRC and MMP-9 supports their cooperation in vivo and warrants further investigation of ID1 as a therapeutic target.

Abl interactor 1 regulates Src-Id1-matrix metalloproteinase 9 axis and is required for invadopodia formation, extracellular matrix degradation and tumor growth of human breast cancer cells

Abl interactor 1 (Abi1) is a key regulator of actin polymerization/depolymerization. The involvement of Abi1 in the development of abnormal cytoskeletal functions of cancer cells has recently been reported. It remains unclear, however, how Abi1 exerts its effects in tumor cells and whether it contributes to tumor progression in vivo. We report here a novel function for Abi1 in the regulation of invadopodia formation and Src-inhibitor of differentiation protein 1 (Id1)-matrix metalloproteinase (MMP)-9 pathway in MDA-MB-231 human breast cancer cells. Abi1 is found in the invadopodia of MDA-MB-231 cells. Epigenetic silencing of the Abi1 gene by short hairpin RNA in MDA-MB-231 cells impaired the formation of invadopodia and resulted in downregulation of the Src activation and Id1/MMP-9 expression. The decreased invadopodia formation and MMP-9 expression correlate with a reduction in the ability of these cells to degrade extracellular matrix. Remarkably, the knockdown of Abi1 expression inhibited tumor cell proliferation and migration in vitro and slowed tumor growth in vivo. Taken together, these results indicate that the Abi1 signaling plays a critical role in breast cancer progression and suggest that this pathway may serve as a therapeutic target for the treatment of human breast cancer.

Role of leukemia cell invadosome in extramedullary infiltration

Acute myelogenous leukemias (AMLs) are characterized by medullary and extramedullary invasion. We hypothesized that a supramolecular complex, the leukemia-cell invadosome, which contains certain integrins, matrix metalloproteinases (MMPs), and other as-yet unidentified proteins, is essential for tissue invasion and may be central to the phenotypic diversity observed in the clinic. Here we show that the specific binding of MMP-9 to leukocyte surface beta(2) integrin is required for pericellular proteolysis and migration of AML-derived cells. An efficient antileukemia effect was obtained by the hexapeptide HFDDDE, a motif of the MMP-9 catalytic domain that mediates integrin binding: HFDDDE prevented proMMP-9 binding, transmigration through a human endothelial cell layer, and extracellular matrix degradation. Notably, the functional protein anchorage between beta(2) integrin and proMMP-9 described in this study does not involve the enzymatic active sites targeted by known MMP inhibitors. Taken together, our results provide a biochemical working definition for the human leukemia invadosome. Disruption of specific protein complexes within this supramolecular target complex may yield a new class of anti-AML drugs with anti-invasion (rather than or in addition to cytotoxic) attributes.

Smad3 mediates immediate early induction of Id1 by TGF-beta

Id1 is a member of the inhibitor of differentiation (Id) protein family that regulates a wide range of cell functions. Previous studies have shown that expression of the Id1 gene is down-regulated by TGF-beta in epithelial cells, whereas it is up-regulated by BMP in a variety of cell types. During our study of the biological function of TGF-beta1, we found that Id1 can be strongly up-regulated by TGF-beta1 in the human mammary gland epithelial cell line MCF10A. Quantitative real-time RT-PCR has revealed as high as 7.5-fold induction of Id1 mRNA by TGF-beta1 in MCF10A cells after 1 h of TGF-beta1 stimulation, and this induction does not require de novo protein synthesis. Using Smad knockdown and knockout approaches, we have identified Smad3 as the responsible R-Smad for mediating transcriptional activation of the Id1 gene. Chromatin immunoprecipitation assay confirms that Smad3 and Smad4 bind to the upstream region of the Id1 gene. Our results demonstrate that Smad3, but not Smad2, mediates TGF-beta1-dependent early transcriptional induction of Id1.

Lipocalin 2 is required for BCR-ABL-induced tumorigenesis

Our previous studies indicate that reduction of lipocalin 2 (mouse 24p3) expression by either anti-sense or siRNA approaches strongly reduces the overgrowth of BCR-ABL+ mouse myeloid 32D in marrow and spleen of NOD/SCID mice. In this study, we used the mouse bone marrow transplant model to further explore the role of 24p3 in BCR-ABL-induced leukemia. Consistent with our previous findings, when using non-irradiated mice as recipient, donor marrow cells expressing BCR-ABL but lacking 24p3 did not cause leukemia or any disease after 75 days, whereas all mice receiving wild type BCR-ABL donor cells died with CML-like disease. An agar clone of the BCR-ABL+ human CML cell line K562 (C5) that secretes relatively high levels of lipocalin 2 (human NGAL) induced suppression of hematopoiesis in spleen and marrow of mice, leading to early death in contrast to parental K562 or K562 clone (C6) expressing low amounts of NGAL. Compared with K562 cells, overexpressing NGAL in K562 led to a higher apoptosis rate and an atrophy phenotype in the spleen of the inoculated mice. Plasma from both leukemic mice and CML patients showed elevated lipocalin 2 levels compared with healthy individuals. Moreover, we found that a primary stable cell line from wild-type mouse marrow cells expressing BCR-ABL caused solid tumors in nude mice whereas a similar BCR-ABL+ cell line from 24p3 null mice did not. These findings demonstrate that lipocalin 2 has at least two functions related to tumorigenesis, one involving apoptosis induction of normal hematopoietic cells and the other being tissue invasion by leukemia cells.

Identification of a Novel Inhibitor of Differentiation-1 (ID-1) Binding Partner, Caveolin-1, and Its Role in Epithelial-Mesenchymal Transition and Resistance to Apoptosis in Prostate Cancer Cells

Recently, ID-1 (inhibitor of differentiation/DNA binding) is suggested as an oncogene and is reported to promote cell proliferation, invasion, and survival in several types of human cancer cells through multiple signaling pathways. However, how Id-1 interacts with these pathways and the immediate downstream effectors of the Id-1 protein are not known. In this study, using a yeast two-hybrid screening technique, we identified a novel Id-1-interacting protein, caveolin-1 (Cav-1), a cell membrane protein, and a positive regulator of cell survival and metastasis in prostate cancer. Using an immunoprecipitation method, we found that the helix-loop-helix domain of the Id-1 protein was essential for the physical interaction between Id-1 and Cav-1. In addition, we also demonstrated that the physical interaction between Id-1 and Cav-1 played a key role in the epithelial-mesenchymal transition and increased cell migration rate as well as resistance to taxol-induced apoptosis in prostate cancer cells. Furthermore, our results revealed that this effect was regulated by Id-1-induced Akt activation through promoting the binding activity between Cav-1 and protein phosphatase 2A. Our study demonstrates a novel Id-1 binding partner and suggests a molecular mechanism that mediates the function of Id-1 in promoting prostate cancer progression through activation of the Akt pathway leading to cancer cell invasion and resistance to anticancer drug-induced apoptosis.

FoxO tumor suppressors and BCR-ABL-induced leukemia: a matter of evasion of apoptosis

Numerous studies have revealed that the BCR-ABL oncoprotein abnormally engages a multitude of signaling pathways, some of which may be important for its leukemogenic properties. Central to this has been the determination that the tyrosine kinase function of BCR-ABL is mainly responsible for its transforming potential, and can be targeted with small molecule inhibitors, such as imatinib mesylate (Gleevec, STI-571). Despite this apparent success, the development of clinical resistance to imatinib therapy, and the inability of imatinib to eradicate BCR-ABL-positive malignant hematopoietic progenitors demand detailed investigations of additional effector pathways that can be targeted for CML treatment. The promotion of cellular survival via the suppression of apoptotic pathways is a fundamental characteristic of tumor cells that enables resistance to anti-cancer therapies. As substrates of survival kinases such as Akt, the FoxO family of transcription factors, particularly FoxO3a, has emerged as playing an important role in the cell cycle arrest and apoptosis of hematopoietic cells. This review will discuss our current understanding of BCR-ABL signaling with a focus on apoptotic suppressive mechanisms and alternative approaches to CML therapy, as well as the potential for FoxO transcription factors as novel therapeutic targets.

Smad signaling in the neural crest regulates cardiac outflow tract remodeling through cell autonomous and non-cell autonomous effects

Neural crest cells (NCCs) are indispensable for the development of the cardiac outflow tract (OFT). Here, we show that mice lacking Smad4 in NCCs have persistent truncus arteriosus (PTA), severe OFT cushion hypoplasia, defective OFT elongation, and mispositioning of the OFT. Cardiac NCCs lacking Smad4 have increased apoptosis, apparently due to decreased Msx1/2 expression. This contributes to the reduction of NCCs in the OFT. Unexpectedly, mutants have MF20-expressing cardiomyocytes in the splanchnic mesoderm within the second heart field (SHF). This may result from abnormal differentiation or defective recruitment of differentiating SHF cells into OFT. Alterations in Bmp4, Sema3C, and PlexinA2 signals in the mutant OFT, SHF, and NCCs, disrupt the communications among different cell populations. Such disruptions can further affect the recruitment of NCCs into the OFT mesenchyme, causing severe OFT cushion hypoplasia and OFT septation failure. Furthermore, these NCCs have drastically reduced levels of Ids and MT1-MMP, affecting the positioning and remodeling of the OFT. Thus, Smad-signaling in cardiac NCCs has cell autonomous effects on their survival and non-cell autonomous effects on coordinating the movement of multiple cell lineages in the positioning and the remodeling of the OFT.

Enhanced phosphorylation of Nbs1, a member of DNA repair/checkpoint complex Mre11-RAD50-Nbs1, can be targeted to increase the efficacy of imatinib mesylate against BCR/ABL-positive leukemia cells

Nbs1, a member of the Mre11-RAD50-Nbs1 complex, is phosphorylated by ATM, the product of the ataxia-telangiectasia mutated gene and a member of the phosphatidylinositol 3-kinase-related family of serine-threonine kinases, in response to DNA double-strand breaks (DSBs) to regulate DNA damage checkpoints. Here we show that BCR/ABL stimulated Nbs1 expression by induction of c-Myc-dependent transactivation and protection from caspase-dependent degradation. BCR/ABL-related fusion tyrosine kinases (FTKs) such as TEL/JAK2, TEL/PDGFbetaR, TEL/ABL, TEL/TRKC, BCR/FGFR1, and NPM/ALK as well as interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and stem cell factor (SCF) also stimulated Nbs1 expression. Enhanced ATM kinase-dependent phosphorylation of Nbs1 on serine 343 (S343) in response to genotoxic treatment was detected in leukemia cells expressing BCR/ABL and other FTKs in comparison to normal counterparts stimulated with IL-3, GM-CSF, and SCF. Expression of Nbs1-S343A mutant disrupted the intra-S-phase checkpoint, decreased homologous recombinational repair (HRR) activity, down-regulated XIAP expression, and sensitized BCR/ABL-positive cells to cytotoxic drugs. Interestingly, inhibition of Nbs1 phosphorylation by S343A mutant enhanced the antileukemia effect of the combination of imatinib and genotoxic agent.

Reassessment of id1 protein expression in human mammary, prostate, and bladder cancers using a monospecific rabbit monoclonal anti-id1 antibody

Id proteins are a class of dominant-negative antagonists of helix-loop-helix transcription factors and have been shown to control differentiation of a variety of cell types in diverse organisms. Although the importance of Id1 in tumor endothelial cells is well established, the expression and role of the Id1 protein in human cancer cells is controversial. To explore this issue, we developed and characterized a highly specific rabbit monoclonal antibody against Id1 to assess its expression in human breast, prostate, and bladder malignancies. Our results show that in usual types of human mammary carcinomas, the Id1 protein is expressed exclusively in the endothelium. Interestingly, we detected nuclear expression of the Id1 protein in the tumor cells in 10 of 45 cases of poorly differentiated and highly aggressive carcinoma with metaplastic morphology. Similarly, only 1 of 30 prostate cancer samples showed Id1-positive tumor cells, whereas in almost all, endothelial cells showed high Id1 expression. Intriguingly, whereas normal prostate glands do not show any Id1 protein expression, basal layer cells of benign prostate glands in proximity to tumors expressed high levels of the Id1 protein. In contrast to the lack of Id1 expression in the usual types of mammary and prostate cancers, the majority of transitional cell bladder tumors showed Id1 protein expression in both tumor and endothelial cells. These results suggest that further refinement of Id1 expression patterns in a variety of tumor types will be necessary to identify and study the functional roles played by Id1 in human neoplastic processes.

ID proteins as targets in cancer and tools in neurobiology

In eukaryotic organisms, ID proteins are key regulators of development when they function to preserve the stem cell state and prevent lineage determination. By fueling several key features of tumor progression (deregulated proliferation, invasiveness, angiogenesis and metastasis), ID proteins contribute to multiple steps of tumorigenesis. Through oncogenic processes that lead to their aberrant activation in tumors, ID proteins transfer the phenotypic traits of embryonic stem cells to cancer cells. However, ID proteins have recently emerged as highly specialized factors in post-mitotic neurons. The elevated expression of ID proteins arrests neurons in the axon growth mode and prevents cessation of axonal elongation. Here, we discuss how unique properties of ID proteins in cancer cells and neurons pave the way to unexpected therapeutic opportunities.