A nucleolin-DNMT1 regulatory axis in acute myeloid leukemogenesis

Targeting nucleolin improves sensitivity to chemotherapy in acute lymphoblastic leukemia

PURPOSE

Most patients with acute lymphoblastic leukemia (ALL) are treated with chemotherapy as primary care. Although the treatment response is usually positive, resistance and relapse often occur via unknown mechanisms. The purpose of this study was to identify factors associated with chemotherapy resistance in ALL. Here, we present clinical and experimental evidence that overexpression of nucleolin (NCL), a multifunctional nucleolar protein, is linked to drug resistance in ALL.

METHODS

NCL mRNA and protein levels were compared between cell lines and patient samples using qRT-PCR and immunoblotting. NCL mRNA levels were compared between patients of different disease stages from our clinic patients' specimens and publicly available ALL patient datasets. Cells and patient-derived xenograft mouse experiments were performed to assess the effect of NCL inhibition on ALL chemotherapy effectiveness.

RESULTS

Analysis of patient specimens, and publicly available RNA-sequencing datasets revealed a strong correlation between the abundance of NCL and disease relapse or poor survival in B-ALL. Altering NCL expression results in changes in drug sensitivity in ALL cell lines. High levels of NCL upregulated components of the ATP-binding cassette transporters via activation of the ERK pathway, resulting in a decrease in drug accumulation inside the cells. Targeting NCL with AS1411, an NCL-binding oligonucleotide aptamer, significantly increased the sensitivity of ALL cell lines and cells/patient-derived ALL xenograft mice to chemotherapeutic drugs and prolonged mouse survival.

CONCLUSION

Our results highlight NCL as a prognostic marker in B-ALL and a potential therapeutic target to combat chemotherapy resistance in ALL.

Nucleolin‑based targeting strategies in cancer treatment: Focus on cancer immunotherapy (Review)

The benefits of treating several types of cancers using immunotherapy have recently been established. The overexpression of nucleolin (NCL) in a number of types of cancer provides an attractive antigen target for the development of novel anticancer immunotherapeutic treatments. NCL is a multifunctional protein abundantly distributed in the nucleus, cytoplasm and cell membrane. It influences carcinogenesis, and the proliferation, survival and metastasis of cancer cells, leading to cancer progression. Additionally, the meta‑analysis of total and cytoplasmic NCL overexpression indicates a poor prognosis of patients with breast cancer. The AS1411 aptamers currently appear to have therapeutic action in the phase II clinical trial. The authors' research group has recently explored the anticancer function of NCL through the activation of T cells by dendritic cell‑based immunotherapy. The present review describes and discusses the mechanisms through which the multiple functions of NCL can participate in the progression of cancer. In addition, the studies that define the utility of NCL‑dependent anticancer therapies are summarized, with specific focus being paid to cancer immunotherapeutic approaches.

DNA methyltransferase-1 in acute myeloid leukaemia: beyond the maintenance of DNA methylation

DNA methylation is considered an essential epigenetic event during leukaemogenesis and the emergence of drug resistance, which is primarily regulated by DNA methyltransferases. DNA methyltransferase-1 (DNMT1) is one of the members of DNA methyltransferases, in charge of maintaining established methylation. Recently, DNMT1 is shown to promote malignant events of cancers through the epigenetic and non-epigenetic processes. Increasing studies in solid tumours have identified DNMT1 as a therapeutic target and a regulator of therapy resistance; however, it is unclear whether DNMT1 is a critical regulator in acute myeloid leukaemia (AML) and how it works. In this review, we summarized the recent understanding of DNMT1 in normal haematopoiesis and AML and discussed the possible functions of DNMT1 in promoting the development of AML and predicting the sensitivity of hypomethylation agents to better understand the relationship between DNMT1 and AML and to look for new hope to treat AML patients.Key messagesThe function of DNA methyltransferase-1 in acute myeloid leukaemia.DNA methyltransferase-1 predicts the sensitivity of drug and involves the emergence of drug resistance.

RNA binding proteins in MLL-rearranged leukemia

RNA binding proteins (RBPs) have recently emerged as important post-transcriptional gene expression regulators in both normal development and disease. RBPs influence the fate of mRNAs through multiple mechanisms of action such as RNA modifications, alternative splicing, and miR-mediated regulation. This complex and, often, combinatorial regulation by RBPs critically impacts the expression of oncogenic transcripts and, thus, the activation of pathways that drive oncogenesis. Here, we focus on the major features of RBPs, their mechanisms of action, and discuss the current progress in investigating the function of important RBPs in MLL-rearranged leukemia.

Aberrant DNA methylation in multiple myeloma: A major obstacle or an opportunity?

Drug resistance (DR) of cancer cells leading to relapse is a huge problem nowadays to achieve long-lasting cures for cancer patients. This also holds true for the incurable hematological malignancy multiple myeloma (MM), which is characterized by the accumulation of malignant plasma cells in the bone marrow (BM). Although new treatment approaches combining immunomodulatory drugs, corticosteroids, proteasome inhibitors, alkylating agents, and monoclonal antibodies have significantly improved median life expectancy, MM remains incurable due to the development of DR, with the underlying mechanisms remaining largely ill-defined. It is well-known that MM is a heterogeneous disease, encompassing both genetic and epigenetic aberrations. In normal circumstances, epigenetic modifications, including DNA methylation and posttranslational histone modifications, play an important role in proper chromatin structure and transcriptional regulation. However, in MM, numerous epigenetic defects or so-called ‘epimutations’ have been observed and this especially at the level of DNA methylation. These include genome-wide DNA hypomethylation, locus specific hypermethylation and somatic mutations, copy number variations and/or deregulated expression patterns in DNA methylation modifiers and regulators. The aberrant DNA methylation patterns lead to reduced gene expression of tumor suppressor genes, genomic instability, DR, disease progression, and high-risk disease. In addition, the frequency of somatic mutations in the DNA methylation modifiers seems increased in relapsed patients, again suggesting a role in DR and relapse. In this review, we discuss the recent advances in understanding the involvement of aberrant DNA methylation patterns and/or DNA methylation modifiers in MM development, progression, and relapse. In addition, we discuss their involvement in MM cell plasticity, driving myeloma cells to a cancer stem cell state characterized by a more immature and drug-resistant phenotype. Finally, we briefly touch upon the potential of DNA methyltransferase inhibitors to prevent relapse after treatment with the current standard of care agents and/or new, promising (immuno) therapies.

An Assessment on Ethanol-Blended Gasoline/Diesel Fuels on Cancer Risk and Mortality

Although cancer is traditionally considered a genetic disease, the epigenetic abnormalities, including DNA hypermethylation, histone deacetylation, and/or microRNA dysregulation, have been demonstrated as a hallmark of cancer. Compared with gene mutations, aberrant epigenetic changes occur more frequently, and cellular epigenome is more susceptible to change by environmental factors. Excess cancer risks are positively associated with exposure to occupational and environmental chemical carcinogens, including those from gasoline combustion exhausted in vehicles. Of note, previous studies proposed particulate matter index (PMI) as a measure for gasoline sooting tendency, and showed that, compared with the other molecules in gasoline, 1,2,4-Trimethylbenzene, 2-methylnaphthalene and toluene significantly contribute to PMI of the gasoline blends. Mechanistically, both epigenome and genome are important in carcinogenicity, and the genotoxicity of chemical agents has been thoroughly studied. However, less effort has been put into studying the epigenotoxicity. Moreover, as the blending of ethanol into gasoline substitutes for carcinogens, like benzene, toluene, xylene, butadiene, and polycyclic aromatic hydrocarbons, etc., a reduction of secondary aromatics has been achieved in the atmosphere. This may lead to diminished cancer initiation and progression through altered cellular epigenetic landscape. The present review summarizes the most important findings in the literature on the association between exposures to carcinogens from gasoline combustion, cancer epigenetics and the potential epigenetic impacts of biofuels.

Ultrasensitive plasmon enhanced Raman scattering detection of nucleolin using nanochannels of 3D hybrid plasmonic metamaterial

Detection of cancer biomarker is of great significance in cancer diagnostics. In this work, we propose an ultrasensitive and in situ method for plasmon enhanced Raman scattering (PERS) detection of nucleolin (NCL) using a 3D hybrid plasmonic metamaterial (PM). In this aptasensor, thiolated complementary DNA (cDNA) immobilized on PM can hybridize with Rox-labeled NCL-binding aptamer (AS1411-Rox) to form a rigid double-stranded DNA (dsDNA). When NCL passes through the PM nanochannels under a transmembrane voltage bias, it interacts with AS1411-Rox to form G-quadruplexes (G4-AS1411-Rox), resulting in the release of AS1411-Rox from the nanochannels surface and the decrease in PERS signal of the reporter Rox. This change in PERS signals can be recorded in situ without the interference of external environment. With the help of the enrichment function of nanochannel, the present method is able to achieve fast NCL detection within 10 min with a detection limit as low as 71 pM. Furthermore, our method shows excellent specificity, reversibility, uniformity (relative standard deviation of ~6.86%) and reproducibility (~6.65%), providing a new platform for reliable cancer auxiliary diagnosis and drug screening.

A novel nucleolin-binding peptide for Cancer Theranostics

Background: Cancer-specific ligands have been of great interest as pharmaceutical carriers due to the potential for site-specific delivery. In particular, cancer-specific peptides have many advantages over nanoparticles and antibodies, including high biocompatibility, low immunogenicity, and the formation of nontoxic metabolites. The goal of the present study was the development of a novel cancer-specific ligand. Methods: Cancer-specific peptide ligands were screened using a one-bead-one-compound (OBOC) combinatorial method combined with a multiple-antigen-peptide (MAP) synthesis method. The specificity of the peptide ligands toward cancer cells was tested in vitro using a whole-cell binding assay, flow cytometry, and fluorescence confocal microscopy. The tissue distribution profile and therapeutic efficacy of a paclitaxel (PTX)-conjugated peptide ligand was assessed in vivo using xenograft mouse models. Results: We discovered that AGM-330 specifically bound to cancer cells in vitro and in vivo. Treatment with PTX-conjugated AGM-330 dramatically inhibited cancer cell growth in vitro and in vivo compared to treatment with PTX alone. The results of pull-down assay and LC-MS/MS analyses showed that membrane nucleolin (NCL) was the target protein of AGM-330. Although NCL is known as a nuclear protein, we observed that it was overexpressed on the membranes of cancer cells. In particular, membrane NCL neutralization inhibited growth in cancer cells in vitro. Conclusions: In summary, our findings indicated that NCL-targeting AGM-330 has great potential for use in cancer diagnosis and targeted drug delivery in cancer therapy.

RNA-Binding Proteins in Acute Leukemias

Acute leukemias are genetic diseases caused by translocations or mutations, which dysregulate hematopoiesis towards malignant transformation. However, the molecular mode of action is highly versatile and ranges from direct transcriptional to post-transcriptional control, which includes RNA-binding proteins (RBPs) as crucial regulators of cell fate. RBPs coordinate RNA dynamics, including subcellular localization, translational efficiency and metabolism, by binding to their target messenger RNAs (mRNAs), thereby controlling the expression of the encoded proteins. In view of the growing interest in these regulators, this review summarizes recent research regarding the most influential RBPs relevant in acute leukemias in particular. The reported RBPs, either dysregulated or as components of fusion proteins, are described with respect to their functional domains, the pathways they affect, and clinical aspects associated with their dysregulation or altered functions.

Effect of nucleolin on adriamycin resistance via the regulation of B-cell lymphoma 2 expression in Burkitt's lymphoma cells

Nucleolin (NCL, C23) is an important nucleocytoplasmic multifunctional protein. Due to its multifaceted profile and high expression in cancer, NCL is considered to be a marker of drug resistance associated with chemotherapy. However, the biochemical mechanisms in which NCL suppresses drug sensitivity in several cancers have yet to be fully elucidated. This study aims to explore the effect of NCL on drug sensitivity and its potential mechanism in CA46 Burkitt's lymphoma (BL) cells. CA46 BL cells were transfected with lentiviruses carrying the NCL gene (CA46-NCL-overexpression, CA46-NCL-OE), or shRNA sequences that target the endogenous NCL gene (CA46-NCL-knockdown, CA46-NCL-KD). Adriamycin (ADM) IC50 levels for CA46-NCL-overexpressed (OE), CA46-NCL-OE control (OEC), CA46-NCL-knockdown (KD), and CA46-NCL-KD control (KDC) cells were 0.68 ± 0.06 μg/ml, 0.68 ± 0.06 μg/ml, 0.68 ± 0.06 μg/ml, and 0.30 ± 0.04 μg/ml, respectively. Apoptosis rates were significantly increased following NCL KD, whereas the opposite effect was noted in OE cells. A significant reduction of B-cell lymphoma 2 (Bcl-2) mRNA and protein levels in KD cells was observed, while OE cells displayed the opposite effect. The stability of Bcl-2 mRNA was influenced by NCL levels, the half-life of which was extended after NCL-OE, whereas it was reduced in KD cells. Finally, results of RNA-immunoprecipitation assays indicated that NCL could bind to Bcl-2 mRNA in CA46 cells. Taken together, these results suggested that NCL could mediate Bcl-2 expression and stability, and thus enhance ADM resistance in CA46 BL cells.

FOXD3 may be a new cellular target biomarker as a hypermethylation gene in human ovarian cancer

Background

FOXD3 is aberrantly regulated in several tumors, but its underlying mechanisms in ovarian cancer (OC) remains largely unknown. The present study aimed to explore the role and associated mechanisms of FOXD3 in OC.

Methods

Microarray data from GEO was used to analyze differential CpG sites and differentially methylated regions (DMR) in tumor tissues and Illumina 450 genome-wide methylation data was employed. The FOXD3 expression level was determined through qRT-PCR and western blot analysis. Wound healing test, colony formation and flow cytometry assay were utilized to analyze cell migration, proliferation abilities, cell cycle and cell apoptosis, respectively. Finally, the effect of FOXD3 on tumor growth was investigated through in vivo xenograft experiments.

Results

GEO data analysis showed that FOXD3 was hypermethylated in OC tissues. Also, qRT-PCR revealed that FOXD3 was low expressed and methylation-specific PCR (MSP) confirmed that the methylation level of FOXD3 was hypermethylated. Combined treatment of 5-aza-2′-deoxycytidine (5-Aza-dC) could synergistically restored FOXD3 expression. Finally, in vitro and in vivo experiments showed that demethylated FOXD3 decreased cell proliferation and migration abilities, and increased the cell apoptosis. In vivo experiment detected that demethylated FOXD3 restrained tumor growth.

Conclusions

FOXD3 could act as a tumor suppressor to inhibit cell proliferation, migration and promote cell apoptosis in OC cells.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0755-8) contains supplementary material, which is available to authorized users.

HDL-AuNPs-BMS Nanoparticle Conjugates as Molecularly Targeted Therapy for Leukemia

Gold nanoparticles (AuNPs) with adsorbed high-density lipoprotein (HDL) have been utilized to deliver oligonucleotides, yet HDL-AuNPs functionalized with small-molecule inhibitors have not been systematically explored. Here, we report an AuNP-based therapeutic system (HDL-AuNPs-BMS) for acute myeloid leukemia (AML) by delivering BMS309403 (BMS), a small molecule that selectively inhibits AML-promoting factor fatty acid-binding protein 4. To synthesize HDL-AuNPs-BMS, we use AuNP as a template to control conjugate size ensuring a spherical shape to engineer HDL-like nanoparticles containing BMS. The zeta potential and size of the HDL-AuNPs obtained from transmission electron microscopy demonstrate that the HDL-AuNPs-BMS are electrostatically stable and 25 nm in diameter. Functionally, compared to free drug, HDL-AuNPs-BMS conjugates are more readily internalized by AML cells and have more pronounced effects on downregulation of DNA methyltransferase 1 (DNMT1), induction of DNA hypomethylation, and restoration of epigenetically silenced tumor suppressor p15^INK4B coupled with AML growth arrest. Importantly, systemic administration of HDL-AuNPs-BMS conjugates into AML-bearing mice inhibits DNMT1-dependent DNA methylation, induces AML cell differentiation, and diminishes AML disease progression without obvious side effects. In summary, these data, for the first time, demonstrate HDL-AuNPs as an effective delivery platform with great potential to attach distinct inhibitors and HDL-AuNPs-BMS conjugates as a promising therapeutic platform to treat leukemia.

Meeting the needs of breast cancer: A nucleolin's perspective

A major challenge in the management of breast cancer disease has been the development of metastases. Finding new molecular targets and the design of targeted therapeutic approaches to improve the overall survival and quality of life of these patients is, therefore, of great importance. Nucleolin, which is overexpressed in cancer cells and tumor-associated blood vessels, have been implicated in various processes supporting tumorigenesis and angiogenesis. Additionally, its overexpression has been demonstrated in a variety of human neoplasias as an unfavorable prognostic factor, associated with a high risk of relapse and low overall survival. Hence, nucleolin has emerged as a relevant target for therapeutic intervention in cancer malignancy, including breast cancer. This review focus on the contribution of nucleolin for cancer disease and on the development of therapeutic strategies targeting this protein. In this respect, it also provides a critical analysis about the potential and pitfalls of nanomedicine for cancer therapy.

A vicious loop of fatty acid-binding protein 4 and DNA methyltransferase 1 promotes acute myeloid leukemia and acts as a therapeutic target

Aberrant DNA methylation mediated by deregulation of DNA methyltransferases (DNMT) is a key hallmark of acute myeloid leukemia (AML), yet efforts to target DNMT deregulation for drug development have lagged. We previously demonstrated that upregulation of fatty acid-binding protein 4 (FABP4) promotes AML aggressiveness through enhanced DNMT1-dependent DNA methylation. Here, we demonstrate that FABP4 upregulation in AML cells occurs through vascular endothelial growth factor (VEGF) signaling, thus elucidating a crucial FABP4-DNMT1 regulatory feedback loop in AML biology. We show that FABP4 dysfunction by its selective inhibitor BMS309403 leads to downregulation of DNMT1, decrease of global DNA methylation and re-expression of p15INK4B tumor suppressor gene by promoter DNA hypomethylation in vitro, ex vivo and in vivo. Functionally, BMS309403 suppresses cell colony formation, induces cell differentiation, and, importantly, impairs leukemic disease progression in mouse models of leukemia. Our findings highlight AML-promoting properties of the FABP4-DNMT1 vicious loop, and identify an attractive class of therapeutic agents with a high potential for clinical use in AML patients. The results will also assist in establishing the FABP4-DNMT1 loop as a target for therapeutic discovery to enhance the index of current epigenetic therapies.

Targeting epigenetic pathway with gold nanoparticles for acute myeloid leukemia therapy

Leukemia remains a fatal disease for most patients and novel therapeutic strategies are urgently needed. Aberrant DNA methylation is an epigenetic modification that is important in the initiation and progression of leukemia. Here, we demonstrated NCL/miR-221/NFκB/DNMT1 axis as a new molecular pathway promoting aggressive acute myeloid leukemia (AML) leukemogenesis and successfully designed and prepared a nuclear localization signal (NLS) peptide-targeted gold nanoparticles with co-loaded anti-221 and AS1411 (NPsN-AS1411/a221), which can specifically target NCL/miR-221/NFκB/DNMT1 signaling pathway in AML. NPsN-AS1411/a221 synergistically abrogate endogenous miR-221 promoting cancerous growth by inhibiting the expression of p27Kip1 suppressor gene, as well as effectively deregulate the DNMT1 expression through NFκB signaling which led to a reduction of global DNA methylation and the restoration of tumor suppressor p15INK4B via its promoter DNA hypomethylation. Functionally, NPsN-AS1411/a221 remarkably blockage leukemia proliferation and clonogenic potential in NCL/miR-221/NFκB/DNMT1 positive AML cell lines. More importantly, NPsN-AS1411/a221 cooperatively extend the overall survival, lower the white blood cells, reverse splenomegaly, inhibit blasts in bone marrow and metastatic to lung in a preclinical AML animal model. Altogether, our studies provide a proof of concept for multiple-functional drug delivery system that based on the specific gene network involved in tumor growth, and highlight the clinical potential of NCL/miR-221/NFκB/DNMT1-targeted AML nanotherapy.

MUC1-C induces DNA methyltransferase 1 and represses tumor suppressor genes in acute myeloid leukemia

Aberrant DNA methylation is a hallmark of acute myeloid leukemia (AML); however, the regulation of DNA methyltransferase 1 (DNMT1), which is responsible for maintenance of DNA methylation patterns, has largely remained elusive. MUC1-C is a transmembrane oncoprotein that is aberrantly expressed in AML stem-like cells. The present studies demonstrate that targeting MUC1-C with silencing or a pharmacologic inhibitor GO-203 suppresses DNMT1 expression. In addition, MUC1 expression positively correlates with that of DNMT1 in primary AML cells, particularly the CD34+/CD38- population. The mechanistic basis for this relationship is supported by the demonstration that MUC1-C activates the NF-κB p65 pathway, promotes occupancy of the MUC1-C/NF-κB complex on the DNMT1 promoter and drives DNMT1 transcription. We also show that targeting MUC1-C substantially reduces gene promoter-specific DNA methylation, and derepresses expression of tumor suppressor genes, including CDH1, PTEN and BRCA1. In support of these results, we demonstrate that combining GO-203 with the DNMT1 inhibitor decitabine is highly effective in reducing DNMT1 levels and decreasing AML cell survival. These findings indicate that (i) MUC1-C is an attractive target for the epigentic reprogramming of AML cells, and (ii) targeting MUC1-C in combination with decitabine is a potentially effective clinical approach for the treatment of AML.

Silencing DNA methyltransferase 1 (DNMT1) inhibits proliferation, metastasis and invasion in ESCC by suppressing methylation of RASSF1A and DAPK

Our previous study showed DNMT1 is up-regulated in esophageal squamous cell carcinoma (ESCC), which is associated with methylation of tumor suppressors. In the current study, we investigate the role of DNMT1 in ESCC. We found silencing DNMT1 inhibited proliferation, metastasis and invasion of three different ESCC cells, K150, K410 and K450. We also found silencing DNMT1 induced G1 arrest and cell apoptosis in K150, K410 and K450 cells. In vivo study showed silencing DNMT1 suppressed tumor growth in nude mice. In addition, silencing DNMT1 increased expression of tumor suppressor genes, RASSF1A and DAPK, in ESCC cells and ESCC xenograft in nude mice. Moreover, silencing DNMT1 decreased methylation in promoter of RASSF1A and DAPK. In conclusion, our data demonstrated that silencing DNMT1 inhibits proliferation, metastasis and invasion in ESCC by suppressing methylation of RASSF1A and DAPK.

Loss of MEN1 activates DNMT1 implicating DNA hypermethylation as a driver of MEN1 tumorigenesis

Multiple endocrine neoplasia type 1 (MEN1) syndrome results from mutations in the MEN1 gene and causes tumor formation via largely unknown mechanisms. Using a novel genome-wide methylation analysis, we studied tissues from MEN1-parathyroid tumors, Men1 knockout (KO) mice, and Men1 null mouse embryonic fibroblast (MEF) cell lines. We demonstrated that inactivation of menin (the protein product of MEN1) increases activity of DNA (cytosine-5)-methyltransferase 1 (DNMT1) by activating retinoblastoma-binding protein 5 (Rbbp5). The increased activity of DNMT1 mediates global DNA hypermethylation, which results in aberrant activation of the Wnt/β-catenin signaling pathway through inactivation of Sox regulatory genes. Our study provides important insights into the role of menin in DNA methylation and its impact on the pathogenesis of MEN1 tumor development.

New perspectives of physiological and pathological functions of nucleolin (NCL)

Nucleolin (NCL) is a multifunctional protein that mainly localized in the nucleolus, it is also found in the nucleoplasm, cytoplasm and cell membrane. The three main structural domains allow the interaction of NCL with different proteins and RNA sequences. Moreover, specific post-translational modifications and its shuttling property also contribute to its multifunctionality. NCL has been demonstrated to be involved in a variety of aspects such as ribosome biogenesis, chromatin organization and stability, DNA and RNA metabolism, cytokinesis, cell proliferation, angiogenesis, apoptosis regulation, stress response and microRNA processing. NCL has been increasingly implicated in several pathological processes, especially in tumorigenesis and viral infection, which makes NCL a potential target for the development of anti-tumor and anti-viral strategies. In this review, we present an overview on the structure, localizations and various functions of NCL, and further describe how the multiple functions of NCL are correlated to its multiple cellular distributions.

Nanopipette-Based SERS Aptasensor for Subcellular Localization of Cancer Biomarker in Single Cells

Single cell analysis is essential for understanding the heterogeneity, behaviors of cells, and diversity of target analyte in different subcellular regions. Nucleolin (NCL) is a multifunctional protein that is markedly overexpressed in most of the cancer cells. The variant expression levels of NCL in subcellular regions have a marked influence on cancer proliferation and treatments. However, the specificity of available methods to identify the cancer biomarkers is limited because of the high level of subcellular matrix effect. Herein, we proposed a novel technique to increase both the molecular and spectral specificity of cancer diagnosis by using aptamers affinity based portable nanopipette with distinctive surface-enhanced Raman scattering (SERS) activities. The aptamers-functionalized gold-coated nanopipette was used to capture target, while p-mercaptobenzonitrile (MBN) and complementary DNA modified Ag nanoparticles (AgNPs) worked as Raman reporter to produce SERS signal. The SERS signal of Raman nanotag was lost upon NCL capturing via modified DNA aptamers on nanoprobe, which further helped to verify the specificity of nanoprobe. For proof of concept, NCL protein was specifically extracted from different cell lines by aptamers modified SERS active nanoprobe. The nanoprobes manifested specifically good affinity for NCL with a dissociation constant Kd of 36 nM and provided a 1000-fold higher specificity against other competing proteins. Furthermore, the Raman reporter moiety has a vibrational frequency in the spectroscopically silent region (1800-2300 cm-1) with a negligible matrix effect from cell analysis. The subcellular localization and spatial distribution of NCL were successfully achieved in various types of cells, including MCF-7A, HeLa, and MCF-10A cells. This type of probing technique for single cell analysis could lead to the development of a new perspective in cancer diagnosis and treatment at the cellular level.

Inactivation of Receptor Tyrosine Kinases Reverts Aberrant DNA Methylation in Acute Myeloid Leukemia

Purpose: Receptor tyrosine kinases (RTKs) are frequently deregulated in leukemia, yet the biological consequences of this deregulation remain elusive. The mechanisms underlying aberrant methylation, a hallmark of leukemia, are not fully understood. Here we investigated the role of RTKs in methylation abnormalities and characterized the hypomethylating activities of RTK inhibitors.Experimental Design: Whether and how RTKs regulate expression of DNA methyltransferases (DNMTs), tumor suppressor genes (TSGs) as well as global and gene-specific DNA methylation were examined. The pharmacologic activities and mechanisms of actions of RTK inhibitors in vitro, ex vivo, in mice, and in nilotinib-treated leukemia patients were determined.Results: Upregulation of RTKs paralleled DNMT overexpression in leukemia cell lines and patient blasts. Knockdown of RTKs disrupted, whereas enforced expression increased DNMT expression and DNA methylation. Treatment with the RTK inhibitor, nilotinib, resulted in a reduction of Sp1-dependent DNMT1 expression, the diminution of global DNA methylation, and the upregulation of the p15^INK4B gene through promoter hypomethylation in AML cell lines and patient blasts. This led to disruption of AML cell clonogenicity and promotion of cellular apoptosis without obvious changes in cell cycle. Importantly, nilotinib administration in mice and human patients with AML impaired expression of DNMTs followed by DNA hypomethylation, TSG re-expression, and leukemia regression.Conclusions: Our findings demonstrate RTKs as novel regulators of DNMT-dependent DNA methylation and define DNA methylation status in AML cells as a pharmacodynamic marker for their response to RTK-based therapy, providing new therapeutic avenues for RTK inhibitors in overcoming epigenetic abnormalities in leukemia. Clin Cancer Res; 23(20); 6254-66. ©2017 AACR.

Thymoquinone exerts potent growth-suppressive activity on leukemia through DNA hypermethylation reversal in leukemia cells

Thymoquinone (TQ), a bioactive constituent of the volatile oil of Monarda fistulosa and Nigella sativa, possesses cancer-specific growth inhibitory effects, but the underlying molecular mechanisms remain largely elusive. We propose that TQ curbs cancer cell growth through dysfunction of DNA methyltransferase 1 (DNMT1). Molecular docking analysis revealed that TQ might interact with the catalytic pocket of DNMT1 and compete with co-factor SAM/SAH for DNMT1 inhibition. In vitro inhibitory assays showed that TQ decreases DNMT1 methylation activity in a dose-dependent manner with an apparent IC50 of 30 nM. Further, exposure of leukemia cell lines and patient primary cells to TQ resulted in DNMT1 downregulation, mechanistically, through dissociation of Sp1/NFkB complex from DNMT1 promoter. This led to a reduction of DNA methylation, a decrease of colony formation and an increase of cell apoptosis via the activation of caspases. In addition, we developed and validated a sensitive and specific LC-MS/MS method and successfully detected a dynamic change of TQ in mouse plasma after administration of TQ through the tail vein, and determined a tolerable dose of TQ to be 15 mg/kg in mouse. TQ administration into leukemia-bearing mice induced leukemia regression, as indicated by the reversed splenomegaly and the inhibited leukemia cell growth in lungs and livers. Our study for the first time demonstrates that DNMT1-dependent DNA methylation mediates the anticancer actions of TQ, opening a window to develop TQ as a novel DNA hypomethylating agent for leukemia therapy.

G-quadruplex oligonucleotide AS1411 as a cancer-targeting agent: Uses and mechanisms

BACKGROUND

AS1411 is a 26-mer G-rich DNA oligonucleotide that forms a variety of G-quadruplex structures. It was identified based on its cancer-selective antiproliferative activity and subsequently determined to be an aptamer to nucleolin, a multifunctional protein that preferentially binds quadruplex nucleic acids and which is present at high levels on the surface of cancer cells. AS1411 has exceptionally efficient cellular internalization compared to non-quadruplex DNA sequences.

SCOPE OF REVIEW

Recent developments related to AS1411 will be examined, with a focus on its use for targeted delivery of therapeutic and imaging agents.

MAJOR CONCLUSIONS

Numerous research groups have used AS1411 as a targeting agent to deliver nanoparticles, oligonucleotides, and small molecules into cancer cells. Studies in animal models have demonstrated that AS1411-linked materials can accumulate selectively in tumors following systemic administration. The mechanism underlying the cancer-targeting ability of AS1411 is not completely understood, but recent studies suggest a model that involves: (1) initial uptake by macropinocytosis, a form of endocytosis prevalent in cancer cells; (2) stimulation of macropinocytosis by a nucleolin-dependent mechanism resulting in further uptake; and (3) disruption of nucleolin-mediated trafficking and efflux leading to cargoes becoming trapped inside cancer cells.

SIGNIFICANCE

Human trials have indicated that AS1411 is safe and can induce durable remissions in a few patients, but new strategies are needed to maximize its clinical impact. A better understanding of the mechanisms by which AS1411 targets and kills cancer cells may hasten the development of promising technologies using AS1411-linked nanoparticles or conjugates for cancer-targeted therapy and imaging. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.

Expression Profiling of Ribosome Biogenesis Factors Reveals Nucleolin as a Novel Potential Marker to Predict Outcome in AML Patients

Acute myeloid leukemia (AML) is a heterogeneous disease. Prognosis is mainly influenced by patient age at diagnosis and cytogenetic alterations, two of the main factors currently used in AML patient risk stratification. However, additional criteria are required to improve the current risk classification and better adapt patient care. In neoplastic cells, ribosome biogenesis is increased to sustain the high proliferation rate and ribosome composition is altered to modulate specific gene expression driving tumorigenesis. Here, we investigated the usage of ribosome biogenesis factors as clinical markers in adult patients with AML. We showed that nucleoli, the nucleus compartments where ribosome production takes place, are modified in AML by analyzing a panel of AML and healthy donor cells using immunofluorescence staining. Using four AML series, including the TCGA dataset, altogether representing a total of about 270 samples, we showed that not all factors involved in ribosome biogenesis have clinical values although ribosome biogenesis is increased in AML. Interestingly, we identified the regulator of ribosome production nucleolin (NCL) as over-expressed in AML blasts. Moreover, we found in two series that high NCL mRNA expression level was associated with a poor overall survival, particular in elderly patients. Multivariate analyses taking into account age and cytogenetic risk indicated that NCL expression in blast cells is an independent marker of reduced survival. Our study identifies NCL as a potential novel prognostic factor in AML. Altogether, our results suggest that the ribosome biogenesis pathway may be of interest as clinical markers in AML.

DNA methylation by DNMT1 and DNMT3b methyltransferases is driven by the MUC1-C oncoprotein in human carcinoma cells

Aberrant expression of the DNA methyltransferases (DNMTs) and disruption of DNA methylation patterns are associated with carcinogenesis and cancer cell survival. The oncogenic MUC1-C protein is aberrantly overexpressed in diverse carcinomas; however, there is no known link between MUC1-C and DNA methylation. Our results demonstrate that MUC1-C induces the expression of DNMT1 and DNMT3b, but not DNMT3a, in breast and other carcinoma cell types. We show that MUC1-C occupies the DNMT1 and DNMT3b promoters in complexes with NF-κB p65 and drives DNMT1 and DNMT3b transcription. In this way, MUC1-C controls global DNA methylation as determined by analysis of LINE-1 repeat elements. The results further demonstrate that targeting MUC1-C downregulates DNA methylation of the CDH1 tumor suppressor gene in association with induction of E-cadherin expression. These findings provide compelling evidence that MUC1-C is of functional importance to induction of DNMT1 and DNMT3b and, in turn, changes in DNA methylation patterns in cancer cells.

Fatty acid-binding protein FABP4 mechanistically links obesity with aggressive AML by enhancing aberrant DNA methylation in AML cells

Obesity is becoming more prevalent worldwide and is a major risk factor for cancer development. Acute myeloid leukemia (AML), the most common acute leukemia in adults, remains a frequently fatal disease. Here we investigated the molecular mechanisms by which obesity favors AML growth and uncovered the fatty acid-binding protein 4 (FABP4) and DNA methyltransferase 1 (DNMT1) regulatory axis that mediates aggressive AML in obesity. We showed that leukemia burden was much higher in high-fat diet-induced obese mice, which had higher levels of FABP4 and interleukin (IL)-6 in the sera. Upregulation of environmental and cellular FABP4 accelerated AML cell growth in both a cell-autonomous and cell-non-autonomous manner. Genetic disruption of FABP4 in AML cells or in mice blocked cell proliferation in vitro and induced leukemia regression in vivo. Mechanistic investigations showed that FABP4 upregulation increased IL-6 expression and signal transducer and activator of transcription factor 3 phosphorylation leading to DNMT1 overexpression and further silencing of the p15^INK4B tumor-suppressor gene in AML cells. Conversely, FABP4 ablation reduced DNMT1-dependent DNA methylation and restored p15^INK4B expression, thus conferring substantial protection against AML growth. Our findings reveal the FABP4/DNMT1 axis in the control of AML cell fate in obesity and suggest that interference with the FABP4/DNMT1 axis might be a new strategy to treat leukemia.

On the potential role of DNMT1 in acute myeloid leukemia and myelodysplastic syndromes: not another mutated epigenetic driver

DNA methylation is the most common epigenetic modification in the mammalian genome. DNA methylation is governed by the DNA methyltransferases mainly DNMT1, DNMT3A, and DNMT3B. DNMT1 methylates hemimethylated DNA ensuring accurate DNA methylation maintenance. DNMT1 is involved in the proper differentiation of hematopoietic stem cells (HSCs) through the interaction with effector molecules. DNMT1 is deregulated in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) as early as the leukemic stem cell stage. Through the interaction with fundamental transcription factors, non-coding RNAs, fusion oncogenes and by modulating core members of signaling pathways, it can affect leukemic cells biology. DNMT1 action might be also catalytic-independent highlighting a methylation-independent mode of action. In this review, we have gathered some current facts of DNMT1 role in AML and MDS and we also propose some perspectives for future studies.

The hypomethylating agent decitabine prior to chemotherapy improves the therapy efficacy in refractory/relapsed acute myeloid leukemia patients

In this study, we investigated the effect of pre-treatment with demethylating agent decitabine on susceptibility to chemotherapeutic drugs in HL60/ADR, Kasumi-1 and primary AML cells. Cytotoxic effect was increased by decitabine through activation of p53 and inhibition of c-Myc, Survivin and Bcl-2. We demonstrated in clinic that combination of decitabine and HAA consisting of harringtonine, aclarubicin and cytarabine was effective and safe to treat patients with refractory, relapsed or high-risk AML. Decitabine prior to HAA regimen improved the first induction complete response rate, and significantly prolonged overall survival and disease-free survival in these patients compared with HAA alone. These findings support clinic protocols based on decitabine prior to chemotherapy to overcome resistance and improve therapeutic efficacy in AML patients.

Elevated Cellular PD1/PD-L1 Expression Confers Acquired Resistance to Cisplatin in Small Cell Lung Cancer Cells

Although small cell lung cancer (SCLC) is highly responsive to chemotherapies (e.g., cisplatin-etoposide doublet), virtually almost all responsive SCLC patients experience disease recurrence characterized by drug resistance. The mechanisms underlying cisplatin resistance remain elusive. Here we report that cell-intrinsic expression of PD1 and PD-L1, two immune checkpoints, is required for sustained expansion of SCLC cells under cisplatin selection. Indeed, PD1 and PD-L1 were expressed at a higher level in lung cancer cell lines, tumor tissues, and importantly, in SCLC cells resistant to cisplatin (H69R, H82R), when compared to respective controls. Genetic abrogation of PD1 and PD-L1 in H69R and H82R cells decreased their proliferation rate, and restored their sensitivity to cisplatin. Mechanistically, PD-L1 upregulation in H69R and H82R cells was attributed to the overexpression of DNA methyltransferase 1 (DNMT1) or receptor tyrosine kinase KIT, as knockdown of DNMT1 or KIT in H69R and H82R cells led to PD-L1 downregulation. Consequently, combined knockdown of PD-L1 with KIT or DNMT1 resulted in more pronounced inhibition of H69R and H82R cell growth. Thus, cell intrinsic PD1/PD-L1 signaling may be a predictor for poor efficacy of cisplatin treatment, and targeting the cellular PD1/PD-L1 axis may improve chemosensitization of aggressive SCLC.

Modified AS1411 Aptamer Suppresses Hepatocellular Carcinoma by Up-Regulating Galectin-14

Aptamers are small synthetic oligonucleotides that bind to target proteins with high specificity and affinity. AS1411 is an aptamer that binds to nucleolin, which is overexpressed in the cytoplasm and occurs on the surface of cancer cells. We investigated the therapeutic potential of aptamers in hepatocellular carcinoma (HCC) by evaluating anti-tumor effects and confirming the affinity and specificity of AS1411- and modified AS1411-aptamers in HCC cells. Cell growth was assessed using the MTS assay, and cell death signaling was explored by immunoblot analysis. Fluorescence-activated cell sorting was performed to evaluate the affinity and specificity of AS1411-aptamers in SNU-761 HCC cells. We investigated the in vivo effects of the AS1411-aptamer using BALB/c nude mice in a subcutaneous xenograft model with SNU-761 cells. Treatment with a modified AS1411-aptamer significantly decreased in vitro (under normoxic [P = 0.035] and hypoxic [P = 0.018] conditions) and in vivo (under normoxic conditions, P = 0.041) HCC cell proliferation compared to control aptamers. AS1411- and control aptamers failed to control HCC cell proliferation. However, AS1411- and the modified AS1411-aptamer did not induce caspase activation. Decrease in cell growth by AS1411 or modified AS1411 was not prevented by caspase or necrosis inhibitors. In a microarray, AS1411 significantly enhanced galectin-14 expression. Suppression of HCC cell proliferation by the modified AS1411-aptamer was attenuated by galectin-14 siRNA transfection. Modified AS1411-aptamer suppressed HCC cell growth in vitro and in vivo by up-regulating galectin-14 expressions. Modified AS1411-aptamers may have therapeutic potential as a novel targeted therapy for HCC.

Epigenetic alterations in the suprachiasmatic nucleus and hippocampus contribute to age-related cognitive decline

Circadian rhythm dysfunction and cognitive decline, specifically memory loss, frequently accompany natural aging. Circadian rhythms and memory are intertwined, as circadian rhythms influence memory formation and recall in young and old rodents. Although, the precise relationship between circadian rhythms and memory is still largely unknown, it is hypothesized that circadian rhythm disruption, which occurs during aging, contributes to age-associated cognitive decline, specifically memory loss. While there are a variety of mechanisms that could mediate this effect, changes in the epigenome that occur during aging has been proposed as a potential candidate. Interestingly, epigenetic mechanisms, such as DNA methylation and sirtuin1 (SIRT1) are necessary for both circadian rhythms and memory. During aging, similar alterations of epigenetic mechanisms occur in the suprachiasmatic nucleus (SCN) and hippocampus, which are necessary for circadian rhythm generation and memory, respectively. Recently, circadian rhythms have been linked to epigenetic function in the hippocampus, as some of these epigenetic mechanisms oscillate in the hippocampus and are disrupted by clock gene deletion. The current paper will review how circadian rhythms and memory change with age, and will suggest how epigenetic changes in these processes might contribute to age-related cognitive decline.

Inhibition of EZH2 via activation of SAPK/JNK and reduction of p65 and DNMT1 as a novel mechanism in inhibition of human lung cancer cells by polyphyllin I

Background

Polyphyllin I (PPI), a bioactive phytochemical extracted from the Rhizoma of Paris polyphylla, has been reported to exhibit anti-cancer activity. However, the detailed mechanism underlying this remains to be elucidated.

Methods

Cell viability and cell cycle distribution were measured using a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and flow cytometry assays, respectively. The expression of enhancer of zeste homolog 2 (EZH2) mRNA was measured by quantitative real time PCR (qRT-PCR). Western blot analysis was performed to examine the phosphorylation and protein expression of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), p65, DNA methyltransferase 1 (DNMT1) and EZH2. Exogenous expression of p65, DNMT1, and EZH2 were carried out by transient transfection assays. Promoter activity of EZH2 gene was determined using Secrete-Pair Dual Luminescence Assay Kit. A xenografted tumor model in nude mice and bioluminescent imaging system were used to further test the effect of PPI in vivo.

Results

We showed that PPI significantly inhibited growth and induced cell cycle arrest of non-small cell lung cancer (NSCLC) cells in a dose-dependent manner. Mechanistically, we found that PPI increased the phosphorylation of SAPK/JNK, reduced protein expression of p65 and DNMT1. The inhibitor of SAPK/JNK (SP600125) blocked the PPI-inhibited p65 and DNMT1 protein expression. Interestingly, exogenously expressed p65 overcame PPI-inhibited protein expression of DNMT1. Moreover, PPI reduced EZH2 protein, mRNA, and promoter activity; overexpression of EZH2 resisted the PPI-inhibited cell growth, and intriguingly, negative feedback regulation of SAPK/JNK signaling. Finally, exogenous expression of DNMT1 antagonized the PPI-suppressed EZH2 protein expression. Consistent with this, PPI inhibited tumor growth, protein expression levels of p65, DNMT1 and EZH2, and increased phosphorylation of SAPK/JNK in vivo.

Conclusion

Our results show that PPI inhibits growth of NSCLC cells through SAPK/JNK-mediated inhibition of p65 and DNMT1 protein levels, subsequently; this results in the reduction of EZH2 gene expression. The interactions among p65, DNMT1 and EZH2, and feedback regulation of SAPK/JNK by EZH2 converge on the overall responses of PPI. This study reveals a novel mechanism for regulating EZH2 gene in response to PPI and suggests a new strategy for NSCLC associated therapy.

Combining disulfiram and poly(l-glutamic acid)-cisplatin conjugates for combating cisplatin resistance

A poly(l-glutamic acid) graft polyethylene glycol-cisplatin complex (PGA-CisPt) performs well in reducing the toxicity of free cisplatin and greatly enhances the accumulation and retention of cisplatin in solid tumors. However, there is a lack of effective treatment options for cisplatin-resistant tumors. A major reason for this is the dense PEG shell, which ensures that the PGA-CisPt maintains a long retention time in the blood that may result in it bypassing the tumor cells or failing to be endocytosed within the tumor microenvironment. Consequently, the cisplatin from PGA-CisPt is released to the extracellular space in the presence of cisplatin-resistant tumor cells and the resistant problem to free cisplatin still valid. Therefore, we devised a strategy to combat the resistance of cisplatin in the tumor microenvironment using nanoparticles-loaded disulfiram (NPs-DSF) as a modulator. In vitro, cisplatin, in combination with DSF, had a synergistic effect and decreased cell survival rate of cisplatin-resistant A549DDP cells. This effect was also observed when combining PGA-CisPt with NPs-DSF. Similarly, in Balb/C nude mice with A549DDP xenografts, NPs-DSF improved PGA-CisPt effectiveness in inhibiting tumor growth while maintaining low toxicity. Our data demonstrate that DSF reduces intracellular glutathione (GSH) levels, inhibits NFκB activity, and modulates the expression of apoptosis-related proteins Bcl-2 and Bax, thereby improves the effectiveness of cisplatin in resistant cell lines. Here, we provide a promising method for overcoming cisplatin resistance in tumors, while maintaining the in vivo benefits of the PGA-CisPt complex.

Nucleolin overexpression is associated with an unfavorable outcome for ependymoma: a multifactorial analysis of 176 patients

Ependymoma typically has a better overall survival rate than most gliomas. Only a few comprehensive clinical studies have been published, but these are mostly from Western countries and use small sample sizes. Histopathological classification is not sufficient to show variable outcomes, and fails to show prognostic markers of the diverse outcomes; hence, it is essential to understand biological mechanisms. In this study, 176 ependymoma samples (World Health Organization grade II and III) were reviewed at Huashan Hospital. Both children and adults were included. We performed multifactorial analyses of clinical prognostic factors and the biomolecular marker expressions of nucleolin, epidermal growth factor receptor (EGFR) and caveolae-associated protein caveolin-1 by immunohistochemistry. We identified the probabilities of progression-free survival and overall survival using univariate and multivariate statistical methods. The participants were diagnosed with ependymomas between 2002 and 2010, including distributions of tumor locations in intracranial and extracranial regions. Nucleolin was overexpressed in 67 % of our samples, demonstrating a subgroup with poor outcome; particularly infratentorial and anaplastic ependymomas. There was no significant correlation between the expression of EGFR and caveolin-1 and clinical outcomes. Clinically, inferior prognosis was observed with regard to age (<18 years), intracranial location, high grade ependymomas, and incomplete resection. We found that nucleolin was an unfavorable prognostic predictor for ependymomas. Moreover, our findings show a subset of aggravating outcomes in high-grade and posterior fossa tumors.

Cap-Independent Translation in Hematological Malignancies

Hematological malignancies are a heterogeneous group of diseases deriving from blood cells progenitors. Although many genes involved in blood cancers contain internal ribosome entry sites (IRESes), there has been only few studies focusing on the role of cap-independent translation in leukemia and lymphomas. Expression of IRES trans-acting factors can also be altered, and interestingly, BCL-ABL1 fusion protein expressed from “Philadelphia” chromosome, found in some types of leukemia, regulates several of them. A mechanism involving c-Myc IRES and cap-independent translation and leading to resistance to chemotherapy in multiple myeloma emphasize the contribution of cap-independent translation in blood cancers and the need for more work to be done to clarify the roles of known IRESes in pathology and response to chemotherapeutics.

Mechanistic studies of anticancer aptamer AS1411 reveal a novel role for nucleolin in regulating Rac1 activation

AS1411 is a G-rich quadruplex-forming oligodeoxynucleotide that binds specifically to nucleolin, a protein found on the surface and in the cytoplasm of most malignant cells but absent from the surface/cytoplasm of most normal cells. AS1411 has shown promising clinical activity and is being widely used as a tumor-targeting agent, but its mechanism of action is not fully understood. Previously, we showed that AS1411 is taken up in cancer cells by macropinocytosis (fluid phase endocytosis) and subsequently stimulates further macropinocytosis by a nucleolin-dependent mechanism. In the current study, we have investigated the significance and molecular mechanisms of AS1411-induced macropinocytosis. Our results indicate that the antiproliferative activity of AS1411 in various cell lines correlated with its capacity to stimulate macropinocytosis. In DU145 prostate cancer cells, AS1411 induced activation of EGFR, Akt, p38, and Rac1. Activation of Akt and p38 were not critical for AS1411 activity because Akt activation was not observed in all AS1411-responsive cell lines and knockdown of p38 had no effect on AS1411's ability to inhibit proliferation. On the other hand, activation of EGFR and Rac1 appeared to play a role in AS1411 activity in all cancer cell lines examined (DU145, MDA-MB-468, A549, LNCaP) and their inhibition significantly reduced AS1411-mediated macropinocytosis and AS1411 antiproliferative activity. Interestingly, downregulation of nucleolin expression by siRNA also produced a substantial increase in activated Rac1, revealing a previously unknown role for nucleolin as a negative regulator of Rac1 activation. Our results are consistent with a model whereby AS1411 binding to nucleolin leads to sustained activation of Rac1 and causes methuosis, a novel type of nonapoptotic cell death characterized by hyperstimulation of macropinocytosis. We speculate that methuosis is a tumor/metastasis suppressor mechanism that opposes the malignant functions of Rac1 and that cancer cells may overexpress nucleolin to surmount this barrier.

The DNA Methyltransferase DNMT1 and Tyrosine-Protein Kinase KIT Cooperatively Promote Resistance to 5-Aza-2'-deoxycytidine (Decitabine) and Midostaurin (PKC412) in Lung Cancer Cells

Lung cancer cells are sensitive to 5-aza-2'-deoxycytidine (decitabine) or midostaurin (PKC412), because decitabine restores the expression of methylation-silenced tumor suppressor genes, whereas PKC412 inhibits hyperactive kinase signaling, which is essential for cancer cell growth. Here, we demonstrated that resistance to decitabine (decitabine(R)) or PKC412 (PKC412(R)) eventually results from simultaneously remethylated DNA and reactivated kinase cascades. Indeed, both decitabine(R) and PKC412(R) displayed the up-regulation of DNA methyltransferase DNMT1 and tyrosine-protein kinase KIT, the enhanced phosphorylation of KIT and its downstream effectors, and the increased global and gene-specific DNA methylation with the down-regulation of tumor suppressor gene epithelial cadherin CDH1. Interestingly, decitabine(R) and PKC412(R) had higher capability of colony formation and wound healing than parental cells in vitro, which were attributed to the hyperactive DNMT1 or KIT, because inactivation of KIT or DNMT1 reciprocally blocked decitabine(R) or PKC412(R) cell proliferation. Further, DNMT1 knockdown sensitized PKC412(R) cells to PKC412; conversely, KIT depletion synergized with decitabine in eliminating decitabine(R). Importantly, when engrafted into nude mice, decitabine(R) and PKC412(R) had faster proliferation with stronger tumorigenicity that was caused by the reactivated KIT kinase signaling and further CDH1 silencing. These findings identify functional cross-talk between KIT and DNMT1 in the development of drug resistance, implying the reciprocal targeting of protein kinases and DNA methyltransferases as an essential strategy for durable responses in lung cancer.

The roles of nucleolin subcellular localization in cancer

Nucleolin (NCL) is one of the most abundant non ribosomal protein of the nucleolus where it plays a central role in polymerase I transcription. NCL is also found outside of the nucleolus, in the nucleoplasm, cytoplasm as well as on the cell membrane. It acts in all cell compartments to control cellular homeostasis and therefore each cellular pool of NCL can play a different role in cancer development. NCL overexpression and its increased localization at the cell membrane is a common feature of several tumor cells. In cancer cells, NCL overexpression influences cell survival, proliferation and invasion through its action on different cellular pathways. In this review, we describe how the multiple functions of NCL that are associated to its multiple cellular localization can participate to the development of cancer.

Genetic mutations in epigenetic modifiers as therapeutic targets in acute myeloid leukemia

INTRODUCTION

Despite enormous insights into the molecular mechanisms of acute myeloid leukemia (AML) pathophysiology, this disease is still fatal in the majority of patients, highlighting the urgent need for novel biomarkers useful in AML prognosis and therapy.

AREAS COVERED

The advent of modern sequencing technologies has allowed the identification of genetic mutations in genes encoding for specific enzymes involved in the epigenetic regulation of gene expression. The authors review recent data demonstrating the involvement of mutations in genes encoding for epigenetic players and their complex combination with somatic genetic mutations in the pathogenesis of AML. They also discuss the prognostic and therapeutic implications of these findings.

EXPERT OPINION

Current clinical and preclinical studies are underscoring the importance of targeting epigenetic modifiers as new biomarkers for a better prognostic risk stratification and therapeutic evaluation of intermediate-risk patients. Combining data from traditional and modern methodologies will allow a definition of the complex networks of epigenetic changes and molecular interactions between candidate epitargets and key regulators of hematopoiesis. It will thus be possible to achieve an overview of potential aberrant mechanisms driving leukemogenesis in different classes of AML patients. Such an improved approach could pave the way towards 'personalized' therapies.

AML1/ETO cooperates with HIF1α to promote leukemogenesis through DNMT3a transactivation

The mechanisms by which AML1/ETO (A/E) fusion protein induces leukemogenesis in acute myeloid leukemia (AML) without mutagenic events remain elusive. Here we show that interactions between A/E and hypoxia-inducible factor 1α (HIF1α) are sufficient to prime leukemia cells for subsequent aggressive growth. In agreement with this, HIF1α is highly expressed in A/E-positive AML patients and strongly predicts inferior outcomes, regardless of gene mutations. Co-expression of A/E and HIF1α in leukemia cells causes a higher cell proliferation rate in vitro and more serious leukemic status in mice. Mechanistically, A/E and HIF1α form a positive regulatory circuit and cooperate to transactivate DNMT3a gene leading to DNA hypermethylation. Pharmacological or genetic interventions in the A/E-HIF1α loop results in DNA hypomethylation, a re-expression of hypermethylated tumor-suppressor p15(INK4b) and the blockage of leukemia growth. Thus high HIF1α expression serves as a reliable marker, which identifies patients with a poor prognosis in an otherwise prognostically favorable AML group and represents an innovative therapeutic target in high-risk A/E-driven leukemia.

C23 protein meditates bone morphogenetic protein-2-mediated EMT via up-regulation of Erk1/2 and Akt in gastric cancer

In our previous study, the epithelial-to-mesenchymal transition (EMT) has been identified to be involved in gastric cancer progression. Notably, nuclear protein C23 and bone morphogenetic protein-2 (BMP2) have been linked into EMT. However, the specific mechanisms underlying BMP2 pathway-mediated EMT are not still unraveled. In this study, we adopted immunohistochemistry and immunoblotting to determine the expression of C23 and BMP2 receptor II (BMPR-II) in 90 gastric cancer samples and cell lines. Subsequently, relevant cell lines were selected to be treated with si-C23 or si-BMPRII and the detection of in vitro assay. Our results revealed that both C23 and BMPRII were aberrantly and constitutively expressed in gastric cancer specimens and cell lines, whose expression was positively associated with metastasis, stage and differentiation, and portended poor survival outcome of gastric cancer patients. In vitro assay validated the increased expression of p-Erk1/2, p-Akt, vimentin, N-cadherin, and MMP2 in BMP2-stimulated MGC803 cells, which was in a dose-dependent manner. By contrast, si-C23 treatment attenuated the BMP2-stimulated expression of p-Erk1/2, p-Akt, vimentin, N-cadherin, and MMP2. Also, the treatment of either si-C23 or si-BMPRII decreased the ability of migration and invasion of MGC803 cells. In conclusion, C23 mediates BMP2-induced EMT progression via the up-regulation of Erk1/2 and Akt signaling pathway in gastric cancer, which indicated both C23 and BMPRII pathway could be recommended as prospective targets or biomarkers to antagonize the progression of gastric cancer.

Imprinted genes in myeloid lineage commitment in normal and malignant hematopoiesis

Genomic imprinting is characterized by the parent-of-origin monoallelic expression of several diploid genes because of epigenetic regulation. Imprinted genes (IGs) are key factors in development, supporting the ability of a genotype to produce phenotypes in response to environmental stimuli. IGs are highly expressed during prenatal stages but are downregulated after birth. They also affect aspects of life other than growth such as cognition, behavior, adaption to novel environments, social dominance and memory consolidation. Deregulated genomic imprinting leads to developmental disorders and is associated with solid and blood cancer as well. Several data have been published highlighting the involvement of IGs in as early as the very small embryonic-like stem cells stage and further during myeloid lineage commitment in normal and malignant hematopoiesis. Therefore, we have assembled the current knowledge on the topic, based mainly on recent findings, trying not to focus on a particular cluster but rather to have a global view of several different IGs in hematopoiesis.

ADAMTS2 gene dysregulation in T/myeloid mixed phenotype acute leukemia

Background

Mixed phenotype acute leukemias (MPAL) include acute leukemias with blasts that express antigens of more than one lineage, with no clear evidence of myeloid or lymphoid lineage differentiation. T/myeloid (T/My) MPAL not otherwise specified (NOS) is a rare leukemia that expresses both T and myeloid antigens, accounting for less than 1% of all leukemias but 89% of T/My MPAL. From a molecular point of view, very limited data are available on T/My MPAL NOS.

Case presentation

In this report we describe a T/My MPAL NOS case with a complex rearrangement involving chromosomes 5 and 14, resulting in overexpression of the ADAM metallopeptidase with thrombospondin type 1 motif, 2 (ADAMTS2) gene due to its juxtaposition to the T cell receptor delta (TRD) gene segment.

Conclusion

Detailed molecular cytogenetic characterization of the complex rearrangement in the reported T/My MPAL case allowed us to observe ADAMTS2 gene overexpression, identifying a molecular marker that may be useful for monitoring minimal residual disease. To our knowledge, this is the first evidence of gene dysregulation due to a chromosomal rearrangement in T/My MPAL NOS.