FOXC1

Gene Summary

Gene:FOXC1; forkhead box C1
Aliases: ARA, IGDA, IHG1, FKHL7, IRID1, RIEG3, FREAC3, FREAC-3
Location:6p25
Summary:This gene belongs to the forkhead family of transcription factors which is characterized by a distinct DNA-binding forkhead domain. The specific function of this gene has not yet been determined; however, it has been shown to play a role in the regulation of embryonic and ocular development. Mutations in this gene cause various glaucoma phenotypes including primary congenital glaucoma, autosomal dominant iridogoniodysgenesis anomaly, and Axenfeld-Rieger anomaly. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:forkhead box protein C1
HPRD
Source:NCBIAccessed: 11 August, 2015

Ontology:

What does this gene/protein do?
Show (51)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 11 August 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Oligonucleotide Array Sequence Analysis
  • Transcription
  • Microarray Analysis
  • Tumor Markers
  • Cell Adhesion
  • Mutation
  • Gene Regulatory Networks
  • Promoter Regions
  • Receptor, erbB-2
  • Single Nucleotide Polymorphism
  • Gene Knockdown Techniques
  • Cell Movement
  • Disease Progression
  • Chromosome 6
  • DNA-Binding Proteins
  • beta Catenin
  • Messenger RNA
  • DNA Methylation
  • CpG Islands
  • Gene Expression Profiling
  • Drug Resistance
  • Neoplastic Cell Transformation
  • Cancer Gene Expression Regulation
  • Transcriptional Activation
  • Neoplasm Invasiveness
  • Prostate Cancer
  • Breast Cancer
  • RTPCR
  • Neoplasm Metastasis
  • Staging
  • Base Sequence
  • Up-Regulation
  • Epithelial-Mesenchymal Transition
  • Cell Proliferation
  • Signal Transduction
  • Synovial Sarcoma
  • Gene Expression
  • Transcription Factors
  • Genome-Wide Association Study
  • Proto-Oncogene Proteins
  • Forkhead Transcription Factors
Tag cloud generated 11 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (3)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: FOXC1 (cancer-related)

Rijal S, Fleming S, Cummings N, et al.
Inositol polyphosphate 4-phosphatase II (INPP4B) is associated with chemoresistance and poor outcome in AML.
Blood. 2015; 125(18):2815-24 [PubMed] Related Publications
Phosphoinositide signaling regulates diverse cellular functions. Phosphoinositide-3 kinase (PI3K) generates PtdIns(3,4,5)P3 and PtdIns(3,4)P2, leading to the activation of proliferative and anti-apoptotic signaling pathways. Termination of phosphoinositide signaling requires hydrolysis of inositol ring phosphate groups through the actions of PtdIns(3,4,5)P3 3-phosphatase (PTEN), PtdIns(3,4,5)P3 5-phosphatases (eg, SHIP), and PtdIns(3,4)P2 4-phosphatases (eg, INPP4B). The biological relevance of most of these phosphoinositide phosphatases in acute myeloid leukemia (AML) remains poorly understood. Mass spectrometry-based gene expression profiling of 3-, 4- and 5-phosphatases in human AML revealed significant overexpression of INPP4B. Analysis of an expanded panel of 205 AML cases at diagnosis revealed INPP4B overexpression in association with reduced responses to chemotherapy, early relapse, and poor overall survival, independent of other risk factors. Ectopic overexpression of INPP4B conferred leukemic resistance to cytosine arabinoside (ara-C), daunorubicin, and etoposide. Expression of a phosphatase inert variant (INPP4B C842A) failed to abrogate resistance of AML cells to chemotherapy in vitro or in vivo. In contrast, targeted suppression of endogenously overexpressed INPP4B by RNA interference sensitized AML cell lines and primary AML to chemotherapy. These findings demonstrate a previously unsuspected and clinically relevant role for INPP4B gain of function as a mediator of chemoresistance and poor survival outcome in AML independent of its phosphoinositide phosphatase function.

Gabor KM, Schermann G, Lautner-Csorba O, et al.
Impact of single nucleotide polymorphisms of cytarabine metabolic genes on drug toxicity in childhood acute lymphoblastic leukemia.
Pediatr Blood Cancer. 2015; 62(4):622-8 [PubMed] Related Publications
BACKGROUND: Cytarabine (cytosine arabinoside, ara-C) is a chemotherapeutical agent used in the treatment of pediatric acute lymphoblastic leukemia (ALL). Adverse drug reactions, such as interpatient variability in sensitivity to ara-C, are considerable and may cause difficulties during chemotherapy. Single nucleotide polymorphisms (SNPs) can play a significant role in modifying nucleoside-drug pharmacokinetics and pharmacodynamics and thus the development of adverse effects. Our aim was to determine whether polymorphisms in genes encoding transporters and enzymes responsible for the metabolism of ara-C are associated with toxicity and clinical outcome in a patient population with childhood ALL.
PROCEDURE: We studied 8 SNPs in the CDA, DCK, DCTD, SLC28A3, and SLC29A1 genes in 144 patients with childhood acute lymphoblastic leukemia treated according to ALLIC BFM 1990, 1995 and 2002 protocols.
RESULTS: DCK rs12648166 and DCK rs4694362 SNPs were associated with hematologic toxicity (OR = 2.63, CI 95% = 1.37-5.04, P = 0.0036 and OR = 2.53, CI 95% = 1.34-4.80, P = 0.0044, respectively).
CONCLUSIONS: Our results indicate that DCK polymorphisms might be important genetic risk factors for hematologic toxicity during ALL treatment with ara-C. Individualized chemotherapy based on genetic profiling may help to optimize ara-C dosing, leading to improvements in clinical outcome and reduced toxicity.

Hoang VT, Buss EC, Wang W, et al.
The rarity of ALDH(+) cells is the key to separation of normal versus leukemia stem cells by ALDH activity in AML patients.
Int J Cancer. 2015; 137(3):525-36 [PubMed] Related Publications
To understand the precise disease driving mechanisms in acute myeloid leukemia (AML), comparison of patient matched hematopoietic stem cells (HSC) and leukemia stem cells (LSC) is essential. In this analysis, we have examined the value of aldehyde dehydrogenase (ALDH) activity in combination with CD34 expression for the separation of HSC from LSC in 104 patients with de novo AML. The majority of AML patients (80 out of 104) had low percentages of cells with high ALDH activity (ALDH(+) cells; <1.9%; ALDH-rare AML), whereas 24 patients had relatively numerous ALDH(+) cells (≥1.9%; ALDH-numerous AML). In patients with ALDH-rare AML, normal HSC could be separated by their CD34(+) ALDH(+) phenotype, whereas LSC were exclusively detected among CD34(+) ALDH(-) cells. For patients with ALDH-numerous AML, the CD34(+) ALDH(+) subset consisted mainly of LSC and separation from HSC was not feasible. Functional analyses further showed that ALDH(+) cells from ALDH-numerous AML were quiescent, refractory to ARA-C treatment and capable of leukemic engraftment in a xenogenic mouse transplantation model. Clinically, resistance to chemotherapy and poor long-term outcome were also characteristic for patients with ALDH-numerous AML providing an additional risk-stratification tool. The difference in spectrum and relevance of ALDH activity in the putative LSC populations demonstrates, in addition to phenotypic and genetic, also functional heterogeneity of leukemic cells and suggests divergent roles for ALDH activity in normal HSC versus LSC. By acknowledging these differences our study provides a new and useful tool for prospective identification of AML cases in which separation of HSC from LSC is possible.

Blonska M, Zhu Y, Chuang HH, et al.
Jun-regulated genes promote interaction of diffuse large B-cell lymphoma with the microenvironment.
Blood. 2015; 125(6):981-91 [PubMed] Article available free on PMC after 05/02/2016 Related Publications
Diffuse large B-cell lymphoma (DLBCL) is an aggressive disease with a high proliferation rate. However, the molecular and genetic features that drive the aggressive clinical behavior of DLBCL are not fully defined. Here, we have demonstrated that activated Jun signaling is a frequent event in DLBCL that promotes dissemination of malignant cells. Downregulation of Jun dramatically reduces lymphoma cell adhesion to extracellular matrix proteins, subcutaneous tumor size in nude mice, and invasive behavior, including bone marrow infiltration and interaction with bone marrow stromal cells. Furthermore, using a combination of RNA interference and gene expression profiling, we identified Jun target genes that are associated with disseminated lymphoma. Among them, ITGAV, FoxC1, and CX3CR1 are significantly enriched in patients with 2 or more extranodal sites. Our results point to activated Jun signaling as a major driver of the aggressive phenotype of DLBCL.

Ara MN, Matsuda T, Hyodo M, et al.
Construction of an aptamer modified liposomal system targeted to tumor endothelial cells.
Biol Pharm Bull. 2014; 37(11):1742-9 [PubMed] Related Publications
We describe herein the development of a high affinity and specific DNA aptamer as a new ligand for use in liposomal nanoparticles to target cultured mouse tumor endothelial cells (mTECs). Active targeted nanotechnology based drug delivery systems are currently of great interest, due to their potential for reducing side effects and facilitating the delivery of cytotoxic drugs or genes in a site specific manner. In this study, we report on a promising aptamer candidate AraHH036 that shows selective binding towards mTECs. The aptamer does not bind to normal cells, normal endothelial cells or tumor cells. Therefore, we synthesized an aptamer-polyethylene glycol (PEG) lipid conjugate and prepared aptamer based liposomes (ALPs) by the standard lipid hydration method. First, we quantified the higher capacity of ALPs to internalize into mTECs by incubating ALPs containing 1 mol%, 5 mol% and 10 mol% aptamer of total lipids and compared the results to those for unmodified PEGylated liposomes (PLPs). A confocal laser scanning microscope (CLSM) uptake study indicated that the ALPs were taken up more efficiently than PLPs. The measured Kd value of the ALPs was 142 nM. An intracellular trafficking study confirmed that most of the rhodamine labeled ALPs were taken up and co-localized with the green lysotracker, thus confirming that they were located in lysosomes. Finally, using an aptamer based proteomics approach, the molecular target protein of the aptamer was identified as heat shock protein 70 (HSP70). The results suggest that these ALPs offer promise as a new carrier molecule for delivering anti-angiogenesis drugs to tumor vasculature.

Ghosh S, Gu F, Wang CM, et al.
Genome-wide DNA methylation profiling reveals parity-associated hypermethylation of FOXA1.
Breast Cancer Res Treat. 2014; 147(3):653-9 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
Early pregnancy in women by the age of 20 is known to have a profound effect on reduction of lifelong breast cancer risk as compared to their nulliparous counterparts. Additional pregnancies further enhance the protection against breast cancer development. Nationwide trend of delayed pregnancy may contribute to the recently reported increase in the incidence of advanced breast cancer among young women in this country. The underlying mechanism for the parity-associated reduction of breast cancer risk is not clearly understood. The purpose of the current study is to use whole-genome DNA methylation profiling to explore a potential association between parity and epigenetic changes in breast tissue from women with early parity and nulliparity. Breast tissue was collected from age-matched cancer-free women with early parity (age < 20; n = 15) or nulliparity (n = 13). The methyl-CpG binding domain-based capture-sequencing technology was used for whole-genome DNA methylation profiling. Potential parity-associated hypermethylated genes were further verified by locus-specific pyrosequencing, using an expanded cohort of parous (n = 19) and nulliparous (n = 16) women that included the initial samples used in the global analysis. Our study identified six genes that are hypermethylated in the parous group (P < 0.05). Pyrosequencing confirmed parity-associated hypermethylation at multiple CpG islands of the FOXA1 gene, which encodes a pioneer factor that facilitates chromatin binding of estrogen receptor α. Our work identifies several potential methylation biomarkers for parity-associated breast cancer risk assessment. In addition, the results are consistent with the notion that parity-associated epigenetic silencing of FOXA1 contributes to long-term attenuation of the estrogenic impact on breast cancer development.

Anderson E, Salisbury V
Rapid in-vitro testing for chemotherapy sensitivity in leukaemia patients.
Adv Biochem Eng Biotechnol. 2014; 145:189-214 [PubMed] Related Publications
Bioluminescent bacterial biosensors can be used in a rapid in vitro assay to predict sensitivity to commonly used chemotherapy drugs in acute myeloid leukemia (AML). The nucleoside analog cytarabine (ara-C) is the key agent for treating AML; however, up to 30 % of patients fail to respond to treatment. Screening of patient blood samples to determine drug response before commencement of treatment is needed. To achieve this aim, a self-bioluminescent reporter strain of Escherichia coli has been constructed and evaluated for use as an ara-C biosensor and an in vitro assay has been designed to predict ara-C response in clinical samples. Transposition mutagenesis was used to create a cytidine deaminase (cdd)-deficient mutant of E. coli MG1655 that responded to ara-C. The strain was transformed with the luxCDABE operon and used as a whole-cell biosensor for development an 8-h assay to determine ara-C uptake and phosphorylation by leukemic cells. Intracellular concentrations of 0.025 μmol/L phosphorylated ara-C were detected by significantly increased light output (P < 0.05) from the bacterial biosensor. Results using AML cell lines with known response to ara-C showed close correlation between the 8-h assay and a 3-day cytotoxicity test for ara-C cell killing. In retrospective tests with 24 clinical samples of bone marrow or peripheral blood, the biosensor-based assay predicted leukemic cell response to ara-C within 8 h. The biosensor-based assay may offer a predictor for evaluating the sensitivity of leukemic cells to ara-C before patients undergo chemotherapy and allow customized treatment of drug-sensitive patients with reduced ara-C dose levels. The 8-h assay monitors intracellular ara-CTP (cytosine arabinoside triphosphate) levels and, if fully validated, may be suitable for use in clinical settings.

Lin Z, Sun L, Chen W, et al.
miR-639 regulates transforming growth factor beta-induced epithelial-mesenchymal transition in human tongue cancer cells by targeting FOXC1.
Cancer Sci. 2014; 105(10):1288-98 [PubMed] Related Publications
Epithelial-to-mesenchymal transition (EMT) is implicated in embryonic development and various pathological events. Transforming growth factor beta (TGFβ) has been reported to induce EMT in tumor cells, which is a critical step in the process of metastasis leading to cancer spreading and treatment failure. However, the involvement of microRNA during the EMT process in tongue squamous cell carcinoma (TSCC) remains to be determined. To address this question, TSCC cell lines SCC9 and CAL27 were treated with human recombinant TGFβ1 for 48 h. miRNA microarray illustrated that miR-639 was significantly downregulated in TGFβ-treated SCC9 cells. Ectopic expression of miR-639 with miRNA mimics effectively blocked TGFβ-induced EMT in SCC9 and CAL27 cells, but inhibition of miR-639 in SCC9 and CAL27 cells with antisense oligonucleotides induced EMT. Computational microRNA target predictions detected a conserved sequence matching to the seed region of miR-639 in the 3'-UTR of FOXC1 mRNA. Luciferase reporter assays revealed that miR-639 targets FOXC1. Ectopic expression of FOXC1 induces EMT in TSCC cells. Silencing FOXC1 expression blocked TGFβ-induced EMT in SCC9 cells. Clinically, reduced miR-639 expression was associated with metastasis in TSCC and poor patient survival. The data from the present study suggest that reduced expression of miR-639 underscores the mechanism of TGFβ-induced EMT in TSCC by targeting FOXC1 and may serve as therapeutic targets in the process of metastasis.

Nagel S, Meyer C, Kaufmann M, et al.
Deregulated FOX genes in Hodgkin lymphoma.
Genes Chromosomes Cancer. 2014; 53(11):917-33 [PubMed] Related Publications
FOX genes encode transcription factors which regulate basic developmental processes during embryogenesis and in the adult. Several FOX genes show deregulated expression in particular malignancies, representing oncogenes or tumor suppressors. Here, we screened six Hodgkin lymphoma (HL) cell lines for FOX gene activity by comparative microarray profiling, revealing overexpression of FOXC1 and FOXD1, and reduced transcription of FOXN3, FOXO1, and FOXP1. In silico expression analyses of these FOX gene candidates in HL patient samples supported the cell line data. Chromosomal analyses demonstrated an amplification of the FOXC1 locus at 6p25 and a gain of the FOXR2 locus at Xp11, indicting genomic aberrations for their upregulation. Comparative expression profiling and ensuing stimulation experiments revealed implementation of the TGFβ- and WNT-signaling pathways in deregulation of FOXD1 and FOXN3. Functional analysis of FOXP1 implicated miR9 and miR34a as upstream regulators and PAX5, TCF3, and RAG2 as downstream targets. A similar exercise for FOXC1 revealed repression of MSX1 and activation of IPO7, both mediating inhibition of the B-cell specific homeobox gene ZHX2. Taken together, our data show that aberrantly expressed FOX genes and their downstream targets are involved in the pathogenesis of HL via deregulation of B-cell differentiation and may represent useful diagnostic markers and/or therapeutic targets.

Pan F, Yao J, Chen Y, et al.
A novel long non-coding RNA FOXCUT and mRNA FOXC1 pair promote progression and predict poor prognosis in esophageal squamous cell carcinoma.
Int J Clin Exp Pathol. 2014; 7(6):2838-49 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
Accumulating evidences demonstrated that many long non-coding RNAs (lncRNAs) can cooperate with the adjacent coding genes, forming into "lncRNA-mRNA gene pairs" in multiple biological cellular processes. Here, we showed that a novel long non-coding RNA FOXCUT (FOXC1 promoter upstream transcript) and its neighboring gene FOXC1 played a similar important role in the oncogenesis and progression of esophageal squamous cell carcinoma (ESCC). In this study, the expression of FOXCUT/FOXC1 was measured in 82 ESCC tissues and adjacent noncancerous tissues by real-time quantitative PCR (qPCR). The prognostic significance of the lncRNA-mRNA gene pair was evaluated using Kaplan-Meier survival analysis and log-rank test. Cell biological experiments were performed in ESCC cell lines to explore their functions in tumor progression. Notably elevated FOXCUT and FOXC1 expression levels were observed in cancerous tissues compared to adjacent noncancerous tissues (86.6% and 84.1%, respectively; P < 0.01), showing strong correlations with poor differentiation, advanced lymph node classification and metastasis (P < 0.05). Moreover, patients with upregulated FOXCUT or FOXC1 experienced a significantly worse prognosis than those with downregulated FOXCUT or FOXC1 (P < 0.001 and P = 0.014, respectively). In addition, the expression of FOXCUT was positively correlated with expression of FOXC1 in ESCC specimens. And the expression of FOXC1 was also decreased as the FOXCUT expression was silenced by siRNA. Assays in vitro demonstrated that knockdown of either FOXCUT or FOXC1 remarkably inhibited cell proliferation, colony formation, migration, invasion in ESCC cells. In conclusion, FOXCUT may be functionally involved in the tumor progression and survival of ESCC patients, at least in part, by modulating FOXC1. FOXCUT and FOXC1 may function as a lncRNA-mRNA gene pair, which may represent a potential prognostic biomarker and therapeutic target for ESCC patients.

Chen WL, Wang JH, Zhao AH, et al.
A distinct glucose metabolism signature of acute myeloid leukemia with prognostic value.
Blood. 2014; 124(10):1645-54 [PubMed] Related Publications
Acute myeloid leukemia (AML) is a group of hematological malignancies with high heterogeneity. There is an increasing need to improve the risk stratification of AML patients, including those with normal cytogenetics, using molecular biomarkers. Here, we report a metabolomics study that identified a distinct glucose metabolism signature with 400 AML patients and 446 healthy controls. The glucose metabolism signature comprises a panel of 6 serum metabolite markers, which demonstrated prognostic value in cytogenetically normal AML patients. We generated a prognosis risk score (PRS) with 6 metabolite markers for each patient using principal component analysis. A low PRS was able to predict patients with poor survival independently of well-established markers. We further compared the gene expression patterns of AML blast cells between low and high PRS groups, which correlated well to the metabolic pathways involving the 6 metabolite markers, with enhanced glycolysis and tricarboxylic [corrected] acid cycle at gene expression level in low PRS group. In vitro results demonstrated enhanced glycolysis contributed to decreased sensitivity to antileukemic agent arabinofuranosyl cytidine (Ara-C), whereas inhibition of glycolysis suppressed AML cell proliferation and potentiated cytotoxicity of Ara-C. Our study provides strong evidence for the use of serum metabolites and metabolic pathways as novel prognostic markers and potential therapeutic targets for AML.

Castilla MÁ, López-García MÁ, Atienza MR, et al.
VGLL1 expression is associated with a triple-negative basal-like phenotype in breast cancer.
Endocr Relat Cancer. 2014; 21(4):587-99 [PubMed] Related Publications
Vestigial-like 1 (VGLL1) is a poorly characterized gene encoding a transcriptional co-activator structurally homologous to TAZ and YAP that modulates the Hippo pathway in Drosophila. In this study, we examined the expression of VGLL1 and its intronic miRNA, miR-934, in breast cancer. VGLL1 and miR-934 expression miRNA profiling was carried out on frozen samples of grade 3 invasive ductal carcinomas. VGLL1 protein was also examined in 433 sporadic and BRCA1-associated breast carcinomas on tissue microarrays. RNA-seq data from The Cancer Genome Atlas (TCGA) was used to confirm differences in VGLL1 and miR-934 expression in different breast cancer subtypes, and to correlate their expression with that of other genes and miRNAs. Of 28 miRNAs differentially expressed in estrogen receptor (ER)-positive and ER-negative grade 3 breast carcinomas, miR-934 was most strongly upregulated in ER-negative carcinomas, and its expression was correlated with that of VGLL1. Nuclear VGLL1 expression was observed in 13% of sporadic breast carcinomas, and while VGLL1 was only occasionally found in luminal A (0.70%) and B (5.60%) carcinomas, it was often expressed in HER2-positive (17%), triple-negative (TN) breast carcinomas (>40%) and BRCA1-associated TN carcinomas (>50%). These findings were confirmed in the TCGA dataset, which revealed positive associations with luminal progenitor genes (GABRP, SLC6A14, FOXC1, PROM1, and BBOX1) and strong negative correlations with ER-associated genes (ESR1, C6ORF211, GATA3, and FOXA1). Moreover, VGLL1 expression was associated with reduced overall survival. In conclusion, VGLL1 and miR-934 are mainly expressed in sporadic and BRCA1-associated TN basal-like breast carcinomas, and their coordinated expression, at least partially mediated by the direct modulation of ESR1, might be involved in the maintenance of a luminal progenitor phenotype.

Weng H, Huang H, Dong B, et al.
Inhibition of miR-17 and miR-20a by oridonin triggers apoptosis and reverses chemoresistance by derepressing BIM-S.
Cancer Res. 2014; 74(16):4409-19 [PubMed] Related Publications
Cancer cell chemoresistance arises in part through the acquisition of apoptotic resistance. Leukemia cells resistant to chemotherapy-induced apoptosis have been found to be sensitive to oridonin, a natural agent with potent anticancer activity. To investigate its mechanisms of action in reversing chemoresistance, we compared the response of human leukemia cells with oridonin and the antileukemia drugs Ara-C and VP-16. Compared with HL60 cells, K562 and K562/ADR cells displayed resistance to apoptosis stimulated by Ara-C and VP-16 but sensitivity to oridonin. Mechanistic investigations revealed that oridonin upregulated BIM-S by diminishing the expression of miR-17 and miR-20a, leading to mitochondria-dependent apoptosis. In contrast, neither Ara-C nor VP-16 could reduce miR-17 and miR-20a expression or could trigger BIM-S-mediated apoptosis. Notably, silencing miR-17 or miR-20a expression by treatment with microRNA (miRNA; miR) inhibitors or oridonin restored sensitivity of K562 cells to VP-16. Synergistic effects of oridonin and VP-16 were documented in cultured cells as well as mouse tumor xenograft assays. Inhibiting miR-17 or miR-20a also augmented the proapoptotic activity of oridonin. Taken together, our results identify a miRNA-dependent mechanism underlying the anticancer effect of oridonin and provide a rationale for its combination with chemotherapy drugs in addressing chemoresistant leukemia cells.

Zahreddine HA, Culjkovic-Kraljacic B, Assouline S, et al.
The sonic hedgehog factor GLI1 imparts drug resistance through inducible glucuronidation.
Nature. 2014; 511(7507):90-3 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
Drug resistance is a major hurdle in oncology. Responses of acute myeloid leukaemia (AML) patients to cytarabine (Ara-C)-based therapies are often short lived with a median overall survival of months. Therapies are under development to improve outcomes and include targeting the eukaryotic translation initiation factor (eIF4E) with its inhibitor ribavirin. In a Phase II clinical trial in poor prognosis AML, ribavirin monotherapy yielded promising responses including remissions; however, all patients relapsed. Here we identify a novel form of drug resistance to ribavirin and Ara-C. We observe that the sonic hedgehog transcription factor glioma-associated protein 1 (GLI1) and the UDP glucuronosyltransferase (UGT1A) family of enzymes are elevated in resistant cells. UGT1As add glucuronic acid to many drugs, modifying their activity in diverse tissues. GLI1 alone is sufficient to drive UGT1A-dependent glucuronidation of ribavirin and Ara-C, and thus drug resistance. Resistance is overcome by genetic or pharmacological inhibition of GLI1, revealing a potential strategy to overcome drug resistance in some patients.

Wang H, Li W, Guo R, et al.
An intragenic long noncoding RNA interacts epigenetically with the RUNX1 promoter and enhancer chromatin DNA in hematopoietic malignancies.
Int J Cancer. 2014; 135(12):2783-94 [PubMed] Related Publications
RUNX1, a master regulator of hematopoiesis, is the most commonly perturbed target of chromosomal abnormalities in hematopoietic malignancies. The t(8;21) translocation is found in 30-40% of cases of acute myeloid leukemia (AML). Recent whole-exome sequencing also reveals mutations and deletions of RUNX1 in some solid tumors. We describe a RUNX1-intragenic long noncoding RNA RUNXOR that is transcribed as unspliced transcript from an upstream overlapping promoter. RUNXOR was upregulated in AML samples and in response to Ara-C treatment in vitro. RUNXOR utilizes its 3'-terminal fragment to directly interact with the RUNX1 promoter and enhancers and participates in the orchestration of an intrachromosomal loop. The 3' region of RUNXOR also participates in long-range interchromosomal interactions with chromatin regions that are involved in multiple RUNX1 translocations. These data suggest that RUNXOR noncoding RNA may function as a previously unidentified candidate component that is involved in chromosomal translocation in hematopoietic malignancies.

Tao HF, Liu YS, Fang JL, et al.
Significance of SODD expression in childhood acute lymphoblastic leukemia and its influence on chemotherapy.
Genet Mol Res. 2014; 13(1):2020-31 [PubMed] Related Publications
This study explored the clinical significance of silencer of death domain (SODD) expression in childhood acute lymphoblastic leukemia (ALL) and its influence on chemotherapy as well as the effect of SODD expression on apoptosis of leukemic cells. The expression of SODD proteins in different ALL groups was determined by immunocytochemistry. The SODD RNAi-interfering plasmid was constructed and transferred to Jurkat cells, and the effects of SODD expression on cell proliferation and apoptosis were analyzed using the MTT and FCM methods. The expressions of SODD, Phospho-NF-κB-P65, Bcl-2, and Caspase 3 were detected by Western blot analysis. The expression of SODD proteins was significantly higher in the ALL groups than in the control group (P < 0.05). The positive expression rate of SODD was significantly higher in refractory/relapsed and clinical high-risk groups than in standard-risk, initial treatment, and complete remission groups (P < 0.05). Microtubule-targeting drugs such as vincristine and taxol can notably down-regulate SODD expression during apoptosis, whereas DNR, and Ara-c cannot. The sensitivity of Jurkat cells to chemotherapeutic drugs increased with down-regulated SODD expression induced by SODD-interfering plasmid transfection. The sensitivity of the cells transfected with SODD-cloning genes decreased. SODD expression was high in the ALL children. These findings indicated that SODD over-expression might be correlated with the clinical classification, curative effect, and prognosis of ALL cells. Microtubule-targeting drugs can specifically down-regulate SODD expression in leukemic cells, thereby increasing the sensitivity of leukemic cells to SODD-targeting chemotherapeutics. In contrast, increased SODD expression tends to reduce sensitivity.

Chen J, Wang W, Zhang Y, et al.
The roles of miR-200c in colon cancer and associated molecular mechanisms.
Tumour Biol. 2014; 35(7):6475-83 [PubMed] Related Publications
The expression of miR-200c has been widely reported to be elevated in tumor tissues and sera of patients with colorectal cancer (CRC) and has been found to correlate with poor prognosis. However, how miR-200c regulates the apoptosis, survival, invasion, metastasis, and tumor growth in colon cancer cells remains to be fully elucidated. This study seeks to further investigate the role of miR-200c in colon cancer development. The expression of miR-200c in tumor and peritumoral tissues of 101 colon cancer patients was measured by real-time PCR. miR-200c expression in HCT-116 and HT-29 colon cancer cells was silenced by adenovirus-carried expression of antisense mRNA against miR-200c. The protein levels of PTEN, p53 Ser(15), PP1, and activated caspase-3 in HCT-116 and HT-29 cells were measured by Western blot. This study demonstrated that the expression of miR-200c was significantly higher in tumor tissues than in peritumoral tissues of colon cancer patients. The elevated miR-200c expression significantly correlated with the TNM stage, lymph node metastasis, and invasion of colon cancer. Silencing miR-200c expression significantly induced cell apoptosis, inhibited long-term survival, invasion, and metastasis, and delayed xenograft tumor growth. Importantly, silencing miR-200c expression sensitized the therapeutic effect of Ara-C (Cytarabine). The effects of silencing miR-200c expression were associated with upregulation of PTEN protein and p53 Ser(15) phosphorylation levels in HCT-116 cells and PTEN protein expression in HT-29 cells. In conclusion, miR-200c functions as an oncogene in colon cancer cells through regulating tumor cell apoptosis, survival, invasion, and metastasis as well as xenograft tumor growth through inhibition of PTEN expression and p53 phosphorylation.

Ma J, Hu Y, Guo M, et al.
hERG potassium channel blockage by scorpion toxin BmKKx2 enhances erythroid differentiation of human leukemia cells K562.
PLoS One. 2013; 8(12):e84903 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
BACKGROUND: The hERG potassium channel can modulate the proliferation of the chronic myelogenous leukemic K562 cells, and its role in the erythroid differentiation of K562 cells still remains unclear.
PRINCIPAL FINDINGS: The hERG potassium channel blockage by a new 36-residue scorpion toxin BmKKx2, a potent hERG channel blocker with IC50 of 6.7 ± 1.7 nM, enhanced the erythroid differentiation of K562 cells. The mean values of GPA (CD235a) fluorescence intensity in the group of K562 cells pretreated by the toxin for 24 h and followed by cytosine arabinoside (Ara-C) treatment for 72 h were about 2-fold stronger than those of K562 cells induced by Ara-C alone. Such unique role of hERG potassium channel was also supported by the evidence that the effect of the toxin BmKKx2 on cell differentiation was nullified in hERG-deficient cell lines. During the K562 cell differentiation, BmKKx2 could also suppress the expression of hERG channels at both mRNA and protein levels. Besides the function of differentiation enhancement, BmKKx2 was also found to promote the differentiation-dependent apoptosis during the differentiation process of K562 cells. In addition, the blockage of hERG potassium channel by toxin BmKKx2 was able to decrease the intracellular Ca(2+) concentration during the K562 cell differentiation, providing an insight into the mechanism of hERG potassium channel regulating this cellular process.
CONCLUSIONS/SIGNIFICANCE: Our results revealed scorpion toxin BmKKx2 could enhance the erythroid differentiation of leukemic K562 cells via inhibiting hERG potassium channel currents. These findings would not only accelerate the functional research of hERG channel in different leukemic cells, but also present the prospects of natural scorpion toxins as anti-leukemic drugs.

Xu Y, Shao QS, Yao HB, et al.
Overexpression of FOXC1 correlates with poor prognosis in gastric cancer patients.
Histopathology. 2014; 64(7):963-70 [PubMed] Related Publications
AIMS: The aim of this study was to determine FOXC1 expression in gastric tissues, and the clinical significance of FOXC1 in the development, progression and metastasis of gastric cancer (GC).
METHODS AND RESULTS: We screened GCs for the expression of FOXC1 using the Affymetrix U133 plus 2.0 Gene Chip Array, and found that expression was significantly higher in GC tissues than in controls. Furthermore, we validated the expression levels of FOXC1 using real-time quantitative RT-PCR (qRT-PCR), and of FOXC1 using immunohistochemistry (IHC). Our study showed that expression levels of FOXC1 mRNA and FOXC1 in GC tissues were significantly higher than those in corresponding non-tumour tissues. High FOXC1 expression correlated with the degree of histological differentiation (P < 0.01), TNM stage (P < 0.001), invasive depth (P < 0.05), lymph node metastasis (P < 0.05), and distant metastasis (P < 0.01). Survival analysis revealed that patients with high FOXC1 expression had shorter overall survival than those with low expression (P < 0.001). Multivariate analysis showed that high FOXC1 expression was an independent prognostic factor for GC patients (P < 0.01).
CONCLUSIONS: Overexpression of FOXC1 may play a key role in the progression of GC, and FOXC1 expression may serve as a useful marker for predicting the outcome of patients with GC.

Lubecka-Pietruszewska K, Kaufman-Szymczyk A, Stefanska B, et al.
Clofarabine, a novel adenosine analogue, reactivates DNA methylation-silenced tumour suppressor genes and inhibits cell growth in breast cancer cells.
Eur J Pharmacol. 2014; 723:276-87 [PubMed] Related Publications
Clofarabine (2-chloro-2'-fluoro-2'-deoxyarabinosyladenine, ClF) is a second-generation 2'-deoxyadenosine analogue that is structurally related to cladribine (2-chloro-2'-deoxyadenosine, 2CdA) and fludarabine (9-beta-d-arabinosyl-2-fluoroadenine, F-ara-A). It demonstrates potent antitumour activity at much lower doses than parent compounds with high therapeutic efficacy in paediatric blood cancers. Our previous studies in breast cancer cells indicate that 2CdA and F-ara-A are involved in epigenetic regulation of gene transcription. We therefore investigated whether ClF influences methylation and expression of selected tumour suppressor genes, such as adenomatous polyposis coli (APC), phosphatase and tensin homologue (PTEN), and retinoic acid receptor beta 2 (RARbeta2), as well as expression of p53, p21 and DNA methyltransferase 1 (DNMT1) in MCF-7 and MDA-MB-231 breast cancer cell lines with different invasive potential. Promoter methylation and gene expression were estimated using methylation-sensitive restriction analysis (MSRA) and real-time PCR, respectively. ClF demonstrated potent growth inhibitory activity in MCF-7 and MDA-MB-231 cells after 96h treatment with IC50 determined as equal to 640nM and 50nM, respectively. In both breast cancer cell lines, ClF led to hypomethylation and up-regulation of APC, PTEN and RARbeta2 as well as increase in p21 expression. Only in non-invasive MCF-7 cells, these changes were associated with down-regulation of DNMT1. Our results provide first evidence of ClF implications in epigenetic regulation of transcriptional activity of selected tumour suppressor genes in breast cancer. It seems to be a new important element of ClF anticancer activity and may indicate its potential efficacy in epigenetic therapy of solid tumours, especially at early stages of carcinogenesis.

Nagel S, Ehrentraut S, Meyer C, et al.
Oncogenic deregulation of NKL homeobox gene MSX1 in mantle cell lymphoma.
Leuk Lymphoma. 2014; 55(8):1893-903 [PubMed] Related Publications
NKL homeobox gene MSX1 is physiologically expressed during embryonic hematopoiesis. Here, we detected MSX1 overexpression in three examples of mantle cell lymphoma (MCL) and one of acute myeloid leukemia (AML) by screening 96 leukemia/lymphoma cell lines via microarray profiling. Moreover, in silico analysis identified significant overexpression of MSX1 in 3% each of patients with MCL and AML, confirming aberrant activity in subsets of both types of malignancies. Comparative expression profiling analysis and subsequent functional studies demonstrated overexpression of histone acetyltransferase PHF16 together with transcription factors FOXC1 and HLXB9 as activators of MSX1 transcription. Additionally, we identified regulation of cyclin D1/CCND1 by MSX1 and its repressive cofactor histone H1C. Fluorescence in situ hybridization in MCL cells showed that t(11;14)(q13;q32) results in detachment of CCND1 from its corresponding repressive MSX1 binding site. Taken together, we uncovered regulators and targets of homeobox gene MSX1 in leukemia/lymphoma cells, supporting the view of a recurrent genetic network that is reactivated in malignant transformation.

Li C, Shen W, Shen S, Ai Z
Gene expression patterns combined with bioinformatics analysis identify genes associated with cholangiocarcinoma.
Comput Biol Chem. 2013; 47:192-7 [PubMed] Related Publications
To explore the molecular mechanisms of cholangiocarcinoma (CC), microarray technology was used to find biomarkers for early detection and diagnosis. The gene expression profiles from 6 patients with CC and 5 normal controls were downloaded from Gene Expression Omnibus and compared. As a result, 204 differentially co-expressed genes (DCGs) in CC patients compared to normal controls were identified using a computational bioinformatics analysis. These genes were mainly involved in coenzyme metabolic process, peptidase activity and oxidation reduction. A regulatory network was constructed by mapping the DCGs to known regulation data. Four transcription factors, FOXC1, ZIC2, NKX2-2 and GCGR, were hub nodes in the network. In conclusion, this study provides a set of targets useful for future investigations into molecular biomarker studies.

Klajic J, Fleischer T, Dejeux E, et al.
Quantitative DNA methylation analyses reveal stage dependent DNA methylation and association to clinico-pathological factors in breast tumors.
BMC Cancer. 2013; 13:456 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
BACKGROUND: Aberrant DNA methylation of regulatory genes has frequently been found in human breast cancers and correlated to clinical outcome. In the present study we investigate stage specific changes in the DNA methylation patterns in order to identify valuable markers to understand how these changes affect breast cancer progression.
METHODS: Quantitative DNA methylation analyses of 12 candidate genes ABCB1, BRCCA1, CDKN2A, ESR1, GSTP1, IGF2, MGMT, HMLH1, PPP2R2B, PTEN, RASSF1A and FOXC1 was performed by pyrosequencing a series of 238 breast cancer tissue samples from DCIS to invasive tumors stage I to IV.
RESULTS: Significant differences in methylation levels between the DCIS and invasive stage II tumors were observed for six genes RASSF1A, CDKN2A, MGMT, ABCB1, GSTP1 and FOXC1. RASSF1A, ABCB1 and GSTP1 showed significantly higher methylation levels in late stage compared to the early stage breast carcinoma. Z-score analysis revealed significantly lower methylation levels in DCIS and stage I tumors compared with stage II, III and IV tumors. Methylation levels of PTEN, PPP2R2B, FOXC1, ABCB1 and BRCA1 were lower in tumors harboring TP53 mutations then in tumors with wild type TP53. Z-score analysis showed that TP53 mutated tumors had significantly lower overall methylation levels compared to tumors with wild type TP53. Methylation levels of RASSF1A, PPP2R2B, GSTP1 and FOXC1 were higher in ER positive vs. ER negative tumors and methylation levels of PTEN and CDKN2A were higher in HER2 positive vs. HER2 negative tumors. Z-score analysis also showed that HER2 positive tumors had significantly higher z-scores of methylation compared to the HER2 negative tumors. Univariate survival analysis identifies methylation status of PPP2R2B as significant predictor of overall survival and breast cancer specific survival.
CONCLUSIONS: In the present study we report that the level of aberrant DNA methylation is higher in late stage compared with early stage of invasive breast cancers and DCIS for genes mentioned above.

Bao Y, Ruan LJ, Mo JF
Low trichorhinophalangeal syndrome 1 gene transcript levels in basal-like breast cancer associate with mesenchymal-to-epithelial transition.
Chin Med Sci J. 2013; 28(3):129-34 [PubMed] Related Publications
OBJECTIVE: To investigate trichorhinophalangeal syndrome 1 gene (TRPS-1) expression patterns in different subtypes of breast cancer and its correlations with other genes and survival using microarray data sets.
METHODS: The transcripts of TRPS-1 and its role in survival in breast cancer were analyzed using published microarray data sets#x02014;Netherlands Cancer Institute (NKI) cohort and Wang cohort.
RESULTS: TRPS-1 expression was lower in basal-like breast cancer. The mRNA levels of TRPS-1 negatively correlated with Slug (Pearson correlation coefficient=-0.1366, P=0.0189 in NKI data set and Pearson correlation coefficient=-0.1571, P=0.0078 in Wang data set), FOXC1 (Pearson correlation coefficient=-0.1211, P=0.0376 in NKI data set and Pearson correlation coefficient=-0.1709, P=0.0037 in Wang data set), and CXCL1 (Pearson correlation coefficient=-0.1197, P=0.0399 in NKI data set and Pearson correlation coefficient=-0.3436, P<0.0001 in Wang data set), but positively correlated with BRCA1 (Pearson correlation coefficient=0.1728, P=0.0029 in NKI data set and Pearson correlation coefficient=0.1805, P=0.0022 in Wang data set). Low TRPS-1 expression associated with poor overall survival (hazard ratio 1.79, 95% CI of ratio 0.9894 to 3.238, P=0.054) and relapse-free survival (hazard ratio 1.913, 95% CI of ratio 1.159 to 3.156, P<0.05). The low TRPS-1 mRNA levels predicted poor outcome in breast cancer patients by the 70-gene signature.
CONCLUSION: The strong expression of TRPS-1 may serve as a good prognostic marker in breast cancer.

Li W, Fan D, Yang M, et al.
Cytosine arabinoside promotes cytotoxic effect of T cells on leukemia cells mediated by bispecific antibody.
Hum Gene Ther. 2013; 24(8):751-60 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
Chemotherapeutic drugs can enhance an immune response of the host against the tumor in addition to killing cancer cells by direct cytotoxicity. Therefore, the combination of chemotherapy and immunotherapy is a promising approach for eliminating tumors, particularly in advanced stages. A strategic medication is to use a bispecific antibody format that is capable of recruiting polyclonal T cells around antibody-target-expressing tumor cells. Recently, we have constructed a bispecific antibody, anti-CD3×anti-CD19, in a diabody configuration. In this study, we measured B7 family members B7.1 (CD80) and B7.2 (CD86) expressed on a CD19(+) human leukemia cell line, Nalm-6, stimulated by cytosine arabinoside (Ara-C). We found that a low concentration of Ara-C could upregulate CD80 expressed on CD19(+) Nalm-6 cells. The cytotoxicity of T lymphocytes against Nalm-6 cells in vitro and in vivo mediated by the anti-CD3×anti-CD19 diabody with or without a low dose of Ara-C was compared. The combination of the anti-CD3×anti-CD19 diabody and Ara-C showed the greatest effectiveness in enhancing the cytotoxicity of T cells against the tumor cells in vitro and in vivo. Activated T cells expressed higher levels of CD25 and CD69 and released more interleukin 2. Both perforin/granzyme B system and Fas/FasL pathway were involved in the diabody-induced T-cell cytotoxicity. Moreover, the activated T cells could upregulate ICAM-3 expression on Nalm-6 cells, and inhibition of LFA-1-ICAM-3 interaction impaired cytotoxicity of T cells. It was noted that Ara-C could upregulate CD80 expressed on two of five specimens of acute B lymphoblastic leukemia patient-derived cells. Cytotoxicity of T cells against these two patient-derived cells was enhanced in the presence of the anti-CD3×anti-CD19 diabody. These findings indicate that treatment strategy using both cytotoxic lymphocyte-based immunotherapy and chemotherapy may have synergistic effects.

Caldwell JT, Edwards H, Dombkowski AA, et al.
Overexpression of GATA1 confers resistance to chemotherapy in acute megakaryocytic Leukemia.
PLoS One. 2013; 8(7):e68601 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
It has been previously shown that acute myeloid leukemia (AML) patients with higher levels of GATA1 expression have poorer outcomes. Furthermore, pediatric Down syndrome (DS) patients with acute megakaryocytic leukemia (AMKL), whose blast cells almost universally harbor somatic mutations in exon 2 of the transcription factor gene GATA1, demonstrate increased overall survival relative to non-DS pediatric patients, suggesting a potential role for GATA1 in chemotherapy response. In this study, we confirmed that amongst non-DS patients, GATA1 transcripts were significantly higher in AMKL blasts compared to blasts from other AML subgroups. Further, GATA1 transcript levels significantly correlated with transcript levels for the anti-apoptotic protein Bcl-xL in our patient cohort. ShRNA knockdown of GATA1 in the megakaryocytic cell line Meg-01 resulted in significantly increased cytarabine (ara-C) and daunorubicin anti-proliferative sensitivities and decreased Bcl-xL transcript and protein levels. Chromatin immunoprecipitation (ChIP) and reporter gene assays demonstrated that the Bcl-x gene (which transcribes the Bcl-xL transcripts) is a bona fide GATA1 target gene in AMKL cells. Treatment of the Meg-01 cells with the histone deacetylase inhibitor valproic acid resulted in down-regulation of both GATA1 and Bcl-xL and significantly enhanced ara-C sensitivity. Furthermore, additional GATA1 target genes were identified by oligonucleotide microarray and ChIP-on-Chip analyses. Our findings demonstrate a role for GATA1 in chemotherapy resistance in non-DS AMKL cells, and identified additional GATA1 target genes for future studies.

Lv Y, Zeng L, Zhang G, et al.
Systematic dielectrophoretic analysis of the Ara-C-induced NB4 cell apoptosis combined with gene expression profiling.
Int J Nanomedicine. 2013; 8:2333-50 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
Dielectrophoresis (DEP) can be used to noninvasively measure the dielectric state of the cell, and this data can be used to monitor cell health or apoptosis. In this study, we followed events associated with cytosine arabinoside (Ara-C)-induced apoptosis in NB4 cells using DEP analysis. Our data showed that the membrane capacitance of NB4 cells decreases from 9.42 to 7.63 mF/m(2) in the first 2 hours following treatment with Ara-C, and that this decreased capacitance persists for >12 hours. Additionally, cytoplasmic conductivity decreases from 0.217 to 0.190 S/m within 2 hours of Ara-C treatment; this level is maintained for a short period of time before decreasing. We also investigated these events molecularly at the level of gene expression using microarray analysis and showed that the expression of genes related to membrane capacitance and cytoplasmic conductivity change dramatically as early as 2 hours post-Ara-C treatment, and further demonstrated a temporal relationship between the dielectric properties and key events in apoptosis. This study, integrating physical electrical properties of the cell membrane and cytoplasm with those of conductivity-related gene networks, provides new insights into the molecular mechanisms underlying the initiation of apoptosis, establishing a systematic foundation for DEP application in follow-up drug screening and development of medicines for treating leukemia.

Estey EH
Epigenetics in clinical practice: the examples of azacitidine and decitabine in myelodysplasia and acute myeloid leukemia.
Leukemia. 2013; 27(9):1803-12 [PubMed] Related Publications
Randomized trials have clearly demonstrated that the hypomethylating agents azacitidine and decitabine are more effective than 'best supportive care'(BSC) in reducing transfusion frequency in 'low-risk' myelodysplasia (MDS) and in prolonging survival compared with BSC or low-dose ara-C in 'high-risk' MDS or acute myeloid leukemia (AML) with 21-30% blasts. They also appear equivalent to conventional induction chemotherapy in AML with >20% blasts and as conditioning regimens before allogeneic transplant (hematopoietic cell transplant, HCT) in MDS. Although azacitidine or decitabine are thus the standard to which newer therapies should be compared, here we discuss whether the improvement they afford in overall survival is sufficient to warrant a designation as a standard in treating individual patients. We also discuss pre- and post-treatment covariates, including assays of methylation to predict response, different schedules of administration, combinations with other active agents and use in settings other than active disease, in particular post HCT. We note that rational development of this class of drugs awaits delineation of how much of their undoubted effect in fact results from hypomethylation and reactivation of gene expression.

Cui XY, Skretting G, Jing Y, et al.
Hypoxia influences stem cell-like properties in multidrug resistant K562 leukemic cells.
Blood Cells Mol Dis. 2013; 51(3):177-84 [PubMed] Related Publications
OBJECTIVES: The present study investigates the potential role of hypoxia in maintaining stem cell-like properties and therapeutic resistance in K562 leukemic cell.
METHODS: Western blot, flow cytometry and cell viability assays were used to investigate the effects of hypoxia (1% O2) on cell proliferation, drug resistance and expression of the hypoxia inducible factor-2α (HIF-2α), the octamer-binding transcription factor 4 (Oct4), CD133, CD34 and the ATP-binding cassette sub-family G member 2 (ABCG2) as well as Smad2 phosphorylation in the drug resistant cell line K562/DOX and its parental cell line.
RESULTS: Hypoxia induced growth inhibition and significantly upregulated HIF-2α, CD133, Oct4, CD34 and ABCG2 expression in the wild type K562 cells (p<0.05). The IC50 of doxorubicin was also enhanced about 2.5-fold in hypoxia. In contrast, the K562/DOX cells, which showed significantly higher ABCG2 expression and IC50 for various drugs, no significant difference in cell proliferation was observed between hypoxia and normoxia. The hypoxia-induced upregulation of HIF-2α, CD133, Oct4, CD34 and ABCG2 expression was significantly lower than in the wild type cells (p<0.05). Moreover, hypoxia induced the phosphorylation of Smad2 and additional treatment with SD-208, an inhibitor of the TGF-β receptor I kinase, resulted in a dose-dependent downregulation of CD133 and Oct4 in the K562/DOX cells.
CONCLUSIONS: Hypoxia plays an important role in enhancing the stem cell-like properties and to induce multidrug resistance of leukemia cells. The activation of the TGF-β/Smad2 signaling pathway may be involved in the regulation of this pathophysiological process.

Ara T, Nakata R, Sheard MA, et al.
Critical role of STAT3 in IL-6-mediated drug resistance in human neuroblastoma.
Cancer Res. 2013; 73(13):3852-64 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
Drug resistance is a major cause of treatment failure in cancer. Here, we have evaluated the role of STAT3 in environment-mediated drug resistance (EMDR) in human neuroblastoma. We determined that STAT3 was not constitutively active in most neuroblastoma cell lines but was rapidly activated upon treatment with interleukin (IL)-6 alone and in combination with the soluble IL-6 receptor (sIL-6R). Treatment of neuroblastoma cells with IL-6 protected them from drug-induced apoptosis in a STAT3-dependent manner because the protective effect of IL-6 was abrogated in the presence of a STAT3 inhibitor and upon STAT3 knockdown. STAT3 was necessary for the upregulation of several survival factors such as survivin (BIRC5) and Bcl-xL (BCL2L1) when cells were exposed to IL-6. Importantly, IL-6-mediated STAT3 activation was enhanced by sIL-6R produced by human monocytes, pointing to an important function of monocytes in promoting IL-6-mediated EMDR. Our data also point to the presence of reciprocal activation of STAT3 between tumor cells and bone marrow stromal cells including not only monocytes but also regulatory T cells (Treg) and nonmyeloid stromal cells. Thus, the data identify an IL-6/sIL-6R/STAT3 interactive pathway between neuroblastoma cells and their microenvironment that contributes to drug resistance.

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