Gene Summary

Gene:POU2F1; POU class 2 homeobox 1
Aliases: OCT1, OTF1, oct-1B
Summary:The OCT1 transcription factor was among the first identified members of the POU transcription factor family (summarized by Sturm et al., 1993 [PubMed 8314572]). Members of this family contain the POU domain, a 160-amino acid region necessary for DNA binding to the octameric sequence ATGCAAAT.[supplied by OMIM, Jul 2010]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:POU domain, class 2, transcription factor 1
Source:NCBIAccessed: 25 June, 2015


What does this gene/protein do?
Show (12)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 25 June 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.

  • Base Sequence
  • Chronic Myelogenous Leukemia
  • Proteins
  • DNA-Binding Proteins
  • Cervical Cancer
  • Cancer DNA
  • Messenger RNA
  • Molecular Sequence Data
  • HeLa Cells
  • P-Glycoprotein
  • Octamer Transcription Factor-2
  • Mutation
  • Transcription Factors
  • Binding Sites
  • Transcription
  • Pyrimidines
  • Transfection
  • Oligonucleotide Probes
  • Nucleic Acid Regulatory Sequences
  • Fusion Proteins, bcr-abl
  • Promoter Regions
  • Breast Cancer
  • Consensus Sequence
  • Repressor Proteins
  • NF-kappa B
  • Host Cell Factor C1
  • Cell Line
  • Chromosome 1
  • Benzamides
  • ATP-Binding Cassette Transporters
  • Young Adult
  • Piperazines
  • B-Lymphocytes
  • Antineoplastic Agents
  • Neoplasm Proteins
  • Single Nucleotide Polymorphism
  • Octamer Transcription Factor-1
  • P-Glycoproteins
  • Cancer Gene Expression Regulation
Tag cloud generated 25 June, 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: POU2F1 (cancer-related)

Kalamohan K, Periasamy J, Bhaskar Rao D, et al.
Transcriptional coexpression network reveals the involvement of varying stem cell features with different dysregulations in different gastric cancer subtypes.
Mol Oncol. 2014; 8(7):1306-25 [PubMed] Related Publications
Despite the advancements in the cancer therapeutics, gastric cancer ranks as the second most common cancers with high global mortality rate. Integrative functional genomic investigation is a powerful approach to understand the major dysregulations and to identify the potential targets toward the development of targeted therapeutics for various cancers. Intestinal and diffuse type gastric tumors remain the major subtypes and the molecular determinants and drivers of these distinct subtypes remain unidentified. In this investigation, by exploring the network of gene coexpression association in gastric tumors, mRNA expressions of 20,318 genes across 200 gastric tumors were categorized into 21 modules. The genes and the hub genes of the modules show gastric cancer subtype specific expression. The expression patterns of the modules were correlated with intestinal and diffuse subtypes as well as with the differentiation status of gastric tumors. Among these, G1 module has been identified as a major driving force of diffuse type gastric tumors with the features of (i) enriched mesenchymal, mesenchymal stem cell like, and mesenchymal derived multiple lineages, (ii) elevated OCT1 mediated transcription, (iii) involvement of Notch activation, and (iv) reduced polycomb mediated epigenetic repression. G13 module has been identified as key factor in intestinal type gastric tumors and found to have the characteristic features of (i) involvement of embryonic stem cell like properties, (ii) Wnt, MYC and E2F mediated transcription programs, and (iii) involvement of polycomb mediated repression. Thus the differential transcription programs, differential epigenetic regulation and varying stem cell features involved in two major subtypes of gastric cancer were delineated by exploring the gene coexpression network. The identified subtype specific dysregulations could be optimally employed in developing subtype specific therapeutic targeting strategies for gastric cancer.

Zhou Y, Liu X, Xu L, et al.
Transcriptional repression of plasma cell differentiation is orchestrated by aberrant over-expression of the ETS factor SPIB in Waldenström macroglobulinaemia.
Br J Haematol. 2014; 166(5):677-89 [PubMed] Related Publications
In Waldenström macroglobulinaemia (WM), the mechanism(s) responsible for repression of B-cell differentiation remains unknown. We found that expression of SPIB and ID2 were significantly increased and decreased, respectively, in WM lymphoplasmacytic cells (LPC). Ectopic expression of SPIB in healthy donor CD19(+) cells inhibited plasmacytic differentiation in conjunction with decreased transcription of IRF4 and XBP1 spliced form. In primary WM LPC, knock-down of SPIB induced plasmacytic differentiation in conjunction with increased transcription of PRDM1, XBP1 spliced form, IRF4 and ID2. Knock-down of SPIB also led to decreased BCL2 expression. Given that SPIB is a direct target of POU2AF1 (OBF1) in complex with POU2F2 or POU2F1, we next examined their expression in WM LPC. POU2F2 transcription, as well as POU2F2 and POU2AF1 protein expression was higher in WM LPC. Ectopic expression of POU2F2 in healthy donor CD19(+) cells induced transcription of SPIB and suppressed transcription of PRDM1 and IRF4. Chromatin immunoprecipitation analysis in BCWM.1 WM cells confirmed binding of POU2F2 and POU2AF1 in SPIB and ID2 promoters. These findings establish a molecular hierarchy among POU2F2, SPIB and ID2 during B-cell differentiation, and suggest that aberrant expression of these transcription factors plays an important role in arresting plasmacytic differentiation in WM.

Schweighofer N, Lerchbaum E, Trummer O, et al.
Metformin resistance alleles in polycystic ovary syndrome: pattern and association with glucose metabolism.
Pharmacogenomics. 2014; 15(3):305-17 [PubMed] Related Publications
Insulin-sensitizer treatment with metformin is common in polycystic ovary syndrome (PCOS). OCT alleles were investigated in PCOS patients to identify genetic 'bad responders' and 'nonresponders' to metformin including their possible effects on glucose metabolism without treatment. We genotyped eight SNPs in OCT1, OCT2 and ATM genes in 676 women with PCOS and 90 control women, we also measured oral glucose tolerance tests prior to treatment. Nonfunctional alleles were present in 29.8% and low-functional alleles in 57.9% of our PCOS cohort. OCT variants were significantly associated with elevated baseline and glucose-induced C-peptide levels in PCOS. Metformin bad responders or nonresponders based on OCT genotypes might be relevant in clinical practice - their modulation of metformin pharmacokinetics and pharmacodynamics and metformin-independent glucose effects remain to be elucidated.

Nies AT, Schaeffeler E, van der Kuip H, et al.
Cellular uptake of imatinib into leukemic cells is independent of human organic cation transporter 1 (OCT1).
Clin Cancer Res. 2014; 20(4):985-94 [PubMed] Free Access to Full Article Related Publications
PURPOSE: In addition to mutated BCR-ABL1 kinase, the organic cation transporter 1 (OCT1, encoded by SLC22A1) has been considered to contribute to imatinib resistance in patients with chronic myeloid leukemia (CML). As data are conflicting as to whether OCT1 transports imatinib and may serve as a clinical biomarker, we used a combination of different approaches including animal experiments to elucidate comprehensively the impact of OCT1 on cellular imatinib uptake.
EXPERIMENTAL DESIGN: Transport of imatinib was studied using OCT1-expressing Xenopus oocytes, mammalian cell lines (HEK293, MDCK, V79) stably expressing OCT1, human leukemic cells, and Oct1-knockout mice. OCT1 mRNA and protein expression were analyzed in leukemic cells from patients with imatinib-naïve CML as well as in cell lines.
RESULTS: Transport and inhibition studies showed that overexpression of functional OCT1 protein in Xenopus oocytes or mammalian cell lines did not lead to an increased cellular accumulation of imatinib. The CML cell lines (K562, Meg-01, LAMA84) and leukemic cells from patients expressed neither OCT1 mRNA nor protein as demonstrated by immunoblotting and immunofluorescence microscopy, yet they showed a considerable imatinib uptake. Oct1 deficiency in mice had no influence on plasma and hepatic imatinib concentrations.
CONCLUSIONS: These data clearly demonstrate that cellular uptake of imatinib is independent of OCT1, and therefore OCT1 is apparently not a valid biomarker for imatinib resistance.

Koren-Michowitz M, Buzaglo Z, Ribakovsky E, et al.
OCT1 genetic variants are associated with long term outcomes in imatinib treated chronic myeloid leukemia patients.
Eur J Haematol. 2014; 92(4):283-8 [PubMed] Related Publications
OBJECTIVES: One third of CML patients treated with first line imatinib have suboptimal responses or treatment failures with increased risk for disease progression. Imatinib is actively transported into cells by the SLC22A1 transporter (hOCT1) and its genetic variants may affect intracellular drug import. We studied the effect of SLC22A1 genetic variants on long-term outcomes of imatinib treated patients.
METHODS: A total of 167 patients, 94% in chronic phase, were analyzed for rs41267797, rs683369, rs12208357, and rs628031 variants using the Sequenom MassARRAY platform.
RESULTS: Rates of CHR, MCyR, CCyR, and MMolR were not significantly different according to allelic variants. However, patients with AA or GA rs628031 genotypes had a higher incidence of poor response to imatinib compared to the GG genotype (47% compared to 29%, P = 0.06), and a higher rate of KD mutation discovery (8/16 vs. 5/27, P = 0.04), suggesting that secondary resistance was more common in these genotypes. Median EFS was shorter for rs628031 genotype AA/AG compared with the GG genotype (61 months and not reached, respectively, P = 0.05), and 5 yr OS rates were lower for patients with the rs628031 genotypes AA/AG compared with the GG genotype (88% and 97%, respectively, P = 0.03). Patients with AA/GA rs628031 and additional rare genotypes had worse EFS and OS compared to patients with only AA/GA rs628031 (P = 0.02 for EFS and 0.01 for OS). There was no difference in pretreatment SLC22A1 mRNA expression levels in patients with rs628031 genotypes GG/AA or GA.
CONCLUSIONS: Studying SLC22A1 genetic variants prior to TKI initiation could influence treatment decisions.

Berstein LM, Iyevleva AG, Vasilyev D, et al.
Genetic polymorphisms potentially associated with response to metformin in postmenopausal diabetics suffering and not suffering with cancer.
Cell Cycle. 2013; 12(23):3681-8 [PubMed] Free Access to Full Article Related Publications
Metformin is a well-known antidiabetic medication, which, besides diabetes, may be involved into modulation of other age-related pathologies, including cancer. The study concerns 12 gene polymorphisms divided into 2 groups consisting of 6 genes each. The first group was composed from so-called "standard" (S) polymorphisms, for which the connection with metabolic response to metformin is already established. The second group included polymorphisms of genes encoding proteins possibly connected with diabetes mellitus type 2 (DM2), impaired glucose tolerance or cancer and entitled here as "associated" (A). A total of 156 postmenopausal women (average age 60.7 ± 0.7) were included, 37 of them healthy, 64 with type DM2 and concurrent treatment-naïve cancer (mostly breast, endometrial or colorectal cancer), 32 with DM2 without cancer, and 23 with treatment-naïve cancer and normal glucose tolerance. The leading metformin response S-marker in combined group of DM2 patients was the CC variant of OCT1-R61C polymorphism of organic cation transporter protein 1 gene. In cancer patients without DM2, this position belonged to AC and AA genotypes of OCT1_rs622342 polymorphism. Among the A-polymorphisms, GA variant of sex hormone-binding globulin gene SHBG_D356N was less frequently observed in DM2 patients with or without cancer. Besides, in diabetics, the same polymorphic variant of SHBG as well as GC genotype of oxidized lipoprotein receptor OLR1_G501C and GG genotype of locus rs11065987 near BRAP gene were carried rather often in combination with "metformin-positive" variant of OCT1_R61C. In addition, carriers of OCT1_R61C and OCT1_rs622342 polymorphisms with potentially positive reaction to metformin had higher insulin resistance score (HOMA-IR) values. Received data lead to the conclusion that postmenopausal diabetics, both with and without cancer, differ in genetic stigmata of potential response to metformin less than they differ from cancer patients without DM2. As genetic polymorphisms associated with metabolic and anticancer metformin (and, possibly, phenformin) effects may be different, this subject requires further investigation.

Perri A, Catalano S, Bonofiglio D, et al.
T3 enhances thyroid cancer cell proliferation through TRβ1/Oct-1-mediated cyclin D1 activation.
Mol Cell Endocrinol. 2014; 382(1):205-17 [PubMed] Related Publications
Several studies have demonstrated that thyroid hormone T3 promotes cancer cell growth, even though the molecular mechanism involved in such processes still needs to be elucidated. In this study we demonstrated that T3 induced proliferation in papillary thyroid carcinoma cell lines concomitantly with an up-regulation of cyclin D1 expression, that is a critical mitogen-regulated cell-cycle control element. Our data revealed that T3 enhanced the recruitment of the TRβ1/Oct-1 complex on Octamer-transcription factor-1 site within cyclin D1 promoter, leading to its transactivation. In addition, silencing of TRβ1 or Oct-1 expression by RNA interference reversed both increased cell proliferation and up-regulation of cyclin D1, underlying the important role of both transcriptional factors in mediating these effects. Finally, T3-induced increase in cell growth was abrogated after knocking down cyclin D1 expression. All these findings highlight a new molecular mechanism by which T3 promotes thyroid cancer cell growth.

Grinfeld J, Gerrard G, Alikian M, et al.
A common novel splice variant of SLC22A1 (OCT1) is associated with impaired responses to imatinib in patients with chronic myeloid leukaemia.
Br J Haematol. 2013; 163(5):631-9 [PubMed] Related Publications
Approximately one-third of patients with chronic myeloid leukaemia will fail to achieve or maintain responses to imatinib. Changes in solute carrier family 22 (organic cation transporter), member 1 (SLC22A1, also termed OCT1), the main transporter for imatinib, have been proposed as a possible predictive factor. We analysed SLC22A1 mRNA levels and single nucleotide polymorphisms (SNPs) located in exon 7 in 153 diagnostic whole blood samples from two patient cohorts. The level of SLC22A1 expression did not significantly correlate with imatinib failure or achievement of molecular remission. The SNP 408V>M (g.1222G>A) was present in 65% of patients and was associated in all cases with an eight base-pair insertion (8(+) allele) at the 3' end of exon 7. The latter generates an alternative splice site, leading to a premature stop codon. M420del was found in 33% of patients and never in cis with 8(+) (the 3(-) allele). Significantly longer times to 1% and 0·1% molecular responses (by quantitative reverse transcription polymerase chain reaction) were seen in patients with 8(+) 8(+) or 8(+) N compared to those with the remaining four genotypes (N = no insertion or deletion). Patients lacking 8(+) and 3(-) (NN, 18%) showed the best outcomes overall. Thus, while SLC22A1 expression does not appear to affect response, alterations in its splicing or amino acid sequence may do so.

Rumjanek VM, Vidal RS, Maia RC
Multidrug resistance in chronic myeloid leukaemia: how much can we learn from MDR-CML cell lines?
Biosci Rep. 2013; 33(6) [PubMed] Free Access to Full Article Related Publications
The hallmark of CML (chronic myeloid leukaemia) is the BCR (breakpoint cluster region)-ABL fusion gene. CML evolves through three phases, based on both clinical and pathological features: a chronic phase, an accelerated phase and blast crisis. TKI (tyrosine kinase inhibitors) are the treatment modality for patients with chronic phase CML. The therapeutic potential of the TKI imatinib is affected by BCR-ABL dependent an independent mechanisms. Development of MDR (multidrug resistance) contributes to the overall clinical resistance. MDR involves overexpression of ABC -transporters (ATP-binding-cassette transporter) among other features. MDR studies include the analysis of cancer cell lines selected for resistance. CML blast crisis is accompanied by increased resistance to apoptosis. This work reviews the role played by the influx transporter OCT1 (organic cation transporter 1), by efflux ABC transporters, molecules involved in the modulation of apoptosis (p53, Bcl-2 family, CD95, IAPs (inhibitors of apoptosis protein)], Hh and Wnt/β-catenin pathways, cytoskeleton abnormalities and other features described in leukaemic cells of clinical samples and CML cell lines. An MDR cell line, Lucena-1, generated from K562 by stepwise exposure to vincristine, was used as our model and some potential anticancer drugs effective against the MDR cell line and patients' samples are presented.

Hwang-Verslues WW, Chang PH, Jeng YM, et al.
Loss of corepressor PER2 under hypoxia up-regulates OCT1-mediated EMT gene expression and enhances tumor malignancy.
Proc Natl Acad Sci U S A. 2013; 110(30):12331-6 [PubMed] Free Access to Full Article Related Publications
The circadian clock gene Period2 (PER2) has been suggested to be a tumor suppressor. However, detailed mechanistic evidence has not been provided to support this hypothesis. We found that loss of PER2 enhanced invasion and activated expression of epithelial-mesenchymal transition (EMT) genes including TWIST1, SLUG, and SNAIL. This finding was corroborated by clinical observation that PER2 down-regulation was associated with poor prognosis in breast cancer patients. We further demonstrated that PER2 served as a transcriptional corepressor, which recruited polycomb proteins EZH2 and SUZ12 as well as HDAC2 to octamer transcription factor 1 (OCT1) (POU2F1) binding sites of the TWIST1 and SLUG promoters to repress expression of these EMT genes. Hypoxia, a condition commonly observed in tumors, caused PER2 degradation and disrupted the PER2 repressor complex, leading to activation of EMT gene expression. This result was further supported by clinical data showing a significant negative correlation between hypoxia and PER2. Thus, our findings clearly demonstrate the tumor suppression function of PER2 and elucidate a pathway by which hypoxia promotes EMT via degradation of PER2.

Reimand J, Bader GD
Systematic analysis of somatic mutations in phosphorylation signaling predicts novel cancer drivers.
Mol Syst Biol. 2013; 9:637 [PubMed] Free Access to Full Article Related Publications
Large-scale cancer genome sequencing has uncovered thousands of gene mutations, but distinguishing tumor driver genes from functionally neutral passenger mutations is a major challenge. We analyzed 800 cancer genomes of eight types to find single-nucleotide variants (SNVs) that precisely target phosphorylation machinery, important in cancer development and drug targeting. Assuming that cancer-related biological systems involve unexpectedly frequent mutations, we used novel algorithms to identify genes with significant phosphorylation-associated SNVs (pSNVs), phospho-mutated pathways, kinase networks, drug targets, and clinically correlated signaling modules. We highlight increased survival of patients with TP53 pSNVs, hierarchically organized cancer kinase modules, a novel pSNV in EGFR, and an immune-related network of pSNVs that correlates with prolonged survival in ovarian cancer. Our findings include multiple actionable cancer gene candidates (FLNB, GRM1, POU2F1), protein complexes (HCF1, ASF1), and kinases (PRKCZ). This study demonstrates new ways of interpreting cancer genomes and presents new leads for cancer research.

Perets R, Kaplan T, Stein I, et al.
Genome-wide analysis of androgen receptor targets reveals COUP-TF1 as a novel player in human prostate cancer.
PLoS One. 2012; 7(10):e46467 [PubMed] Free Access to Full Article Related Publications
Androgen activity plays a key role in prostate cancer progression. Androgen receptor (AR) is the main mediator of androgen activity in the prostate, through its ability to act as a transcription mediator. Here we performed a genome-wide analysis of human AR binding to promoters in the presence of an agonist or antagonist in an androgen dependent prostate cancer cell line. Many of the AR bound promoters are bound in all examined conditions while others are bound only in the presence of an agonist or antagonist. Several motifs are enriched in AR bound promoters, including the AR Response Element (ARE) half-site and recognition elements for the transcription factors OCT1 and SOX9. This suggests that these 3 factors could define a module of co-operating transcription factors in the prostate. Interestingly, AR bound promoters are preferentially located in AT rich genomic regions. Analysis of mRNA expression identified chicken ovalbumin upstream promoter-transcription factor 1 (COUP-TF1) as a direct AR target gene that is downregulated upon binding by the agonist liganded AR. COUP-TF1 immunostaining revealed nucleolar localization of COUP-TF1 in epithelium of human androgen dependent prostate cancer, but not in adjacent benign prostate epithelium. Stromal cells both in human and mouse prostate show nuclear COUP-TF1 staining. We further show that there is an inverse correlation between COUP-TF1 expression in prostate stromal cells and the rising levels of androgen with advancing puberty. This study extends the pool of recognized putative AR targets and identifies a negatively regulated target of AR - COUP-TF1 - which could possibly play a role in human prostate cancer.

Lin R, Li X, Li J, et al.
Long-term cisplatin exposure promotes methylation of the OCT1 gene in human esophageal cancer cells.
Dig Dis Sci. 2013; 58(3):694-8 [PubMed] Related Publications
BACKGROUND: Cisplatin-based chemotherapy is widely used for treatment of a variety of human malignant solid and metastatic tumors, including esophageal cancer. However, the clinical effect of this drug is limited because of intrinsic and acquired resistance to it. Organic cation transporters (OCTs) are important in the cellular uptake of cisplatin.
AIM: Our objective was to test the hypothesis that cisplatin resistance is associated with alteration of expression of OCTs.
METHODS: Levels of expression of OCTs in paired esophageal cancer and adjacent non-cancerous tissues were examined by use of immunohistochemistry.
RESULTS: We found that OCT1 silencing impaired cisplatin-mediated apoptosis of esophageal cancer cells. The level of OCT1 mRNA in cisplatin-resistant cells was markedly reduced compared with parental cells. Promoter methylation of OCT1 was induced in cisplatin-resistant cells.
CONCLUSION: This study shows that long-term exposure to cisplatin promotes methylation of the OCT1 gene in human esophageal cancer cells, which in turn results in cisplatin resistance.

Lu H, Hallstrom TC
Sensitivity to TOP2 targeting chemotherapeutics is regulated by Oct1 and FILIP1L.
PLoS One. 2012; 7(8):e42921 [PubMed] Free Access to Full Article Related Publications
Topoisomerase II (TOP2) targeting drugs like doxorubicin and etoposide are frontline chemotherapeutics for a wide variety of solid and hematological malignancies, including breast and ovarian adenocarcinomas, lung cancers, soft tissue sarcomas, leukemias and lymphomas. These agents cause a block in DNA replication leading to a pronounced DNA damage response and initiation of apoptotic programs. Resistance to these agents is common, however, and elucidation of the mechanisms causing resistance to therapy could shed light on strategies to reduce the frequency of ineffective treatments. To explore these mechanisms, we utilized an unbiased shRNA screen to identify genes that regulate cell death in response to doxorubicin treatment. We identified the Filamin A interacting protein 1-like (FILIP1L) gene as a crucial mediator of apoptosis triggered by doxorubicin. FILIP1L shares significant similarity with bacterial SbcC, an ATPase involved in DNA repair. FILIP1L was originally described as DOC1, or "down-regulated in ovarian cancer" and has since been shown to be downregulated in a wide variety of human tumors. FILIP1L levels increase markedly through transcriptional mechanisms following treatment with doxorubicin and other TOP2 poisons, including etoposide and mitoxantrone, but not by the TOP2 catalytic inhibitors merbarone or dexrazoxane (ICRF187), or by UV irradiation. This induction requires the action of the OCT1 transcription factor, which relocalizes to the FILIP1L promoter and facilitates its expression following doxorubicin treatment. Our findings suggest that the FILIP1L expression status in tumors may influence the response to anti-TOP2 chemotherapeutics.

Wang L, Giannoudis A, Austin G, Clark RE
Peroxisome proliferator-activated receptor activation increases imatinib uptake and killing of chronic myeloid leukemia cells.
Exp Hematol. 2012; 40(10):811-9.e2 [PubMed] Related Publications
Low pretreatment expression of the imatinib uptake transporter human organic cation transporter 1 (hOCT1) is associated with inferior complete cytogenetic response rates, progression-free survival, and overall survival in imatinib-treated chronic myeloid leukemia (CML). Upregulation of hOCT1 can therefore increase the uptake of imatinib. The hOCT1 gene is transactivated by hepatocyte nuclear factor 4α in human liver, and peroxisome proliferator-activated receptors (PPAR) α and γ activation increases OCT1 expression in mouse hepatocytes. Here we report that no isoform of hepatocyte nuclear factor 4α is expressed in CML lines or in CML primary cells. In contrast, both PPARα and γ were expressed in all CML cell lines and primary cells studied. PPARα agonist treatment increased imatinib killing of CML KCL22 cells and primitive CD34(+) cells, and also upregulates hOCT1 gene expression and increases imatinib uptake into KCL22 cells and primary cells. PPARα agonists might potentially be of clinical use in CML patients failing imatinib.

Ciarimboli G, Lancaster CS, Schlatter E, et al.
Proximal tubular secretion of creatinine by organic cation transporter OCT2 in cancer patients.
Clin Cancer Res. 2012; 18(4):1101-8 [PubMed] Free Access to Full Article Related Publications
PURPOSE: Knowledge of transporters responsible for the renal secretion of creatinine is key to a proper interpretation of serum creatinine and/or creatinine clearance as markers of renal function in cancer patients receiving chemotherapeutic agents.
EXPERIMENTAL DESIGN: Creatinine transport was studied in transfected HEK293 cells in vitro and in wild-type mice and age-matched organic cation transporter 1 and 2-deficient [Oct1/2(-/-)] mice ex vivo and in vivo. Clinical pharmacogenetic and transport inhibition studies were done in two separate cohorts of cancer patients.
RESULTS: Compared with wild-type mice, creatinine clearance was significantly impaired in Oct1/2(-/-) mice. Furthermore, creatinine inhibited organic cation transport in freshly isolated proximal tubules from wild-type mice and humans, but not in those from Oct1/2(-/-) mice. In a genetic association analysis (n = 590), several polymorphisms around the OCT2/SLC22A2 gene locus, including rs2504954 (P = 0.000873), were significantly associated with age-adjusted creatinine levels. Furthermore, in cancer patients (n = 68), the OCT2 substrate cisplatin caused an acute elevation of serum creatinine (P = 0.0083), consistent with inhibition of an elimination pathway.
CONCLUSIONS: Collectively, this study shows that OCT2 plays a decisive role in the renal secretion of creatinine. This process can be inhibited by OCT2 substrates, which impair the usefulness of creatinine as a marker of renal function.

Gupta S, Wulf G, Henjakovic M, et al.
Human organic cation transporter 1 is expressed in lymphoma cells and increases susceptibility to irinotecan and paclitaxel.
J Pharmacol Exp Ther. 2012; 341(1):16-23 [PubMed] Related Publications
Antineoplastic agents directed at nuclear and cytoplasmic targets in tumor cells represent the current mainstay of treatment for patients with disseminated malignant diseases. Cellular uptake of antineoplastics is a prerequisite for their efficacy. Five of six lymphoma cell lines as well as primary samples from chronic lymphocytic leukemia patients demonstrated significant expression of SLC22A1 mRNA coding for organic cation transporter 1 (OCT1). Functionally, the antineoplastic agents irinotecan, mitoxantrone, and paclitaxel inhibited the uptake of the organic cation [(3)H]1-methyl-4-pyridinium iodide into OCT1-transfected Chinese hamster ovary model cells, with K(i) values of 1.7, 85, and 50 μM, respectively. Correspondingly, OCT1-positive cell lines and transfectants exhibited significantly higher susceptibilities to the cytotoxic effects of irinotecan and paclitaxel compared with those of OCT1-negative controls. We hypothesize that OCT1 can contribute to the susceptibility of cancer cells to selected antineoplastic drugs. In the future, an expression analysis of the transporters and the application of transporter-specific antineoplastic agents could help to tailor cancer therapy.

Takaoka N, Takayama T, Teratani T, et al.
Analysis of the regulation of fatty acid binding protein 7 expression in human renal carcinoma cell lines.
BMC Mol Biol. 2011; 12:31 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Improving the treatment of renal cell carcinoma (RCC) will depend on the development of better biomarkers for predicting disease progression and aiding the design of appropriate therapies. One such marker may be fatty acid binding protein 7 (FABP7), also known as B-FABP and BLBP, which is expressed normally in radial glial cells of the developing central nervous system and cells of the mammary gland. Melanomas, glioblastomas, and several types of carcinomas, including RCC, overexpress FABP7. The abundant expression of FABP7 in primary RCCs compared to certain RCC-derived cell lines may allow the definition of the molecular components of FABP7's regulatory system.
RESULTS: We determined FABP7 mRNA levels in six RCC cell lines. Two were highly expressed, whereas the other and the embryonic kidney cell line (HEK293) were weakly expressed FABP7 transcripts. Western blot analysis of the cell lines detected strong FABP7 expression only in one RCC cell line. Promoter activity in the RCC cell lines was 3- to 21-fold higher than that of HEK293. Deletion analysis demonstrated that three FABP7 promoter regions contributed to upregulated expression in RCC cell lines, but not in the HEK293 cell. Competition analysis of gel shifts indicated that OCT1, OCT6, and nuclear factor I (NFI) bound to the FABP7 promoter region. Supershift experiments indicated that BRN2 (POU3F2) and NFI bound to the FABP7 promoter region as well. There was an inverse correlation between FABP7 promoter activity and BRN2 mRNA expression. The FABP7-positive cell line's NFI-DNA complex migrated faster than in other cell lines. Levels of NFIA mRNA were higher in the HEK293 cell line than in any of the six RCC cell lines. In contrast, NFIC mRNA expression was lower in the HEK293 cell line than in the six RCC cell lines.
CONCLUSIONS: Three putative FABP7 promoter regions drive reporter gene expression in RCC cell lines, but not in the HEK293 cell line. BRN2 and NFI may be key factors regulating the expression of FABP7 in certain RCC-derived cell lines.

Shukla V, Coumoul X, Lahusen T, et al.
BRCA1 affects global DNA methylation through regulation of DNMT1.
Cell Res. 2010; 20(11):1201-15 [PubMed] Related Publications
Global DNA hypomethylation at CpG islands coupled with local hypermethylation is a hallmark for breast cancer, yet the mechanism underlying this change remains elusive. In this study, we showed that DNMT1, which encodes a methylation maintenance enzyme, is a transcriptional target of BRCA1. BRCA1 binds to the promoter of the DNMT1 gene through a potential OCT1 site and the binding is required for maintaining a transcriptional active configuration of the promoter in both mouse and human cells. We further demonstrated that impaired function of BRCA1 leads to global DNA hypomethylation, loss of genomic imprinting, and an open chromatin configuration in several types of tissues examined in a BRCA1 mutant mouse model at premaligant stages. BRCA1 deficiency is also associated with significantly increased expression levels of several protooncogenes, including c-Fos, Ha-Ras, and c-Myc, with a higher expression in tumors, while premalignant mammary epithelial cells displayed an intermediate state between tumors and controls. In human clinical samples, reduced expression of BRCA1 correlates with decreased levels of DNMT1, and reduced methylation of CpG islands. Thus, BRCA1 prevents global DNA hypomethylation through positively regulating DNMT1 expression, and this provides one of mechanisms for BRCA1-associated breast cancer formation.

Zhu X, Wu L, Zhang L, et al.
Distinct regulatory mechanism of immunoglobulin gene transcription in epithelial cancer cells.
Cell Mol Immunol. 2010; 7(4):279-86 [PubMed] Free Access to Full Article Related Publications
The restriction of immunoglobulin (Ig) expression to B lymphocytes is well established. However, several reports have confirmed that the Ig gene can be expressed in many non-B cancer cells and/or some normal cells. Our aim is to determine whether the Ig gene promoter can be activated in non-B cancer cells and to identify the regulatory mechanism for Ig gene expression. Our results show that the Ig promoter of VH4-59 was activated in several non-B cancer cell lines. Moreover, two novel positive regulatory elements, an enhancer-like element at -800 to -610 bp and a copromoter-like element at -610 to -300 bp, were identified in two epithelial cancer cell lines, HeLa S3 and HT-29. The octamer element (5'-ATGCAAAT-3') located in the Ig promoter, a crucial element for B-cell-derived Ig gene transcription, was also very important for non-B-cell-derived Ig gene transcription. More importantly, we confirmed that octamer-related protein-1 (Oct-1), but not Oct-2, was a crucial transcriptional factor for Ig gene transcription due to its ability to bind to the octamer element of the Ig promoter in epithelial cancer cells. These results suggested the presence of a distinct regulatory mechanism for Ig gene expression in non-B cancer cells.

Marin D, Bazeos A, Mahon FX, et al.
Adherence is the critical factor for achieving molecular responses in patients with chronic myeloid leukemia who achieve complete cytogenetic responses on imatinib.
J Clin Oncol. 2010; 28(14):2381-8 [PubMed] Related Publications
PURPOSE: There is a considerable variability in the level of molecular responses achieved with imatinib therapy in patients with chronic myeloid leukemia (CML). These differences could result from variable therapy adherence.
METHODS: Eighty-seven patients with chronic-phase CML treated with imatinib 400 mg/d for a median of 59.7 months (range, 25 to 104 months) who had achieved complete cytogenetic response had adherence monitored during a 3-month period by using a microelectronic monitoring device. Adherence was correlated with levels of molecular response. Other factors that could influence outcome were also analyzed.
RESULTS: Median adherence rate was 98% (range, 24% to 104%). Twenty-three patients (26.4%) had adherence 90%) and the 6-year probability of a 3-log reduction (also known as major molecular response [MMR]) in BCR-ABL1 transcripts (28.4% v 94.5%; P < .001) and also complete molecular response (CMR; 0% v 43.8%; P = .002). Multivariate analysis identified adherence (relative risk [RR], 11.7; P = .001) and expression of the molecular human organic cation transporter-1 (RR, 1.79; P = .038) as the only independent predictors for MMR. Adherence was the only independent predictor for CMR. No molecular responses were observed when adherence was CONCLUSION: In patients with CML treated with imatinib for some years, poor adherence may be the predominant reason for inability to obtain adequate molecular responses.

More SS, Li S, Yee SW, et al.
Organic cation transporters modulate the uptake and cytotoxicity of picoplatin, a third-generation platinum analogue.
Mol Cancer Ther. 2010; 9(4):1058-69 [PubMed] Free Access to Full Article Related Publications
Picoplatin, a third-generation platinum agent, is efficacious against lung cancers that are otherwise resistant or become refractory during platinum treatment. This effort was aimed at the determination of the influence of organic cation transporters 1, 2, and 3 (OCT1, OCT2, and OCT3) and their genetic variants on cellular uptake of picoplatin and on the individual components of the ensuing cytotoxicity such as DNA adduct formation. The effect of OCT1 on picoplatin pharmacokinetics and antitumor efficacy was determined using OCT knockout mice and HEK293 xenografts stably expressing OCT1. The uptake and DNA adduct formation of picoplatin were found to be significantly enhanced by the expression of the OCTs. Expression of OCT1 and OCT2, but not OCT3, significantly enhanced picoplatin cytotoxicity, which was reduced in the presence of an OCT inhibitor. Common reduced functional variants of OCT1 and OCT2 led to reduction in uptake and DNA adduct formation of picoplatin in comparison with the reference OCT1 and OCT2. Pharmacokinetic parameters of picoplatin in Oct1(-/-) and Oct1(+/+) mice were not significantly different, suggesting that the transporters do not influence the disposition of the drug. In contrast, the volume of OCT1-expressing xenografts in mice was significantly reduced by picoplatin treatment, suggesting that OCT1 may enhance the antitumor efficacy of picoplatin. These studies provide a basis for follow-up clinical studies that would seek to examine the relationship between the anticancer efficacy of picoplatin and expression levels of OCTs and their genetic variants in tumors. Mol Cancer Ther; 9(4); 1058-69. (c)2010 AACR.

Galetti M, Alfieri RR, Cavazzoni A, et al.
Functional characterization of gefitinib uptake in non-small cell lung cancer cell lines.
Biochem Pharmacol. 2010; 80(2):179-87 [PubMed] Related Publications
Gefitinib, an inhibitor of epidermal growth factor receptor tyrosine kinase, has been developed and approved for treatment of advanced non-small cell lung cancer (NSCLC). In this study, we investigated the uptake of gefitinib in gefitinib-sensitive and -resistant NSCLC cell lines. The transport system was temperature-dependent, indicative of an active process and sodium- and potential-independent. Moreover, high cell densities and low extracellular pH significantly reduced the uptake of gefitinib. Inhibitors of the human organic cation transporter 1 (hOCT1) significantly decreased gefitinib uptake; however, gefitinib was not a substrate for hOCT1 or hOCT2 in overexpressing HEK293 cells. Interestingly, gefitinib significantly reduced uptake of the hOCT prototypical substrate MPP suggesting that gefitinib may exert an inhibitory effect on the intracellular accumulation of drugs transported by hOCT1 and hOCT2. After 15min of treatment at 1microM (the maximum plasma concentration of gefitinib obtained at the clinically relevant dose) gefitinib accumulated within the cell in resistant-cell lines at concentrations similar or even higher than in gefitinib-sensitive cells tending to rule out an alteration in drug uptake as a mechanism of resistance to gefitinib treatment. Moreover, our results suggest that the extrusion of lactate by crowded cells may contribute in decreasing the pH, which in turn can influence the uptake of gefinitib and as a result the inhibition of EGFR autophosphorylation.

Harte MT, O'Brien GJ, Ryan NM, et al.
BRD7, a subunit of SWI/SNF complexes, binds directly to BRCA1 and regulates BRCA1-dependent transcription.
Cancer Res. 2010; 70(6):2538-47 [PubMed] Related Publications
We carried out a yeast two-hybrid screen using a BRCA1 bait composed of amino acids 1 to 1142 and identified BRD7 as a novel binding partner of BRCA1. This interaction was confirmed by coimmunoprecipitation of endogenous BRCA1 and BRD7 in T47D and HEK-293 cells. BRD7 is a bromodomain containing protein, which is a subunit of PBAF-specific Swi/Snf chromatin remodeling complexes. To determine the functional consequences of the BRCA1-BRD7 interaction, we investigated the role of BRD7 in BRCA1-dependent transcription using microarray-based expression profiling. We found that a variety of targets were coordinately regulated by BRCA1 and BRD7, such as estrogen receptor alpha (ERalpha). Depletion of BRD7 or BRCA1 in either T47D or MCF7 cells resulted in loss of expression of ERalpha at both the mRNA and protein level, and this loss of ERalpha was reflected in resistance to the antiestrogen drug fulvestrant. We show that BRD7 is present, along with BRCA1 and Oct-1, on the ESR1 promoter (the gene which encodes ERalpha). Depletion of BRD7 prevented the recruitment of BRCA1 and Oct-1 to the ESR1 promoter; however, it had no effect on the recruitment of the other Swi/Snf subunits BRG1, BAF155, and BAF57 or on RNA polymerase II recruitment. These results support a model whereby the regulation of ERalpha transcription by BRD7 is mediated by its recruitment of BRCA1 and Oct-1 to the ESR1 promoter.

He HH, Meyer CA, Shin H, et al.
Nucleosome dynamics define transcriptional enhancers.
Nat Genet. 2010; 42(4):343-7 [PubMed] Free Access to Full Article Related Publications
Chromatin plays a central role in eukaryotic gene regulation. We performed genome-wide mapping of epigenetically marked nucleosomes to determine their position both near transcription start sites and at distal regulatory elements, including enhancers. In prostate cancer cells, where androgen receptor binds primarily to enhancers, we found that androgen treatment dismisses a central nucleosome present at androgen receptor binding sites that is flanked by a pair of marked nucleosomes. A new quantitative model built on the behavior of such nucleosome pairs correctly identified regions bound by the regulators of the immediate androgen response, including androgen receptor and FOXA1. More importantly, this model also correctly predicted previously unidentified binding sites for other transcription factors present after prolonged androgen stimulation, including OCT1 and NKX3-1. Therefore, quantitative modeling of enhancer structure provides a powerful predictive method to infer the identity of transcription factors involved in cellular responses to specific stimuli.

Hernández A, Villegas A, Anguita E
Human promoter mutations unveil Oct-1 and GATA-1 opposite action on Gfi1b regulation.
Ann Hematol. 2010; 89(8):759-65 [PubMed] Related Publications
Growth factor-independence 1b (Gfi1b) is a zinc finger transcription factor essential for erythroid and megakaryocytic development. To better understand Gfi1b regulation and to know the implication of the level of expression of this gene in human pathology, we have searched for promoter punctual sequence variations in 214 patients with different hematological diseases. We found two previously unknown congenital mutations at evolutionary conserved GATA and octamer-binding (Oct) transcription factor sites. The Oct site mutation was also found in five relatives of the patient. The GATA motif mutation reduced promoter activity by 50% in vitro, while homozygous patients with the octamer site mutation showed a four-to-five times increase of Gfi1b RNA in platelets. Electrophoretic mobility shift analyses demonstrated that different protein complexes bind to both sites and that binding is reduced by the mutations. Finally, we found that GATA-1 and Oct-1 are the main components of each complex. This study provides evidences of a new mechanism for Gfi1b repression. This is also the first report of Gfi1b mutations with a functional implication; further investigation and follow-up will clarify the involvement of these mutations in hematological disease.

Kang J, Shakya A, Tantin D
Stem cells, stress, metabolism and cancer: a drama in two Octs.
Trends Biochem Sci. 2009; 34(10):491-9 [PubMed] Related Publications
It is a classic story of two related transcription factors. Oct4 is a potent regulator of pluripotency during early mammalian embryonic development, and is notable for its ability to convert adult somatic cells to pluripotency. The widely expressed Oct1 protein shares significant homology with Oct4, binds to the same sequences, regulates common target genes, and shares common modes of upstream regulation, including the ability to respond to cellular stress. Both proteins are also associated with malignancy, yet Oct1 cannot substitute for Oct4 in the generation of pluripotency. The molecular underpinnings of these phenomena are emerging, as are the consequences for adult stem cells and cancer, and thereby hangs a tale.

Kim DH, Sriharsha L, Xu W, et al.
Clinical relevance of a pharmacogenetic approach using multiple candidate genes to predict response and resistance to imatinib therapy in chronic myeloid leukemia.
Clin Cancer Res. 2009; 15(14):4750-8 [PubMed] Related Publications
PURPOSE: Imatinib resistance is major cause of imatinib mesylate (IM) treatment failure in chronic myeloid leukemia (CML) patients. Several cellular and genetic mechanisms of imatinib resistance have been proposed, including amplification and overexpression of the BCR/ABL gene, the tyrosine kinase domain point mutations, and MDR1 gene overexpression.
EXPERIMENTAL DESIGN: We investigated the impact of 16 single nucleotide polymorphisms (SNP) in five genes potentially associated with pharmacogenetics of IM, namely ABCB1, multidrug resistance 1; ABCG2, breast-cancer resistance protein; CYP3A5, cytochrome P450-3A5; SLC22A1, human organic cation transporter 1; and AGP, alpha1-acid glycoprotein. The DNAs from peripheral blood samples in 229 patients were genotyped.
RESULTS: The GG genotype in ABCG2 (rs2231137), AA genotype in CYP3A5 (rs776746), and advanced stage were significantly associated with poor response to IM especially for major or complete cytogenetic response, whereas the GG genotype at SLC22A1 (rs683369) and advanced stage correlated with high rate of loss of response or treatment failure to IM therapy.
CONCLUSIONS: We showed that the treatment outcomes of imatinib therapy could be predicted using a novel, multiple candidate gene approach based on the pharmacogenetics of IM.

Bayer M, Kuçi Z, Schömig E, et al.
Uptake of mIBG and catecholamines in noradrenaline- and organic cation transporter-expressing cells: potential use of corticosterone for a preferred uptake in neuroblastoma- and pheochromocytoma cells.
Nucl Med Biol. 2009; 36(3):287-94 [PubMed] Related Publications
For imaging of neuroblastoma and phaeochromocytoma, [(123)I]meta-iodobenzylguanidine ([(123)I]mIBG) is routinely used, whereas [(18)F]6-fluorodopamine ([(18)F]6-FDA) is sporadically applied for positron emission tomography in pheochromocytoma. Both substances are taken up by catecholamine transporters (CATs). In competition, some other cell types are able to take up catecholamines and related compounds probably by organic cation (OCT) [extraneuronal monoamine (EMT)] transporters (OCT1, OCT2, OCT3=EMT). In this study, we investigated the uptake of radioiodine-labeled meta-iodobenzylguanidine (mIBG) as well as [(3)H]dopamine (mimicring 6-fluorodopamine) and [(3)H]noradrenaline. SK-N-SH (neuroblastoma) and PC-12 (phaeochromocytoma) cells were used and compared with HEK-293 cells transfected with OCT1, OCT2 and OCT3, respectively. In order to gain a more selective uptake in CAT expressing tumor cells, different specific inhibitors were measured. Uptake of mIBG into OCT-expressing cells was similar or even better as into both CAT-expressing cell lines, whereas dopamine and noradrenaline uptake was much lower in OCT-expressing cells. In presence of corticosterone (f.c. 10(-4) M], catecholamine and mIBG uptake into SK-N-SH and PC-12 cells was only slightly reduced. In contrast, this process was significantly inhibited in OCT2 and OCT3 transfected HEK-293 as well as in Caki-1 cells, which naturally express OCT3. We conclude that the well-known corticosteroid corticosterone might be used in combination with [(18)F]6-FDA or [(123)I]mIBG to improve specific imaging of neuroblastoma and pheochromocytoma and to reduce irradiation dose to nontarget organs in [(131)I]mIBG treatment.

Shakya A, Cooksey R, Cox JE, et al.
Oct1 loss of function induces a coordinate metabolic shift that opposes tumorigenicity.
Nat Cell Biol. 2009; 11(3):320-7 [PubMed] Related Publications
Cancer cells frequently undergo a shift from oxidative to glycolytic metabolism. Although there is interest in targeting metabolism as a form of cancer therapy, this area still remains in its infancy. Using cells, embryos and adult animals, we show here that loss of the widely expressed transcription factor Oct1 induces a coordinated metabolic shift: mitochondrial activity and amino acid oxidation are increased, while glucose metabolism is reduced. Altered expression of direct Oct1 targets encoding metabolic regulators provides a mechanistic underpinning to these results. We show that these metabolic changes directly oppose tumorigenicity. Collectively, our findings show that Oct1, the genes it regulates and the pathways these genes affect could be used as targets for new modes of cancer therapy.

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