FOSL2; FOS-like antigen 2 (2p23.3)

Gene Summary

Gene:FOSL2; FOS-like antigen 2
Aliases: FRA2
Summary:The Fos gene family consists of 4 members: FOS, FOSB, FOSL1, and FOSL2. These genes encode leucine zipper proteins that can dimerize with proteins of the JUN family, thereby forming the transcription factor complex AP-1. As such, the FOS proteins have been implicated as regulators of cell proliferation, differentiation, and transformation. [provided by RefSeq, Jul 2014]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:fos-related antigen 2
Updated:14 December, 2014


What does this gene/protein do?
Show (9)


What pathways are this gene/protein implicaed in?
- Bone Remodelling BIOCARTA
Data from KEGG and BioCarta [BIOCARTA terms] via CGAP

Cancer Overview

Research Indicators

Publications Per Year (1989-2014)
Graph generated 14 December 2014 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.

  • SPRR1B
  • Gene Expression
  • CCR4
  • Ovarian Cancer
  • FOSB
  • Leukemic Gene Expression Regulation
  • Apoptosis
  • Tumor Microenvironment
  • Proto-Oncogene Proteins c-jun
  • Adult T-Cell Leukemia-Lymphoma
  • Chromosome 2
  • Acute Myeloid Leukaemia
  • siRNA
  • Proto-Oncogenes
  • Up-Regulation
  • Tumor Markers
  • Gene Expression Profiling
  • ID2
  • Promoter Regions
  • DNA-Binding Proteins
  • Cell Cycle Proteins
  • JNK Mitogen-Activated Protein Kinases
  • Transcriptional Activation
  • Angiogenesis
  • Cell Culture Techniques
  • Immunohistochemistry
  • Receptors, CCR4
  • Lymphoma, T-Cell
  • Transcription Factors
  • Translocation
  • Fos-Related Antigen-2
  • Transcription
  • Proto-Oncogene Proteins c-fos
  • CCAAT-Enhancer-Binding Protein-beta
  • Base Sequence
  • Epithelial Cells
  • Skin Cancer
  • Mutation
  • Cancer Gene Expression Regulation
  • Transcription Factor AP-1
Tag cloud generated 14 December, 2014 using data from PubMed, MeSH and CancerIndex

Related Links

Latest Publications: FOSL2 (cancer-related)

Kharman-Biz A, Gao H, Ghiasvand R, et al.
Expression of activator protein-1 (AP-1) family members in breast cancer.
BMC Cancer. 2013; 13:441 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The activator protein-1 (AP-1) transcription factor is believed to be important in tumorigenesis and altered AP-1 activity was associated with cell transformation. We aimed to assess the potential role of AP-1 family members as novel biomarkers in breast cancer.
METHODS: We studied the expression of AP-1 members at the mRNA level in 72 primary breast tumors and 37 adjacent non-tumor tissues and evaluated its correlation with clinicopathological parameters including estrogen receptor (ER), progesterone receptor (PR) and HER2/neu status. Expression levels of Ubiquitin C (UBC) were used for normalization. Protein expression of AP-1 members was assessed using Western blot analysis in a subset of tumors. We used student's t-test, one-way ANOVA, logistic regression and Pearson's correlation coefficient for statistical analyses.
RESULTS: We found significant differences in the expression of AP-1 family members between tumor and adjacent non-tumor tissues for all AP-1 family members except Fos B. Fra-1, Fra-2, Jun-B and Jun-D mRNA levels were significantly higher in tumors compared to adjacent non-tumor tissues (p < 0.001), whilst c-Fos and c-Jun mRNA levels were significantly lower in tumors compared with adjacent non-tumor tissues (p < 0.001). In addition, Jun-B overexpression had outstanding discrimination ability to differentiate tumor tissues from adjacent non-tumor tissues as determined by ROC curve analysis. Moreover, Fra-1 was significantly overexpressed in the tumors biochemically classified as ERα negative (p = 0.012) and PR negative (p = 0.037). Interestingly, Fra-1 expression was significantly higher in triple-negative tumors compared with luminal carcinomas (p = 0.01).
CONCLUSIONS: Expression levels of Fra-1 and Jun-B might be possible biomarkers for prognosis of breast cancer.

Related: Breast Cancer

Higuchi T, Nakayama T, Arao T, et al.
SOX4 is a direct target gene of FRA-2 and induces expression of HDAC8 in adult T-cell leukemia/lymphoma.
Blood. 2013; 121(18):3640-9 [PubMed] Related Publications
Previously, we have shown that an AP-1 family member, FRA-2, is constitutively expressed in adult T-cell leukemia/lymphoma (ATL) and, together with JUND, upregulates CCR4 and promotes ATL cell growth. Among the identified potential target genes of FRA-2/JUND was SOX4. Here, we examine the expression and function of SOX4 in ATL. SOX4 was indeed consistently expressed in primary ATL cells. FRA-2/JUND efficiently activated the SOX4 promoter via an AP-1 site. Knockdown of SOX4 expression by small interfering RNA (siRNA) strongly suppressed cell growth of ATL cell lines. Microarray analyses revealed that SOX4 knockdown reduced the expression of genes such as germinal center kinase related (GCKR), NAK-associated protein 1 (NAP1), and histone deacetylase 8 (HDAC8). We confirmed consistent expression of GCKR, NAP1, and HDAC8 in primary ATL cells. We also showed direct activation of the HDAC8 promoter by SOX4. Furthermore, siRNA knockdown of GCKR, NAP1, and HDAC8 each significantly suppressed cell growth of ATL cell lines. Taken together, we have revealed an important oncogenic cascade involving FRA-2/JUND and SOX4 in ATL, which leads to the expression of genes such as GCKR, NAP1, and HDAC8.

Zhou L, Graves M, MacDonald G, et al.
Microenvironmental regulation of BRCA1 gene expression by c-Jun and Fra2 in premalignant human ovarian surface epithelial cells.
Mol Cancer Res. 2013; 11(3):272-81 [PubMed] Related Publications
Reduced BRCA1 gene expression is common in the sporadic form of ovarian carcinoma. The spread of this highly lethal cancer often begins when tumor cell clusters are shed into the fluid of the abdominopelvic cavity such that they can float freely before seeding distant sites on the peritoneal walls and organs. Thus, the microenvironment that tumor cells find themselves in changes dramatically during these early shedding and floating stages of transperitoneal metastasis. To mimic this microenvironmental change in vitro, we released premalignant human ovarian surface epithelial cells from the substratum and forced them to cluster in suspension. Under these conditions, steady state levels of BRCA1 mRNA and protein fell significantly and the transcriptional activation state of the BRCA1 promoter was suppressed. Analysis of the promoter indicated that the previously identified "CRE" element located within the "positive regulatory region" (PRR) contributed to this suppression. More specifically, we show that the suppression was mediated, at least in part, by a suspension culture-driven decrease in the levels of two members of the AP1 transcription factor complex, c-Jun and Fra2, that bind to the CRE element. Therefore, a microenvironmental change that is manifested during the initial stages of ovarian carcinoma dissemination may, potentially, help suppress BRCA1 expression in sporadic tumors and thus promote their progression.

Related: Ovarian Cancer

Shin SY, Choi C, Lee HG, et al.
Transcriptional regulation of the interleukin-11 gene by oncogenic Ras.
Carcinogenesis. 2012; 33(12):2467-76 [PubMed] Related Publications
Interleukin-11 (IL-11), which belongs to a class of IL6-type cytokines, plays an important role in inflammation, motility and invasion in cancer. The ras mutation is frequently found in human cancer, but little is known regarding the transcriptional activation of the IL-11 gene by the Ras signal pathway in tumour cells. In this study, we investigated the role of Ras in the regulation of IL-11 using two different cell model systems: mouse NIH3T3 cells over-expressing oncogenic Ras with a tet-on system and Capan-1 human pancreatic carcinoma cells harbouring a K-ras mutation. We found that IL-11 expression was up-regulated at the transcriptional level by oncogenic Ras. Activation of the AP-1 response element, located between -153 and -30 in the 5'-regulatory region of the IL-11 gene, was necessary for oncogenic Ras-induced IL-11 promoter activation. AP-1 proteins, including Fra-1 and Fra-2, were up-regulated through the Raf/MEK and phosphatidylinositol 3-kinase (PI3K)/Akt pathways by oncogenic Ras. Knockdown of Fra-1 by siRNA in NIH3T3 or Capan-1 cells strongly attenuated oncogenic Ras-induced IL-11 expression. Additionally, inhibition of JNK, p38 and Stat3 abrogated oncogenic Ras-induced IL-11 expression. These results suggest that both the PI3K and Raf pathways are necessary for the expression of IL-11 in oncogenic Ras-mutated cells, and that JNK, p38 and Stat3 also contribute to oncogenic Ras-induced IL-11 expression.

Dippel V, Milde-Langosch K, Wicklein D, et al.
Influence of L1-CAM expression of breast cancer cells on adhesion to endothelial cells.
J Cancer Res Clin Oncol. 2013; 139(1):107-21 [PubMed] Related Publications
PURPOSE: Expression of the adhesion molecule L1-CAM (L1) has been shown to correlate with early recurrence in breast cancer. Here, we investigated whether L1-CAM expression of breast cancer cells might influence adherence to human pulmonary microvascular endothelial cells (HPMEC) and thus promote metastasis.
METHODS: MDA-MB231-Fra2 breast cancer cells that express high levels of L1-CAM (L1(high) cells) were stably transfected to generate clones with strong L1-CAM downregulation. Adhesion to activated HPMEC was studied in dynamic cell flow and static assays. Potential binding partners on endothelial cells were identified by blocking experiments and adhesion assays after coating of the flow channels with recombinant proteins.
RESULTS: Adhesion of L1(high) cells to activated HPMEC was significantly higher compared to L1l(ow) clones under flow conditions. Blocking experiments and adhesion assays with recombinant proteins identified activated leucocyte cell adhesion molecule (ALCAM) or L1 itself, but not ICAM-1, as potential binding partners on endothelial cells. E-selectin blocking antibodies strongly diminished the adherence of breast cancer cells irrespective of their L1-CAM expression.
CONCLUSIONS: Our experiments indicate that L1-CAM expression on breast cancer cells can promote adherence to activated endothelial cells by binding to endothelial L1-CAM or ALCAM. This mechanism might lead to increased metastasis and a poor prognosis in L1-CAM-positive carcinomas in vivo. Therefore, L1-CAM might be a suitable therapeutic target in breast cancers with a high L1-CAM expression.

Related: Breast Cancer

Cukierski WJ, Nandy K, Gudla P, et al.
Ranked retrieval of segmented nuclei for objective assessment of cancer gene repositioning.
BMC Bioinformatics. 2012; 13:232 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Correct segmentation is critical to many applications within automated microscopy image analysis. Despite the availability of advanced segmentation algorithms, variations in cell morphology, sample preparation, and acquisition settings often lead to segmentation errors. This manuscript introduces a ranked-retrieval approach using logistic regression to automate selection of accurately segmented nuclei from a set of candidate segmentations. The methodology is validated on an application of spatial gene repositioning in breast cancer cell nuclei. Gene repositioning is analyzed in patient tissue sections by labeling sequences with fluorescence in situ hybridization (FISH), followed by measurement of the relative position of each gene from the nuclear center to the nuclear periphery. This technique requires hundreds of well-segmented nuclei per sample to achieve statistical significance. Although the tissue samples in this study contain a surplus of available nuclei, automatic identification of the well-segmented subset remains a challenging task.
RESULTS: Logistic regression was applied to features extracted from candidate segmented nuclei, including nuclear shape, texture, context, and gene copy number, in order to rank objects according to the likelihood of being an accurately segmented nucleus. The method was demonstrated on a tissue microarray dataset of 43 breast cancer patients, comprising approximately 40,000 imaged nuclei in which the HES5 and FRA2 genes were labeled with FISH probes. Three trained reviewers independently classified nuclei into three classes of segmentation accuracy. In man vs. machine studies, the automated method outperformed the inter-observer agreement between reviewers, as measured by area under the receiver operating characteristic (ROC) curve. Robustness of gene position measurements to boundary inaccuracies was demonstrated by comparing 1086 manually and automatically segmented nuclei. Pearson correlation coefficients between the gene position measurements were above 0.9 (p < 0.05). A preliminary experiment was conducted to validate the ranked retrieval in a test to detect cancer. Independent manual measurement of gene positions agreed with automatic results in 21 out of 26 statistical comparisons against a pooled normal (benign) gene position distribution.
CONCLUSIONS: Accurate segmentation is necessary to automate quantitative image analysis for applications such as gene repositioning. However, due to heterogeneity within images and across different applications, no segmentation algorithm provides a satisfactory solution. Automated assessment of segmentations by ranked retrieval is capable of reducing or even eliminating the need to select segmented objects by hand and represents a significant improvement over binary classification. The method can be extended to other high-throughput applications requiring accurate detection of cells or nuclei across a range of biomedical applications.

Related: Breast Cancer FISH

Nakayama T, Higuchi T, Oiso N, et al.
Expression and function of FRA2/JUND in cutaneous T-cell lymphomas.
Anticancer Res. 2012; 32(4):1367-73 [PubMed] Related Publications
Adult T-cell leukemia/lymphoma (ATLL) and cutaneous T-cell lymphomas (CTCLs) are known to frequently express CC chemokine receptor 4 (CCR4). Previously, we investigated the transcriptional control of CCR4 expression in ATLL and have found that an activating protein 1 (AP1) family member, FBJ murine osteosarcoma viral oncogene homolog (FOS)-related antigen 2 (FRA2), is consistently expressed at high levels in ATLL and, together with v-JUN avian sarcoma virus 17 oncogene homolog D (JUND), up-regulates the expression of CCR4 as well as that of several proto-oncogenes such as v-MYB myeloblastosis viral oncogene homolog (MYB), murine double minute 2 homolog (MDM2), and B-cell lymphoma 6 (BCL6). Here, we examined the expression of these genes in clinical samples of CTCLs. We detected the transcripts of FRA2, JUND, CCR4, MYB, MDM2, and BCL6 at high levels in CTCL skin lesions. Except for BCL6, we confirmed protein expression of FRA2, JUND, CCR4, MYB, and MDM2 in CTCL skin lesions. Furthermore, siRNA-mediated knockdown of FRA2 or JUND suppressed cell growth and the expression of CCR4, MYB, MDM2, and BCL6 in CTCL cell lines. Our results, thus, demonstrate the presence of a common oncogenic cascade initiated by FRA2/JUND in CCR4-expressing mature T-cell malignancies such as ATLL and CTCLs.

Related: Skin Cancer JUND

Cooper LA, Gutman DA, Chisolm C, et al.
The tumor microenvironment strongly impacts master transcriptional regulators and gene expression class of glioblastoma.
Am J Pathol. 2012; 180(5):2108-19 [PubMed] Free Access to Full Article Related Publications
The Cancer Genome Atlas (TCGA) project has generated gene expression data that divides glioblastoma (GBM) into four transcriptional classes: proneural, neural, classical, and mesenchymal. Because transcriptional class is only partially explained by underlying genomic alterations, we hypothesize that the tumor microenvironment may also have an impact. In this study, we focused on necrosis and angiogenesis because their presence is both prognostically and biologically significant. These features were quantified in digitized histological images of TCGA GBM frozen section slides that were immediately adjacent to samples used for molecular analysis. Correlating these features with transcriptional data, we found that the mesenchymal transcriptional class was significantly enriched with GBM samples that contained a high degree of necrosis. Furthermore, among 2422 genes that correlated with the degree of necrosis in GBMs, transcription factors known to drive the mesenchymal expression class were most closely related, including C/EBP-β, C/EBP-δ, STAT3, FOSL2, bHLHE40, and RUNX1. Non-mesenchymal GBMs in the TCGA data set were found to become more transcriptionally similar to the mesenchymal class with increasing levels of necrosis. In addition, high expression levels of the master mesenchymal factors C/EBP-β, C/EBP-δ, and STAT3 were associated with a poor prognosis. Strong, specific expression of C/EBP-β and C/EBP-δ by hypoxic, perinecrotic cells in GBM likely account for their tight association with necrosis and may be related to their poor prognosis.

Related: Angiogenesis and Cancer Signal Transduction

Fu L, Balasubramanian M, Shan J, et al.
Auto-activation of c-JUN gene by amino acid deprivation of hepatocellular carcinoma cells reveals a novel c-JUN-mediated signaling pathway.
J Biol Chem. 2011; 286(42):36724-38 [PubMed] Free Access to Full Article Related Publications
Mammalian cells respond to protein or amino acid (AA) limitation by activating a number of signaling pathways, collectively referred to as the AA response (AAR), that modulate a range of cellular functions, including transcriptional induction of target genes. This study demonstrates that in hepatocellular carcinoma cells, expression of c-JUN, JUN-B, c-FOS, and FOS-B was induced by the AAR, whereas JUN-D, FRA-1, and FRA-2 were not. Of the four activated FOS/JUN members, c-JUN made the largest contribution to the induction of several known AAR target genes. For several human liver, prostate, and ovarian cell lines, the AAR-induced increase in c-JUN expression was greater in transformed cells compared with nontransformed counterparts, an effect independent of cell growth rate. Thus far, the best characterized AA-responsive genes are all transcriptionally activated by ATF4, but the AAR-dependent induction of c-JUN transcription was ATF4-independent. The increased expression of c-JUN was dependent on ATF2 and on activation of the MEK-ERK and JNK arms of the MAPK signaling pathways. Formation of c-JUN-ATF2-activated heterodimers was increased after AA limitation, and c-JUN or ATF2 knockdown suppressed the induction of c-JUN and other AAR target genes. AA deprivation triggers a feed-forward process that involves phosphorylation of existing c-JUN protein by JNK and subsequent auto-activation of the c-JUN gene by recruitment of c-JUN and ATF2 to two AP-1 sites within the proximal promoter. The results document the novel observation that AP-1 sequences within the c-JUN gene can function as transcriptional amino acid-response elements.

Related: Liver Cancer

Singh R, Cadeddu RP, Fröbel J, et al.
The non-steroidal anti-inflammatory drugs Sulindac sulfide and Diclofenac induce apoptosis and differentiation in human acute myeloid leukemia cells through an AP-1 dependent pathway.
Apoptosis. 2011; 16(9):889-901 [PubMed] Related Publications
Acute myeloid leukemia is a heterogeneous disease with varying genetic and molecular pathologies. Non-steroidal anti-inflammatory drugs (NSAIDs) have been proven to possess significant anti-proliferative potential in various cancer cells in vitro and in vivo. Hence, treatment with these agents can be utilized to study disease specific anti-proliferative pathways. In this study, a total number of 42 bone marrow derived CD34(+) selected de novo AML patient samples and the AML cell lines THP-1 and HL-60 were treated with the NSAIDs Sulindac sulfide and Diclofenac. We analyzed viability, apoptosis, differentiation and addressed the molecular mechanisms involved. We found a consistent induction of apoptosis and to some extent an increased myeloid differentiation capacity in NSAID treated AML cells. Comprehensive protein and gene expression profiling of Diclofenac treated AML cells revealed transcriptional activation of GADD45α and its downstream MAPK/JNK pathway as well as increased protein levels of the caspase-3 precursor. This pointed towards a role of the c-Jun NH(2)-terminal kinase (JNK) in NSAID mediated apoptosis that we found indeed to be dependent on JNK activity as addition of a specific JNK-inhibitor abrogated apoptosis. Furthermore, the AP-1 transcription factor family members' c-Jun, JunB and Fra-2 were transcriptionally activated in NSAID treated AML cells and re-expression of these transcription factors led to activation of GADD45α with induction of apoptosis. Mechanistically, we demonstrate that NSAIDs induce apoptosis in AML through a novel pathway involving increased expression of AP-1 heterodimers, which by itself is sufficient to induce GADD45α expression with consecutive activation of JNK and induction of apoptosis.

Related: Apoptosis CASP3 Acute Myeloid Leukemia (AML)

Sanjmyatav J, Steiner T, Wunderlich H, et al.
A specific gene expression signature characterizes metastatic potential in clear cell renal cell carcinoma.
J Urol. 2011; 186(1):289-94 [PubMed] Related Publications
PURPOSE: The discovery of metastasis markers in clear cell renal cell carcinoma is of critical importance to define individual metastatic risk and select patients for new targeted therapies. We identified potential biomarkers for metastatic clear cell renal cell carcinoma by gene expression analysis.
MATERIALS AND METHODS: We performed transcriptional profiling of 16 primary metastatic and 18 nonmetastatic clear cell renal cell carcinomas with PIQOR™ microarrays. Differentially expressed genes were validated by quantitative real-time polymerase chain reaction.
RESULTS: Genes discriminating between metastatic and nonmetastatic tumors were identified at q <0.001 by significance analysis of microarrays. The metastatic signature contained 127 transcripts. In metastatic samples a greater than 4-fold decrease in expression was detected for the genes CD151 and IKBA (t/F statistic p <0.0001) while the genes MMP16, B7-H1, BCL2L2 and FRA2 showed greater than 4-fold increase of expression in metastatic primary tumors (p <0.0001). Quantitative real-time polymerase chain reaction revealed significant differences in expression among all metastatic tumors, including synchronously and metachronously metastasized tumors, and nonmetastatic tumors for FRA2 (p = 0.032) and CD151 (p = 0.005). In addition, the genes B7-H1 (p = 0.040), FRA2 (p = 0.035), CD151 (p = 0.004) and BCL2L2 (p = 0.035) showed significantly higher expression in early metastasized than in nonmetastatic tumor samples. Different B7-H1 (p = 0.002) and BCL2L2 (p = 0.007) expression levels were found in samples with late metastasis compared to those in synchronously metastasized tumors.
CONCLUSIONS: We determined a metastatic signature of clear cell renal cell carcinoma by microarray analysis. Our data provide the possibility of defining the metastatic potential of primary clear cell renal cell carcinoma based on a select number of genes even in a localized situation.

Related: Kidney Cancer

Wang L, Rodrigues NA, Wu Y, et al.
Pleiotropic action of AP-1 in v-Src-transformed cells.
J Virol. 2011; 85(13):6725-35 [PubMed] Free Access to Full Article Related Publications
The activation of AP-1 is a hallmark of cell transformation by tyrosine kinases. In this study, we characterize the role of AP-1 proteins in the transformation of chicken embryo fibroblasts (CEF) by v-Src. In normal CEF, the expression of a dominant negative mutant of c-Jun (TAM67) induced senescence. In contrast, three distinct phenotypes were observed when TAM67 was expressed in v-Src-transformed CEF. While senescent cells were also present, the inhibition of AP-1 caused apoptosis in a fraction of the v-Src-transformed cells. In addition, cells containing lipid-rich vesicles accumulated, suggesting that a subpopulation of the v-Src-transformed cells underwent differentiation in response to the inhibition of AP-1. JunD and Fra-2 were the main components of this factor, while c-Jun accounted for a minor fraction of AP-1 in v-Src-transformed CEF. The downregulation of c-Jun expression by short hairpin RNA (shRNA) induced senescence in normal and v-Src-transformed cells. In contrast, a high incidence of apoptosis was caused by the downregulation of JunD, suggesting that it is required for the survival of v-Src-transformed CEF. Levels of the p53 tumor suppressor were elevated under conditions of JunD inhibition. Repression of p53 by shRNA enhanced the survival and anchorage-independent proliferation of v-Src-transformed CEF with JunD/AP-1 inhibition. The inhibition of Fra-2 had no visible phenotype in normal CEF but caused the appearance of lipid-rich vesicles in v-Src-transformed CEF. Therefore, AP-1 facilitated transformation by acting as a survival factor, by inhibiting premature entry into senescence, and by blocking the differentiation of v-Src-transformed CEF.

Related: SRC v-src avian sarcoma (Schmidt-Ruppin A-2) viral oncogene homolog

Li Z, Sasaki Y, Mezawa M, et al.
cAMP and fibroblast growth factor 2 regulate bone sialoprotein gene expression in human prostate cancer cells.
Gene. 2011; 471(1-2):1-12 [PubMed] Related Publications
Bone sialoprotein (BSP) is a noncollagenous protein of the extracellular matrix in mineralized connective tissues that has been implicated in the nucleation of hydroxyapatite. Forskolin (FSK), an activator of adenylate cyclase, increased the intracellular cAMP level, which stimulates the proliferation and differentiation of osteoblasts. Fibroblast growth factor 2 (FGF2) is a potent mitogen in many cell types, including osteoblasts. In human prostate cancer DU145 cells, FSK (1 μM) and FGF2 (10 ng/ml) increased BSP and Runx2 mRNA and protein levels at 3 and 12h, respectively. Transient transfection analyses were performed using chimeric constructs of the human BSP gene promoter linked to a luciferase reporter gene. Treatment of DU145 cells with FSK (1 μM) and FGF2 (10 ng/ml) increased the luciferase activities of constructs between -60LUC to -927LUC and -108LUC to -927LUC, including the human BSP gene promoter. Effects of FSK and FGF2 abrogated in constructs included 2bp mutations in the two cAMP response elements (CRE1 and CRE2). Luciferase activities induced by FSK and FGF2 were blocked by protein kinase A and tyrosine kinase inhibitors. Gel mobility shift analyses showed that FSK and FGF2 increased the binding of CRE1 and CRE2. CRE1-protein complexes were supershifted by phospho-CREB1 and c-Fos antibodies, and disrupted by CREB1, c-Jun, JunD, Fra2, p300, Runx2, Dlx5 and Smad1 antibodies. CRE2-protein complexes were disrupted by CREB1, phospho-CREB1, c-Fos, c-Jun, JunD, Fra2, p300, Runx2, Dlx5 and Smad1 antibodies. These studies demonstrate that FSK and FGF2 stimulate BSP transcription in DU145 human prostate cancer cells by targeting the CRE1 and CRE2 elements in the human BSP gene promoter.

Related: FGF2 Prostate Cancer

Liss AS, Tiwari R, Kralova J, Bose HR
Cell transformation by v-Rel reveals distinct roles of AP-1 family members in Rel/NF-kappaB oncogenesis.
Oncogene. 2010; 29(35):4925-37 [PubMed] Free Access to Full Article Related Publications
Cell transformation by the v-rel oncogene is mediated by the aberrant expression of genes that are normally tightly regulated by other Rel/NF-kappaB family members. Although a number of genes inappropriately activated or suppressed by v-Rel have been identified, their contributions to the v-Rel transformation process have been poorly characterized. Here, we examine the role of individual AP-1 proteins in v-Rel-mediated transformation. v-Rel-transformed cells exhibit elevated RNA and protein expression of c-Fos, c-Jun and ATF2 and sustained repression of Fra-2. c-Fos and c-Jun are essential in both the initiation and maintenance of v-Rel-mediated transformation, whereas Fra-2 is dispensable. By employing a c-Jun dimerization mutant, we further identified Fos/Jun heterodimers as major contributors to the v-Rel transformation process. The inability of c-Rel to induce the expression of c-Fos and c-Jun contributes to its weaker oncogenic potential relative to v-Rel. Our studies also demonstrate that v-Rel may induce AP-1 members by directly upregulating gene expression (c-fos and ATF2) and by activating pathways that stimulate AP-1 activity. Although elevated expression of ATF2 is also required for v-Rel-mediated transformation, its ectopic overexpression is inhibitory. Investigating the mode of ATF2 regulation revealed a positive feedback mechanism whereby ATF2 induces p38 MAPK phosphorylation to further induce its own activity. In addition, these studies identified Ha-Ras as an effector of v-Rel-mediated transformation and reveal a novel role for ATF2 in the inhibition of the Ras-Raf-MEK-ERK signaling pathway. Overall, these studies reveal distinct and complex roles of AP-1 proteins in Rel/NF-kappaB oncogenesis.

Li Z, Wang Z, Yang L, et al.
Fibroblast growth factor 2 regulates bone sialoprotein gene transcription in human breast cancer cells.
J Oral Sci. 2010; 52(1):125-32 [PubMed] Related Publications
Bone sialoprotein (BSP) is a major non-collagenous, extracellular matrix glycoprotein associated with mineralized tissues. Fibroblast growth factor 2 (FGF2) is recognized as a potent mitogen for a variety of mesenchymal cells. FGF2 produced by osteoblasts accumulates in the bone matrix and acts as an autocrine/paracrine regulator of osteoblasts. We previously reported that FGF2 regulates BSP gene transcription through the FGF2 response element (FRE) and activator protein 1 (AP1) binding site overlapping with the glucocorticoid response element in the rat BSP gene promoter. In the present study, FGF2 (10 ng/ml) increased BSP and Runx2 mRNA levels at 6 h in MCF7 human breast cancer cells. Transient transfection analyses were performed using chimeric constructs of the human BSP gene promoter linked to a luciferase reporter gene. Treatment of MCF7 cells with FGF2 (10 ng/ml) increased the luciferase activity of the constructs between -84LUC and -927LUC. Gel mobility shift analyses showed that FGF2 increased the binding of AP1 and CRE2. The CRE2- and AP1-protein complexes were disrupted by antibodies against CREB1, c-Fos, c-Jun, Fra2, p300 and Runx2. These studies demonstrate that FGF2 stimulates BSP transcription in MCF7 human breast cancer cells by targeting the AP1 and CRE2 elements in the human BSP gene promoter.

Related: Breast Cancer FGF2 IBSP

Schröder C, Schumacher U, Müller V, et al.
The transcription factor Fra-2 promotes mammary tumour progression by changing the adhesive properties of breast cancer cells.
Eur J Cancer. 2010; 46(9):1650-60 [PubMed] Related Publications
The transcription factor Fra-2 (Fos-related antigen-2) has been implicated in invasion of breast cancer cells, but there is only sparse information about its role in clinical tumours. In the present study, we analysed Fra-2 mRNA expression in a cohort of 167 patients, and found significant correlations between high Fra-2 expression and nodal involvement or reduced disease-free survival. To get more information about the underlying mechanisms, we generated stably transfected MDA-MB231 breast cancer cells with increased Fra-2 expression. Compared with the controls, these clones did not differ in proliferation and motility, but had higher invasive potential. By global gene expression analysis and subsequent validation of selected genes, we identified a number of proteins involved in cell-cell or cell-matrix interactions that were up- or down-regulated in Fra-2 overexpressing cells, e.g. connexin 43, ICAM-1, L1-CAM, integrin beta 2, integrin beta 4, and integrin alpha 6. The association of Fra-2 overexpression and high ICAM-1 or L1-CAM levels could also be demonstrated in our clinical cohort of mammary tumours. In both MDA-MB231 and MCF7 cells, we found an increased attachment of Fra-2 transfectants to components of the extracellular matrix. In addition, we could show a striking increase in the number of rolling cells in flow-through assays using E-selectin coated capillaries, which might indicate a higher capacity of extravasation. In conclusion, our data obtained on breast cancer cell lines and clinical tissue samples suggest that overexpression of Fra-2 promotes breast cancer progression and metastasis by deregulation of genes involved in cell-cell and cell-ECM contacts.

Related: Breast Cancer

Mishra A, Bharti AC, Saluja D, Das BC
Transactivation and expression patterns of Jun and Fos/AP-1 super-family proteins in human oral cancer.
Int J Cancer. 2010; 126(4):819-29 [PubMed] Related Publications
Transcription factor activator protein-1 (AP-1) super-family is known to modulate expression of array of genes during development of many cancers and considered as an important target for modern therapeutics. But the role of AP-1 during development of human oral cancers is still poorly understood. Because oral cancer is one of the most common cancers in India and south-east Asia, we studied the activation and expression pattern of AP-1 family of proteins and mRNA in different stages of oral carcinogenesis. Gel-shift assay, western blotting, immunohistochemistry and northern blotting have been used to assess the binding activity and expression pattern of AP-1 family (c-Jun, JunB, JunD, c-Fos, FosB, Fra-1 and Fra-2) proteins and mRNA transcripts in a total of 100 fresh oral tissue specimens comprising precancer (n = 40), cancer (n = 50) and healthy control (n = 10). Constitutive activation of AP-1 with concomitant upregulated expression of majority of AP-1 family of proteins and mRNA was observed in cancer cases. Interestingly, almost all precancerous cases showed JunD homodimers, whereas c-Fos/JunD was the most prevalent complex found in cancer tissues. The overexpression of EGFR mRNA, p50:p50/NF-kappaB homodimer formation, together with overexpression of pERK and c-Fos proteins in this study suggests an interesting cross talk between AP-1 and NF-kappaB pathways in oral cancers. Thus, this study demonstrates differential expression and activation of AP-1 super-family proteins in relation to severity of lesion and their crucial role in human oral carcinogenesis.

Related: Oral Cancer

Yin Y, Wang S, Sun Y, et al.
JNK/AP-1 pathway is involved in tumor necrosis factor-alpha induced expression of vascular endothelial growth factor in MCF7 cells.
Biomed Pharmacother. 2009; 63(6):429-35 [PubMed] Free Access to Full Article Related Publications
Vascular endothelial growth factor (VEGF) has been implicated in breast tumor angiogenesis. And tumor necrosis factor-alpha (TNF-alpha) is a positive regulator of VEGF. This study was aimed to identify the signalling pathway of TNF-alpha in VEGF expression regulation in breast cancer cell line MCF7. Using luciferase reporter assays, we demonstrated that TNF-alpha significantly increased activator protein-1 (AP-1) transcriptional activity in the MCF7 cells. The expression of the AP-1 family members c-Jun, c-Fos and JunB and phosphorylation levels of c-Jun were upregulated by TNF-alpha, whereas other AP-1 family members Fra-1, Fra-2, and JunD were unaffected. The activation of AP-1 was associated with the formation of p-c-Jun-c-Jun and p-c-Jun-JunB homodimers. Furthermore, the phosphorylation levels of c-Jun N-terminal kinase (JNK) but not P38 and ERK were elevated by TNF-alpha in MCF7 cells. TNF-alpha potently upregulated the mRNA and protein levels of VEGF, which were significantly reversed by JNK inhibitor SP600125. Finally using chromatin immunoprecipitation (CHIP) assays, we found that p-c-Jun bound to the VEGF promoter and regulated VEGF transcription directly. These data suggest that the pro-inflammatory cytokine TNF-alpha is a critical regulator of VEGF expression in breast cancer cells, at least partially via a JNK and AP-1 dependent pathway.

Related: Breast Cancer Signal Transduction TNF VEGFA

Hu DG, Mackenzie PI
Estrogen receptor alpha, fos-related antigen-2, and c-Jun coordinately regulate human UDP glucuronosyltransferase 2B15 and 2B17 expression in response to 17beta-estradiol in MCF-7 cells.
Mol Pharmacol. 2009; 76(2):425-39 [PubMed] Related Publications
UDP-glucuronosyltransferase 2B15 and 2B17 expression is up-regulated by 17beta-estradiol in MCF-7 breast cancer cells, as assessed by quantitative real-time polymerase chain reaction. Using 5'-deletion mapping and site-directed mutagenesis, we demonstrate that 17beta-estradiol activation of UGT2B15 gene transcription is mediated by a 282-base pair fragment positioned -454 to -172 nucleotides from the translation start site. This region contains two putative activator protein-1 (AP-1) elements, one imperfect estrogen response element (ERE), and two consensus ERE half-sites. We propose that these five sites act as an estrogen response unit (ERU), because mutation in any site reduces activation of the UGT2B15 promoter by 17beta-estradiol. Despite the presence of two AP-1 elements, the UGT2B15 promoter is not responsive to the AP-1 activator phorbol 12-myristate 13-acetate. Although electrophoretic mobility shift assays (EMSA) indicate that the AP-1 proteins c-Jun and Fos-related antigen 2 (Fra-2) bound to the distal AP-1 site, binding of Jun or Fos family members to the proximal AP-1 site was not detected by EMSA. Chromatin immunoprecipitation assays showed a 17beta-estradiol-induced recruitment of estrogen receptor (ER) alpha, c-Jun, and Fra-2 to the 282-bp ERU. The involvement of these three transcription factors in the stimulation of UGT2B15 gene expression by 17beta-estradiol was confirmed by siRNA silencing experiments. Mutagenesis and siRNA experiments indicate that UGT2B17 expression is also regulated by 17beta-estradiol via the ERU, which is fully conserved in both promoters. Because UGT2B15 and UGT2B17 inactivate steroid hormones by glucuronidation, the regulation of their genes by 17beta-estradiol may maintain steroid hormone homeostasis and prevent excessive estrogen signaling activity.

Related: Breast Cancer

Shin S, Asano T, Yao Y, et al.
Activator protein-1 has an essential role in pancreatic cancer cells and is regulated by a novel Akt-mediated mechanism.
Mol Cancer Res. 2009; 7(5):745-54 [PubMed] Related Publications
Activator protein-1 (AP-1) regulates the expression of several genes involved in human tumorigenesis. However, there is little known about this transcription factor in pancreatic ductal adenocarcinoma. We recently found high levels of AP-1-binding activities and multiple AP-1/DNA complexes containing c-Jun, JunD, Fra1, and Fra2 in pancreatic cancer cells. Transient transfection assays indicated that AP-1 was functional and capable of transactivating its gene targets. Furthermore, a c-Jun transactivation mutant inhibited anchorage-dependent and anchorage-independent proliferation, suggesting that AP-1 had an essential role in pancreatic cancer cells. Our study also uncovered a novel mechanism by which protein kinase Akt controls c-Jun activity in pancreatic cancer cells. Indeed, distinct from its known ability to induce c-fos and fra1 and to stabilize c-Jun, Akt appeared to directly regulate the transcriptional activity of c-Jun independently of the phosphorylation sites targeted by c-Jun NH(2)-terminal kinase (Ser(63)/Ser(73)) and glycogen synthase kinase-3 (Thr(239)). Our data also suggest that growth factors might use this Akt-regulated mechanism to potently induce c-Jun targets such as cyclin D1. Collectively, our findings indicate that AP-1 has an important function in pancreatic cancer cells and provide evidence for a previously unknown Akt-mediated mechanism of c-Jun activation.

Related: Cancer of the Pancreas Pancreatic Cancer AKT1 Signal Transduction

Yoshie O
[CCR4, HTLV-1 infection, and ATL oncogenesis].
Uirusu. 2008; 58(2):125-40 [PubMed] Related Publications
Adult T-cell leukemia (ATL) is a malignancy of mature CD4+ T cells that is etiologically associated with the infection of human T-cell leukemia virus type 1 (HTLV-1), an exogenous human retrovirus. Previously, we have shown that leukemic cells of most ATL patients express CCR4, a chemokine receptor known to be selectively expressed by T cell subsets such as Th2 cells, skin-homing memory/effector T cells, and regulatory T cells. Therefore, the expression of CCR4 suggests that ATL cells are mostly derived from one of these T cell subsets. We have also shown that Tax, the HTLV-1-encoded potent transcriptional activator, strongly induces the expression of CCL22, a CCR4 ligand, which promotes the cell-dependent transmission of HTLV-1 from HTLV-1-infected T cells to CCR4+ target T cells by inducing close cell-to-cell interactions. We have also shown that ATL cells aberrantly express the AP-1 family member Fra-2 which, by forming the heterodimer with JunD, potently induces the expression of not only CCR4 but also the genes such as c-Myb, MDM2 and Bcl-6, the well-known proto-oncogenes. Thus, Fra-2 is a novel oncogene of ATL, and CCR4 may be regarded as a useful tumor marker of ATL.

Mathas S, Kreher S, Meaburn KJ, et al.
Gene deregulation and spatial genome reorganization near breakpoints prior to formation of translocations in anaplastic large cell lymphoma.
Proc Natl Acad Sci U S A. 2009; 106(14):5831-6 [PubMed] Free Access to Full Article Related Publications
Although the identification and characterization of translocations have rapidly increased, little is known about the mechanisms of how translocations occur in vivo. We used anaplastic large cell lymphoma (ALCL) with and without the characteristic t(2;5)(p23;q35) translocation to study the mechanisms of formation of translocations and of ALCL transformation. We report deregulation of several genes located near the ALCL translocation breakpoint, regardless of whether the tumor contains the t(2;5). The affected genes include the oncogenic transcription factor Fra2 (located on 2p23), the HLH protein Id2 (2p25), and the oncogenic tyrosine kinase CSF1-receptor (5q33.1). Their up-regulation promotes cell survival and repression of T cell-specific gene expression programs that are characteristic for ALCL. The deregulated genes are in spatial proximity within the nuclear space of t(2;5)-negative ALCL cells, facilitating their translocation on induction of double-strand breaks. These data suggest that deregulation of breakpoint-proximal genes occurs before the formation of translocations, and that aberrant transcriptional activity of genomic regions is linked to their propensity to undergo chromosomal translocations. Also, our data demonstrate that deregulation of breakpoint-proximal genes has a key role in ALCL.

Related: Chromosome 2 Chromosome 5 ID2 CSF1R

Abba MC, Hu Y, Levy CC, et al.
Identification of modulated genes by three classes of chemopreventive agents at preneoplastic stages in a p53-null mouse mammary tumor model.
Cancer Prev Res (Phila). 2009; 2(2):175-84 [PubMed] Free Access to Full Article Related Publications
Genetically engineered mouse cancer models are among the most useful tools for testing the in vivo effectiveness of the various chemopreventive approaches. The p53-null mouse model of mammary carcinogenesis was previously characterized by us at the cellular, molecular, and pathologic levels. In a companion article, Medina et al. analyzed the efficacy of bexarotene, gefitinib, and celecoxib as chemopreventive agents in the same model. Here we report the global gene expression effects on mammary epithelium of such compounds, analyzing the data in light of their effectiveness as chemopreventive agents. SAGE was used to profile the transcriptome of p53-null mammary epithelium obtained from mice treated with each compound versus controls. This information was also compared with SAGE data from p53-null mouse mammary tumors. Gene expression changes induced by the chemopreventive treatments revealed a common core of 87 affected genes across treatments (P < 0.05). The effective compounds, bexarotene and gefitinib, may exert their chemopreventive activity, at least in part, by affecting a set of 34 genes related to specific cellular pathways. The gene expression signature revealed various genes previously described to be associated with breast cancer, such as the activator protein-1 complex member Fos-like antigen 2 (Fosl2), early growth response 1 (Egr1), gelsolin (Gsn), and tumor protein translationally controlled 1 (Tpt1), among others. The concerted modulation of many of these transcripts before malignant transformation seems to be conducive to predominantly decrease cell proliferation. This study has revealed candidate key pathways that can be experimentally tested in the same model system and may constitute novel targets for future translational research.

Related: TP53 Gefitinib (Iressa)

Leaner VD, Chick JF, Donninger H, et al.
Inhibition of AP-1 transcriptional activity blocks the migration, invasion, and experimental metastasis of murine osteosarcoma.
Am J Pathol. 2009; 174(1):265-75 [PubMed] Free Access to Full Article Related Publications
A well-characterized murine osteosarcoma model for metastasis and invasion was used in this study to determine the role of AP-1 in the progression of this disease. We analyzed K12 and K7M2 cells, two clonally related murine osteosarcoma cell lines that have been characterized as low metastatic or high metastatic, respectively, for AP-1 components and activity. AP-1 DNA binding was similar between the two cell lines; however AP-1 transcriptional activity was enhanced by 3- to 5-fold in K7M2 cells relative to that in K12 cells. The AP-1 complexes in K12 and K7M2 cells was composed primarily of cJun, JunD, FosB, Fra1, and Fra2, with the contribution of individual components in the complex varying between the two cell lines. In addition, an increase in phosphorylated cJun, JNK activity, and phosphorylated ERK1/2 was associated with the more metastatic osteosarcoma phenotype. The significance of AP-1 activation was confirmed by conditional expression of TAM67, a dominant negative mutant of cJun. Under conditions where TAM67 inhibited AP-1 activity in K7M2 cells, migration and invasion potential was significantly blocked. Tam67 expression in aggressive osteosarcoma cells decreased long-term in vivo experimental metastasis and increased survival of mice. This study shows that differences in metastatic activity can be due to AP-1 activation. The inhibition of AP-1 activity may serve as a therapeutic tool in the management of osteosarcoma.

Related: Bone Cancers Osteosarcoma Signal Transduction

Mahner S, Baasch C, Schwarz J, et al.
C-Fos expression is a molecular predictor of progression and survival in epithelial ovarian carcinoma.
Br J Cancer. 2008; 99(8):1269-75 [PubMed] Free Access to Full Article Related Publications
Members of the Fos protein family dimerise with Jun proteins to form the AP-1 transcription factor complex. They have a central function in proliferation and differentiation of normal tissue as well as in oncogenic transformation and tumour progression. We analysed the expression of c-Fos, FosB, Fra-1 and Fra-2 to investigate the function of Fos transcription factors in ovarian cancer. A total of 101 patients were included in the study. Expression of Fos proteins was determined by western blot analysis, quantified by densitometry and verified by immunohistochemistry. Reduced c-Fos expression was independently associated with unfavourable progression-free survival (20.6, 31.6 and 51.2 months for patients with low, moderate and high c-Fos expression; P=0.003) as well as overall survival (23.8, 46.0 and 55.5 months for low, moderate and high c-Fos levels; P=0.003). No correlations were observed for FosB, Fra-1 and Fra-2. We conclude that loss of c-Fos expression is associated with tumour progression in ovarian carcinoma and that c-Fos may be a prognostic factor. These results are in contrast to the classic concept of c-Fos as an oncogene, but are supported by the recently discovered tumour-suppressing and proapoptotic function of c-Fos in various cancer types.

Related: Ovarian Cancer

Hasselblatt P, Gresh L, Kudo H, et al.
The role of the transcription factor AP-1 in colitis-associated and beta-catenin-dependent intestinal tumorigenesis in mice.
Oncogene. 2008; 27(47):6102-9 [PubMed] Related Publications
Chronic inflammation is an important cancer risk factor but the molecular pathways linking inflammation and cancer are incompletely understood. The transcription factor c-Jun/AP-1 (activator protein 1) is involved in inflammatory responses and tumorigenesis and has been proposed as an essential mediator of oncogenic beta-catenin signaling in the intestine. Here, we examined the functions of c-Jun in two distinct mouse models of conditional and intestine-specific activation of beta-catenin. c-Jun is strongly expressed in the small intestine of mutant mice. However, beta-catenin-dependent cell proliferation is surprisingly not affected in mice lacking c-jun in intestinal epithelium, suggesting that c-Jun is not an essential immediate target of beta-catenin signaling in the small intestine. To examine the functions of Jun and Fos proteins during inflammation and cancer in the colon, colitis-associated tumors were induced chemically in the respective knockout mice. Tumors were characterized by activated beta-catenin and strongly expressed c-Jun and JunB. However, tumorigenesis was not affected by inactivation of c-Jun in either intestinal epithelium or myeloid cells. Moreover, tumorigenesis was not altered in mice lacking junB, junD, c-fos, fra-1 or fra-2, suggesting that inhibition of c-Jun or other single AP-1 proteins is not a determining factor in colitis-associated cancer in mice.

Related: APC Signal Transduction CTNNB1 gene

Eferl R, Hasselblatt P, Rath M, et al.
Development of pulmonary fibrosis through a pathway involving the transcription factor Fra-2/AP-1.
Proc Natl Acad Sci U S A. 2008; 105(30):10525-30 [PubMed] Free Access to Full Article Related Publications
Studies using genetically modified mice have revealed fundamental functions of the transcription factor Fos/AP-1 in bone biology, inflammation, and cancer. However, the biological role of the Fos-related protein Fra-2 is not well defined in vivo. Here we report an unexpected profibrogenic function of Fra-2 in transgenic mice, in which ectopic expression of Fra-2 in various organs resulted in generalized fibrosis with predominant manifestation in the lung. The pulmonary phenotype was characterized by vascular remodeling and obliteration of pulmonary arteries, which coincided with expression of osteopontin, an AP-1 target gene involved in vascular remodeling and fibrogenesis. These alterations were followed by inflammation; release of profibrogenic factors, such as IL-4, insulin-like growth factor 1, and CXCL5; progressive fibrosis; and premature mortality. Genetic experiments and bone marrow reconstitutions suggested that fibrosis developed independently of B and T cells and was not mediated by autoimmunity despite the marked inflammation observed in transgenic lungs. Importantly, strong expression of Fra-2 was also observed in human samples of idiopathic and autoimmune-mediated pulmonary fibrosis. These findings indicate that Fra-2 expression is sufficient to cause pulmonary fibrosis in mice, possibly by linking vascular remodeling and fibrogenesis, and suggest that Fra-2 has to be considered a contributing pathogenic factor of pulmonary fibrosis in humans.

Related: IGF1 IL4 Cancer Prevention and Risk Reduction

Adiseshaiah P, Li J, Vaz M, et al.
ERK signaling regulates tumor promoter induced c-Jun recruitment at the Fra-1 promoter.
Biochem Biophys Res Commun. 2008; 371(2):304-8 [PubMed] Free Access to Full Article Related Publications
Fra-1 as an integral part of AP-1 (Jun/Fos) drives transcriptional programs involved in several physiologic and pathologic processes. It is also critical for tumor cell motility and metastasis. We have previously shown that two critical elements of Fra-1 promoter, the upstream TPA response element (TRE) and the serum response element (SRE), are necessary for its induction in response to phorbol esters in human pulmonary epithelial cell lines. Here, we have investigated the roles of various MAP kinases in regulating Fra-1 expression in response to TPA. Using pharmacologic and genetic tools, we demonstrate a prominent role for ERK1/2, but not JNK1/2 and p38, signaling in the TPA-induced activation of specific transcription factors that bind to the AP1 site and the SRE. Inhibition of ERK1/2 pathway suppresses Elk1 activation, and c-Jun and Fra-2 recruitment to the promoter.

Related: Cancer Prevention and Risk Reduction Signal Transduction

de Wilde J, De-Castro Arce J, Snijders PJ, et al.
Alterations in AP-1 and AP-1 regulatory genes during HPV-induced carcinogenesis.
Cell Oncol. 2008; 30(1):77-87 [PubMed] Related Publications
BACKGROUND: Previous studies demonstrated a functional involvement of the AP-1 transcription factor in HPV-induced cervical carcinogenesis. Here, we aimed to obtain further insight in expression alterations of AP-1 family members during HPV-mediated transformation and their relationship to potential regulatory (Notch1, Net) and target (CADM1) genes.
METHODS: mRNA expression levels of c-Jun, JunB, junD, c-Fos, FosB, Fra-1, Fra-2, Notch1, Net and CADM1 were determined by quantitative RT-PCR in primary keratinocytes (n=5), early (n=4) and late (n=4) passages of non-tumorigenic HPV-immortalized keratinocytes and in tumorigenic cervical cancer cell lines (n=7). In a subset of cell lines protein expression and AP-1 complex composition was determined.
RESULTS: Starting in immortal stages c-Fos, Fra-2 and JunB expression became up regulated towards tumorigenicity, whereas Fra-1, c-Jun, Notch1, Net and CADM1 became down regulated. The onset of deregulated expression varied amongst the AP-1 members and was not directly related to altered Notch1, Net or CADM1 expression. Nevertheless, a shift in AP-1 complex composition from Fra-1/c-Jun to c-Fos/c-Jun heterodimers was only observed in tumorigenic cells.
CONCLUSION: HPV-mediated transformation is associated with altered AP-1, Notch1, Net and CADM1 transcription. Whereas the onset of deregulated expression of various AP-1 family members became already manifest during the immortal state, a shift in AP-1 complex composition appeared a rather late event associated with tumorigenicity.

Related: Cervical Cancer

Yang S, Misner B, Chiu R, Meyskens FL
Common and distinct mechanisms of different redox-active carcinogens involved in the transformation of mouse JB6P+ cells.
Mol Carcinog. 2008; 47(7):485-91 [PubMed] Related Publications
We transformed JB6P+ cells with prolonged intermittent low-dose UVB radiation or prolonged exposure to low-dose H(2)O(2) or CdCl(2). Stable transformation was confirmed by an anchorage-independence assay. The JB6P+ transformants formed more colonies (approximately six folds) in soft agar as compared to their JB6P+ parent cells and were associated with increased intracellular reactive oxygen species (ROS) levels. Activating protein-1 (AP-1) is a family of transcription factors that are rapidly activated by elevated intracellular ROS levels, and their composition is important in the process of cellular transformation and/or tumor progression. To investigate if carcinogenesis induced by distinct carcinogens was via similar molecular mechanisms in these transformants, gel mobility shift and immunoblot analyses were utilized to determine the distinct AP-1 compositions. Compared to parent JB6P+ cells, the gain of JunB and Fra-1 in AP-1 DNA binding complexes was markedly increased in all transformed cells, which might contribute to a more proliferative phenotype, while loss of Fra-2 occurred in JB6P+/H(2)O(2) and JB6P+/Cd cells. Differential AP-1 components in the transformants suggested that their transformations might be mediated by distinct transcription signalings with distinct AP-1 dimer compositions. However, all three transformants exhibited increased activation of pathways involved in cell proliferation (ERK/Fra-1/AP-1 and JNK/c-jun/AP-1) and anti-apoptosis (Bcl-xl). The development of the JB6P+ transformants (JB6P+/UVB; JB6P+/H(2)O(2); JB6P+/Cd) provides a unique tool to study the mechanisms that contribute to different redox-active carcinogens in a single model.


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