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P63, a p53 family member, is expressed as TA and ΔN isoforms. Interestingly, both TAp63 and ΔNp63 are transcription factors, and regulate both common and distinct sets of target genes. p63 is required for survival of some epithelial cell lineages, and lack of p63 leads to loss of epidermis and other epithelia in humans and mice. Here, we explored the role of p63 isoforms in cell proliferation, migration and tubulogenesis by using Madin-Darby Canine Kidney (MDCK) tubular epithelial cells in two- or three-dimensional (2-D or 3-D) culture. We found that like downregulation of p53, downregulation of p63 and TAp63 decreases expression of growth-suppressing genes, including p21, PUMA and MIC-1, and consequently promotes cell proliferation and migration in 2-D culture. However, in 3-D culture, downregulation of p63, especially TAp63, but not p53, decapacitates MDCK cells to form a cyst structure through enhanced epithelial-to-mesenchymal transition (EMT). In contrast, downregulation of ΔNp63 inhibits MDCK cell proliferation and migration in 2-D culture, and delays but does not block MDCK cell cyst formation and tubulogenesis in 3-D culture. Consistent with this, downregulation of ΔNp63 markedly upregulates growth-suppressing genes, including p21, PUMA and MIC-1. Taken together, these data suggest that TAp63 is the major isoform required for tubulogenesis by maintaining an appropriate level of EMT, whereas ΔNp63 fine-tunes the rate of cyst formation and tubulogenesis by maintaining an appropriate expression level of genes involved in cell cycle arrest and apoptosis. [ABSTRACT FROM AUTHOR]

Caudal-related homeobox 1 (CDX1), an intestinal-specific transcription factor, has been reported to have vital roles in gastric intestinal metaplasia (IM). Although IM is a high-risk factor for gastric cancer (GC), the specific role of CDX1 in GC is largely unknown. In this study, we investigated the expression of CDX1 and its functional roles in GC, and its upstream regulatory mechanisms at the microRNA (miRNA) level were further explored. We found that CDX1 is lost in GC when compared with adjacent IM tissues. Gain-of-function studies showed that CDX1 significantly inhibited GC cell growth by inducing cell cycle arrest and apoptosis. Interestingly, we identified and verified an onco-mir, miR-296-5p, as a direct upstream regulator of CDX1. miR-296-5p overexpression significantly promoted GC cell growth and attenuated the CDX1-induced anti-growth effects by recurring cell cycle distribution and apoptotic status, whereas knockdown of miR-296-5p decreased GC cell growth. Furthermore, we found that the extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation and the subsequent downstream changes in protein levels related to cell cycle and apoptosis partly account for the miR-296-5p-CDX1-induced GC growth promotion. In addition, the detection of miR-296-5p and expression of CDX1 in primary GC tissues and adjacent IM tissues revealed that miR-296-5p is inversely correlated with CDX1, further supporting our in vitro results. Our results showed an anti-growth effect of CDX1 and identified its miRNA regulatory mechanism in GC. The identification of this novel miR-296-5p-CDX1-ERK1/2 axis sheds new light on the understanding of the process from IM to GC and may provide therapeutic targets for the treatment of GC. [ABSTRACT FROM AUTHOR]

The transcription factor E2F1 has pivotal roles in both cell proliferation and cell death, and is an important molecular target in cancer. Under proliferative conditions E2F1 induces the expression of genes that promote cell cycle progression, such as E2F2, whereas under proapoptotic conditions E2F1 induces expression of genes such as p73 that lead to apoptosis. The mechanism by which the apoptotic function of E2F1 is activated remains unclear, however. We now show that members of the E2F family are covalently conjugated with the ubiquitin-like modifier NEDD8. Overexpression of SENP8, a NEDD8-specific cysteine protease, resulted in deNEDDylation of E2F1 and promoted its transactivation activity at the p73 gene but not at the E2F2 gene. Knockdown of SENP8, on the other hand, attenuated p73 expression and apoptosis induced by E2F1 or by DNA damage. SENP8 also promoted the interaction between E2F1 and its cofactor Microcephalin 1, which is required for p73 induction. These results suggest that NEDDylation is a molecular trigger that modifies the target specificity of E2F1, and could have important implications for E2F1 regulation of apoptosis. [ABSTRACT FROM AUTHOR]

FoxO transcription factors are an evolutionary conserved subfamily of the forkhead transcription factors, characterized by the forkhead DNA-binding domain. FoxO factors regulate a number of cellular processes involved in cell-fate decisions in a cell-type- and environment-specific manner, including metabolism, differentiation, apoptosis and proliferation. A key mechanism by which FoxO determines cell fate is through regulation of the cell cycle machinery, and as such the cellular consequence of FoxO deregulation is often manifested through perturbation of the cell cycle. Consequently, the deregulation of FoxO factors is implicated in the development of numerous proliferative diseases, in particular cancer.Oncogene (2008) 27, 2300–2311; doi:10.1038/onc.2008.23 [ABSTRACT FROM AUTHOR]

FOXO (Forkhead box O) transcription factors are involved in cell-cycle arrest or apoptosis induction by transcripting cell-cycle inhibitor p27KIP1 or apoptosis-related genes, respectively. Akt/protein kinase B promotes cell proliferation and suppresses apoptosis, in part, by phosphorylating FOXOs. Phosphorylated FOXOs could not exhibit transcriptional activity because of their nuclear export. Here we show that p15INK4b and p19INK4d transcription is associated with FOXO-mediated G1 cell-cycle arrest. Inhibition of Akt signaling by PI3K inhibitors, a PDK1 inhibitor, or dominant-negative Akt transfection increased expression of p15INK4b and p19INK4d but not p16INK4a and p18INK4c. Ectopic expression of wild type or active FOXO but not inactive form also increased p15INK4b and p19INK4d levels. FOXOs bound to promoter regions and induced transcription of these genes. No increase in the G1-arrested cell population, mediated by PI3K inhibitor LY294002, was observed in INK4b−/− or INK4d−/− murine embryonic fibroblasts. In summary, FOXOs are involved in G1 arrest caused by Akt inactivation via p15INK4b and p19INK4d transcription.Oncogene (2008) 27, 1677–1686; doi:10.1038/sj.onc.1210813; published online 17 September 2007 [ABSTRACT FROM AUTHOR]

The paired/homeodomain transcription factor Pax4 is essential for islet β-cell generation during pancreas development and their survival in adulthood. High Pax4 expression was reported in human insulinomas indicating that deregulation of the gene may be associated with tumorigenesis. We report that rat insulinoma INS-1E cells express 25-fold higher Pax4 mRNA levels than rat islets. In contrast to primary β-cells, activin A but not betacellulin or glucose induced Pax4 mRNA levels indicating dissociation of Pax4 expression from insulinoma cell proliferation. Short hairpin RNA adenoviral constructs targeted to the paired domain or homeodomain (viPax4PD and viPax4HD) were generated. Pax4 mRNA levels were lowered by 73 and 50% in cells expressing either viPax4PD or viPax4HD. Transcript levels of the Pax4 target gene bcl-xl were reduced by 53 and 47%, whereas Pax6 and Pdx1 mRNA levels were unchanged. viPax4PD-infected cells displayed a twofold increase in spontaneous apoptosis and were more susceptible to cytokine-induced cell death. In contrast, proliferation was unaltered. RNA interference-mediated repression of insulin had no adverse effects on either Pax4 or Pdx1 expression as well as on cell replication or apoptosis. These results indicate that Pax4 is redundant for proliferation of insulinoma cells, whereas it is essential for survival through upregulation of the antiapoptotic gene bcl-xl.Oncogene (2007) 26, 4261–4271; doi:10.1038/sj.onc.1210205; published online 29 January 2007 [ABSTRACT FROM AUTHOR]

The path to the discovery of suberoylanilide hydroxamic acid (SAHA, vorinostat) began over three decades ago with our studies designed to understand why dimethylsulfoxide causes terminal differentiation of the virus-transformed cells, murine erythroleukemia cells. SAHA can cause growth arrest and death of a broad variety of transformed cells both in vitro and in vivo at concentrations that have little or no toxic effects on normal cells. It was discovered that SAHA inhibits the activity of histone deacetylases (HDACs), including all 11 known human class I and class II HDACs. HDACs have many protein targets whose structure and function are altered by acetylation including histones and non-histone proteins component of transcription factors controlling gene expression and proteins that regulate cell proliferation, migration and death. SAHA is in clinical trials and has significant anticancer activity against both hematologic and solid tumors at doses well tolerated by patients. A new drug application has been approved for SAHA (vorinostat) treatment of cutaneous T-cell lymphoma.Oncogene (2007) 26, 1351–1356. doi:10.1038/sj.onc.1210204 [ABSTRACT FROM AUTHOR]

The cytoskeleton is a dynamic network that undergoes restructuring during various cellular events, influencing cell proliferation, differentiation, and apoptosis. Here, we report that accumulation of c-Jun, a member of the AP1 family of transcription factors that play a key role in normal and aberrant cell growth, dramatically increases upon depolymerization of the cytoskeleton, and that, unexpectedly, this increase is controlled translationally. Depolymerization of the actin or microtubule network induces an increase in c-Jun accumulation with no corresponding increase in c-Jun mRNA or in the half-life of the c-Jun protein, but rather in the translatability of its transcript. This increase is mediated by the untranslated regions (UTRs) of c-Jun mRNA, and is not dependent on activated mitogen-activated protein kinase pathways. This novel mechanism of c-Jun regulation might be relevant to physiological conditions in which c-Jun plays a pivotal role.Oncogene (2006) 25, 665–676. doi:10.1038/sj.onc.1209114; published online 10 October 2005 [ABSTRACT FROM AUTHOR]

The proto-oncoprotein c-Myc functions as a transcriptional regulator that controls different aspects of cell behavior, including proliferation, differentiation, and apoptosis. In addition, Myc proteins have the potential to transform cells and are deregulated in the majority of human cancers. Several Myc-interacting factors have been described that mediate part of Myc's functions in the control of cell behavior. Here, we describe the isolation of a novel 150?kDa protein, designated PARP-10, that interacts with Myc. PARP-10 possesses domains with homology to RNA recognition motifs and to poly(ADP-ribose) polymerases (PARP). Molecular modeling and biochemical analysis define a PARP domain that is capable of ADP-ribosylating PARP-10 itself and core histones, but neither Myc nor Max. PARP-10 is localized to the nuclear and cytoplasmic compartments that is controlled at least in part by a Leu-rich nuclear export sequence (NES). Functionally, PARP-10 inhibits c-Myc- and E1A-mediated cotransformation of rat embryo fibroblasts, a function that is independent of PARP activity but that depends on a functional NES. Together, our findings define a novel PARP enzyme involved in the control of cell proliferation.Oncogene (2005) 24, 1982-1993. doi:10.1038/sj.onc.1208410 Published online 17 January 2005 [ABSTRACT FROM AUTHOR]

Runx transcription factors regulate viral growth, hematopoiesis, bone formation, angiogenesis, and gastric epithelial development through specific DNA-binding motifs on target gene promoters. Vascular endothelial cells (ECs) express RUNX genes that are activated by angiogenic factors. The RUNX2 gene also activates the vascular endothelial growth factor promoter. Alternatively spliced forms of RUNX genes have been described, but their functions in angiogenesis have not been elucidated. In this study, expression of a novel alternatively spliced variant of RUNX2 (RUNX2?8), lacking the region encoded by exon 8, was detected in aortic tissue undergoing angiogenesis in vitro and in ECs. Expression of RUNX2 and RUNX2?8 increased in vascular sprouts concomitant with expression of cellular proteases and cytokines known to mediate angiogenesis. RUNX2 DNA-binding activity was expressed in proliferating but not quiescent ECs. Ectopic expression of RUNX2 in ECs increased cell sprouting, cell proliferation, DNA synthesis, and phosphorylation of phosphorylated retinoblastoma relative to control transfectants while RUNX2, but not RUNX2?8 transfectants, acquired resistance to growth inhibition by transforming growth factor (TGFß1). Furthermore, RUNX2?8-transfected cells were more sensitive to TGFß1-induced apoptosis than RUNX2 transfectants. Consistent with these data, the RUNX2 gene was a strong repressor of the promoter of the cyclin-dependent kinase inhibitor, p21CIP1, while RUNX2?8 was a competitive inhibitor of RUNX2 and exhibited weak repression activity. These results support the hypothesis that ECs regulate growth and apoptosis, in part, by alternative splicing events in the RUNX2 transcription factor to affect the TGFß1 signaling pathway. The exon 8 domain of RUNX2 may contribute to the strong repression activity of RUNX2 for some target gene promoters.Oncogene (2004) 23, 4722-4734. doi:10.1038/sj.onc.1207589 Published online 26 April 2004 [ABSTRACT FROM AUTHOR]

c-Myc promotes cellular proliferation, sensitizes cells to apoptosis and prevents differentiation. It binds cyclin T1 structurally and functionally from the positive transcription elongation factor b (P-TEFb). The cyclin-dependent kinase 9 (Cdk9) in P-TEFb then phosporylates the C-terminal domain of RNA polymerase II, which is required for the transition from initiation to elongation of eukaryotic transcription. Inhibiting P-TEFb blocks the transcription of its target genes as well as cellular proliferation and apoptosis induced by c-Myc.Oncogene (2003) 22, 5707-5711. doi:10.1038/sj.onc.1206800 [ABSTRACT FROM AUTHOR]

Presents a study that investigated the differential activity of nuclear cofactors in mediating oncogenic transformation by both the Myc and E2F transcription factors. Background on the Myc and E2F transcription factors; Information on the activities of nuclear cofactors in apoptosis; Analysis of the biological activities of the c-Myc and E2F1 transcription factors, including oncogenesis and cell proliferation.

Rel/NF-κB transcription factors are key regulators of immune, inflammatory and acute phase responses and are also implicated in the control of cell proliferation and apoptosis. Remarkable progress has been made in understanding the signal transduction pathways that lead to the activation of Rel/NF-κB factors and the consequent induction of gene expression. Evidence linking deregulated Rel/NF-κB activity to oncogenesis in mammalian systems has emerged in recent years, consistent with the acute oncogenicity of the viral oncoprotein v-Rel in animal models. Chromosomal amplification, overexpression and rearrangement of genes coding for Rel/NF-κB factors have been noted in many human hematopoietic and solid tumors. Persistent nuclear NF-κB activity was also described in several human cancer cell types, as a result of constitutive activation of upstream signaling kinases or mutations inactivating inhibitory IκB subunits. Studies point to a correlation between the activation of cellular gene expression by Rel/NF-κB factors and their participation in the malignant process. Experiments implicating NF-κB in the control of the apoptotic response also support a role in oncogenesis and in the resistance of tumor cells to chemotherapy. This review focuses on the status of the rel, nfkb and ikb genes and their activity in human tumors and their association with the onset or progression of malignancies. [ABSTRACT FROM AUTHOR]

IN CELL CULTURE STUDIES, OVEREXPRESSION OF THE E2F1 TRANSCRIPTION FACTOR HAS BEEN SHOWN TO STIMULATE PROLIFERATION, INDUCE APOPTOSIS, AND COOPERATE WITH AN ACTIVATED RAS: gene to oncogenically transform primary rodent cells. To study the effect of increased E2F1 activity on epithelial growth and tumorigenesis in vivo, transgenic mice expressing E2F1 under the control of a keratin 5 (K5) promoter were generated. Expression of E2F1 in the epidermis results in hyperplasia but does not inhibit terminal differentiation. In a transgenic line expressing high levels of E2F1, mice have decreased hair growth likely as a result of aberrant apoptosis in developing hair follicles. Coexpression of a cyclin D1 transgene with E2F1 augments epidermal hyperplasia and further disrupts hair follicle development suggesting that hypophosphorylated Rb antagonizes the proliferative and apoptotic-promoting activities of E2F1. Finally, the E2F1 transgene is found to cooperate with a v-Ha-ras transgene to induce skin tumors in double transgenic animals. These findings confirm that many of the activities ascribed to E2F1 through in vitro studies can be reproduced in vivo and demonstrate for the first time that deregulated E2F activity can contribute to tumor development. [ABSTRACT FROM AUTHOR]

Interferon Regulatory Factor (IRF)-1 has been characterized as an important growth regulatory and immunomodulatory transcription factor. To further characterize the potential targets of IRF-1 antiproliferative activity, IRF-1 was expressed under the control of the tetracycline-inducible system in murine NIH3T3 cells. Due to their ability to mimic IRF-1 transactivator function, the regulatory potential of IRF-1/RelA and IRF-2/RelA fusion proteins consisting of the DNA binding domains of IRF-1 or IRF-2 fused to the transactivation domain of NF-κB RelA(p65) was also examined. Cells inducibly expressing IRF-1 or IRF/RelA in response to doxycycline treatment displayed significantly reduced growth rates compared to control cells, and inhibition of cell growth correlated directly with the level of transgene expression. Interestingly, IRF-1 and IRF/RelA expression also induced a low level of apoptosis, as detected by microscopic analyses. Furthermore, expression of the interferon inducible, double stranded RNA dependent kinase PKR was increased following IRF-1 or IRF/RelA induction. Most strikingly, induction of IRF-1 and IRF/RelA expression resulted in a significant increase in STAT1 (p91) protein and increased ISGF3 DNA binding activity, suggesting that IRF-1 tumor suppressor activity may involve a novel mechanism which activates the JAK-STAT pathway through STAT1. WAF1 levels were also constitutively elevated in IRF-1 and IRF-1/RelA cells. These studies demonstrate that inducible expression of the transactivation function of IRF-1 or IRF/RelA mediates tumor suppressor activity by inducing cell growth arrest, apoptosis and the differential activation of growth regulatory genes such as PKR, STAT1 and WAF1. [ABSTRACT FROM AUTHOR]