Alteration of jun proto-oncogene status by plasmid transfection affects growth of human ovarian cancer cells

c-Jun transcriptionally regulates alpha 1, 2-fucosyltransferase 1 (FUT1) in ovarian cancer

Alpha 1, 2-fucosyltransferase (FUT 1/2) is a rate-limiting enzyme that catalyzes the synthesis of Lewis y, a cell membrane-associated carbohydrate antigen. In human ovarian cancer, the upregulated expression of FUT1 and Lewis y is associated with advanced pathological stages and involved in cell proliferation, migration and invasion. However, the mechanism underlying the upregulation of FUT1 is largely unknown. Here, we identify an AP-1 binding site in FUT1 promoter in ovarian cancer cells. c-Jun promotes FUT1 expression, thereby enhancing Lewis y biosynthesis in various ovarian cancer cell lines. Moreover, EMSA, luciferase activity and ChIP assays demonstrate c-Jun directly interacts with FUT1 promoter. Furthermore, FUT1 mediates c-Jun-induced cell proliferation in ovarian cancer cells. In human ovarian cancer samples, c-Jun overexpression is linked to malignant degree and positively correlated to FUT1 and Lewis y expression. Taken together, c-Jun could transcriptionally modulate FUT1 expression in ovarian cancer, implicating the potential application of c-Jun inhibitors for human ovarian cancer therapy.

The Extracts of Some Marine Invertebrates and Algae Collected off the Coast Waters of Vietnam Induce the Inhibitory Effects on the Activator Protein-1 Transcriptional Activity in JB6 Cl41 Cells

It has previously been shown that inhibition of the transcriptional activity of the oncogenic nuclear factor AP-1 can result in cancer prevention. Marine invertebrates and alga are a rich source of natural compounds that possess various biological activities. The inhibitory effects of the extracts of Vietnamese marine organisms in relation to the AP-1 transcriptional activity were examined by the luciferase method using JB6 Cl41 cells stably expressing a luciferase reporter gene controlled by AP-1 DNA binding sequence. As was found, 71 species of marine sponges out of 148 species studied contain inhibitors of the AP-1 transcriptional activity. Therefore, marine organisms as a source of biologically active compounds have a great potential for isolation of the new cancer preventive compounds that inhibit the oncogenic AP-1 nuclear factor.

Inhibition of AP-1 suppresses cervical cancer cell proliferation and is associated with p21 expression

AP-1, a transcription factor comprised primarily of Jun and Fos family proteins, regulates genes involved in proliferation, differentiation and oncogenesis. Previous studies demonstrated that elevated expression of Jun and Fos family member proteins is associated with numerous human cancers and in cancer-relevant biological processes. In this study we used a dominant-negative mutant of c-Jun, Tam67, which interferes with the functional activity of all AP-1 complexes, to investigate the requirement of AP-1 in the proliferation and cell cycle progression of cervical cancer cells. Transient and stable expression of Tam67 in CaSki cervical cancer cells resulted in decreased AP-1 activity that correlated with a significant inhibition of cell proliferation and anchorage-independent colony formation. Inhibiting AP-1 activity resulted in a two-fold increase in cells located in the G2/M phase of the cell cycle and an accompanying increase in the expression of the cell cycle regulatory protein, p21. The increase in p21 was associated with a decrease in HPV E6 expression and an increase in p53. Importantly, blocking the induction of p21 in CaSki-Tam67-expressing cells accelerated their proliferation rate to that of CaSki, implicating p21 as a key player in the growth arrest induced by Tam67. Our results suggest a role for AP-1 in the proliferation, G2/M progression and inhibition of p21 expression in cervical cancer.

Regulation of the Rhox5 Homeobox Gene in Primary Granulosa Cells: Preovulatory Expression and Dependence on SP1/SP3 and GABP1

Homeobox genes encode transcription factors that regulate embryonic development and postnatal events. Rhox5 (previously called Pem), the founding member of a homeobox gene cluster that we recently identified on the X chromosome, is selectively expressed in granulosa cells in the ovary and other somatic-cell types in other reproductive organs. In this report, we investigate its regulation in granulosa cells in the rat ovary. We found that Rhox5 expression in the ovary is governed by the Rhox5 distal promoter and is expressed at least as early as Day 5 postpartum. Rhox5 mRNA levels are regulated during the ovarian cycle, peaking before ovulation. Deletion analysis revealed a 25-nt element essential for distal promoter transcription in primary granulosa cells. This distal promoter element contains two ETS and one SP1 transcription-factor family binding sites that mutagenesis analysis indicated were essential for high-level transcription. This element was both necessary and sufficient for transcription, because it activated transcription when placed upstream of a heterologous minimal promoter. Cold competition and electrophoretic mobility shift assay studies demonstrated that SP1, SP3, and the ETS family transcription factor GABP bound this element. Dominant-negative forms of GABP and SP3 repressed distal promoter expression in primary rat granulosa, showing that these factors are crucial for Rhox5 expression. Cotransfection of dominant-negative mutants indicated that Rhox5 expression in granulosa cells is regulated by the c-Jun N-terminal protein kinase (JNK, MAPK8) and RAS pathways, which are known to be upstream of ETS family transcription factors. The discovery that Rhox5 expression in granulosa cells is regulated by MAPK pathways and ETS and SP1 family members provides an opportunity to understand how these regulatory pathways and factors collaborate to regulate gene expression during the ovarian cycle.

Spindlin1, a novel nuclear protein with a role in the transformation of NIH3T3 cells

spindlin1, a novel human gene recently isolated by our laboratory, is highly homologous to mouse spindlin gene. In this study, we cloned cDNA full-length of this novel gene and send it to GenBank database as spindlin1 (Homo sapiens spindlin1) with Accession No. AF317228. In order to investigate the function of spindlin1, we studied further the subcellular localization of Spindlin1 protein and the effects of spindlin1 overexpression in NIH3T3 cells. The results showed that the fusion protein pEGFP-N1-spindlin1 was located in the nucleus and the C-terminal is correlated with nuclear localization of Spindlin1 protein. NIH3T3 cells which could stably express spindlin1 as a result of RT-PCR analysis compared with the control cells displayed a complete morphological change; made cell growth faster; and increased the percentage of cells in G2/M and S phase. Furthermore, overexpressed spindlin1 cells formed colonies in soft agar in vitro and formed tumors in nude mice. Our findings provide direct evidence that spindlin1 gene may contribute to tumorigenesis.

Jun, the oncoprotein

Cellular Jun (c-Jun) and viral Jun (v-Jun) can induce oncogenic transformation. For this activity, c-Jun requires an upstream signal, delivered by the Jun N-terminal kinase (JNK). v-Jun does not interact with JNK; it is autonomous and constitutively active. v-Jun and c-Jun address overlapping but not identical sets of genes. Whether all genes essential for transformation reside within the overlap of the v-Jun and c-Jun target spectra remains to be determined. The search for transformation-relevant targets of Jun is moving into a new stage with the application of DNA microarrays technology. Genetic screens and functional tests remain a necessity for the identification of genes that control the oncogenic phenotype.

Induction of T cell responses against autologous ovarian tumors with whole tumor cell lysate-pulsed dendritic cells

The loading of dendritic cells (DCs) with whole tumor cell lysates may circumvent the facts that few tumor-specific antigens have been identified in human solid tumors. The present study was designed to investigate whether ovarian cancer cells lysate-pulsed DCs activate T cell responses against autologous ovarian tumors. Incubation of T cells with autologous tumor cell lysate-pulsed DCs stimulated proliferation of autologous T cells. T cells primed by autologous tumor cell lysate-pulsed DCs showed significant killing activity against autologous tumor cells, which could be blocked by anti-MHC-class-I and anti-CD8 mAb. By contrast, T cells primed by autologous unpulsed DCs alone or tumor lysates alone failed to exhibit significant killing activity. In addition, T cells primed by DCs pulsed with allogeneic tumor cell lysates or with autologous normal cell lysate or by these cell lysates alone did not induce the increase in the autologous tumor killing activity. As additional controls, T cells stimulated with autologous tumor lysate-pulsed DCs express no increase in the lysis of autologous monocytes, allogeneic ovarian tumor cells and other cell lines including K562, Daudi and Molt-4. Furthermore, T cells stimulated with autologous tumor lysate-pulsed DCs could produce the considerable amounts of cytokines such as GM-CSF, TNF-alpha and IFN-gamma. The data in the present study suggest that whole tumor cell lysates-pulsed DCs could activate T cell responses against autologous ovarian tumor cells, and that these pulsed DCs may be used as a new approach for the specific immunotherapy of ovarian cancer patients.

Endogenous AP-1 levels necessary for oncogenic activity are higher than those sufficient to support normal growth

We investigated the role of endogenous AP-1 in human tumor cell lines by introducing SupJunD-1, a dominant-negative mutant of AP-1, using vesicular stomatitis virus G protein (VSV-G)-pseudotyped retrovirus vectors. Single inoculation of six human tumor cell lines, originating from osteosarcomas, non-small cell lung carcinomas or cervical carcinomas, with recombinant SupJunD-1 virus at a high multiplicity of infection readily inhibited colony formation in soft agar. We detected no significant changes in expression levels of AP-1 components c-Jun or Fra-1, adhesion molecules CD44 or E-cadherin, or cell cycle regulator p53, which are encoded by genes previously reported to be under the control of AP-1 in some mouse or human cell lines. By varying the dosage of VSV-G-pseudotyped retrovirus, we were able to change the proviral copy number of supjunD-1 from 1 to approximately 10 and monitor suppression of endogenous AP-1 function as assessed by growth characteristics of the tumor cell lines, we found a SupJunD-1 dosage which significantly suppressed anchorage-independent growth without affecting the cellular growth in monolayer cultures at all. We conclude that endogenous AP-1 levels necessary for oncogenic activity are much higher than those sufficient to support normal growth.

Regulation of AP1 (Jun/Fos) factor expression and activation in ovarian granulosa cells. Relation of JunD and Fra2 to terminal differentiation

AP1 transcription factors control rapid responses of mammalian cells to stimuli that impact proliferation, differentiation, and transformation. To determine which AP1 factors are present in and regulated by hormones in ovarian cells during specific stages of proliferation and differentiation, we used both in vitro and in vivo models, Western blotting, immunohistochemistry, DNA binding assays, and transfections of AP1 promoter-reporter constructs. The expression patterns of Jun and Fos family members in response to hormones (follicle-stimulating hormone (FSH), luteinizing hormone (LH), and cAMP) were distinct. JunB, c-Jun, c-Fos, and Fra2 were rapidly but transiently induced by FSH in immature granulosa cells. JunD and Fra2 were induced by LH and maintained as granulosa cells terminally differentiated into luteal cells. Forskolin and phorbol myristate acetate acted synergistically to enhance transcription of an AP1(-73COL)-luciferase construct. JunD appears to be one mediator of this effect, since JunD was a major component of the AP1-DNA binding complex in granulosa cells, and menin, a selective inhibitor of JunD, blocked transcription of -73COL-luciferase. Thus, FSH and LH via cAMP induce specific AP1 factors, the AP1 expression patterns are distinct, and that of JunD and Fra2 correlates with the transition of proliferating granulosa cells to terminally differentiated, non-dividing luteal cells.