Suppression of invasion and peritoneal carcinomatosis of ovarian cancer cells by overexpression of AP-2alpha

Crucial role of the transcription factors family activator protein 2 in cancer: current clue and views

The transcription factor family activator protein 2 (TFAP2) is vital for regulating both embryonic and oncogenic development. The TFAP2 family consists of five DNA-binding proteins, including TFAP2A, TFAP2B, TFAP2C, TFAP2D and TFAP2E. The importance of TFAP2 in tumor biology is becoming more widely recognized. While TFAP2D is not well studied, here, we mainly focus on the other four TFAP2 members. As a transcription factor, TFAP2 regulates the downstream targets directly by binding to their regulatory region. In addition, the regulation of downstream targets by epigenetic modification, posttranslational regulation, and interaction with noncoding RNA have also been identified. According to the pathways in which the downstream targets are involved in, the regulatory effects of TFAP2 on tumorigenesis are generally summarized as follows: stemness and EMT, interaction between TFAP2 and tumor microenvironment, cell cycle and DNA damage repair, ER- and ERBB2-related signaling pathway, ferroptosis and therapeutic response. Moreover, the factors that affect TFAP2 expression in oncogenesis are also summarized. Here, we review and discuss the most recent studies on TFAP2 and its effects on carcinogenesis and regulatory mechanisms.

Identification and Functional Validation of Differentially Expressed microRNAs in Ascites-Derived Ovarian Cancer Cells Compared with Primary Tumour Tissue

Purpose

Ovarian cancer, manifested by malignant ascites, is the most lethal gynaecological cancer. Suspended ascites-derived spheroids may contribute to ovarian cancer metastasis. MicroRNAs (miRNAs) are also associated with ovarian cancer metastasis. Here, we aimed to investigate the differentially expressed miRNAs (DE-miRNAs) in ascites-derived spheroids compared with primary tumour tissues, which may regulate ovarian cancer metastasis.

Methods

The DE-miRNAs between ovarian cancer primary tumour tissues and ascites-derived spheroids were identified by GEO2R screening in samples from 3 high-grade serous ovarian cancer (HGSOC) patients of dataset GSE65819. We used MiRTarBase, TargetScanHuman7.2 and STRING to predict the target hub genes of DE-miRNAs and DAVID to perform functional analysis of hub genes. ALGGEN PROMO and TransmiR v2.0 were used to predict transcription factors (TFs) that potentially regulate DE-miRNAs expression. The observed differences in DE-miRNAs expression were validated with samples from 12 HGSOC patients and 2 ovarian cancer cell lines using PCR. The functions of DE-miRNAs on ovarian cancer progression were verified by invasion, adherent, and angiogenesis assays.

Results

Through bioinformatics screening and experimental validation, miR-199a-3p, miR-199b-3p, miR-199a-5p, miR-126-3p and miR-145-5p were identified as being significantly downregulated in ascites-derived spheroids compared with primary tumour tissues. In addition, TFAP2A was identified as a potentially common upstream TF regulating the expression of the above mentioned DE-miRNAs. The overexpression of miR-199a-3p, miR-199b-3p, miR-199a-5p lead to invasion inhibition, and the overexpression of miR-126-3p, miR-145-5p, miR-199a-5p and miR-199b-3p lead to adhesion inhibition of suspended ovarian cancer cells. High-expressed miR-126-3p, miR-199a-3p, miR-199a-5p and miR-199b-3p contributed to apoptosis of suspended ovarian cancer cells.

Conclusion

The downregulated expression of miR-199a-3p, miR-199b-3p, miR-199a-5p, miR-126-3p and miR-145-5p in ascites-derived spheroids plays a key role in promoting ovarian cancer progression, which may represent novel molecules for targeted therapy for ovarian cancer.

Identification of Tumor Microenvironment-Related Prognostic Biomarkers for Ovarian Serous Cancer 3-Year Mortality Using Targeted Maximum Likelihood Estimation: A TCGA Data Mining Study

Ovarian serous cancer (OSC) is one of the leading causes of death across the world. The role of the tumor microenvironment (TME) in OSC has received increasing attention. Targeted maximum likelihood estimation (TMLE) is developed under a counterfactual framework to produce effect estimation for both the population level and individual level. In this study, we aim to identify TME-related genes and using the TMLE method to estimate their effects on the 3-year mortality of OSC. In total, 285 OSC patients from the TCGA database constituted the studying population. ESTIMATE algorithm was implemented to evaluate immune and stromal components in TME. Differential analysis between high-score and low-score groups regarding ImmuneScore and StromalScore was performed to select shared differential expressed genes (DEGs). Univariate logistic regression analysis was followed to evaluate associations between DEGs and clinical pathologic factors with 3-year mortality. TMLE analysis was conducted to estimate the average effect (AE), individual effect (IE), and marginal odds ratio (MOR). The validation was performed using three datasets from Gene Expression Omnibus (GEO) database. Additionally, 355 DEGs were selected after differential analysis, and 12 genes from DEGs were significant after univariate logistic regression. Four genes remained significant after TMLE analysis. In specific, ARID3C and FREM2 were negatively correlated with OSC 3-year mortality. CROCC2 and PTF1A were positively correlated with OSC 3-year mortality. Combining of ESTIMATE algorithm and TMLE algorithm, we identified four TME-related genes in OSC. AEs were estimated to provide averaged effects based on the population level, while IEs were estimated to provide individualized effects and may be helpful for precision medicine.

Silencing of lncRNA DLEU1 inhibits tumorigenesis of ovarian cancer via regulating miR-429/TFAP2A axis

Long non-coding RNAs (lncRNAs) are known as crucial regulators in the development of OC. In the current study, we aim to explore the function and molecular mechanism of lncRNA DLEU1 in OC. Quantitative real-time polymerase chain reaction (qRT-PCR) was applied to determine the expression of DLEU1, miR-429, and TFAP2A in OC cells and tissues. The relationship among DLEU1, miR-429, and TFAP2A was tested by dual-luciferase reporter (DLR) assay. Besides, the proliferative, migratory and invasive abilities of OC cells were analyzed by MTT, wound healing, and transwell assays, respectively. Western blot was performed to determine the protein expression of TFAP2A. The expression of lncRNA DLEU1 and TFAP2A were upregulated, and miR-429 was downregulated in OC tissues. Silencing of DLEU1 inhibited the proliferation, migration, and invasion of OC cells. Bioinformation and DLR assay showed that DLEU1 acted as the sponge for miR-429. Moreover, miR-429 could directly target TFAP2A and inhibit the proliferation, migration, and invasion of OC cells. Moreover, we observed a negative correlation between miR-429 and DLEU1, and between miR-429 and TFAP2A in OC tissues. The transfection of miR-429 inhibitor or pcDNA-TFAP2A reversed the inhibitory effects of si-DLEU1 on the proliferation, migration, and invasion of OC cells. Silencing of DLEU1 inhibited the proliferation, migration, and invasion of OC cells by regulating miR-429/TFAP2A axis, indicating a potential therapeutic target for OC.

Transcription factor AP-2β suppresses cervical cancer cell proliferation by promoting the degradation of its interaction partner β-catenin

Transcription factor AP-2β mediates the transcription of a number of genes implicated in mammalian development, cell proliferation, and carcinogenesis. Although the expression pattern of AP-2β has been analyzed in cervical cancer cell lines, the functions and molecular mechanism of AP-2β are unknown. Here, we found that AP-2β significantly inhibits TCF/LEF reporter activity. Moreover, AP-2β and β-catenin interact both in vitro through GST pull-down assays and in vivo by co-immunoprecipitation. We further identified the interaction regions to the DNA-binding domain of AP-2β and the 1-9 Armadillo repeats of β-catenin. Moreover, AP-2β binds with β-TrCP and promotes the degradation of endogenous β-catenin via the proteasomal degradation pathway. Immunohistochemistry analysis revealed a negative correlation between the two proteins in cervical cancer tissues and cell lines. Finally, functional analysis showed that AP-2β suppresses cervical cancer cell growth in vitro and in vivo by inhibiting the expression of Wnt downstream genes. Taken together, these findings demonstrated that AP-2β functions as a novel inhibitor of the Wnt/β-catenin signaling pathway in cervical cancer.

Activating enhancer-binding protein-2α induces cyclooxygenase-2 expression and promotes nasopharyngeal carcinoma growth

Activating enhancer-binding protein-2α (AP-2α) regulates the expression of many cancer-related genes. Here, we demonstrated a novel mechanism by which AP-2α up-regulated cyclooxygenase-2 (COX-2) expression to promote the growth of nasopharyngeal carcinomas (NPCs). High expression of AP-2α in NPC cell lines and tumor tissues from NPC patients was detected and significantly correlated with COX-2 expression. Overexpression of AP-2α and COX-2 in tumor tissues was associated with advanced tumor stage, clinical progression, and short survival of patients with NPCs. Knockdown of AP-2α by siRNA markedly inhibited COX-2 expression and PGE2 production in NPC cells. Exogenous expression of AP-2α up-regulated the COX-2 and PGE2. Knockdown of AP-2α also significantly suppressed cell proliferation in NPC cells in vitro and tumor growth in a NPC xenograft mouse model. Moreover, we found that p300 played an important role in the AP-2α/COX-2 pathway. AP-2α could co-localize and interact with p300 in NPC cells. Overexpression of the p300, but not its histone acetyltransferase (HAT) domain deletion mutant, promoted the acetylation of AP-2α and its binding on the COX-2 promoter, thereby up-regulated COX-2 expression. Our results indicate that AP-2α activates COX-2 expression to promote NPC growth and suggest that the AP-2α/COX-2 signaling is a potential therapeutic target for NPC treatment.

Specificity protein 1 (Sp1) maintains basal epithelial expression of the miR-200 family: implications for epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is required for the specification of tissues during embryonic development and is recapitulated during the metastatic progression of tumors. The miR-200 family plays a critical role in enforcing the epithelial state with their expression lost in cells undergoing EMT. EMT can be mediated by activation of the ZEB1 and ZEB2 (ZEB) transcription factors, which repress miR-200 expression via a self-reinforcing double negative feedback loop to promote the mesenchymal state. However, it remains unclear what factors drive and maintain epithelial-specific expression of miR-200 in the absence of EMT-inducing factors. Here, we show that the transcription factor Specificity Protein 1 (Sp1) binds to the miR-200b∼200a∼429 proximal promoter and activates miR-200 expression in epithelial cells. In mesenchymal cells, Sp1 expression is maintained, but its ability to activate the miR-200 promoter is perturbed by ZEB-mediated repression. Reduction of Sp1 expression caused changes in EMT-associated markers in epithelial cells. Furthermore, we observed co-expression of Sp1 and miR-200 during mouse embryonic development wherein miR-200 expression was only lost in regions with high ZEB expression. Together, these findings indicate that miR-200 family members require Sp1 to drive basal expression and to maintain an epithelial state.

Synergistic silencing by promoter methylation and reduced AP-2α transactivation of the proapoptotic HRK gene confers apoptosis resistance and enhanced tumor growth

The Harakiri (HRK) gene encodes an important proapoptotic mitochondrial protein of the Bcl-2 family. HRK is expressed in normal tissues but is decreased in many cancers such as melanoma, the mechanisms of which have not been fully elucidated. Here, we demonstrate that HRK is silenced by hypermethylation of a major proximal CpG island in the HRK promoter. Furthermore, we show that HRK is a novel target gene regulated by the transcription factor AP-2α, which interacts with an AP-2α binding site in the HRK promoter. Hypermethylation of the major proximal CpG island (which contains the AP-2α binding site within the most densely methylated -218- to -194-bp region) inhibited AP-2α binding and transcriptional activity. Artificial overexpression of AP-2α in melanoma cells up-regulated HRK transcription, which was further restored by treatment with DNA methyltransferase inhibitor 5-azacytidine. Artificial overexpression of HRK by recombinant adenovirus induced caspase-dependent apoptosis, inhibited melanoma cell growth in vitro, and markedly reduced in vivo melanoma growth in a nude mouse xenograft model. RNA interference by siHRK or siAP-2α reversed the above effects. We conclude that the synergistic effects of HRK promoter hypermethylation and loss of AP-2α transactivation lead to HRK gene silencing and confer resistance to apoptosis and enhanced tumor growth. These novel molecular lesions may provide the basis for new therapeutic approaches to treating AP-2α- and HRK-deficient cancers.

Reversal of epigenetic silencing of AP-2alpha results in increased zinc uptake in DU-145 and LNCaP prostate cancer cells

Zinc accumulation is lost during prostate carcinogenesis. Recent studies reveal a strong association between prostate cancer progression and the downregulation of the zinc uptake transporters hZip1 and hZip3. The aim of this work was to assess the involvement of epigenetic processes in the disruption of zinc uptake homeostasis in prostate adenocarcinoma. In this report, we demonstrate an increase in hZip1 and hZip3 zinc transporters' expression and zinc uptake by the prostate cancer cells DU-145 and LNCaP in response to 5-aza-2'-deoxycytidine. This effect is due to demethylation of the promoter region of the activator protein (AP)-2alpha protein, which is crucial for hZip1 and hZip3 genes expression. Loss of AP-2alpha expression in DU-145 and LNCaP prostate cancer cells is due to hypermethylation of its promoter region. Similarly, we found higher AP-2alpha promoter methylation levels in clinical samples of early-stage prostate adenocarcinoma when compared with adjacent non-malignant prostate tissue. Taken together, our findings provide a better understanding of the epigenetic mechanisms that are involved in the loss of AP-2alpha protein in prostate cancer cells which lead to decreased cellular zinc uptake-a sine qua non of prostate cancer development.

Tumor suppressor HLJ1 binds and functionally alters nucleophosmin via activating enhancer binding protein 2alpha complex formation

HLJ1, a member of the heat shock protein 40 chaperone family, is a newly identified tumor suppressor that has been implicated in tumorigenesis and metastasis in non-small cell lung cancer. However, the mechanism of HLJ1 action is presently obscure. In this study, we report that HLJ1 specifically interacts with the nuclear protein nucleophosmin (NPM1), forming a multiprotein complex that alters the nucleolar distribution and oligomerization state of NPM1. Enforced accumulation of NPM1 oligomers by overexpression in weakly invasive but high HLJ1-expressing cells induced the activity of signal transducer and activator of transcription 3 (STAT3) and increased cellular migration, invasiveness, and colony formation. Furthermore, silencing HLJ1 accelerated NPM1 oligomerization, inhibited the activity of transcription corepressor activating enhancer binding protein 2alpha (AP-2alpha), and increased the activities of matrix metalloproteinase-2 (MMP-2) and STAT3. Our findings suggest that HLJ1 switches the role of NPM1, which can act as tumor suppressor or oncogene, by modulating the oligomerization of NPM1 via HLJ1-NPM1 heterodimer formation and recruiting AP-2alpha to the MMP-2 promoter.

Activator protein-2 impairs the invasion of a human extravillous trophoblast cell line

The reduced migration/invasion of extravillous trophoblasts (EVTs) is a key feature of the genesis of preeclampsia. We and others previously reported that transcriptional factors activator protein-2 (AP-2) alpha and AP-2gamma act as suppressors of tumor invasion. The present study examined the expressions of AP-2alpha and AP-2gamma in preeclamptic placenta vs. control placenta and investigated their effect on the function of EVTs. The expressions of AP-2alpha and AP-2gamma were elevated in the preeclamptic placentas in comparison with the gestational age-matched control placentas. Their expressions also increased in EVTs of the preeclamptic placentas. Thereafter, we transfected AP-2alpha or AP-2gamma into human EVT cell line, HTR-8/SVneo. The overexpression of AP-2alpha or AP-2gamma decreased the migratory and invasive abilities in HTR-8/SVneo cells. This was followed by the reduction of protease activated receptor-1 and matrix metalloproteinases and a significant induction of plasminogen activator inhibitor-1 and the tissue inhibitor of metalloproteinase-1. AP-2alpha and AP-2gamma were weakly expressed in the cultured EVTs and HTR-8/SVneo cells, whereas they were induced by TNF-alpha, which increases in preeclamptic placenta and impairs trophoblast invasion. In the presence of TNF-alpha, the invasion of the HTR-8/SVneo cells was partially restored by a blocking of AP-2 induction using small interfering RNA of AP-2. The present data suggest that AP-2 may suppress trophoblast migration and invasion, thus leading to a shallow placentation in preeclampsia.

H-cadherin expression reduces invasion of malignant melanoma

Melanocytic behavior, survival, and proliferation are regulated through a complex system of cell-cell adhesion molecules. Pathologic changes leading to development of malignant melanoma, upset the delicate homeostatic balance between melanocytes and keratinocytes and can lead to altered expression of cell-cell adhesion and cell-cell communication molecules. Malignant transformation of melanocytes frequently coincides with loss of E-cadherin expression. We now show loss of another member of the superfamily of classical cadherins, H-cadherin (CDH13), which may be involved in the development of malignant melanoma. The provided data show that H-cadherin expression is lost in nearly 80% of the analyzed melanoma cell lines. Knockdown of H-cadherin using siRNA increases invasive capacity in melanocytes. Functional assays show that the re-expression of H-cadherin decreases migration and invasion capacity, as well as anchorage-independent growth in comparison to control melanoma cells. Furthermore, melanoma cells, which re-express H-cadherin via stable transfection show a reduction in rate of tumor growth in a nu/nu mouse tumor model in comparison to the parental control transfected cell lines. Our study presents for the first time the down-regulation of H-cadherin in malignant melanomas and its possible functional relevance in maintenance healthy skin architecture.

New pathway links from cancer-progression determinants to gene expression of matrix metalloproteinases in breast cancer cells

AP-2alpha, interleukin-4 (IL-4), E-cadherin, fibulin 1D, p16(INK4alpha), PTEN, RKIP, and S100A4 are determinants (suppressors, except for S100A4) of cancer cell invasiveness and other traits of cancer progression, which are located upstream of matrix metalloproteinases (MMPs) in cell signaling pathways. We will refer to them as upstream cancer-progression determinants (UCPDs, for brevity). MMP-1, MMP-2, MMP-9, MMP-11, MMP-13, MMP-14, MMP-16, and MMP-19 are enhancers of cancer cell invasiveness and other traits of cancer progression, in MDA-MB-231 breast cancer cells. We are interested in pathway links from UCPDs to gene expression of cancer cell MMPs in MDA-MB-231 cells. To test models about these links, wild-type copies of UCPDs were transiently overexpressed and then MMP mRNAs were measured by reverse transcription real-time PCR. The present results show that each of eight UCPDs is linked to the gene expression of a unique set of MMPs. This indicates that the effects are sequence-specific and that each UCPD reaches these MMP expressions through different sets of signaling pathways. We have detected 20 new pathway links, 11 are downregulatory and nine are upregulatory; 15 are new links in any cell, and five are new links in breast cancer. In seven links, three cancer-progression suppressing UCPDs unexpectedly enhance the gene expression of five cancer-progression promoting MMPs.

Rb depletion results in deregulation of E-cadherin and induction of cellular phenotypic changes that are characteristic of the epithelial-to-mesenchymal transition

The retinoblastoma tumor suppressor protein (Rb) is mutated or expressed at very low levels in several tumor types, including retinoblastoma and osteosarcoma, as well as small cell lung, colon, prostate, bladder, and breast carcinomas. Loss or reduction of Rb expression is seen most commonly in high-grade breast adenocarcinomas, suggesting that a relationship may exist between loss of Rb function and a less-differentiated state, increased proliferation, and high metastatic potential. In this study, we found that knockdown of Rb by small interfering RNA in MCF7 breast cancer cells disrupts cell-cell adhesion and induces a mesenchymal-like phenotype. The epithelial-to-mesenchymal transition (EMT), a key event in embryonic morphogenesis, is implicated in the metastasis of primary tumors. Additionally, Rb is decreased during growth factor- and cytokine-induced EMT and overexpression of Rb inhibits the EMT in MCF10A human mammary epithelial cells. Ectopic expression and knockdown of Rb resulted in increased or reduced expression of E-cadherin, which is specifically involved in epithelial cell-cell adhesion. Other EMT-related transcriptional factors, including Slug and Zeb-1, are also induced by Rb depletion. Furthermore, we confirmed that Rb binds to an E-cadherin promoter sequence in association with the transcription factor activator protein-2alpha. Finally, in breast cancer specimens, we observed a concurrent down-regulation of Rb and E-cadherin expression in mesenchymal-like invasive cancers. These findings suggest that Rb inactivation contributes to tumor progression due to not only loss of cell proliferation control but also conversion to an invasive phenotype and that the inhibition of EMT is a novel tumor suppressor function of Rb.

Transcription factor AP-2alpha represses both the mucin MUC4 expression and pancreatic cancer cell proliferation

MUC4 is a transmembrane mucin expressed in pancreatic ductal adenocarcinoma (DAC) in contrast to normal pancreas, and is an independent predictor of poor prognosis in patients with invasive DAC. Our aim was therefore to investigate the mechanisms that control MUC4 expression in pancreatic cancer cells. We focused our study on activator protein (AP)-2alpha transcription factor that acts as a tumour suppressor gene in several cancers. In a series of 18 human DAC, using immunohistochemistry, we confirmed that MUC4 was exclusively expressed in cancerous or preneoplastic lesions in 83% of the samples. On the contrary, AP-2 was mainly expressed by non-tumoural ductal cells (61%) or endocrine cells (67%). Moreover, MUC4 and AP-2 were never found co-expressed suggesting an inhibitory role of AP-2alpha in normal ductal cells. In CAPAN-1 and CAPAN-2 cells, transient AP-2alpha over-expression decreased both MUC4 mRNA and apomucin levels by 20-40% by a mechanism involving inhibition of MUC4 promoter. By chromatin immunoprecipitation and gel-shift assays, we demonstrated that this inhibition involved two AP-2 cis-elements located in the -475/-238 region of the promoter. CAPAN-1 clones, which stably over-expressed AP-2alpha, displayed a strong MUC4 down-regulation (-38 to -100%), a significant decrease of both cell proliferation and invasion concomitant to the up-regulation of p27 cyclin-dependent kinase inhibitor. In conclusion, our data provide evidence that AP-2alpha is an important in vivo negative regulator of MUC4 expression in human pancreatic tissue and that AP-2alpha may play a tumour-suppressive role in pancreatic DAC.

Activator protein-2 in carcinogenesis with a special reference to breast cancer-A mini review

Activator protein-2 (AP-2) transcription factors are involved in the regulation of cell proliferation, differentiation, apoptosis and carcinogenesis. AP-2alpha has been suggested to function as a tumor suppressor in many cancers and AP-2gamma to be a marker of testicular and germ cell malignancies. At least 3 of the 5 AP-2 family members identified to date, AP-2alpha, AP-2beta and AP-2gamma, are known to be expressed in breast tissue and thought to coordinate the growth and development of the breast via regulation of several breast-related genes such as human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER). The function of AP-2alpha seems to be tumor suppressive in breast tissue, whereas the role of the other AP-2 family members is less well known. In this review, we summarize the current knowledge of AP-2 in carcinogenesis, especially in breast cancer.

Loss of AP-2alpha results in deregulation of E-cadherin and MMP-9 and an increase in tumorigenicity of colon cancer cells in vivo

Activator protein-2 (AP-2) is a transcription factor that regulates proliferation and differentiation in mammalian cells and has been implicated in the acquisition of the metastatic phenotype in several types of cancer. Herein, we examine the role of AP-2alpha in colon cancer progression. We provide evidence for the lack of AP-2alpha expression in the late stages of colon cancer cells. Re-expression of the AP-2alpha gene in the AP-2alpha-negative SW480 colon cancer cells suppressed their tumorigenicity following orthotopic injection into the cecal wall of nude mice. The inhibition of tumor growth could be attributed to the increased expression of E-cadherin and decreased expression and activity of matrix-metalloproteinase-9 (MMP-9) in the transfected cells, as well as a substantial loss of their in vitro invasive properties. Conversely, targeting constitutive expression of AP-2alpha in AP-2-positive KM12C colon cancer cells with small interfering RNA resulted in an increase in their invasive potential, downregulation of E-cadherin and increased expression of MMP-9. In SW480 cells, re-expression of AP-2alpha resulted in a fourfold increase in the activity of E-cadherin promoter, and a 5-14-fold decrease in the activity of MMP-9 promoter, indicating transcriptional regulation of these genes by AP-2alpha. Chromatin immunoprecipitation assay showed that re-expressed AP-2alpha directly binds to the promoter of E-cadherin, where it has been previously reported to act as a transcriptional activator. Furthermore, chromatin immunoprecipitation assay revealed AP-2alpha binding to the MMP-9 promoter, which ensued by decreased binding of transcription factor Sp-1 and changes in the recruitment of transcription factors to a distal AP-1 element, thus, contributing to the overall downregulation of MMP-9 promoter activity. Collectively, our data provide evidence that AP-2alpha acts as a tumor suppressor gene in colon cancer..

Phosphatidylinositol 3-kinase/Akt regulates the balance between plasminogen activator inhibitor-1 and urokinase to promote migration of SKOV-3 ovarian cancer cells

OBJECTIVES

Increased levels of urokinase-type plasminogen activator (uPA) are associated with shortened overall survival in ovarian cancer patients. Additionally, elevated levels of the serine protease inhibitor (serpin), plasminogen activator inhibitor-1 (PAI-1), a uPA inhibitor, have also been correlated with an unfavorable prognosis in ovarian cancer. Therefore, it is critical to understand the signaling pathways that regulate PAI-1 and uPA expression in cancer cell migration-invasion.

METHODS

We studied the PI3K/Akt, Rho kinase/ROCK, p38 MAPK and MEK pathways and their modulation of PAI-1 and uPA expression and wound-induced cell migration in SKOV-3 ovarian cancer cells. The PI3K/Akt pathway was further examined using pharmacological inhibitors (LY294002 and wortmannin), Akt siRNA, constitutively active Akt adenovirus and treatment with IGF-1/insulin in the SKOV-3 cells.

RESULTS

The PI3K/Akt pathway negatively regulates PAI-1 expression and positively correlates with migratory abilities and uPA expression in SKOV-3 cells. A reduction in active Akt results in an increase in PAI-1 expression coupled with a decrease in uPA expression to ultimately result in reduced cell migration and invasion. By contrast, an increase in Akt activity reduces PAI-1 expression and results in an increase in SKOV-3 wound-induced cell migration. Furthermore, IGF-1 and insulin stimulated SKOV-3 migration by altering the balance between uPA and PAI-1 to favor uPA, and the enhanced migration was attenuated by treatment with LY294002 indicating PI3K/Akt in this pathway.

CONCLUSIONS

These results suggest an overall ovarian tumor-protective role for PAI-1, and that the PI3K/Akt signaling pathway regulates the ratio of PAI-1:uPA to either increase or decrease cell migration.

Promoter hypermethylation profile of ovarian epithelial neoplasms

PURPOSE

Ovarian carcinomas are believed to arise de novo from surface epithelium, but the actual molecular pathogenesis is unknown. The aim of this study was to compare the promoter hypermethylation profiles of ovarian epithelial neoplasms to better understand the role of epigenetic silencing in carcinogenesis.

EXPERIMENTAL DESIGN

We analyzed the DNA promoter methylation status of eight tumor suppressor and cancer-related genes (p16, RARbeta, E-cadherin,H-cadherin, APC, GSTP1, MGMT, RASSF1A) in 23 benign cystadenomas, 23 low malignant potential (LMP) tumors, and 23 invasive carcinomas by methylation-specific PCR.

RESULTS

Benign cystadenomas exhibited promoter hypermethylation in only two genes, p16 (13%) and E-cadherin (13%). LMP tumors also showed p16 (22%) and E-cadherin (17%) methylation, in addition to RARbeta (9%) and H-cadherin (4%). All eight genes were hypermethylated in invasive cancers at a frequency of 9% to 30%. The mean methylation index was highest in invasive tumors [0.20 versus 0.065 (LMP) and 0.033 (cystadenomas); P = 0.001]. Promoter methylation of at least one gene was most commonly observed among invasive cancers [78% versus 44% (LMP; P = 0.03) and 26% (cystadenomas; P = 0.0009)]. Three genes exhibited higher methylation frequencies in invasive tumors: RASSF1A (30% versus 0%; P = 0.0002), H-cadherin (22% versus 2%; P = 0.013), and APC (22% versus 0%; P = 0.003).

CONCLUSIONS

Promoter hypermethylation is a frequent epigenetic event that occurs most commonly in invasive epithelial ovarian carcinomas. The profile of aberrant methylation suggests that an accumulation of events at specific genes may trigger malignant transformation of some benign cystadenomas and LMP tumors.