TGF beta-induced Smad signaling remains intact in primary human ovarian cancer cells

Glycosphingolipids are mediators of cancer plasticity through independent signaling pathways

The molecular repertoire promoting cancer cell plasticity is not fully elucidated. Here, we propose that glycosphingolipids (GSLs), specifically the globo and ganglio series, correlate and promote the transition between epithelial and mesenchymal cells. The epithelial character of ovarian cancer remains stable throughout disease progression, and spatial glycosphingolipidomics reveals elevated globosides in the tumor compartment compared with the ganglioside-rich stroma. CRISPR-Cas9 knockin mediated truncation of endogenous E-cadherin induces epithelial-to-mesenchymal transition (EMT) and decreases globosides. The transcriptomics analysis identifies the ganglioside-synthesizing enzyme ST8SIA1 to be consistently elevated in mesenchymal-like samples, predicting poor outcome. Subsequent deletion of ST8SIA1 induces epithelial cell features through mTOR^S2448 phosphorylation, whereas loss of globosides in ΔA4GALT cells, resulting in EMT, is accompanied by increased ERK^Y202/T204 and AKT^S124. The GSL composition dynamics corroborate cancer cell plasticity, and further evidence suggests that mesenchymal cells are maintained through ganglioside-dependent, calcium-mediated mechanisms.

Review: Targeting the Transforming Growth Factor-Beta Pathway in Ovarian Cancer

Despite extensive efforts, there has been limited progress in optimizing treatment of ovarian cancer patients. The vast majority of patients experience recurrence within a few years despite a high response rate to upfront therapy. The minimal improvement in overall survival of ovarian cancer patients in recent decades has directed research towards identifying specific biomarkers that serve both as prognostic factors and targets for therapy. Transforming Growth Factor-β (TGF-β) is a superfamily of proteins that have been well studied and implicated in a wide variety of cellular processes, both in normal physiologic development and malignant cellular growth. Hypersignaling via the TGF-β pathway is associated with increased tumor dissemination through various processes including immune evasion, promotion of angiogenesis, and increased epithelial to mesenchymal transformation. This pathway has been studied in various malignancies, including ovarian cancer. As targeted therapy has become increasingly prominent in drug development and clinical research, biomarkers such as TGF-β are being studied to improve outcomes in the ovarian cancer patient population. This review article discusses the role of TGF-β in ovarian cancer progression, the mechanisms of TGF-β signaling, and the targeted therapies aimed at the TGF-β pathway that are currently being studied.

TGFβ splicing and canonical pathway activation in high-grade serous carcinoma

The present study analyzed the expression and clinical role of the transforming growth factor-β (TGFβ) pathway in high-grade serous carcinoma (HGSC), with focus on malignant effusions. TGFβ1-3 and TGFβRI-III mRNA expression by qRT-PCR was analyzed in 70 HGSC effusions and 55 solid specimens (28 ovarian, 27 abdominal metastases). Protein expression of Smad2 and Smad3 and their phosphorylated forms by Western blotting was analyzed in 73 specimens (42 effusions, 13 ovarian carcinomas, 18 solid metastases). Expression was analyzed for association with anatomic site and clinical parameters, including survival. TGFβRI and TGFβRII mRNA was overexpressed in effusions and solid metastases, particularly the former, compared to that in the ovarian tumors (p < 0.001 to p = 0.05), with anatomic site-dependent expression of splice variants. Conversely, Smad2, p-Smad2, and p-Smad3 were overexpressed in solid specimens (ovarian and peritoneal) compared to those in effusions (p < 0.001 for all). In univariate survival analysis, higher TGFβRI variant 1 and TGFβRIII mRNA levels were associated with a trend for shorter overall survival in patients with post-chemotherapy effusions (p = 0.066 and p = 0.087, respectively), and the latter was an independent prognostic marker in Cox multivariate analysis (p = 0.041). Smad3 protein expression was associated with a trend for shorter overall survival in univariate survival analysis (p = 0.052). TGFβ receptor splice variant expression is anatomic site-dependent in HGSC. Elevated levels of TGFβ signaling pathway mRNAs are seen in metastatic HGSC, but are not accompanied by increased Smad expression and activation in HGSC effusions, evidence of failure to activate canonical TGFβ signaling. Assessment of the prognostic role of this pathway in HGSC effusions merits further research.

Mesothelial-to-mesenchymal transition as a possible therapeutic target in peritoneal metastasis of ovarian cancer

Peritoneal dissemination is the primary metastatic route of ovarian cancer (OvCa), and is often accompanied by the accumulation of ascitic fluid. The peritoneal cavity is lined by mesothelial cells (MCs), which can be converted into carcinoma‐associated fibroblasts (CAFs) through mesothelial‐to‐mesenchymal transition (MMT). Here, we demonstrate that MCs isolated from ascitic fluid (AFMCs) of OvCa patients with peritoneal implants also undergo MMT and promote subcutaneous tumour growth in mice. RNA sequencing of AFMCs revealed that MMT‐related pathways – including transforming growth factor (TGF)‐β signalling – are differentially regulated, and a gene signature was verified in peritoneal implants from OvCa patients. In a mouse model, pre‐induction of MMT resulted in increased peritoneal tumour growth, whereas interfering with the TGF‐β receptor reduced metastasis. MC‐derived CAFs showed activation of Smad‐dependent TGF‐β signalling, which was disrupted in OvCa cells, despite their elevated TGF‐β production. Accordingly, targeting Smad‐dependent signalling in the peritoneal pre‐metastatic niche in mice reduced tumour colonization, suggesting that Smad‐dependent MMT could be crucial in peritoneal carcinomatosis. Together, these results indicate that bidirectional communication between OvCa cells and MC‐derived CAFs, via TGF‐β‐mediated MMT, seems to be crucial to form a suitable metastatic niche. We suggest MMT as a possible target for therapeutic intervention and a potential source of biomarkers for improving OvCa diagnosis and/or prognosis. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Prioritizing cancer-related microRNAs by integrating microRNA and mRNA datasets

MicroRNAs (miRNAs) are small non-coding RNAs regulating the expression of target genes, and they are involved in cancer initiation and progression. Even though many cancer-related miRNAs were identified, their functional impact may vary, depending on their effects on the regulation of other miRNAs and genes. In this study, we propose a novel method for the prioritization of candidate cancer-related miRNAs that may affect the expression of other miRNAs and genes across the entire biological network. For this, we propose three important features: the average expression of a miRNA in multiple cancer samples, the average of the absolute correlation values between the expression of a miRNA and expression of all genes, and the number of predicted miRNA target genes. These three features were integrated using order statistics. By applying the proposed approach to four cancer types, glioblastoma, ovarian cancer, prostate cancer, and breast cancer, we prioritized candidate cancer-related miRNAs and determined their functional roles in cancer-related pathways. The proposed approach can be used to identify miRNAs that play crucial roles in driving cancer development, and the elucidation of novel potential therapeutic targets for cancer treatment.

Aberrant over-expression of COX-1 intersects multiple pro-tumorigenic pathways in high-grade serous ovarian cancer

Cyclooxygenase-1 (COX-1) is implicated in ovarian cancer. However, patterns of COX expression and function have been unclear and controversial. In this report, patterns of COX-1 and COX-2 gene expression were obtained from RNA-seq data through The Cancer Genome Atlas. Our analysis revealed markedly higher COX-1 mRNA expression than COX-2 in high-grade serous ovarian cancers (HGSOC) and higher COX-1 expression in HGSOC tumors than 10 other tumor types. High expression of COX-1 in HGSOC tumors was confirmed in an independent tissue microarray. In contrast, lower or similar expression of COX-1 compared to COX-2 was observed in endometrioid, mucinous and clear cell tumors. Stable COX-1 knockdown in HGSOC-representative OVCAR-3 ovarian cancer cells reduced gene expression in multiple pro-tumorigenic pathways. Functional cell viability, clonogenicity, and migration/invasion assays were consistent with transcriptomic changes. These effects were reversed by stable over-expression of COX-1 in SKOV-3 cells. Our results demonstrate a distinct pattern of COX-1 over-expression in HGSOC tumors and strong association of COX-1 with multiple pro-tumorigenic pathways in ovarian cancer cells. These findings provide additional insight into the role of COX-1 in human ovarian cancer and support further development of methods to selectively target COX-1 in the management of HGSOC tumors.

Invasion of ovarian cancer cells is induced byPITX2-mediated activation of TGF-β and Activin-A

BACKGROUND

Most ovarian cancers are highly invasive in nature and the high burden of metastatic disease make them a leading cause of mortality among all gynaecological malignancies. The homeodomain transcription factor, PITX2 is associated with cancer in different tissues. Our previous studies demonstrated increased PITX2 expression in human ovarian tumours. Growing evidence linking activation of TGF-β pathway by homeodomain proteins prompted us to look for the possible involvement of this signalling pathway in PITX2-mediated progression of ovarian cancer.

METHODS

The status of TGF-β signalling in human ovarian tissues was assessed by immunohistochemistry. The expression level of TGFB/INHBA and other invasion-associated genes was measured by quantitative-PCR (Q-PCR) and Western Blot after transfection/treatments with clones/reagents in normal/cancer cells. The physiological effect of PITX2 on invasion/motility was checked by matrigel invasion and wound healing assay. The PITX2- and activin-induced epithelial-mesenchymal transition (EMT) was evaluated by Q-PCR of respective markers and confocal/phase-contrast imaging of cells.

RESULTS

Human ovarian tumours showed enhanced TGF-β signalling. Our study uncovers the PITX2-induced expression of TGFB1/2/3 as well as INHBA genes (p < 0.01) followed by SMAD2/3-dependent TGF-β signalling pathway. PITX2-induced TGF-β pathway regulated the expression of invasion-associated genes, SNAI1, CDH1 and MMP9 (p < 0.01) that accounted for enhanced motility/invasion of ovarian cancers. Snail and MMP9 acted as important mediators of PITX2-induced invasiveness of ovarian cancer cells. PITX2 over-expression resulted in loss of epithelial markers (p < 0.01) and gain of mesenchymal markers (p < 0.01) that contributed significantly to ovarian oncogenesis. PITX2-induced INHBA expression (p < 0.01) contributed to EMT in both normal and ovarian cancer cells.

CONCLUSIONS

Overall, our findings suggest a significant contributory role of PITX2 in promoting invasive behaviour of ovarian cancer cells through up-regulation of TGFB/INHBA. We have also identified the previously unknown involvement of activin-A in promoting EMT. Our work provides novel mechanistic insights into the invasive behavior of ovarian cancer cells. The extension of this study have the potential for therapeutic applications in future.

Oncolytic virotherapy for ovarian cancer

In the past two decades, more than 20 viruses with selective tropism for tumor cells have been developed as oncolytic viruses (OVs) for treatments of a variety of malignancies. Of these viruses, eleven have been tested in human ovarian cancer models in preclinical studies. So far, nine phase I or II clinical trials have been conducted or initiated using four different types of OVs in patients with recurrent ovarian cancers. In this article, we summarize the different OVs that are being assessed as therapeutics for ovarian cancer. We also present an overview of recent advances in identification of key genetic or immune-response pathways involved in tumorigenesis of ovarian cancer, which provides a better understanding of the tumor specificities and oncolytic properties of OVs. In addition, we discuss how next-generation OVs could be genetically modified or integrated into multimodality regimens to improve clinical outcomes based on recent advances in ovarian cancer biology.

BMP signalling controls the malignant potential of ascites-derived human epithelial ovarian cancer spheroids via AKT kinase activation

Epithelial ovarian cancer (EOC) cells have the ability to form multi-cellular aggregates in malignant ascites which dramatically alters cell signalling, survival, and metastatic potential. Herein, we demonstrate that patient ascites-derived EOC cells down-regulate endogenous bone morphogenetic protein (BMP) signalling by decreasing BMP ligand expression when grown in suspension culture to form spheroids. Enforced BMP signalling in these cells via constitutively-active BMP type I ALK3(QD) receptor expression causes the formation of smaller, more loosely-aggregated spheroids. Additionally, ALK3(QD)-expressing spheroids have an increased rate of adhesion and dispersion upon reattachment to substratum. Inhibition of endogenous BMP signalling using recombinant Noggin or small molecule inhibitor LDN-193189, on the other hand, opposed these phenotypic changes. To identify potential targets that impact the phenotype of EOC spheroids due to activated BMP signalling, we performed genome-wide expression analyses using Affymetrix arrays. Using the online Connectivity Map resource, the BMP signalling gene expression signature revealed that the AKT pathway is induced by activated BMP signalling in EOC cells; this finding was further validated by phospho-AKT immuno-blotting. In fact, treatment of EOC spheroids with an AKT inhibitor, Akti-1/2, reduced BMP-stimulated cell dispersion during reattachment as compared to controls. Thus, we have identified AKT as being one important downstream component of activated BMP signalling on EOC spheroid pathobiology, which may have important implications on the metastatic potential of this malignancy.

TGF-β: friend or foe? The role of TGF-β/SMAD signaling in epigenetic silencing of ovarian cancer and its implication in epigenetic therapy

IMPORTANCE OF THE FIELD

The TGF-β signaling pathway plays an important role in regulating numerous cellular processes including growth inhibition of ovarian surface epithelial (OSE) cells. However, epithelial ovarian cancer is refractory to the inhibitory functions of TGF-β, and yet TGF-β induces metastasis or epithelial-mesenchymal transition (EMT) in advanced ovarian cancer. How TGF-β plays a certain role in one cell but a different role in its malignant counterpart is not fully understood.

AREAS COVERED IN THIS REVIEW

The role of TGF-β/SMAD signaling both in normal OSE cells and ovarian cancer as well as how dysregulation of this signaling pathway leads to epigenetic silencing of its downstream targets in ovarian neoplasias are reviewed. The therapeutic implication of this signaling pathway in epigenetic therapy of ovarian cancer are also discussed.

WHAT THE READER WILL GAIN

The reader will gain insight on how dysregulation of TGF-β signaling alters promoter methylation and histone modifications of TGF-β downstream targets in ovarian cancer.

TAKE HOME MESSAGE

Disruption of TGF-β/SMAD signaling leads to epigenetic silencing of its target genes transiently through histone modifications but permanently by promoter hypermethylation. Targeting the TGF-β signaling pathway may be a novel therapeutic strategy in ovarian cancer.

Epigenetic suppression of the TGF-beta pathway revealed by transcriptome profiling in ovarian cancer

Epithelial ovarian cancer is the leading cause of death among gynecologic malignancies. Diagnosis usually occurs after metastatic spread, largely reflecting vague symptoms of early disease combined with lack of an effective screening strategy. Epigenetic mechanisms of gene regulation, including DNA methylation, are fundamental to normal cellular function and also play a major role in carcinogenesis. To elucidate the biological and clinical relevance of DNA methylation in ovarian cancer, we conducted expression microarray analysis of 39 cell lines and 17 primary culture specimens grown in the presence or absence of DNA methyltransferase (DNMT) inhibitors. Two parameters, induction of expression and standard deviation among untreated samples, identified 378 candidate methylated genes, many relevant to TGF-beta signaling. We analyzed 43 of these genes and they all exhibited methylation. Treatment with DNMT inhibitors increased TGF-beta pathway activity. Hierarchical clustering of ovarian cancers using the 378 genes reproducibly generated a distinct gene cluster strongly correlated with TGF-beta pathway activity that discriminates patients based on age. These data suggest that accumulation of age-related epigenetic modifications leads to suppression of TGF-beta signaling and contributes to ovarian carcinogenesis.

Effects of omega-3 fatty acids on components of the transforming growth factor beta-1 pathway: implication for dietary modification and prevention in ovarian cancer

OBJECTIVE

We previously demonstrated that omega-3 fatty acids (OM-3FAs) have definitive inhibitory effects on ovarian cancer cell lines. We sought to determine whether the inhibitory effects of OM-3FAs were mediated by the transforming growth factor (TGF)-beta1 signaling pathway.

STUDY DESIGN

Ovarian cancer cell lines were grown at 37 degrees C in 5% CO(2) and treated with OM-3FAs, omega-6 fatty acids, and control at different concentrations for 24-72 hours. Enzyme-linked immunosorbent assay (ELISA) assay and Western blot analysis were used to measure TGF-beta1, phosphorylated mothers against decapentaplegic (Smad)-3 and p21 protein levels.

RESULTS

An ELISA assay demonstrated that OM-3FA treatment increased TGF-beta1 in all 3 Hey cell lines (P < .05). In both SKOV-3 and OVCAR-3 cells, TGF-beta1 levels were not significantly increased. Western blots confirmed increases in TGF-beta1, Smad-3 and p21 protein levels in Hey and HeyC2 but not SKOV-3 and OVCAR-3 cells.

CONCLUSION

OM-3FAs increased the level of TGF-beta1, Smad-3, and p21 protein in ovarian cancer cells known to be more sensitive to their inhibitory effect.

Differential regulation of human thymosin beta 15 isoforms by transforming growth factor beta 1

We recently identified an additional isoform of human thymosin beta 15 (also known as NB-thymosin beta, gene name TMSB15A) transcribed from an independent gene, and designated TMSB15B. The purpose of this study was to investigate whether these isoforms were differentially expressed and functional. Our data show that the TMSB15A and TMSB15B isoforms have distinct expression patterns in different tumor cell lines and tissues. TMSB15A was expressed at higher levels in HCT116, DU145, LNCaP, and LNCaP-LN3 cancer cells. In MCF-7, SKOV-3, HT1080, and PC-3MLN4 cells, TMSB15A and TMSB15B showed approximately equivalent levels of expression, while TMSB15B was the predominant isoform expressed in PC-3, MDA-MB-231, NCI-H322, and Caco-2 cancer cells. In normal human prostate and prostate cancer tissues, TMSB15A was the predominant isoform expressed. In contrast, normal colon and colon cancer tissue expressed predominantly TMSB15B. The two gene isoforms are also subject to different transcriptional regulation. Treatment of MCF-7 breast cancer cells with transforming growth factor beta 1 repressed TMSB15A expression but had no effect on TMSB15B. siRNA specific to the TMSB15B isoform suppressed cell migration of prostate cancer cells to epidermal growth factor, suggesting a functional role for this second isoform. In summary, our data reveal different expression patterns and regulation of a new thymosin beta 15 gene paralog. This may have important consequences in both tumor and neuronal cell motility.

Aberrant transforming growth factor beta1 signaling and SMAD4 nuclear translocation confer epigenetic repression of ADAM19 in ovarian cancer

Transforming growth factor-beta (TGF-beta)/SMAD signaling is a key growth regulatory pathway often dysregulated in ovarian cancer and other malignancies. Although loss of TGF-beta-mediated growth inhibition has been shown to contribute to aberrant cell behavior, the epigenetic consequence(s) of impaired TGF-beta/SMAD signaling on target genes is not well established. In this study, we show that TGF-beta1 causes growth inhibition of normal ovarian surface epithelial cells, induction of nuclear translocation SMAD4, and up-regulation of ADAM19 (a disintegrin and metalloprotease domain 19), a newly identified TGF-beta1 target gene. Conversely, induction and nuclear translocation of SMAD4 were negligible in ovarian cancer cells refractory to TGF-beta1 stimulation, and ADAM19 expression was greatly reduced. Furthermore, in the TGF-beta1 refractory cells, an inactive chromatin environment, marked by repressive histone modifications (trimethyl-H3K27 and dimethyl-H3K9) and histone deacetylase, was associated with the ADAM19 promoter region. However, the CpG island found within the promoter and first exon of ADAM19 remained generally unmethylated. Although disrupted growth factor signaling has been linked to epigenetic gene silencing in cancer, this is the first evidence demonstrating that impaired TGF-beta1 signaling can result in the formation of a repressive chromatin state and epigenetic suppression of ADAM19. Given the emerging role of ADAMs family proteins in growth factor regulation in normal cells, we suggest that epigenetic dysregulation of ADAM19 may contribute to the neoplastic process in ovarian cancer.

Expression profiling identifies altered expression of genes that contribute to the inhibition of transforming growth factor-beta signaling in ovarian cancer

Ovarian cancer is resistant to the antiproliferative effects of transforming growth factor-beta (TGF-beta); however, the mechanism of this resistance remains unclear. We used oligonucleotide arrays to profile 37 undissected, 68 microdissected advanced-stage, and 14 microdissected early-stage papillary serous cancers to identify signaling pathways involved in ovarian cancer. A total of seven genes involved in TGF-beta signaling were identified that had altered expression >1.5-fold (P < 0.001) in the ovarian cancer specimens compared with normal ovarian surface epithelium. The expression of these genes was coordinately altered: genes that inhibit TGF-beta signaling (DACH1, BMP7, and EVI1) were up-regulated in advanced-stage ovarian cancers and, conversely, genes that enhance TGF-beta signaling (PCAF, TFE3, TGFBRII, and SMAD4) were down-regulated compared with the normal samples. The microarray data for DACH1 and EVI1 were validated using quantitative real-time PCR on 22 microdissected ovarian cancer specimens. The EVI1 gene locus was amplified in 43% of the tumors, and there was a significant correlation (P = 0.029) between gene copy number and EVI1 gene expression. No amplification at the DACH1 locus was found in any of the samples. DACH1 and EVI1 inhibited TGF-beta signaling in immortalized normal ovarian epithelial cells, and a dominant-negative DACH1, DACH1-Delta DS, partially restored signaling in an ovarian cancer cell line resistant to TGF-beta. These results suggest that altered expression of these genes is responsible for disrupted TGF-beta signaling in ovarian cancer and they may be useful as new and novel therapeutic targets for ovarian cancer.

Tissue fibrosis and carcinogenesis: divergent or successive pathways dictate multiple molecular therapeutic targets for oligo decoy therapies

The extracellular matrix (ECM) is composed of several families of macromolecular components: fibrous proteins such as collagens, type I collagen (COL1), type III collagen (COL3), fibronectin, elastin, and glycoconjugates such as proteoglycans and matrix glycoproteins. Their receptors on the cell membrane, most of which in the case of the ECM belong to the integrins, which are heterodimeric proteins composed of alpha and beta chains. COL1 is the major fibrous collagen of bone, tendon, and skin; while COL3 is the more pliable collagen of organs like liver. Focus will not only be given to the regulation of synthesis of several fibrogenic parameters but also modulation of their degradation during growth factor-induced tissue fibrosis and cancer development. Evidence will be provided that certain tissues, which undergo fibrosis, also become cancerous. Why does there exist a divergency between tissues, which undergo frank fibrosis as an endpoint, and those tissues that undergo fibrosis and subsequently are susceptible to carcinogenicity; resulting from the etiological factor(s) causing the initial injury? For example, why does a polyvinyl alcohol (PVA) sponge implant become encapsulated and filled with fibrous tissue then fibrosis tissue growth stops? Why does the subcutaneous injection of a fibrogenic growth factor cause a benign growth and incisional wounding results in fibrosis and ultimately scarring? There are many examples of tissues, which undergo fibrosis as a prerequisite to carcinogenesis. Is there a cause-effect relationship? If you block tissue fibrosis in these precancerous tissues, would you block cancer formation? What are the molecular targets for blocking fibrosis and ultimately carcinogenesis? How can oligo decoys may be used to attenuate carcinogenesis and which oligo decoys specifically attenuate fibrogenesis as a prelude to carcinogenesis? What are other molecular targets for oligo decoy therapy in carcinogenesis?

Activin receptor-like kinase 7 induces apoptosis through up-regulation of Bax and down-regulation of Xiap in normal and malignant ovarian epithelial cell lines

Transforming growth factor-beta superfamily has been implicated in tumorigenesis. We have recently shown that Nodal, a member of transforming growth factor-beta superfamily, and its receptor, activin receptor-like kinase 7 (ALK7), inhibit proliferation and induce apoptosis in human epithelial ovarian cancer cell lines. In this study, we further investigated the cellular mechanisms underlying the apoptotic action of ALK7 using an immortalized ovarian surface epithelial cell line, IOSE397, and an epithelial ovarian cancer cell line, OV2008. Infection of these cells with an adenoviral construct carrying constitutively active ALK7 (Ad-ALK7-ca) potently induced cell death; all cells died after 3 and 5 days of Ad-ALK7-ca infection in IOSE397 and OV2008 cells, respectively. ALK7-ca induced the expression of proapoptotic factor Bax but suppressed the expression of antiapoptotic factors Bcl-2, Bcl-XL, and Xiap. Silencing of Bax by small interfering RNA in IOSE397 cells significantly reduced ALK7-ca-induced apoptosis as measured by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay but partially blocked ALK7-ca-induced caspase-3 activation and did not affect the down-regulation of Xiap by ALK7-ca. Dominant-negative Smad2, Smad3, and Smad4 blocked ALK7-ca-regulated Xiap and Bax expression and caspase-3 activation. Thus, ALK7-induced apoptosis is at least in part through two Smad-dependent pathways, Bax/Bcl-2 and Xiap.

Cell cycle genes in ovarian cancer: steps toward earlier diagnosis and novel therapies

Human malignant tumors are characterized by abnormal proliferation resulting from alterations in cell cycle-regulatory mechanisms. The regulatory pathways controlling cell cycle phases include several oncogenes and tumor suppressor genes that display a range of abnormalities with potential usefulness as markers of evolution or treatment response in ovarian cancer. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary. We sought to divide cell cycle-regulatory genes into four subgroups on the basis of their predominant role in a specific phase or during the transition between two phases of the cell cycle.

The conventional nonsteroidal anti-inflammatory drug sulindac sulfide arrests ovarian cancer cell growth via the expression of NAG-1/MIC-1/GDF-15

Although the chemopreventive and antitumorigenic activities of nonsteroidal anti-inflammatory drug (NSAID) against colorectal cancer are well established, the molecular mechanisms responsible for these properties in ovarian cancer have not been elucidated. Therefore, there is an urgent need to develop mechanism-based approaches for the management of ovarian cancer. To this end, the effect of several NSAIDs on ovarian cancer cells was investigated as assessed by the induction of NAG-1/MIC-1/GDF-15, a proapoptotic gene belonging to the transforming growth factor-beta superfamily. Sulindac sulfide was the most significant NSAID activated gene 1 (NAG-1) inducer and its expression was inversely associated with cell viability as determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. This growth suppression by sulindac sulfide was recovered by transfection of NAG-1 small interfering RNA. These results indicate that NAG-1 is one of the genes responsible for growth suppression by sulindac sulfide. Furthermore, we observed down-regulation of p21 WAF1/CIP1 by introduction of NAG-1 small interfering RNA into sulindac sulfide-treated cells. In addition, to elucidate other potential molecular mechanisms involved in sulindac sulfide treatment of ovarian cancer cells, we did a membrane-based microarray experiment. We found that cyclin D1, MMP-1, PI3KR1, and uPA were down-regulated by sulindac sulfide. In conclusion, a novel molecular mechanism is proposed to explain the experimental results and provide a rationale for the chemopreventive activity of NSAIDs in ovarian cancer.

Up-regulation of vascular endothelial growth factor-C by nicotine in cervical cancer cell lines

PROBLEM

Smoking and infection with human papilloma virus (HPV) are major risk factors for cervical cancer. Our earlier work shows that nicotine enhances cellular proliferation of cervical cancer cell lines by up-regulating epidermal growth factor (EGF) and its receptor EGF-R, which leads to increased insulin-like growth factor II in vitro. We found that the vascular endothelial growth factor (VEGF)-C, one of the five isoforms of VEGF, may be specifically involved in lymphogenic metastasis of cervical cancer. This has prompted us to study if in vitro nicotine treatment will up-regulate VEGF-C alongside EGF-R levels, while down regulating the anti-proliferative transforming growth factor (TGF)-beta levels in HPV positive cervical cancer cell lines.

METHOD OF STUDY

Cervical cancer cell lines CaSki, HeLa and ME-180, were cultured in serum free DMEM medium for 24-hr, and treated with 10 ng/mL nicotine in the medium supplemented with 10% fetal bovine serum. A group of untreated cells served as controls. The cells were cultured in chamber slides (for immunofluorescent antibody assay) as well as microtiter plate wells (for BrdU cell proliferation assay). The cellular levels of VEGF-C, TGF-beta, EGF-R and HPV-E6 (early protein 6) were measured by a semi-quantitative immunofluorescent antibody assay. The cell proliferation and immunofluorescent assay data were analyzed by a Student's t-test.

RESULTS

Cell proliferation was significantly increased after nicotine treatment in all the cell lines. The VEGF-C levels were significantly increased, while TGF-beta levels were decreased by nicotine in all the cell lines (P < 0.00001). EGF-R levels were also significantly increased after nicotine treatment in HeLa and ME-180, while HPV-E6 levels remained unchanged in all three.

CONCLUSIONS

Nicotine up regulates expression of cell proliferative VEGF-C and EGF-R, while down-regulating anti-proliferative TGF-beta. Our data suggest that nicotine in circulation and in cervical squamous epithelial cells may promote not only rapid tumor growth but its lympho-angiogenic spread (VEGF-C) as well. It appears that nicotine does not promote HPV spread in the cervical cancer cells.

Substantial changes in gene expression of Wnt, MAPK and TNFalpha pathways induced by TGF-beta1 in cervical cancer cell lines

Transforming growth factor-beta 1 (TGF-beta1) is a potent inhibitor of epithelial cell proliferation. During the development of cervical carcinoma however, an increase in production of TGF-beta1 is accompanied by decreased sensitivity for the growth-limiting effect of TGF-beta1. TGF-beta1 has an anti-proliferative effect on cells of the immune system and thus can be advantageous for tumor progression. The aim of the present study was to determine the effect of TGF-beta1 on mRNA expression profile of genes in pathways involved in cell growth and cell death, in cervical carcinoma cell lines with different sensitivity to TGF-beta1. For this purpose, we have investigated changes in gene expression in TGF-beta1 stimulated cervical cancer cell lines with high (CC10B), intermediate (SiHa) and low (HeLa) sensitivity to the anti-proliferative effect of TGF-beta1, at timepoints 0, 6, 12 and 24 h. Microarray analysis, using Affymetrics focus arrays, representing 8973 genes, was used to measure gene expression. In our study novel target genes involved in tumor necrosis factor alpha (TNFalpha), mitogen-activated protein kinase (MAPK) and wingless type (Wnt) pathways in response to TGF-beta1 were found. Substantial differences in gene expression between TGF-beta1 sensitive and insensitive cell lines were observed involving genes in TNFalpha, MAPK, Wnt and Smad pathways. Since these pathways are implicated in cell proliferation and cell death, these pathways may play a role in determining the overall sensitivity of a cell to TGF-beta1 induced cell growth inhibition. The results were subsequently validated by quantitative real-time PCR. Increased resistance to TGF-beta1 induced cell growth inhibition was correlated with an elevated production of TGF-beta1 by the cell lines, as measured by enzyme linked immunosorbent assay. TGF-beta1 production did not inhibit cell growth, since blocking TGF-beta1 protein by anti-TGF-beta had no effect on cell proliferation. TGF-beta1 excretion by tumor cells more likely contributes to paracrine stimulation of tumor development.

Association between endogenous gene expression and growth regulation induced by TGF-β1 in human gastric cancer cells

AIM: To investigate the association between endogenous gene expression and growth regulation including proliferation and apoptosis induced by transforming growth factor-β1 (TGF-β1) in human gastric cancer (GC) cells.

METHODS: Reverse transcription polymerase chain reaction (RT-PCR) was performed to detect the main components of the TGF-β1/Smads signal pathway in human poorly differentiated GC cell line BGC-823. Localization of Smad proteins was also determined using immunofluorescence. Then, the BGC-823 cells were cultured in the presence or absence of TGF-β1 (10 ng/mL) for 24 and 48 h, and the effects of TGF-β1 on proliferation and apoptosis were measured by cell growth curve and flow cytometry (FCM) analysis. The ultrastructural features of BGC-823 cells with or without TGF-β1 treatment were observed under transmission electron microscope. The apoptotic cells were visualized by means of the terminal deoxynucleotidyl transferase (TdT)-mediated dTUP in situ nick end-labeling (TUNEL) method. Meanwhile, the expression levels of endogenous p15,p21 and Smad7 mRNA and the corresponding proteins in the cells were detected at 1, 2 and 3 h after culture in the presence or absence of TGF-β1 (10 ng/mL) by semi-quantitative RT-PCR and Western blot, respectively.

RESULTS: The TGF-β1/Smad signaling was found to be intact and functional in BGC-823 cells. The growth curve revealed the most evident inhibition of cell proliferation by TGF-β1 at 48 h, and FCM assay showed G1 arrest accompanied with apoptosis induced by TGF-β1. The typical morphological changes of apoptosis were observed in cells exposed to TGF-β1. The apoptosis index (AI) in TGF-β1-treated cells was significantly higher than that in the untreated controls (10.7±1.3% vs 0.32±0.06%, P<0.01). The levels of p15,p21 and Smad7 mRNA and corresponding proteins in cells were significantly up-regulated at 1 h, but gradually returned to basal levels at 3 h following TGF-β1 (10 ng/mL) treatment.

CONCLUSION: TGF-β1 affects both proliferation and apoptosis of GC cells through the regulation of p15 and p21, and induces transient expression of Smad 7 as a negative feedback modulation of TGF-β1 signal. Our results suggest a novel functional role of p21 as an accelerant of TGF-β1-mediated apoptosis in GC cells.

The TGF-beta superfamily and its roles in the human ovary and placenta

The transforming growth factor-beta (TGF-beta) superfamily consists of a large group of growth and differentiation factors, such as TGF-betas, activins, inhibins, growth and differentiation factors (GDFs), and bone morphogenetic proteins (BMPs). These molecules act through specific receptor complexes that are composed of type I and type II serine/threonine receptor kinases. The receptor kinases subsequently activate Smad proteins, which then propagate the signals into the nucleus to regulate target gene expression. Several ligands in this family, such as TGF-betas, activins, inhibins, BMP-15, and GDF-9, play important roles in regulating human ovarian functions, including follicle development and maturation. Activin and TGF-beta are also involved in regulating placental development and functions. Abnormal expression or function of these ligands has been found in several pathological conditions. This review summarizes the role of the TGF-beta superfamily in human ovarian and placental regulation and function, and the potential clinical implications.

The p38 MAPK inhibitor, PD169316, inhibits transforming growth factor β-induced Smad signaling in human ovarian cancer cells

Transforming growth factor beta (TGFbeta) can signal through a variety of Smad-independent pathways, including the p38 MAPK pathway. Recent work has shown that inhibitors of p38 MAPK, such as SB203580 and SB202190, can inhibit signaling induced by TGFbeta. Here we show that another p38 MAPK inhibitor, PD169316, abrogates signaling initiated by both TGFbeta and Activin A, but not bone morphogenetic protein (BMP) 4. Inhibition of TGFbeta signaling is dose dependent and results in reduced Smad2 and Smad3 phosphorylation, nuclear translocation, and up-regulation of the TGFbeta target gene Smad7. Reduced TGFbeta signaling is not due to abrogation of p38 MAPK activity, since blocking p38 MAPK activity with a dominant negative form of p38 MAPK has no effect on TGFbeta/Smad signaling. Our results show that use of PD169316 at 5 MICROM or higher can block TGFbeta signaling activity and thus caution must be used when attributing cellular activities exclusively to p38 MAPK signaling when these inhibitors are used experimentally.

Smad 3 regulates proliferation of the mouse ovarian surface epithelium

Smad 3 is a signaling intermediate for the transforming growth factor beta (TGFbeta) family; however, little is known about the role this protein plays in the regulation of the ovarian surface epithelium (OSE). Using a transgenic mouse model, we found that in the absence of Smad 3 there was a distinct morphological alteration of OSE cells. Wild-type (WT) OSE was flat with thin cells, while Smad 3-deficient (Smad 3 -/-) OSE was thick with plump cuboidal cells. WT OSE had less immunostaining for proliferating cell nuclear antigen (PCNA) and estrogen receptor alpha (ERalpha) than Smad 3 -/- OSE. However, there were no differences in the number of apoptotic cells or Bax and Bcl-2 levels between WT and Smad 3 -/- OSE. Although WT mice had higher levels of serum estradiol than Smad 3 -/- mice, WT and Smad 3 -/- mice had similar levels of progesterone. These data suggest that Smad 3 regulates OSE morphological appearance and proliferation in the absence of high serum estradiol levels or alterations in progesterone levels.

Identification of a putative autocrine bone morphogenetic protein-signaling pathway in human ovarian surface epithelium and ovarian cancer cells

Bone morphogenetic proteins (BMPs) are members of the TGFbeta superfamily of cytokines that are involved in development, differentiation, and disease. In an analysis of normal ovarian surface epithelium (OSE) and ovarian cancer (OC) cells, we observed BMP4 mRNA expression and found that primary OC cells produce mature BMP4. In addition, each member of the downstream signaling pathway was expressed in primary OSE and OC cells. Smad1 was phosphorylated and underwent nuclear translocation in normal OSE and OC cells upon treatment with BMP4. Interestingly, the BMP target genes ID1 and ID3 were up-regulated 10- to 15-fold in primary OC cells, compared with a 2- to 3-fold increase in normal OSE. The growth of several primary OC cells was relatively unaltered by BMP4 treatment; however, long-term BMP4 treatment of primary OC cells resulted in decreased cell density as well as increased cell spreading and adherence. These data demonstrate the existence and putative function of BMP signaling in normal OSE and OC cells, and thus the continued examination of BMP4 signaling in the regulation of these two processes will be critical to further our current understanding of the role of BMP biology in OC pathogenesis.

Inhibition of the antiproliferative effect of TGFbeta by EGF in primary human ovarian cancer cells

The majority of ovarian cancers (OCs) arise from the ovarian surface epithelium (OSE). Proliferation of the OSE can be regulated by a number of autocrine and paracrine factors, including transforming growth factor beta (TGFbeta). Defects in the TGFbeta signaling pathway have been implicated in a number of cancers, including ovarian. We previously found that the TGFbeta signaling pathway is intact and functional in primary human OC cells, and that these cells stop growing in response to TGFbeta. Ovarian cancer cells in vivo are exposed to TGFbeta, yet continue to proliferate, therefore, mechanisms must exist to inhibit TGFbeta signaling contributing to uncontrolled cellular proliferation. Numerous signaling pathways converge with the TGFbeta pathway to modulate its effects, including signaling induced by epidermal growth factor (EGF). We hypothesized that EGF can modulate TGFbeta signaling and contribute to uncontrolled cellular proliferation of OC cells. Our results show that EGF abrogates the antiproliferative effect of TGFbeta. EGF does not modulate TGFbeta signaling by inhibiting receptor-activated Smad (R-Smad) phosphorylation or nuclear translocation. Rather, EGF decreases TGFbeta-induced mRNA expression of the cell cycle regulator, p15(INK4B), contributing to decreased sensitivity of OC cells to the antiproliferative effect of TGFbeta.

Primary culture and mRNA analysis of human ovarian cells

Established cell lines are invaluable for studying cell and molecular biological questions. A variety of human ovarian cancer (OC) cell lines exist, however, most have acquired significant genetic alterations from their cells of origin, including deletion of important cell cycle regulatory genes. In order to analyze signaling events related to cell cycle control in human OC, we have modified existing protocols for isolating and culturing OC cells from patient ascites fluid and normal ovarian surface epithelial (OSE) cells from benign ovarian tissue sections. These cells maintain an epithelial phenotype and can be manipulated experimentally for several passages before cellular senescence. An example using TGFb1 treatment of OC cells to examine signaling and target gene activation is presented.