Ovarian carcinomas: CCN genes are aberrantly expressed and CCN1 promotes proliferation of these cells

Extracellular matrix protein CCN1 limits oncolytic efficacy in glioma

Oncolytic viral therapy has been explored widely as an option for glioma treatment but its effectiveness has remained limited. Cysteine rich 61 (CCN1) is an extracellular matrix (ECM) protein elevated in cancer cells that modulates their adhesion and migration by binding cell surface receptors. In this study, we examined a hypothesized role for CCN1 in limiting the efficacy of oncolytic viral therapy for glioma, based on evidence of CCN1 induction that occurs in this setting. Strikingly, we found that exogenous CCN1 in glioma ECM orchestrated a cellular antiviral response that reduced viral replication and limited cytolytic efficacy. Gene expression profiling and real-time PCR analysis revealed a significant induction of type-I interferon responsive genes in response to CCN1 exposure. This induction was accompanied by activation of the Jak/Stat signaling pathway, consistent with induction of an innate antiviral cellular response. Both effects were mediated by the binding of CCN1 to the cell surface integrin α6β1, activating its signaling and leading to rapid secretion of interferon-α, which was essential for the innate antiviral effect. Together, our findings reveal how an integrin signaling pathway mediates activation of a type-I antiviral interferon response that can limit the efficacy of oncolytic viral therapy. Furthermore, they suggest therapeutic interventions to inhibit CCN1-integrin α6 interactions to sensitize gliomas to viral oncolysis.

Cyr61 expression in osteosarcoma indicates poor prognosis and promotes intratibial growth and lung metastasis in mice

Osteosarcoma is the most frequent primary malignant bone tumor in children and adolescents with a high propensity for lung metastasis, the major cause of disease-related death. Reliable outcome-predictive markers and targets for osteosarcoma metastasis-suppressing drugs are urgently needed for more effective treatment of metastasizing osteosarcoma, which has a current mean 5-year survival rate of approximately 20%. This study investigated the prognostic value and the biological relevance of the extracellular matrix-associated growth factor Cyr61 of the CCN family of secreted proteins in osteosarcoma and metastasis. The prognostic value of Cyr61 was assessed with Kaplan-Meier analyses based on Cyr61 immunostaining of a tissue microarray of osteosarcoma biopsies collected from 60 patients with local or metastatic disease. Effects of Cyr61 overexpression on intratibial tumor growth and lung metastasis of the low metastatic human SaOS-2 osteosarcoma cell line were examined in severe combined immunodeficiency (SCID) mice. Cyr61-provoked signaling was studied in vitro in nonmanipulated SaOS-2 cells. Cyr61 immunostaining of osteosarcoma tissue cores correlated significantly (p = 0.02) with poor patient survival. Mice intratibially injected with Cyr61-overexpressing SaOS-2 cells showed faster tumor growth and an increase in number and outgrowth of lung metastases and consequently significantly (p = 0.0018) shorter survival than mice injected with control SaOS-2 cells. Cyr61-evoked PI-3K/Akt/GSK3β signaling in SaOS-2 cells resulted in a subcellular redistribution of the cell cycle inhibitor p21(Cip1/WAF1). Cyr61 has considerable potential as a novel marker for poor prognosis in osteosarcoma and is an attractive target for primary tumor- and metastases-suppressing drugs.

Taking aim at the extracellular matrix: CCN proteins as emerging therapeutic targets

Members of the CCN family of matricellular proteins are crucial for embryonic development and have important roles in inflammation, wound healing and injury repair in adulthood. Deregulation of CCN protein expression or activities contributes to the pathobiology of various diseases - many of which may arise when inflammation or tissue injury becomes chronic - including fibrosis, atherosclerosis, arthritis and cancer, as well as diabetic nephropathy and retinopathy. Emerging studies indicate that targeting CCN protein expression or signalling pathways holds promise in the development of diagnostics and therapeutics for such diseases. This Review summarizes the biology of CCN proteins, their roles in various pathologies and their potential as therapeutic targets.

CYR61 controls p53 and NF-κB expression through PI3K/Akt/mTOR pathways in carboplatin-induced ovarian cancer cells

CYR61 over-expression promotes cell proliferation by inhibiting carboplatin-induced apoptosis, decreasing Bax expression, and increasing Bcl-xL, Mcl-1, and Bcl-2. At the same time, down-regulating p53 expression, while up-regulated NF-κB expression. Additionally, p21 and p53 promoter activities were reduced, while NF-κB and Bcl-2 activities increased. In parallel, CYR61-expressing cells, during carboplatin-induced apoptosis, resulted in an increase of Akt phosphorylation, while rapamycin-treated cells were not affected. Carboplatin effectively inhibited the activation of mTOR signaling cascade, which includes mTOR, 4E-BP1, p70S6K, HIF-1α, and VEGF. These results provide evidence that CYR61 promotes cell proliferation and inhibits apoptosis.

CCN1/CYR61: the very model of a modern matricellular protein

CCN1 (CYR61) is a dynamically expressed, multifunctional matricellular protein that plays essential roles in cardiovascular development during embryogenesis, and regulates inflammation, wound healing and fibrogenesis in the adult. Aberrant CCN1 expression is associated with myriad pathologies, including various cancers and diseases associated with chronic inflammation. CCN1 promotes diverse and sometimes opposing cellular responses, which can be ascribed, as least in part, to disparate activities mediated through its direct binding to distinct integrins in different cell types and contexts. Accordingly, CCN1 promotes cell proliferation, survival and angiogenesis by binding to integrin α(v)β(3), and induces apoptosis and senescence through integrin α(6)β(1) and heparan sulfate proteoglycans. The ability of CCN1 to trigger the accumulation of a robust and sustained level of reactive oxygen species underlies some of its unique activities as a matrix cell-adhesion molecule. Emerging studies suggest that CCN1 might be useful as a biomarker or therapeutic target in certain diseases.

Multivariate survival analysis of the patients with recurrent endometrial cancer

Objective

Few studies on the prognosticators of the patients with recurrent endometrial cancer after relapse have been reported in the literature. The aim of this study was to determine the prognosticators after relapse in patients with recurrent endometrial cancer who underwent primary complete cytoreductive surgery and adjuvant chemotherapy.

Methods

Thirty-five patients with recurrent endometrial cancer were included in this retrospective analysis. The prognostic significance of several clinicopathological factors including histologic type, risk for recurrence, time to relapse after primary surgery, number of relapse sites, site of relapse, treatment modality, and complete resection of recurrent tumors were evaluated. Survival analyses were performed by Kaplan-Meier curves and the log-rank test. Independent prognostic factors were determined by multivariate Cox regression analysis.

Results

Among the clinicopathological factors analyzed, histologic type (p=0.04), time to relapse after primary surgery (p=0.03), and the number of relapse sites (p=0.03) were significantly related to survival after relapse. Multivariate analysis revealed that time to relapse after primary surgery (hazard ratio, 6.8; p=0.004) and the number of relapse sites (hazard ratio, 11.1; p=0.002) were independent prognostic factors for survival after relapse. Survival after relapse could be stratified into three groups by the combination of two independent prognostic factors.

Conclusion

We conclude that time to relapse after primary surgery, and the number of relapse sites were independent prognostic factors for survival after relapse in patients with recurrent endometrial cancer.

CYR61 downregulation reduces osteosarcoma cell invasion, migration, and metastasis

Osteosarcoma is the most common primary tumor of bone. The rapid development of metastatic lesions and resistance to chemotherapy remain major mechanisms responsible for the failure of treatments and the poor survival rate for patients. We showed previously that the HMGCoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase inhibitor statin exhibits antitumoral effects on osteosarcoma cells. Here, using microarray analysis, we identify Cyr61 as a new target of statins. Transcriptome and molecular analyses revealed that statins downregulate Cyr61 expression in human and murine osteosarcoma cells. Cyr61 silencing in osteosarcoma cell lines enhanced cell death and reduced cell migration and cell invasion compared with parental cells, whereas Cyr61 overexpression had opposite effects. Cyr61 expression was evaluated in 231 tissue cores from osteosarcoma patients. Tissue microarray analysis revealed that Cyr61 protein expression was higher in human osteosarcoma than in normal bone tissue and was further increased in metastatic tissues. Finally, tumor behavior and metastasis occurrence were analyzed by intramuscular injection of modified osteosarcoma cells into BALB/c mice. Cyr61 overexpression enhanced lung metastasis development, whereas cyr61 silencing strongly reduced lung metastases in mice. The results reveal that cyr61 expression increases with tumor grade in human osteosarcoma and demonstrate that cyr61 silencing inhibits in vitro osteosarcoma cell invasion and migration as well as in vivo lung metastases in mice. These data provide a novel molecular target for therapeutic intervention in metastatic osteosarcoma.

Functional Characterization of a Fluorescent Highly Tumorigenic Ovarian Cancer Line to Test Cellular Therapy in Experimental Models

Objectives

The objective of this study was to functionally characterize a fluorescent highly tumorigenic ovarian cancer line to test cellular therapy in combination with cytokines or chemotherapies in experimental models.

Methods

A fluorescent highly tumorigenic subline (SKOV3-AF2) was derived from the SKOV3 ovarian cancer cell line. Peripheral blood mononuclear cell (PBMC)-mediated cytotoxicity of SKOV3-AF2 in the presence of interleukin 2 (IL-2) and interferon α-2b (IFNα-2b) was assayed by lactate dehydrogenase release. Sensitivity of SKOV3-AF2 cells to polyethylene glycol-IFNα-2b and IL-2 was assayed in a xenograph nude mouse model. Histopathology was performed to determine necrosis and tumor-infiltrating lymphocytes in the solid tumors. Reverse transcriptase-polymerase chain reaction was used for gene expression analyses ofE-cadherinandcysteine-rich 61(CCN1).

Results

The SKOV3-AF2 subline exhibits increased cytotoxicity (up to 70%), mediated by PBMCs, IL-2, and IFNα-2b, compared with parental SKOV3-red fluorescent protein (RFP) cells. SKOV3-AF2 cells are more tumorigenic in vivo as indicated by tumor incidence, time to sacrifice, tumor weight, and ascitic fluid production. SKOV3-AF2 tumor growth was inhibited by polyethylene glycol-IFNα-2b but not low-dose IL-2. Histopathology revealed that the tumors consisted of poorly differentiated surface epithelial carcinoma. SKOV3-RFP, and -AF2 cell lines as well as -AF2 tumors expressedE-cadherin.SKOV3-AF2 derived tumors expressedCCN1; however, the SKOV3-RFP and SKOV3-AF2 cell lines did not.

Conclusions

Characterization of SKOV3-AF2 cells revealed that it is more susceptible to PBMC-mediated cytotoxicity than SKOV3-RFP and highly tumorigenic in a xenograph model, and AF-2 tumors express genes that promote aggressive behavior. Collectively, our data suggest that the SKOV3-AF2 subline will be a useful tool to test cellular therapy for the treatment of ovarian cancer utilizing experimental models.

Expression of Cyr61 (CCN1) in human oral squamous cell carcinoma: An independent marker for poor prognosis

BACKGROUND

Cysteine-rich 61 (Cyr61 [CCN1]) has disparate functions in tumorigenesis that are dependent on the cell types. The aim of the study was to investigate its role in the growth of oral squamous cell carcinoma (SCC).

METHODS

The study used immunohistochemistry to examine Cyr61 expression in 93 oral SCC specimens and assessed the effect of Cyr61 overexpression on proliferation and migration of oral SCC cells in vitro and xenograft growth in severe combined immunodeficient (SCID) mice.

RESULTS

High expression of Cyr61 significantly correlated with large tumor size (p = .009) and advanced tumor stage (p = .036). Multivariate analysis revealed that high Cyr61 (relative risk [RR] 2.44, 95% confidence interval [CI] 1.209-4.95, p = .010) significantly correlated with mortality. Forced expression of Cyr61 stimulated the motility and growth of Ca9-22 cells in vitro and enhanced xenograft growth in SCID mice.

CONCLUSIONS

Cyr61 is a positive growth modulator of oral SCC and Cyr61 overexpression is an independent prognostic indicator for patients with oral SCC.

Arecoline stimulated Cyr61 production in human gingival epithelial cells: inhibition by lovastatin

Cyr61 is associated with growth and progression of many types of tumors and is an independent poor prognostic indicator for oral cancer patients. Areca nut (AN) chewing is the most important etiological factor in the pathogenesis of oral cancer in India and many Southeast Asian countries. Yet, the molecular mechanisms involved in the AN-induced oral cancer remain largely unknown. In this study, we show that arecoline, a main alkaloid found in AN, stimulated Cyr61 synthesis in human gingival epithelial S-G cells. Constitutive overexpression of Cyr61 protein in oral epithelial cells during AN chewing may play a role in the pathogenesis of oral cancer. ERK inhibitor PD98059, N-acetyl-L-cysteine, Rho-associated protein kinase (ROCK) selective inhibitor Y-27632 and a geranylgeranyltransferase inhibitor reduced the arecoline-stimulated levels of Cyr61 protein by ∼31%, 47%, 65% and 100%, respectively. Lovastatin also completely inhibited arecoline-induced Cyr61 synthesis and the inhibition is dose-dependent. Decreased of geranylgeranylated proteins could be the mechanism that lovastatin regulates Cyr61 synthesis and lovastatin could serve as a useful agent in controlling AN-induced oral cancer.

[Expressions of Cyr61 and WISP-3 in non-small cell lung cancer and its clinical significance]

背景与目的

Cyr61是非小细胞肺癌（non-small cell lung cancer, NSCLC）生长过程中的一个肿瘤抑制基因，Cyr61与WISP-3同属于CCN基因家族，具有极其明显的序列同源性。本研究通过检测Cyr61和WISP-3在NSCLC组织中的表达，探讨其临床意义。

方法

应用免疫组化SP染色法检测54例NSCLC癌组织和癌旁正常肺组织中Cyr61和WISP-3的表达，并结合临床参数进行分析。

结果

在NSCLC癌组织中Cyr61表达水平低于癌旁正常肺组织（P < 0.001），WISP-3表达水平高于癌旁正常肺组织（P < 0.001）；NSCLC癌组织中Cyr61与WISP-3蛋白表达呈负相关（r=-0.395, P=0.003）；Cyr61的表达与肿瘤的组织学分化程度、病理类型、临床分期、家族史、吸烟史和淋巴结转移有关（P < 0.05）；WISP-3阳性表达率与肿瘤的组织学分化程度、临床分期和年龄有关（P < 0.05）。

结论

Cyr61和WISP-3可能是反映NSCLC进展、生物学行为、转移发生及预后的重要生物学标记物。

Predicting response of bladder cancers to gemcitabine and carboplatin neoadjuvant chemotherapy through genome-wide gene expression profiling

Neoadjuvant chemotherapy with gemcitabine and carboplatin (GC) for invasive bladder cancer increases the chance of a radical response for a subset of patients, while other patients suffer from severe adverse drug reactions without any benefit. To establish a method for predicting the response to chemotherapy with GC, the expression profiles of biopsy samples from 37 advanced bladder cancers were analyzed using a microarray consisting of 38,500 genes or ESTs. Upon analysis of 9 'responder' and 9 'non-responder' tumors, 12 'predictive' genes were found to be significantly differentially expressed between the 'responder' and 'non-responder' groups, and a numerical prediction scoring system that clearly separated the responder group from the non-responder group was established. This system accurately predicted the drug responses of 18 of 19 additional test cases that were reserved from the original 37 cases. Moreover, a quantitative PCR-based prediction system was developed that may be feasible for routine clinical use, and the sensitivity of invasive bladder cancer to neoadjuvant chemotherapy with GC was able to be predicted by the expression patterns in this set of genes. Nearly 50% of patients treated with GC or methotrexate, vinblastine, doxorubicin and cisplatin (M-VAC) therapy have been reported to achieve complete or partial response to either of these therapies. When we applied this prediction system as well as the system for M-VAC, we expected that approximately 80% of the patients would achieve significant tumor shrinking (>60%) by selection of either the GC or M-VAC regimens. Our results suggest that the two prediction scoring systems lead to achievement of 'personalized therapy' for the treatment of invasive bladder cancer and should improve the quality of life for patients with this disease.

Inhibition of AP-1 by SARI negatively regulates transformation progression mediated by CCN1

Enhanced expression of the CCN family of secretory integrin-binding proteins correlates with many essential components of the cancerous state, including tumor cell adhesion, proliferation, invasion and migration. Consequently, CCN1 expression is elevated in various cancers, including breast cancer, and its expression directly correlates with poor patient prognosis. Using subtraction-hybridization, combined with induction of cancer cell terminal differentiation, we cloned SARI (suppressor of activator protein (AP)-1, regulated by interferon (IFN)), an IFN-beta-inducible, potent tumor suppressor gene that exerts cancer-selective growth inhibitory effects. Forced expression of SARI using an adenovirus (Ad.SARI) inhibits AP-1 function and downregulates CCN1 expression in multiple cancer lineages, resulting in a profound inhibition in anchorage-independent cell growth and tumor cell invasion. Overexpression of SARI reduces CCN1-promoter activity through inhibition of AP-1 binding. Accordingly, SARI selectively blocks expression of the transformed state in rat embryo fibroblast cells that stably overexpress c-Jun. These results illustrate that SARI inhibits AP-1 transactivating factor binding to the cis-element of the CCN1 promoter, possibly through its interaction with c-Jun. Overall, SARI can directly inhibit CCN1-induced transformation by inhibiting the transcription of CCN1, as well as indirectly by inhibiting the expression of c-Jun (and hence blocking AP-1 activity). In these contexts, transformed cells 'addicted' to AP-1 activity are rendered susceptible to SARI-mediated inhibition of expression of the transformed phenotype.

Involvement of CYR61 and CTGF in the fascin-mediated proliferation and invasiveness of esophageal squamous cell carcinomas cells

Fascin is overexpressed in esophageal squamous cell [corrected] carcinoma (ESCC) and involved in the proliferation and invasiveness of ESCC cells. In this study, we retrospectively examined the expression of fascin in ESCC samples by immunohistochemistry and revealed that overexpression of fascin was related to poor patient survival. RNAi-mediated knockdown of fascin in ESCC cells significantly inhibited cell proliferation and invasiveness, whereas forced expression of fascin in immortalized esophageal epithelial cells accelerated cell proliferation and invasiveness. To explore the underlying mechanism, cDNA microarray was performed to identify the differential gene expression profiles between a fascin-depleted cell line by RNAi and the corresponding control ESCC cells. Results showed that 296 genes were differentially expressed on fascin depletion. In this study, we focused on two down-regulated genes: CYR61 and CTGF. We found that restored expression of either CYR61 or CTGF led to a recovery of the suppression of cellular proliferation and invasiveness induced by down-regulation of fascin expression; the protein level of CYR61 and CTGF were up-regulated in ESCCs and their expression pattern correlated with fascin overexpression. Finally, analysis of signal transduction revealed that fascin affected the expressions of CYR61 and CTGF through transforming growth factor (TGF)-beta pathway. Taken together, we propose that fascin regulates the proliferation and invasiveness of ESCC cells by modulating the expression of CTGF and CYR61 via TGF-beta pathway.

Reprogramming of the transcriptome in a novel chromosome 3 transfer tumor suppressor ovarian cancer cell line model affected molecular networks that are characteristic of ovarian cancer

Tumor suppression as a consequence of the transfer of chromosome 3p fragments was previously observed in a novel epithelial ovarian cancer (EOC) OV-90 cell line model harboring loss of 3p. Microarray analysis revealed that tumor suppression was associated with a modified transcriptome. To investigate the relevance of the altered transcriptome, the differentially expressed genes identified by Affymetrix analysis in the 3p transfer studies, were integrated with a comparative microarray analysis of normal ovarian surface epithelial (NOSE) cells and malignant ovarian (TOV) cancers. Data from 219 significantly differentially expressed genes exhibited patterns in the direction predicted by the analysis of 3p transfer study. The 30 genes with the highest statistically significant differences (P < 1 x 10(-8)) in expression were found consistently differentially expressed between NOSE and TOV samples. The investigation of these genes in benign serous ovarian tumors and EOC cell lines also exhibited predictable expression patterns. Within the group of differentially expressed genes were SPARC, DAB2, CP, EVI1, ELF3, and EHD2, known to play a role in ovarian cancer, genes implicated in other cancers, such as GREM1 and GLIPR1, as well as genes not previously reported in a cancer context such as AKAP2 and ATAD4. A number of the differentially expressed genes are implicated in the TGF-beta signaling pathway. These findings suggest that the reprogramming of the transcriptome that occurred as a consequence of the chromosome 3 transfer and tumor suppression affected molecular networks that are characteristic of ovarian carcinogenesis thus validating our novel ovarian cancer cell line model.

Transcriptome profiling and network pathway analysis of genes associated with invasive phenotype in oral cancer

The aim of this study was to clarify relevant alterations of gene expression associated with the invasive phenotype of oral cancer. To reduce heterogeneity and to obtain data on genes specifically involved in invasive mechanism, we established a highly invasive ORC subline through in vitro Matrigel invasion method. Affymetrix microarrays were used for transcriptome profiling between parental and the highly invasive subline. Seventy-nine genes were differentially expressed at least 2-fold, including 38 up-regulated and 41 down-regulated. After analyzing the microarray data by MetaCore algorithm, a total of 12 regulatory pathways were found to be associated with invasive phenotype (p<0.001). Two functional pathways were most significant: the cell adhesion through extracellular matrix remodeling (p=4.964e-06), and MHC-class-I mediated antigen presentation (p=9.843e-05). To shed more light on the biological functions of invasiveness, two genes highly over-expressed in the invasive subline, Cyr61 and CD44 were further validated. RNAi knockdown of these two genes led to significant suppression of cell growth (32% and 31%, respectively at day 3), cell migration (45% and 96%, respectively at 24 h), and cell invasion (83% and 87%, respectively at day 3). These results suggested important roles of these genes in regulating invasive phenotype, and demonstrated the confidence of this study design in the search of invasive associated genes. The identified pathways associated with invasion mechanism may be novel targets for manipulation of the cancer behavior with consequences on treatment outcome.

Cyr61, a member of ccn (connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed) family, predicts survival of patients with endometrial cancer of endometrioid subtype

OBJECTIVES

It has been reported that expression of Cyr61 decreased in endometrial cancers and cancer cell lines compared with normal endometrium, and forced expression of Cyr61 could suppress the growth of human endometrial cancer cells. However, in another report, Cyr61 was immunostained in most of endometrial cancer tissues analyzed. Thus, the aim of this study was to examine the expression of Cyr61 in endometrial cancer and to correlate Cyr61 expression with cinicopathologic factors in a larger cohort.

METHODS

We used immunohistochemistry and RT-PCR to examine the expression of Cyr61 in 92 endometrial carcinomas of endometrioid subtype. We correlated the expression of Cyr61 with various clinicopathologic factors in patients with endometrioid adenocarcinoma. Survival analyses were performed by the Kaplan Meier curves and the log-rank test. Independent prognostic factors were determined by multivariate Cox regression analysis.

RESULTS

Cyr61 expression was high in 21 of 92 cases of endometrioid adenocarcinoma (22.8%). High expression of Cyr61 was related to poor survival of patients with endometrioid adenocarcinoma. Multivariate analysis including Cyr61 expression revealed that Cyr61 expression and positive lymph node metastasis (LNM) were independent prognostic factors for survival. Survival of patients with endometrioid adenocarcinoma could be stratified into three groups by combination of Cyr61 expression and positive LNM with an estimated 5-year survival rate of 96.5% for no LNM irrespective of Cyr61 expression (group A), 85.7% for positive LNM with low/moderate expression of Cyr61 (group B), and 0% for positive LNM with high expression of Cyr61 (group C)(p=0.18 for group A vs group B, p=0.008 for group B vs group C, and p<0.0001 for group A vs group C).

CONCLUSIONS

Cyr61 is highly expressed in some endometrial cancer of endometrioid subtype. Cyr61 expression and positive LNM were independent prognostic factors for patients with endometrioid adenocarcinoma. Cyr61 might be a new molecular marker to predict the prognosis of patients with endometrioid adenocarcinoma.

Functions and mechanisms of action of CCN matricellular proteins

Members of the CCN (CYR61/CTGF/NOV) family have emerged as dynamically expressed, extracellular matrix-associated proteins that play critical roles in cardiovascular and skeletal development, injury repair, fibrotic diseases and cancer. The synthesis of CCN proteins is highly inducible by serum growth factors, cytokines, and environmental stresses such as hypoxia, UV exposure, and mechanical stretch. Consisting of six secreted proteins in vertebrate species, CCNs are typically comprised of four conserved cysteine-rich modular domains. They function primarily through direct binding to specific integrin receptors and heparan sulfate proteoglycans, thereby triggering signal transduction events that culminate in the regulation of cell adhesion, migration, proliferation, gene expression, differentiation, and survival. CCN proteins can also modulate the activities of several growth factors and cytokines, including TGF-beta, TNFalpha, VEGF, BMPs, and Wnt proteins, and may thereby regulate a broad array of biological processes. Recent studies have uncovered novel CCN activities unexpected for matricellular proteins, including their ability to induce apoptosis as cell adhesion substrates, to dictate the cytotoxicity of inflammatory cytokines such as TNFalpha, and to promote hematopoietic stem cell self-renewal. As potent regulators of angiogenesis and chondrogenesis, CCNs are essential for successful cardiovascular and skeletal development during embryogenesis. In the adult, the expression of CCN proteins is associated with injury repair and inflammation, and has been proposed as diagnostic or prognostic markers for diabetic nephropathy, hepatic fibrosis, systemic sclerosis, and several types of cancer. Targeting CCN signaling pathways may hold promise as a strategy of rational therapeutic design.

Aromatase inhibitors in ovarian cancer: is there a role?

Estrogen plays a role in ovarian tumorigenesis. Aromatase is the enzyme required for the synthesis of estrogen via conversion of androgen to estrogen, which is the major source of estrogen in postmenopausal women. Aromatase is present in normal ovaries and other tissues (e.g., fat and muscle) as well as in 33-81% tumor tissues of ovarian cancer. Aromatase inhibitors (AIs) block estrogen synthesis by inhibiting aromatase activity. In patients with recurrent ovarian cancer, single-agent AI therapy has been shown to elicit clinical response rates of up to 35.7% and stable disease rates of 20-42%. Given the limited treatment options for recurrent ovarian cancer and the favorable safety profile and convenient use, AI is a rational option for prolonging platinum-free interval in recurrent ovarian cancer. Further studies are required to determine the efficacy of combination treatment with AIs and biological agents, determine the benefit of AIs for treating special types of ovarian cancer (e.g., endometrioid type), and identify biomarkers for targeted patient selection. This review summarizes the current epidemiologic, preclinical, and clinical data regarding estrogen's role in ovarian cancer, the expression and regulation of aromatase in this disease, the development and characteristics of the three generations of AIs, and the preclinical and clinical studies of AIs in the treatment of ovarian cancer.

Erythropoietin treatment of human ovarian cancer cells results in enhanced signaling and a paclitaxel-resistant phenotype

Erythropoietin (Epo), a glycoprotein hormone that is the principal regulator of erythropoiesis, is known to act also on nonhematopoietic cell types. Epo receptors have been reported on several normal and neoplastic human cells and tissues, including ovarian cancer cells. We found that long-term Epo treatment of A2780 cells resulted in the development of a phenotype exhibiting both enhanced Epo signaling, evidenced by increased peak levels of phospho-Erk1/2 and increased paclitaxel resistance. This phenotypic effect was specific for paclitaxel, since no change in cisplatin or carboplatin sensitivity was observed. In addition, the change in phenotype was stable, even after the removal of Epo. Measurement of mono- and oligonucleosome formation revealed that long-term Epo treated A2780 cells exhibited markedly less apoptosis than nonerythropoietin treated cells at essentially all concentrations of paclitaxel tested. Western blot analyses revealed that the long-term Epo treated cells had significantly reduced expression of apoptosis-related proteins Bcl-2 and Bcl-10. These findings may have implications for the clinical use of recombinant human Epo and other erythropoiesis stimulating agents to correct anemia in paclitaxel-treated cancer patients.

Characterization of erythropoietin receptor and erythropoietin expression and function in human ovarian cancer cells

The identification of erythropoietin receptors (EpoR) on cancer cells has caused concern, since it implies the possibility that treatment of cancer patients with erythropoietin (Epo) and related agents with demonstrable antiapoptotic activity could enhance cancer growth and progression. However, the function and even the validity of the identification of these receptors have been called into question. We now report the characterization of EpoR and Epo expression by 4 human ovarian cancer cell lines: A2780, CaOV, SKOV and OVCAR-3. Using semiquantitative RT-PCR, restriction digestion of the PCR products and DNA sequence analysis, we determined that each of the lines expresses the EpoR and Epo at the mRNA level. A2780 cells were the highest expressers of both genes. We demonstrated EpoR protein both by western blotting and by immunofluorescence and biologically active Epo protein by quantitative in vitro bioassay. The EpoR on A2780 cells was shown to be functional, since Epo stimulation resulted in phosphorylation of Erk1/2, an important EpoR mitogenic signaling intermediate. None of the cell lines exhibited a growth response in culture to exogenous Epo. However, addition of a neutralizing anti-Epo antibody to A2780 cells resulted in partial growth inhibition that was reversed by the addition of excess Epo, providing evidence for an autocrine/paracrine mechanism of growth enhancement in these cells.

Endometrial Expression of Cyr61

OBJECTIVE

To compare the expression of Cyr61 in normal cycling endometrium with endometrium from women with polycystic ovarian syndrome (PCOS) and endometrial hyperplasia and adenocarcinoma.

METHODS

This is a retrospective study of 59 samples of normal and abnormal endometrium. Endometrial biopsies were obtained from normal fertile controls throughout the menstrual cycle and compared with endometrium from ovulatory and anovulatory women with PCOS and complex endometrial hyperplasia and endometrioid adenocarcinoma. Cyr61 expression was evaluated by using immunohistochemistry and reverse transcription PCR for Cyr61, estrogen receptor (ER)-alpha, a marker of cell proliferation (Ki67), and another marker of early estrogen action, cFos. Regulation of Cyr61 protein was studied in a steroid-responsive endometrial carcinoma cell line, ECC1.

RESULTS

Cyr61 protein was regulated by estrogen. In normal endometrium, Cyr61 was highest in the proliferative phase and lowest in the normal midsecretory phase. In contrast, elevated levels of Cyr61, ER-alpha, Ki67, and cFos were all found in the midsecretory endometrium of ovulatory PCOS patients, endometrial cancer patients, and hyperplasia patients.

CONCLUSION

Cyr61 is overexpressed in PCOS endometrium, reflecting a heightened responsiveness to estrogen. As a unique marker of estrogen action, Cyr61 may be an early biomarker for the development of hyperplasia or adenocarcinoma in this group of women.

RTP801 is a novel retinoic acid–responsive gene associated with myeloid differentiation

OBJECTIVE

Retinoids are crucial in the regulation of fundamental cellular processes including terminal differentiation of both normal and malignant myeloid progenitors. The aim of this study was to identify and characterize retinoic acid (RA) target genes.

METHODS AND RESULTS

RTP801 is a recently cloned stress response gene that acts as a negative regulator of the mTOR pathway. Here we identified RTP801 as a novel early RA target gene in myeloid cells. RTP801 mRNA levels are induced in acute myeloid leukemia (AML) cell lines during RA-dependent differentiation and are differentially expressed during maturation of normal CD34(+) cells. The myeloid-specific, differentiation-related transcription factor C/EBPepsilon also induces RTP801 expression. Overexpression of RTP801 in the U937 leukemic cells leads to growth inhibition and apoptosis. Conversely, silencing of endogenous RTP801 by shRNA reduces RA-induced differentiation of the U937 cells. Downregulation of RTP801 also abrogates hypoxia-induced inhibition of mTOR in those cells.

CONCLUSION

Taken together, our data suggest that RTP801 is an important RA-regulated gene involved in myeloid differentiation, which could represent a therapeutic target in leukemia.

The 5' untranslated regions (UTRs) of CCN1, CCN2, and CCN4 exhibit cryptic promoter activity

CCNs are structurally related matricellular proteins that are highly expressed in many embryonic and adult tissues, including the skeletal system and tumors, where canonical cap-dependent translation is suppressed under hypoxic environments. CCNs are encoded by mRNAs containing long G/C rich 5'-untranslated regions (5'-UTRs). Given that they are expressed under conditions of cellular stress, it has been suggested that the long G/C-rich regions contain internal ribosomal entry sites (IRES) that allow these mRNAS to be translated under conditions where cap-dependent translation is suppressed. Previously published work supported this possibility. However, recent studies have shown that a number of previously reported cellular IRES elements do not in fact possess IRES activity. Here we aimed to reveal whether the 5'UTRs of CCNs harbor IRES activities. The 5'UTRs of CCN1, 2, and 4 were tested in this study. Our results showed that the 5'UTRs of these genes do not contain IRES elements, but instead appear to contain cryptic promoters. Both promoterless and hairpin-containing dicistronic tests showed that transcription was initiated by cryptic promoter elements in 5'UTRs of CCN1, 2, and 4. When dicistronic mRNAs were translated in vitro or in vivo, no IRES activities were detected in the 5'UTRs of CCN1, 2, and 4. Furthermore, these cryptic promoter activities from 5'UTRs of CCN1, 2, and 4 could be detected in various cell types, including chondrocytes, osteoblasts, and endothelial cells, where the cryptic promoter permitted varying degrees of activation. In addition, the core promoter element of the CCN2 5'UTR was identified. CCNs are expressed under conditions of cellular stress, and it has been suggested that some CCN family members utilize IRES-mediated translation initiation to facilitate this expression. We found no evidence for IRES activity, but rather found that the unusually long 5'UTRs of CCNs 1, 2, and 4 harbor cryptic promoters that showed varying degrees of activity in different cell types. These results suggest that these promoters may contribute to the regulation of CCN genes in vivo.

All in the CCN family: essential matricellular signaling modulators emerge from the bunker

The CCN family is a group of six secreted proteins that specifically associate with the extracellular matrix. Structurally, CCN proteins are modular, containing up to four distinct functional domains. CCN family members are induced by growth factors and cytokines such as TGFβ and endothelin 1 and cellular stress such as hypoxia, and are overexpressed in pathological conditions that affect connective tissues, including scarring, fibrosis and cancer. Although CCN family members were discovered over a decade ago, the precise biological role, mechanism of action and physiological function of these proteins has remained elusive until recently, when several key mechanistic insights into the CCN family emerged. The CCNs have been shown to have key roles as matricellular proteins, serving as adaptor molecules connecting the cell surface and extracellular matrix (ECM). Although they appear not to have specific high-affinity receptors, they signal through integrins and proteoglycans. Furthermore, in addition to having inherent adhesive abilities that modulate focal adhesions and control cell attachment and migration, they execute their functions by modulating the activity of a variety of different growth factors, such as TGFβ. CCN proteins not only regulate crucial biological processes including cell differentiation, proliferation, adhesion, migration, apoptosis, ECM production, chondrogenesis and angiogenesis, but also have more sinister roles promoting conditions such as fibrogenesis.