Ovarian Cancer Cell Lines OVCAR3 Research Articles

Epidermal growth factor increases lysophosphatidic acid production in human ovarian cancer cells: roles for phospholipase D2 and receptor transactivation

Lysophosphatidic acid (LPA), is a lipid mediator that binds to G-protein coupled receptors. Epidermal growth factor (EGF), a polypeptide growth factor, binds to the EGF receptor (EGFR), a receptor tyrosine kinase. Both LPA and EGF induce responses in tumor cells that include proliferation, migration, metastasis, and induction of angiogenesis. LPA has the potential to act as an autocrine/paracrine factor and can transactivate the EGFR. This study explores the role of phospholipase D2 (PLD2) activation in LPA production, as well as cross-talk between EGF and LPA receptors. We demonstrate that EGF and LPA both stimulate production of LPA by OVCAR3 and SKOV3 human ovarian cancer cell lines. PD158780, an EGFR-selective tyrosine kinase inhibitor, blocks LPA production in response to both EGF and LPA in OVCAR3 and SKOV3 cells. Pertussis toxin, an inhibitor of LPA receptor signaling, inhibits LPA production in response to both EGF and LPA. Similar results were observed for the LPA receptor antagonist, Ki16425. Overexpression of PLD2 increases LPA production, while knockdown of PLD2 blocks EGF-induced LPA production. A phospholipase A2 (PLA2) inhibitor also blocks LPA- and EGF-induced LPA production. These results indicate that EGF stimulates LPA production in a manner that requires PLD2, and suggest that cross-talk can occur bidirectionally between EGF and LPA receptors.

Inhibition of human ovarian cancer cell lines by Devil's club Oplopanax horridus

Aim of the study To search for more effective treatment of ovarian cancer, we investigated the in vitro anti-proliferation activities of Devil's club (OH) root bark extracts, an important medicinal plant of North America, on cisplatin sensitive and resistant human ovarian cancer cell lines. Materials and methods High performance liquid chromatography was used to provide the chemical profiling of the OH extracts. The anti-proliferation activities of OH extracts alone or in combination with cisplatin or paclitaxel were determined on four human ovarian cell lines by crystal violet assay. Flow cytometry and light microscopy were employed for cell cycle analysis, and also to detect apoptosis. Results Our data showed that water, 70% ethanol, 100% ethanol, and ethyl acetate extracts of OH inhibited the proliferation of human ovarian cancer cell lines A2780, A2780CP70, OVCAR3, and OVCAR10 in vitro. The respective 50% inhibition (IC 50) was estimated at 1/256, 1/74, 1/69, 1/53; 1/4156, 1/1847, 1/1029, 1/4530; 1/25,753, 1/3310, 1/3462, 1/5049; and 1/29,916, 1/2912 1/3828, and 1/4232 dilutions. Some combinations of non-cytotoxic dilutions (<IC 50) of 70% ethanol OH extract with cisplatin and paclitaxel enhanced its anti-proliferation IC 50 on A2780 and A2780CP70 cells. Cell cycle analysis demonstrated that the effect of OH extract on cell cycle was dependent on the concentration tested, blocking cells in the S and G2/M phases. At low concentrations it induced cell death by apoptosis, while at high concentrations, it kills cells by necrosis. Conclusions Our data showed that OH extracts exhibited significant anti-proliferation effect against both cisplatin sensitive and resistant human ovarian cell lines. Further research might result in discovery of agent(s) that can potentially be useful as an adjunct therapy for ovarian cancer cells. It is one of the few North American medicinal herbs that have been tested for anti-ovarian cancer activities.

SP148 Emerging tissue-based cancer biomarkers in breast cancer

The presence of circulating tumor cells (CTCs) in the blood of ovarian cancer patients was shown to correlate with decreased overall survival, whereby CTCs with epithelial–mesenchymal-transition (EMT) or stem-like traits are supposed to be involved in metastatic progression and recurrence. Thus, investigating the transcriptional profiles of CTCs might help to identify therapy resistant tumor cells and to overcome treatment failure. For this purpose, we established a multi-marker panel for the molecular characterization of single CTCs, detecting epithelial (EpCAM, Muc-1, CK5/7), EMT (N-cadherin, Vimentin, Snai1/2, CD117, CD146, CD49f) and stem cell (CD44, ALDH1A1, Nanog, SOX2, Notch1/4, Oct4, Lin28) associated transcripts.First primer specificity and PCR-performance of the multiplex-RT-PCRs were successfully validated on genomic DNA and cDNA isolated from OvCar3 cells. The assay sensitivity of the epithelial panel was evaluated by adding defined numbers of tumor cells into the blood of healthy donors and performing a subsequent immunomagnetic tumor cell enrichment (AdnaTest OvarianCancerSelect), resulting in a 100% concordance for the epithelial markers EpCAM and Muc-1 to the AdnaTest OvarianCancerDetect. Additionally, by processing blood from ovarian cancer patients, high assay sensitivity could be verified. In blood of healthy donors no signals for epithelial markers were detected, for EMT and stem cell markers, however, signals were obtained mainly originating from leukocytes which calls for single cell analysis.To that aim by using the ovarian cancer cell line OvCar3, we successfully established a workflow enabling the characterization of single CTCs. It consists of a density gradient-dependent enrichment for nucleated cells, a depletion of CD45-positive cells of hematopoietic origin followed by immunofluorescent labeling of CTCs by EpCAM and Muc-1. Single CTCs are then isolated by micromanipulation and processed for panel gene expression profiling. Finally, fifteen single CTCs from three ovarian cancer patients were analyzed and found to be positive for stem cell (CD44, ALDH1A1, Nanog, Oct4) and EMT markers (N-cadherin, Vimentin, Snai2, CD117, CD146). Albeit, inter-cellular and intra/inter-patient heterogeneity and co-expression of epithelial, mesenchymal and stem cell transcripts on the same CTC was observed.We have established a robust workflow to perform sensitive single cell panel gene expression analysis without the need of pre-amplification steps. Our data point towards a heterogeneous expression of stem cell and EMT associated transcripts in ovarian cancer CTCs.

Cytotoxicity of natural extract from Tegillarca granosa on ovarian cancer cells is mediated by multiple molecules

To determine the cellular and molecular mechanism of cytotoxicity induced by Haishengsu (HSS), nature extract from Tegillarca granosa, toward human ovarian cancer cell lines SKOV-3 and OVCAR-3. The cytotoxic effects of HSS on two ovarian cancer cell lines were tested by XTT assay. Cell apoptosis and cell cycle arrest induced by HSS were demonstrated by DNA ladder assay and flow cytometric analysis, respectively. RT-PCR or flow cytometric analysis was used to investigate the expression of bcl-2, caspase-3, p53, beta-catenin, E-cadherin, CD24, and CD44. Continuous exposure to HSS for 48 h produced cytotoxic effects on both cell lines in a concentration dependent manner, which was accompanied by apoptosis and cell cycle arrest. Apoptosis associated gene bcl-2 and caspase-3, tumor metastasis associated gene ?-catenin, but not E-cadherin, and CD24, but not CD44, were involved in the effect of growth inhibition induced by HSS. Although p53 mediated apoptosis induced by HSS in OVCAR-3 cells, it was not required in SKOV-3 cells. HSS has a potential cytotoxic effect on human ovarian cancer cells, which was mediated by multiple signal molecules including bcl-2, caspase-3, beta-catenin, and CD24. These findings will provide a theoretical basis for HSS's potential clinical application as a novel marine anti-cancer agent.

Identification of Cancer Stem-like Side Population Cells in Ovarian Cancer Cell Line OVCAR-3

Side population (SP) cells may enrich stem-like cells in many normal and malignant tissues. However, SP method application has drawn special attention to the field of stem cell research, and the existence of SP cells in cell culture is being debated, most probably because different cell lines require different technical modifications, especially when cell staining is considered. In this study, the authors aimed to disclose whether the hoechst33342 staining required extensive optimization for identifying SP cells in the human ovarian cancer cell line OVCAR-3. After systematic evaluations, it was found that only 2.5 microg/mL hoechst33342 staining of the cells for 60 min could get an ideal SP population, which accounted for 0.9% of the whole cell population. The sorted SP cells showed significantly higher colony formation efficiency than the non-side population (NSP) cells, and only the SP cells could form holoclones. Real-time PCR disclosed that SP cells expressed higher levels of "stemness" gene Oct3/4 than the NSP cells did, indicating that the SP cells might harbor cancer stem cells in this cell line. The results highlight the necessity of SP method optimization in cell studies, and the SP cells in this cell line merit further studies when cancer stem cell identification and isolation are considered.

Inhibition of functional HER family members increases the sensitivity to docetaxel in human ovarian cancer cell lines

Human epidermal growth factor (HER) family-targeted therapy combined with standard cytotoxic agents might improve the treatment of ovarian cancer. Human ovarian cancer cell lines OVCAR-3, IGROV-1, and SKOV-3 with differential EGFR, HER2, and HER3 expression levels were used to study whether EGFR-directed (cetuximab) or HER2-directed (trastuzumab, pertuzumab) monoclonal antibodies inhibited cell growth and abrogated activated receptor signaling routes. Possible increase of antiproliferative effects and further activation of caspase-3 as a read-out for apoptosis were analyzed when monoclonal antibodies were combined with docetaxel. Cetuximab alone inhibited cell growth in OVCAR-3 and IGROV-1, which was more pronounced when combined with pertuzumab in OVCAR-3. SKOV-3 cell growth was not significantly affected by any of the antibodies. Cetuximab increased the 50% growth-inhibiting effects of docetaxel in OVCAR-3 and IGROV-1, but not in SKOV-3. Coaddition of pertuzumab to cetuximab plus docetaxel in OVCAR-3 and IGROV-1, and, to a lesser extent trastuzumab in OVCAR-3, inhibited cell growth even further. Caspase-3 activation by docetaxel was enhanced after addition of cetuximab in OVCAR-3 and after addition of cetuximab plus pertuzumab in IGROV-1 and SKOV-3. Functional EGFR-signaling, HER2-signaling, and HER3-signaling routes as shown from abrogation of EGF-stimulated and heregulin-stimulated phosphorylated ERK1/2 by cetuximab, trastuzumab, and pertuzumab, respectively, were shown in OVCAR-3 and IGROV-1, but hardly in SKOV-3. Pertuzumab was able to abrogate phosphorylated HER2 by EGF and heregulin, except in SKOV-3. In conclusion, a combination of docetaxel with inhibitors of HER family members, such as cetuximab plus pertuzumab, may be considered for a clinical trial in ovarian carcinomas with functional receptors.

Inhibition by lenalidomide of growth factor and hypoxia-induced signaling in endothelial and epithelial tumor cells, and effects within the tumor cell microenvironment

e14620 Background: Lenalidomide, an immunomodulatory and anti-angiogenic agent, has activity in many hematological malignancies. It has direct anti-proliferative activity in hematological cells but there is no evidence of direct activity in solid tumor cells. In solid tumors, lenalidomide is being advanced in combination with other agents to take advantage of its immune-enhancing properties in combination with direct anti-tumor agents. Lenalidomide studies in CLL and MM suggest that it may also attenuate pro-survival signals generated by interaction of stroma with the malignant cell itself. Lysophosphatidic acid (LPA) is a key pro-survival factor present at high levels within the ascites of ovarian cancer patients which confers increased tumor invasiveness and reduced survival. Hypoxia-induced factor (HIF)-1α is the key initiator of angiogenesis and tumor invasiveness. Methods: The effect of lenalidomide on growth factor-induced Akt phosphorylation was investigated in endothelial cells, NHL cells, and ovarian cancer cells in vitro. Ovarian cancer cell lines SKOV-3 and OVCAR-3 were treated with LPA and the effect of lenalidomide on invasiveness via enhanced p-Akt was investigated. The effect of lenalidomide on HIF-1α expression by endothelial cells and epithelial cells was also investigated. Results: Lenalidomide inhibited growth factor-induced Akt phosphorylation. Treatment of ovarian tumor cells with LPA increased tumor cell invasiveness via enhanced p-Akt. Lenalidomide strongly inhibited invasion and p-Akt (at S308 but not T473) in a dose-dependent manner. Hypoxic endothelial cells and epithelial tumor cells showed enhanced HIF-1α expression. Lenalidomide inhibited hypoxia-induced HIF-1α expression by endothelial cells and by epithelial tumor cells, including prostate, breast, pancreatic, renal and ovarian tumor cells. Conclusions: Lenalidomide may act within the tumor microenvironment to inhibit key signals of tumor cells survival, growth, and invasiveness. These studies support the potential utility of lenalidomide in combination with other agents in the treatment of patients with solid tumors. [Table: see text]

Cell proliferation of human ovarian cancer is regulated by the opioid growth factor-opioid growth factor receptor axis

Ovarian cancer is the leading cause of death from gynecological malignancies. Understanding the biology of these tumors, as well as treatment modalities, has been challenging. The opioid growth factor (OGF; [Met(5)]-enkephalin) and the OGF receptor (OGFr) form an endogenous growth-regulating pathway in homeostasis and neoplasia. In this investigation, we examined the relationship of the OGF-OGFr axis to ovarian cancer, and defined its presence, function, and mechanisms. Using OVCAR-3 and SKOV-3 ovarian cancer cell lines, we found that OGF and OGFr were present and functional. Exogenous OGF was observed to have a dose-dependent, serum-independent, reversible, and receptor-mediated inhibitory action on cell proliferation that was dependent on RNA and protein synthesis. The repressive effect of OGF on cell proliferation also was observed in SW626, CAOV-3, and HEY ovarian cancer cell lines. Endogenous OGF was found to be constitutively produced and tonically active on cell replicative activities, with neutralization of this peptide accelerating cell proliferation. Silencing of OGFr using siRNA technology stimulated cell replication, documenting its integral role. The mechanism of OGF-OGFr action on DNA synthesis was related to the cyclin-dependent kinase inhibitory pathway because knockdown of p16 or p21 in OVCAR-3 cells, and p21 in SKOV-3 cells, eliminated OGF's inhibitory effect on growth. These data are the first to report that the OGF-OGFr system is a native biological regulator of cell proliferation in human ovarian cancer. This information will be important in designing treatment strategies for this deadly disease.

Identification of Cancer Stem-like Side Population Cells in Ovarian Cancer Cell Line OVCAR-3

ABSTRACTSide population (SP) cells may enrich stem-like cells in many normal and malignant tissues. However, SP method application has drawn special attention to the field of stem cell research, and the existence of SP cells in cell culture is being debated, most probably because different cell lines require different technical modifications, especially when cell staining is considered. In this study, the authors aimed to disclose whether the hoechst33342 staining required extensive optimization for identifying SP cells in the human ovarian cancer cell line OVCAR-3. After systematic evaluations, it was found that only 2.5μg/mL hoechst33342 staining of the cells for 60 min could get an ideal SP population, which accounted for 0.9% of the whole cell population. The sorted SP cells showed significantly higher colony formation efficiency than the non-side population (NSP) cells, and only the SP cells could form holoclones. Real-time PCR disclosed that SP cells expressed higher levels of “stemness” gene Oct3/4 than the NSP cells did, indicating that the SP cells might harbor cancer stem cells in this cell line. The results highlight the necessity of SP method optimization in cell studies, and the SP cells in this cell line merit further studies when cancer stem cell identification and isolation are considered.

Regulator of G-protein signalling expression and function in ovarian cancer cell lines

Regulator of G-protein signalling (RGS)2 proteins critically regulate signalling cascades initiated by G-protein coupled receptors (GPCRs) by accelerating the deactivation of heterotrimeric G-proteins. Lysophosphatidic acid (LPA) is the predominant growth factor that drives the progression of ovarian cancer by activating specific GPCRs and G-proteins expressed in ovarian cancer cells. We have recently reported that RGS proteins endogenously expressed in SKOV-3 ovarian cancer cells dramatically attenuate LPA stimulated cell signalling. The goal of this study was twofold: first, to identify candidate RGS proteins expressed in SKOV-3 cells that may account for the reported negative regulation of G-protein signalling, and second, to determine if these RGS protein transcripts are differentially expressed among commonly utilized ovarian cancer cell lines and non-cancerous ovarian cell lines. Reverse transcriptase-PCR was performed to determine transcript expression of 22 major RGS subtypes in RNA isolated from SKOV-3, OVCAR-3 and Caov-3 ovarian cancer cell lines and non-cancerous immortalized ovarian surface epithelial (IOSE) cells. Fifteen RGS transcripts were detected in SKOV-3 cell lines. To compare the relative expression levels in these cell lines, quantitative real time RT-PCR was performed on select transcripts. RGS19/GAIP was expressed at similar levels in all four cell lines, while RGS2 transcript was detected at levels slightly lower in ovarian cancer cells as compared to IOSE cells. RGS4 and RGS6 transcripts were expressed at dramatically different levels in ovarian cancer cell lines as compared to IOSE cells. RGS4 transcript was detected in IOSE at levels several thousand fold higher than its expression level in ovarian cancer cells lines, while RGS6 transcript was expressed fivefold higher in SKOV-3 cells as compared to IOSE cells, and over a thousand fold higher in OVCAR-3 and Caov-3 cells as compared to IOSE cells. Functional studies of RGS 2, 6, and 19/GAIP were performed by measuring their effects on LPA stimulated production of inositol phosphates. In COS-7 cells expressing individual exogenous LPA receptors, RGS2 and RSG19/GAIP attenuated signalling initiated by LPA1, LPA2, or LPA3, while RGS6 only inhibited signalling initiated by LPA2 receptors. In SKOV-3 ovarian cancer cells, RGS2 but not RGS6 or RGS19/GAIP, inhibited LPA stimulated inositol phosphate production. In contrast, in CAOV-3 cells RGS19/GAIP strongly attenuated LPA signalling. Thus, multiple RGS proteins are expressed at significantly different levels in cells derived from cancerous and normal ovarian cells and at least two candidate RGS transcripts have been identified to account for the reported regulation of LPA signalling pathways in ovarian cancer cells.

A proteomic approach to paclitaxel chemoresistance in ovarian cancer cell lines

Ovarian cancer is the leading cause of gynaecological cancer mortality. Paclitaxel is used in the first line treatment of ovarian cancer, but acquired resistance represents the most important clinical problem and a major obstacle to a successful therapy. Several mechanisms have been implicated in paclitaxel resistance, however this process has not yet been fully explained. To better understand molecular resistance mechanisms, a comparative proteomic approach was undertaken on the human epithelial ovarian cancer cell lines A2780 (paclitaxel sensitive), A2780TC1 and OVCAR3 (acquired and inherently resistant). Proteins associated with chemoresistance process were identified by DIGE coupled with mass spectrometry (MALDI-TOF and LC-MS/MS). Out of the 172 differentially expressed proteins in pairwise comparisons among the three cell lines, 151 were identified and grouped into ten main functional classes. Most of the proteins were related to the category of stress response (24%), metabolism (22%), protein biosynthesis (15%) and cell cycle and apoptosis (11%), suggesting that alterations of those processes might be involved in paclitaxel resistance mechanisms. This is the first direct proteomic comparison of paclitaxel sensitive and resistant ovarian cancer cells and may be useful for further studies of resistance mechanisms and screening of resistance biomarkers for the development of tailored therapeutic strategies.

GnRH analog resensitizes cisplatin-resistant human ovarian cancer cells

Objective:To study the effect of GnRH analog triptorelin in resensitizing cisplatin-resistant human ovarian canc- er cells and to discuss the related mechanism.Methods:Cisplatin-resistant human ovarian cancer cell line OVCAR-3/CDDP was established in vitro.MTT assay was used to assess the inhibitory effects of triptorelin,cisplatin alone or a combination of both on OVCAR-3/CDDP cells.Flow cytometry was employed to observe the expression changes in epidermal growth factor receptor (EGFR)in different groups.Results:The drug restant index of OVCAR-3/CDDP cells was 13.42.The resensitizing fold of cisplatin combined with triptorelin was 3.80.The expression of EGFR had the most prominent decrease in OVCAR-3/CDDP cells in the combination group.Conclusion:Triptorelin can partially resensitize cisplatin-resistant OVCAR-3/CDDP cells,which might be related to the down-regulation of EGFR.

Biological Significance of Erythropoietin and Erythropoietin Receptor Expression by Human Ovarian Cancer Cells.

Erythropoietin (Epo) is the primary regulator of erythroid cell proliferation and differentiation mediated through its specific binding to the Epo receptor (EpoR). Epo also is known to have non-hematopoietic actions, including the promotion of wound healing, tissue protection and others. Accumulating evidence demonstrating both Epo and EpoR expression in many types of human cancers has raised concern about the clinical use of Epo and other erythropoiesis stimulating agents (ESAs) in cancer-related anemia, since the presence of functional EpoR on the tumor cells suggests the potential for an adverse effect of Epo treatment by enhancing cancer growth and progression. Previously, we demonstrated that A2780 ovarian cancer cells express the EpoR gene and that long-term Epo treatment of these cells renders them resistant to paclitaxel. We now report the characterization and biological significance of Epo and EpoR expression by four ovarian cancer cell lines. Using semi-quantitative RT-PCR, restriction digestion of the PCR products and DNA sequence analysis, we demonstrated that A2780, CaOV, SKOV, and OVCAR-3 ovarian cancer cell lines examined express Epo and EpoR at the mRNA level. We demonstrated EpoR protein expression both by western blotting and by immunofluorescence, and demonstrated biologically active Epo protein expression by quantitative in vitro bioassay of the cell culture supernatants. The EpoR on A2780 cells are functional, since Epo stimulation of the cells resulted in a time-dependent 5-fold increase in phosphorylation of Erk1/2 that reached a peak in 10 min and then returned to the basal level. None of the cell lines exhibited a short-term (3-day) growth response in culture to exogenous Epo. However, addition of a neutralizing anti-Epo antibody to the cell culture resulted in partial growth inhibition of A2780 cells that was reversed by addition of excess Epo, consistent with an autocrine/paracrine mechanism of Epo growth enhancement of these cells. We also found that long-term Epo treatment of A2780 cells resulted in the development of a phenotype exhibiting enhanced Epo signaling, evidenced by a 20-fold increase in phosphorylation levels of Erk1/2. This phenotype was sustained even after the removal of Epo, suggesting a mechanism underlying the paclitaxel resistance developed after long-term Epo treatment. Our findings have implications for the clinical use of recombinant human Epo and other ESAs to correct and/or prevent anemia in ovarian and, potentially, other cancer patients. They also suggest that endogenous Epo and the EpoR may serve as novel therapeutic targets in the treatment of cancer patients.

Caspase-dependent and -independent suppression of apoptosis by monoHER in Doxorubicin treated cells

Doxorubicin (DOX) is an antitumour agent for different types of cancer, but the dose-related cardiotoxicity limits its clinical use. To prevent this side effect we have developed the flavonoid monohydroxyethylrutoside (monoHER), a promising protective agent, which did not interfere with the antitumour activity of DOX. To obtain more insight in the mechanism underlying the selective protective effects of monoHER, we investigated whether monoHER (1 mM) affects DOX-induced apoptosis in neonatal rat cardiac myocytes (NeRCaMs), human endothelial cells (HUVECs) and the ovarian cancer cell lines A2780 and OVCAR-3. DOX-induced cell death was effectively reduced by monoHER in heart, endothelial and A2780 cells. OVCAR-3 cells were highly resistant to DOX-induced apoptosis. Experiments with the caspase-inhibitor zVAD-fmk showed that DOX-induced apoptosis was caspase-dependent in HUVECs and A2780 cells, whereas caspase-independent mechanisms seem to be important in NeRCaMs. MonoHER suppressed DOX-dependent activation of the mitochondrial apoptotic pathway in normal and A2780 cells as illustrated by p53 accumulation and activation of caspase-9 and -3 cleavage. Thus, monoHER acts by suppressing the activation of molecular mechanisms that mediate either caspase-dependent or -independent cell death. In light of the current work and our previous studies, the use of clinically achievable concentrations of monoHER has no influence on the antitumour activity of DOX whereas higher concentrations as used in the present study could influence the antitumour activity of DOX.

SPARC Inhibits LPA-Mediated Mesothelial—Ovarian Cancer Cell Crosstalk

The interplay between peritoneal mesothelial cells and ovarian cancer cells is critical for the initiation and peritoneal dissemination of, and ascites formation in, ovarian cancer. The production of lysophosphatidic acid (LPA) by both peritoneal mesothelial cells and ovarian cancer cells has been shown to promote metastatic phenotype in ovarian cancer. Herein, we report that exogenous addition or ectopic overexpression of the matricellular protein SPARC (secreted protein acidic and rich in cysteine) significantly attenuated LPA-induced proliferation, chemotaxis, and invasion in both highly metastatic SKOV3 and less metastatic OVCAR3 ovarian cancer cell lines. SPARC appears to modulate these functions, at least in part, through the regulation of LPA receptor levels and the attenuation of extracellular signal-regulated kinase (ERK) 1/2 and protein kinase B/AKT signaling. Moreover, our results show that SPARC not only significantly inhibited both basal and LPA-induced interleukin (IL) 6 production in both cell lines but also attenuated IL-6-induced mitogenic, chemotactic, and proinvasive effects, in part, through significant suppression of ERK1/2 and, to a lesser extent, of signal transducers and activators of transcription 3 signaling pathways. Our results strongly suggest that SPARC exerts a dual inhibitory effect on LPA-induced mesothelial-ovarian cancer cell crosstalk through the regulation of both LPA-induced IL-6 production and function. Taken together, our findings underscore the use of SPARC as a potential therapeutic candidate in peritoneal ovarian carcinomatosis.

Gonadotropin-Releasing Hormone Promotes Ovarian Cancer Cell Invasiveness through c-Jun NH2-Terminal Kinase–Mediated Activation of Matrix Metalloproteinase (MMP)-2 and MMP-9

Gonadotropin-releasing hormone (GnRH) receptor is present in 80% of ovarian cancer, and numerous studies have provided evidence for a role of GnRH in cell proliferation. In this study, the effect of GnRH on the invasion potential of ovarian cancer cells was investigated. In vitro migration and cell invasion assays with the ovarian cancer cell lines Caov-3 and OVCAR-3 revealed the biphasic nature of GnRH; low concentrations of GnRH agonist (GnRHa) increased the cell motility and invasiveness of these cells, but at increased concentrations, the stimulatory effect was insignificant. Reverse transcription-PCR, Western blot, and gelatin zymography showed that the expression of metastasis-related proteinases, matrix metalloproteinase (MMP)-2 and MMP-9, was up-regulated and activated by GnRHa. Moreover, we observed that GnRHa was able to transactivate the MMP-2 and MMP-9 promoters. The invasive/migratory phenotype activated by GnRHa can be blocked by specific inhibitors or neutralizing antibodies to MMP-2 and MMP-9. Knockdown of the GnRH receptor using small interfering RNA significantly inhibited the GnRH-induced MMP activation, invasion, and migration. In addition, we showed that the c-Jun NH(2)-terminal kinase, but not extracellular signal-regulated kinase 1/2 or p38 mitogen-activated protein kinase, signaling pathway was critical for GnRH-mediated up-regulation of MMP, cell invasion, and motility. These results indicate for the first time an expanded role for GnRH in other aspects of ovarian tumor progression, such as metastasis, via activation of MMP and the subsequent increase in cell migration and invasion.

Cytotoxic Macrolides from a New Species of the Deep-Water Marine Sponge Leiodermatium

Chemical investigation of a new species of the deep-water marine sponge Leiodermatium, collected by manned submersible at a depth of 740 feet in Palau, resulted in the isolation of two cytotoxic macrolides, leiodolides A (1) and B (2). The leiodolides represent the first members of a new class of 19-membered ring macrolides, incorporating several unique functional groups including a conjugated oxazole ring, a bromine substituent, and an alpha-hydroxy-alpha-methyl carboxylic acid side-chain terminus. The structures of these new metabolites were established by spectroscopic analysis, chemical modification, and degradation. The relative and absolute stereochemistries at most chiral centers were assigned on detailed interpretation of spectroscopic data, coupled with chemical degradation and application of the modified Mosher ester method. Leiodolide A showed significant cytotoxicity (average GI(50) = 2.0 microM) in the National Cancer Institute's 60 cell line panel with enhanced activity against HL-60 leukemia and OVCAR-3 ovarian cancer cell lines.

Synthesis, antimycobacterial and antitumor activities of new (1,1-dioxido-3-oxo-1,2-benzisothiazol-2(3H)-yl)methyl N,N-disubstituted dithiocarbamate/O-alkyldithiocarbonate derivatives

Reaction of 2-chloromethylsaccharin with substituted potassium dithiocarbamates and substituted potassium dithiocarbonates furnished (1,1-dioxido-3-oxo-1,2-benzisothiazol-2(3H)-yl)methyl N,N-disubstituted dithiocarbamates (4–15) and (1,1-dioxido-3-oxo-1,2-benzisothiazol-2(3H)-yl)methyl O-alkyldithiocarbonates (16–20). The new derivatives were evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv. Compounds 4–13, 15, and 16–20 described herein showed moderate to good inhibitory activity. In particular, seven analogs 4, 5, 6, 13, and 7, 8, and 12 exhibited excellent MIC values of 1.56 and 0.78μg/mL, respectively. Compounds 4, 5, 10, 12, 13, and 16 were selected and screened for antitumor activity. Among the tested compounds, 4 and 5 were found to be cytotoxic, especially against leukemia cell lines CCRF-CEM, HL-60(TB), RPMI-8226, and SR with log10GI50 values lower than −6.69, and against non-small cell lung cancer NCI-H522 cell line with log10GI50 values lower than −6.31. Compound 10 was cytotoxic against leukemia cell line HL-60(TB), whereas 16 displayed favorable cytotoxicity against ovarian cancer cell line OVCAR-3 with log10GI50 values of −6.31 and −7.45, respectively.

Azidothymidine and cisplatin increase p14ARF expression in OVCAR-3 ovarian cancer cell line

p14(ARF) tumor suppressor protein regulates p53 by interfering with mdm2-p53 interaction. p14(ARF) is activated in response to oncogenic stimuli but little is known of the responses of endogenous p14(ARF) to different types of cellular stress or DNA damage. Azidothymidine (AZT) is being tested in several clinical trials as an enhancer of anticancer chemotherapy. However, the knowledge of the relationship between AZT and cellular pathways, e.g. p53 pathway, is very limited. In this study, we show that AZT, cisplatin (CDDP) and docetaxel (DTX) all induce unique molecular responses in OVCAR-3 ovarian carcinoma cells carrying a mutated p53, while in A2780, ovarian carcinoma and MCF-7 breast carcinoma cells with wild type p53, all of these drugs cause similar p53 responses. We found that endogenous p14(ARF) protein in OVCAR-3 cells is down-regulated by DTX but induced by AZT and a short CDDP pulse treatment. In HT-29 colon carcinoma cells with a mutated p53, all treatments down-regulated p14(ARF) protein. Both CDDP and AZT increased the expression of p14ARF mRNA in OVCAR-3 cells. Differences in cell death induced by these drugs did not explain the differences in protein and mRNA expressions. No increase in the level of either c-Myc or H-ras oncoproteins was seen in OVCAR-3 cells after AZT or CDDP-treatment. These results suggest that p14(ARF) can respond to DNA damage without oncogene activation in cell lines without functional p53.

EGF-stimulated migration in ovarian cancer cells is associated with decreased internalization, increased surface expression, and increased shedding of the urokinase plasminogen activator receptor

Objectives.The EGFR is expressed in malignant ovarian tumor tissue, and tissue content of EGFR has been directly associated with poor prognosis in patients with ovarian cancer. The uPA system plays a role in pericellular proteolysis, cell migration, invasion, and is over-expressed in ovarian cancer. This study explored the effects of EGF on uPAR expression in the ovarian cancer cell line OVCAR-3. Methods.We used OVCAR-3 cells and the following methods: cell migration assay, time-lapse video microscopy, real-time PCR, assays for cellular binding of 125I-uPA and cellular degradation of 125I-uPA:PAI-1 complex, biosynthetic labeling using 35S-methionin, Western blot, Northern blot, and ELISAs for uPA, PAI-1, and uPAR. Results.EGF up-regulates both protein and mRNA not only for uPAR, but also for the ligand uPA and its inhibitor PAI-1. Cell surface uPAR, in control as well as EGF-stimulated cells, is present only in the intact, not the cleaved, form. Ligand binding experiments showed an increase of endogenously occupied uPAR, whereas non-occupied receptor sites were not increased. In addition, EGF treatment resulted in decreased degradation of radiolabeled uPA:PAI-1 complex. This suggests decreased internalization of uPAR, since the complex is internalized together with uPAR. Like EGF, colchicine, which inhibits endocytosis, increased cell surface expression of uPAR. In addition, we found an immediate increase of uPAR after exposing the cells to EGF and this was accompanied by a transient increase of cell migration. The increase of cell surface uPAR in response to EGF is accompanied by increased release of the soluble form of uPAR (suPAR) to the medium as well as by increased cell migration. Both uPAR and suPAR increased in cells treated with the endocytosis inhibitor colchicine even though cell migration was inhibited, suggesting that the mechanism of uPAR shedding is not related to cell migration. Conclusion.Increased cell surface uPAR in response to EGF stimulation results from mobilization of uPAR from detergent-resistant domains, increased expression of uPAR mRNA, and decreased internalization and degradation of uPAR. Both the anti-uPAR antibody R3, which inhibits binding of uPA, and the EGFR phosphorylation inhibitor Iressa inhibited cell migration in response to uPA as well as to EGF, suggesting that EGFR and uPAR are engaged in the same multiprotein assembly on the cell surface.