Ovarian Carcinoma-derived Cell Research Articles

Extracellular ATP/P2X7 receptor, a regulatory axis of migration in ovarian carcinoma-derived cells.

ATP is actively maintained at high concentrations in cancerous tissues, where it promotes a malignant phenotype through P2 receptors. In this study, we first evaluated the effect of extracellular ATP depletion with apyrase in SKOV-3, a cell line derived from metastatic ovarian carcinoma. We observed a decrease in cell migration and an increase in transepithelial electrical resistance and cell markers, suggesting a role in maintaining a mesenchymal phenotype. To identify the P2 receptor that mediated the effects of ATP, we compared the transcript levels of some P2 receptors and found that P2RX7 is three-fold higher in SKOV-3 cells than in a healthy cell line, namely HOSE6-3 (from human ovarian surface epithelium). Through bioinformatic analysis, we identified a higher expression of the P2RX7 transcript in metastatic tissues than in primary tumors; thus, P2X7 seems to be a promising effector for the malignant phenotype. Subsequently, we demonstrated the presence and functionality of the P2X7 receptor in SKOV-3 cells and showed through pharmacological approaches that its activity promotes cell migration and contributes to maintaining a mesenchymal phenotype. P2X7 activation using BzATP increased cell migration and abolished E-cadherin expression. On the other hand, a series of P2X7 receptor antagonists (A438079, BBG and OxATP) decreased cell migration. We used a CRISPR-based knock-out system directed to P2RX7. According to the results of our wound-healing assay, SKOV3-P2X7KO cells lacked receptor-mediated calcium mobilization and decreased migration. Altogether, these data let us propose that P2X7 receptor is a regulator for cancer cell migration and thus a potential drug target.

Development of the nonreceptor tyrosine kinase FER-targeting PROTACs as a potential strategy for antagonizing ovarian cancer cell motility and invasiveness

Aberrant overexpression of nonreceptor tyrosine kinase FER (Fps/Fes Related) has been reported in various ovarian carcinoma-derived tumor cells and is a poor prognosis factor for patient survival. It plays an essential role in tumor cell migration and invasion, acting concurrently in both kinase-dependent and -independent manners, which is not easily suppressed by conventional enzymatic inhibitors. Nevertheless, the PROteolysis-TArgeting Chimera (PROTAC) technology offers superior efficacy over traditional activity-based inhibitors by simultaneously targeting enzymatic and scaffold functions. Hence in this study, we report the development of two PROTAC compounds that promote robust FER degradation in a cereblon-dependent manner. Both PROTAC degraders outperform a Food and Drug Administration-approved drug, brigatinib, in ovarian cancer cell motility suppression. Importantly, these PROTAC compounds also degrade multiple oncogenic FER fusion proteins identified in human tumor samples. These results lay an experimental foundation to apply the PROTAC strategy to antagonize cell motility and invasiveness in ovarian and other types of cancers with aberrant expression of FER kinase and highlight PROTACs as a superior strategy for targeting proteins with multiple tumor-promoting functions.

FER-mediated phosphorylation and PIK3R2 recruitment on IRS4 promotes AKT activation and tumorigenesis in ovarian cancer cells.

Tyrosine phosphorylation, orchestrated by tyrosine kinases and phosphatases, modulates a multi-layered signaling network in a time- and space-dependent manner. Dysregulation of this post-translational modification is inevitably associated with pathological diseases. Our previous work has demonstrated that non-receptor tyrosine kinase FER is upregulated in ovarian cancer, knocking down which attenuates metastatic phenotypes. However, due to the limited number of known substrates in the ovarian cancer context, the molecular basis for its pro-proliferation activity remains enigmatic. Here, we employed mass spectrometry and biochemical approaches to identify insulin receptor substrate 4 (IRS4) as a novel substrate of FER. FER engaged its kinase domain to associate with the PH and PTB domains of IRS4. Using a proximity-based tagging system in ovarian carcinoma-derived OVCAR-5 cells, we determined that FER-mediated phosphorylation of Tyr779 enables IRS4 to recruit PIK3R2/p85β, the regulatory subunit of PI3K, and activate the PI3K-AKT pathway. Rescuing IRS4-null ovarian tumor cells with phosphorylation-defective mutant, but not WT IRS4 delayed ovarian tumor cell proliferation both in vitro and in vivo. Overall, we revealed a kinase-substrate mode between FER and IRS4, and the pharmacological inhibition of FER kinase may be beneficial for ovarian cancer patients with PI3K-AKT hyperactivation.

Adenosine Receptor A2B Negatively Regulates Cell Migration in Ovarian Carcinoma Cells.

The purinergic system is fundamental in the tumor microenvironment, since it regulates tumor cell interactions with the immune system, as well as growth and differentiation in autocrine-paracrine responses. Here, we investigated the role of the adenosine A2B receptor (A2BR) in ovarian carcinoma-derived cells’ (OCDC) properties. From public databases, we documented that high A2BR expression is associated with a better prognostic outcome in ovarian cancer patients. In vitro experiments were performed on SKOV-3 cell line to understand how A2BR regulates the carcinoma cell phenotype associated with cell migration. RT-PCR and Western blotting revealed that the ADORA2B transcript (coding for A2BR) and A2BR were expressed in SKOV-3 cells. Stimulation with BAY-606583, an A2BR agonist, induced ERK1/2 phosphorylation, which was abolished by the antagonist PSB-603. Pharmacological activation of A2BR reduced cell migration and actin stress fibers; in agreement, A2BR knockdown increased migration and enhanced actin stress fiber expression. Furthermore, the expression of E-cadherin, an epithelial marker, increased in BAY-606583-treated cells. Finally, cDNA microarrays revealed the pathways mediating the effects of A2BR activation on SKOV-3 cells. Our results showed that A2BR contributed to maintaining an epithelial-like phenotype in OCDC and highlighted this purinergic receptor as a potential biomarker.

Involvement of the MDR1 gene and glycolipids in anticancer drug-resistance of human ovarian carcinoma-derived cells.

We previously reported that anti-paclitaxel-resistant ovarian carcinoma cells characteristically expressed the MDR1 (multidrug resistance 1) gene with enhanced synthesis of glycolipids, i.e., LacCer, Gb3Cer, Leb and GM3, and that anti-cisplatin-resistant cells lost GM3. To further examine the involvement of glycolipids and the MDR1 gene in the anticancer drug-resistance, we determined their expression and the sensitivity to anticancer drugs of several ovarian carcinoma-derived cells, i.e., serous KF28, mucinous HMKOA, endometrioid HNOA and clear cell RMG-1 cells. The MDR1 gene was only detected in RMG-1 cells, in which the amounts of Gb4Cer, Leb and GM3 were higher than in the other cells, which reflected their much higher resistance to paclitaxel and docetaxel compared to the other cells. Among HNOA, HMKOA and KF28 cells, all of which did not express the MDR1 gene, the HNOA and HMKOA cells were relatively more resistant to paclitaxel and docetaxel than KF28 cells, and contained more than sevenfold Gb4Cer and Leb in KF28 cells, indicating that cells containing glycolipids with longer carbohydrate chains, even without expression of the MDR1 gene, have the resistance property as to hydrophobic drugs. On the contrary, RMG-1 cells with the highest amount of GM3 were relatively more sensitive to cisplatin than the other cells, which probably due to a negative charge for binding with cisplatin. Thus, MDR1, and increased amounts of Gb4Cer, Leb and GM3 were suggested to be involved in the anticancer drug-resistance to hydrophobic paclitaxel and docetaxel, and GM3 was to basic cisplatin.

RGS5 decreases the proliferation of human ovarian carcinoma‑derived primary endothelial cells through the MAPK/ERK signaling pathway in hypoxia.

Regulator of G-protein signaling 5 (RGS5), a tissue-specific signal-regulating molecule, plays a key role in the development of the vasculature. It was recently found that RGS5 is abundantly expressed in epithelial ovarian cancer (EOC) compared with the normal ovaries. However, the distribution of RGS5 in EOC and its significance require further investigation. The aim of the present study was to investigate the expression of RGS5 in EOC, as well as its association with cancer differentiation, metastasis and clinicopathological parameters. Immunohistochemistry (IHC), western blotting, RT-PCR, wound-healing, cell proliferation and flow cytometric assays were the methods used in the present study. RGS5 was highly expressed in the cytoplasm of ovarian carcinoma cells and in microvascular structures. The expression of RGS5 in EOC was negatively associated with peritoneal metastasis (P=0.004), but it was not found to be associated with age, tumor size, clinical stage or lymph node metastasis (P>0.05). EOC patients with high RGS5 expression had a prolonged progression-free survival (72.34±8.41 vs. 43.56±5.41 months, P<0.001). High expression of RGS5 was correlated with significantly lower microvascular density (MVD) as indicated by the expression of CD34, whereas the opposite was observed in tissues with low RGS5 expression (P<0.05). Hypoxia increased RGS5 expression in ovarian carcinoma-derived endothelial cells (ODMECs), whereas the proliferative capacity of ODMECs exhibited a significant increase following RNAi-mediated reduction of RGS5 expression. These data indicated that RGS5 plays a key role in angiogenesis in ovarian carcinoma. In addition, RGS5 downregulated the expression of the downstream proteins CDC25A, CDK2 and cyclin E, which are mediated by the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway, causing ODMEC arrest in the G1 phase of the cell cycle under hypoxic conditions. Collectively, our data indicated that RGS5 is crucial for the occurrence and development of ovarian cancer, and that RGS5 and its signaling pathway may serve as anti-angiogenesis targets for the treatment of ovarian cancer.

Spatial regulation of signaling by the coordinated action of the protein tyrosine kinases MET and FER

A critical aspect of understanding the regulation of signal transduction is not only to identify the protein-protein interactions that govern assembly of signaling pathways, but also to understand how those pathways are regulated in time and space. In this report, we have applied both gain-of-function and loss-of-function analyses to assess the role of the non-receptor protein tyrosine kinase FER in activation of the HGF Receptor protein tyrosine kinase MET. Overexpression of FER led to direct phosphorylation of several signaling sites in MET, including Tyr1349, but not the activation loop residues Tyr1234/5; in contrast, suppression of FER by RNAi revealed that phosphorylation of both a C-terminal signaling site (Tyr1349) and the activation loop (Tyr1234/5) were influenced by the function of this kinase. Adaptin β, a component of the adaptor protein complex 2 (AP-2) that links clathrin to receptors in coated vesicles, was recruited to MET following FER-mediated phosphorylation. Furthermore, we provide evidence to support a role of FER in maintaining plasma membrane distribution of MET and thereby delaying protein-tyrosine phosphatase PTP1B-mediated inactivation of the receptor. Simultaneous up-regulation of FER and down-regulation of PTP1B observed in ovarian carcinoma-derived cell lines would be expected to contribute to persistent activation of HGF-MET signaling, suggesting that targeting of both FER and MET may be an effective strategy for therapeutic intervention in ovarian cancer.

HPIP promotes epithelial-mesenchymal transition and cisplatin resistance in ovarian cancer cells through PI3K/AKT pathway activation.

Hematopoietic PBX interacting protein (HPIP), a scaffold protein, is known to regulate the proliferation, migration and invasion in different cancer cell types. The aim of this study was to assess the role of HPIP in ovarian cancer cell migration, invasion and epithelial-mesenchymal transition (EMT), and to unravel the mechanism by which it regulates these processes. HPIP expression was assessed by immunohistochemistry of tissue microarrays containing primary ovarian tumor samples of different grades. OAW42, an ovarian carcinoma-derived cell line exhibiting a high HPIP expression, was used to study the role of HPIP in cell migration, invasion and EMT. HPIP knockdown in these cells was achieved using a small hairpin RNA (shRNA) approach. Cell migration and invasion were assessed using scratch wound and transwell invasion assays, respectively. The extent of EMT was assessed by determining the expression levels of Snail, Vimentin and E-cadherin using Western blotting. The effect of HPIP expression on AKT and MAPK activation was also investigated by Western blotting. Cell viabilities in response to cisplatin treatment were assessed using a MTT assay, whereas apoptosis was assessed by determining caspase-3 and PARP cleavage in ovarian carcinoma-derived SKOV3 cells. We found that HPIP is highly expressed in high-grade primary ovarian tumors. In addition, we found that HPIP promotes the migration, invasion and EMT in OAW42 cells and induces EMT in these cells via activation of the PI3K/AKT pathway. The latter was found to lead to stabilization of the Snail protein and to repression of E-cadherin expression through inactivation of GSK-3β. We also found that HPIP expression confers cisplatin resistance to SKOV3 cells after prolonged exposure and that its subsequent knockdown decreases the viability of these cells and increases caspase-3 activation and PARP proteolysis in these cells following cisplatin treatment. From these results we conclude that HPIP expression is associated with high-grade ovarian tumors and may promote their migration, invasion and EMT, a process that is associated with metastasis. In addition, we conclude that HPIP may serve as a potential therapeutic target for cisplatin resistant ovarian tumors.

IL6-induced metastasis modulators p-STAT3, MMP-2 and MMP-9 are targets of 3,3'-diindolylmethane in ovarian cancer cells.

Ovarian cancer is a highly lethal gynecological malignancy for which the overall prognosis has remained poor over the past few decades. Interleukin (IL6) has been found to be a major contributor to the initiation and progression of ovarian cancer. This cytokine exerts its activity through activation of several signaling pathways, in particular the signal transducer and activator of transcription (STAT3) pathway. Here, we aimed at investigating the capacity of a natural dietary compound found in cruciferous vegetables, i.e., 3,3'-diindolylmethane (DIM), to target the metastatic phenotype of ovarian cancer cells through functional p-STAT3. The human ovarian carcinoma-derived cell lines SKOV3 and A2780 were treated with IL6 and/or DIM and subjected to in vitro proliferation, adhesion, migration and invasion assays to assess the anti-metastatic and anti-IL6 effects of DIM, as well as to assess gene expression alterations before and after shRNA-mediated STAT3 silencing. We found that DIM inhibits IL6-mediated increases in ovarian cancer cell adhesion, migration and invasion. These results were corroborated by shRNA-mediated STAT3 silencing. Through Western blot and ELISA analyses direct evidence was provided for the capacity of DIM to inhibit ovarian cancer cell adhesion, migration and invasion, which was found to be associated with down-regulation of the matrix metalloproteinases MMP-2 and MMP-9. From our data we conclude that DIM exhibits an anti-IL6-like activity by inhibiting p-STAT3 enhanced ovarian cancer cell proliferation and in vitro metastasis-associated events, i.e., adhesion, migration and invasion. Most significantly, MMP-2 and MMP-9, which are known to promote and enhance metastasis, were found to act as targets of DIM. This anti-IL6-like property of DIM may pave the way for the development of novel ovarian cancer preventive and/or therapeutic strategies.

The P2RY2 Receptor Induces Carcinoma Cell Migration and EMT Through Cross-Talk With Epidermal Growth Factor Receptor.

Extracellular nucleotides are signaling elements present in the tumor microenvironment; however, their role in tumor growth is not completely understood. In the present study, we asked whether nucleotides regulate cell migration in ovarian carcinoma-derived cells. We observed that 100 μM UTP induced migration in SKOV-3 cells (1.57 ± 0.08 fold over basal), and RT-PCR showed expression of transcripts for the P2RY2 and P2RY4 receptors. Knockdown of P2RY2 expression in SKOV-3 cells (P2RY2-KD) abolished the UTP-induced migration. The mechanism activated by UTP to induce migration involves transactivation of the epidermal growth factor receptor (EGFR) since we observed that the EGFR kinase inhibitor AG1478 and the PI3K inhibitor Wortmannin inhibit this response (to 0.76 ± 0.23 and 0.46 ± 0.14 relative to the control, respectively). In agreement with these observations, UTP was able to modify the phosphorylation state of the EGFR; likewise, the induction of ERK1/2 phosphorylation promoted by UTP was abolished by a 30-60 min treatment with AG1478. Our data also suggested that the enhanced cell migration involves the epithelium to mesenchymal transition (EMT) process, since a 12 h stimulation of SKOV-3 cells with 100 μM UTP showed an increase in vimentin and SNAIL protein levels (459.8 ± 132.4% over basal for SNAIL). Interestingly, treatment with apyrase (10 U/mL) reduces the migration of control cells and induces a considerable enrichment of E-cadherin in the cell-cell contacts, favoring an epithelial phenotype and strongly suggesting that the nucleotides released by tumor cells and acting through the P2RY2 receptor are potential regulators of invasiveness.

Abstract POSTER-BIOL-1328: Endothelin-1/endothelin a receptor-mediated biased signaling is a new player in modulating human ovarian cancer cell tumorigenesis

Abstract The endothelin-1 (ET-1)/endothelin A receptor (ETAR, a G protein-coupled receptor) axis confers pleiotropic effects on both tumor cells and the tumor microenvironment, modulating chemo-resistance and other tumor-associated processes by activating Gαq- and β-arrestin-mediated pathways. While the precise mechanisms by which these effects occur remain to be elucidated, interference with ETAR signaling has emerged as a promising antitumor strategy in many cancers including ovarian cancer (OC). However, current clinical approaches using ETAR antagonists in the absence of a detailed knowledge of downstream signaling have resulted in multiple adverse side effects and limited therapeutic efficacy. To maximize the safety and efficacy of ETAR-targeted OC therapy, we investigated the role of other G protein subunits such as Gαs in the ETAR-mediated ovarian oncogenic signaling. In HEY (human metastatic OC) cells where the ET-1/ETAR axis is well-characterized, Gαs signaling inhibits ETAR-mediated OC cell migration, wound healing, proliferation and colony formation on soft agar while inducing OC cell apoptosis. Mechanistically, ET-1/ETAR is coupled to Gαs/cAMP signaling in the same ovarian carcinoma-derived cell line. Gαs/cAMP/PKA activation inhibits ETAR-mediated β-arrestin activation of angiogenic/metastatic Calcrl and Icam2 expression. Consistent with our findings, Gαs overexpression is associated with improved survival in OC patients in the analysis of the Cancer Genome Atlas data. In conclusion, our results indicate a novel function for Gαs signaling in ET-1/ETAR-mediated OC oncogenesis and may provide a rationale for a biased signaling mechanism, which selectively activates Gαs-coupled tumor suppressive pathways while blocking Gαq-/β-arrestin-mediated oncogenic pathways, to improve the targeting of the ETAR axis in OC. Citation Format: Jian-peng Teoh, Kyoung-mi Park, Yongchao Wang, Qiuping Hu, Sangmi Kim, Guangyu Wu, Shuang Huang, Nita Maihle, Il-man Kim. Endothelin-1/endothelin a receptor-mediated biased signaling is a new player in modulating human ovarian cancer cell tumorigenesis [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1328.

Endothelin-1/Endothelin A receptor-mediated biased signaling is a new player in modulating human ovarian cancer cell tumorigenesis

The endothelin-1 (ET-1)/endothelin A receptor (ETAR, a G protein-coupled receptor) axis confers pleiotropic effects on both tumor cells and the tumor microenvironment, modulating chemo-resistance and other tumor-associated processes by activating Gαq- and β-arrestin-mediated pathways. While the precise mechanisms by which these effects occur remain to be elucidated, interference with ETAR signaling has emerged as a promising antitumor strategy in many cancers including ovarian cancer (OC). However, current clinical approaches using ETAR antagonists in the absence of a detailed knowledge of downstream signaling have resulted in multiple adverse side effects and limited therapeutic efficacy. To maximize the safety and efficacy of ETAR-targeted OC therapy, we investigated the role of other G protein subunits such as Gαs in the ETAR-mediated ovarian oncogenic signaling. In HEY (human metastatic OC) cells where the ET-1/ETAR axis is well-characterized, Gαs signaling inhibits ETAR-mediated OC cell migration, wound healing, proliferation and colony formation on soft agar while inducing OC cell apoptosis. Mechanistically, ET-1/ETAR is coupled to Gαs/cAMP signaling in the same ovarian carcinoma-derived cell line. Gαs/cAMP/PKA activation inhibits ETAR-mediated β-arrestin activation of angiogenic/metastatic Calcrl and Icam2 expression. Consistent with our findings, Gαs overexpression is associated with improved survival in OC patients in the analysis of the Cancer Genome Atlas data. In conclusion, our results indicate a novel function for Gαs signaling in ET-1/ETAR-mediated OC oncogenesis and may provide a rationale for a biased signaling mechanism, which selectively activates Gαs-coupled tumor suppressive pathways while blocking Gαq-/β-arrestin-mediated oncogenic pathways, to improve the targeting of the ETAR axis in OC.

Endoglin is necessary for angiogenesis in human ovarian carcinoma-derived primary endothelial cells

Endoglin (CD105, END) is upregulated in proliferating endothelial cells, suggesting potential therapeutic properties. However, it is not clear whether endoglin mediates an enhanced proliferative rate or may be upregulated as part of a negative feedback loop. To gain insights into context-dependent and cell type-dependent regulatory effects of endoglin, we studied its role properties in human ovarian carcinoma-derived endothelial cells (ODMECs). We isolated and cultured primary ODMECs from epithelial ovarian carcinoma tissue. ODMECs had higher expression of endoglin and VEGFR-2, and also exhibited enhanced spontaneous formation of vessel-like structures in vitro. Transfection of siRNA targeting endoglin in ODMECs cells resulted in the reduction of the proliferation and tube formation. These results indicate that a subset of ODMECs display abnormal angiogenic properties and this phenotype was blocked by decreasing endoglin levels, suggesting endoglin is essential for stimulating angiogenesis, and targeting it may be an attractive approach to anti-angiogenesis therapy for ovarian carcinoma.

Protein-tyrosine Phosphatase 1B Antagonized Signaling by Insulin-like Growth Factor-1 Receptor and Kinase BRK/PTK6 in Ovarian Cancer Cells*♦

Ovarian cancer, which is the leading cause of death from gynecological malignancies, is a heterogeneous disease known to be associated with disruption of multiple signaling pathways. Nevertheless, little is known regarding the role of protein phosphatases in the signaling events that underlie the disease; such knowledge will be essential to gain a complete understanding of the etiology of the disease and how to treat it. We have demonstrated that protein-tyrosine phosphatase 1B (PTP1B) was underexpressed in a panel of ovarian carcinoma-derived cell lines, compared with immortalized human ovarian surface epithelial cell lines. Stable restoration of PTP1B in those cancer cell lines substantially decreased cell migration and invasion, as well as proliferation and anchorage-independent survival. Mechanistically, the pro-survival IGF-1R signaling pathway was attenuated upon ectopic expression of PTP1B. This was due to dephosphorylation by PTP1B of IGF-1R β-subunit and BRK/PTK6, an SRC-like protein-tyrosine kinase that physically and functionally interacts with the IGF-1R β-subunit. Restoration of PTP1B expression led to enhanced activation of BAD, one of the major pro-death members of the BCL-2 family, which triggered cell death through apoptosis. Conversely, inhibition of PTP1B with a small molecular inhibitor, MSI-1436, increased proliferation and migration of immortalized HOSE cell lines. These data reveal an important role for PTP1B as a negative regulator of BRK and IGF-1Rβ signaling in ovarian cancer cells.

Abstract 2241: Possible involvement of glycolipids in anticancer drug resistance of human ovarian serous carcinoma-derived cells.

Abstract To further characterize the molecular basis on anticancer drug-resistance of human ovarian carcinoma, we compared glycolipid and transporter gene expressions in ovarian serous carcinoma-derived KF28 and 2008 cells with those in their paclitaxel- and cisplatin-resistant cells. Lipid compositions were determined by TLC and TLC-immunostaining and gene expressions of transporter proteins and glycosyltransferases were by RT-PCR. Although the amounts of major lipids, i.e. cholesterol, ceramides and phospholipids, in the resistant cells were same with those in the sensitive cells, Gb3Cer was commonly increased in all resistant cells, irrespective of whether the resistance was to paclitaxel or cisplatin. Also, expressions of the MDR1 gene and gangliosides, GM3 for KF28, and GM1 and GD1a for 2008 cells, were enhanced in paclitaxel-resistant cells, but gangliosides were absent in cisplatin-resistant cells. In accord with the decreased amounts of gangliosides in cisplatin-resistant cells, the gene expression and specific activity of GM3 synthase were greatly decreased in cisplatin-resistant cells. One can suggest that increased amount of Gb3Cer in cisplatin-resistant cells is brought about by the metabolic shifts of LacCer-modifying pathway from GM3- to Gb3Cer-synthases. Furthermore, paclitaxel- and cisplatin-resistant cells were converted to forms more sensitive to the respective anticancer drugs on cultivation with D-PDMP, an inhibitor of GlcCer synthase, and GM3, respectively, prior to the addition of anticancer drugs. Thus, coexpression of the MDR1 gene and glycolipids including gangliosides was thought to be necessary for survival of cells in media containing paclitaxel through regulation of transporter proteins with glycolipids in membrane rafts. Also, the decreased amounts of gangliosides might contribute to the cisplatin resistance, probably by the reduced incorporation of cisplatin. Citation Format: Kyoko Tanaka, Daisuke Aoki, Seiji Isonishi, Mikio Mikami, Kazushige Kiguchi, Masao Iwamori. Possible involvement of glycolipids in anticancer drug resistance of human ovarian serous carcinoma-derived cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2241. doi:10.1158/1538-7445.AM2013-2241

Possible involvement of glycolipids in anticancer drug resistance of human ovarian serous carcinoma-derived cells

Glycolipid and transporter protein gene expression in ovarian serous carcinoma-derived 2008 cells, and their paclitaxel-resistant Px2 and cisplatin-resistant C13 forms was examined to confirm the previous finding, i.e., that it was characteristically altered in anticancer drug-resistant cells established on continuous cultivation of ovarian carcinoma-derived KF28 cells in the different anticancer drug-containing media. Although the concentrations of lipid constituents in 2008 cells were higher than those in KF28 cells, and the glycolipid compositions were different, the following glycolipids and genes were commonly altered in KF28- and 2008-derived resistant cells. Gb(3)Cer was increased in all resistant cells, irrespective of whether the resistance was to paclitaxel or cisplatin, and expression of the MDR1 gene and gangliosides was enhanced in paclitaxel-resistant cells, but gangliosides were absent in cisplatin-resistant cells. In accord with the decreased amounts of gangliosides in cisplatin-resistant cells, the gene expression and specific activity of GM3 synthase were greatly decreased in cisplatin-resistant cells. Furthermore, paclitaxel- and cisplatin-resistant cells were converted to forms more sensitive to the respective anticancer drugs on cultivation with D-PDMP, an inhibitor of GlcCer synthase, and GM3, respectively, prior to the addition of anticancer drugs, indicating the possible involvement of glycolipids in anticancer drug resistance.

The anti-adhesive mucin podocalyxin may help initiate the transperitoneal metastasis of high grade serous ovarian carcinoma

High grade serous ovarian tumors often metastasize transperitoneally, a process that begins when small tumor nodules de-adhere and are released into the fluid of the abdominal cavity where they float freely to reach new sites on the peritoneal wall. Podocalyxin, a small anti-adhesive sialomucin, has been shown to contribute to non-adhesive membrane domain formation in some epithelia and is overexpressed in a variety of cancers. We therefore assessed podocalyxin expression on a previously characterized tissue microarray and found that 87% (169/194) of high grade serous epithelial ovarian carcinomas were positive for podocalyxin. In addition, cell surface localization of podocalyxin was associated with a significant decrease in disease-free survival in these tumors. When podocalyxin was force-expressed in serous ovarian carcinoma-derived OVCAR-3 cells it was targeted to the cell surface and it decreased the adhesion of these cells to mesothelial monolayers, fibronectin and immobilized β1 integrin-binding antibodies. This decrease in adhesion was associated with a modest decrease in cell surface β1 integrin. In monolayer culture, podocalyxin was targeted to the free, apical domains of OVCAR-3 cells and it appeared to decrease β1 integrin levels on the attached basolateral domains of the same cells. Furthermore, in 3-dimensional basement membrane gel culture, the cells formed small, cohesive nodules and podocalyxin localized to membrane domains at the cell-basement membrane interface. Therefore, podocalyxin's ability to facilitate the formation of non-adhesive membrane domains may contribute to the formation of free-floating high grade serous tumor nodules during the initial steps of transperitoneal metastasis.

Lewis Y regulates signaling molecules of the transforming growth factor β pathway in ovarian carcinoma-derived RMG-I cells

LeY (Lewis Y) is a difucosylated oligosaccharide carried by glycoconjugates on the cell surface. Elevation of LeY is frequently observed in epithelial-derived cancers and is correlated to pathological staging and prognosis. To study the role of LeY on cancer cells, a stably LeY-overexpressing cell line, RMG-I-H, was developed previously by transfection of the α1,2-fucosyltransferase gene, a key enzyme that catalyzes the synthesis of LeY, into ovarian carcinoma-derived RMG-I cells. Our studies have shown that LeY is involved in the changes in biological behavior of RMG-I-H cells. However, the mechanism is still largely unknown. In this study, we determined the structural relationship and co-localization between LeY and TβRI/TβRII, respectively, and the potential cellular signaling mechanism was also investigated. We found that both TβRI and TβRII contain the LeY structure, and the level of LeY in TβRI and TβRII in RMG-I-H cells was significantly increased. Overexpression of LeY up-regulates the phosphorylation of ERK, Akt and down-regulates the phosphorylation of Smad2/3. In addition, the phosphorylation intensity was attenuated significantly by LeY monoantibody. These findings suggest that LeY is involved in the changes in biological behavior through TGF-β receptors via Smad, ERK/MAPK and PI3K/Akt signaling pathways. We suggest that LeY may be an important composition of growth factor receptors and could be an attractive candidate for cancer diagnosis and treatment.

Increase in Docetaxel-Resistance of Ovarian Carcinoma-Derived RMG-1 Cells with Enhanced Expression of Lewis Y Antigen

Epithelial carcinomas of the ovary exhibit the highest mortality rate among gynecologic malignancies. Studies found that the metabolism of glycolipids or carbohydrates is associated with acquirement of anticancer drug-resistance by cancer cells. This study was to characterize possible involvement of Lewis Y (LeY) antigen in the drug-resistance of cancer cells. We transfected the α1,2-fucosyltransferase gene into human ovarian carcinoma-derived RMG-1 cells and established RMG-1-hFUT cells with enhanced expression of LeY. We determined the effects of docetaxel on the survival of cells by MTT assaying and observed the apoptosis of cells in the presence of docetaxel by flow cytometric analysis and by transmission electron microscopy. Plasma membranes and intracellular granules in RMG-1-hFUT cells were stained with anti-LeY antibody, the intensity of the staining was higher than that in control cells. The RMG-1-hFUT cells exhibited higher resistance to docetaxel than the control cells with regard to the docetaxel concentration and time course. After treatment with 10 μg/mL docetaxel for 72 h, the control cells, but not RMG-1-hFUT, contained abundant positively stained cell debris due to disintegration of the cytoskeleton. On transmission electron microscopy, although the control cells treated with docetaxel as above showed the following morphology, i.e., absence of villi, cells shrunken in size, pyknosis, agglutinated chromatin and cell buds containing nuclei in the process of apoptosis, the RMG-1-hFUT cells showed only agglutinated chromatin and vacuoles in the cytoplasm. In summary, cells with enhanced expression of LeY were shown to acquire docetaxel-resistance, indicating the possible involvement of glycoconjugates in the drug-resistance.

Inhibition of p53 represses E-cadherin expression by increasing DNA methyltransferase-1 and promoter methylation in serous borderline ovarian tumor cells

The mechanisms underlying the progression of noninvasive serous borderline ovarian tumors (SBOT) to low-grade invasive carcinomas are poorly understood. We recently showed that inhibition of p53 induces SBOT invasion by activating the PI3K/Akt pathway and transcriptionally repressing E-cadherin. In human cancers, aberrant DNA methylation is a common phenomenon, and it is thought to be involved in the progression from noninvasive to invasive ovarian carcinomas. In this study, we tested the hypothesis that inhibition of p53 downregulates E-cadherin by regulating the methylation of its promoter in SBOT cells. Here, we show that DNA methyltransferase-1 (DNMT1), but not DNMT3a or DNMT3b, was increased in SV40 LT-infected SBOT4 cells, SBOT4-LT and the low-grade invasive serous ovarian carcinoma-derived cell line MPSC1. Treatment with 5-Aza-dC, a DNMT1 inhibitor, restored E-cadherin promoter methylation and expression, and inhibited cell invasion in both invasive SBOT4-LT and MPSC1 cells. Moreover, knockdown of endogenous p53 using siRNA in SBOT3.1 cells induced DNMT1 expression and led to an increase in E-cadherin promoter methylation. Additionally, activation of the PI3K/Akt pathway is required for p53 inhibition-induced DNMT1 expression. The increase in DNMT1 was associated with the inhibition of p53-induced downregulation of E-cadherin and cell invasion. Our findings show an important role for p53 in the progression of SBOT to an invasive carcinoma, and suggest that downregulation of E-cadherin by DNMT1-mediated promoter methylation contributes to this process.