Selection of human ovarian carcinoma cells with high dissemination potential by repeated passage of the cells in vivo into nude mice, and involvement of Le(x)-determinant in the dissemination potential

In vivo selection reveals autophagy promotes adaptation of metastatic ovarian cancer cells to abdominal microenvironment

Peritoneal dissemination is the most frequent metastatic route of ovarian cancer. However, due to the high heterogeneity in ovarian cancer, most conventional studies lack parental tumor controls relevant to metastases and, thus, it is difficult to trace the molecular changes of cancer cells along with the selection by the abdominal microenvironment. Here, we established an in vivo mouse peritoneal dissemination scheme that allowed us to select more aggressive sublines from parental ovarian cancer cells, including A2780 and SKOV-3. Microarray and gene profiling analyses indicated that autophagy-related genes were enriched in selected malignant sublines. Detection of LC3-II, p62 and autophagic puncta demonstrated that these malignant variants were more sensitive to autophagic induction when exposed to diverse stress conditions, such as high cell density, starvation and drug treatment. As compared with parental A2780, the selected variant acquired the ability to grow better under high-density stress; however, this effect was reversed by addition of autophagic inhibitors or knockdown of ATG5. When analyzing the clinical profiles of autophagy-related genes identified to be enriched in malignant A2780 variant, 73% of them had prognostic significance for the survival of ovarian cancer patients. Taken together, our findings indicate that an increase in autophagic potency among ovarian cancer cells is crucial for selection of metastatic colonies in the abdominal microenvironment. In addition, the derived autophagic gene profile can not only predict prognosis well but can also be potentially applied to precision medicine for identifying those ovarian cancer patients suitable for taking anti-autophagy cancer drugs.

Adhesion molecules in peritoneal dissemination: function, prognostic relevance and therapeutic options

Peritoneal dissemination is diagnosed in 10–25 % of colorectal cancer patients. Selected patients are treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy. For these patients, earlier diagnosis, optimised selection criteria and a personalised approach are warranted. Biomarkers could play a crucial role here. However, little is known about possible candidates. Considering tumour cell adhesion as a key step in peritoneal dissemination, we aim to provide an overview of the functional importance of adhesion molecules in peritoneal dissemination and discuss the prognostic, diagnostic and therapeutic options of these candidate biomarkers. A systematic literature search was conducted according to the PRISMA guidelines. In 132 in vitro, ex vivo and in vivo studies published between 1995 and 2013, we identified twelve possibly relevant adhesion molecules in various cancers that disseminate peritoneally. The most studied molecules in tumour cell adhesion are integrin α2β1, CD44 s and MUC16. Furthermore, L1CAM, EpCAM, MUC1, sLe^x and Le^x, chemokine receptors, Betaig-H3 and uPAR might be of clinical importance. ICAM1 was found to be less relevant in tumour cell adhesion in the context of peritoneal metastases. Based on currently available data, sLe^a and MUC16 are the most promising prognostic biomarkers for colorectal peritoneal metastases that may help improve patient selection. Different adhesion molecules appear expressed in haematogenous and transcoelomic spread, indicating two different attachment processes. However, our extensive assessment of available literature reveals that knowledge on metastasis-specific genes and their possible candidates is far from complete.

CRISPR/Cas9n-Mediated Deletion of the Snail 1Gene (SNAI1) Reveals Its Role in Regulating Cell Morphology, Cell-Cell Interactions, and Gene Expression in Ovarian Cancer (RMG-1) Cells

Snail1 is a transcription factor that induces the epithelial to mesenchymal transition (EMT). During EMT, epithelial cells lose their junctions, reorganize their cytoskeletons, and reprogram gene expression. Although Snail1 is a prominent repressor of E-cadherin transcription, its precise roles in each of the phenomena of EMT are not completely understood, particularly in cytoskeletal changes. Previous studies have employed gene knockdown systems to determine the functions of Snail1. However, incomplete protein knockdown is often associated with these systems, which may cause incorrect interpretation of the data. To more precisely evaluate the functions of Snail1, we generated a stable cell line with a targeted ablation of Snail1 (Snail1 KO) by using the CRISPR/Cas9n system. Snail1 KO cells show increased cell–cell adhesion, decreased cell–substrate adhesion and cell migration, changes to their cytoskeletal organization that include few stress fibers and abundant cortical actin, and upregulation of epithelial marker genes such as E-cadherin, occludin, and claudin-1. However, morphological changes were induced by treatment of Snail1 KO cells with TGF-beta. Other transcription factors that induce EMT were also induced by treatment with TGF-beta. The precise deletion of Snail1 by the CRISPR/Cas9n system provides clear evidence that loss of Snail1 causes changes in the actin cytoskeleton, decreases cell–substrate adhesion, and increases cell–cell adhesion. Treatment of RMG1 cells with TGF-beta suggests redundancy among the transcription factors that induce EMT.

Highly parallel genome-wide expression analysis of single mammalian cells

BACKGROUND

We have developed a high-throughput amplification method for generating robust gene expression profiles using single cell or low RNA inputs.

METHODOLOGY/PRINCIPAL FINDINGS

The method uses tagged priming and template-switching, resulting in the incorporation of universal PCR priming sites at both ends of the synthesized cDNA for global PCR amplification. Coupled with a whole-genome gene expression microarray platform, we routinely obtain expression correlation values of R(2)~0.76-0.80 between individual cells and R(2)~0.69 between 50 pg total RNA replicates. Expression profiles generated from single cells or 50 pg total RNA correlate well with that generated with higher input (1 ng total RNA) (R(2)~0.80). Also, the assay is sufficiently sensitive to detect, in a single cell, approximately 63% of the number of genes detected with 1 ng input, with approximately 97% of the genes detected in the single-cell input also detected in the higher input.

CONCLUSIONS/SIGNIFICANCE

In summary, our method facilitates whole-genome gene expression profiling in contexts where starting material is extremely limiting, particularly in areas such as the study of progenitor cells in early development and tumor stem cell biology.

Enhancive effects of Lewis y antigen on CD44-mediated adhesion and spreading of human ovarian cancer cell line RMG-I

Background

This study aimed to investigate the molecular structural relationship between cell adhesive molecule CD44 and Lewis y antigen, and determine the effects of Lewis y antigen on CD44-mediated adhesion and spreading of ovarian cancer cell line RMG-I and the Lewis y antigen-overexpressed cell line RMG-I-H.

Methods

The expression of CD44 in RMG-I and RMG-I-H cells before and after treatment of Lewis y monoclonal antibody was detected by immunocytochemistry; the expression of Lewis y antigen and CD44 was detected by Western Blot. The structural relationship between Lewis y antigen and CD44 was determined by immunoprecipitation and confocal laser scanning microscopy. The adhesion and spreading of RMG-I and RMG-I-H cells on hyaluronic acid (HA) were observed. The expression of CD44 mRNA in RMG-I and RMG-I-H cells was detected by real-time RT-PCR.

Results

Immunocytochemistry revealed that the expression of CD44 was significantly higher in RMG-I-H cells than in RMG-I cells (P < 0.01), and its expression in both cell lines was significantly decreased after treatment of Lewis y monoclonal antibody (both P < 0.01). Western Blot confirmed that the content of CD44 in RMG-I-H cells was 1.46 times of that in RMG-I cells. The co-location of Lewis y antigen and CD44 was confirmed by co-immunoprecipitation. The co-expression of CD44 and Lewis y antigen in RMG-I-H cells was 2.24 times of that in RMG-I cells. The adhesion and spreading of RMG-I-H cells on HA were significantly enhanced as compared to those of RMG-I cells (P < 0.01), and this enhancement was inhibited by Lewis y monoclonal antibody (P < 0.01). The mRNA level of CD44 in both cell lines was similar (P > 0.05).

Conclusion

Lewis y antigen strengthens CD44-mediated adhesion and spreading of ovarian cancer cells.

Alterations in the glycolipid composition and cellular properties of ovarian carcinoma-derived RMG-1 cells on transfection of the alpha1,2-fucosyltransferase gene

Transfection of the mouse Fut1 and Fut2, and human FUT1 genes into human ovarian carcinoma-derived RMG-1 cells resulted in 20-30-fold increases in cellular alpha1,2-fucosyltransferase activity, and in alteration of the glycolipid composition, including not only fucosylated products, but also precursor glycolipids. Although globo-series glycolipids were not significantly affected by the transfection, the major glycolipids belonging to the lacto-series type 1 chain family in RMG-1 cells and the transfectants were the Lc4Cer, Lewis a (Le)a and Leb, and H-1 glycolipids, respectively, suggesting that fucosylation of Lc4Cer to the H-1 glycolipid prevents the further modification of Lc4Cer to Lea and Leb in the transfectants. Also, the lacto-series type 2 chains in RMG-1 cells were LeX, NeuAc-nLc4Cer and NeuAc-LeX, and those in the transfectants were LeX and LeY, indicating that the sialylation of nLc4Cer and LeX is restricted by increased fucosylation of LeX. As a result, the amount of sialic acid released by sialidase from the transfectants decreased to 70% of that from RMG-1 cells, and several membrane-mediated phenomena, such as the cell-to-cell interaction between cancer cells and mesothelial cells, and the cell viability in the presence of an anticancer drug, 5-fluorouracil, for the transfectants was found to be increased in comparison to that for RMG-1 cells. These findings indicate that cell surface carbohydrates are involved in the biological properties, including cell-to-cell adhesion and drug resistance, of cancer cells.

Disruption of the Fanconi anemia-BRCA pathway in cisplatin-sensitive ovarian tumors

Ovarian tumor cells are often genomically unstable and hypersensitive to cisplatin. To understand the molecular basis for this phenotype, we examined the integrity of the Fanconi anemia-BRCA (FANC-BRCA) pathway in those cells. This pathway regulates cisplatin sensitivity and is governed by the coordinate activity of six genes associated with Fanconi anemia (FANCA, FANCC, FANCD2, FANCE, FANCF and FANCG) as well as BRCA1 and BRCA2 (FANCD1). Here we show that the FANC-BRCA pathway is disrupted in a subset of ovarian tumor lines. Mono-ubiquitination of FANCD2, a measure of the function of this pathway, and cisplatin resistance were restored by functional complementation with FANCF, a gene that is upstream in this pathway. FANCF inactivation in ovarian tumors resulted from methylation of its CpG island, and acquired cisplatin resistance correlated with demethylation of FANCF. We propose a model for ovarian tumor progression in which the initial methylation of FANCF is followed by FANCF demethylation and ultimately results in cisplatin resistance.

Invasion of interstitial matrix by a novel cell line from primary peritoneal carcinosarcoma, and by established ovarian carcinoma cell lines: role of cell-matrix adhesion molecules, proteinases, and E-cadherin expression

OBJECTIVE

Primary peritoneal carcinosarcomas are similar to ovarian carcinomas in that they can metastasize by intraperitoneal dissemination; therefore, invasion of the submesothelial interstitial (stromal) matrix is an integral part of the pathology. Our objective was to study cell-matrix interactions that may influence invasive behavior of a novel, primary peritoneal carcinosarcoma cell line (PC880), and to assess how these cell-matrix interactions are different from frequently studied cultured ovarian carcinoma cells NIH:OVCAR-3, SKOV-3, and ES-2. We also wanted to determine how the expression of the cell-cell adhesion molecule E-cadherin is related to invasive behavior.

METHODS

The PC880 cell line was established from ascites fluid of a patient diagnosed with primary peritoneal carcinosarcoma. Adhesion assays were done in titer plates coated with individual matrix components. Cell migration in monolayer cultures was assessed by the scratch wound assay method. Invasion assays were done using a three-dimensional type I collagen gel. Cytokeratin, vimentin, and E-cadherin were detected by Western blotting. E-cadherin mRNA was detected by RT-PCR.

RESULTS

PC880 cells adhered well to fibronectin, laminin, and vitronectin in an integrin-dependent manner. The cells also adhered to type I collagen and invaded a three-dimensional type I collagen matrix. The invasiveness of the PC880 cells was moderated by pretreatment of the collagen matrix with heparin or chondroitin sulfate (82 and 63% of control invasiveness, respectively), indicating a role of cell surface proteoglycans in promoting invasive phenotype. Treatment of PC880 cells with sodium chlorate also decreased invasiveness (80% of control), further confirming the role of cell surface proteoglycans. Treatment of PC880 cells with function-blocking antibody to alpha2 integrin decreased invasiveness (57% of control), indicating the role of integrins in promoting the invasive phenotype. The protease inhibitors GM6001, E-64, and AEBSF decreased invasiveness (35, 57, and 37% of control, respectively) of PC880 cells. The ES-2 cells also adhered to type I collagen, and invaded the three-dimensional type I collagen matrix; however, inhibitors such as heparin, chondroitin sulfate, function-blocking antibody to alpha2 integrin, E-64, and AEBSF were less effective in moderating the invasiveness. Inhibition of invasiveness with sodium chlorate was the same as in PC880 cell, while GM6001 did not inhibit invasiveness at all. The NIH:OVCAR-3 and SK-OV-3 cells were previously found to adhere to type I collagen, but these cells did not invade the three-dimensional type I collagen matrix. In a monolayer culture PC880 and ES-2 cells had significantly higher motility than NIH:OVCAR-3 and SK-OV-3 cells. Only these noninvasive cell lines expressed E-cadherin protein or mRNA.

CONCLUSIONS

PC880 is the first cell line established from primary peritoneal carcinosarcoma, and the cytoskeletal composition indicated that these cells represent the sarcomatous elements of the tumor. PC880 cells, similar to ES-2 cells, adhered to type I collagen, and invaded a three-dimensional collagen matrix. The invasion of the interstitial matrix by both the peritoneal carcinosarcoma and the ovarian carcinoma cell line was mediated by cell surface proteoglycans, alpha2 integrin, and proteases. The invasive cell behavior of PC880 and ES-2 cells correlated with a high degree of motility, and with the lack of expression of the cell-cell adhesion molecule E-cadherin.

HER2 is frequently over-expressed in ovarian clear cell adenocarcinoma: possible novel treatment modality using recombinant monoclonal antibody against HER2, trastuzumab

Ovarian clear cell adenocarcinoma (CCA) is generally chemo-resistant. Recently the poor prognosis and resistance to chemotherapeutic agents of HER2/neu over-expressing tumors have become clear. Thus, we investigated the expression level of HER2 in surgically resected CCA and ovarian serous adenocarcinoma, endometrioid adenocarcinoma, and mucinous adenocarcinoma specimens, as well as CCA cell lines, by an immunohistochemical method. HER2 was over-expressed in 42.9% of CCA (P=0.026, vs. ovarian serous adenocarcinoma), 20.8% of ovarian serous adenocarcinoma, 23.1% of ovarian endometrioid adenocarcinoma, and 30.0% of mucinous adenocarcinoma specimens. Three CCA cell lines, RMG-1, HAC-II and KK were also positively stained for HER2. A flow-cytometric study of HER2 revealed 7.2-, 6.4- and 4.5-fold greater expression of HER2 than that of normal mammary gland, respectively. Trastuzumab, a humanized recombinant monoclonal antibody against HER2 significantly and dose-dependently reduced the growth of CCA cell lines in vitro. The extent of the inhibitory effect of trastuzumab was dependent on the expression level of HER2. Trastuzumab also dose-dependently inhibited the growth of xenografted RMG-1 tumor. The survival period of trastuzumab-treated mice was longer than that of the control group. From these findings, trastuzumab appears to be a candidate as a treatment modality for HER2 over-expressing ovarian CCA.

Ovarian carcinoma cells synthesize both chondroitin sulfate and heparan sulfate cell surface proteoglycans that mediate cell adhesion to interstitial matrix

Metastatic ovarian carcinoma metastasizes by intra-peritoneal, non-hematogenous dissemination. The adhesion of the ovarian carcinoma cells to extracellular matrix components, such as types I and III collagen and cellular fibronectin, is essential for intra-peritoneal dissemination. The purpose of this study was to determine whether cell surface proteoglycans (a class of matrix receptors) are produced by ovarian carcinoma cells, and whether these proteoglycans have a role in the adhesion of ovarian carcinoma cells to types I and III collagen and fibronectin. Proteoglycans were metabolically labeled for biochemical studies. Both phosphatidylinositol-anchored and integral membrane-type cell surface proteoglycans were found to be present on the SK-OV-3 and NIH:OVCAR-3 cell lines. Three proteoglycan populations of differing hydrodynamic size were detected in both SK-OV-3 and NIH:OVCAR-3 cells. Digestions with heparitinase and chondroitinase ABC showed that cell surface proteoglycans of SK-OV-3 cells had higher proportion of chondroitin sulfate proteoglycans (75:25 of chondroitin sulfate:heparan sulfate ratio), while NIH:OVCAR-3 cells had higher proportion of heparan sulfate proteoglycans (10:90 of chondroitin sulfate:heparan sulfate ratio). RT-PCR indicated the synthesis of a unique assortment of syndecans, glypicans, and CD44 by the two cell lines. In adhesion assays performed on matrix-coated titer plates both cell lines adhered to types I and III collagen and cellular fibronectin, and cell adhesion was inhibited by preincubation of the matrix with heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, or chondroitin glycosaminoglycans. Treatment of the cells with heparitinase, chondroitinase ABC, or methylumbelliferyl xyloside also interfered with adhesion confirming the role of both heparan sulfate and chondroitin sulfate cell surface proteoglycans as matrix receptors on ovarian carcinoma cells.

Absence of estrogen receptor-alpha expression in human ovarian clear cell adenocarcinoma compared with ovarian serous, endometrioid, and mucinous adenocarcinoma

The mechanism that regulates growth in ovarian clear cell adenocarcinoma (CCA) is not well understood. A high incidence of concurrent endometriosis with CCA may indicate that estrogen is a growth promotor in CCA. To determine estrogen as a growth promotor, the authors investigated the presence or absence of estrogen receptor-alpha (ER-alpha), ER-beta, progesterone receptor, and dioxin receptor (i.e., aromatic hydrocarbon receptor) in clinically resected ovarian CCA, serous adenocarcinoma (SAC), endometrioid adenocarcinoma (EAC), and mucinous adenocarcinoma (MAC) specimens using an immunohistochemical method. Expression of ER-alpha and ER-beta messenger ribonucleic acid was examined by reverse transcription-polymerase chain reaction in three established CCA cell lines: KK, RMG-1, and HAC-II. None of the surgically resected CCA and CCA cell lines showed positive staining for ER-alpha. Conversely, 97.2% of SACs, 100% of EACs, and 70% of MACs showed positive nuclear staining for ER-alpha (p < 0.001). Conversely, positive ER-beta staining for CCA (39.3%) was similar to that of SAC (41.7%) and MAC (30.0%). EAC (75%) showed a higher expression of ER-beta (p < 0.02). Progesterone receptor was detected in only 10.7% of CCA, compared with SAC and EAC (SAC, 86.1%; EAC, 91.7%; p < 0.01). Aromatic hydrocarbon receptor was detected in all histologic types at an incidence of approximately 50% to 60%. Messenger ribonucleic acid of ER-alpha and ER-beta was not detected in the three CCA cell lines. These findings indicate biologic characteristics that distinguish CCA from other types of ovarian epithelial cancer.