E-cadherin loss is frequently associated with ovarian cancer metastasis. Given that adhesion to the abdominal peritoneum is the first step in ovarian cancer dissemination, we reasoned that down-regulation of E-cadherin would affect expression of cell matrix adhesion receptors. We show here that inhibition of E-cadherin in ovarian cancer cells causes up-regulation of A 5 -integrin protein expression and transcription. When E-cadherin was blocked, RMUG-S ovarian cancer cells were able to attach and invade more efficiently. This greater efficiency could, in turn, be inhibited both in vitro and in vivo with an A 5 B 1 -integrin-blocking antibody. When E-cadherin is silenced, A 5 -integrin is up-regulated through activation of an epidermal growth factor receptor/FAK/Erk1-mitogenactivated protein kinase-dependent signaling pathway and not through the canonical E-cadherin/B-catenin signaling pathway. In SKOV-3ip1 ovarian cancer xenografts, which express high levels of A 5 -integrin, i.p. treatment with an A 5 B 1 -integrin antibody significantly reduced tumor burden, ascites, and number of metastasis and increased survival by an average of 12 days when compared with IgG treatment (P < 0.0005). A 5 -Integrin expression was detected by immunohistochemistry in 107 advanced stage ovarian cancers using a tissue microarray annotated with disease-specific patient follow-up. Ten of 107 tissues (9%) had A 5 -integrin overexpression, and 39% had some level of A 5 -integrin expression. The median survival for patients with high A 5 -integrin levels was 26 months versus 35 months for those with low integrin expression (P < 0.05). Taken together, we have identified A 5 -integrin upregulation as a molecular mechanism by which E-cadherin loss promotes tumor progression, providing an explanation for how E-cadherin loss increases metastasis. Targeting this integrin could be a promising therapy for a subset of ovarian cancer patients.

CD95 (also called Fas and APO-1) is a prototypical death receptor that regulates tissue homeostasis mainly in the immune system through induction of apoptosis 1-3. During cancer progression CD95 is frequently downregulated or cells are rendered apoptosis resistant 4,5 raising the possibility that loss of CD95 is part of a mechanism for tumour evasion. However, complete loss of CD95 is rarely seen in human cancers 4 and many cancer cells express large quantities of CD95 and are highly sensitive to CD95 mediated apoptosis in vitro. Furthermore, cancer patients frequently have elevated levels of the physiological ligand for CD95, CD95L 6. These data raise the intriguing possibility that CD95 could actually promote the growth of tumours through its nonapoptotic activities 7. Here we show that cancer cells in general, regardless of their CD95 apoptosis sensitivity, depend on constitutive activity of CD95, stimulated by cancer-produced CD95L, for optimal growth. Consistently, loss of CD95 in mouse models of ovarian cancer and liver cancer reduces cancer incidence as well as the size of the tumours. The tumorigenic activity of CD95 is mediated by a pathway involving JNK and c-Jun. These results demonstrate that CD95 plays a growth promoting role during tumorigenesis and suggest that efforts to inhibit its activity rather than to enhance its activation should be considered during cancer therapy.

The hepatocyte growth factor receptor c-Met is a receptor tyrosine kinase that plays an important role in tumor growth by activating mitogenic signaling pathways.

The role of the fibronectin receptor, α5β1-integrin, as an adhesion receptor and in angiogenesis, is well established. However, its role in cancer cell invasion and metastasis is less clear. We describe a novel mechanism by which fibronectin regulates ovarian cancer cell signaling and promotes metastasis. Fibronectin binding to α5β1-integrin led to a direct association of α5-integrin with the receptor tyrosine kinase, c-Met, activating it in a hepatocyte growth factor/scatter factor (HGF/SF) independent manner. Subsequently, c-Met associated with Src and activated Src and focal adhesion kinase (FAK). Inhibition of α5β1-integrin decreased the phosphorylation of c-Met, FAK and Src, both in vitro and in vivo. Independent activation of c-Met by its native ligand, HGF/SF, or overexpression of a constitutively active FAK in HeyA8 cells could overcome the effect of α5β1-integrin inhibition on tumor cell invasion, indicating that α5β1-integrin is upstream of c-Met, Src and FAK. Inhibition of α5β1-integrin on cancer cells in two xenograft models of ovarian cancer metastasis resulted in a significant decrease of tumor burden, which was independent of the effect of α5β1-integrin on angiogenesis. These data suggest that fibronectin promotes ovarian cancer invasion and metastasis through an α5β1-integrin/c-Met/FAK/Src dependent signaling pathway, transducing signals through c-Met in a HGF/SF independent manner.

Mechanistic insight from the current study suggests that therapeutic targeting of exosomes may be beneficial in treating ovarian cancer. Mol Cancer Res; 15(1); 78-92. ©2016 AACR.

TRL is associated with resistance to radiotherapy among cervical cancer patients, and MDSC-targeting treatments may have therapeutic potential in these patients.

Purpose: Mammalian target of rapamycin (mTOR) plays a central role in cell proliferation and is regarded as a promising target in cancer therapy, including for ovarian cancer. This study aimed to examine the role of mTOR as a therapeutic target in clear cell carcinoma of the ovary, which is regarded as an aggressive, chemoresistant histologic subtype. Experimental Design: Using tissue microarrays of 98 primary ovarian cancers (52 clear cell carcinomas and 46 serous adenocarcinomas), the expression of phospho-mTOR was assessed by immunohistochemistry. Then, the growth-inhibitory effect of mTOR inhibition by RAD001 (everolimus) was examined using two pairs of cisplatin-sensitive parental (RMG1 and KOC7C) and cisplatin-resistant human clear cell carcinoma cell lines (RMG1-CR and KOC7C-CR) both in vitro and in vivo.Results: Immunohistochemical analysis showed that mTOR was more frequently activated in clear cell carcinomas than in serous adenocarcinomas (86.6% versus 50%). Treatment with RAD001 markedly inhibited the growth of both RMG1 and KOC7C cells both in vitro and in vivo. Increased expression of phospho-mTOR was observed in cisplatin-resistant RMG1-CR and KOC7C-CR cells, compared with the respective parental cells. This increased expression of phospho-mTOR in cisplatin-resistant cells was associated with increased activation of AKT. RMG1-CR and KOC7C-CR cells showed greater sensitivity to RAD001 than did parental RMG1 and KOC7C cells, respectively, in vitro and in vivo. Conclusion: mTOR is frequently activated in clear cell carcinoma and can be a promising therapeutic target in the management of clear cell carcinoma. Moreover, mTOR inhibition by RAD001 may be efficacious as a second-line treatment of recurrent disease in patients previously treated with cisplatin. (Clin Cancer Res 2009;15(17):5404-13) Ovarian carcinoma is the fourth most common cause of cancer death among women in the United States, with >21,000 new cases each year and an estimated 15,520 deaths in 2008 (1). Cytoreductive surgery followed by platinum-based chemotherapy usually combined with paclitaxel is the standard initial treatment and has improved survival in patients with epithelial ovarian cancer (2). However, there still exists many clinical problems in the treatment of epithelial ovarian cancer. One of the most important problems that needs to be resolved is the management of clear cell carcinoma of the ovary, which was first recognized by the WHO as a distinct histologic subtype in 1973 (3). The precise incidence of clear cell carcinoma is unknown, but it is reported to be 3.7% to 12.1% of all histologic subtypes among epithelial ovarian cancer (4).There have been two major clinical problems in the clinical management of clear cell carcinoma. First is its poor sensitivity to first-line platinum-based chemotherapy and the association with a worse prognosis than the more common serous adenocarcinomas. In the setting of front-line chemotherapy, the response rate to conventional platinum-based chemotherapy, platinum agent alo...

Ovarian cancer is the leading cause of death among gynecologic malignancies. Since ovarian cancer develops asymptomatically, it is often diagnosed at an advanced and incurable stage. Despite many years of research, there is still a lack of reliable diagnostic markers and methods for early detection and screening. Recently, it was discovered that cell-free microRNAs (miRNAs) circulate in the body fluids of healthy and diseased patients, suggesting that they may serve as a novel diagnostic marker. This review summarizes the current knowledge regarding the potential clinical relevance of circulating cell-free miRNA for ovarian cancer diagnosis, prognosis, and therapeutics. Despite the high levels of ribonucleases in many types of body fluids, most of the circulating miRNAs are packaged in microvesicles, exosomes, or apoptotic bodies, are binding to RNA-binding protein such as argonaute 2 or lipoprotein complexes, and are thus highly stable. Cell-free miRNA signatures are known to be parallel to those from the originating tumor cells, indicating that circulating miRNA profiles accurately reflect the tumor profiles. Since it is well established that the dysregulation of miRNAs is involved in the tumorigenesis of ovarian cancer, cell-free miRNAs circulating in body fluids such as serum, plasma, whole blood, and urine may reflect not only the existence of ovarian cancer but also tumor histology, stage, and prognoses of the patients. Several groups have successfully demonstrated that serum or plasma miRNAs are able to discriminate patients with ovarian cancer patients from healthy controls, suggesting that the addition of these miRNAs to current testing regimens may improve diagnosis accuracies for ovarian cancer. Furthermore, recent studies have revealed that changes in levels of cell-free circulating miRNAs are associated with the condition of cancer patients. Discrepancies between the results across studies due to the lack of an established endogenous miRNA control to normalize for circulating miRNA levels, as well as differing extraction and quantification methods, are the pitfalls to be resolved before clinical application. There is still a long way, however, before this can be achieved, and further evidence would make it possible to apply circulating cell-free miRNAs not only as biomarkers but also as potential therapeutic targets for ovarian cancer in the future.