Differentiation and growth potential of human ovarian surface epithelial cells expressing temperature-sensitive SV40 T antigen

Tumor necrosis factor-α and interferon-γ stimulate MUC16 (CA125) expression in breast, endometrial and ovarian cancers through NFκB

Transmembrane mucins (TMs) are restricted to the apical surface of normal epithelia. In cancer, TMs not only are over-expressed, but also lose polarized distribution. MUC16/CA125 is a high molecular weight TM carrying the CA125 epitope, a well-known molecular marker for human cancers. MUC16 mRNA and protein expression was mildly stimulated by low concentrations of TNFα (2.5 ng/ml) or IFNγ (20 IU/ml) when used alone; however, combined treatment with both cytokines resulted in a moderate (3-fold or less) to large (> 10-fold) stimulation of MUC16 mRNA and protein expression in a variety of cancer cell types indicating that this may be a general response. Human cancer tissue microarray analysis indicated that MUC16 expression directly correlates with TNFα and IFNγ staining intensities in certain cancers. We show that NFκB is an important mediator of cytokine stimulation of MUC16 since siRNA-mediated knockdown of NFκB/p65 greatly reduced cytokine responsiveness. Finally, we demonstrate that the 250 bp proximal promoter region of MUC16 contains an NFκB binding site that accounts for a large portion of the TNFα response. Developing methods to manipulate MUC16 expression could provide new approaches to treating cancers whose growth or metastasis is characterized by elevated levels of TMs, including MUC16.

Targeting of follicle stimulating hormone peptide-conjugated dendrimers to ovarian cancer cells

Ovarian cancer is the most lethal gynecological malignancy. Current treatment modalities include a combination of surgery and chemotherapy, which often lead to loss of fertility in premenopausal women and a myriad of systemic side effects. To address these issues, we have designed poly(amidoamine) (PAMAM) dendrimers to selectively target the follicle stimulating hormone receptor (FSHR), which is overexpressed by tumorigenic ovarian cancer cells but not by immature primordial follicles and other non-tumorigenic cells. Fluorescein-labeled generation 5 (G5) PAMAM dendrimers were conjugated with the binding peptide domain of FSH (FSH33) that has a high affinity to FSHR. The targeted dendrimers exhibited high receptor selectivity to FSHR-expressing OVCAR-3 cells, resulting in significant uptake and downregulation of an anti-apoptotic protein survivin, while showing minimal interactions with SKOV-3 cells that do not express FSHR. The selectivity of the FSH33-targeted dendrimers was further validated in 3D organ cultures of normal mouse ovaries. Immunostaining of the conjugates revealed their selective binding and uptake by ovarian surface epithelium (OSE) cells that express FSHR, while sparing the immature primordial follicles. In addition, an in vivo study monitoring tissue accumulation following a single intraperitoneal (i.p.) injection of the conjugates showed significantly higher accumulation of FSH33-targeted dendrimers in the ovary and oviduct compared to the non-targeted conjugates. These proof-of-concept findings highlight the potential of these FSH33-targeted dendrimers to serve as a delivery platform for anti-ovarian cancer drugs, while reducing their systemic side effects by preventing nonspecific uptake by the primordial follicles.

In vitro model of spontaneous mouse OSE transformation

An in vitro syngeneic model of neoplastic progression of murine ovarian surface epithelial (MOSE) cells represents a valid and significant model that allows for investigations into early mechanisms that impact tumorigenesis. Importantly, MOSE cells representing different stages of neoplastic transformation can be implanted back into immunocompetent mice to investigate host microenvironmental interactions that impact peritoneal dissemination and suppress immune surveillance mechanisms. Here we describe the isolation of MOSE cells that undergo spontaneous transformation upon repeated passage in cell culture. We also provide detailed in vitro assays for 3-D culturing of MOSE cells for characterizing anchorage-independent and invasive growth properties of these cells. Cell lines derived from this model have provided numerous insights into genetic, epigenetic, and biomechanical changes associated with neoplastic progression, as well as the immune responses associated with peritoneal dissemination of ovarian cancer cells.

37-kDa laminin receptor precursor mediates GnRH-II-induced MMP-2 expression and invasiveness in ovarian cancer cells

GnRH-II enhances ovarian cancer cell invasion in an autocrine manner. We have now found that GnRH-II increases 37-kDa laminin receptor precursor (LRP) production in GnRH receptor (GnRHR)-positive OVCAR-3 and CaOV-3 ovarian cancer cells, while small interfering RNA (siRNA)-mediated depletion of GnRH-II or GnRHR mRNA abrogates this. The invasiveness of ovarian cancer cells is also reduced >85% by siRNA-mediated knockdown of LRP levels and >50% by pretreatment of Matrigel with a synthetic peptide that blocks interactions between laminin and the 67-kDa nonintegrin laminin receptor which comprises two LRP subunits. Conversely, overexpressing LRP in CaOV-3 cells increases their invasiveness 5-fold, while overexpressing LRP with a nonfunctional laminin-binding site does not. Depletion of LRP by siRNA treatment reduces CaOV-3 cell attachment to laminin-coated plates by ∼80% but only reduces their binding to Matrigel by ∼20%. Thus, while LRP influences CaOV-3 cell adhesion to laminin, LRP must act in other ways to enhance invasion. Matrix metalloproteinases (MMPs) are key mediators of invasion, and LRP siRNA treatment of OVCAR-3 and CaOV-3 cells inhibits MMP-2 but not MMP-9 mRNA levels. Overexpressing LRP in these cells increases MMP-2 production specifically, while a laminin-binding deficient LRP does not. Importantly, LRP siRNA treatment abolishes GnRH-II-induced MMP-2 production, and invasion in OVCAR-3 and CaOV-3 cells, which was also seen after MMP-2 siRNA treatment. These results suggest that GnRH-II-induced LRP expression increases the amount of the 67-kDa nonintegrin laminin receptor, which appears to interact with laminin in the extracellular matrix to promote MMP-2 expression and enhance ovarian cancer cell invasion.

STAMP alters the growth of transformed and ovarian cancer cells

BACKGROUND

Steroid receptors play major roles in the development, differentiation, and homeostasis of normal and malignant tissue. STAMP is a novel coregulator that not only enhances the ability of p160 coactivator family members TIF2 and SRC-1 to increase gene induction by many of the classical steroid receptors but also modulates the potency (or EC50) of agonists and the partial agonist activity of antisteroids. These modulatory activities of STAMP are not limited to gene induction but are also observed for receptor-mediated gene repression. However, a physiological role for STAMP remains unclear.

METHODS

The growth rate of HEK293 cells stably transfected with STAMP plasmid and overexpressing STAMP protein is found to be decreased. We therefore asked whether different STAMP levels might also contribute to the abnormal growth rates of cancer cells. Panels of different stage human cancers were screened for altered levels of STAMP mRNA. Those cancers with the greatest apparent changes in STAMP mRNA were pursued in cultured cancer cell lines.

RESULTS

Higher levels of STAMP are shown to have the physiologically relevant function of reducing the growth of HEK293 cells but, unexpectedly, in a steroid-independent manner. STAMP expression was examined in eight human cancer panels. More extensive studies of ovarian cancers suggested the presence of higher levels of STAMP mRNA. Lowering STAMP mRNA levels with siRNAs alters the proliferation of several ovarian cancer tissue culture lines in a cell line-specific manner. This cell line-specific effect of STAMP is not unique and is also seen for the conventional effects of STAMP on glucocorticoid receptor-regulated gene transactivation.

CONCLUSIONS

This study indicates that a physiological function of STAMP in several settings is to modify cell growth rates in a manner that can be independent of steroid hormones. Studies with eleven tissue culture cell lines of ovarian cancer revealed a cell line-dependent effect of reduced STAMP mRNA on cell growth rates. This cell-line dependency is also seen for STAMP effects on glucocorticoid receptor-mediated transactivation. These preliminary findings suggest that further studies of STAMP in ovarian cancer may yield insight into ovarian cancer proliferation and may be useful in the development of biomarker panels.

The mammalian ovary from genesis to revelation

Two major functions of the mammalian ovary are the production of germ cells (oocytes), which allow continuation of the species, and the generation of bioactive molecules, primarily steroids (mainly estrogens and progestins) and peptide growth factors, which are critical for ovarian function, regulation of the hypothalamic-pituitary-ovarian axis, and development of secondary sex characteristics. The female germline is created during embryogenesis when the precursors of primordial germ cells differentiate from somatic lineages of the embryo and take a unique route to reach the urogenital ridge. This undifferentiated gonad will differentiate along a female pathway, and the newly formed oocytes will proliferate and subsequently enter meiosis. At this point, the oocyte has two alternative fates: die, a common destiny of millions of oocytes, or be fertilized, a fate of at most approximately 100 oocytes, depending on the species. At every step from germline development and ovary formation to oogenesis and ovarian development and differentiation, there are coordinated interactions of hundreds of proteins and small RNAs. These studies have helped reproductive biologists to understand not only the normal functioning of the ovary but also the pathophysiology and genetics of diseases such as infertility and ovarian cancer. Over the last two decades, parallel progress has been made in the assisted reproductive technology clinic including better hormonal preparations, prenatal genetic testing, and optimal oocyte and embryo analysis and cryopreservation. Clearly, we have learned much about the mammalian ovary and manipulating its most important cargo, the oocyte, since the birth of Louise Brown over 30 yr ago.

Implication of the Akt2/survivin pathway as a critical target in paclitaxel treatment in human ovarian cancer cells

PURPOSE

Although multiple mechanisms have been implicated in paclitaxel (PTX)-induced resistance in ovarian cancer, recent evidence has suggested that Akt2 has an important role in the protection of cells from paclitaxel-induced apoptosis. In the present study, we investigated the role of the Akt2/survivin pathway in paclitaxel-induced resistance by a modified method to generate an effective shRNA vector.

METHODS

We applied RNAi-mediated silencing techniques to investigate the mechanism of the Akt2/survivin pathway on PTX-induced resistance in ovarian cancer cells (A2780 and SKOV3). The expression of Akt2 and survivin mRNA and related protein levels were evaluated with semiquantitative real-time RT-PCR and western blot analysis, respectively. Inhibition of cell proliferation was determined by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay, and the induction of apoptosis was examined through flow cytometry (FACS) and Hoechst staining.

RESULTS

Akt2 down-regulation sensitized ovarian cancer cells to paclitaxel-induced apoptosis, and inhibited survivin expression. We further demonstrated that suppressing the inhibition of survivin expression can induce the drug-resistance to paclitaxel. We introduced a modified vector to generate shRNA to induce RNA interference, which contained three U6 promoters to express different shRNAs; it severely reduced Akt2 gene expression and showed good specificity.

CONCLUSION

Our findings will aid in understanding the molecular mechanism of paclitaxel-induced resistance in ovarian cancer and facilitate the development of novel anti-neoplastic strategies.

Molecular pathogenesis and therapeutic targets in epithelial ovarian cancer

Ovarian cancer, the most aggressive gynecologic cancer, is the foremost cause of death from gynecologic malignancies in the developed world. Two primary reasons explain its aggressive behavior: most patients present with advanced disease at diagnosis, and die of recurrences from disease that has become resistant to conventional chemotherapies. In this paper on epithelial ovarian cancer (EOC), we will review molecular alterations associated with the few precursor lesions identified to date, followed by the more commonly recognized processes of de novo carcinogenesis, metastasis, and the development of chemoresistance. We will propose a unifying model of ovarian epithelial tumorigenesis that takes into account various hypotheses. We will also review novel approaches to overcome the major problem of chemoresistance in ovarian cancer. Finally, we will discuss advances and new challenges in the development of mouse model systems to investigate EOC precursor lesions, progression, metastasis, and chemoresistance.

Mechanisms underlying p53 regulation of PIK3CA transcription in ovarian surface epithelium and in ovarian cancer

Inactivation of the transcription factor and tumor suppressor p53, and overexpression or mutational activation of PIK3CA, which encodes the p110alpha catalytic subunit of phosphatidylinositol-3-kinase (PI3K), are two of the most common deleterious genomic changes in cancer, including in ovarian carcinomas. We investigated molecular mechanisms underlying interactions between these two mediators and their possible roles in ovarian tumorigenesis. We identified two alternate PIK3CA promoters and showed direct binding of and transcriptional inhibition by p53 to one of these promoters. Conditional suppression of functional p53 increased p110alpha transcripts, protein levels and PI3K activity in immortalized, non-tumorigenic ovarian surface epithelial (OSE) cells, the precursors of ovarian carcinoma. Conversely, overexpression of p53 by adenoviral infection and activation of p53 by gamma-irradiation both diminished p110alpha protein levels in normal OSE and ovarian cancer cells. The demonstration that p53 binds directly to the PIK3CA promoter and inhibits its activity identifies a novel mechanism whereby these two mediators regulate cellular functions, and whereby inactivation of p53 and subsequent upregulation of PIK3CA might contribute to the pathophysiology of ovarian cancer.

Adeno-associated virus-mediated delivery of a mutant endostatin in combination with carboplatin treatment inhibits orthotopic growth of ovarian cancer and improves long-term survival

A human ovarian cancer cell line, which migrates to mouse ovaries and establishes peritoneal carcinomatosis, was used to evaluate the cooperative effect of an antiangiogenic gene therapy combined with chemotherapy. The ovarian carcinoma cell line MA148 was genetically modified by "Sleeping Beauty" transposon-mediated delivery of DsRed2 fluorescent protein. Stable, high-level expression of DsRed protein enabled in vivo imaging of peritoneal dissemination of ovarian cancer. Both external and internal imaging, along with histopathology, showed migration of i.p. injected human ovarian cancer cell line to mouse ovaries. Using this model, we evaluated the effect of adeno-associated virus (AAV)-mediated expression of a mutant endostatin either alone or in combination with carboplatin treatment. A single i.m. injection of recombinant AAV (rAAV)-mutant human endostatin with P125A substitution (P125A-endostatin) showed sustained expression of mutant endostatin. Antiangiogenic gene therapy inhibited orthotopic growth of ovarian cancer and resulted in 33% long-term tumor-free survival. A single cycle of carboplatin treatment combined with mutant endostatin gene therapy resulted in 60% of the animals remaining tumor free for >200 days, which was significantly better than rAAV-LacZ and/or carboplatin. Combination treatment delayed tumor appearance in 40% of the animals, wherein the residual tumors were smaller in size with limited or no peritoneal metastasis. These studies suggest that AAV-mediated gene therapy of P125A-endostatin in combination with carboplatin is a useful method to inhibit peritoneal dissemination of ovarian carcinoma.

Survivin and Granzyme B-induced apoptosis, a novel anticancer therapy

Survivin is an antiapoptotic protein highly expressed in malignant cells that confers resistance to cytotoxic therapy. Granzyme B is a potent cytotoxic protein that is released from mammalian natural killer cells and CTLs following noxious stimuli, including foreign invaders. Here, we took advantage of the properties of these two functionally divergent molecules to create a molecular agent that specifically activates Granzyme B within tumor cells. We designed Survivin and Granzyme B-induced apoptosis (SAGA), which consists of a fusion of the Survivin gene promoter to the coding sequence of active Granzyme B. In cultured human tumor cells transfected with SAGA DNA, Granzyme B is rapidly expressed and results in significant tumor cell death. In vivo, mice harboring human ovarian tumors had statistically significant clinical responses to SAGA treatment that were magnified following combination therapy with SAGA and paclitaxel. At the completion of a 3-week therapeutic trial, 3 of 15 animals were free of disease in the SAGA-treated group, and an additional eight animals had tumors that were nonpalpable and only detected on surgical resection. In contrast, 15 of 15 animals in the control and paclitaxel-only-treated groups had tumors at end of therapy. Treatment with SAGA with or without paclitaxel also prevented disease dissemination in 19 of 20 animals. These results strongly suggest that SAGA has the potential to be a potent agent for the treatment of primary and recurrent human ovarian carcinoma. Moreover, we predict that SAGA will be useful therapeutically in any human cancer that expresses Survivin.

Pregnancy-associated plasma protein-A (PAPP-A) expression and insulin-like growth factor binding protein-4 protease activity in normal and malignant ovarian surface epithelial cells

Pregnancy-Associated Plasma Protein-A (PAPP-A) proteolyses insulin-like growth factor binding protein-4 (IGFBP-4), thereby regulating local IGF availability. Reduced PAPP-A mRNA expression has been reported in ovarian cancer specimens compared to normal ovarian surface epithelial cells (OSE). To characterize PAPP-A expression and proteolytic activity in OSE, we developed a lifespan-extended human cell model using a temperature-sensitive mutant of the SV40 large T antigen (SV40LT). These OSE(tsT) cells proliferate at 34 degrees C (i.e., when SV40LT-positive), but not at 39 degrees C, a temperature at which the SV40LT is unstable (SV40LT-negative). Proteolysis of radiolabeled IGFBP-4 in conditioned media from OSE(tsT) lines was IGF-dependent and blocked by anti-PAPP-A antisera. Temperature shifts that eliminated stable SV40LT induced a 7-fold increase in PAPP-A mRNA and a 4-fold increase in protein. The converse experiment (shifting to SV40LT-positive conditions) resulted in decreased levels of PAPP-A mRNA but little change in PAPP-A protein. Nevertheless, there was a marked reduction in IGF-BP-4 proteolytic activity in medium of SV40LT-positive OSE-(tsT) cells. This decreased PAPP-A activity coincided with a nearly 20-fold increase in mRNA encoding a physiological inhibitor of PAPP-A, the precursor form of eosinophil Major Basic Protein (proMBP), and 4- to 5-fold increases in proMBP protein. Primary cultures of unmodified OSE expressed high levels of PAPP-A and undetectable proMBP, and therefore produced abundant IGFBP-4 protease activity. Short-term ovarian tumor cell cultures expressed variable levels of PAPP-A and high levels of proMBP, and consequently secreted little or no IGFBP-4 protease activity. The concurrent regulation of PAPP-A and its inhibitor, proMBP, suggests that IGFBP-4 proteolysis and local regulation of IGF availability may be altered in malignant ovarian epithelial cells.

Human bronchial smooth muscle cell lines show a hypertrophic phenotype typical of severe asthma

We developed clonal cell lines of human bronchial smooth muscle origin by retroviral transduction of temperature-sensitive simian virus 40 large tumor (T) antigen. These cells show increased growth potential at 33 degrees C, but on shift to the nonpermissive temperature (39 degrees C), they show diminished or arrested growth. In addition to the expected reduction in the level of large T antigen, cells shifted to 39 degrees C show increased expression of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1), characteristic of cells arrested in G1 of the cell cycle. Shifted cells undergo a process of cell hypertrophy, as demonstrated by increased time of flight and forward scatter, as well as increased expression of the contractile proteins alpha-smooth muscle actin, myosin light chain kinase, and SM22. Changes in contractile protein expression were regulated primarily in a posttranscriptional manner. Phosphatidylinositol 3-kinase activity was increased in shifted cells, and chemical inhibition of phosphatidylinositol 3-kinase attenuated alpha-actin and myosin light-chain kinase expression. We have developed clonal cell lines of human bronchial smooth muscle origin that may be useful for the study of airway smooth muscle biology. Furthermore, we demonstrate that arrest of airway smooth muscle cell cycle traversal can induce cellular hypertrophy, which parallels changes observed in the airways of patients with severe asthma.

Animal models of ovarian cancer

Ovarian cancer is the most lethal of all of the gynecological cancers and can arise from any cell type of the ovary, including germ cells, granulosa or stromal cells. However, the majority of ovarian cancers arise from the surface epithelium, a single layer of cells that covers the surface of the ovary. The lack of a reliable and specific method for the early detection of epithelial ovarian cancer results in diagnosis occurring most commonly at late clinical stages, when treatment is less effective. In part, the deficiency in diagnostic tools is due to the lack of markers for the detection of preneoplastic or early neoplastic changes in the epithelial cells, which reflects our rather poor understanding of this process. Animal models which accurately represent the cellular and molecular changes associated with the initiation and progression of human ovarian cancer have significant potential to facilitate the development of better methods for the early detection and treatment of ovarian cancer. This review describes some of the experimental animal models of ovarian tumorigenesis that have been reported, including those involving specific reproductive factors and environmental toxins. Consideration has also been given to the recent progress in modeling ovarian cancer using genetically engineered mice.