In vitro growth inhibition of ovarian cancer cells by decorin: synergism of action between decorin and carboplatin.

In vitro studies showed that decorin, a small proteoglycan that is a normal component of the cell matrix involved in tissue scaffolding, effectively inhibited the growth of two ovarian cancer lines, SKOV3 and 2774. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to measure cell growth, IC50s for decorin ranged from 150 to 400 microg/ml for the two cell lines. In contrast, the growth of tumor cells grown on an artificial cell matrix (Matrigel) was unaffected by decorin treatment, perhaps because of the decorin being irreversibly bound by matrix-associated collagen. Decorin-induced inhibition of ovarian tumor cells appeared to be associated with the increased expression of the cyclin-dependent kinase inhibitor p21Waf1/Cip1. Up-regulation of p21 expression was shown by Western blot analysis in decorin-treated ovarian cancer cells. No decorin-induced up-regulation of c-myc was seen, although decorin was reported to activate the epidermal growth factor receptor. Decorin was also shown to synergize with carboplatin to inhibit the growth of ovarian tumor cells. Additional studies are warranted to determine the role of decorin in the treatment of ovarian cancer.

Growth inhibitory effects of sodium phenylacetate (NSC 3039) on ovarian carcinoma cells in vitro.

The aim of this study was to determine the antiproliferative activity of sodium phenylacetate (NaPa) against ovarian carcinoma cell lines. NaPa induced a dose-dependent inhibition (IC50 from 12 mM to >20 mM) of all ovarian carcinoma cell lines, although the sensitivity of individual lines to NaPa varied. Both cisplatin-sensitive and -resistant cell lines responded to NaPa, and growth-inhibitory activity was also detected against cells freshly isolated from malignant ascites of previously treated patients. The growth inhibitory effects that were produced by NaPa were time dependent, showing a maximum effect at 72 h, and were not associated with cytotoxic action. Growth inhibitory effects of NaPa were also reversible. After 48- and 72-h exposures to NaPa, a reduction in the percentage of cells in the S-phase was detected, with a concomitant recruitment of cells in the G0-G1 phase. Treatment with NaPa after different exposure times did not significantly increase the proportion of cells undergoing apoptosis. NaPa also produced a significant reduction in the percentage of cyclin-D1- and p21/ras-positive cells and in the percentage of cells positive for bcl-2, whereas the percentages of bax/p21-positive cells increased. NaPa produced minimal, if any, alterations of expression of HLA class I and transforming growth factor beta1 antigens. In contrast, the percentage of transforming growth factor beta2-positive cells decreased after exposure to NaPa. The combination of NaPa with cisplatin resulted in an additive inhibitory effect. Our results show, for the first time, that NaPa inhibits the growth of ovarian carcinoma cell lines and the cells from malignant ascites of chemotherapy-treated patients with ovarian carcinoma. The growth-inhibitory properties of NaPa suggest that this molecule could represent a prototype of a new class of compounds with possible therapeutic potential in patients with ovarian carcinoma.

Growth inhibitory effects of aromatic fatty acids on ovarian tumor cell lines.

Epithelial ovarian cancer is a major cause of cancer-related mortality in women, making the search for new treatment modalities essential. Sodium phenylacetate (NaPa), a phenylalanine derivative, has been shown to induce cytostasis and differentiation by inhibiting protein isoprenylation. Similar effects have been observed with phenylbutyrate, a phenylacetate congener. We examined in parallel the growth inhibitory activity against human ovarian carcinoma cell lines of phenylacetate, phenylbutyric acid (PB), and certain related compounds, and comparisons were made with lovastatin. On a molar basis, hydroxykynurenine and kynurenine showed the highest activity followed by PB and NaPa. Ovarian carcinoma cell lines were also sensitive to lovastatin in micromolar concentrations. Additive effects were observed when PB was combined with cisplatin or when NaPa or PB were combined with lovastatin. NaPa and PB, but not kynurenine, inhibited incorporation of [3H]mevalonate into ovarian carcinoma cells. An immune modulatory role might also be suggested for PB because it resulted in increased ovarian tumor cell expression of human leukocyte antigen class I and the cluster of differentiation molecule CD58, whereas transforming growth factor-beta2 expression was decreased. Phenylbutyrate, which is the ester form of PB, has shown acceptable pharmacological properties and clinical responses in patients with other malignancies, and might be considered for evaluation in ovarian cancer.

The role of cytokines in both the normal and malignant ovary.

Normal ovarian tissue is rich in cytokines. Cytokines and chemokines are important in the physiology of ovarian function and of ovulation. Cytokines and chemokines may recruit cytokine-producing lymphocytes to the site of a developing follicle, and cytokines appear to play an important role in pre and post follicle development. Most of the same cytokines that are found in normal ovarian tissue are also found in association with malignancy in contrast to their functions in normal tissues. It is reasonable to assume that the functions of cytokines associated with malignancy may serve to promote the unregulated growth if tumor cells and metastasis. It is also likely that cytokines produced by tumors will modulate immune responses that favor tumor progression. In the following review, we have highlighted those functions of cytokines that have been identified as having the most significant impact on tumor growth and development. By examining activities of these cytokines in normal and in malignant ovarian tissues, it is hoped that future possible avenues for investigation may be opened up and that the results of these investigations will lead to strategies that can modulate the production or the activity of the cytokines leading to the growth of tumors or their metastases. Such strategies now fall under the general discipline of bioimmunotherapy. This is an expanding discipline as more is learned about growth regulation in cancer, and with the availability and rapid development of new molecules for therapeutic approaches.

The role of macrophages in antitumor defense of patients with ovarian cancer.

Macrophages have diverse effects on tumor biology, including neovascularization, growth rate, and stroma formation. Tumor-associated macrophages (TAMs) represent a major subpopulation of the mononuclear leukocytes present in malignant ascites of ovarian cancer patients. TAMs appear to participate in the immunologic antitumor defense mechanism through cytotoxic activities, such as direct cellular cytotoxicity and the release of cytokines, and may represent key targets for a variety of therapeutic interventions.

Identification of an IL-10-producing HLA-DR-negative monocyte subset in the malignant ascites of patients with ovarian carcinoma that inhibits cytokine protein expression and proliferation of autologous T cells.

A newly described subset of monocytes has been identified in peritoneal exudate cells (PEC) from the malignant ascites from patients with ovarian cancer. These cells were characterized by the production of IL-10 and TGF-beta2, but not IL-12, IL-1alpha, or TNF-alpha, and they expressed CD14, CD16, and CD54, but not HLA-DR, CD80, CD86, CD11a, CD11b, or CD25 cell surface Ags. Since this subset of monocytes could affect the modulation of tumor immune responses in vivo, studies were undertaken to determine their effect on the activation and proliferation of autologous T cells from the peritoneal cavity of patients with ovarian carcinoma. Expression of cytokine-specific transcripts in T cells was determined by RT-PCR. Transcripts for the following cytokines were detected in patient specimens that also contained the IL-10-producing monocytes IL-2 (12 of 17 specimens), GM-CSF (9 of 17 specimens), IFN-gamma (6 of 17 specimens), and TNF-alpha (4 of 17 specimens). Cytokine production by T cells was determined by intracellular flow cytometry and by ELISA. IL-2 and IFN-gamma proteins, unlike their transcripts, were detected only in specimens that lacked IL-10-producing monocytes. IL-10-producing monocytes cocultured with autologous T cells inhibited the proliferation of the T cells in response to PHA. However, T cells cocultured with PEC from which the IL-10-producing monocytes had been removed did not inhibit T cell proliferation. Moreover, the inhibition of T cell proliferation by IL-10-producing monocytes could be reversed by adding neutralizing Abs to both IL-10R and TGF-beta2. These results suggest that this subset of monocytes may modulate immune responses by inhibiting T cell proliferation and cytokine protein production.