Effects of prolonged tamoxifen treatment on receptor expression and apoptosis of ovarian cancer cells

Role of Estrogen Receptor β, G-Protein Coupled Estrogen Receptor and Estrogen-Related Receptors in Endometrial and Ovarian Cancer

Ovarian and endometrial cancers are affected by estrogens and their receptors. It has been long known that in different types of cancers, estrogens activate tumor cell proliferation via estrogen receptor α (ERα). In contrast, the role of ERs discovered later, including ERβ and G-protein-coupled ER (GPER1), in cancer is less well understood, but the current state of knowledge indicates them to have a considerable impact on both cancer development and progression. Moreover, estrogen related receptors (ERRs) have been reported to affect pathobiology of many tumor types. This article provides a summary and update of the current findings on the role of ERβ, GPER1, and ERRs in ovarian and endometrial cancer. For this purpose, original research articles on the role of ERβ, GPER1, and ERRs in ovarian and endometrial cancers listed in the PubMed database have been reviewed.

Tamoxifen inhibits fibroblast proliferation and prevents epidural fibrosis by regulating the AKT pathway in rats

Many factors contribute to epidural fibrosis after lumbar laminectomy, particularly the excessive proliferation of fibroblasts. Many studies have shown that tamoxifen (TAM) inhibits fibroblast proliferation and reduces fibrosis, but the detailed effect and mechanism of TAM on preventing epidural fibrosis are unknown. To investigate the effect of TAM on fibroblast proliferation and epidural fibrosis, fibroblasts were cultured and treated with different concentrations of TAM. Cell Counting Kit-8(CCK-8) detection, cell cycle analysis and western blot analysis were used to detect the roles of TAM in regulating fibroblast proliferation. Lumbar laminectomies were performed in rats, and various concentrations of TAM were administered by gavage. Histological and immunohistochemical analyses were used to evaluate the effects of TAM on preventing epidural fibrosis. CCK-8 detection showed that TAM could inhibit fibroblast viability; western blot analysis showed that TAM could decrease the expression of proliferative proteins p-AKT and cyclinD1 and increase the expression of antiproliferative proteins P21 and P27. Histological analysis showed that TAM could reduce epidural fibrosis. Immunohistochemical analysis showed that the p-ATK expression in epidural scar tissue was decreased after TAM treatment. The present study demonstrated that TAM could inhibit fibroblast proliferation and prevent epidural fibrosis, potentially through the regulation of the AKT pathway.

HE4 expression is associated with hormonal elements and mediated by importin-dependent nuclear translocation

Antiestrogens including tamoxifen and fulvestrant have been evaluated as chemotherapeutics for ovarian cancer, particularly in cases of platinum resistant disease. Human epididymis protein 4 (HE4) is highly overexpressed in women with ovarian cancer and overexpression of HE4 has been found to correlate with platinum resistance. However, the role of HE4 in modulating responses to hormones and hormonal therapy has not been characterized in ovarian cancer. Here we demonstrate that 17β-estradiol, tamoxifen, and fulvestrant induce nuclear and nucleolar translocation of HE4 and that HE4 overexpression induces resistance to antiestrogens. HE4 was found to interact with estrogen receptor-α (ER-α), and HE4 overexpression resulted in ER-α downregulation in vitro and in human ovarian cancers. We identified a novel role for importin-4 in governing the nuclear transport of HE4. Treatment with ivermectin, an importin inhibitor, blocked HE4/importin-4 nuclear accumulation and sensitized HE4-overexpressing ovarian cancer cells to fulvestrant and tamoxifen.

The role of hormonal factors and endocrine therapy in ovarian cancer

The efficacy of the second-line chemotherapy commonly used in both relapsed ovarian cancer patients and those with primary treatment failure remains unsatisfactory. This therapy has a small effect on survival, whereas associated toxicity may diminish the patient's quality of life.

Hormonal factors play a role in ovarian tumorigenesis, and inhibition of the stimulating effects of estrogens may exert a clinical benefit. The role of hormonal therapy as a palliative therapeutic alternative for ovarian cancer remains undetermined. This modality may result in long-term stabilization of disease in individual patients and less frequently in tumor remission.

In this article the role of hormonal factors and recent literature of various forms of hormonal therapy for ovarian cancer are presented.

Long-term treatment with the pure anti-estrogen fulvestrant durably remodels estrogen signaling in BG-1 ovarian cancer cells

Most ovarian cancers are estrogen-positive and hormonal treatments using anti-estrogens or aromatase inhibitors are under investigation for treating the tumors that are resistant to conventional therapies. In this study, the long-term effects of two anti-estrogens, namely 4-hydroxytamoxifen and fulvestrant (or ICI182,780), were investigated in ERα-positive BG1 epithelial ovarian cancer cells. To this aim, cells were grown in the presence of anti-estrogen concentrations that were sufficient to saturate the estrogen receptors, but were neither cytotoxic nor cytostatic as indicated by the absence of inhibition of cell proliferation. In these conditions and despite the lack of cytostatic effect of the drugs, long-term treatment (3 months) with the pure anti-estrogen fulvestrant induced a specific, reproducible and irreversible inhibition of ERα expression. This inhibition was accompanied by loss of estrogen-induced cell proliferation and gene expression as indicated by the analysis of several estrogen-responsive genes. ERα down-regulation was not linked to deregulated expression of transcription factors which drive ERα transcription and did not involve DNA methylation or histone deacetylation. Altogether, these results demonstrate that non-cytotoxic concentrations of pure anti-estrogens affect estrogen signaling and might be relevant for the treatment for ovarian cancers.

Effects of pharmacological concentrations of estrogens on growth of 3AO human ovarian cancer cells

During the past two decades, the knowledge of the molecular mechanism by which estrogens exert various functions in different tissues and organs has evolved rapidly. Recent reports demonstrated that estrogen could decrease the cell growth in several types of cancer cells, including ovarian cancer cells. Though experiments explored the possible mechanism of the inhibitory effect, the exact mechanism is responsible for the effect, which remains unclear. The ovary is the main source of the estrogen, estrogen receptor is expressed in several ovarian cell types, including ovarian surface epithelium, the tissue of origin of approximately 90% of the ovarian cancers. It was of great interest to analyze the effects of 17beta-estradiol (E2) on apoptosis of ovarian cancer cells, and the identification of E2-regulated specific genes involved in epithelial proliferation apoptosis, thus may be a clue for understanding the progression of ovarian cancer and for the design of new target therapies. To elucidate the mechanism involved, effects of pharmacological concentrations of estrogen were studied in human ovarian cancer cell line 3AO cells. Inhibition of cellular growth of 3AO cells was seen with E2 at concentrations higher than 0.1 micromol/L. The estrogen receptor inhibitor ICI 182780 cannot block the inhibitory effect of E2. It was surprising to find that ICI 182780 itself can inhibit the growth of 3AO cells, and had a collaborative effect with E2. The decreased cell growth induced by E2 was shown to be apoptosis as analyzed by flow cytometry. ERbeta was detected in the 3AO ovarian cancer cell line but not ERalpha. The expression of ERbeta was weak, which may partially explain why high but not low dose of E2 needed to induce the apoptosis of 3AO cells. We also observed that membrane impermeable E2, E2-BSA have lost growth inhibitory on 3AO cells, which excluded the membrane effect of E2 as previously reported by many investigators. The p38 kinase inhibitor, SB203580 were partially protected 3AO cells against growth inhibition by E2, while inhibitor of JNK, SP600125 enhanced cell death induced by E2. These results showed that MAPK is implicated in cellular processes involving apoptosis.

The efficacy of tamoxifen in patients with advanced epithelial ovarian cancer

BACKGROUND

Activity of tamoxifen as a salvage therapy in patients with advanced epithelial ovarian cancer was evaluated by a number of studies. In this study, we evaluated efficacy of tamoxifen in our patients with platinum-resistant epithelial ovarian carcinoma.

PATIENTS AND METHODS

A retrospective analysis was conducted of patients who received tamoxifen at a dose 20 mg twice daily for the treatment of advanced epithelial ovarian cancer.

RESULTS

Twenty-nine eligible patients were included to the study. There were 1 (3%) complete response, 2 (7%) partial response, 6 (21%) stable disease, and 20 (69%) progressive disease. All patients were progressed after initiation of tamoxifen. Median progression-free survival was 4 mo (95% CI: 2.98-5.02). Disease progression of 19 (65%) patients were shown within the first 6 mo after initiation of tamoxifen. Progression-free survival was between 6 and 12 mo for 7 (24%) patients and > or =12 mo for 3 (10%) patients. The median survival after initiation of tamoxifen was 15 mo (95% CI: 7.2-22.8). No toxicity attributable to tamoxifen was seen in any of the patients. The only independent prognostic factor that had a significant predictive value for progression- free survival was the response to tamoxifen treatment (p = 0.043, hazard ratio: 0.12, 95% CI: 0.01-0.94).

CONCLUSION

Considering minimal side effects and ability to cause objective responses, there is a place for tamoxifen in treatment of patients with platinum-resistant ovarian cancer. A phase III trial is required to con- firm the value of the drug in patients presenting these clinical settings.