Repurposing ospemifene for potentiating an antigen-specific immune response.

OBJECTIVE: Ospemifene, an estrogen receptor agonist/antagonist approved for the treatment of dyspareunia and vaginal dryness in postmenopausal women, has potential new indications as an immune modulator. The overall objective of the present series of preclinical studies was to evaluate the immunomodulatory activity of ospemifene in combination with a peptide cancer vaccine. METHODS: Immune regulating effects, mechanism of action and structure activity relationships of ospemifene and related compounds were evaluated by examining expression of T-cell activating cytokines in vitro, and antigen-specific immune response and cytotoxic T-lymphocyte activity in vivo. The effects of ospemifene (OSP) on the immune response to a peptide cancer vaccine (PV) were evaluated after chronic [control (n = 22); OSP 50 mg/kg (n = 16); PV (n = 6); OSP+PV (n = 11)], intermittent [control (n = 10); OSP 10 and 50 mg/kg (n = 11); PV (n = 11); combination treatment (n = 11 each dose)] and pretreatment [control; OSP 100 mg/kg; PV 100 µg; combination treatment (n = 8 all groups)] ospemifene oral dosing schedules in a total of 317 mixed-sex tumor-bearing and nontumor-bearing mice. RESULTS: The results showed that ospemifene induced expression of the key TH1 cytokines interferon gamma and interleukin-2 in vitro, which may be mediated by stimulating T-cells through phosphoinositide 3-kinase and calmodulin signaling pathways. In combination with an antigen-specific peptide cancer vaccine, ospemifene increased antigen-specific immune response and increased cytotoxic T-lymphocyte activity in tumor-bearing and nontumor-bearing mice. The pretreatment, intermittent, and chronic dosing schedules of ospemifene activate naive T-cells, modulate antigen-induced tolerance and reduce tumor-associated, pro-inflammatory cytokines, respectively. CONCLUSIONS: Taken together, ospemifene's dose response and schedule-dependent immune modulating activity offers a method of tailoring and augmenting the efficacy of previously failed antigen-specific cancer vaccines for a wide range of malignancies.

Estrogen modulates bone marrow-derived DCs in SLE murine model-(NZB x NZW) F1 female mice.

Dendritic cells (DCs) in the patient and animal models of systemic lupus erythematosus (SLE) are abnormal, but the detailed mechanism is unclear. Estrogen can modulate DCs in biological condition and estrogen concentration is related to the onset and development of SLE. So the control of estrogen on DCs might lead to the disorder of DCs. To prove the hypothesis, we detected the effects of 17beta-estradiol (E2) on bone marrow (BM)-derived DCs in SLE murine model-(NZB x NZW) F1 (NZB/w F1) female mice before and after the disease onset. We found that E2 mainly enhanced the expression of surface molecule CD40, MHCII and the stimulation activity of immature DCs, but weakened the activity of mature DCs. E2 decreased the production of cytokines IL-6, IL-10, IL-12 and TNFalpha of DCs in young mice, but increased them in old mice. Tamoxifen could antagonize the E2 effect. E2 changed the expression of estrogen receptor-alpha (ER alpha) in DCs. The level of ER alpha in DCs of various old mice and the differentiation states varied. The results suggest that E2 can modulate the functions of BM-derived DCs in SLE pathology. The modulation is achieved by binding ER. The effects of E2 on DCs are different depending on the progression of SLE and cell differentiation status. This might be due to the difference of ER expression.

Estradiol regulates monocyte chemotactic protein-1 in human coronary artery smooth muscle cells: a mechanism for its antiatherogenic effect.

OBJECTIVE: The protective effect of estrogen against early atherosclerosis in animal models is well documented, but the mechanisms responsible for this effect are not well understood. The earliest recognizable event in the pathogenesis of atherosclerosis is an increased recruitment of macrophages into the arterial subendothelium. Macrophages first play a protective role by removing low-density lipoproteins, but when the cholesterol is in excess, macrophages are converted into foam cells and form atheromas. Recent human and animal data indicate that the recruitment of macrophages to the arterial wall is mediated by monocyte chemotactic protein-1 (MCP-1). We hypothesized that one of the mechanisms of estrogen's protective effect against atherosclerosis may be the down-regulation of MCP-1 expression in the arterial wall. DESIGN: Human coronary artery smooth muscle cells were replicated to confluence in smooth muscle cell basal medium supplemented with growth factors and 5% fetal bovine serum. Before each experiment, cells were incubated for 24 h with phenol red-free medium containing 5% charcoal-stripped calf serum, and then they were treated with various concentrations of 17beta-estradiol as well as selective estrogen receptor (ER) modulators, raloxifene and tamoxifen. MCP-1 messenger ribonucleic acid (mRNA) levels were quantified by Northern blots. MCP-1 protein was quantified using an enzyme-linked immunosorbent assay. ER expression was evaluated by reverse transcriptase-polymerase chain reaction. RESULTS: Human coronary artery smooth muscle cells expressed MCP-1 mRNA and produced MCP-1 protein. Estradiol induced up to 40% inhibition in mRNA expression at concentrations 10-9 M and higher. Raloxifene and tamoxifen also resulted in an inhibition, but the inhibition was less than when induced by estradiol. Estradiol also inhibited the MCP-1 protein production in a concentration-dependent manner (p < 0.05). Coronary smooth muscle cells expressed both ERalpha and ERbeta. CONCLUSION: Our findings suggest that one of the mechanisms by which estrogen prevents atherosclerosis is by down-regulating MCP-1 expression, thus decreasing macrophage recruitment to the arterial wall.

Site-directed estrogen receptor antibodies stabilize 4-hydroxytamoxifen ligand, but not estradiol, and indicate ligand-specific differences in the recognition of estrogen response element DNA in vitro.

Conformational differences between type I antiestrogen-liganded estrogen receptor and estradiol (E2)-liganded estrogen receptor (ER) are thought to be responsible for differentiating agonist versus antagonist ER activity at individual genes. To examine the impact of ER ligand on estrogen-response element (ERE) binding kinetics and receptor conformation, we quantitated the effect of site-directed, ER-specific antibodies raised against synthetic peptides corresponding to the DNA-binding domain of human ER on ER-ERE binding in vitro. Although 4-hydroxytamoxifen-liganded-ER (4-OHT-ER) and E2-ER bind a consensus ERE with equal high affinity, the stoichiometry of 4-OHT-ER-ERE binding at saturation is approximately 50% lower than that of E2-ER binding to all ERE sequences tested. In contrast, the ERE binding stoichiometry of tamoxifen aziridine-liganded ER (TAz-ER) is identical to that of E2-ER: one receptor dimer bound per ERE. The difference in binding stoichiometry is caused by dissociation of one molecule of 4-OHT from the ER as the dimeric receptor binds DNA. Addition of low concentrations of ER-specific polyclonal antibodies AT3A or AT3B prevented 4-OHT ligand dissociation, yielding an increase in specific 4-OHT-ER-ERE binding to a level equal to that of E2-ER- or TAz-ER-ERE binding. However, higher amounts of AT3A or AT3B inhibited specific ERE binding of both 4-OHT- and E2-ER. We conclude that differences in ER conformation when liganded with 4-OHT versus E2 are revealed by these antibodies and that such differences in receptor conformation may influence subsequent interaction of the receptor with other proteins necessary for transactivation.

Tamoxifen-induced immune-mediated platelet destruction. A case report.

Drug-induced immunologic thrombocytopenia, a fairly common disorder, is characterized by drug-dependent antiplatelet antibodies that destroy circulating platelets in the presence of the provoking drug or its metabolites. The development of reliable methods for the detection of platelet-bound immunoglobulins causing in vivo platelet destruction, such as the use of monoclonal antibodies tagged with fluorescein and flow cytofluorimetric analysis, has ushered in a new era to differentiate between immune and non-immune thrombocytopenias. A severe thrombocytopenia developed in an elderly female patient treated with tamoxifen, a non-steroidal anti-estrogen drug, after surgery for breast cancer. A tamoxifen-dependent platelet antibody was detected in the patient's serum and linked on the platelet membranes. This antibody reacted only in the presence of the offending drug and showed platelet specificity. Withdrawal of drug restored platelet count to normal levels.

Interaction of [3H] estradiol - and [3H] monohydroxytamoxifen-estrogen receptor complexes with a monoclonal antibody.

The aim of this study was to compare and contrast the interaction of estrogen [( 3H]17 beta-estradiol)- or antiestrogen [( 3H]monohydroxytamoxifen)-receptor complexes from human breast tumor cytosols with monoclonal antibodies raised to the human breast tumor estrogen receptor. Breast tumor cytosols containing estrogen receptor which sedimented as radiolabeled peaks in either the 8S, 8S and 4S, or 4S regions of sucrose density gradients, interacted with the monoclonal antibody D547 to produce a broad 9-10S peak, a broad 8S-10S peak, or a more discrete 8S peak, respectively. On high salt (0.4M KC1) sucrose density gradients the 4S ligand-receptor complex plus antibody produced a binding peak at approximately the 8S region of the gradient. These sedimentation studies with the monoclonal antibody D547, and similar studies with the monoclonal antibody D58, could detect no differences in the cytosolic estrogen receptor whether complexed with [3H]estradiol or with [3H]monohydroxytamoxifen. These observations were confirmed by Scatchard equilibrium saturation analysis and sucrose density gradient analysis of cytosols from the MCF-7 human breast cancer cell line. The antibody D547 interacted with 8S ER from these cytosols to produce a broad 8S-10S peak, but the antibody produced no change in the affinity or number of binding sites present in these cytosols. It seems, therefore, that the antigenic determinants recognized by these particular antibodies on the breast tumor cytosolic receptor are not significantly altered by the binding of either an estrogen or an antiestrogen to the receptor.