A new triphenylethylene compound, Fc-1157a. I. Hormonal effects

Computer-Aided Ligand Discovery for Estrogen Receptor Alpha

Breast cancer (BCa) is one of the most predominantly diagnosed cancers in women. Notably, 70% of BCa diagnoses are Estrogen Receptor α positive (ERα+) making it a critical therapeutic target. With that, the two subtypes of ER, ERα and ERβ, have contrasting effects on BCa cells. While ERα promotes cancerous activities, ERβ isoform exhibits inhibitory effects on the same. ER-directed small molecule drug discovery for BCa has provided the FDA approved drugs tamoxifen, toremifene, raloxifene and fulvestrant that all bind to the estrogen binding site of the receptor. These ER-directed inhibitors are non-selective in nature and may eventually induce resistance in BCa cells as well as increase the risk of endometrial cancer development. Thus, there is an urgent need to develop novel drugs with alternative ERα targeting mechanisms that can overcome the limitations of conventional anti-ERα therapies. Several functional sites on ERα, such as Activation Function-2 (AF2), DNA binding domain (DBD), and F-domain, have been recently considered as potential targets in the context of drug research and discovery. In this review, we summarize methods of computer-aided drug design (CADD) that have been employed to analyze and explore potential targetable sites on ERα, discuss recent advancement of ERα inhibitor development, and highlight the potential opportunities and challenges of future ERα-directed drug discovery.

Calibration of sperm concentration for in vitro fertilization in a mouse reprotoxicity model

Xenobiotics, such as chemicals and pesticides, may result in adverse effects on reproduction in human and animals. Using in-vitro embryo production as a testing system reveals details of fertilization (IVF) and early embryonic development (IVC). The aim of our study was to perform a systematical calibration of sperm concentration in an IVF/IVC system, using an outbred mouse strain, and further determine the sperm concentration that furnishes a sensitive assessment of sperm fertilizing capacity in relation to reprotoxic evaluations. By performing breakpoint analysis, the results revealed a maximum two-cell percentage (51%, 95% CI: 38 to 69%) at 3.6 × 10⁴ sperm/ml (95% CI: 2.1 × 10⁴ to 6.1 × 10⁴). For future application of the IVF/IVC system, a sperm concentration lower than this breakpoint concentration is required to be within the responsive range for determining sperm fertilizing capacity. We conclude that a relatively low sperm concentration (2.5 × 10⁴ sperm/ml) is a precondition in a mouse IVF/IVC system in order to detect potential reprotoxic effects on sperm fertilizing capacity. Our study illustrates that a systematic approach is necessary for validation and appropriate use of such in-vitro system used for reproductive toxicity testing.

Adjuvant endocrine monotherapy for postmenopausal early breast cancer patients with hormone-receptor positive: a systemic review and network meta-analysis

BACKGROUND

In patients with hormone receptor-positive postmenopausal of early stage breast cancer, adjuvant endocrine monotherapies include letrozole, anastrozole, exemestane, toremifene and tamoxifen. But the optimum regimen remains controversial.

METHODS

PubMed, Cochrane Database and ClinicalTrials.gov were systematically reviewed of abstract for randomized-controlled trials (RCTs) to assess the efficacy of tamoxifen, letrozole, exemestane, anastrozle and toremifene for postmenopausal patients with hormone-receptor positive (HR+), who have not received prior therapy for early stage breast cancer. The outcomes were measured by disease-free survival (DFS) and overall survival (OS). We evaluated relative hazard ratios (HRs) for death of different therapies by combination hazard ratios for death of included trials. The SUCRA values were used to evaluate the rankings of efficacy for these monotherapies.

RESULTS

A total of fourteen studies including 19,517 patients in our research were absorbed and estimated. The superiority of efficacy for DFS were 5-year letrozole and 10-year tamoxifen (SUCRA values 0.743/0.657) in all comparisons. A more efficient SUCRA values for OS were 5-year Exemestane, 5-year letrozole and 10-year tamoxifen (0.756/0.677/0.669).

CONCLUSIONS

Clinically important differences exist between commonly prescribed different adjuvant endocrine monotherapy regimens for both efficacy and acceptability in favor of exemestane and letrozole. 10-year tamoxifen for early breast cancer patients is noninferior to 5-year anastrozle, and might be the best choice where aromatase inhibitors (AIs) are not easy to acquire.

Effects of toremifene versus tamoxifen on breast cancer patients: a meta-analysis

Toremifene and tamoxifen are both selective estrogen receptor modulators used in the treatment of breast cancer patients. Therefore, we carried out a meta-analysis to achieve a more precise evaluation of the effects of toremifene versus tamoxifen on breast cancer patients, including the efficacy and safety, and the effects on the uterus, lipids, and bone. Comprehensive literature searches were conducted using the electronic databases and reference lists to include randomized controlled trials (RCTs) that compared toremifene with tamoxifen for breast cancer patients. Two reviewers independently selected studies and abstracted data. Data were analyzed by Review Manager, version 5.0. Twenty-three trials (7242 patients) were included. For early stage breast cancer, toremifene was associated with higher 5-year survival rates (OR 1.25, 95 % CI 1.04, 1.50), more vaginal discharge (OR 1. 32, 95 % CI 1.01, 1.73), a greater decrease in serum triglyceride levels (SMD -1.01, 95 % CI -1.89, -0.14), a smaller decrease in LDL cholesterol levels (SMD 0.45, 95 % CI 0.07, 0.84) and in bone mineral density in Ward's triangle (SMD -0.36, 95 % CI -0.71, -0.01), and a greater increase in HDL cholesterol levels (SMD 0.43, 95 % CI 0.08, 0.77) than tamoxifen. For advanced breast cancer patients, toremifene was associated with more vaginal bleeding (OR 0.45, 95 % CI 0.26, 0.80) and a greater decrease in serum triglyceride levels (SMD -1.15, 95 % CI -1.90, -0.39) than tamoxifen. Available evidence showed that toremifene could be an alternative option to tamoxifen for both early and advanced breast cancer patients. However, the methodological quality of the included studies was low. More rigorous RCTs are needed to confirm the results of this meta-analysis in the future.

Toremifene is an effective and safe alternative to tamoxifen in adjuvant endocrine therapy for breast cancer: results of four randomized trials

Compared to tamoxifen, the efficacy and side effects of toremifene in adjuvant endocrine therapy for breast cancer were not very clear. This meta-analysis was conducted to give a more precise estimation of the efficacy and severe side effects of toremifene given in the adjuvant setting in comparison to tamoxifen. The electronic database PubMed was searched for randomized trials comparing toremifene with tamoxifen as adjuvant therapies. Four randomized trials published in three articles were eligible, including 1,890 pooled cases treated with toremifene and 1,857 cases treated with tamoxifen. Compared to patients in tamoxifen group, patients in toremifene group did not have a significantly different overall survival rate (risk ratio (RR): 1.07, 95% confidence interval (CI): 0.97-1.19, P = 0.994 for heterogeneity) or a disease-free survival (DFS) rate (RR: 1.05, 95% CI: 0.95-1.17, P = 0.431 for heterogeneity) at the end of the follow-up time. The rates of thromboembolic events in toremifene group, including deep vein thrombosis (odds ratio (OR): 0.68, 95% CI: 0.40-1.17, P = 0.926 for heterogeneity), cerebrovascular accident (OR: 0.59, 95% CI: 0.32-1.09, P = 0.438 for heterogeneity), and pulmonary embolism (OR: 0.91, 95% CI: 0.42-2.01, P = 0.618 for heterogeneity), were not significantly different from those in tamoxifen group. The rates of endometrial polyps and endometrial cancer between the two groups were almost the same. This meta-analysis suggested that toremifene was as effective as tamoxifen in the adjuvant setting for both perimenopausal and postmenopausal breast cancer patients with similar severe adverse effects to tamoxifen. Toremifene was a convincing and safe change for tamoxifen in adjuvant endocrine therapy.

Excellent outcomes with adjuvant toremifene or tamoxifen in early stage breast cancer

BACKGROUND

Fareston (toremifene) and tamoxifen, both selective estrogen receptor modulators, are therapeutically equivalent treatments for metastatic breast cancer. We hypothesized that toremifene as compared with tamoxifen given as adjuvant therapy for early stage breast cancer would result in equivalent survival with an improved side effect profile, therefore, providing superior therapeutic efficacy.

METHODS

The North American Fareston versus Tamoxifen Adjuvant trial assigned 1813 perimenopausal or postmenopausal women with hormone receptor (HR)-positive invasive breast cancer to adjuvant treatment with either tamoxifen or toremifene. The primary outcomes evaluated were disease-free survival (DFS) and overall survival (OS).

RESULTS

Median follow-up was 59 months. The baseline characteristics of the 2 treatment groups were well-balanced. On the basis of intent-to-treat, 5-year actuarial DFS was not significantly different between tamoxifen and toremifene (91.2% [standard error of the mean [SE] 1.2%] vs 91.2% [SE 1.1%], respectively). Similarly, 5-year actuarial OS was not significantly different between tamoxifen and toremifene (92.7% [SE 1.1%] vs 93.7% [SE 1.0%], respectively). Controlling for patient age, tumor size, and tumor grade, a Cox multivariate survival analysis found no difference between patients randomized to toremifene versus tamoxifen in terms of OS (OR = 0.951; 95% confidence interval [CI], 0.623-1.451, P = .951) or DFS (OR = 1.037; 95% CI, 0.721-1.491, P = .846). Adverse events were similar in the 2 groups.

CONCLUSIONS

Women treated with adjuvant hormonal therapy enjoyed excellent DFS and OS. No significant differences were found between treatment with either tamoxifen or toremifene. Treatment of HR-positive patients with either tamoxifen or toremifene is appropriate.

Effect of combined therapy with the antiestrogen agent toremifene and local hyperthermia on breast cancer cells implanted in nude mice

PURPOSE

We evaluated the effects of combined treatment with the antiestrogen agent toremifene (TOR) and local hyperthermia (LHT) on the MCF-7 breast cancer cell line.

METHODS

BALB/c mice implanted with MCF-7 cells were divided into six treatment groups: a control group, a TOR30 group (given 30 mg/kg/day), a TOR120 group (given 120 mg/kg/day), an LHT group (43.5 degrees C), a TOR30 + LHT group, and a TOR120 + LHT group. The effects of the treatments on tumor cells, estrogen receptor (ER) expression, and cell cycle kinetics were measured after 21 days. We calculated the apoptotic index and vascular density inside the tumors and evaluated the efficacy of the transmigration of TOR into the tumors.

RESULTS

The antitumor effects were significantly greater in both combined therapy groups than in any of the single therapy groups. Estrogen receptor expression was weaker in the combined therapy groups than in the single therapy groups, and there were more G0/G1-phase cells and fewer S-phase cells in both combined therapy groups than in the single therapy groups. The apoptotic index was increased and the tumor vascular density was decreased in the combined therapy groups.

CONCLUSIONS

We attributed the effects of this combined therapy to the induction of apoptosis, the decrease in vascular density, and the increase and decrease in G0/G1-phase and S-phase cells, respectively, in the tumors.

Toremifene and tamoxifen are equally effective for early-stage breast cancer: first results of International Breast Cancer Study Group Trials 12-93 and 14-93

BACKGROUND

Toremifene is a chlorinated derivative of tamoxifen, developed to improve its risk-benefit profile. The International Breast Cancer Study Group (IBCSG) conducted two complementary randomized trials for peri- and postmenopausal patients with node-positive breast cancer to compare toremifene versus tamoxifen as the endocrine agent and simultaneously investigate a chemotherapy-oriented question. This is the first report of the endocrine comparison after a median follow-up of 5.5 years.

PATIENTS AND METHODS

1035 patients were available for analysis: 75% had estrogen receptor (ER)-positive primary tumors, the median number of involved axillary lymph nodes was three and 81% received prior adjuvant chemotherapy.

RESULTS

Toremifene and tamoxifen yielded similar disease-free (DFS) and overall survival (OS): 5-year DFS rates of 72% and 69%, respectively [risk ratio (RR)=0.95; 95% confidence interval (CI)=0.76-1.18]; 5-year OS rates of 85% and 81%, respectively (RR = 1.03; 95% CI = 0.78-1.36). Similar outcomes were observed in the ER-positive cohort. Toxicities were similar in the two treatment groups with very few women (<1%) experiencing severe thromboembolic or cerebrovascular complications. Quality of life results were also similar. Nine patients developed early stage endometrial cancer (toremifene, six; tamoxifen, three).

CONCLUSIONS

Toremifene is a valid and safe alternative to tamoxifen in postmenopausal women with endocrine-responsive breast cancer.

Tamoxifen and toremifene treatment of breast cancer and risk of subsequent endometrial cancer: a population-based case-control study

A population-based case-control study was performed to evaluate the risk of endometrial cancer related to tamoxifen or toremifene treatment. All patients with breast cancer diagnosis since 1980 in Finland who subsequently developed an endometrial cancer by the end of 1995 and 3 matched controls were identified among the 38,000 breast cancer patients of the Finnish Cancer Registry database. Detailed information on treatment of breast cancer and potential confounders was collected from hospital records. The OR for tamoxifen treatment (59 cases), adjusted for significant cofactors (increased risk associated with obesity, low parity and PR positivity) was 2.9 (95% CI 1.8-4.7). The OR for toremifene (3 cases) was 0.9 (95% CI 0.3-3.9). The OR related to adjuvant tamoxifen treatment reached its maximum 2-5 years after the beginning of treatment (OR 5.1, 95% CI 2.1-13), while the OR for tamoxifen used for palliative treatment of advanced breast cancer was especially high after a lag of over 5 years (OR 9.5, 95% CI 2.5-36). The risk increase due to tamoxifen was slightly higher if the age at initiation was below 55, and risk was more pronounced among patients with well-differentiated endometrial cancer than patients with cancers of clinical grades 2 or 3. According to our results, treatment with tamoxifen increases the risk of endometrial cancer. Due to the rare use of toremifene up to the mid-1990s, the risk assessment concerning it was inconclusive.

Comparative tolerability of first-generation selective estrogen receptor modulators in breast cancer treatment and prevention

In general, the selective estrogen receptor modulators (SERMs) currently indicated for the treatment and prevention of breast cancer, i.e. tamoxifen and toremifene, are fairly well tolerated. However, tamoxifen has been shown to induce hepatocellular carcinomas in rats, but not in humans, and can increase the risk of endometrial cancer in humans by two to three times. Other potentially serious adverse effects which have been associated with tamoxifen and toremifene therapy include vasomotor symptoms, an increased risk of venous thromboembolic events, and an increased incidence of cataracts and ocular toxicity, fatty liver, and nonmalignant hepatic and uterine changes. In addition, long term tamoxifen use almost always results in resistance to the drug and, indeed, has actually been shown to promote tumour proliferation in human breast cancer cells. Both tamoxifen and toremifene display drug interactions with a variety of drug classes. The adverse events associated with these compounds have raised significant concerns regarding their widespread use for the treatment and prevention of breast cancer. In addition, because of the weakness and scarcity of the data on toremifene, any conclusions about its tolerability remain tentative until outcomes of ongoing clinical trials in the adjuvant setting are known. A third SERM, raloxifene, is the focus of several large randomised trials examining its efficacy in the prevention of breast cancer. At present, each potential adverse event needs to be weighed against potential benefits in the decision to undergo SERM treatment. An array of therapies is currently available for patients with breast cancer and women at increased risk of disease; the risk-to-benefit ratio for each agent should be carefully examined in determining the most advantageous regimen.

Phase II trial of toremifene in androgen-independent prostate cancer: a Penn cancer clinical trials group trial

Toremifene has antiestrogenic and estrogenic properties in vitro and in vivo. In addition, it may have antiangiogenesis and antimicrotubule properties at higher doses. Studies have demonstrated the efficacy of this agent in the treatment of metastatic breast cancer. We performed a phase II trial of toremifene in patients with androgen-independent prostate cancer (AIPC). Patients with an increasing prostate-specific antigen level despite castrate testosterone levels and antiandrogen withdrawal were eligible. Patients could not have received prior salvage hormonal therapy or chemotherapy. Patients received toremifene at 300 mg/m2/d orally (maximum dose 640 mg/d). Fifteen patients were treated. Patients received treatment for a median of 13 weeks (range, 4-30 weeks). The median age was 72 years (range, 58-80 years). The median Eastern Cooperative Oncology Group performance status was 0. The treatment was well tolerated and toxicity was mild. Two patients had grade III hepatic toxicity; one had grade III hyperglycemia. There were no treatment-related deaths. No objective responses were demonstrated. In summary, toremifene is not effective therapy for AIPC at the dose and schedule evaluated in this trial.

Effects of oral administration of tamoxifen, toremifene, dehydroepiandrosterone, and vorozole on uterine histomorphology in the rat

Tamoxifen, toremifene, DHEA, and vorozole inhibit tumor growth in rodent mammary carcinoma models and are promising chemotherapeutic agents for use against breast cancer development. In the present study, the effect of these agents on uterine histomorphology following oral administration to mature ovary-intact rats (n = 380) was examined. Animals received diet only (control), tamoxifen (0.4 and 1 mg/kg of diet; 10 mg/kg BW by daily gavage), toremifene (3-30 mg/kg of diet), DHEA (24-2000 mg/kg of diet), or vorozole (0.08-1.25 mg/kg BW by daily gavage) for 28 days and were either sacrificed or returned to a basal diet and then sacrificed 21 days later. Treatment with toremifene (all doses) or tamoxifen (1 and 10 mg/kg) for 28 days produced a decrease (P<0.05) in overall uterine size and myometrial thickness; however, uterine luminal and glandular epithelia cell height increased (P<0.05) compared with control. These compartmentalized uterotrophic and antiestrogenic effects of toremifene and tamoxifen were still apparent after 21 days post-treatment. Administration of DHEA (2000 mg/kg of diet) for 28 days had dramatic uterotrophic effects, increasing (P<0.05) overall uterine size and stimulating all three uterine compartments (epithelia, stroma, and myometrium). The other doses of DHEA, however, were not uterotrophic. Interestingly, after removal of DHEA from the diet, uterine weight and myometrial thickness decreased (P<0.05). Vorozole (1.25 mg/kg) administration for 28 days had differential, compartmentalized uterine effects, producing an increase (P<0.05) in epithelial cell height, a decrease (P<0.05) in stromal size, but no change in myometrial thickness. After 21 days postadministration of vorozole, luminal epithelial cell height was increased (P<0.05) compared with control. The data suggest that oral administration of tamoxifen, toremifene, DHEA, and vorozole results in differential, compartmentalized effects in the uterus that are highly dependent on treatment dose. The data may have implications for risk assessment of these agents prior to administration to healthy, cancer-free women.

Silica xerogel carrier material for controlled release of toremifene citrate

Sol-gel processed silica xerogel was used as a carrier material for toremifene citrate in order to develop an implantable controlled release formulation which could be localised to a desired site providing targeted and long-lasting disease control and resulting in a reduced amount of drug needed. Toremifene citrate, an anti-estrogenic compound, was incorporated into silica xerogel matrixes during polycondensation of organic silicate, tetraethyl ortho silicate (TEOS). The effects of drug amount, drying temperature and polyethylene glycol (PEG) on the release rate of toremifene citrate and degradation of the silica xerogel matrixes were investigated. Addition of PEG (M(w) 4600/10000) decreased the specific surface area of the matrix and lowered the release rate of the drug. Reducing the amount of drug in the matrix also decreased the release rate of toremifene citrate. However, drying temperature did not affect the release rate of silica or toremifene citrate. The release profiles of toremifene citrate were according to zero order kinetics, suggesting that drug release was controlled by erosion of the silica xerogel matrix. These results suggest that the toremifene citrate release rate can be controlled to some extent by adding (PEG) or by varying the amount of drug in the silica xerogel matrix.

Silica xerogel as an implantable carrier for controlled drug delivery--evaluation of drug distribution and tissue effects after implantation

The purpose of the present study was to examine controlled delivery of toremifene citrate from subcutaneously implanted silica xerogel carrier and to evaluate silica xerogel related tissue effects after implantation. Toremifene citrate was incorporated into hydrolyzed silica sol in a room temperature process. Toremifene citrate treated silica xerogel implants were tested both in vitro and in vivo using healthy mice. Silica xerogel with tritium-labelled toremifene was implanted subcutaneously in mice for 42 d. To determine the amount of tritiated toremifene remaining in the silica discs at the implantation site, the discs were excised periodically and radioactivity measured. The amount of tritiated toremifene in the implant after 42 d was still about 16% and the amount of silica xerogel about 25%. In a histopathological study silica xerogel did not show any tissue irritation at the site of the implantation. A fibrotic capsule was formed around the implant. No silica xerogel related histological changes in liver, kidney, lymph nodes and uterus were observed during the implantation period. The silica xerogel discs showed a sustained release of toremifene citrate over 42 d. Histologically, toremifene-related changes in the uterus were also detectable at all studied time points. These findings suggest that silica xerogel is a promising carrier material for implantable controlled drug delivery system.

Selective estrogen receptor modulators: tissue selectivity and differential uterine effects

Selective estrogen receptor modulators (SERMs) are compounds that bind to estrogen receptors and produce estrogen-like (agonist) effects in some tissues and estrogen-blocking (antagonist) effects in other tissues. One of the goals of SERM research has been to develop compounds that provide the potential benefits of estrogen in the skeleton and cardiovascular system, but avoid the negative effects of estrogen in other tissues. Estrogen therapy has been consistently associated with endometrial stimulation, including glandular proliferation, hyperplasia and cancer. In contrast, the presence or degree of endometrial stimulation observed with SERMs varies by compound. The purpose of this review is to differentiate the endometrial effects of compounds that display a SERM-like profile. Molecular mechanisms involving SERM binding to estrogen receptors, preclinical uterine effects in both tissue culture and animal models, and endometrial findings in clinical experience are discussed. There are several SERMs commercially available or in development. The favorable safety profile of raloxifene in the uterus differentiates it from the others. Future SERM development will continue to focus on finding compounds that exhibit minimal endometrial stimulation.

In vitro release behavior of toremifene citrate from sol-gel processed sintered silica xerogels

Factors affecting the adsorption and desorption of toremifene citrate (TC) on sintered silica xerogels were investigated in vitro. TC was attached onto sol-gel processed sintered silica xerogel grains or disks by adsorption. The adsorption of TC on the surface of silica was pH dependent. The results support the conclusion that large pore size results in highest drug adsorption. Adsorption of TC was most effective in xerogels sintered at 700 degrees C and containing the largest pores and lowest specific surface area of the silica xerogels studied in the adsorption tests. The release of TC from the xerogel matrix was linear with respect to the square root of time. The release of TC from the grains was very rapid for the first 5 hr, followed by a slower release. All drug was released from the grains, and 60% to 80% was released from the disks in 24 hr. All drug-silica xerogel formulations showed sustained in vitro release profiles.

The evolving role of specific estrogen receptor modulators (SERMs)

Estrogens are the most effective therapy for women with postmenopausal problems. However, relatively few women use estrogen and then often for a limited time because of the fear of its carcinogenic effects on the uterus and breast; in addition, estrogen is not advised for women who have had breast cancer. Selective estrogen receptor modulators (SERMs) are agents with antagonist action on the uterus and breast and agonist action on the bones, cardiovascular system, and brain. Unlike estrogens, however, existing SERMs do not help alleviate the vasomotor and urogenital problems associated with menopause. A comprehensive review of the literature published from January 1995 to June 1999 was conducted. Reports were identified using Medline and Cancer Lit. The effect of menopausal problems on the health of women and the socioeconomic effects of menopause are discussed. All currently available and investigational SERMs are reviewed and discussed, including their mechanism of action, metabolism, dose scheduling, antitumor activity, and potential role in maintaining the health of menopausal women and in preventing breast cancer.

Uterotrophic effects of tamoxifen, toremifene, and raloxifene do not predict endometrial cell proliferation in the ovariectomized CD1 mouse

The uterotrophic responses of ovariectomized CD1 mice to tamoxifen, toremifene, and raloxifene have been compared to 17beta-estradiol after a treatment period of 72 h. Uterine and vaginal weight, luminal epithelial thickening, and 5-bromodeoxyuridine (BrdU) labeling index in the endometrial stroma were examined. All three pharmaceuticals, as well as 17beta-estradiol, produced increases in the classic estrogen-dependent variables of uterine and vaginal weights after the 3-day treatment period. Tamoxifen, toremifene, raloxifene, and estradiol all increased luminal epithelial thickness, and increased the BrdU labeling index in the endometrial stroma of the uterus. Although the dose response for the uterotrophic effect and the vaginal weight increases for toremifene differed from tamoxifen and raloxifene, in that there was no dose at which these effects were maximal, the stimulation of BrdU labeling index in the endometrial stroma was dose dependent and very similar for all three, at the clinically relevant doses. Treatment-related hypertrophic effects were estimated by examination of the nuclear profile density in the endometrial stroma. Estradiol and tamoxifen caused a greater hypertrophic effect than toremifene and raloxifene, indicating that factors other than an increase in cell number contribute to the overall uterotrophic effect. This demonstrates that the use of uterine weight to estimate the relative estrogenicity of drugs could give a misleading impression of the response of the uterus to estrogen agonists. Variables, such as increased DNA replication, which may be more important to a subsequent potential carcinogenic process in the uterus, for a particular drug, requires separate evaluation.

In vitro evaluation of biodegradable epsilon-caprolactone-co-D, L-lactide/silica xerogel composites containing toremifene citrate

Poly(epsilon-caprolactone-co-D,L-lactide) polymers were blended with toremifene citrate or with toremifene citrate impregnated silica xerogel in order to develop a controlled release formulation. The copolymers were synthesized by bulk polymerization and characterized by nuclear magnetic resonance, size exclusion chromatography and differential scanning calorimetry analyses. The in vitro release of toremifene citrate, an antiestrogenic compound, and silica was carried out in simulated body fluid (pH 7.4) containing 0.5 wt% sodium dodecylsulphate at 34 degrees C. The in vitro release studies indicate that the release flux of toremifene citrate increases with increasing weight fraction of caprolactone in the copolymer. Silica xerogel had a minor enhancing effect on the release rate of toremifene citrate. Copolymers containing larger amounts of D,L-lactide (PLA-CL20 and PLA-CL40 copolymers) were not suitable matrices for the delivery of toremifene citrate in a controlled manner because of the burst effect. The fraction of toremifene citrate released from PLA-CL80 matrix increased with the increasing loading of toremifene citrate. The results of the study indicate that the in vitro release of toremifene citrate can be adjusted by varying the polymer composition and also the initial drug loading.

The effect of toremifene on bone and uterine histology and on bone resorption in ovariectomised rats

The effect of the selective oestrogen receptor modulator, toremifene, to inhibit ovariectomy-induced bone loss was studied in rats. The oral doses were 0.3, 3.0 or 30 mg/kg/day for 2 months. 17beta-oestradiol (5 microg/kg/day, subcutaneously) was used as positive control. One group was also treated with a combination of 17beta-oestradiol (5 microg/kg) and toremifene (3.0 mg/kg). Biochemical markers were urinary hydroxyproline and calcium (adjusted with urinary creatinine levels) and the serum level of pyridinoline cross-linked carboxy terminal telopeptide, a bone specific collagen breakdown product. The femoral and sternal trabecular bone thickness served as histological parameters. Ovarectomy increased the levels of hydroxyproline and pyrodinoline and decreased the trabecular bone thickness compared to the sham-operated control group. This was inhibited by both test compounds but 17beta-oestradiol was more efficient. Toremifene did not reverse the ovariectomy-induced reduction of urinary calcium but inhibited the 17beta-oestradiol-related increase. When administered together with oestradiol, toremifene did not reverse the positive effect of 17beta-oestradiol on bone, however toremifene reversed the oestradiol-related uterothrophic effects. These findings indicate that the antagonistic features of toremifene dominate in the rat uterus the agonistic properties do in the bone.

Sol-gel-processed sintered silica xerogel as a carrier in controlled drug delivery

Sol-gel-processed sintered silica xerogel was studied as a controllable, dissolvable, implantable material. The erosion of the matrix and the release of the preadsorbed drug toremifene citrate was investigated both in vitro and in vivo using mice. In an in vitro dissolution study, 50 to 60% of the drug was released after 24 h, according to the square root of time kinetics, and the weight loss of the silica was 24 wt %. Silica xerogel with tritium-labeled toremifene was implanted subcutaneously in mice for 56 days. To determine the amount of tritiated drug remaining in the silica disks at the implantation site, the disks were excised periodically and the radioactivity measured. About 40% of the radioactivity was released during the first 4 days and all of it within 28 days. Radioactivity also was measured in the liver, lungs, kidneys, uterus, and blood. The radioactivity reached a maximum level after 4 days in the liver, kidneys, and lungs and slowly decreased until all of the drug had been released from the matrix after 28 days. After release of the drug (28 days) the amount of remaining silica xerogel implant was 45 wt %, and at the end of the study (56 days) it was 24 wt %. In the histopathological study, sintered silica xerogel did not show any tissue toxicity at the site of the implantation, in the liver, or in the kidneys. It was concluded that sintered silica xerogel is a biocompatible and controllably resorbable material and therefore is a promising matrix for use in the sustained delivery of drugs.

Genotoxicity studies with the antiestrogen toremifene

Toremifene, a second-generation triphenylethylene antiestrogen used clinically in the chemotherapy of breast cancer and some other cancers, differs in its nonclinical toxicology from its first-generation congener tamoxifen. Tamoxifen produces DNA adducts and tumors in rat liver, whereas assays for DNA adduct formation with toremifene have been negative to weakly positive, and toremifene does not produce liver tumors in rats. To evaluate further toremifene for possible genotoxicity, it was tested in three standard, in vitro assay--reversion of bacterial point mutations, unscheduled DNA synthesis in cultured hepatocytes from two rat strains, and cytogenetics of human lymphocytes in primary culture--and in one in vivo assay, the mouse, erythrocyte micronucleus assay. The three in vitro assays were conducted with toremifene at up to the limit of cytotoxicity (100 to 250 micrograms/ml, depending on the system). The bacterial mutagenicity and lymphocyte chromosome aberration assays were performed both in the presence and absence of metabolic activation by Araclor-induced, rat liver S-9, while the hepatocyte unscheduled DNA synthesis assay provides intrinsic bioactivation. To test for chromosome damage in vivo, mice were administered up to 2g/kg toremifene once by gavage, and bone marrow was harvested daily, for three days. Normochromatic and polychromatic bone marrow erythrocytes were examined for micronuclei. Toremifene lacked genotoxicity or myelotoxicity detectable by any of the above assays. These findings, together with the reported absence of DNA binding in rat liver, provide evidence that toremifene is not genotoxic.

Cyclophosphamide, adriamycin, 5-fluorouracil and high-dose toremifene for patients with advanced/recurrent breast cancer. The Japan Toremifene Cooperative Study Group

BACKGROUND

Multi-combination chemotherapy consisting of anthracyclines has been effective but has not invariably prolonged the survival period in advanced/recurrent breast cancer. The possibility has been discussed that chemoendocrine therapy combined with endocrine agents is more effective.

METHODS

In order to evaluate the toxicity and efficacy of a new endocrine therapy for advanced/recurrent breast cancer, we ran a pilot study during the period from July 1994 to July 1996.

RESULTS

Twenty-two patients with advanced/recurrent breast cancer were treated with chemoendocrine therapy consisting of cyclophosphamide (100 mg/body) p.o. daily for 14 days, with adriamycin (40 mg/m2) i.v. and 5-fluorouracil (500 mg/body) i.v. on day 1 (repeated every 3 weeks for 9 weeks) (CAF therapy), and high-dose toremifene (120 mg/body) p.o. daily. Of 20 evaluable patients, two showed complete response (10%), eight partial response (40%), six no change (30%) and four progressive disease (20%). The overall response rate was 50%, and the median duration of response was 69.5 days (28-133+ days). The major toxicities were drug-induced alopecia, gastrointestinal toxicity and hematological toxicity, but these were clinically well tolerated. No serious cardiac, liver or renal symptom was seen.

CONCLUSIONS

Based on these results, we consider the addition of high-dose toremifene to the CAF therapy to be useful in the treatment of advanced and recurrent breast cancer.

Toremifene. A review of its pharmacological properties and clinical efficacy in the management of advanced breast cancer

The triphenylethylene antiestrogen toremifene is a chlorinated derivative of the antiestrogen tamoxifen, an agent which has been widely and successfully used in the treatment of breast cancer. Clinical trials investigating the efficacy of toremifene as first-line endocrine therapy in postmenopausal women with advanced breast cancer (estrogen receptor status positive or unknown) have shown this drug to have similar antitumour activity to that of tamoxifen. In multicentre comparative trials, objective responses (complete and partial) occurred in 20 to 29% of patients treated with toremifene (60 to 240 mg/day) and in 19 to 37.5% of tamoxifen (20 or 40 mg/day) recipients. The duration of response, time to disease progression and median overall survival time were generally similar in both treatment groups. Toremifene is well tolerated. Most drug-related adverse effects are mild or moderate in severity and rarely necessitate discontinuation of therapy. The tolerability profile of toremifene is similar to that reported for tamoxifen, the most common adverse effects being hot flushes, sweating, nausea and/or vomiting, dizziness, oedema, and vaginal discharge and/or bleeding. Thus, toremifene provides an equally effective and well tolerated alternative to tamoxifen for the first-line endocrine therapy of postmenopausal advanced breast cancer. Preclinical studies showing toremifene to have a lower carcinogenic potential than tamoxifen indicate that toremifene may be a preferable agent for long term treatment regimens; however, these findings require confirmation in the clinical setting.

Comparison of toremifene and tamoxifen in post-menopausal patients with advanced breast cancer: a randomized double-blind, the 'nordic' phase III study

The study was planned to compare, in a prospective double-blind randomized trial, the efficacy and safety of toremifene (TOR) and tamoxifen (TAM) in post-menopausal patients with advanced breast cancer who have not had prior systemic therapy for advanced disease. Four hundred and fifteen post-menopausal patients with oestrogen receptor (ER)-positive or ER-unknown advanced breast cancer were randomly assigned to receive daily either 60 mg TOR or 40 mg TAM. The patients were stratified to measurable and non-measurable but evaluable groups. They were assessed for response to therapy, time to progression (TTP), time to treatment failure (TTF), response duration, overall survival and drug toxicity. Two hundred and fourteen patients were randomized into TOR and 201 into TAM treatment. The response rate (complete + partial) was 31.3% for TOR and 37.3% for TAM (P = 0.215). The 95% confidence interval (CI) for the 6% difference was -15.1% to 3.1%. The median TTP was 7.3 months for TOR and 10.2 months for TAM (P = 0.047). The 95% CI for the hazard ratio of 0.80 was 0.64-1.00. A percentage of the TOR patients (9.8%) and the TAM patients (18.9%) discontinued the treatment prematurely (P = 0.011) for various reasons. Consequently, the median TTF of 6.3 vs 8.5 months did not differ significantly (P = 0.271). The hazard ratio was 0.89 and the subsequent 95% CI 0.73-1.09. The median overall survival was 33.0 months for TOR and 38.7 months for TAM (P = 0.645). The hazard ratio was 0.94 with 95% CI of 0.73-1.22. The transient difference in TTP may be related to an imbalance in ER content of the tumours. When only patients with ER-positive tumours were considered (n = 238), no difference between two treatments was seen (P = 0.578). TAM was associated with an overall slightly higher frequency of adverse drug reactions than TOR (44.3 vs 39.3%) and a higher discontinuation rate due to these events (3.5% vs 0.9%). Treatment-emerged moderate dizziness (P = 0.026) and cataracts (P = 0.026) were more frequent among TAM than among TOR patients. In conclusion, TOR (60 mg day(-1)) and TAM (40 mg day(-1)) are equally effective and safe in the treatment of advanced post-menopausal ER-positive or ER-unknown breast cancer.

A two-year dietary carcinogenicity study of the antiestrogen toremifene in Sprague-Dawley rats

The carcinogenic potential of the nonsteroidal triphenylethylene antiestrogen toremifene (Fareston) was evaluated in a standard 104-week rat dietary carcinogenicity study. The doses were 0, 0.12, 1.2, 5.0 and 12 mg/kg/day and the number of animals 50/sex/dose group. The body weight gain and food consumption were monitored once weekly (study weeks 1-16) or once every four weeks thereafter (study weeks 17-104). Blood samples were taken at weeks 34, 52 and 104 and the plasma concentrations of toremifene, as well as the two main metabolites (deaminohydroxy)toremifene and N-demethyltoremifene, were measured. All doses of toremifene reduced food intake and body weight gain. Toremifene caused a significant reduction in mortality, which was mainly due to reduced incidences of pituitary tumors. This was evident in all dose groups. Drug-related decrease of mammary tumors in females (at all doses) and testicular tumors in male rats (doses > or = 1.2 mg/kg/day) were also evident. The incidence of the preneoplastic foci of basophilic hepatocytes were significantly decreased in treated female groups. Toremifene induced no preneoplastic or neoplastic lesions. Based on histopathology, no obvious toxicity could be observed. Drug-related changes were observed in the genital organs, thyroid, spleen, mammary gland, adrenal, kidney, stomach and lung. These changes were due to hormonal disturbances or as a result of reduced food consumption or reduced incidences of pituitary, mammary or testicular tumors. This study indicates that toremifene is an efficient antiestrogen in long-term treatment, is well tolerated and has no tumorigenic potential in rats.

Cell proliferation in dimethylbenz(A)anthracene(DMBA)-induced rat mammary carcinoma treated with antiestrogen toremifene

Cell proliferation during antiestrogen toremifene treatment was studied using the DMBA-induced rat mammary carcinoma model. The volume corrected mitotic index (M/V INDEX) and the S-phase fraction (SPF) determined by flow cytometry (FCM) were used as proliferation markers. Two series of rats (A and B) treated with two dose levels of toremifene were used. The two series of tumors appeared to have different growth properties. In series A the tumors were rapidly growing with high proliferation rate. In this series, toremifene (3 mg/kg for 4 weeks) reduced significantly the mean MV/INDEX, but the slight reduction of the mean SPF was not significant. In series B the tumors grew slowly and had low levels of proliferation markers. One-third of the tumors were spontaneously stable in the untreated group. Higher dose of toremifene was used in this series (12 mg/kg for 4 weeks), and the number of regressing or stable tumors was 58% compared with 31% in series A. Taking into consideration the high number of spontaneously stable tumors in series B, it may be concluded that about one-third of the tumors regressed or remained stable due to toremifene treatment in both series. The reduction of the M/V INDEX was significant only when the regressing treated tumors were compared with the growing controls. The reduction of the SPF was not significant. We think that the M/V INDEX is a more appropriate method to measure cell proliferation than is the SPF in this tumor model, where the tumors are heterogenous and, e.g., spontaneous apoptosis is known to be frequent.

High dose toremifene for estrogen and progesterone receptor negative metastatic breast cancer: a phase II trial of the Cancer and Leukemia Group B (CALGB)

In pre-clinical and limited clinical studies, high doses ( > or = 200 mg/day) of the triphenylethylene derivative toremifene showed activity in estrogen receptor (ER) negative and ER-unknown metastatic breast cancer after progression on tamoxifen, and a mechanism of action independent of hormone receptor binding was speculated. The CALGB conducted a Phase II trial (CALGB 8945) to test the efficacy of high dose toremifene in a population of patients who had hormone receptor-negative, metastatic breast cancer with limited prior chemotherapy exposure, good performance status, and measurable disease. Twenty eligible patients received toremifene at a dose of 400 mg/day orally for 8 weeks. Toxicity was minimal. Nausea was reported by 20% of the patients, lightheadedness by 20%, weight loss by 20%, and hot flashes by 15%. There was no grade 3-4 toxicity. No objective responses were observed, and 5 of 6 patients with stable disease at 8 weeks developed progressive disease at 11 to 33 weeks. High dose toremifene (400 mg/day) is well-tolerated but imparts no detectable activity in hormone receptor-negative, metastatic breast cancer.

Imaging, biodistribution and therapy potential of halogenated tamoxifen analogues

Tamoxifen binds to estrogen receptors (ERs) and prevents breast cancer cell proliferation. This study is aimed at developing a ligand for imaging ER (+) breast tumors by positron emission tomography (PET) or single photon emission computed tomography (SPECT). [18F]-Labeled tamoxifen analogue ([18F]FTX) was prepared in 30-40% yield and [131I]-labeled tamoxifen analogue ([131I]ITX) was prepared in 20-25% yield. In mammary tumor-bearing rats, the biodistribution of [18F]FTX at 2 h showed a tumor uptake value (% injected dose/gram tissue) of 0.41 +/- 0.07; when rats were pretreated with diethylstilbestrol (DES), the value changed to 0.24 +/- 0.017. [131I]ITX at 6 h showed a tumor uptake value of 0.26 +/- 0.166; when rats were pretreated with DES, the value changed to 0.22 +/- 0.044. Priming tumor-bearing rats with estradiol, a tumor uptake value for [131I]ITX was increased to 0.48 +/- 0.107 at 6 h. In the [3H]estradiol receptor assay, tumors had a mean estrogen receptor density of 7.5 fmol/mg of protein. In gamma scintigraphic imaging studies with [131I]ITX, the rabbit uterus uptake can be blocked by pretreatment with DES. Both iodo-tamoxifen and tamoxifen reduced ER(+) breast tumor growth at the dose of 50 micrograms in tumor-bearing mice. The findings indicate that tamoxifen analogue uptake in tumors occurs via an ER-mediated process. Both analogues should have potential for diagnosing functioning ER(+) breast cancer.

Influence of toremifene on the endocrine regulation in breast cancer patients

In a combined phase I-II study, the hormonal effects of toremifene (TOR) were investigated in 30 patients. Half of the patients received continuous therapy of TOR 60 mg and half 300 mg of TOR orally daily. Serum concentrations of oestradiol (E2), progesterone (PROG), testosterone (TE), follicle stimulating hormone (FSH), luteinising hormone (LH), prolactin (PRL), human growth hormone (hGH) and sex hormone binding globulin (SHBG) were monitored prior to the treatment and at the second, sixth, eighth and twelfth weeks. The influence of TOR upon the hypothalamo-hypophyseal axis was investigated by the TRH (thyroid-stimulating hormone releasing hormone) functional test using 400 micrograms intravenous injection of TRH for stimulation of PRL secretion. The concentration of E2 decreased during the TOR therapy with 60 mg and 300 mg causing 82 and 71% decreases, respectively (non-significant). PRL was significantly (P < 0.001) suppressed. Both these effects reflect the anti-oestrogenic action of TOR. SHBG increased significantly at both doses of TOR, probably due to a direct oestrogen-like effect of TOR in the liver. TE decreased as a consequence of the elevated SHBG. The TRH-induced PRL release was suppressed by both doses of TOR. There were 17 and 27% reductions at 12 weeks in the 60 and 300 mg groups, respectively. Other hormones measured were not significantly affected by TOR. The hormonal effects of 60 and 300 mg doses of TOR did not differ significantly. Anti-oestrogenic (i.e. decrease of E2), and partially oestrogenic (i.e. increase of SHBG) properties as well as the antiprolactinic effects of TOR may have an overall beneficial effect in the clinical management of breast cancer patients.

Toremifene and tamoxifen in advanced breast cancer--a double-blind cross-over trial

Toremifene (TOR) is a triphenylethylene derivative related to tamoxifen (TAM). TOR has antitumor activity, not dependent on estrogen receptors, and responses with TOR have been observed in patients with progressive disease during TAM-treatment. To elucidate possible cross-resistance between these two antiestrogens, we compared their anti-tumor activity in a randomized, double-blind, cross-over study. 66 postmenopausal women with advanced estrogen receptor positive or unknown breast cancer and a median age of 63 years (range 38-82) were included. Patients were randomized to TAM 40 mg/day or TOR 240 mg/day. Treatment continued until progressive disease, when cross-over to the alternative treatment was done. The response rate with first line TOR was 29% (95% confidence limits 10-41%) and with TAM 42% (95% confidence limits 25-61%). Response rates and response durations, survival and toxicity were not significantly different between the two treatments. 44 patients progressing on first line TAM or TOR were evaluable for second line TOR or TAM treatment. As no responses were observed, the possibility of over-looking a response rate of 20% or more is less than 1%. In conclusion, this study strongly indicates that TOR and TAM are clinically cross-resistant in patients with advanced breast cancer.

Effect of toremifene on the growth, hormone receptors and insulin-like growth factor-1 of hormone-dependent MCF-7 tumors in athymic mice

Toremifene given in different sizes of silastic capsules was used to treat MCF-7 tumors in athymic mice. Toremifene inhibited the estradiol-stimulated growth of MCF-7 tumors in athymic mice. Average serum concentrations of toremifene obtained using a sustained-release preparation of the drug (in 0.5-, 1.0-, and 2.0-cm silastic capsules) increased gradually in a capsule-size-dependent fashion. Much higher levels of toremifene or N-demethyl-toremifene were detected in tumors (target tissues of estrogen) as compared with muscles (non-target tissues of estrogen). The concentration of toremifene in serum (i.e., 10-30 ng ml-1) was sufficient to inhibit the estrogen-stimulated growth of MCF-7 tumors at physiological (i.e., 200-400 pg ml-1) serum estradiol concentrations in premenopausal women. No significant difference in estrogen receptor (ER) levels was found between the estradiol-alone group and the toremifene-treated groups. However, the ER levels in the toremifene-alone group and the no-treatment group (no toremifene or estradiol) tended to increase as compared with the estradiol-alone group. Toremifene blocked the estradiol-induced increase in progesterone receptor levels in a dose-dependent fashion. Insulin-like growth factor-1 (IGF-1) levels in the MCF-7 tumors significantly decreased in the toremifene-alone group as compared with the estradiol-alone group. These results show the antiestrogenic action of toremifene on hormone-dependent MCF-7 tumors in athymic mice.

The effects of diethylstilbestrol, tamoxifen, and toremifene on estrogen-inducible hepatic proteins and estrogen receptor proteins in female rats

Alterations of estrogen-inducible hepatic proteins and estrogen receptor proteins were studied in female rats after daily oral administration of vehicle control (0.5% carboxymethylcellulose), the nonsteroidal antiestrogens tamoxifen (TAM; 3, 11, or 45 mg/kg body weight), toremifene (TOR; 3, 12, or 48 mg/kg body weight), or the potent synthetic estrogen diethylstilbestrol (DES; 10 mg/kg body weight) for 1 and 3 months. Serum corticosterone levels were significantly reduced by TAM 11, TOR 12, and DES at 1 month and by TOR 48 and DES at 3 months. Serum ceruloplasmin levels were unchanged at 1 month except for a significant reduction with TOR 48 and a significant increase in the DES-treated group. After 3 months, all doses of TAM and TOR had significant reductions whereas DES had elevations even greater than those at 1 month. The activity of the enzyme alanine aminotransferase in the liver was increased by TAM, TOR, and DES at 1 and 3 months of treatment. Both TAM and TOR caused a slight reduction in cytosolic estrogen receptor protein after 1 month and significant reductions at 3 months. The nuclear estrogen receptor (nER) protein levels were significantly increased at 1 and 3 months for TAM and TOR; whereas DES treatment resulted in nER levels no different than controls. In summary, chronic (up to 3 months) administration of TAM and TOR results in qualitatively and quantitatively similar hormone-related effects on the female rat liver. Thus, other mechanisms must be investigated to ascertain the hepatoproliferative differences seen with TAM administration but not with TOR.

Phase I clinical and pharmacokinetics study of high-dose toremifene in postmenopausal patients with advanced breast cancer

Toremifene is an antiestrogen that binds strongly to estrogen receptors (ER). A total of 19 previously treated postmenopausal women with metastatic breast cancer whose performance status was good and whose ER status was positive or unknown were studied to determine the maximum tolerated dose of toremifene. Cohorts of patients received 200, 300, or 400 mg/m2 p.o. daily until relapse or unacceptable toxicity had occurred. Nausea, vomiting, and dizziness were dose-related. Three of five patients receiving 400 mg/m2 experienced moderate or severe vomiting and another developed reversible disorientation and hallucinations. Mild sweating, peripheral edema, vaginal discharge, and hot flushes were encountered at all doses. Reversible corneal pigmentation was identified in seven cases but was not of clinical importance. The pharmacokinetics of toremifene was studied weekly and in detail on day 42 using a high-performance liquid chromatographic (HPLC) assay that identified the parent compound and three active metabolites, N-desmethyltoremifene, (deaminohydroxy)toremifene, and didemethyltoremifene. Steady state was achieved at 1-3 weeks. The toremifene area under the curve and the maximal concentration were dose-dependent at high doses. The recommended phase II dose is 300 mg/m2 p.o. daily.

Determination of 2-fluoro-2-deoxy-D-glucose uptake and ATP level for evaluating drug effects in neoplastic cells

The glucose analogue 2-fluoro-2-deoxy-D-glucose (FDG) was used to study chemosensitivity of two human ovarian cancer cell lines and of murine L1210 cells. Cell viability was determined by measuring intracellular adenosine triphosphate (ATP) with a bioluminescence method, which has been shown to correlate closely with trypan blue, stem cell, and [3H]TdR assays. All three cell lines were sensitive to cytostatic drugs, which exerted a parallel decrease in the intracellular FDG and ATP levels. The two measures correlated positively (r = 0.66, P less than 0.001), indicating that FDG uptake is closely linked with ATP production. Relatively low hexokinase (HK)-to-glucose 6-phosphatase (HK/G6-Pase) ratios were measured, which suggests that the metabolic trapping of FDG 6-phosphate within the cytosol is incomplete. Apparently, these cell lines may not depend exclusively on glycolysis for their energy requirement. We conclude that cell killing caused by cytostatic drugs is associated with a decreased ATP content and FDG uptake. This indicates that not only ATP but also FDG may be used to study drug effects in vitro.

Estrogen suppression of erbB2 expression is associated with increased growth rate of ZR-75-1 human breast cancer cells in vitro and in nude mice

Amplification and enhanced expression of the erbB2/HER-2/neu gene has been associated with an increased growth rate and poor prognosis of human breast cancer. We have studied the relationship between erbB2 expression and the regulation of cell growth by estrogen and anti-estrogens in the human breast cancer cell line ZR-75-1 in vitro and in athymic nude mice, pS2 being used as a marker gene for estrogen-stimulated gene expression. Only low amounts of erbB2 mRNA were seen in the cells grown in vitro in the presence of estrogen which stimulated the cells to proliferate rapidly and induced the expression of pS2 mRNA. Upon hormone withdrawal, erbB2 mRNA and protein increased, while pS2 mRNA declined to an undetectable level and cell proliferation slowed down. Opposite but more rapid changes were observed upon estrogen addition. The anti-estrogens toremifene and tamoxifen inhibited estrogen induction of pS2 expression, down-regulation of erbB2 expression and proliferation of the ZR-75-I cells in a concentration-dependent manner. Similar results were obtained in nude mice. ZR-75-I cells formed tumors only in mice carrying estrogen pellets. In these tumors little erbB2 mRNA was seen. Concomitant administration of toremifene or tamoxifen increased erbB2 mRNA and abolished pS2 mRNA. Our results show that enhanced expression of erbB2 is associated with hormone deprivation and growth arrest of the estrogen-dependent breast cancer cell line ZR-75-I. Thus, in mammary epithelial cells, erbB2 may have important estrogen-regulated functions which are not related to cell proliferation.

The effect of toremifene therapy on serum immunoglobulin levels in breast cancer

Estrogens and anti-estrogens enhance the number of immunoglobulin (Ig)-secreting cells in pokeweed mitogen (PWM)-stimulated lymphocyte cultures. Lymphocytes from patients who have received anti-estrogen therapy show similar enhancement of Ig-secreting cells after PWM stimulation. In this study the effect of anti-estrogen (toremifene) therapy on serum immunoglobulin (IgA, IgM, IgG) levels in breast cancer patients was investigated. Serum Ig levels were followed up to two years after or during the therapy. An unexpected finding was that the Ig levels decreased during the follow-up period. This decrease was seen in patients who responded to the therapy as well as in those who did not.

The effects of anti-estrogen therapy on lymphocyte functions in breast cancer patients

The effects of anti-estrogen therapy (tamoxifen or toremifene) on in vitro lymphocyte functions were investigated in breast cancer patients. We found that the amount of DNA synthesis, with or without PWM stimulation, was decreased in all cancer patient groups compared to normal controls. The number of Ig-secreting cells was enhanced in unstimulated peripheral blood lymphocyte cultures but decreased in PWM-stimulated cultures. This occurred in all cancer patient groups investigated, with or without anti-estrogen therapy, as compared to healthy controls. On the other hand, subsequent samples with two-month intervals showed that anti-estrogens can increase PFC responses and inhibit DNA synthesis of peripheral blood lymphocytes in more than half of the patients. Interestingly, the enhancing dexamethasone effect, which usually causes an increase in the number of Ig-secreting cells in PWM-stimulated cultures, was also seen more often in anti-estrogen-treated patients. These results suggest that anti-estrogens may have immunoregulatory effects in vivo.

Synthesis and in vitro receptor binding studies of fluorotamoxifen analogues

We describe the synthesis of new fluorotamoxifen analogues with the fluorine atom positioned on the end of the aliphatic chain of tamoxifen. The binding of fluorotamoxifens to cytosol estrogen receptors of rat uteri was determined with [3H]estradiol (5 nM). The fluorotamoxifens had similar or superior binding affinities compared with tamoxifen. The IC50 value was as follows: tamoxifen, 5 x 10(-7) M; fluorotamoxifen (VII), 5 x 10(-7) M; N,N-diethylfluorotamoxifen (IV)-cis, 1 x 10(-6) M, and trans, 2 x 10(-7) M; and (cis) fluoromethyl-N,N-diethyltamoxifen (VI) 1 x 10(-7) M. Therefore, the fluorinated tamoxifens have potential use in imaging estrogen receptors by PET.

Antiestrogen therapy for breast cancer: current strategies and potential causes for therapeutic failure

There is an enormous literature that supports the use of tamoxifen as the treatment of choice for breast cancer. However, preliminary evidence suggests that long-term treatment with tamoxifen may expose the women to an increased risk of liver and endometrial cancer. This is probably only of concern to young women with stage I (node negative) disease. It remains to be seen whether any of the new strategies, including the new antiestrogens discussed here and novel endocrine therapies, will prove any better as an antitumor treatment. Treatments will probably be directed initially at treating patients after tamoxifen failure and ultimately at treating hormone-independent cancers. These therapies may involve the autocrine growth factors produced by breast cancer cells as potential targets. Such development of novel treatments will be extremely beneficial to these women, who face a worrying lack of therapeutic opportunities, with the exception of chemotherapy.

Effects of the antiestrogen toremifene on growth of the human mammary carcinoma cell line MCF-7

The effects of toremifene, a new antiestrogenic drug, were investigated in vitro on the exponentially growing human mammary carcinoma cell line MCF-7. The drug effects were monitored by serial cell counts and DNA flow cytometry. The inhibitory effect of toremifene on MCF-7 became greater as the drug concentration was increased from 1 microM to 10 microM. At 5 microM toremifene induced a large decrease in the relative percentages of S- and G2/M-phase cells, and an increase in the amount of cell debris, indicating increased cell death. After withdrawal of the drug the mammary cancer cells resumed logarithmic growth similar to that of control cells. The effects caused by toremifene were similar to those caused by tamoxifen both in quality and quantity.