Induction of Invasive Transitional Cell Bladder Carcinoma in Immune Intact Human MUC1 Transgenic Mice:  A Model for Immunotherapy Development

A preclinical model of invasive bladder cancer was developed in human mucin 1 (MUC1) transgenic (MUC1.Tg) mice for the purpose of evaluating immunotherapy ...

University of California, Davis

Selective estrogen receptor modulators, or SERMs, are a class of compounds that can act as estrogen receptor (ER) agonists in some tissues while acting as ER antagonists in others. SERMs are being evaluated and used to treat and prevent such diseases as breast cancer, osteoporosis, and cardiovascular disease. Currently, three primary SERMs are used clinically, which include tamoxifen, toremifene (triphenylethylenes), and raloxifene (a benzothiophene). Tamoxifen and toremifene have beneficial effects on bone and serum lipids, and are currently used to treat breast cancer. Both have stimulatory effects on the uterus. Raloxifene, indicated for the treatment and prevention of osteoporosis, also has beneficial effects on bone and serum lipids, but does not stimulate the uterus. All three are associated with venous thromboembolism and hot flashes. New SERMs to treat and prevent breast cancer, osteoporosis, and cardiovascular disease are undergoing clinical development, including idoxifene, droloxifene, ospemifene, lasofoxifene, arzoxifene, and MDL 103,323.

SERMs: current status and future trends.

Selective estrogen receptor modulators (SERMs) are a class of compounds used to treat and prevent breast cancer and osteoporosis. SERMs currently approved for use in patients include tamoxifen, toremifene and raloxifene. These compounds are well tolerated in patients, and the most common adverse effects experienced in patients undergoing SERM therapy include vasomotor symptoms such as hot flashes and vaginal discharge. New SERMs currently under development for use in the treatment and prevention of osteoporosis and breast cancer include ospemifene, a derivative of toremifene, and arzoxifene, a compound very similar in structure to raloxifene. SERMs are administered orally at doses ranging from 20 to 60 mg/day. Tamoxifen and toremifene have a bioavailability of approximately 100%, whereas that of raloxifene is only 2%. SERMs are very highly bound to plasma proteins (>95%). Tamoxifen and toremifene are metabolised by the cytochrome p450 enzyme system, and raloxifene is metabolised by glucuronide conjugation. The terminal elimination half-lives of these drugs range from 27.7 hours to 7 days. The pharmacokinetics of these compounds are affected in hepatically impaired patients, but not in renally impaired patients. SERMs have several potential drug interactions with other agents, such as warfarin, rifampicin (rifampin), cholestyramine and aromatase inhibitors.

Pharmacokinetics of selective estrogen receptor modulators.

Ospemifene is a new selective estrogen receptor modulator (SERM) that is being developed for the treatment of urogenital atrophy and osteoporosis. Similarly to other SERMs, ospemifene exhibits antiestrogenic effects in breast tissue, which led to the hypothesis that it may be a potential breast cancer chemopreventive agent. We first assessed the ability of ospemifene, compared to tamoxifen and raloxifene, to prevent dimethylbenzanthracene (DMBA)-induced mammary tumors in female Sencar mice. Ospemifene (N = 18), tamoxifen (N = 20) and raloxifene (N = 17), each dosed at 50 mg/kg, were administered daily by oral gavage, in combination with 20 microg DMBA for the first 6 weeks. Control mice (N = 21) received vehicle plus DMBA only for the first 6 weeks. Daily treatment then continued for 37 weeks. As hypothesized, ospemifene greatly reduced the incidence of mammary carcinomas compared to control mice (p = 0.003), similar to tamoxifen (p = 0.0004); however, in the raloxifene group, no significant effect was seen in mammary tumor prevention (p = 0.20). A follow-up study comparing ospemifene (N = 20) to tamoxifen (N = 20) in the same model was then performed to confirm the results of the first study. The results of the follow-up study, which extended the treatment to 52 weeks, confirmed the results of our previous study, with ospemifene (p = 0.01) and tamoxifen (p = 0.004) significantly decreasing mammary carcinomas compared to controls. The results of these two studies suggest that women taking ospemifene for osteoporosis and/or urogenital atrophy may further benefit from ospemifene's breast cancer chemopreventive effects.

Ospemifene inhibits the growth of dimethylbenzanthracene-induced mammary tumors in Sencar mice.

Ductal carcinoma in situ (DCIS) is a noninvasive premalignant lesion and is considered a precursor to invasive carcinoma. DCIS accounts for nearly 20% of newly diagnosed breast cancer, but the lack of experimentally amenable in vivo DCIS models hinders the development of treatment strategies. Here, we demonstrate the utility of a mouse transplantation model of DCIS for chemoprevention studies using selective estrogen receptor modulators (SERMs). This model consists of a set of serially transplanted lines of genetically engineered mouse mammary intraepithelial neoplasia (MIN) outgrowth (MIN-O) tissue that have stable characteristics. We studied the ovarian-hormone-responsiveness of one of the lines with a particular focus on the effects of two related SERMs, tamoxifen and ospemifene.

Selective estrogen receptor modulators inhibit growth and progression of premalignant lesions in a mouse model of ductal carcinoma in situ.

The potential of American ginseng (AG) ( Panax quinquefolium), a commonly used herbal remedy believed to have anticarcinogenic effects, to prevent the development of mammary tumors was evaluated in a mouse model of dimethylbenzanthracene (DMBA)-induced mammary carcinoma. Ginsenosides, believed to be the active components of ginseng and that have a chemical structure similar to estradiol, have previously been shown to possess phytoestrogen-like qualities similar to the soy isoflavone genistein. The effects of AG, administered as powdered root, were compared to the selective estrogen receptor modulators tamoxifen and ospemifene. Eighty-three female SENCAR mice were divided into four treatment groups: control (N = 23), AG (N = 20), ospemifene (N = 20), and tamoxifen (N = 20). American ginseng, ospemifene, and tamoxifen were administered at a dose of 50 mg/kg/day orally by gavage, with the control mice receiving vehicle only. For the first 6 weeks, all mice received 20 microg/day DMBA in combination with their respective treatments. DMBA was then withdrawn, and daily treatments continued for a total of approximately 52 weeks. As expected, ospemifene (p = 0.01) and tamoxifen (p = 0.004) significantly reduced the incidence of mammary tumors compared to the control mice, which had a mammary tumor incidence of approximately 57%. The incidence of mammary carcinomas in the AG group was 40%, a reduction of approximately 29% compared to control. These results suggest that AG may still have the potential to prevent the development of mammary tumors in a chemically induced breast cancer mouse model, although the present study showed no significant difference between control and AG-treated mice.

Ineffectiveness of American ginseng in the prevention of dimethylbenzanthracene-induced mammary tumors in mice.

Ospemifene (Ophena) is a new selective oestrogen receptor modulator currently in phase III clinical development for treatment of post-menopausal vulvar and vaginal atrophy. In the present study, we examined the pharmacokinetics, toxicity, and DNA adduct forming potential of ospemifene in the liver and endometrium of rhesus macaques following single and subchronic dosing schedules to better understand the potential toxicologic effects of ospemifene. During single weekly dosing, six macaques were administered 35 mg/kg/week ospemifene orally for 3 weeks. Pharmacokinetics, haematologic toxicity, uterotrophic effects and serum cholesterol levels were monitored. Additionally, two animals were subchronically dosed with 60 mg ospemifene for 9 weeks, followed by 12 mg/day for 3 weeks. Serum cholesterol and pharmacokinetics were monitored, and serial liver and endometrial biopsies were collected during and after treatment to evaluate DNA adduct formation. Following single weekly dosing, no significant haematologic toxicities or uterotrophic effects associated with ospemifene were observed. Peak absorption was 4-5 hr, and the elimination half-life was approximately 22 hr. Serum low-density lipoprotein and triglyceride levels trended lower while no other effects on serum lipids were observed. Subchronic dosing resulted in no haematologic toxicity, a lowering of low-density lipoprotein and triglyceride levels, and an increase in high-density lipoprotein levels that were reversed following cessation of dosing. No clinically relevant uterine or endometrial effects were observed, and no DNA adducts were detected in the liver or endometrial biopsies. The results of our pilot study show that ospemifene may lack genotoxic and toxic effects while having a favourable pharmacokinetic profile.

Pharmacologic effects of ospemifene in rhesus macaques: a pilot study.

Ospemifene, a new drug indicated for the treatment of vulvovaginal atrophy, has completed phase III clinical trials. A condition affecting millions of women worldwide, vulvovaginal atrophy has long been treated with estrogen therapy. Estrogen treatment carries with it risks of thromboembolism, endometrial proliferative effects, and breast cancer promotion. In this study, we test the effects of three dosing levels of ospemifene in both the prevention and treatment of breast cancer in the MTag.Tg mouse model.

Ospemifene and 4-hydroxyospemifene effectively prevent and treat breast cancer in the MTag.Tg transgenic mouse model.

In this study, we examine the immunomodulatory effects and antitumor activity of tamoxifen and letrozole when combined with the human epithelial mucin (hMUC1)-specific vaccine, L-BLP25, in the hMUC1-expressing mammary tumor (MMT) mouse model.

L-BLP25 vaccine plus letrozole induces a TH1 immune response and has additive antitumor activity in MUC1-expressing mammary tumors in mice.

We have recently reported immunomodulatory effects for tamoxifen and letrozole on the L-BLP25 (Stimuvax(®))-induced immune response in a MUC1-expressing breast cancer mouse model. While neither tamoxifen nor letrozole appeared to interfere with the Th1-polarized cytokine response induced by L-BLP25, only letrozole increased the survival advantage of L-BLP25.

L-BLP25 vaccine plus letrozole for breast cancer: Is translation possible?

The incidence and severity of vulvovaginal atrophy (VVA) in postmenopausal breast cancer patients has a significant impact on quality of life. While the etiology of VVA is primarily related to low estrogen levels seen in menopause, women with breast cancer have an added risk of VVA induced by a combination of chemotherapy, hormonal therapy, and menopause. Ospemifene is a new, non-hormonal selective estrogen receptor modulator (SERM) triphenylethylene derivative that is effective in treating VVA in postmenopausal women. Although other SERMs have antagonistic effects on the vagina, ospemifene exerts an estrogen-like effect on the vaginal epithelium. This review will focus on data demonstrating the antiestrogenic activity of ospemifene in several unique breast cancer animal models, and the implications for utilizing ospemifene in patients with breast cancer suffering from VVA. Additional research addressing the expanded use of ospemifene in breast cancer patients is also warranted.

Ospemifene, vulvovaginal atrophy, and breast cancer.

BACKGROUND: L-BLP25 antigen-specific cancer immunotherapeutic agent is currently in phase III clinical trials for non-small cell lung cancer. Using a novel human MUC1 transgenic (hMUC1.Tg) lung cancer mouse model, we evaluated effects of L-BLP25 combined with low-dose cyclophosphamide (CPA) pretreatment on Th1/Th2 cytokine production and antitumor activity. METHODS: A chemically-induced lung tumor model was developed in hMUC1.Tg C57BL/6 mice by administering 10 weekly 0.75-mg/g doses of the chemical carcinogen urethane by intraperitoneal injection. Serum cytokines associated with Th1/Th2 polarization and inflammation were measured by multiplex cytokine assay during tumorigenesis. Antitumor activity of L-BLP25 (10 mug) with CPA (100 mg/kg) pretreatment was evaluated following either one or two eight-week cycles of treatment by preparing lung whole mounts and counting tumor foci, and assessing IFN-gamma production by ELISpot assay. RESULTS: During the carcinogenesis phase, no detectable Th1- or Th2-associated cytokine responses were observed, but levels of pro-inflammatory cytokines were increased with distinctive kinetics. A single cycle of L-BLP25 consisting of eight weekly doses was ineffective, whereas adding a second cycle given during tumor progression showed a significant reduction in the incidence of tumor foci. Administering two cycles of L-BLP25 induced Th1 cytokines IL-12, IL-2 and IFNgamma at 24 h after the last dose, while Th2 and inflammatory cytokines were elevated to a lesser extent. CONCLUSIONS: Urethane-induced lung tumors in hMUC1.Tg mice can be used as a model to assess the efficacy of the MUC1 antigen-specific cancer immunotherapeutic agent L-BLP25. The results indicate that the antitumor response to L-BLP25 requires at least two cycles and pre-treatment with CPA. In addition, monitoring pro-inflammatory serum cytokines may be useful as a biomarker of L-BLP25 response. Taken together, the preclinical lung tumor model can be utilized for determining effective combinations of L-BLP25 with chemotherapy and/or other immunotherapies.

Antitumor effects of L-BLP25 Antigen-Specific tumor immunotherapy in a novel human MUC1 transgenic lung cancer mouse model.

Ospemifene is a selective estrogen receptor modulator (SERM), or estrogen receptor agonist/antagonist, that was recently approved by the US Food and Drug Administration for the treatment of dyspareunia associated with vulvar and vaginal atrophy, a chronic condition that affects up to 60% of postmenopausal women. Ospemifene is the first and only nonestrogen compound approved for this indication. Compared with other approved SERMs, such as tamoxifen, toremifene, bazedoxifene, and raloxifene, the estrogen-like effects of ospemifene in the vaginal epithelium are unique. This review first discusses the rationale for developing ospemifene, including its mechanism of action, and then focuses on the clinical development of ospemifene for the treatment of dyspareunia associated with vulvar and vaginal atrophy. Included are discussions of the effects of ospemifene on the endometrium, serum lipids, coagulation markers, bone, and breast cancer. In conclusion, ospemifene is a SERM with a unique estrogen agonist/antagonist tissue profile that was recently approved in the US for the treatment of dyspareunia associated with vulvar and vaginal atrophy in postmenopausal women. Ospemifene warrants further clinical investigation for the treatment and prevention of osteoporosis and breast cancer.

Gregory T. Wurz

Department of Internal Medicine,
Division of Hematology and Oncology,
Department of Internal Medicine, Division of Hematology and Oncology

University of California, Davis

Induction of Invasive Transitional Cell Bladder Carcinoma in Immune Intact Human MUC1 Transgenic Mice: A Model for Immunotherapy Development

Gregory T. Wurz

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Internal Medicine,Division of Hematology and Oncology,Department of Internal Medicine, Division of Hematology and Oncology

University of California, Davis

Induction of Invasive Transitional Cell Bladder Carcinoma in Immune Intact Human MUC1 Transgenic Mice: A Model for Immunotherapy Development

Department of Internal Medicine,
Division of Hematology and Oncology,
Department of Internal Medicine, Division of Hematology and Oncology