Thesis (M.S.)--Medical University of Ohio, 2005. / "In partial fulfillment of the requirements for the degree of Master of Science in Biomedical Sciences." Major advisor: Brian G. Rowan. Includes abstract. Document formatted into pages: iv, 57 p. Title from title page of PDF document. Bibliography: pages 49-56.

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Breast cancer (BC) is the second most common malignancy in the world and it accounts for 15% of female deaths due to cancer every year. The development of these tumours is regulated by the activities of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Tamoxifen (TAM) is frequently used to treat patients with ER+ BC; however, a recurring problem is the development of resistance and the mechanisms leading up to this event remain unclear. FAM84B is reported to be associated with the development of various cancers such as esophageal squamous cell carcinoma and prostate cancer. The function of the protein is unknown; however, insight towards its mechanism of action has been made through the discovery of its structural similarities with the H-Ras-like suppressor (HRASLS) subfamily of enzymes. We hypothesize that FAM84B upregulation enhances BC tumorigenesis and facilitates the development of TAM resistance in this disease. We observed that both overexpression and knockdown of FAM84B had little effects on cell proliferation; however, the latter reduced the ability of MCF7 cells to form isolated colonies. We performed similar analyses using a FAM84B mutant with deletion of its HRASLS domain and we observed that MCF7 cells expressing this protein showed higher rates of cell proliferation and increased ability to form isolated colonies compared to cells with baseline expression of wild-type FAM84B. These results suggest that FAM84B regulates BC cell proliferation through a complex manner. An analysis of patient-derived BC tissue revealed that FAM84B expression was associated with BC at early stages than later stages, which suggests a possible role of the protein in directing events associated with the early developmental stages of the disease. Additional analyses demonstrated that overexpression and knockdown of FAM84B had little impact on TAM-derived cytotoxicity of MCF7 cells. We observed higher expression of FAM84B in TAM-resistant MCF7 cells in comparison to TAM-sensitive cells, while TAM-resistant and TAM-sensitive xenograft tumours showed similar levels of FAM84B expression. This suggests that the contributions of FAM84B in BC tumorigenesis and resistance to TAM are complex; alternatively, FAM84B may not play a major role in either events. Future studies will be needed to clarify the effects of FAM84B on BC tumorigenesis and progression. / Dissertation / Master of Science (MSc) / Breast cancer (BC) is the second most common malignancy in the world and it accounts for 15% of female deaths due to cancer every year. Although hormonal therapy with tamoxifen (TAM) is a commonly used treatment for the disease, a recurring problem is that tumours eventually develop resistance to the drug. We are interested in investigating the role of FAM84B in BC tumorigenesis and the development of TAM resistance in these tumours. FAM84B has been shown to have higher expression in esophageal squamous cell carcinoma than in normal tissue and the protein was associated with increased tumour growth. Similar studies in prostate cancer have shown that FAM84B is associated with progression of the disease. The results of our analyses suggest that FAM84B may have a possible role in promoting events associated with enhancing the viability of MCF7 cells, leading to increased rates of growth and division. In addition, FAM84B may also function to direct events associated with the early developmental stages of BC. We did not, however, observe any impact of altered FAM84B expression on the development of TAM resistance in BC. Further research involving improved in vitro and in vivo studies, along with an examination of FAM84B’s impact on various oncogenic molecular signalling pathways, will help improve our understanding of the protein’s role in BC tumorigenesis.

nÃo hà / O cÃncer de mama foi descrito hà muitos anos e documentado, pela primeira vez, por Imhotep, mÃdico, astrÃlogo e arquiteto egÃpcio, nascido em 2.650 antes de Cristo (a.C.) que recomendava Ãquela Ãpoca, como tratamento, a cauterizaÃÃo do tecido doente. Tamoxifeno à o fÃrmaco mais prescrito no tratamento do cÃncer de mama. Sua utilizaÃÃo à principalmente na modalidade adjuvante, em pacientes prà ou pÃs menopausadas, receptor de estrÃgeno e/ou progesterona positivos. à tambÃm utilizado no tratamento da doenÃa localmente avanÃada e metastÃtica e em menor proporÃÃo nas pacientes com contra-indicaÃÃo formal de cirurgia ou que se recusam a se submeter a esta modalidade de tratamento. Na neo-adjuvÃncia à utilizada apenas em ensaios clÃnicos. O tamoxifeno tambÃm diminui, na adjuvÃncia por cinco anos, a probabilidade de recidiva em 47% e de morte por cÃncer de mama em 26% e os dois principais efeitos colaterais, apesar de raros, sÃo aumento da prevalÃncia de cÃncer de endomÃtrio e de fenÃmenos tromboembÃlicos. Este estudo teve como objetivo principal avaliar as pacientes portadoras de cÃncer de mama, no Instituto do CÃncer do CearÃ, tratadas com tamoxifeno de forma adjuvante, no perÃodo de janeiro de 1993 a 1996, com relaÃÃo aos principais benefÃcios e efeitos colaterais, bem como anÃlise de sobrevivÃncia. ProntuÃrios de setecentos e quarenta e duas pacientes foram analisados no que diz respeito aos dados sÃcio- demogrÃficos, idade, status menopausal, estadiamento clÃnico e patolÃgico, dosagem de receptores de estrÃgeno e progesterona, casos de cÃncer de endomÃtrio, principais sÃtios de metÃstases, modalidade de tratamento cirÃrgico, radioterÃpico e quimioterÃpico, causas de Ãbito, tipo histolÃgico, status dos linfonodos axilares e anÃlise de sobrevivÃncia de acordo com o estadiamento. Concluiu-se que a maioria dos dados estÃo de acordo com a literatura e que o prejuÃzo da anÃlise foi resultante da qualidade dos registros realizados nos prontuÃrios, devendo cada vez mais os mÃdicos serem estimulados a documentar, de forma clara e legÃvel, o maior nÃmero de informaÃÃes possÃveis, nÃo apenas as positivas, mas todas aquelas que, mais freqÃentemente, possam ter relaÃÃo com a utilizaÃÃo de qualquer medicamento prescrito. / O cÃncer de mama foi descrito hà muitos anos e documentado, pela primeira vez, por Imhotep, mÃdico, astrÃlogo e arquiteto egÃpcio, nascido em 2.650 antes de Cristo (a.C.) que recomendava Ãquela Ãpoca, como tratamento, a cauterizaÃÃo do tecido doente. Tamoxifeno à o fÃrmaco mais prescrito no tratamento do cÃncer de mama. Sua utilizaÃÃo à principalmente na modalidade adjuvante, em pacientes prà ou pÃs menopausadas, receptor de estrÃgeno e/ou progesterona positivos. à tambÃm utilizado no tratamento da doenÃa localmente avanÃada e metastÃtica e em menor proporÃÃo nas pacientes com contra-indicaÃÃo formal de cirurgia ou que se recusam a se submeter a esta modalidade de tratamento. Na neo-adjuvÃncia à utilizada apenas em ensaios clÃnicos. O tamoxifeno tambÃm diminui, na adjuvÃncia por cinco anos, a probabilidade de recidiva em 47% e de morte por cÃncer de mama em 26% e os dois principais efeitos colaterais, apesar de raros, sÃo aumento da prevalÃncia de cÃncer de endomÃtrio e de fenÃmenos tromboembÃlicos. Este estudo teve como objetivo principal avaliar as pacientes portadoras de cÃncer de mama, no Instituto do CÃncer do CearÃ, tratadas com tamoxifeno de forma adjuvante, no perÃodo de janeiro de 1993 a 1996, com relaÃÃo aos principais benefÃcios e efeitos colaterais, bem como anÃlise de sobrevivÃncia. ProntuÃrios de setecentos e quarenta e duas pacientes foram analisados no que diz respeito aos dados sÃcio- demogrÃficos, idade, status menopausal, estadiamento clÃnico e patolÃgico, dosagem de receptores de estrÃgeno e progesterona, casos de cÃncer de endomÃtrio, principais sÃtios de metÃstases, modalidade de tratamento cirÃrgico, radioterÃpico e quimioterÃpico, causas de Ãbito, tipo histolÃgico, status dos linfonodos axilares e anÃlise de sobrevivÃncia de acordo com o estadiamento. Concluiu-se que a maioria dos dados estÃo de acordo com a literatura e que o prejuÃzo da anÃlise foi resultante da qualidade dos registros realizados nos prontuÃrios, devendo cada vez mais os mÃdicos serem estimulados a documentar, de forma clara e legÃvel, o maior nÃmero de informaÃÃes possÃveis, nÃo apenas as positivas, mas todas aquelas que, mais freqÃentemente, possam ter relaÃÃo com a utilizaÃÃo de qualquer medicamento prescrito. / Breast cancer is a disease that was described many years ago and has been documented, for the first time, by Imhotep, physician, astrologer and Egyptian architect, born in 2.650 before Christ (b.C.), who recommended, at that time, as a way of treatment, cauterization of the diseased tissue. Tamoxifen is the drug more prescribed in the treatment of breast cancer. Itâs use is mainly in the adjuvant modality, in pre or post menopaused patients positive estrogen and/or progesteron receptors. Itâs used in the treatment of locally advanced and metastatic disease and in smaller proportion in patients with formal contraindication of surgery or that refuse to submit this treatment modality. In the neoadjuvancy it is just used in clinical research. The tamoxifen also reduces in the adjuvant modality during five years, the probability of recurrence in 47% and deaths caused by breast cancer in 26% and the two main side effects, in spite of rare, are the increase of the prevalence of endometrial cancer and of thromboembolic phenomenas. This study had as main objective to evaluate the patients, breast cancer bearers, in the Institute of Cancer of CearÃ, treated with tamoxifen in the adjuvant form in the period of 1993 to 1996 regarding the main benefits and side effects, as well as survival analysis. Seven hundred forty-two patientsâprontuaries were analyzed in respect to the demographic datas, age, menopausal status, clinical and pathological staging, dosage of estrogen and/or progesterone receptors, cases of endometrial cancer, main local metastasis, modality of surgical treatment, radiotherapy and chemotherapy, death causes, histological type, status of the axillary lymph nodes and survival analysis in agreement with the staging. We concluded that most of the data is in agreement with the literature and that the demage of the analysis was resulting from the quality accomplished found in the prontuaries. Also, doctors should be more and more stimulated to document, in a clear and readable way, the largest number of possible information, not just the positive ones, but all those that more frequently can have relationships with the use of any prescribed medicine. / Breast cancer is a disease that was described many years ago and has been documented, for the first time, by Imhotep, physician, astrologer and Egyptian architect, born in 2.650 before Christ (b.C.), who recommended, at that time, as a way of treatment, cauterization of the diseased tissue. Tamoxifen is the drug more prescribed in the treatment of breast cancer. Itâs use is mainly in the adjuvant modality, in pre or post menopaused patients positive estrogen and/or progesteron receptors. Itâs used in the treatment of locally advanced and metastatic disease and in smaller proportion in patients with formal contraindication of surgery or that refuse to submit this treatment modality. In the neoadjuvancy it is just used in clinical research. The tamoxifen also reduces in the adjuvant modality during five years, the probability of recurrence in 47% and deaths caused by breast cancer in 26% and the two main side effects, in spite of rare, are the increase of the prevalence of endometrial cancer and of thromboembolic phenomenas. This study had as main objective to evaluate the patients, breast cancer bearers, in the Institute of Cancer of CearÃ, treated with tamoxifen in the adjuvant form in the period of 1993 to 1996 regarding the main benefits and side effects, as well as survival analysis. Seven hundred forty-two patientsâprontuaries were analyzed in respect to the demographic datas, age, menopausal status, clinical and pathological staging, dosage of estrogen and/or progesterone receptors, cases of endometrial cancer, main local metastasis, modality of surgical treatment, radiotherapy and chemotherapy, death causes, histological type, status of the axillary lymph nodes and survival analysis in agreement with the staging. We concluded that most of the data is in agreement with the literature and that the demage of the analysis was resulting from the quality accomplished found in the prontuaries. Also, doctors should be more and more stimulated to document, in a clear and readable way, the largest number of possible information, not just the positive ones, but all those that more frequently can have relationships with the use of any prescribed medicine.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Resistance to antiestrogen therapy remains a significant problem in breast cancer. Low expression of inhibitor of growth 4 (ING4) in primary tumors has been correlated with increased rates of recurrence in estrogen receptor-positive (ER+) breast cancer patients, suggesting a role for ING4 in ER signaling. This study provides evidence that ING4 inhibits ER activity. ING4 overexpression increased the sensitivity of T47D and MCF7 ER+ breast cancer cells to hormone deprivation. ING4 attenuated maximal estrogen-dependent cell growth without affecting the dose-response of estrogen. These results indicated that ING4 functions as a noncompetitive inhibitor of estrogen signaling and may inhibit estrogen-independent ER activity. Supportive of this, treatment with fulvestrant but not tamoxifen rendered T47D cells sensitive to hormone deprivation as did ING4 overexpression. ING4 did not affect nuclear ER alpha protein expression, but repressed selective ER-target gene transcription. Taken together, these results demonstrated that ING4 inhibited estrogen-independent ER activity, suggesting that ING4-low breast tumors recur faster due to estrogen-independent ER activity that renders tamoxifen less effective. This study puts forth fulvestrant as a proposed therapy choice for patients with ING4-low ER+ breast tumors.

Objectives: A decrease in Ki67 during neoadjuvant therapy predicts response to tamoxifen. Previous trials have shown a decreased Ki67 in breast tumors with as little as two or more weeks of preoperative tamoxifen. Shortening the preoperative treatment time in window of opportunity clinical trials makes these trials more attractive to women. POWERPIINC examined the effect of 7 days of preoperative tamoxifen on breast tumor proliferation and patient symptoms. Methods: Women with untreated stage I/II, ER-positive, invasive breast cancer with no contraindications to tamoxifen were enrolled. Women received 20 mg of tamoxifen for 7 days up to the day of surgery. Proliferation was assessed by Ki67 immunohistochemistry before and after 7 days of tamoxifen. Symptoms and QOL were assessed by the FACT-ES and MENQOL. Adherence was measured by pill counts. Results: 52 women were enrolled, and 44 were evaluable for Ki67. The median age was 58.5 years, and the median tumor diameter was 1.2 cm. Most women (73%) were post-menopausal. Most tumors were PR positive (88%) and HER2-negative (92%). The Ki67 decreased by a geometric mean of 40% (95% CI 29%-63%), and 73% (95% CI 57%-85%) of women had tumors with decreased proliferation (p = 0.0001 by paired t-test). Adherence to taking tamoxifen during the preoperative period was 100%. Women reported minimal bother from psychosocial or physical symptoms at baseline or on the day of surgery. Conclusion: Seven days of tamoxifen showed a similar relative decrease in Ki67 as that reported for longer courses, was acceptable to women, and could be considered for window of opportunity studies.

Introdução: O câncer se tornou um grande problema de saúde pública mundial, sendo o câncer de mama o mais incidente em mulheres. A terapia endócrina com o tamoxifeno, um modulador seletivo do receptor de estrógeno (SERM), é aplicada em câncer de mama receptor de estrógeno (RE) positivo, porém, pacientes tratadas por um longo período podem desenvolver resistência ao medicamento. O tratamento padrão para o câncer de mama triplo negativo é a quimioterapia com antraciclinas e taxanos, individual ou em combinação com cirurgia e/ou radioterapia, porém muitos fatores devem ser considerados. Assim, aumenta a necessidade por novas estratégias terapêuticas para o tratamento do câncer de mama, especialmente para o fenótipo triplo-negativo e, consequentemente, abre-se uma grande área para a aplicação de produtos naturais, como o resveratrol. Estudos tem demonstrado que fitoquímicos, como o resvetatrol, podem ser usados em combinação com agentes quimioterapêuticos, aumentando sua eficácia e diminuindo sua toxicidade. Objetivos: Avaliar os efeitos citotóxicos do resveratrol e dos metabólitos do tamoxifeno (N-desmetiltamoxifeno e 4-hidroxitamoxifeno), em tratamentos isolados e em associação, na proliferação e apoptose de células de câncer de mama RE-positivo (MCF-7) e células de câncer de mama triplo negativo (MDA-MB-231). Materiais e Métodos: A avaliação dos efeitos citotóxicos de resveratrol e metabólitos do tamoxifeno na proliferação e apoptose das células de câncer de mama foi realizada a partir do Ensaio de Viabilidade Celular (método de análise colorimétrica utilizando o Metil Tiazol Tetrazolium - MTT), cálculo de Coeficiente de Interação entre Drogas (CID) para avaliar o grau de sinergia entre os tratamentos, marcação celular com anexina V e iodeto de propídeo, Hypotonic Fluorescent Solution e western-blot (caspase 3, 8 e 9). Resultados: O tratamento associado de resveratrol 165 ?M + desmetiltamoxifeno 30 ?M e resveratrol 165 ?M + hidroxitamoxifeno 40 ?M mostrou diminuir significativamente a viabilidade celular de MCF-7 e MDA-MB-231, quando comparado com o tratamento isolado de desmetiltamoxifeno 30 ?M e hidroxitamoxifeno 40 ?M, respectivamente. Os tratamentos associados também mostraram aumento de células MCF-7 e MDA-MB-231 marcadas com anexina V e iodeto de propídeo e aumento de núcleos hipodiplóides, porém, a maior ativação de caspase 3, 8 e 9 ocorreu apenas em MCF-7. Conclusões: Os resultados obtidos indicam que os tratamentos associados reduziram a viabilidade de células MCF-7 e MDA-MB-231 e induziram ativação de apoptose somente em MCF-7. Assim, sugere-se que a redução na viabilidade de MDA-MB-231 deve estar relacionada com mecanismos independentes de ativação de caspases. / Introduction: Cancer has become a major public health problem worldwide, with breast cancer being the most common in women. Endocrine therapy with tamoxifen, a selective estrogen receptor modulator (SERM), is used in estrogen receptor (ER)-positive breast cancer, but patients treated over a long period may develop resistance to the drug. The standard treatment for triple negative breast cancer is chemotherapy with anthracyclines and taxanes, either alone or in combination with surgery and / or radiotherapy, but many factors must be considered. Thus, there is a growing need for new therapeutic strategies for the treatment of breast cancer, especially for the triple-negative phenotype and, consequently, opens up a great area for the application of natural products, such as resveratrol. Studies have shown that phytochemicals, such as resvetatrol, can be used in combination with chemotherapeutic agents, increasing their efficacy and decreasing their toxicity. Objectives: To evaluate the cytotoxic effects of resveratrol and the metabolites of tamoxifen (N-desmetiltamoxifen and 4-hydroxytamoxifen) in isolated and combined treatments on the proliferation and apoptosis of ER-positive breast cancer cells (MCF-7) and cancer cells of triple negative breast (MDA-MB-231). Materials and methods: The evaluation of the cytotoxic effects of resveratrol and metabolites of tamoxifen on the proliferation and apoptosis of breast cancer cells was performed from the Cell Viability Assay (colorimetric analysis using Methyl Thiazole Tetrazolium - MTT), Coefficient of Drug Interaction (ICD) to assess the degree of synergy between treatments, cell marking with annexin V and propidium iodide, Hypotonic Fluorescent Solution and western blot (caspase 3, 8 e 9). Results: The associated treatment of resveratrol 165 ?M + desmethyltamoxifen 30 ?M and resveratrol 165 ?M + hydroxytamoxifen 40 ?M showed a significant decrease in the cellular viability of MCF-7 and MDA-MB-231 when compared to the isolated treatment of desmethyltamoxifen 30 ?M and hydroxytamoxifen 40 ?M, respectively. Associated treatments also showed increase of MCF-7 and MDA-MB-231 cells labeled with annexin V and propidium iodide and increase of hypodiploid nuclei, but the greater activation of caspase 3, 8 and 9 occurred only in MCF-7. Conclusions: The results indicate that the associated treatments reduced the viability of MCF-7 and MDA-MB-231 cells and induced activation of apoptosis only in MCF-7. Thus, it is suggested that the reduction in the viability of MDA-MB-231 should be related to independent mechanisms of caspase activation.

Resistance to endocrine treatments in oestrogen receptor positive (ER+) breast cancer (BC) significantly contribute to patient morbidity and mortality. ER+ BC constitute 60% of all breast cancers although there is considerable clinico-pathological diversity within this group. Breast cancer initiating cells (BCICs) are implicated in tumour relapse and metastasis and are postulated to drive resistance to standard anti-cancer therapies. However little is known about the sensitivity of BCICs to endocrine therapies. We assessed the effect of tamoxifen treatment and acquired tamoxifen resistance on BCIC frequency in vitro and in vivo using breast cancer cell lines and, importantly, patient derived samples of early and metastatic ER+ breast cancer. In ER+ breast cancer, BCICs may be prospectively enriched in vitro by selecting cells by CD44+/CD24lo/ESA+ phenotype or by mammosphere initiating capacity (MIC). However the gold standard assay to determine BCIC frequency is limiting dilution transplantation in vivo. In the past it has been historically difficult to generate xenograft models of ER+ breast cancer using patient samples. In this thesis, using a novel experimental technique, patient-derived xenografts (PDX) of early and metastatic ER+ BC were generated with almost 85% efficiency in NOD/SCID IL2gammaR-/- (NSG) mice. PDX expressed ER and were able to undergo serial in vivo passage, matching the phenotype of the tumour from which they were derived. In this work, two patterns of response to tamoxifen treatment were observed in ER+ cell lines, patient derived breast cancer samples and xenografts during BCIC assays in vitro and in vivo; Limited Sensitivity (LS) or Resistance (R). In the LS group there was no change or a significant diminution in BCIC frequency in the presence of tamoxifen. In the R group, a significant increase in BCIC frequency was observed in the presence of tamoxifen. Furthermore BCIC activity was shown be enhanced by the acquisition of tamoxifen resistance using cell line models. Cellular populations enriched for BCICs in ER+ cell lines were shown to express low levels of ER compared to non-BCICs. Finally Notch (gamma-secretase inhibitor) and EGFR (gefitinib) pathway inhibitors were tested alone or in combination with tamoxifen against a panel of established and novel cell lines and ER+ patient-derived breast cancer samples for anti-BCIC activity. Tamoxifen treatment can increase BCIC frequency in vitro assays of cell lines and patient-derived samples and in vivo using patient-derived xenografts of ER+ breast cancer. However phenotypic diversity of BCIC may be present within the ER+ BC population. A pharmaceutical strategy to effectively treat BCICs alongside standard endocrine therapy is necessary for the effective future treatment of ER+ breast cancer.

Although tamoxifen has been successfully utilized in the treatment and prevention of estrogen-dependent breast cancer for decades, its use is limited by its low incidence of endometrial cancer. The carcinogenic effects of tamoxifen are complex and may involve a combination of estrogen receptor-mediated hormonal effects as well as the metabolic activation of tamoxifen to reactive electrophiles that are genotoxic. Moreover, a significant population of patients develop clinical resistance to tamoxifen, which leads to breast cancer recurrence and a decrease in patient survival. Therefore, the goal of the current study was to examine the interactions of major metabolites of tamoxifen with the human cytosolic sulfotransferases hSULT2A1, hSULT1E1, and hSULT1A1*1. Changes in the catalytic activity of hSULT2A1 by tamoxifen metabolites may inhibit the formation of the genotoxic Α-sulfooxy tamoxifen intermediate catalyzed by this enzyme. Moreover, tamoxifen metabolites might interfere in the inactivation of hydroxysteroids catalyzed by hSULT2A1 as a part of the variable responses to tamoxifen therapy. Endoxifen was the most potent inhibitor of the hSULT2A1, which suggests that this metabolite may inhibit the role of hSULT2A1 in the metabolic pathway for genotoxicity that is seen with tamoxifen.N-desmethyltamoxifen (N-desTAM) was a substrate for the hSULT2A1, and the product of this reaction, N-desmethyltamoxifen sulfamate (N-desTAM-S), displayed greater inhibition of the enzyme than its unconjugated precursor. Thus, endoxifen, N-desTAM, and N-desTAM-S might serve protective roles in some tissues as they may inhibit the role of hSULT2A1 in the genotoxicity of tamoxifen. Metabolites of tamoxifen were then examined as inhibitors of hSULT1E1 and hSULT1A1*1 due to the roles of these enzymes in the inactivation of estrogens. Each of the metabolites studied were weak inhibitors of hSULT1E1; thus, endoxifen is not likely to promote increased estrogen signaling in breast tissue when administered as an independent breast cancer therapeutic agent in ongoing clinical trials. However, 4-hydroxytamoxifen (4-OHTAM) was a very potent inhibitor of hSULT1A1*1 when examined with estradiol as substrate. This suggests the potential for 4-OHTAM to interfere in estrogen metabolism in tissues where hSULT1A1*1 is expressed and hSULT1E1 is not. This information will be useful when interpreting the clinical trials of endoxifen and will aid in the design of related molecules