SERMs in chemoprevention of breast cancer

Switching from Aromatase Inhibitors to Dual Targeting Flavonoid-Based Compounds for Breast Cancer Treatment

Despite the significant outcomes attained by scientific research, breast cancer (BC) still represents the second leading cause of death in women. Estrogen receptor-positive (ER+) BC accounts for the majority of diagnosed BCs, highlighting the disruption of estrogenic signalling as target for first-line treatment. This goal is presently pursued by inhibiting aromatase (AR) enzyme or by modulating Estrogen Receptor (ER) α. An appealing strategy for fighting BC and reducing side effects and resistance issues may lie in the design of multifunctional compounds able to simultaneously target AR and ER. In this paper, previously reported flavonoid-related potent AR inhibitors were suitably modified with the aim of also targeting ERα. As a result, homoisoflavone derivatives 3b and 4a emerged as well-balanced submicromolar dual acting compounds. An extensive computational study was then performed to gain insights into the interactions the best compounds established with the two targets. This study highlighted the feasibility of switching from single-target compounds to balanced dual-acting agents, confirming that a multi-target approach may represent a valid therapeutic option to counteract ER+ BC. The homoisoflavone core emerged as a valuable natural-inspired scaffold for the design of multifunctional compounds.

Molecular Mechanisms of Anti-Estrogen Therapy Resistance and Novel Targeted Therapies

Breast cancer (BC) is the most commonly diagnosed cancer in women, constituting one-third of all cancers in women, and it is the second leading cause of cancer-related deaths in the United States. Anti-estrogen therapies, such as selective estrogen receptor modulators, significantly improve survival in estrogen receptor-positive (ER+) BC patients, which represents about 70% of cases. However, about 60% of patients inevitably experience intrinsic or acquired resistance to anti-estrogen therapies, representing a major clinical problem that leads to relapse, metastasis, and patient deaths. The resistance mechanisms involve mutations of the direct targets of anti-estrogen therapies, compensatory survival pathways, as well as alterations in the expression of non-coding RNAs (e.g., microRNA) that regulate the activity of survival and signaling pathways. Although cyclin-dependent kinase 4/6 and phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) inhibitors have significantly improved survival, the efficacy of these therapies alone and in combination with anti-estrogen therapy for advanced ER+ BC, are not curative in advanced and metastatic disease. Therefore, understanding the molecular mechanisms causing treatment resistance is critical for developing highly effective therapies and improving patient survival. This review focuses on the key mechanisms that contribute to anti-estrogen therapy resistance and potential new treatment strategies alone and in combination with anti-estrogen drugs to improve the survival of BC patients.

Neurological complications of chemotherapy to the central nervous system

One of the most common complications of chemotherapeutic drugs is toxicity to the central nervous system (CNS). This toxicity can manifest in many ways, including encephalopathy syndromes and confusional states, seizure activity, headache, cerebrovascular complications and stroke, visual loss, cerebellar dysfunction, and spinal cord damage with myelopathy. For many drugs, the toxicity is related to route of administration and cumulative dose, and can vary from brief, transient episodes to more severe, chronic sequelae. However, the neurotoxicity can be idiosyncratic and unpredictable in some cases. Among the antimetabolite drugs, methotrexate, 5-fluorouracil, and cytosine arabinoside are most likely to cause CNS toxicity. Of the alkylating agent chemotherapeutic drugs, the nitrosoureas (e.g., BCNU) and cisplatin most frequently cause toxicity to the CNS, especially when given via the intra-arterial route. Ifosfamide is also likely to cause neurotoxicity at high intravenous doses. Other alkylating agents, such as busulfan, cyclophosphamide, procarbazine, and temozolomide, are better tolerated by the CNS at moderate doses. The retinoid drugs are known to cause severe headaches at high doses. l-Asparaginase can induce an encephalopathy syndrome, as well as cerebrovascular complications such as stroke.

Interaction of current cancer treatments and the immune system: implications for breast cancer therapeutics

Early diagnosis and treatment of breast cancer may account for the current improvement in the mortality of breast cancer. However, achieving a complete 'cure' is the holy grail of cancer medicine and, in many cases, cancer patients still succumb to their ultimate fate. There is therefore a need to devise innovative therapies to overcome this problem. To this end, many emerging therapies utilizing the immune system to eradicate the residues of disease have been described in the preclinical and clinical arenas. However, there is very little work examining the impact of immunotherapy on the existing natural immunity. The relationship between antitumor immunity, in the form of immunotherapy (either passive or active), and current strategies of treatment also needs to be explored. If we are to improve the success of cancer treatment, we must understand how current therapies interact with the immune system and with the emerging immunotherapies. For breast-cancer treatment to be successful, therapeutics should be tailored towards antitumor immunity; they should also avoid tumor-specific tolerance. The sources of information used to prepare this paper were obtained through published work on Pubmed/Medline and materials published on the US/UK governmental agencies' websites.

Structure–Activity Relationships for a Family of Benzothiophene Selective Estrogen Receptor Modulators Including Raloxifene and Arzoxifene

The search for the "ideal" selective estrogen receptor modulator (SERM) as a substitute for hormone replacement therapy (HRT) or use in cancer chemoprevention has focused on optimization of estrogen receptor (ER) ligand binding. Based on the clinical and preclinical benzothiophene SERMs, raloxifene and arzoxifene, a family of SERMs has been developed to modulate activity and oxidative lability. Antiestrogenic potency measured in human endometrial and breast cancer cells, and ER ligand binding data were correlated and seen to provide a guide to SERM design only when viewed in toto. The in vitro studies were extended to the juvenile rat model, in which the desired antiestrogenic profile and putative cardiovascular benefits of SERMs were observed.

Delayed and persistent ERK1/2 activation is required for 4-hydroxytamoxifen-induced cell death

Tamoxifen (Tam), and its active metabolite, 4-hydroxytamoxifen (OHT), compete with estrogens for binding to the estrogen receptor (ER). Tam and OHT can also induce ER-dependent apoptosis of cancer cells. 10-100nM OHT induces ER-dependent apoptosis in approximately 3 days. Using HeLaER6 cells, we examined the role of OHT activation of signal transduction pathways in OHT-ER-mediated apoptosis. OHT-ER activated the p38, JNK and ERK1/2 pathways. Inhibition of p38 activation with SB203580, or RNAi-knockdown of p38alpha, moderately reduced OHT-ER mediated cell death. A JNK inhibitor partly reduced cell death. Surprisingly, the MEK1/2 inhibitor, PD98059, completely blocked OHT-ER induced apoptosis. EGF, an ERK1/2 activator, enhanced OHT-induced apoptosis. OHT induced a delayed and persistent phosphorylation of ERK1/2 that persisted for >80h. Addition of PD98059 as late as 24h after OHT largely blocked OHT-ER mediated apoptosis. The antagonist, ICI 182,780, blocked both the long-term OHT-mediated phosphorylation of ERK1/2 and OHT-induced apoptosis. Our data suggests that the p38 and JNK pathways, which often play a central role in apoptosis, have only a limited role in OHT-ER-mediated cell death. Although rapid activation of the ERK1/2 pathway is often associated with cell growth, persistent activation of the ERK1/2 pathway is essential for OHT-ER induced cell death.

Molecular screening for breast cancer prevention, early detection, and treatment planning: combining biomarkers from DNA, RNA, and protein

The completion of the human genome project, along with the ancillary technologies derived from this effort, provides the ability to comprehensively analyze patient tumors as well as the individual patient's own genetic make-up at the DNA, RNA, and protein level. As a result, novel molecular screening techniques have the potential to push the boundaries of detection to even smaller tumors and also to allow accurate risk assessment, cancer prevention, and treatment planning in individual women. This review focuses on advances over the past 2 years in the use of molecular signatures and circulating tumor cells for early breast cancer detection and for prediction of response to therapy.

Skin cancer chemoprevention with systemic retinoids: an adjunct in the management of selected high-risk patients

Systemic retinoids (isotretinoin, etretinate, and acitretin) have been shown to be effective chemotherapeutic agents in studies of patients with xeroderma pigmentosum, the nevoid basal cell carcinoma syndrome, and recipients of organ or bone marrow transplantation. In addition, patients who do not have these disorders but who are actively developing large numbers of new skin cancers may also benefit from this approach. All patients developing large numbers of skin cancers need rigorous UV protection and frequent dermatologic examinations. Although isotretinoin and acitretin share overlapping toxicities, there are differences that may affect drug choice. Because low doses may be effective, there are advantages to beginning treatment at a low dose, and subsequently, increasing dose if necessary, based on patient response. Laboratory monitoring including pregnancy testing should be performed before and during treatment. Long-term toxicity, primarily involving the skeletal system, can be monitored with imaging studies.

Chemoprevention of breast cancer among Asian women--its perspective and problems

Chemoprevention of breast cancer employing tamoxifen and others has been demonstrated to be effective in reducing the frequency of developing breast malignancy in Western countries. In Asian countries, the frequency of breast cancer as well as its premalignant lesions has recently increased. Therefore, the possible chemoprevention may benefit those women with potential high risks of developing breast cancer and with premalignant lesions. However, the details of these findings of chemoprevention in Western countries have not been available for women with Asian descendant. In addition, risk factors of developing breast cancer in healthy women have not been established in Asian countries compared to Western countries with relative paucity of familial breast cancer cases. Thus, possible chemoprevention of breast cancer in Asian countries may be targeted toward those with established premalignant breast lesions such as ductal carcinoma in situ and/or atypical ductal hyperplasia. However, due to their recent increment of their incidence, biological and/or clinical features of these premalignant breast lesions have not been extensively characterized in Asian women and further investigations are required for wide spread chemoprevention.

Three-dimensional models of non-steroidal ligands: a comparative molecular field analysis

The estrogen receptor, ER, is an important biological target whose inhibition is known to be therapeutically relevant in the treatment of postmenopausal osteoporosis. In the present study, two prediction methods (CoMFA and GRIND (Almond)) were used to describe the binding modes of a set of estrogen receptor ligands. The critical alignment step presented in CoMFA was solved by using the information of the molecular descriptors space generated by grid-independent descriptors (GRIND). Then, it was possible to build robust and high predictive models based on the alignment-independent model. Since the structure of estrogen receptor is solved, the results of the present 3D QSAR models, given by the PLS maps based on molecular interaction fields (MIF) were compared to ligand-binding ER domains and showed good agreement.

Development of novel cancer chemopreventive agents in Europe--neglected Cinderella or rising phoenix? A critical commentary. ESF Workshop on Cancer Chemoprevention, DKFZ, Heidelberg, September 18-20, 2005

Agents that prevent cancer, delay its onset, or revert premalignant conditions could have dramatic beneficial impacts on human health. Although there is an urgent need to develop cancer chemopreventive agents, researchers in the field suspect that this area of scientific endeavour in Europe leads a Cinderella existence, both in terms of perception of importance and research funding. In order to review current activities in this prevention field and to seek a consensus position, an exploratory workshop was held in September 2005 at the German Cancer Research Center (DKFZ) in Heidelberg, Germany, sponsored mainly by the European Science Foundation (ESF), and also supported by the European Association for Cancer Research (EACR) and the German Cancer Society (DKG). The 35 experts from European countries and the United States of America assessed state-of-the-art cancer chemoprevention research in Europe. The aims that the workshop organizers had pre-defined were: i) assessment of the usefulness of animal models for agent identification; ii) review of ongoing preclinical and clinical work on novel agents; iii) discussion of potential biomarkers predictive for cancer preventive efficacy; and finally iv) the potential role that European pharmaceutical industries could play in furthering chemopreventive agent development. Overall the workshop aimed at raising awareness among European clinical and laboratory researchers of the importance of the development of novel, efficacious and safe cancer preventive agents.