Cannabidiol as a Promising Adjuvant Therapy for Estrogen Receptor-Positive Breast Tumors: Unveiling Its Benefits with Aromatase Inhibitors.

BACKGROUND: Estrogen receptor-positive (ER+) breast cancer is the most diagnosed subtype, with aromatase inhibitors (AIs) being one of the therapeutic drug types used in the clinic. However, endocrine resistance may develop after prolonged treatment, and different approaches, such as combining endocrine and targeted therapies, have been applied. Recently, we demonstrated that cannabidiol (CBD) induces anti-tumor actions in ER+ breast cancer cells by targeting aromatase and ERs. Considering this, we studied, in vitro, whether CBD when combined with AIs could improve their effectiveness. METHODS: MCF-7aro cells were used and the effects on cell viability and on the modulation of specific targets were investigated. RESULTS: CBD when combined with anastrozole (Ana) and letrozole (Let) caused no beneficial effect in comparison to the isolated AIs. In contrast, when combined with the AI exemestane (Exe), CBD potentiated its pro-cell death effects, abolished its estrogen-like effect, impaired ERα activation, and prevented its oncogenic role on the androgen receptor (AR). Moreover, this combination inhibited ERK1/2 activation, promoting apoptosis. The study of the hormonal microenvironment suggests that this combination should not be applied in early stages of ER+ breast tumors. CONCLUSIONS: Contrary to Ana and Let, this study highlights the potential benefits of combining CBD with Exe to improve breast cancer treatment and opens up the possibility of new therapeutic approaches comprising the use of cannabinoids.

An Exemestane Derivative, Oxymestane-D1, as a New Multi-Target Steroidal Aromatase Inhibitor for Estrogen Receptor-Positive (ER+) Breast Cancer: Effects on Sensitive and Resistant Cell Lines.

Around 70-85% of all breast cancer (BC) cases are estrogen receptor-positive (ER+). The third generation of aromatase inhibitors (AIs) is the first-line treatment option for these tumors. Despite their therapeutic success, they induce several side effects and resistance, which limits their efficacy. Thus, it is crucial to search for novel, safe and more effective anti-cancer molecules. Currently, multi-target drugs are emerging, as they present higher efficacy and lower toxicity in comparison to standard options. Considering this, this work aimed to investigate the anti-cancer properties and the multi-target potential of the compound 1α,2α-epoxy-6-methylenandrost-4-ene-3,17-dione (Oxy), also designated by Oxymestane-D1, a derivative of Exemestane, which we previously synthesized and demonstrated to be a potent AI. For this purpose, it was studied for its effects on the ER+ BC cell line that overexpresses aromatase, MCF-7aro cells, as well as on the AIs-resistant BC cell line, LTEDaro cells. Oxy reduces cell viability, impairs DNA synthesis and induces apoptosis in MCF-7aro cells. Moreover, its growth-inhibitory properties are inhibited in the presence of ERα, ERß and AR antagonists, suggesting a mechanism of action dependent on these receptors. In fact, Oxy decreased ERα expression and activation and induced AR overexpression with a pro-death effect. Complementary transactivation assays demonstrated that Oxy presents ER antagonist and AR agonist activities. In addition, Oxy also decreased the viability and caused apoptosis of LTEDaro cells. Therefore, this work highlights the discovery of a new and promising multi-target drug that, besides acting as an AI, appears to also act as an ERα antagonist and AR agonist. Thus, the multi-target action of Oxy may be a therapeutic advantage over the three AIs applied in clinic. Furthermore, this new multi-target compound has the ability to sensitize the AI-resistant BC cells, which represents another advantage over the endocrine therapy used in the clinic, since resistance is a major drawback in the clinic.

The anti-cancer potential of crotoxin in estrogen receptor-positive breast cancer: Its effects and mechanism of action.

Estrogen receptor-positive (ER+) breast cancer is the most diagnosed subtype of breast cancer. Currently, aromatase inhibitors (AIs) are used as first-line treatment option in this type of tumors, however they cause several side effects, which is why new therapeutic approaches are demanding. The South American rattlesnake Crotalus durissus terrificus produces a venom enriched in several bioactive substances, like phospholipases A2 (PLA2). One of those is crotoxin, a ß-neurotoxin, that has already been reported for its anti-cancer properties in different cancers. Recently, its clinical interest has emerged and, in fact, a clinical trial in patients with advanced cancer is underway. Considering this, in this work, we studied the biological mechanisms behind the anti-cancer effects of crotoxin B (CTX) in an ER+ aromatase-overexpressing breast cancer cell line (MCF-7aro cells). Results revealed that CTX impairs MCF-7aro cells growth, through a cell cycle arrest at G2/M phase, inhibition of ERK1/2 pathway and by apoptosis through activation of caspase-8. In addition, it can be considered a safe natural compound as did not affect non-cancerous cells and only showed anti-growth effects in breast cancer cells. Therefore, this study represents an important landmark to better understand the effects and mechanisms of action of crotoxin in ER+ breast cancer.

Unveiling the mechanism of action behind the anti-cancer properties of cannabinoids in ER+ breast cancer cells: Impact on aromatase and steroid receptors.

Breast cancer is the leading cause of cancer-related death in women worldwide. In the last years, cannabinoids have gained attention in the clinical setting and clinical trials with cannabinoid-based preparations are underway. However, contradictory anti-tumour properties have also been reported. Thus, the elucidation of the molecular mechanisms behind their anti-tumour efficacy is crucial to better understand its therapeutic potential. Considering this, our work aims to clarify the molecular mechanisms underlying the anti-cancer properties of the endocannabinoid anandamide (AEA) and of the phytocannabinoids, cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC), in estrogen receptor-positive (ER+) breast cancer cells that overexpress aromatase (MCF-7aro). Their in vitro effects on cell proliferation, cell death and activity/expression of aromatase, ERα, ERß and AR were investigated. Our results demonstrated that cannabinoids disrupted MCF-7aro cell cycle progression. Unlike AEA and THC that induced apoptosis, CBD triggered autophagy to promote apoptotic cell death. Interestingly, all cannabinoids reduced aromatase and ERα expression levels in cells. On the other hand, AEA and CBD not only exhibited high anti-aromatase activity but also induced up-regulation of ERß. Therefore, all cannabinoids, albeit by different actions, target aromatase and ERs, impairing, in that way, the growth of ER+ breast cancer cells, which is dependent on estrogen signalling. As aromatase and ERs are key targets for ER+ breast cancer treatment, cannabinoids can be considered as potential and attractive therapeutic compounds for this type of cancer, being CBD the most promising one. Thus, from an in vitro perspective, this work may contribute to the growing mass of evidence of cannabinoids and cannabinoids-based medicines as potential anti-cancer drugs.

Cannabinoids in Breast Cancer: Differential Susceptibility According to Subtype.

Although cannabinoids have been used for centuries for diverse pathological conditions, recently, their clinical interest and application have emerged due to their diverse pharmacological properties. Indeed, it is well established that cannabinoids exert important actions on multiple sclerosis, epilepsy and pain relief. Regarding cancer, cannabinoids were first introduced to manage chemotherapy-related side effects, though several studies demonstrated that they could modulate the proliferation and death of different cancer cells, as well as angiogenesis, making them attractive agents for cancer treatment. In relation to breast cancer, it has been suggested that estrogen receptor-negative (ER-) cells are more sensitive to cannabinoids than estrogen receptor-positive (ER+) cells. In fact, most of the studies regarding their effects on breast tumors have been conducted on triple-negative breast cancer (TNBC). Nonetheless, the number of studies on human epidermal growth factor receptor 2-positive (HER2+) and ER+ breast tumors has been rising in recent years. However, besides the optimistic results obtained thus far, there is still a long way to go to fully understand the role of these molecules. This review intends to help clarify the clinical potential of cannabinoids for each breast cancer subtype.

Discovery of a multi-target compound for estrogen receptor-positive (ER+) breast cancer: Involvement of aromatase and ERs.

Despite intense research, breast cancer remains the leading cause of cancer-related death in women worldwide, being estrogen receptor-positive (ER+) the most common subtype. Nowadays, aromatase inhibitors (AIs), the selective estrogen receptor modulator (SERM) tamoxifen and the selective estrogen receptor down-regulator (SERD) fulvestrant are used as therapeutic options for ER+ breast cancer, since they interfere directly with the production of estrogens and with the activation of estrogen-dependent signaling pathways. Despite the success of these treatments, the occurrence of resistance limits their clinical efficacy, demanding the development of novel therapies. Recently, multi-target compounds emerged as promising therapeutic strategies for ER+ breast cancer, as they can potentially modulate several important targets simultaneously. In line with this, in this work, the anti-cancer properties and multi-target action of 1,1-Bis(4-hydroxyphenyl)-2-phenylbut-1-ene, tamoxifen bisphenol (1,1-BHPE), were evaluated in an ER+ breast cancer cell model (MCF-7aro cells). Molecular docking analysis predicted that 1,1-BHPE was able to bind to aromatase, ERα and ERß. In vitro studies showed that, although it did not present anti-aromatase activity, 1,1-BHPE reduced aromatase protein levels and interfered with ERα and ERß signaling pathways, acting as an ERα antagonist and inducing ERß up-regulation. Through these mechanisms, 1,1-BHPE was able to impair breast cancer growth and induce apoptosis. This represents an important therapeutic advantage because the main players responsible for estrogen production and signaling are modulated by a single compound. To the best of our knowledge, this is the first study describing the anti-cancer properties of 1,1-BHPE as a multi-target compound specific for ER+ breast cancer.