New Promising Steroidal Aromatase Inhibitors with Multi-Target Action on Estrogen and Androgen Receptors for Breast Cancer Treatment

Background/Objectives: Endocrine therapies that comprise anti-estrogens and aromatase inhibitors (AIs) are the standard treatment for estrogen receptor-positive (ER+) (Luminal A) breast cancer—the most prevalent subtype. However, the emergence of resistance restricts their success by causing tumor relapse and re-growth, which demands a switch towards other therapeutic approaches in order to minimize or overcome resistance. Indeed, this clinical limitation highlights the search for new molecules to improve cancer treatment. Recently, strategies that address multiple targets have been emerging, and multi-target drugs have the potential to become the future anti-cancer molecules. Our group has been searching for new multi-target compounds, and as part of this, our study aims to understand the anti-cancer and multi-target potential of three new steroidal aromatase inhibitors (AIs): 7α-methylandrost-4-en-17-one (6), 7α-methylandrost-4-ene-3,17-dione (10a) and androsta-4,9(11)-diene-3,17-dione (13). Methods: Their in vitro actions and molecular mechanisms were elucidated in a sensitive ER+ aromatase-overexpressing breast cancer cell line, MCF-7aro cells, as well as in an AI-resistant ER+ breast cancer cell line, LTEDaro cells. Results: All the new AIs (10 µM) prevented the proliferation of MCF-7aro cells by arresting cell cycle progression. Interestingly, all AIs (10 µM) act as androgen receptor (AR) agonists and modulate ER levels, synthesis and signaling to induce the apoptosis of ER+ breast cancer cells. Additionally, these new AIs (10 µM) also re-sensitize resistant cells by promoting apoptosis, offering a therapeutic benefit. Conclusions: Overall, new steroidal polypharmacological compounds have been discovered that, by acting as AIs, ER modulators and AR agonists, impair ER+ breast cancer cell growth. Overall, this study is a breakthrough on drug discovery as it presents new molecules with appealing anti-cancer properties and multi-target action for the treatment of ER+ breast cancer.