Inhibition of growth and appearance of estrogen-dependent rat mammary tumors by 10-propargylestr-4-ene-3,17-dione, an aromatase inhibitor

A review of estrogen receptor/androgen receptor genomics in male breast cancer

Male breast cancer is a rare disease, of which little is known. In contrast to female breast cancer, the very vast majority of all cases are positive for estrogen receptor alpha (ERα), implicating the function of this steroid hormone receptor in tumor development and progression. Consequently, adjuvant treatment of male breast cancer revolves around inhibition of ERα. In addition, the androgen receptor (AR) gradually receives more attention as a relevant novel target in breast cancer treatment. Importantly, the rationale of treatment decision making is strongly based on parallels with female breast cancer. Yet, prognostic indicators are not necessarily the same in breast cancer between both genders, complicating translatability of knowledge developed in female breast cancer toward male patients. Even though ERα and AR are expressed both in female and male disease, are the genomic functions of both steroid hormone receptors conserved between genders? Recent studies have reported on mutational and epigenetic similarities and differences between male and female breast cancer, further suggesting that some features are strongly conserved between the two diseases, whereas others are not. This review critically discusses the recent developments in the study of male breast cancer in relation to ERα and AR action and highlights the potential future studies to further elucidate the genomic regulation of this rare disease.

A novel in vitro and in vivo breast cancer model for testing inhibitors of estrogen biosynthesis and its action using mammary tumor cells with an activated int-5/aromatase gene

We recently showed that the cellular gene int-5/aromatase in BALB/c mammary alveolar hyperplastic nodule (D2 HAN/D2 tumor cells) is activated as a result of mouse mammary tumor virus integration within the 3' untranslated region of the aromatase gene. In the present study, we evaluated the effect of various aromatase inhibitors on androstenedione-mediated tumor cell growth. Also, we compared the effect of the non-steroidal aromatase inhibitor (CGS 16949A) on the inhibition of tumor growth. Our results show that D2 tumor cells respond well to various aromatase inhibitors and antiestrogens. We examined the usefulness of this model by using D2 tumor cells to simulate postmenopausal breast cancer employing both in vitro cell culture and in vivo ovariectomized (OVX) nude mouse. Unlike DMBA-induced tumors or other models, D2 tumor cells form very rapid tumors within a few days in intact mice or OVX nude mice with androstenedione supplementation and respond well to an aromatase inhibitor. This model with its known mechanism of aromatase activation should be useful for studying the role of intra-tumoral estrogen in mammary cancer, for evaluating the effects of aromatase inhibitors and antiestrogens, and for comparing breast cancer treatments.

Presence of aromatase inhibitors in cycads

Cycads, the most primitive of the living gymnosperms, have been used and continue to be used for food and medicinal purposes by many cultures, although toxins must be removed before ingestion. In our quest to identify tropical plants that contain inhibitors of the cytochrome P-450 aromatase and thus may be efficacious in treating estrogen-dependent tumors, we have screened extracts from 5 species of cycad folia encompassing 3 genera: Cycas cairnsiana F. Muell., Cycas revoluta Thunb., Cycas rumphii Miq., Dioon spinulosum Dyer and Encephalartos ferox Bertol. All extracts were found to contain inhibitors of the human enzyme.