The beneficial androgenic action of steroidal aromatase inactivators in estrogen-dependent breast cancer after failure of nonsteroidal drugs

Lanyang Gao,Zheng Bao,Ling Liu,Alexander T Teichmann,Dan Nie,Xiaofang Li,Youzhe Yang,Jiamin Li,Guilin Wang,Heng Deng,F Heinrich Wieland,Zuyuan Rong

doi:10.1038/s41419-019-1724-9

Abstract

Direct treatment of ER (+) breast cancer with Formestane diminishes the tumor within weeks. This is unlikely due to lack of estrogens alone. We proposed that it is the negative influence of androgens on the growth of ER(+) breast cancer. We investigated the influence of Formestane and Exemestane and of their major androgenic metabolites 4-hydroxytestosterone and 17-hydroexemestane on the proliferation of MCF-7 cells and ZR-75-1 cells. Inhibitory effects could be prevented by antiandrogens and siRNA. Activation of the AR in MCF-7 and U2-OS cells was tested by reporter gene assays. In vivo androgenicity was evaluated using the Hershberger assay. Influence on the cell cycle was demonstrated by flow-cytometry. Influence of androgens on the activity of CCND1 was demonstrated by Chip-qPCR. Antitumor activity was determined by topical treatment of DMBA tumors. We found that breast cancer cells can metabolize Formestane and Exemestane to androgenic compounds which inhibit proliferation. This can be explained by hindering the accessibility of CCND1 by histone modification. Androgenic metabolites can abolish the growth of DMBA-tumors and prevent the appearance of new tumors. The lack of cross-resistance between steroidal and nonsteroidal aromatase inhibitors is due to inhibitory effects of androgenic steroidal metabolites on the production of cyclin D1. These sterols not only inhibit proliferation of cancer cells but can also stop the growth of DMBA cancers upon direct absorption into the tumor. The quick and considerable effect on ER(+) tumors may open a new avenue for neodjuvant treatment.

Highlights

More than 50% of breast cancers express estrogen receptor alpha (ERα) and are dependent on estrogens for their development and growth[1,2]
In order to gain more information about the androgenic properties of Formestane, 4-OHT, Exemestane, and 17HEXE, and about their intracellular metabolism and influence on certain cellular behaviors we have investigated the affinity of the sterols to the AR by competitive receptor-binding assays and their ability to activate the AR by reporter gene assays
We investigated the androgenic and myotrophic properties of the substances in castrated young male rats and compared the influence of different sterols on the growth of E2-dependent DMBA-induced breast cancers in ovariectomized rats under hormone replacement therapy in order to characterize the induction of tumor atrophy and apoptosis at physiological levels of estradiol

Summary

Introduction

More than 50% of breast cancers express estrogen receptor alpha (ERα) and are dependent on estrogens for their development and growth[1,2]. In the past the main method of inhibiting the cancer growth was to block ERα by tamoxifen[3]. The first specific steroidal AI in clinical use was 4hydroxyandrostenedione (4-OHA)[6], named Formestane. It came to the market as an intramuscular depot. Official journal of the Cell Death Differentiation Association. Gao et al Cell Death and Disease (2019)10:494 preparation (Lentaron®Depot). Lentaron® is administered at a single dose of 250 mg/patient/application once every 2 weeks. Since this tedious way of administration is not suited for adjuvant treatment, Lentaron was taken from the market. Nonsteroidal AIs are chemicals which are not subjected to much metabolic changes within cells, whereas the structure of the steroidal aromatase inhibitors can undergo slight changes within cells giving rise to different active sterols (intracrinology)[7]

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Conclusion