# Botanical Modulation of AhR-ERα by Crosstalk Inhibitors Promotes Estrogen (E2) Detoxification

> **NIH NIH F31** · UNIVERSITY OF ILLINOIS AT CHICAGO · 2020 · $41,334

## Abstract

Botanical Modulation of AhR-ERα by Crosstalk Inhibitors Promotes Estrogen (E2) Detoxification
Estrogen receptor (ER) positive breast cancer poses significant health risks for postmenopausal women, and is
in part mediated by the estrogen (E2) metabolite, estradiol-3,4-quinone, which causes depurinating adducts
and leads to mutations. P450 1B1 is the primary enzyme for the conversion of estradiol to the 4-hydroxylated
product, which can result in a genotoxic 4-quinone, while P450 1A1, which is normally epigenetically inhibited
by E2-activated estrogen receptor alpha (ERα), converts estradiol to a nongenotoxic 2-hydroxylated product.
Activated aryl hydrocarbon receptor (AhR) induces degradation of ERα as well as the transcription of both
CYP1A1 and CYP1B1, which are translated into P450 1A1 and 1B1 respectively. Activators and ligands of
AhR (Crosstalk Inhibitors) have been shown to preferentially upregulate CYP1A1 and ultimately the
nongenotoxic 2-hydroxylated estradiol metabolite (estrogen detoxification pathway), through downregulation of
the epigenetic inhibition of CYP1A1. Women have increasingly turned to botanical dietary supplements (BDS),
instead of traditional hormone replacement therapy (HRT), since the release of the findings that estrogen +
progesterone increases breast cancer risk. Interestingly, icaritin, a bioactive compound from Epimedium sp., a
botanical used for women's health purposes, has been shown to activate AhR. The hypothesis of this
proposal is that some women's health botanicals contain antiestrogenic, AhR activating compounds which
degrade ERα (Aim 1) and reverse epigenetic CYP1A1 inhibition to preferentially activate the estrogen
detoxification pathway in an in vitro cell culture model (Aim 2) and an in vivo ovariectomized rat model (Aim 3).
Inhibition of estrogen-dependent alkaline phosphatase activity in Ishikawa cells, and a failure to inhibit a
fluorescent estradiol-ERα complex by botanical compounds in a fluorescence polarization enzyme assay will
provide antiestrogenic compounds which do not act through ERα. These compounds will be subjected to in-
cell western of MCF-7 (ER+) cells against an ERα antibody to find compounds which degrade ERα. Additional
XRE-luciferase activity in HepG2 cells will indicate AhR activating compounds, while a decrease in methylation
through a ChIP assay of DNMT and XRE, and qRT-PCR of CYP1A1/1B1 will show that the reversal of
estradiol mediated epigenetic CYP1A1 inhibition leads to upregulation of the estrogen detoxification pathway
by Crosstalk Inhibitors in vitro. This premise will be taken to an ovariectomized rat model involving E2 and
botanical compounds before sacrificing and analyzing uterine weight, performing LC-MS analysis of the E2
metabolites, and quantifying ERα expression levels using immunohistochemistry. This research may reveal
mechanisms by which some bioactive women's health BDS compounds exhibit antiestrogenic outcomes, and
the importance of the E2 detoxification pa...

## Key facts

- **NIH application ID:** 9977925
- **Project number:** 5F31AT010090-03
- **Recipient organization:** UNIVERSITY OF ILLINOIS AT CHICAGO
- **Principal Investigator:** Ryan Thomas Hitzman
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $41,334
- **Award type:** 5
- **Project period:** 2018-08-16 → 2021-08-15

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9977925

## Citation

> US National Institutes of Health, RePORTER application 9977925, Botanical Modulation of AhR-ERα by Crosstalk Inhibitors Promotes Estrogen (E2) Detoxification (5F31AT010090-03). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9977925. Licensed CC0.

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