# Presentation: 429696

## OVERVIEWBiology of Estrogen & Progesterone Receptors

***Benita S. Katzenellenbogen***
**Swanlund Professor of Physiology,**
**Cell and Structural Biology**
**University of Illinois and College of Medicine**

## Important Issues

** ****Roles of ER******** and ER******
** ****Distinct Functions of PR-A and PR-B**
** ****Selective Ligands (SERMs and SPRMs)**
** ****Coregulators**
**  ****Interrelationships Between Estrogen and**
**  ****	****Progestin Hormone-Receptor Pathways**
**  ****Tissue Selectivity in Estrogen and **
**	****Progestin Actions**

## Target Tissues in Females & Males

**Target Tissues in Females & Males**

**Also:**
**  ****Colon (& Intestine)**
**  ****Bladder & Urogenital Tract**
**  ****Lung**

***Korach,  2001***

## Estrogen Receptor in Breast Cancer

**Predicts:**
**  ****Improved Disease-Free Survival**
**  ****Response to Tamoxifen/Endocrine**
**    ****Therapy**

## New York Times, April 7, 1998, p. A1

**Researchers Find the First Drug Known to Prevent Breast Cancer**

***Tamoxifen Helps Women, but Has Side Effects***

## Tissue Selectivity

***Antagonist***** - Breast, Uterus**
***Agonist***** - Bone, Brain, Colon,****	**** ****	****Lipid Profile, Vasomotor, ****	****	****Cardiovascular**

***- Ideal Profile for HRT -***

## TRIPARTITE PHARMACOLOGY MEDIATED BY NUCLEAR HORMONE RECEPTORS– Underlies Tissue Selectivity –

## Receptor Actions in Cells

**Receptor Actions in Cells**

**(B. Katzenellenbogen et al. *****Recent Prog. Horm. Res*****.,2000)**

## Human Estrogen Receptors  and 

**Notes:**
Human Estrogen Receptors  and 

## Exquisite Precision in Receptor Regulation

**Small Changes**
**in**
**Ligand Structure**

**Major Changes**
**in**
**Biological Character**

**ER********ER******
**Different Ligands**

**Different Pharmacology**
**At**
**Different Target Genes**

**Exquisite Precision in Receptor Regulation**

## Ligands for Estrogen Receptors

**Estrogens**

**Known SERMs**

**Novel ER********/ER******
**Selective Ligands**

**Estradiol**

**Diethylstilbestrol**

**Tamoxifen**

**Raloxifene**

**Droloxifene, Idoxifene,**
**Toremifene, GW5638,**
**EM652, Cp-336156, others**

**PPT (Pyrazole)**
***ER************ Agonist***

**R,R-THC**
***ER************ Agonist &***
***ER************ Antagonist***

**Ligands for Estrogen Receptors**

**MPP**
***ER************ Antagonist***

**DPN (Nitrile)**
***ER************ Agonist***

## SERM Action

**(B. & J. Katzenellenbogen, Science, **_**295**_**: 2380, 2002) **

## Structures of Diethylstilbestrol-ER LBD and Hydroxytamoxifen-ER LBD

**Diethylstilbestrol**

**Hydroxytamoxifen**

**Greene, 4/99**

## PPT, an ER Specific Ligand, Prevents Ovariectomy-Induced Loss of Bone Mineral Density

**0**

**100**

**200**

**300**

**400**

**500**

**600**

**700**

**800**

**Sham**

**Ovx**

**PPT (2mg/kg)**

**17beta-estradiol**

**(6ug/kg)**

**Bone Mineral Density**
** ****(mg/cm3)**

**Total**

**Trabecular**

- *

- *

- *

- *

- *

- *

- * significantly greater than ovx (p < 0.01)

**(Harris et al. and Katzenellenbogens,**
**        ****Endocrinology, 2002)**

## PPT, an ER Specific Ligand, Prevents Hot Flush in a Rat Model

**0**

**1**

**2**

**3**

**4**

**5**

**6**

**Vehicle**

**PPT**

**Temperature Increase**
**(degrees +/- SEM)**

**(Harris et al. and Katzenellenbogens,**
**Endocrinology 2002)**

**Ethinyl**
**Estradiol**

## Gene Regulation

## Estrogen Effects on Cell Cytoarchitecture

**From Vic *****et al*****., *****Cancer Res*****., 1982**

## Estrogen Effects in Mammary Glandand Breast Cancer

**Cell Cycle Regulation --**
******  ****Proliferation****	****  ******** Apoptosis**
**Cytoskeletal Organization**
**Signal Transduction**

## Estrogen Receptor Beta

**A ****“dampener”**** of ER******** activity?**
**Some overlap with ER******** but also some **
**	****	****different gene activations**

## ER in Human Breast

**(Roger et al., **_***Cancer Res***_**. **_**61**_**:2537, 2001)**

## Gene Expression Profiling by DNA Microarrays Differentiates Estrogen and SERM Activities 

**Gene Expression Profiling by DNA Microarrays Differentiates Estrogen and SERM Activities **

-  Estrogen Stimulates Many Genes

-  Tamoxifen also Stimulates Some of these Genes

-  Raloxifene Stimulates a Few of these Genes

-  Different Ligands Stimulate Somewhat Different Gene Sets

**Notes:**
Of 37 genes stim by E2 - -

A,B,C -- expected patterns

D,E,F -- unusual patterns

## Comparative Patterns of Gene Stimulation by Estradiol and SERMs (MCF-7 Cells)  [n = 33]

**E2 and TOT (n = 12)**

**C**

**E2**

**ICI**

**Ral**

**TOT**

**E2, Ral and TOT (n = 4)**

**C**

**E2**

**ICI**

**Ral**

**TOT**

**E2 Only (n = 17)**

**C**

**E2**

**ICI**

**Ral**

**TOT**

**A**

**B**

**C**

**Response**

**Response**

**Response**

**Notes:**
TOT , considered the most estrogen-like SERM

## SERM Antagonism of Estradiol Stimulation       (MCF-7 Cells)    [n = 35]

**Notes:**
Of 37 genes stim by E2 - -

A,B,C -- expected patterns

D,E,F -- unusual patterns

## Progesterone Receptor

## Ligands for Progesterone Receptor

## Human Progesterone Receptor: A and B Forms

**  ****From single gene by alternate transcription**
**       ****initiation**** ****(different promoters)**
**  ****Different activities **

## Human Progesterone Receptor Isoforms A and B

**  ****Differential transcriptional activities**
**      ****Cell type- and promoter-specific**
**      ****Often PR-B > PR-A**
**  ****PR-A repressor of PR-B and ER signaling**
**   ****Present at unequal levels in breast tumors; some tissues**
**      ****PR-A predominance as early event in carcinogenesis**

## Interrelationships Between Estrogen and Progestin Receptor Signaling Pathways

**Interrelationships Between Estrogen and Progestin Receptor Signaling Pathways**

**ER**

**PR**

**Uterus**

**Breast**

**+**

**–**

***PR Opposes***
***ER Stimulation***

***PR Enhances***
***ER Stimulation***

***Other Tissues?***

## Women’s Health Initiative (WHI) Clinical Trial

**Ended at 5.2 years, May 2002**
***[JAMA 288:321-333, 2002]***

**16,608 Healthy postmenopausal US women**

**Estrogen**
** ****(CEE 0.625 mg/d)**

**+**

**Progestin**
** ****(MPA 2.5 mg/d)**

***together daily***

## Would outcome be different if:

**...****estrogen only?**
**...****different formulations, dosages?**
**...****different estrogen(s)?**
**...****different progestin?**

## Biology of Estrogens  and Progestins are Determined By:

**Ligand structure**
**ER subtype (******** or ********) and PR isoform (A or B) **
**Gene promoter responsive unit**
**Character and balance of coactivators and corepressors**

## Take-Home Messages

**Estrogens and progestins act through ER and PR.**
**Ligands can be: **
***Agonists-------SERMs/SPRMs-------Antagonists***
**(mixed agonists/antagonists)**
**3.****	****Different ligands induce different receptor conformations that determine all further interactions.**

## ER and PR work with partner proteins that modulate their activity.  Coregulator levels vary in different tissues.

***Ligand      Receptor       Coregulator      Tissue Responses***
**Many interrelationships between ER and PR pathways: **
**Progestins modulate estrogen action but also act independently.**
**Progestin effects on estrogen actions vary in different tissues -**
***Mid-luteal when progesterone levels high --***
***– ******Breast: enhances mitotic activity***
***– ******Uterus: suppresses mitotic activity***

## Questions that Remain

**What estrogen/SERM (± progestin/SPRM combination) will give the best benefit/risk for HRT in the diverse tissues in which these hormones act ?**
**Respective roles of ER******** and ER******** in mediating the desired vs. undesired effects of estrogen, and modulation of these activities by progestins**

## Slide 35