Selective estrogen receptor modulators and betulinic acid act synergistically to target ERα and SP1 transcription factor dependent Pygopus expression in breast cancer.

Abstract

AIMS:

Estrogen and progesterone hormone receptor (ER and PR) expression in invasive breast cancer predicts response to hormone disruptive therapy. Pygopus2 (hPYGO2) encodes a chromatin remodelling protein important for breast cancer growth and cell cycle progression. The aims of this study were to determine the mechanism of expression of hPYGO2 in breast cancer and to examine how this expression is affected therapeutically.

METHODS:

hPYGO2 and ER protein expression was examined in a breast tumour microarray by immunohistochemistry. hPYGO2 RNA and protein expression was examined in ER+ and ER- breast cancer cell lines in the presence of selective estrogen hormone receptor modulator drugs and the specificity protein-1 (SP1) inhibitor, betulinic acid (BA). The effects of these drugs on the ability for ER and SP1 to bind the hPYGO2 promoter and affect cell cycle progression were studied using chromatin immunoprecipitation assays.

RESULTS:

hPYGO2 was expressed in seven of eight lines and in nuclei of 98% of 65 breast tumours, including 3 Ductal carcinoma in situ and 62 invasive specimens representing ER-negative (22%) and ER-positive (78%) cases. Treatment with either 4-Hydroxytamoxifen (OHT) or fulvestrant reduced hPYGO2 mRNA 10-fold and protein 5-10-fold within 4 h. Promoter analysis indicated an ER/SP1 binding site at nt -225 to -531 of hPYGO2. SP1 RNA interference and BA reduced hPYGO2 protein and RNA expression by fivefold in both ER- and ER+ cells. Further attenuation was achieved by combining BA and 4-OHT resulting in eightfold reduction in cell growth.

CONCLUSIONS:

Our findings reveal a mechanistic link between hormone signalling and the growth transcriptional programme. The activation of its expression by ERα and/or SP1 suggests hPYGO2 as a theranostic target for hormone therapy responsive and refractory breast cancer.

• Authors: Youlian R Tzenov, Phillip Andrews, Kim Voisey, Luis Gai, Beverley Carter, Kathryn Whelan, Catherine Popadiuk, Kenneth R Kao
• Journal: Journal of clinical pathology (J Clin Pathol) Vol. 69 Issue 6 Pg. 518-26 (Jun 2016) ISSN: 1472-4146 [Electronic] England
• PMID: 26645832 (Publication Type: Journal Article)
• Copyright: Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Chemical References

• Antineoplastic Agents
• ESR1 protein, human
• Estrogen Receptor alpha
• Hydroxytestosterones
• Intracellular Signaling Peptides and Proteins
• PYGO2 protein, human
• Pentacyclic Triterpenes
• Selective Estrogen Receptor Modulators
• Sp1 Transcription Factor
• Sp1 protein, human
• Triterpenes
• Tamoxifen
• afimoxifene
• 4,17 beta-dihydroxy-4-androstene-3-one
• Fulvestrant
• Estradiol
• Betulinic Acid

Topics

• Antineoplastic Agents (therapeutic use)
• Breast Neoplasms (metabolism)
• Carcinoma, Intraductal, Noninfiltrating (metabolism)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Estradiol (analogs & derivatives, therapeutic use)
• Estrogen Receptor alpha (genetics, metabolism)
• Female
• Fulvestrant
• Gene Expression Regulation, Neoplastic
• Humans
• Hydroxytestosterones (therapeutic use)
• Intracellular Signaling Peptides and Proteins (genetics, metabolism)
• Microarray Analysis
• Pentacyclic Triterpenes
• Promoter Regions, Genetic (genetics)
• Selective Estrogen Receptor Modulators (metabolism)
• Signal Transduction (drug effects)
• Sp1 Transcription Factor (antagonists & inhibitors, genetics, metabolism)
• Tamoxifen (analogs & derivatives, therapeutic use)
• Triterpenes (therapeutic use)
• Betulinic Acid