Booth Id:
CELL041
Category:
Cellular and Molecular Biology
Year:
2019
Finalist Names:
Chai, Esther (School: Townsend Harris High School)
Abstract:
Over 70% of breast cancer patients’ cells express the estrogen receptor (ER), which
promotes the proliferation of cancer cells, by activating the expression of tumor-promoting
genes. In the normal ER pathway, estrogen binds to ER, stimulating its activity. Drugs have been
developed to interfere with ER signaling, thereby inhibiting ER-driven tumor growth. However,
due to prolonged use of hormonal therapy in the clinical setting, resistance occurs where cells
develop mutations and activate themselves in the absence of estrogen. To identify the mechanism
by which one of the mutant ERs, S463P, is able to activate, a RIME analysis revealed that high
levels of the GREB1 protein was bound to the mutant S463P ER. Based on these findings,
GREB1 was hypothesized to be a potential coactivator of the mutant estrogen receptor. A series
of experiments was conducted to better understand the role of GREB1. The data revealed that
partial loss of GREB1 using shRNA showed a differential effect on ER activity, as the data
showed increase in RNA levels of some target genes but decrease in others. Subsequently, the
CRISPR/Cas9 system was used to knockout the expression of GREB1. The GREB1 knockout
resulted in a notable decrease of downstream targets, as detected by lighter bands in the western
blot and decrease in mRNA levels in qRT-PCR analysis. These findings supported the
hypothesis and indicated that GREB1 is a potential coactivator of the mutant S463P ER. Its role
as a potential coactivator may be exploited for therapeutic targeting in the clinical setting.