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Updated: Nov 11, 2025
Pooled CRISPR-Based Genetic Screens in Mammalian Cells
Published on: September 4, 2019
A genome-scale CRISPR Cas9 dropout screen identifies synthetically lethal targets in SRC-3 inhibited cancer cells
Yosi Gilad1, Yossi Eliaz2, Yang Yu1
1Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA.
Abstract:
Steroid receptor coactivator 3 (SRC-3/NCoA3/AIB1), is a key regulator of gene transcription and it plays a central role in breast cancer (BC) tumorigenesis, making it a potential therapeutic target. Beyond its function as an important regulator of estrogen receptor transcriptional activity, SRC-3 also functions as a coactivator for a wide range of other transcription factors, suggesting SRC-3 inhibition can be beneficial in hormone-independent cancers as well. The recent discovery of a potent SRC-3 small molecule inhibitor, SI-2, enabled the further development of additional related compounds. SI-12 is an improved version of SI-2 that like SI-2 has anti-proliferative activity in various cancer types, including BC. Here, we sought to identify gene targets, that when inhibited in the presence of SI-12, would lead to enhanced BC cell cytotoxicity. We performed a genome-scale CRISPR-Cas9 screen in MCF-7 BC cells under conditions of pharmacological pressure with SI-12. A parallel screen was performed with an ER inhibitor, fulvestrant, to shed light on both common and distinct activities between SRC-3 and ERα inhibition. Bearing in mind the key role of SRC-3 in tumorigenesis of other types of cancer, we extended our study by validating potential hits identified from the MCF-7 screen in other cancer cell lines.
Insights
Steroid receptor coactivator 3 (SRC-3) inhibition enhances breast cancer cell killing when combined with specific gene targets. This study identifies key genes that, when inhibited alongside SRC-3, could improve cancer therapies.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Steroid receptor coactivator 3 (SRC-3) is crucial for breast cancer (BC) development and is a therapeutic target.
- SRC-3 coactivates numerous transcription factors, indicating its potential in hormone-independent cancers.
- SI-12 is a novel small molecule inhibitor of SRC-3 with anti-proliferative effects.
Purpose of the Study:
- To identify gene targets that enhance BC cell cytotoxicity when inhibited in combination with SI-12.
- To compare the effects of SRC-3 inhibition with estrogen receptor (ER) inhibition using fulvestrant.
- To validate identified gene targets in various cancer cell lines beyond breast cancer.
Main Methods:
- Genome-scale CRISPR-Cas9 screening was performed in MCF-7 BC cells under SI-12 treatment.
- A parallel screen utilized the ER inhibitor fulvestrant.
- Potential gene targets were validated in additional cancer cell lines.
Main Results:
- The study identified specific gene targets that, upon inhibition, significantly increased BC cell death in the presence of SI-12.
- Comparative analysis revealed both overlapping and distinct mechanisms between SRC-3 and ERα inhibition.
- Validated hits demonstrated efficacy in non-breast cancer cell lines, suggesting broader therapeutic potential.
Conclusions:
- Combined inhibition of SRC-3 and identified gene targets presents a promising strategy for enhancing BC cytotoxicity.
- Understanding the interplay between SRC-3 and ER signaling provides insights into targeted cancer therapies.
- SRC-3 inhibition holds potential for treating a wider spectrum of cancers, not limited to hormone-dependent types.
