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Updated: Jul 2, 2026
In Vivo CRISPR/Cas9 Screening to Simultaneously Evaluate Gene Function in Mouse Skin and Oral Cavity
Published on: November 2, 2020
A tailored in vivo CRISPR screen identifies BAP1 as a potent tumor suppressor of sarcoma
Jianguo Huang1, Xingliang Liu1, Warren Floyd2
1Earle A. Chiles Research Institute, Providence Cancer Institute, Portland, Oregon, USA.
Abstract:
Undifferentiated pleomorphic sarcoma (UPS) is one of the most common adult soft-tissue sarcomas (STSs), yet therapeutic progress remains limited because of the absence of recurrent oncogenic driver mutations. To identify tumor suppressors contributing to UPS pathogenesis, we performed a customized in vivo CRISPR/Cas9 screen in mice. This approach identified BRCA1-associated protein 1 (BAP1) as a potent tumor suppressor in STS. Integrative analyses using RNA sequencing, multiplex immunohistochemistry, and flow cytometry revealed that Bap1-deficient sarcomas exhibited a markedly immunosuppressive tumor microenvironment. Consistent with these findings, BAP1 protein expression was reduced in human UPS, whereas polo-like kinase 1 (PLK1) expression was elevated. Functional studies demonstrated that PLK1 was required for the growth and survival of Bap1-deficient sarcomas. Pharmacologic inhibition of PLK1 with volasertib significantly suppressed tumor growth in both syngeneic and autochthonous mouse models. Moreover, combining PLK1 inhibition with anti-PD-1 therapy enhanced tumor control and improved survival compared with either treatment alone. Together, these results identify PLK1 as a potential therapeutic vulnerability in BAP1-deficient sarcomas and support further evaluation of combined PLK1 inhibition and immune checkpoint blockade as a treatment strategy for a subset of STSs.
Insights
BRCA1-associated protein 1 (BAP1) loss in soft tissue sarcomas (STS) creates an immunosuppressive tumor environment. Inhibiting polo-like kinase 1 (PLK1) with volasertib shows promise, especially combined with immunotherapy.
Area of Science:
- Oncology
- Cancer Biology
- Immunology
Background:
- Undifferentiated pleomorphic sarcoma (UPS) is a common soft tissue sarcoma (STS) with limited therapeutic options due to a lack of identified driver mutations.
- Tumor suppressors are critical in understanding STS pathogenesis and developing new treatments.
Purpose of the Study:
- To identify novel tumor suppressors involved in UPS development.
- To investigate the therapeutic potential of targeting identified vulnerabilities in BAP1-deficient STS.
Main Methods:
- Utilized an in vivo CRISPR/Cas9 screen in mice to identify tumor suppressors in STS.
- Performed integrative analyses including RNA sequencing, multiplex immunohistochemistry, and flow cytometry.
- Conducted functional studies and pharmacologic inhibition of polo-like kinase 1 (PLK1) using volasertib in mouse models.
Main Results:
- Identified BRCA1-associated protein 1 (BAP1) as a key tumor suppressor in STS.
- Bap1-deficient sarcomas displayed an immunosuppressive tumor microenvironment.
- Reduced BAP1 and elevated PLK1 expression were observed in human UPS.
- PLK1 inhibition with volasertib suppressed tumor growth; combination with anti-PD-1 therapy improved efficacy.
Conclusions:
- PLK1 is essential for the growth of BAP1-deficient sarcomas and represents a therapeutic vulnerability.
- Combined PLK1 inhibition and immune checkpoint blockade warrant further investigation for treating a subset of STS.
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