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posted on 2023-03-31, 03:44 authored by Keshav Karki, Gus A. Wright, Kumaravel Mohankumar, Un-Ho Jin, Xing-Han Zhang, Stephen Safe <p>Supplemental Figure S3. Role of Sp1, Sp3, Sp4 and p300 in PD-L1 expression. MDA-MB-231 and 4T1 cells were transfected with oligonucleotides targeting Sp1 (iSp1) (A), Sp3 (iSp3), Sp4 (iSp4) and p300 (ip300) (B) and whole cell lysates were analyzed by western blots. The Sp3 bands represent the high and low molecular weight bands in descending order.</p>
Funding
NIH
Texas A&M AgriLife Research
Sid Kyle Chair Endowment
History
ARTICLE ABSTRACT
PD-L1 is expressed in tumor cells and its interaction with PD-1 plays an important role in evading immune surveillance; this can be overcome using PD-L1 or PD-1 immunotherapy antibodies. This study reports a novel approach for targeting PD-L1. In human breast cancer cell lines and 4T1 mouse mammary tumor cells, PD-L1 expression was regulated by the nuclear receptor NR4A1/Sp1 complex bound to the proximal germinal center (GC)-rich region of the PD-L1 gene promoter. Treatment of breast cancer cells with bis-indole–derived NR4A1 antagonists including 1,1-bis(3′-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (Cl-OCH3) decreased expression of PD-L1 mRNA, promoter-dependent luciferase activity, and protein. In in vivo studies using a syngeneic mouse model bearing orthotopically injected 4T1 cells, Cl-OCH3 decreased tumor growth and weight and inhibited lung metastasis. Cl-OCH3 also decreased expression of CD3+/CD4+/CD25+/FoxP3+ regulatory T cells and increased the Teff/Treg ratio. Therefore, the potent anticancer activities of NR4A1 antagonists are also accompanied by enhanced antitumor immunity in PD-L1–expressing triple-negative breast cancer and thus represent a novel class of drugs that mimic immunotherapy.
These findings show that the orphan nuclear receptor NR4A1 controls PD-L1 expression and identify a chemical probe capable of disrupting this regulatory axis.
