Blockade of programmed death-ligand 1 (PD-L1) by therapeutic antibodies has shown to be a promising strategy in cancer therapy, yet clinical response in many types of cancer, including prostate cancer (PCa), is limited. Tumor cells secrete PD-L1 through exosomes or splice variants, which has been described as a new mechanism for the resistance to PD-L1 blockade therapy in multiple cancers, including PCa. This suggests that cutting off the secretion or expression of PD-L1 might improve the response rate of PD-L1 blockade therapy in PCa treatment. Here we report that p300/CBP inhibition by a small molecule p300/CBP inhibitor dramatically enhanced the efficacy of PD-L1 blockade treatment in a syngeneic model of PCa by blocking both the intrinsic and IFN-γ-induced PD-L1 expression. Mechanistically, p300/CBP could be recruited to the promoter of CD274 (encoding PD-L1) by the transcription factor IRF-1, which induced the acetylation of Histone H3 at CD274 promoter followed by the transcription of CD274. A485, a p300/CBP inhibitor, abrogated this process and cut off the secretion of exosomal PD-L1 by blocking the transcription of CD274, which combined with the anti-PD-L1 antibody to reactivate T cells function for tumor attack. This finding reports a new mechanism of how cancer cells regulate PD-L1 expression through epigenetic factors and provides a novel therapeutic approach to enhance the efficacy of immune checkpoint inhibitors treatment.
|Number of pages
|Published - May 7 2020
Bibliographical noteFunding Information:
Acknowledgements This work was supported by NIH grants R01 CA157429 (XL), R01 CA192894 (XL), R01 CA196835 (XL), and R01 CA196634 (XL). The work was also supported by Biospecimen Procurement and Translational Pathology, Biostatistics and Bioinfor-matics, Flow Cytometry and Immune Monitoring Shared Resources of the University of Kentucky Markey Cancer Center (P30CA177558). We thank Heather Russell-Simmons at Research Communications Office of Markey Cancer Center for proof-reading of the paper.
© 2020, The Author(s), under exclusive licence to Springer Nature Limited.
ASJC Scopus subject areas
- Molecular Biology
- Cancer Research