PD-L1 (CD274) promoter hypomethylation predicts immunotherapy response in metastatic urothelial carcinoma

ABSTRACT

PD-L1 status assessed by immunohistochemistry (IHC) has failed to reliably predict outcomes for patients with metastatic urothelial carcinoma (mUC) on immune checkpoint blockade (ICB). PD-L1 promoter methylation is an epigenetic mechanism that has been shown to regulate PD-L1 mRNA expression in various malignancies. The aim of our present study was to evaluate the predictive potential of PD-L1 promoter methylation status (mPD-L1) in ICB-treated mUC compared to conventional IHC-based PD-L1 assessment. We quantified mPD-L1 in formalin-fixed and paraffin-embedded tissue sections using an established quantitative methylation-specific PCR assay (qMSP) in a well-characterized multicenter ICB-treated cohort comprising N = 107 patients with mUC. Additionally, PD-L1 protein expression in tumor tissues was assessed using regulatory approved IHC protocols. The effect of pharmacological hypomethylation by the DNA methyltransferase inhibitor decitabine in combination with interferon-γ stimulation in urothelial carcinoma cell lines was investigated by IHC and FACS. mPD-L1 hypomethylation predicted objective response rate at the first staging on ICB. Patients with tumors categorized as PD-L1 hypomethylated (lower quartile) showed significantly prolonged progression-free (PFS) and overall survival (OS) after ICB initiation. In contrast, PD-L1 protein expression status neither correlated with response nor survival. In multivariable Cox regression analyses, PD-L1 promoter hypermethylation remained an independent predictor of unfavorable PFS and OS. In urothelial carcinoma cell lines, pharmacological demethylation led to an upregulation of membranous PD-L1 expression and an enhanced inducibility of PD-L1 expression by interferon γ. Hypomethylation of the PD-L1 promoter is a promising predictive biomarker for response to ICB in patients with mUC.

KEYWORDS:

• biomarker
• bladder cancer
• CD274
• DNA methylation
• immune checkpoint blockade
• immunotherapy
• metastatic urothelial carcinoma
• PD-L1
• promoter methylation

Acknowledgments

We thank the patients and their families who were subjects of this study.

Disclosure statement

DD owns patents and patent applications on biomarker technologies and methylation of immune checkpoint genes as predictive and prognostic biomarkers (DE 10 2016 005 947.8, DE 10 2015 009 187.5, DE 10 2017 125 780.2, PCT/EP2016/001237). The patents are licensed to Qiagen GmbH (Hilden, Germany). DD is a consultant of Qiagen. The University Hospital Bonn (PI DD) received research funding from Qiagen. RMW is founder and CEO of STRATIFYER Molecular pathology. All other authors declare no conflicts of interest regarding the present study.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request. https://www.sciencedirect.com/science/article/pii/S030228382102056X?via%3Dihub

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/2162402X.2023.2267744

Additional information

Funding

This study was supported by a junior research group funding by the BONFOR Program of the Medical Faculty of the University of Bonn (grant ID 2020-2A-12) to NK, funding from the Else Kröner-Fresenius Foundation (2020_EKEA.129) to ME, the Clinician Scientist program of the IZKF of the FAU (ME), and a Young Clinical Scientist Fellowship of the Bavarian Center for Cancer Research (BZKF) to ME. NK is supported by the Advanced Clinician Scientist Program Bonn (ACCENT) of the Medical Faculty of the University of Bonn – Grant ID 01EO2107. MH is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC2151–390873048.