Abundance of immune checkpoint molecules and their ligands in Oropharyngeal Squamous cell carcinoma (OPSCC) depends on HPV status and can be modulated by demethylation.

Introduction Immune checkpoint molecules (ICM) regulate immune cell functions and anti-cancer immunity. ICM expression within the tumor microenvironment (TME) may differ by HPV-status. Decitabine (DAC), a nucleoside analogue, causes unspecific DNA demethylation resulting in increased expression of cancer testis antigens, potentially enhancing immunogenicity. Systemic DAC may also impact immune cells in the microenvironment and the periphery. Here, we aim at characterizing ICM expression in the TME and effects of DAC on ICM ligands in cancer cells.

Material & Methods RNA of 13 HPV+ and 12 HPV- OPSCC was extracted. Whole exome sequencing of RNA was performed (40 Mio reads). In addition, RNA from three HPV+ (UD-SCC-2, UM-SCC-47, UPCI-SCC:90) and three HPV- OPSCC cell-lines (UD-SCC-1, UD-SCC-4, UD-SCC-5) was extracted after treatment with DAC (2µmol/l) or control (DMSO) for five consecutive Days. Expression data of ICM and their ligands were compared using Mann-Whitney U test (OPSCC samples by HPV-status) or paired Wilcoxon signed rank test (cell lines).

Results ICM ligand expression in the TME was significantly altered for PVR (p<0.001), ICOSL, Galectin-9 and IGSF11 (p<0.05). After DAC treatment, the following ICM ligands with inhibitory or stimulatory potential showed increased expression: PD-L1, CEACAM1, PVRL2, PVR, TNFRSF14, 4-1BBL, CD27L, GITRL (p<0.05).

Discussion Expression of ICM and their ligands in the TME tends to be higher in HPV-positive OPSCC indicating an inflamed phenotype. DAC affects both, the expression of stimulatory and inhibitory ICM ligands in cancer cell lines. The functional impact of these effects needs to be analyzed further.

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Publication History

Article published online:
10 June 2020