Programmed death-ligand 1 (PD-L1) expression in pheochromocytoma.

Abstract

537 Background: Programmed cell death ligand-1 (PD-L1) is a key target molecule of immunotherapy that is frequently overexpressed in several neoplasms. But there were few reports about PD-L1 expression of pheochromocytoma. In the present study, we examined PD-L1 expression in pheochromocytoma. Methods: PD-L1 mRNA expression was compared across 184 pheochromocytoma, 492 prostate cancer cases and 404 bladder cancer cases based on The Cancer Genome Atlas (TCGA). Furthermore, we enrolled 32 pheochromocytoma patients treated with surgery at our hospital between June 2005 and February 2016. We conducted an immunohistochemistry (IHC) of PD-L1 using the SP142 assay. PD-L1 expression was scored at three diagnostic levels (0/1/2). Results: Comparison of PD-L1 mRNA expression based on the TCGA revealed that PD-L1 expression was significantly higher in pheochromocytoma than in bladder cancer and in prostate cancer (p < 0.001). In the SP 142 assay of our 32 pheochromocytoma, the prevalence of positive PD-L1 expression (IHC score 1 or 2 (1/2)) in tumor-infiltrating immune cells (TICs) was 8 patients (25%). The prevalence of positive PD-L1 expression in tumor cells (TCs) was 9 patients (28.1%). Tumor diameter of PD-L1 (+) in TICs patients was 3.36±0.35 cm and that of PD-L1 (-) in TCs patients was 5.37±0.50cm, there was statistically significance between two groups. (unpaired t test: p=0.044) In our cohort, there were two malignant pheochromocytoma. But there were not PD-L1 positive cases in malignant pheochromocytoma. Conclusions: PD-L1 expression is relatively high in pheochromocytoma compared to bladder cancer and prostate cancer based on TCGA. In the SP142 assay of our 32 pheochromocytoma cases, tumor diameter of PD-L1 (-) in TICs cases was larger than that of PD-L1 (+) cases. In our cohort, there were not PD-L1 (+) cases in malignant pheochromocytoma. These findings suggest that PD-L1 expression of pheochromocytoma was comparatively common and PD-L1 positive expression of pheochromocytoma may not be associated with tumor aggressiveness.