%0 Journal Article %A TAKAAKI MASUDA %A MIWA NODA %A AKIHIRO KITAGAWA %A QINGJIANG HU %A ATSUSHI FUJII %A SHUHEI ITO %A KEISUKE KOSAI %A YUKI ANDO %A YOSHIHIRO MATSUMOTO %A HAJIME OHTSU %A HIROKI UCHIDA %A SHINJI OHNO %A KOSHI MIMORI %T The Expression Level of PD-L1 (CD274) mRNA in Peripheral Blood Is a Potential Biomarker for Predicting Recurrence in Breast Cancer %D 2020 %R 10.21873/anticanres.14362 %J Anticancer Research %P 3733-3742 %V 40 %N 7 %X Background/Aim: Programmed death-ligand 1 (PD-L1/CD274) elicits T-cell anergy, leading to immune suppression. We aimed to determine the prognostic relevance of PD-L1 expression in the blood of breast cancer (BC) patients. Materials and Methods: We measured PD-L1 mRNA expression in blood and tumor tissues of BC patients using RT-qPCR and a dataset from The Cancer Genome Atlas, and performed a survival analysis of PD-L1 expression in the blood of 330 BC patients. Flow cytometric analysis was performed using blood cells. Results: No statistical difference in PD-L1 expression was seen between normal controls and BC in blood or tissues. There was a significant positive correlation between the PD-L1 expression levels in blood and tissues. Decreased PD-L1 expression in blood or tissues was associated with poor recurrence-free survival. PD-L1 is mainly expressed in polymorphonuclear leukocytes. Conclusion: Low expression of PD-L1 in the blood could serve as a biomarker of poor prognosis in BC patients. %U https://ar.iiarjournals.org/content/anticanres/40/7/3733.full.pdf