Feng, YongShen, JacsonGao, YanLiao, YunfeiCote, GregoryChoy, EdwinChebib, IvanMankin, HenryHornicek, FrancisDuan, Zhenfeng2015-08-032015Feng, Yong, Jacson Shen, Yan Gao, Yunfei Liao, Gregory Cote, Edwin Choy, Ivan Chebib, Henry Mankin, Francis Hornicek, and Zhenfeng Duan. 2015. “Expression of programmed cell death ligand 1 (PD-L1) and prevalence of tumor-infiltrating lymphocytes (TILs) in chordoma.” Oncotarget 6 (13): 11139-11149.1949-2553http://nrs.harvard.edu/urn-3:HUL.InstRepos:17820945Chordomas are primary malignant tumors of the notochord that are resistant to conventional chemotherapy. Expression of programmed cell death ligand 1 (PD-L1), prevalence of tumor-infiltrating lymphocytes (TILs), and their clinical relevance in chordoma remain unknown. We evaluated PD-L1 expression in three chordoma cell lines and nine chordoma tissue samples by western blot. Immunohistochemical staining was performed on a chordoma tissue microarray (TMA) that contained 78 tissue specimens. We also correlated the expression of PD-L1 and TILs with clinical outcomes. PD-L1 protein expression was demonstrated to be induced by IFN-γ in both UCH1 and UCH2 cell lines. Across nine human chordoma tissue samples, PD-L1 protein was differentially expressed. 94.9% of chordoma samples showed positive PD-L1 expression in the TMA. The expression score of PD-L1 for metastatic chordoma tumors was significant higher as compared with non-metastatic chordoma tumors. Expression of PD-L1 protein significantly correlates with the presence of elevated TILs, which correlates with metastasis. In summary, our study showed high levels of PD-L1 are expressed in chordoma, which is correlated with the prevalence of TILs. The current study suggests targeting PD-L1 may be a novel immunotherapeutic strategy for chordoma clinical trials.en-USPD-L1TILschordomaimmunotherapyJournal Article2015-08-03