Plasma soluble programmed death ligand 1 levels predict clinical response in peripheral T‐cell lymphomas

Immune checkpoints, including PD‐1/PD‐L1, play an important role in immunosuppression in various malignancies. Elevated levels of soluble programmed death ligand 1 (sPD‐L1) are associated with worse prognosis in multiple myeloma and diffuse large B cell lymphoma. Herein, the purpose of this study is to investigate the relationships between plasma sPD‐L1 levels and clinical response in peripheral T‐cell lymphoma (PTCL) patients. A total of 37 PTCL patients and 20 healthy volunteers were enrolled. Peripheral blood from patients was collected prior to systemic therapy. Plasma levels of sPD‐L1 and IFN‐γ were measured by enzyme‐linked immunosorbent assay (ELISA). PD‐L1 expression in tissues was detected by immunohistochemistry (IHC). Clinical response for patients was evaluated. ONCOMINE database analyses showed that PD‐L1 mRNA expression was significantly upregulated in PTCLs. The median sPD‐L1 level was 0.729 ng/mL for 20 healthy volunteers and 1.696 ng/mL for 37 PTCL patients which was significantly higher than that in healthy volunteers (0.000). The sPD‐L1 level was positively correlated with IFN‐γ level (0.000, r = 0.849) and was also positively associated with clinical staging (0.045), LDH level (0.003), and β2‐MG level (0.045). Patients with high sPD‐L1 level had lower overall response rate than those with low sPD‐L1 level (88.9% vs 50.0%, 0.022) and tended to have poorer PFS and OS. PD‐L1 expression in tissues matched very well with the sPD‐L1 level in PTCL patients. In conclusion, PTCL patients had higher sPD‐L1 level compared with healthy volunteers. High sPD‐L1 level was correlated with worse clinical response, suggesting that sPD‐L1 level was an underlying plasma biomarker to predict the prognosis for PTCL patients.