PD-L1 expression in peripheral T-cell lymphomas is not related to either PD-L1 gene amplification or rearrangements

Nodal peripheral T-cell lymphomas (n-PTCL) are aggressive lymphomas with no specific treatment. Programmed death 1 (PD-1) inhibits T-cell activation and proliferation, and the expression of its ligand PD-L1 has been associated with worse prognosis in some tumors. We performed immunohistochemistry for PD-1, p-STAT3, and PD-L1 (Clones SP142/263/22C3/28.8) and FISH studies for PD-L1/2 genes in chromosome 9p in a series of 168 formalin-fixed, paraffin-embedded n-PTCL samples. PD-L1 (clone 263) was the most frequently detected in both tumor cells (especially in the ALCL subgroup) and the microenvironment (especially in the AITL subgroup). In five ALCL cases, 3-4 copies of the two loci of chromosome 9 were found, suggestive of polyploidy. PD-L1 correlated with p-STAT3 on tumor cells. PD-1 expression in tumor cells was related to expression of PD-L1 in microenvironment. The expression of PD-L1 on tumor cells or microenvironment suggests that some n-PTCL cases might benefit from immune check-point modulation therapy.

Automated summary

In this study, immunohistochemistry and FISH studies were conducted on n-PTCL samples to investigate the expression of PD-1, p-STAT3, and PD-L1, as well as genetic abnormalities of chromosome 9p. PD-L1 (clone 263) was most commonly detected in both tumor cells and the microenvironment, with some cases showing polyploidy in chromosome 9. PD-L1 expression correlated with p-STAT3 in tumor cells, while PD-1 expression was associated with PD-L1 expression in the microenvironment. Overall, the presence of PD-L1 on tumor cells or in the microenvironment suggests potential benefits of immune check-point modulation therapy in some n-PTCL cases.