A study showed a notable link between programmed cell death 1 (PD-1) as well as indoleamine 2,3-deoxygenase (IDO1) in the development of primary diffuse large B-cell lymphoma of the central nervous system (PCNSL). The study appeared in the journal Acta Oncologica.
To conduct this study, researchers used 45 cases of PCNSL to construct tissue microarrays. They noted that RNA extraction from whole tissue sections and RNA sequencing were successfully performed in 33 cases. Subsequently, they assessed immunohistochemical staining for PD-1, PD-L1/paired box protein 5 (PAX-5), PD-L2/PAX-5 and IDO1, and Epstein-Barr virus encoding RNA.
Following analysis, the researchers observed a high-proportions of PD-L1 and PD-L2 positive tumor cells in 11% and 9% of cases, respectively. Also, the results showed high levels of PD-L1 and PD-L2 positive leukocytes in 55% and 51% of cases, respectively. The researchers noted that RNA sequencing revealed that gene expression of IDO1 was high in patients with high proportion of PD-L1 positive leukocytes (P=0.01).
“Our study shows a significant association between gene and protein expression of IDO1 and protein expression of PD-L1 in the tumor microenvironment of PCNSL, possibly of importance for prediction of response to immunotherapies,” the researchers concluded.