PD‐L1 and PD‐1 expression in pediatric post‐transplant Burkitt lymphoma and other monomorphic post‐transplant lymphoproliferative disorders

Abstract

BackgroundPost‐transplant lymphoproliferative disorders (PTLD) develop as a consequence of immune suppression. Programmed death protein 1 (PD‐1), a regulator of host immune activation, binds to programmed death‐ligand 1 (PD‐L1) to suppress the T‐cell immune response. PD‐1/PD‐L1 pathway may play a role in PTLD. The objective was to describe intratumoral expression of PD‐L1 and PD‐1 in pediatric monomorphic PTLD, and assess if density of these cells is associated with progression‐free survival (PFS) and overall survival (OS).ProcedureClinical variables and outcome data were collected on B‐cell monomorphic PTLD treated in Toronto, Canada between 2000 and 2017. Diagnostic area from tumor tissue was identified to count CD3‐positive or PD‐1‐positive cells and CD3‐negative lymphoma B cells or PD‐L1‐positive cells. CD3+, PD‐1+, and PD‐L1+ cell densities were compared between cases of PTLD. OS and PFS were analyzed.ResultsWe identified 25 cases of B‐cell monomorphic PTLD; majority Burkitt lymphoma (32%) and diffuse large B‐cell lymphoma (56%). All cases had CD3+ cells infiltrating the tumor, and median percentage of CD3+ cells was 14% (interquartile range: 6.2%–25%). Twelve cases (48%) had PD‐1+ cell infiltrating (range: 1%–83%) and 13 cases (52%) had no PD‐1+ cells infiltrating. Sixteen cases (64%) had PD‐L1+ cells present; however, there was no PD‐L1 expression on any Burkitt lymphoma tissue. When comparing PD‐1 and PD‐L1 expression, there was no difference in OS or PFS.ConclusionIntratumoral presence of PD‐1+ and PD‐L1+ cells varied in pediatric patients with monomorphic PTLD; however, no relationship to OS and PFS was identified.