Abstract 454: Uniform TIM 3 and galectin 9 positivity on immunohistochemistry staining of tumor specimen at diagnosis in pediatric patients with Ewing sarcoma
Authors: Si Stephanie J. , Barrett David , Wertheim Gerald 
Published: September 2020

Abstract
Immune checkpoint blockade have gained substantial interest in the past decade. Adult studies have shown that the location, density, and cell type that express negative checkpoint receptors (NCRs) such as PD 1, TIM 3, LAG 3 and their respective ligands PD L1, Galectin 9, MHC class II vary between and within tumor types. However, our understanding of the onco immunologic landscape in pediatric solid tumors remains limited, with studies to date mainly focusing on the expression of PD 1 and PD L1 within the center of tumors and results have been mixed. Furthermore, LAG 3 and TIM 3 have shown great promise in adult cancer therapy, but availability of such clinical trials have not progressed to pediatric patients as the preclinical data of NCR expression in pediatric tumors is not well characterized.
We performed immunohistochemistry staining for PD 1/PD L1, TIM 3/Galectin 9, LAG 3/MHC class II on 26 diagnostic tumor samples from pediatric patients with non Hodgkin lymphoma (NHL), Ewing sarcoma, and osteosarcoma. As with adult tumors, both NCR and ligand expression varied significantly between and within tumor types. One notable finding was uniform positivity of TIM 3 and Galectin 9 on tumor infiltrating lymphocytes (TILs) in Ewing sarcoma specimens (see Table 1). Comparison of NCR/ligand expression of TILs versus peripheral blood T cells showed no correlation within individual patients. Of note, a higher percentage of peripheral T cells from NHL patients showed expression of all three NCRs (8.6%) compared to Ewing sarcoma (1.6%) and osteosarcoma (0.38%) patients, suggesting a higher degree of T cell exhaustion. In this data set, peripheral blood T cells did not reflect the tumor environment at diagnosis limiting this parameter's prognostic value. Our translational data suggest further investigation of TIM 3 and Galectin 9 for checkpoint blockade in future pediatric solid tumor clinical trials.
Table 1.Distribution of NCRs and ligands PD 1/PD L1, TIM 3/Galectin 9, LAG 3/MHC Class II on TILs in (A) Ewing sarcoma (B) Osteosarcoma (C) NHL tissue samples at diagnosis.Distribution of NCRs/ligands on TILs in Ewing, Osteo, and NHL diagnostic samplesEwingPD 1TIM 3LAG 3++/--++/--++/--1/103/106/1010/100/100/100/100/1010/10PD L1Galectin 9MHC Class II++/--++/--++/--0/101/109/1010/100/100/1010/100/100/10OsteoPD 1TIM 3LAG 3++/--++/--++/--0/81/87/85/81/82/80/80/88/8PD L1Galectin 9MHC Class II++/--++/--++/--0/80/88/85/80/83/88/80/80/8NHLPD 1TIM 3LAG 3++/--++/--++/--7/81/80/83/83/82/84/84/80/8PD L1Galectin 9MHC Class II++/--++/--++/--3/83/82/86/82/80/84/82/82/8
Citation Format: Stephanie J. Si, David Barrett, Gerald Wertheim. Uniform TIM 3 and galectin 9 positivity on immunohistochemistry staining of tumor specimen at diagnosis in pediatric patients with Ewing sarcoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 454.