Analysis of the Tumor Microenvironment By Quantitative Immunohistochemistry Reveals Novel Predictors in Classic Hodgkin Lymphoma Treated with Anti-PD1 Therapy

Classical Hodgkin Lymphoma (cHL) is characterized histologically by the presence of neoplastic Hodgkin and Reed-Sternberg cells surrounded by mixed immune cells. Anti-PD-1 therapy is the principal treatment option for relapsed or refractory cHL. To reveal biomarkers for predicting the cHL patients' responses to immunotherapy, pathological tissues of twenty patients with cHL who have been treated with anti-PD1 therapy were collected. Tumor immune microenvironment was investigated by immunostaining and quantitative measurement of CD68 (for macrophages), CD8 (for cytotoxic T-cells), FoxP3 (for Treg), PD-1, PD-L1 and PD-L2 expression levels. The in situ hybridization for Epstein-Barr virus (EBER-ISH) were also performed. The results showed that the main immune indicators of the tumor microenvironment we had tested were independent of the histological subtypes. Patients who were positive for EBER-ISH had higher mean density of PD-L1 than those were negative for EBER-ISH. Single-factor analysis revealed the high expression of PD-L1 and positive EBER-ISH were associated with significantly increased 2-year PFS in cHL treated with anti-PD1, while CD68, CD8, FoxP3, PD-1 and PD-L2 were not. Therefore, we propose that PD-L1 and EBER-ISH may serve as novel predictors for the treatment outcomes of cHL patients with anti-PD1 therapy.