Abstract
The presence of tumor-infiltrating lymphocytes (TILs) in the tumor microenvironment has been associated with clinical characteristics and prognosis in various cancers, although the role of TILs in sarcoma is unclear. Adult soft tissue sarcomas are a heterogeneous group of tumors that would benefit from the identification of new prognostic markers and novel therapeutic strategies. The purpose of this study was to determine whether there are specific subgroups of soft tissue sarcomas that contain TILs and/or express immune checkpoint proteins, and if so, the clinical importance. We performed immunohistochemistry (IHC) on sections from 99 tumors and found that certain soft tissue sarcomas such as leiomyosarcoma and liposarcoma exhibit little or no immune infiltrate and immune checkpoint proteins. In contrast, a subset of undifferentiated pleomorphic sarcomas (UPS) and myxofibrosarcomas contain TILs and express PD-L1 and PD-1. Evaluation of expression of PD-L1 by IHC has been controversial; however, we observed a significant positive correlation comparing the levels of PD-L1 determined by IHC on tumor sections and RT-qPCR of mRNA from quick frozen primary tumors. We detected PD-L1 expression in a well-characterized group of osteosarcomas in addition to UPS and myxofibrosarcoma. We are now integrating data from RNA-sequencing and next-generation sequencing to investigate the molecular differences in tumors with and without PD-L1 expression. These studies suggest that there may be individuals with specific sarcomas who may be good candidates to benefit from immunotherapies targeting PD-L1/PD-1 based on their tumor characteristics.
Citation Format: Irene L. Andrulis. Variation in the immune cell infiltrate and expression of PD-L1 in sarcoma subtypes [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr IA23.
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