Analysis of the intratumoral adaptive immune response in well differentiated and dedifferentiated retroperitoneal liposarcoma

Abstract

Treatment options are limited in well differentiated (WD) and dedifferentiated (DD) retroperitoneal liposarcoma. We sought to study the intratumoral adaptive immune response and explore the potential feasibility of immunotherapy in this disease. Tumor-infiltrating lymphocytes (TILs) were isolated from fresh surgical specimens and analyzed by flow cytometry for surface marker expression. Previously reported immune cell aggregates known as tertiary lymphoid structures (TLS) were further characterized by immunohistochemistry. In all fresh tumors, TILs were found. The majority of TILs were CD4 T cells; however cytotoxic CD8 T cells were also seen (average: 20% of CD3 T cells). Among CD8 T cells, 65% expressed the immune checkpoint molecule PD-1. Intratumoral TLS may be sites of antigen presentation as DC-LAMP positive, mature dendritic cells were found juxtaposed next to CD4 T cells. Clinicopathologic correlation, however, demonstrated that presence of TLS was associated with worse recurrence-free survival in WD disease and worse overall survival in DD disease. Our data suggest that an adaptive immune response is present in WD/DD retroperitoneal liposarcoma but may be hindered by TLS, among other possible microenvironmental factors; further investigation is needed. Immunotherapy, including immune checkpoint blockade, should be evaluated as a treatment option in this disease.

Figure 1

Tumor-infiltrating lymphocytes or TILs in WD/DD retroperitoneal liposarcoma. (a) Representative analysis by flow cytometry with gating schema for identification of CD3, CD4, and CD8 T cells. (b) Immunohistochemistry demonstrating intratumoral presence of CD8 T cells (brown), 400x magnification.

Figure 2

Expression of PD-1 and 4-1BB among the TIL CD8 population.

Figure 3

Intratumoral tertiary lymphoid structures (TLS) in WD/DD retroperitoneal liposarcoma. (a) General histologic appearance of TLS with varying levels of complexity and size, 100x magnification. (b) Immunohistochemistry for DC-LAMP (brown dots), a marker for mature dendritic cells, CD4 (red) and CD8 (green). Green boxes denote areas with DC-LAMP positive cells. 400x magnification. (c) Clinical outcome for patients with and without intratumoral TLS with recurrence-free survival (RFS) and overall survival (OS) shown.

Figure 4

Summary of the intratumoral adaptive immune response in WD/DD retroperitoneal liposarcoma and the potential clinical utility of immune checkpoint blockade. Brown circles = tumor cell, yellow squiggle = tumor antigen, purple shapes = dendritic cell (DC), and green circles = T cell; TLS = tertiary lymphoid structure; TCR = T cell receptor; MHC = major histocompatibility complex.