Abstract A007: Resident memory T cells express PD-1 in high grade liposarcoma

Abstract Objective: Memory T cells play crucial roles in anti-tumor immunity. Tumor-associated resident memory T cells (TRM) have been associated with durable immune response and improved patient survival across multiple tumor types. SARC028, a phase II, multicenter trial of pembrolizumab, a programmed death 1 (PD-1) checkpoint inhibitor immunotherapy, showed promising activity in select histologic subtypes of advanced soft tissue sarcoma (STS), including dedifferentiated liposarcoma (DDLPS). However, there was only a 20% overall response rate. Notably, the patients who did respond to immunotherapy had durable responses, supporting our enthusiasm to understand the potential role for TRM in liposarcoma anti-tumor immunity. The characterization of memory T cells in liposarcoma, and whether TRM are present has not been explored. Design: Fresh retroperitoneal liposarcoma specimens from 8 patients: 3 well-differentiated liposarcoma (WDLPS) and 5 DDLPS were collected. Lymphocytes were analyzed by flow cytometry using T-cell (CD45, CD3, CD4, CD8) and phenotypic markers (CD69, CD62L, CD103, CD49a, PD-1, TIM-3). Results: DDLPS had a 4-fold higher overall T-cell infiltration and a 2.5-fold higher CD8+/CD4+ T-cell ratio than WDLPS. DDLPS contained CD8+ T cells with a CD45RA− CCR7− CD69hi CD62Llo phenotype, characteristic of a TRM response, and well as CD69lo effector memory T (TEM) cells. DDLPS had 3-fold more TRM than WDLPS. DDLPS had a much higher level of activated PD-1+ CD69+ CD8+ resident memory T-cell population compared to WDLPS. Additionally, the population of TRM had higher PD-1 expression compared to TEM in both DDLPS and WDLPS. Conclusions: These data suggest that TRM subsets may contribute to the responsiveness to anti-PD1 therapy in patients with DDLPS. Further investigations may lead to the discovery of TRM-targeted T-cell therapies in DDLPS, which currently has limited treatment options. Citation Format: Christina V. Angeles, Jichang Han, Jodi Wilkoswki, Scott Bresler. Resident memory T cells express PD-1 in high grade liposarcoma [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A007.