Abstract 990: Immune-suppressive tumor microenvironment leads to poor survival following curative intent surgical resection in soft-tissue sarcomas

Surgical resection of early stage soft-tissue sarcomas (STS) is a potentially curative treatment; however, many STS tumors will recur. Predicting recurrence and survival outcomes for patients with early stage STS remains a challenge. In this study, we identify prognostic biomarkers from clinical and transcriptomic data form a large set of early stage STS. Primary tumor samples from 69 subjects with STS were sequenced using the Tempus xT targeted DNA and whole transcriptome next-generation sequencing platforms. The most common histologies included were liposarcoma (n=22), gastrointestinal stromal tumor (n=19), and leiomyosarcoma (n=12). As expected, high-grade tumors were associated with decreased DFS and OS times while tumor histology was only correlated with OS. Single sample gene set enrichment analysis (ssGSEA) values for seven Hallmark genesets were correlated with both DFS and OS; including pro-tumor survival pathways (p53, Apoptosis, TNF-α via NF-κB), tumor proliferation pathways (MTORC1, MYC Targets, Mitotic Spindle), and UV Response signaling. These pathways are associated with tumor proliferation as well as an immunosuppressive tumor microenvironment (TME). To assess the TME of these tumors we estimated immune cell infiltration using CIBERSORTx. Of the 22 cell types accounted for by CIBERSORTx, only elevated infiltration of M2 Macrophages were associated with poor DFS and OS. To further determine TME activation we assessed the expression of 74 known immune response associated genes. Only PDCD1 (PD-1) was associated with reduced DFS and OS times. Clustering on the nine variables identified here to correlate with both DFS and OS revealed two distinct clusters demonstrating similar histologies. While histologies were similar across clusters, cluster 2 exclusively included high-grade tumors while cluster 1 was made up of 57.4% high-grade tumors. Sub-classifying cluster 1 into low and high-grade subgroups demonstrated a stepped biomarker expression pattern associated with both tumor grade and cluster membership. Using established TME genesets, high-grade tumors demonstrated higher tumor proliferative scores than low-grade tumors, while cluster 2 tumors demonstrated increased tumor associated macrophage signaling. In a multivariable model, cluster membership outperformed tumor grade and histology as the only significant predictor of DFS or OS. Taken together, while tumor grade is a strong predictor of clinical outcomes following surgical resection in STS, immunosuppressive signaling patters may help to identify patients at the highest risk. Citation Format: Nathan David Seligson, Yan W. Asmann, Tariq Almerey, Steven Attia, Sanjay P. Bagaria. Immune-suppressive tumor microenvironment leads to poor survival following curative intent surgical resection in soft-tissue sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 990.