The immune landscape of undifferentiated pleomorphic sarcoma

Introduction

Undifferentiated pleomorphic sarcoma (UPS) can be associated with a relatively dense immune infiltration. Immune checkpoint inhibitors (anti-PD1, anti-PDL1, and anti-CTLA4) are effective in 20% of UPS patients. We characterize the immune microenvironment of UPS and its association with oncologic outcomes.

Material and methods

Surgically resected UPS samples were stained by immunohistochemistry (IHC) for the following: tumor-associated immune cells (CD3, CD8, CD163, CD20), immune checkpoints (stimulatory: OX40, ICOS; inhibitory: PD-L1, LAG3, IDO1, PD1), and the adenosine pathway (CD73, CD39). Sections were reviewed for the presence of lymphoid aggregates (LA). Clinical data were retrospectively obtained for all samples. The Wilcoxon rank-sum and Kruskal-Wallis tests were used to compare distributions. Correlations between biomarkers were measured by Spearman correlation. Univariate and multivariate Cox models were used to identify biomarkers associated with overall survival (OS) and disease-free survival (DFS). Unsupervised clustering was performed, and Kaplan-Meier curves and log-rank tests used for comparison of OS and DFS between immune clusters.

Results

Samples analyzed (n=105) included 46 primary tumors, 34 local recurrences, and 25 metastases. LA were found in 23% (n=10/43), 17% (n=4/24), and 30% (n=7/23) of primary, recurrent, and metastatic samples, respectively. In primary UPS, CD73 expression was significantly higher after preoperative radiation therapy (p=0.009). CD39 expression was significantly correlated with PD1 expression (primary: p=0.002, recurrent: p=0.004, metastatic: p=0.001), PD-L1 expression (primary: p=0.009), and CD3+ cell densities (primary: p=0.016, recurrent: p=0.043, metastatic: p=0.028). In recurrent tumors, there was a strong correlation between CD39 and CD73 (p=0.015), and both were also correlated with CD163+ cell densities (CD39 p=0.013; CD73 p<0.001). In multivariate analyses, higher densities of CD3+ and CD8+ cells (Cox Hazard Ratio [HR]=0.33; p=0.010) were independently associated with OS (CD3+, HR=0.19, p<0.001; CD8+, HR= 0.33, p=0.010) and DFS (CD3+, HR=0.34, p=0.018; CD8+, HR=0.34, p= 0.014). Unsupervised clustering of IHC values revealed three immunologically distinct clusters: immune high, intermediate, and low. In primary tumors, these clusters were significantly associated with OS (log-rank p<0.0001) and DFS (p<0.001).

Conclusion

We identified three immunologically distinct clusters of UPS Associated with OS and DFS. Our data support further investigations of combination anti-PD-1/PD-L1 and adenosine pathway inhibitors in UPS.

Abstract 3857: Characterization of immune cell biomarkers in undifferentiated pleomorphic sarcoma

Background: Undifferentiated pleomorphic sarcoma (UPS) are genetically complex sarcomas often showing a relatively higher immune infiltration among sarcomas, and a demonstrated benefit for immunotherapy in a subset of patients. This study characterizes the immune microenvironment of UPS including tumor infiltrating lymphocytes (TILs), as well as immune checkpoint (IC) and related biomarkers.

Methods: We used FFPE surgical resected UPS from 90 patients (43 primary, 28 recurrence and 19 metastasis) placed in a tissue microarray and stained with immunohistochemistry for the following biomarkers: IC (stimulatory: OX40 & ICOS; inhibitory: PD-L1, LAG3, IDO1, & PD1), TILs (CD3 & CD8), monocytes-macrophages (CD163), Adenosine Pathway (CD73 & CD39), and pSTAT3. We scored TIL and IC biomarkers as positive cell densities, and PD-L1, pSTAT3, CD73 and CD39 as percentage of expression in malignant cells. Clinicopathological data and clinical outcome were available for all patients. Spearman correlation was used to assess the correlation between two biomarkers. Cox proportional hazard regression models were used to identify the prognostic biomarkers for overall survival (OS), recurrence-free survival (RFS), and metastasis-free survival (MFS).

Results: In our cohort, PD-L1, pSTAT3, CD73 and CD39 positive expression (cut-off ≥1%) was 19, 73 78 and 68% respectively. These biomarkers were positively correlated with immune infiltrates: CD3 (p=0.013, 0.009, 0.009, &lt;.001), CD8 (p=0.004, 0.016, &lt;.001, &lt;.001) and ICOS (p=0.005, 0.222, 0.007, 0.022). CD73 and CD39 were also positively correlated with both CD163 (p=0.001, &lt;.001) and PD-1 (p=0.012, &lt;.001). In recurrent tumors, smaller tumors had higher CD3, CD8, ICOS and PD-1 (p=0.011, 0.045, 0.013, 0.045). In metastatic tumor, CD163 and OX40 were positively correlated with age (p=0.045, 0.019). OX40 was inversely correlated with tumor size (p=0.04). ICOS positively correlated with PD-1, PD-L1 and CD39 (p&lt;.001, 0.002, 0.003) in primary tumors; with IDO1 and PD1 (p=0.012, &lt;.001) in recurrent tumors; and with PD-L1 expression (p=0.031) in metastatic tumors. Low CD3, CD8, CD163 densities (cut-off median) were associated with inferior OS (HR: 3.19 [1.37, 7.42]; p=0.007), RFS (HR: 2.79 [1.21, 6.42], p=0.016), and MFS (HR: 2.42 [1.05, 5.56]; p=0.038) after adjusting for size, respectively. Low CD73 and PD-L1 (cut-off median) were associated with inferior OS (HR 3.03 [HR: 1.21, 7.61], p=0.018), RFS (HR: 2.59 [1.06, 6.36]; p=0.037), and MFS (HR: 2.43 [1.00, 5.89], p=0.049), respectively.

Conclusions: In this study, we characterized the immune cell infiltrates and the expression of PD-L1, pSTAT3, CD73 and CD39 in UPS. These biomarkers differentially correlated with clinicopathological characteristics in primary, recurrent and metastatic tumors. Lower TILs and low CD73/PD-L1 expression were associated with inferior survival outcomes.

Citation Format: Carmelia M. Barreto, Luisa M. Solis-Soto, Ruth Salazar, Swati Gite, Edwin R. Parra, Barbara Mino, Davis Ingram, Khalida M. Wani, Cheuk H. Leung, Heather Lin, Ignacio I. Wistuba, Alexander Lazar, Wei-Lien Wang. Characterization of immune cell biomarkers in undifferentiated pleomorphic sarcoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3857.