PurposeClinical successes using current T-cell based immunotherapies have been limited in soft tissue sarcomas (STS), while pre-clinical studies have shown evidence of natural killer (NK) cell activity. Since tumor immune infiltration, especially tumor-infiltrating lymphocytes, is associated with improved survival in most solid tumors, we sought to evaluate the gene expression profile of tumor and blood NK and T cells, as well as tumor cells, with the goal of identifying potential novel immune targets in STS.Experimental DesignUsing fluorescence-activated cell sorting, we isolated blood and tumor-infiltrating CD3-CD56+ NK and CD3+ T cells and CD45- viable tumor cells from STS patients undergoing surgery. We then evaluated differential gene expression (DGE) of these purified populations with RNA sequencing analysis. To evaluate survival differences and validate primary DGE results, we also queried The Cancer Genome Atlas (TCGA) database to compare outcomes stratified by bulk gene expression.ResultsSorted intra-tumoral CD3+ T cells showed significant upregulation of established activating (CD137) and inhibitory genes (TIM-3) compared to circulating T cells. In contrast, intra-tumoral NK cells did not exhibit upregulation of canonical cytotoxic genes (IFNG, GZMB), but rather significant DGE in mitogen signaling (DUSP4) and metabolic function (SMPD3, SLC7A5). Tumors with higher NK and T cell infiltration exhibited significantly increased expression of the pro-inflammatory receptor TLR4 in sorted CD45- tumor cells. TCGA analysis revealed that tumors with high TLR4 expression (P = 0.03) and low expression of STMN1 involved in microtubule polymerization (P < 0.001) were associated with significantly improved survival.ConclusionsUnlike T cells, which demonstrate significant DGE consistent with upregulation of both activating and inhibiting receptors in tumor-infiltrating subsets, NK cells appear to have more stable gene expression between blood and tumor subsets, with alterations restricted primarily to metabolic pathways. Increased immune cell infiltration and improved survival were positively correlated with TLR4 expression and inversely correlated with STMN1 expression within tumors, suggesting possible novel therapeutic targets for immunotherapy in STS.

IntroductionSoft tissue sarcomas (STS) are rare, heterogenous malignancies with an unmet need for novel immunotherapies. Tumor infiltrating lymphocytes (TILs) have been linked with favorable outcomes in STS patients, though the contribution of natural killer (NK) cells and spatial relationships of TILs with MHC-I expressing cells lacks detailed characterization.Experimental designUsing archived and prospectively collected specimens, we evaluated intratumoral NK cells by immunohistochemistry (IHC), flow cytometry, and immunofluorescence (IF). We assessed spatial localization of NK and T cells by multiplex IF, analyzing the effects of MHC-I expression status on NK and T cell clustering.ResultsBoth intratumoral NKp46 and CD56dim expression were associated with significantly improved overall survival (P=0.05), while higher infiltrates of CD56bright NK cells predicted a worse prognosis (P=0.05). The presence of intratumoral NK cells was inversely proportional to CD3+ T cells. Spatial analyses showed NK cells preferentially clustering close to other NK cells with sparse CD3+ T and CD8+ T cells in range (P<0.0001). Additionally, CD3+ T and CD8+ T cells showed significantly greater co-localization with MHC-I+ cells, compared to NK cells (P<0.0001). After neoadjuvant radiotherapy, there was greater CD8 clustering, while after neoadjuvant chemotherapy, there was overall lower TIL clustering.ConclusionIntratumoral NK cells are prognostic in STS and localize closer to MHC-I- cells than T cells. Although both NK and T cells are associated with improved survival in STS, their differential distribution in the TME based on MHC-I expression status may serve as a biomarker for improved immunotherapy treatment selection.

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Natural killer (NK) cells have been shown to be important mediators of anti-tumor responses, including in soft tissue sarcomas (STS). NK cells show significant heterogeneity, depending on maturation, tissue residency, and inflammatory environment. As previous studies have suggested that tumor-infiltrating NK cells (TiNKs) acquire a less cytotoxic CD56 brighttissue resident phenotype, we sought to compare blood versus tumor NK cell phenotype in STS and evaluate any association with survival. Blood and tumor from 27 STS patients undergoing surgery from 2018–2022 were collected prospectively for flow cytometry and retrospectively analyzed. 52% were female, the mean age was 59, and 74% were AJCC stage 3. Increasing absolute number of NK cells in the blood correlated with longer survival (P<0.005, r=0.6). As expected, CD56 dimNK cells predominated in the blood (91.5±5.8% of CD3-CD56+ lymphocytes compared to 80.1±13% in tumor, P<0.005). In contrast, CD56 brightcells were enriched in tumor representing 18.5±13% compared to 8.4±5.8% in blood (P<0.005). Although CD56 brightNK cells were approximately 2.4±3-fold higher in tumor compared to blood, CD56 dimNK cells still represented the majority of TiNKs. Higher proportions of both overall NK cells and CD56 dimNK cells in STS tumors were associated with better metastasis-free survival on Kaplan-Meier analysis (P<0.05). CD56 dimTiNKs had higher NKp46 expression than CD56 brights. In conclusion, both blood and intra-tumoral NK cells appear prognostic in STS. Although the proportion of CD56 brightTiNKs in STS is higher than blood the majority of TiNKs are CD56 dimconsistent with a cytotoxic phenotype. Better characterization of NK subsets in STS is likely to have translational significance.