title: Immunological Profiling of Desmoid Tumour Patients under Active Surveillance: Uncovering Biomarkers for Personalized Clinical Strategies
Creators: name: Bergamaschi, Laura
Publisher: name: The Open University
Year: 2025

description: <b>Introduction.</b> Desmoid tumour (DT) is a rare and locally aggressive soft tissue sarcoma of fibroblastic/myofibroblastic origin, characterised by activating mutations in exon 3 of the β-catenin (<i>CTNNB1</i>) gene, with T41A, S45F, and S45P being the most common mutations. Recent studies have shown that approximately 20% of DTs undergo spontaneous regression, while half remain stable. These findings, coupled with the potential risks associated with surgery and a high likelihood of recurrence, have led to a shift in the primary management of DT from surgical intervention to active surveillance (AS), which involves scheduled clinical examinations and MRI/CT monitoring. Unfortunately, around 30% of DTs progress, necessitating local or systemic treatment. The limited understanding of DT biology and immune contexture hinders the identification of prognostic biomarkers essential for optimising and tailoring therapies. The unpredictable behaviour of DT, along with the well-documented relationship between oncogene activation and inflammation—whereby β-catenin may influence the tumour’s inflammatory milieu—suggests a specific role for inflammation and the immune system in DT. In this study, we conducted an in-depth exploration of local and systemic immunity of DT patients using multiple approaches and assessing their associations with clinical features (specific β-catenin mutation and comorbid autoimmunity) and disease outcomes (progression and the need for active treatment).
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<b>Methodology.</b> We conducted an observational study on AS at our institute, prospectively enrolling 56 patients with newly diagnosed primary sporadic DT with measurable disease in various anatomical sites. The mutational status of the <i>CTNNB1</i> gene in the tumour was determined using Sanger sequencing. Next-Generation Sequencing technology was applied in cases Sanger resulted wild-type. Transcriptional profiles of DT biopsies obtained at diagnosis were investigated through targeted and untargeted gene expression profiling analyses using Nanostring and RNAseq technology. Transcriptional data were analysed using bioinformatic tools, including IPA, GSEA, and ssGSEA. The abundance of immune cells infiltrating the tumour was estimated by MCP counter and semi-quantitative assessment of haematoxylin and eosin (H&amp;E)-stained sections. Blood samples taken from patients at DT diagnosis and during AS (every 3 months during the first year and every 6 months during the second year or until the patient required systemic/local therapy) were analysed to investigate the phenotypic and functional characteristics of immune cells using multiparametric flow cytometry. Plasma proteomic profiles were obtained using Luminex and Olink technology. The quantity of cell-free DNA (cfDNA) was evaluated by fluorescence-based assays, and levels of circulating β-catenin-mutated variants (T41A, S45F, S45P) in circulating tumour DNA (ctDNA) were assessed by droplet digital PCR analysis. 
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<b>Results.</b> The transcriptional profile of S45F-mutated DTs, compared to T41A-mutated DTs, shows negative enrichment of gene sets related to immune/inflammatory responses and enrichment of genes associated with Th22 cells and the TGF-β signalling pathway. DTs from patients who experienced tumour progression during AS are characterised by lower expression of gene sets associated with muscle activity and higher expression of TGF-β fibrotic signalling and Th2 signatures compared to patients who experienced regression. DTs from patients with comorbid autoimmunity display higher expression of genes associated with immune/inflammatory response pathways, similar to DTs from patients requiring treatment. 
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Blood immune profiling reveals an increase in myeloid and lymphoid subsets associated with systemic inflammation and immune activation in patients compared to healthy donors. Blood from patients with the S45F mutation shows higher levels of Th22 cells, while those with the T41A mutation present higher percentages of activated monocytes. Patients experiencing disease progression exhibit higher percentages of mature granulocytes, activated lymphocytes, Th1, Th9, and Th17/Th1 cells, and lower percentages of Th2 cells compared to regressing patients. Blood from patients with comorbid autoimmunity shows higher levels of Th9 cells and increased PD-L1 expression on monocytes compared to others. Patients requiring treatment display higher levels of Th17/Th1 and Th9 cells and lower levels of TIM3 expression on CD8+ T cells compared to others.
Higher percentages of Th2 cells are associated with a significant lower probability of progression, both in univariate and multivariate analysis, with ORs of 0.670 and 0.497, respectively. 
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Plasma cytokines, chemokines, and other immune-regulatory molecules, with both pro- and anti-inflammatory functions, are generally downregulated in patients with the S45F mutation, DT progression, and the need for treatment, while they are upregulated in patients with autoimmunity. β-catenin mutations are detectable in 65% of DT plasma samples. Mutated β-catenin levels correlate with tumor size in patients with trunk DTs. In a subgroup patients with higher ctDNA levels (&gt; 0,5 mutated copies/ml), we observed a non-significant association between longitudinal monitoring of ctDNA levels during AS and the observed clinic radiological event.
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<b>Conclusions.</b> In summary, these findings indicate that an altered inflammatory status is present both at the tumour site and in the peripheral blood of DT patients. The immune alterations observed in myeloid and lymphoid cell subsets in the peripheral blood support the hypothesis of the immune system involvement in DT onset and could potentially serve as a marker of disease aggressiveness. The results of the ctDNA analysis further support its potential clinical implementation as a diagnostic tool in specific clinical scenarios where biopsy may be challenging. A prospective clinical trial is necessary to evaluate the potential role of ctDNA as a predictive biomarker.