Abstract B004: Identification of distinct subpopulations of cancer associated fibroblasts in oral squamous cell carcinoma by imaging mass cytometry

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Abstract Background: Although cancer associated fibroblast (CAF) heterogeneity is recognized in oral squamous cell carcinoma (OSCC), the phenotype and role of CAF subpopulations in OSCC is still unknown. Objectives: This study aimed to dissect CAF heterogeneity and spatial location by using imaging mass cytometry on formalin fixed paraffin embedded (FFPE) tissues from primary OSCC. Methods: Imaging mass cytometry (Hyperion technology) was used to identify 24 markers (E-cadherin, EGFR, Ki-67, α-SMA, CD140β, FAP, FSP-1/S100A4, CD90/Thy-1, integrin α-11, collagen-1, tenascin-C, caveolin-1, CD4, CD8a, CD16, CD20, CD68, CD163, FoxP3, granzyme B, CD31, podoplanin, CD146, and YAP-1) in HPV-negative OSCC lesions (n=10). Tissue images were segmented employing the Steinbock framework. Unsupervised clustering of single-cell data was carried out using a bioinformatics pipeline developed in R language. Results: Unsupervised clustering identified several major cell types, with E-cadherin+ cells being the most abundant (30%) and CD146+ being the least abundant cell type (0.62%). Within the immune compartment CD4+ cells were most abundant (11.72%) followed by CD8+ cells (10.6%) and CD68+ cells (10.25%). Cells negative for other major lineage markers and positive for stromal markers were considered as CAFs and they clustered in 6 clusters defined as CAF1 to CAF6. CAF1-3 were high in FAP and CD140β while CAF 4-6 were low expressing FAP and CD140β. CAF1 and 6 expressed high αSMA, while CAF 3 and 5 expressed high collagen-1. CAF6 had high expression of integrin α-11. CAF1 and 3 subtypes were found closer to immune cells whereas CAF2 and 6 were closely located to cancer cells. Conclusions: We identified six distinct subpopulations of CAFs in OSCC by using imaging mass cytometry. Their clinical implications can be further revealed by using this method on larger patient cohorts with FFPE tissues available in diagnostic biobanks. Citation Format: Stian Tornaas, Siren Fromreide, Dimitrios Kleftogiannis, Hans Jørgen Aarstad, Olav K. Vintermyr, Lars Akslen, Harsh Dongre, Daniela Elena Costea. Identification of distinct subpopulations of cancer associated fibroblasts in oral squamous cell carcinoma by imaging mass cytometry [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B004.