Cancer Growth and Invasion Are Increased in the Tight Skin (TSK) Mouse

<b>Background</b>: Patients with systemic sclerosis have a significantly increased incidence of developing various solid malignancies within a few years of systemic sclerosis onset, but the mechanism of tumor promotion is not well understood. The tight skin (TSK) mouse has been a valuable model for investigating systemic sclerosis-related pathologies due to increased extracellular matrix deposition, fibrosis in connective tissues, and altered immune cell activation. Despite the role of extracellular matrix and fibrosis in cancer progression, the potential of the TSK mouse as a model for cancer studies is unexplored. <b>Methods:</b> To investigate the impact of the altered microenvironment in TSK mice on cancer progression, we compared the tumor-forming capabilities (by subcutaneous and intraperitoneal injection) in TSK mice and WT mice using syngeneic breast cancer, melanoma, and ovarian cancer cell lines. We used bulk and single-cell RNA sequencing to characterize these tumors and identify the changes in the TSK microenvironment that promote cancer formation. <b>Results:</b> In all three cancer types, TSK mice exhibited more invasive subcutaneous tumors in comparison to WT controls, underscoring the role of the TSK subcutaneous microenvironment in promoting cancer progression. Furthermore, the heightened invasiveness of ovarian tumors implanted intraperitoneally suggests that the peritoneal microenvironment in TSK mice also promotes tumor progression. Single-cell RNA sequencing analyses of subcutaneous tumors from TSK and WT mice revealed tumor-specific changes in the composition and phenotype of various cell populations. The most consistent alteration in TSK mice included a higher neutrophil-to-lymphocyte ratio and an enrichment in profibrotic subpopulations of myofibroblasts and macrophages. <b>Conclusions:</b> Our research unveils the TSK mouse as a valuable model for studying the intricate connections between systemic sclerosis and cancer.