Matrix Stiffness Transcriptomic Signatures and Immune Exclusion in Pan-Cancer TCGA Data: A Cross-Sectional Analysis (Preprint)

<sec> <title>BACKGROUND</title> <p>Matrix stiffness and ECM crosslinking have been increasingly regarded as major factors contributing to the development of cancer. Preclinical studies indicate that stiff matrices prevent the infiltration of CD8⁺ T cells and lead to immunosuppression. However, the question of whether similar transcriptional markers are present in human cancers has not yet been addressed.</p> </sec> <sec> <title>OBJECTIVE</title> <p>We aimed to determine whether transcriptional programs of matrix stiffness are associated with CD8⁺ T cell infiltration and immune exclusion across human cancers, and to assess whether these associations are independent of stromal content.</p> </sec> <sec> <title>METHODS</title> <p>9,562 tumor samples from 32 types of TCGA cancers underwent pan-cancer analysis. The LOX/collagen stiffness signature formed by a set of 9 genes and the broader mechanotransduction signature formed by 73 genes were computed. The immune infiltration was estimated using Ayers GEP obtained from 18 genes and the CD8⁺ T cell effector signature. The ESTIMATE method for calculating stromal and immune scores was employed to obviate the need for making adjustments. The Spearman method, partial correlation, Cox proportional hazards, and random effects analysis were applied in the study.</p> </sec> <sec> <title>RESULTS</title> <p>The results obtained revealed that stiffness was positively and significantly associated with the extent of immune infiltration. Nevertheless, after controlling for stromal scores, the LOX/collagen-immune associations dropped to zero, even though statistical significance was still maintained at such a large sample size. The broader mechanotransduction signature demonstrated a sustainable association with immune infiltration, which did not depend on the stromal score. Both indices were capable of predicting the worst survival outcomes in patients with cancer. Further tests confirmed the extreme heterogeneity of the obtained results.</p> </sec> <sec> <title>CONCLUSIONS</title> <p>The hypothesis according to which stiffness signatures are connected with immune-excluded tumors was disproven. Instead, LOX/collagen stiffness signatures could be considered as indicators of the immune infiltration level.</p> </sec>