In silico analyses of the tumor microenvironment highlight tumoral inflammation, a Th2 cytokine shift and a mesenchymal stem cell-like phenotype in advanced in basal cell carcinomas.

Abstract

Basal Cell Carcinoma (BCC) represents the most common form of all cancers. BCC is characteristically surrounded by a fibromyxoid stroma. Previous studies have suggested a shift towards a Th2 response, an increase in T regulatory lymphocytes and the presence of cancer-associated fibroblasts in the BCC tumor microenvironment. In this study, we aimed to further characterize the BCC tumor microenvironment in detail by analyzing BCC RNA-Sequencing data and correlating it with clinically-relevant features via in silico RNA deconvolution. Using immune cell type deconvolution by CIBERSORT, we have identified a brisk lymphocytic infiltration, and more abundant macrophages in BCC tumors compared to normal skin. Using cell type enrichment by xCell, we confirmed the observed immune infiltration in BCC tumors and compared them to normal skin. We observed a shift towards Th2 immunity in advanced and vismodegib-resistant tumors. Tumoral inflammation induced by macrophage activity was associated with advanced BCCs, while lymphocytic infiltration was most significant in non-advanced tumors, likely related to an adaptive anti-tumoral response. In advanced and vismodegib-resistant BCCs, mesenchymal stem cell-like properties were observed. Particularly in vismodegib-resistant BCCs, fibroblasts and adipocytes were found at high number, which ultimately may contribute to the decreased drug delivery to the tumor. In conclusion, this study has revealed notable BCC tumor microenvironment findings associated with important clinical features. Microenvironment-altering agents may be used locally for "routine" BCCs and systematically for advanced or resistant BCCs.