AUTHOR=Coto-Llerena Mairene , Ercan Caner , Kancherla Venkatesh , Taha-Mehlitz Stephanie , Eppenberger-Castori Serenella , Soysal Savas D. , Ng Charlotte K. Y. , Bolli Martin , von Flüe Markus , Nicolas Guillaume P. , Terracciano Luigi M. , Fani Melpomeni , Piscuoglio Salvatore 

TITLE=High Expression of FAP in Colorectal Cancer Is Associated With Angiogenesis and Immunoregulation Processes

JOURNAL=Frontiers in Oncology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2020.00979

DOI=10.3389/fonc.2020.00979

ISSN=2234-943X

ABSTRACT=<p>Fibroblast activation protein α (FAP) plays an important role in tissue remodeling and helps tumor cells invade surrounding tissue. We sought to investigate FAP as a prognostic molecular marker in colorectal cancer (CRC) using immunohistochemical and transcriptomic data. <italic>FAP</italic> expression and clinicopathological information were obtained from The Cancer Genome Atlas data set. The association of <italic>FAP</italic> expression and tissue cellular heterogeneity landscape was explored using the xCell method. We evaluated FAP protein expression in a cohort of 92 CRCs and 19 non-tumoral tissues. We observed that <italic>FAP</italic> was upregulated in tumors both at the mRNA and protein levels, and its expression was associated with advanced stages, poor survival, and consensus molecular subtype 4. <italic>FAP</italic> expression was also associated with angiogenesis and collagen degradation. We observed an enrichment in immune-cell process–related genes associated with <italic>FAP</italic> overexpression. Colorectal cancers with high <italic>FAP</italic> expression display an inflamed phenotype enriched for macrophages and monocytes. Those tumors showed enrichment for regulatory T cell populations and depletion of T<sub>H</sub>1 and natural killer T cells, pointing to an immunosuppressive environment. Colorectal cancers with high levels of stromal FAP are associated with aggressive disease progression and survival. Our results suggest that FAP plays additional roles in tumor progression such as modulation of angiogenesis and immunoregulation in the tumor microenvironment.</p>