Abstract
Background: Colorectal cancer (CRC) stands as the most common gastrointestinal malignancy, with the Follistatin-like 1 (FSTL1) gene associated with unfavorable outcomes in diverse cancer forms. Nonetheless, the precise mechanisms through which FSTL1 influences CRC pathogenesis and its associated multi-omics characteristics remain unclear. Methods: This study leveraged RNA sequencing and single-cell RNA sequencing (scRNAseq) data from the Gene Expression Omnibus (GEO) database to scrutinize the expression profile, prognostic significance, and clinicopathological relevance of FSTL1 in colorectal cancer. Gene set enrichment analysis (GSEA) and protein-protein interaction (PPI) network analysis were conducted to delve into the potential biological functions of FSTL1 in colorectal cancer and its associated pathways. The ESTIM algorithm and Tumor Immune Estimation Resource (TIDE) database were utilized to investigate FSTL1 expression in immune cell infiltration and immune checkpoints. Mutation characteristics of FSTL1 were elucidated using the cBioPortal database. The pRRophetic package was employed to identify potential chemotherapeutic drugs targeting FSTL1. Expression levels of FSTL1 in colon cancer and adjacent normal tissues were evaluated using the Human Protein Atlas (HPA) database. Furthermore, single-cell sequencing technology and cell communication were employed to assess the immunogenomic features of FSTL1 in the tumor microenvironment. In vitro experiments were conducted to validate the efficacy of FSTL1. Results: FSTL1 levels were markedly higher in colorectal cancer tissues compared to healthy tissues, correlating significantly with unfavorable patient outcomes. Elevated FSTL1 expression was closely linked to key biological processes including the PI3K pathway, cell adhesion, proliferation, migration, and extracellular matrix remodeling. Furthermore, FSTL1 expression exhibited strong associations with immune cell levels and the tumor immune microenvironment in colorectal cancer. Notably, FSTL1 mutations predominantly comprised missense mutations and displayed significant correlations with various immune checkpoints and low methylation levels. Axitinib emerged as a promising targeted therapeutic option for patients with high FSTL1 expression. Analysis from the HPA database confirmed elevated FSTL1 expression in colorectal tissues compared to adjacent normal tissues. Single-cell sequencing analysis identified stromal cells as the primary source of abundant FSTL1 expression, potentially influencing tumor microenvironment remodeling by myeloid and B cells via the APP-CD74 pathway. Downregulating FSTL1 expression in colon cancer cells suppresses the proliferation, motility, and invasiveness of SW480 and HCT116 colon cancer cells. Conclusion: In summary, the findings of the study indicate that elevated FSTL1 expression could serve as a prognostic biomarker for unfavorable outcomes in colorectal cancer (CRC) diagnosis and may also identify potential targets for immunotherapy in CRC.