Multi-omics analysis unraveling stemness features associated with oncogenic dedifferentiation in 12 cancers.

Tumorigenesis is typically accompanied by cellular dedifferentiation and the acquisition of stem cell-like attributes. However, few studies have comprehensively evaluated the putative relationships between these characteristics and various cancers. Here, we integrated gene expression and DNA methylation quantitative trait loci (cis-eQTL and cis-mQTL) data from the blood to perform multi-omics Mendelian randomization analysis. Our analyses revealed 967 stem cell-associated genes (P < 0.05) and 11,262 methylation sites (P < 0.01) significantly related to 12 cancers. SMAD7 (cg14321542) in colon cancer, IGF2 (cg13508136) in prostate cancer, and FADS1 (cg07005513) in rectal cancer were prioritized as candidate causal genes and regulatory elements. Notably, using cis-eQTL data from the corresponding tissue sites, we detected 16 stem cell-associated genes dramatically causally associated with six cancers (FDR<0.2). The gene THBS3 was particularly common in both blood and stomach tissues and exhibited prognostic significance. Furthermore, it was markedly associated with one microbial metabolic pathway and four immunophenotypes. Functional validation using the ECC12 gastric cancer cell line revealed that the inhibition of its expression could accelerate oxidative phosphorylation and reactive oxygen species production, reduce clonal proliferation ability, and promote the apoptosis of stomach tumor cells. Additionally, based on spatial transcriptomic data from gastrointestinal cancers, the results demonstrated the clusters enriched with the most stem cell-associated genes exhibited significantly enhanced tumor-promoting potency, and the THBS3-expressing cells displayed suppressed oxidative phosphorylation. Overall, this study enhances our understanding of tumorigenic mechanisms and aids in the identification of therapeutic targets.