The role of long non‐coding RNA Maternally Expressed Gene 3 in cancer‐associated fibroblasts at single cell pan‐cancer level

Abstract Long non‐coding RNAs (lncRNAs) can crucially regulate activation and transformation of cancer‐associated fibroblasts (CAFs) but have not been systematically investigated at single cell resolution. Here, by utilizing integrated single‐cell sequencing datasets, we screened the aberrantly expressed lncRNAs in CAFs, which are the major component of tumor microenvironment. Our findings revealed a consistent CAF‐specific downregulation of Maternally Expressed Gene 3 (MEG3) expression and increased MEG3 + proportion at the pan‐cancer level, which may be attributed to m6A‐related post‐transcriptional modifications. Through activation trajectory analysis of the major CAF subtypes, it was determined that elevated MEG3 expression in CAFs leads to an increase in PDGFRA expression. This, in turn, promotes CAF activation and transformation into an MEG3 + adipogenic CAF (MACAF) subtype, which is more sensitive to Dasatinib. MACAF‐related cell–cell interactions highlighted that MACAF could enhance the epithelial‐mesenchymal transition process in tumor cells via the TGF‐β pathway, promoting tumor cell migration and possibly contributing to tumor progression and invasiveness. Notably, patients with higher MACAF scores experience unfavorable prognoses and poor response rates to checkpoint inhibitor‐based immunotherapy, suggesting a correlation between MACAF and immunosuppressive microenvironment shaping. Our findings provide novel insights of the MEG3 in CAF activation and highlight the potential value of the MACAF score for therapeutic strategies design involving Dasatinib and immunotherapy.