CMS4 epithelial-intrinsic glycosyltransferase GALNT5 promotes tumor aggressiveness and correlates with poor survival in colorectal cancer

Abstract

Abstract The “mesenchymal” consensus molecular subtype 4 (CMS4) of colorectal cancer (CRC) has the poorest prognosis and shows stromal activation and bulk epithelial-mesenchymal transition (EMT) signatures that largely reflect cancer-associated fibroblast-derived signals, obscuring tumor cell-intrinsic programs. Aberrant glycosylation drives EMT and metastasis, yet the glycosyltransferase landscape intrinsic to CMS4 tumor epithelium remains poorly defined because stromal signals dominate bulk transcriptomes. To overcome this confounding, we analyzed single-cell RNA-sequencing datasets to distinguish CMS4 tumor epithelial cells from CMS1–3 epithelial cells, normal epithelium, and stromal/immune populations. This identified a nine-gene glycosyltransferase signature uniquely upregulated in CMS4 tumor epithelium. Among these, GALNT5 showed consistent transcriptional induction during EMT in CRC cell lines. GALNT5 depletion suppressed proliferation, invasion, and migration, independent of overt changes in canonical EMT markers or AKT/ERK signaling. Immunohistochemical analysis of 431 resected CRC specimens confirmed that GALNT5 protein expression was restricted to cancer cells, particularly at the invasive front. High GALNT5 expression was associated with deeper invasion and advanced stage, and served as an independent prognostic factor for worse overall survival, notably within the microsatellite-stable subgroup. In conclusion, by leveraging single-cell transcriptomics, this study defines a CMS4 epithelial-intrinsic glycosylation program and highlights GALNT5 as a prognostic biomarker and therapeutic candidate.