ELK1/NOL3/GRP78 axis regulates proliferation and stemness in TP53-mutant colon cancer by enhancing adaptive endoplasmic reticulum stress.

BACKGROUND

Colon cancer harboring TP53 mutations is highly aggressive and associated with short survival. Adaptive, rather than apoptotic, endoplasmic reticulum (ER) stress endows TP53-mutant tumor cells with enhanced protein-folding capacity, metabolic plasticity, and chemoresistance. However, the upstream regulators that selectively drive this cytoprotective program within the cancer stem cell compartment remain elusive.

METHODS

Single-cell RNA-seq analysis of TP53-mutant versus wild-type tumors was performed to identify ER stress- and mitochondrial metabolism-related differentially expressed genes (EMRDEGs). A four-gene prognostic signature was constructed from TCGA-COAD and GEO cohorts using DESeq2 and LASSO regression. Functional analyses included gain- and loss-of-function studies in TP53-mutant (SW480, HT-29) and TP53-wild-type (HCT116) colon cancer cells, followed by CCK-8, colony formation, microsphere formation, xenograft, dual-luciferase reporter, coimmunoprecipitation and western blot assays.

RESULTS

TP53-mutant tumor stem cells exhibited synchronized activation of ER stress and mitochondrial metabolic pathways, guiding EMRDEG selection. Among the signature genes, nucleolar protein 3 (NOL3) emerged as an independent adverse prognostic factor that correlated with advanced stage, nodal positivity and shorter overall survival. NOL3 enhanced proliferation and cancer stem cell properties in a TP53-mutant-dependent manner. Mechanistically, ELK1 transcriptionally upregulated NOL3, which physically interacted with GRP78 to activate the PERK/CHOP branch of the unfolded protein response, thereby amplifying adaptive ER stress.

CONCLUSION

The ELK1/NOL3/GRP78 axis promotes the progression of TP53-mutant colon cancer by increasing adaptive ER stress and stemness. NOL3 serves as a valuable prognostic biomarker and a potential therapeutic target.