Single-Cell and Spatial Transcriptome Profiling Identifies the Transcription Factor BHLHE40 as a Driver of EMT in Metastatic Colorectal Cancer

Colorectal cancer is one of the most common malignant tumors in humans, with liver metastasis being the primary cause of mortality. The epithelial-mesenchymal transition (EMT) process endows cancer cells with enhanced metastatic potential. To elucidate the cellular mechanisms driving EMT in colorectal cancer, we analyzed single-cell RNA sequencing data from 11 nonmetastatic primary tumors (TnM) and 11 metastatic primary tumors (TM) from colorectal cancer patients. Compared with the TnM group, the TM samples showed elevated numbers of malignant epithelial cell and cancer-associated fibroblast (CAF) subsets that displayed enrichments of EMT, angiogenesis, and TGFβ signaling pathways. One specific TM-enriched subgroup of malignant epithelial cells underwent EMT to transdifferentiate into CXCL1+ CAFs that subsequently differentiated into SFRP2+ CAFs, which was validated by spatial transcriptomic and pseudotime trajectory analyses. Furthermore, cell-cell communication analysis identified BHLHE40 as a probable key transcription factor driving EMT that was associated with poor prognosis. Finally, in vitro and in vivo experiments functionally substantiated that BHLHE40 promoted the proliferation, invasion, migration, EMT, and liver metastasis of colorectal cancer cells. In summary, this study identified BHLHE40 as a key transcription factor regulating EMT that promotes liver metastasis in colorectal cancer. Significance: Integrated analysis of single-cell RNA sequencing and spatial transcriptomics in metastatic colorectal cancer provides insights into the mechanisms underlying EMT and cancer-associated fibroblast differentiation, which could help improve patient diagnosis and treatment.