Decoding the Dynamic Landscape of Sequential Disease Stages from Oral Submucous Fibrosis to Oral Squamous Cell Carcinoma.

Oral submucous fibrosis (OSF) is a chronic and progressive disease of the oral mucosa that is considered potentially malignant. However, the specific mechanism of OSF occurrence and malignant transformation into oral squamous cell carcinoma (OSCC) is still unclear. This study aimed to elucidate the spatiotemporal changes in cellular biological behaviour during the occurrence and malignant transformation of OSF, providing new insights for understanding the underlying mechanism and developing novel therapeutic strategies. Sets of normal, OSF, margin area, and OSCC tissue samples were collected, and 10 × Visium spatial transcriptomics technology was used for sequencing library construction. The spatial transcriptomic data were combined with single-cell transcriptomic data for analysis. Phenotypic shifts in fibroblasts drove the progression of diverse disease stages, and immune cell patterns revealed adaptive immune dominance in OSF and immunosuppression in OSCC. A distinctive transitional zone with low transcriptional activity and intermediate transcriptomic features between noncancerous and cancer cells was identified at the forefront of the cancer invasion margin. Moreover, cancer-side cells had increased cell-cell communication around the tumour margin, reprogramming the adjacent microenvironment to facilitate invasion. The differential end states of epithelial cells demonstrated that basal epithelial cells were the dominant cell source of cancer cells in OSCC. Dynamic changes occur in gene expression and cellular function during the transformation of OSF into OSCC. The malignant transformation of OSF is a complex process involving multiple cell populations, in which changes first occur in cellular biological behaviours instead of pathomorphology. These spatiotemporal insights provide important evidence for clarifying the mechanisms of OSF-OSCC transformation and offer potential targets for early intervention. The identified transitional zone presents potential targets for early intervention in OSF patients at high risk of malignant transformation, supporting the development of strategies for OSCC prevention and precise clinical management.