Molecular mechanism and biological pathway of high-expressed RAD51 in regulating cell adhesion and potentially affecting oral squamous cell carcinoma.

Background: Oral squamous cell carcinoma (OSCC) is the most common malignant tumor in the oral cavity, with over 70% of cases detected in advanced stages and a 5-year survival rate of 50%. RAD51, a crucial DNA repair molecule, has also been implicated in the regulation of cell adhesion. However, its multi-platform expression patterns and functional role in cell adhesion within the context of OSCC have not yet been comprehensively validated.

Methods: Bulk RNA (RNA-seq and microarray), immunohistochemistry (IHC), and single-cell sequencing (scRNA-seq) were used to assess RAD51 expression and its clinical relevance in OSCC. CRISPR was used to knock out RAD51 and explore its effect on OSCC cell proliferation. Bulk RNA and scRNA-seq analyses were integrated to explore RAD51's molecular mechanisms, cellular communication, and metabolic pathways. Drug sensitivity analysis aimed to explore the relationship between RAD51 and drugs, while the target molecules of RAD51 transcription factors were identified.

Results: In bulk RNA (1,006 OSCC samples), IHC (162 OSCC tissues), and scRNA-seq (9,693 malignant epithelial cells), RAD51 was comprehensively upregulated in OSCC. The proliferation of OSCC cells was inhibited due to knockout of RAD51. Bulk RNA and scRNA-seq indicated that RAD51 was associated with cell adhesion. High expression of RAD51 was associated with the MIF pathway in cell communication, with the TCA cycle metabolism being mainly regulated. The expression of RAD51 was associated with resistance to Erlotinib, Gefitinib, and Selumetinib. In the molecular network, RAD51 was demonstrated a targeting relationship with adhesion-related molecules like CD74, JUP and MIF.

Conclusion: High expression of RAD51 may promote the advancement of OSCC by regulating the related mechanisms of cell adhesion.