Single-Cell and Multiomics Characterization of p21 in Cancer Progression and Therapeutic Sensitivity

CDKN1A (encoding p21) is a canonical regulator of cell cycle arrest and genomic stability. However, its functional spectrum within the tumor microenvironment (TME), especially at single-cell resolution, remains insufficiently defined.

We performed an integrative multiomics analysis combining bulk transcriptomics, single-cell RNA sequencing (scRNA-seq), and functional assays across multiple cancer types. Publicly available datasets were used to assess CDKN1A expression, immune infiltration, and signaling pathways. Functional validation was conducted upon silencing or overexpression of p21 in several cancer cell lines.

Pancancer analysis revealed that CDKN1A expression is frequently dysregulated across multiple tumor types and is associated with patient prognosis. ScRNA-seq further demonstrated that CDKN1A was preferentially enriched in nonmalignant epithelial cells and varies along an inferred malignant epithelial transcriptional continuum. Computational cell-cell communication analysis suggested inferred ligand-receptor associations involving extracellular matrix-related and immune-associated signaling pathways. Functionally, p21 overexpression suppressed tumor cell proliferation, induced senescence and apoptosis, and reduced migratory capacity across multiple cancer cell lines. In vitro drug-sensitivity assays further showed that p21 overexpression was associated with enhanced sensitivity to targeted therapy and chemotherapy agents, as evidenced by reduced IC50 values. In addition, p21 regulated immune-related molecules, including ICOS, TGFB1, and PDCD1, and coculture experiments revealed that macrophage polarization differentially modulates p21-mediated tumor cell inhibition, with M1 macrophages enhancing and M2 macrophages attenuating this effect.

By delineating its function at single-cell resolution, we identify CDKN1A as a prognostic biomarker and a potential modulator of tumor-cell drug sensitivity that requires further clinical validation. These findings expand the conventional view of p21 from a cell cycle inhibitor to a context-dependent regulator of tumor immune interactions and therapeutic sensitivity-associated phenotypes.