Clinicopathological and prognostic significance of stromal p16 and p53 expression in oral squamous cell carcinoma.

The tumor microenvironment is highly heterogeneous and consists of neoplastic cells and diverse stromal components, including fibroblasts, endothelial cells, pericytes, immune cells, local and bone marrow-derived stromal stem and progenitor cells, and the surrounding extracellular matrix. Although the significance of p16 and p53 has been reported in various tumor types, their involvement in the stromal cells of oral squamous cell carcinoma (OSCC) remains unclear. We performed immunohistochemical analyses of p16 and p53 expression in OSCC samples, Of the 116 samples, 74 showed p16-positive stromal cells, and 33 showed p53-positive stromal cells. Both p16 and p53 positivity were associated with an increased histological grade, lymphovascular invasion, an immature stromal pattern with abundant amorphous extracellular matrix material, infiltrative invasion patterns (Yamamoto Kohama classification-4C and 4D), and poor prognosis. Multivariate analyses identified p16 and p53 positivity in the stroma as independent prognostic factors for overall survival (P = 0.032 and P = 0.020, respectively); moreover, stromal p16 positivity correlated with stromal p53 positivity. These findings indicated that p16 and p53 stroma positivity may regulate OSCC tumor aggressiveness.