Aims Recent studies have shown that phosphorylation of p120-catenin (p120) promotes progression and invasion of oral squamous cell carcinoma (OSCC) cells. The objective of the current study was to evaluate the usefulness of phosphorylated p120-catenin (pp120) as a biomarker for predicting clinical behaviour in the carcinogenesis of potentially malignant oral lesions.

Methods In a retrospective follow-up study, the expression pattern of pp120 protein was determined using immunohistochemistry in samples from 68 patients with potentially malignant oral lesions, including patients with untransformed lesions (n=38) and patients with malignant transformed lesions (n=30). Analysis of corresponding post-malignant lesions (OSCCs) was also performed.

Results There was high expression of pp120 in 35 of 68 (51.5%) of general potentially malignant oral lesions and 23 of 30 (76.7%) of OSCCs compared with expression in normal oral mucosa. Kaplan–Meier analysis revealed that patients with potentially malignant oral lesions expressing high levels of membranous pp120 had a significantly higher incidence of OSCC than those expressing low expressing pp120 (p=0.002; log-rank test). Cox regression analysis revealed that this pp120 expression pattern was significantly associated with a 3.43-fold increase in the risk of malignant progression (p=0.007). In addition, there was a significant correlation between high levels of membranous expression of pp120 in pre-malignant lesions and cytoplasmic expression in post-malignant lesions (p=0.028).

Conclusions The data indicated that a high level of membranous expression of pp120 in potentially malignant oral lesions is an early event during oral carcinogenesis, and that the mislocalisation of expression of pp120 from the cell membrane to the cytoplasm is associated with oral cancer progression. pp120 may serve as a useful marker for the identification of a high risk of potentially malignant oral lesions progressing to OSCC.