PTPRD and head and neck squamous cell carcinoma: To test the association between PTPRD mutation and pSTAT3 expression directly, we transfected an HNSCC cell line with known endogenous PTPRD mutation (Cal27 harboring mutation S387L) with wild-type PTPRD or vector control and found that overexpression of wild-type PTPRD leads to significantly decreased pSTAT3 expression (P ≤ 0.05).