We first performed immunohistochemistry to examine the expression of WIP1 in human lung cancer samples with a tissue array containing 116 NSCLC tumor tissue samples (60 squamous cell carcinoma and 56 adenocarcinoma specimens) and 16 normal lung tissues/normal adjacent lung tissue samples (N/NAT) (4N and 12 NAT specimens) (Fig. 1a). This evidence concerns the gene PPM1D and squamous cell carcinoma.