PLPP4 and squamous cell lung carcinoma: We first analyzed the expression levels of LPPs proteins, including PLPP1-7, in the high throughput paired lung carcinoma RNA expression profile datasets from TCGA and found that the expression levels of PLPP2, PLPP4, PLPP5 and PLPP6 were differentially elevated in lung adenocarcinoma (ADC) and lung squamous cell carcinoma (SQC) tissues compared to the respective adjacent normal tissues (ANT), particularly PLPP4 with a 12.03-fold change in ADC and a 12.65-fold change in SQC (Fig. 1a and b).