As shown in Figure 6E, CD9 depletion led to increased FAK and Cas-L tyrosine phosphorylation in mesothelioma cells, indicating that CD26 and CD9 may regulate the overall protein level and tyrosine-phosphorylation of β1 integrin-related signaling molecules as well as the expression of α5β1 integrin. This evidence concerns the gene DPP4 and mesothelioma.