Tensin 1 (TNS1) is a protein localizes to focal adhesions, regions of the plasma membrane where the cell attaches to the extracellular matrix. It crosslinks actin filaments and contains a Src homology 2 (SH2) domain, which is often found in molecules involved in signal transduction. TNS1 contains binding domain, which allows it to interact with a variety of signaling molecules and transmembrane receptors, such as integrins and receptor tyrosine kinases. To test the effect of TNS1 protein on cell proliferation, A549 cells were seeded into triplicate wells of 96-well plates and allowed to attach, replaced with various concentrations of recombinant human TNS1. After incubated for 72h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10 μl of CCK-8 solution was added to each well of the plate, then the absorbance at 450 nm was measured using a microplate reader after incubating the plate for 1-4 hours at 37 ℃. Cell viability was assessed by CCK-8 assay after incubation with recombinant human TNS1 for 72h. The result was shown in Figure 1. It was obvious that TNS1 significantly decreased cell viability of A549 cells. The ED50 of recombinant human TNS1 is 1.348 μg/ml.