Firstly, we detected the protein expression of PADI4 in the normal human osteoblast cell (hFOB1.19) and several human osteosarcoma cell lines (U2OS, Saos-2, HOS, SJSA1, and 143B) by Western blot, and the results indicated increased PADI4 expression in osteosarcoma cells (Figure 3(a)). Here, PADI4 is linked to osteosarcoma.