Proteins in PC-9 cells were extracted by CO-IP lysis buffer, PHGDH antibody and agarose gel beads were added into the lysis buffer and rotated in 4°C overnight. The agarose gel beads were washed for 5 times by centrifugation, and denatured in 2 x loading buffer. The denatured protein samples were sent for MS analysis and screened for the proteins interacted with PHGDH.