Expression of DJ-1 and p53 proteins as determined by LC-MS/MS/PhosphoScan method. DJ-1/PARK-7 protein levels in KG1a cells with or without coculture with HS5 stroma at 0.5, 1, 4, and 18 hours were determined by Western blot (left) and confirmed by densitometry (right). There was a strong correlation between the decrease in DJ-1 over time in KG1a cells after coculture with HS5 stroma and an increase in protein levels of p53 as determined with anti–serine 46 phospho antibodies. The increase in p53 was associated with an increase in apoptosis (see Figure 5A). One of 3 identical experiments is shown.