PPARGC1A and neoplasm: To verify whether PGC–1α is regulated by p53S and how this increase in expression is regulated, we compared the expression of PGC–1α in early-stage (ES) senescent cells, late-stage (LS) tumorigenic cells, and SCID tumor cells (obtained from SCID tumors formed by the subcutaneous injection of late-stage cells, Figure 1F).