Fig. 2From: Reactivation of TAp73 tumor suppressor by protoporphyrin IX, a metabolite of aminolevulinic acid, induces apoptosis in TP53-deficient cancer cellsPpIX induces apoptosis and activates TAp73 in p53-null cancer cells. a PpIX induces caspases as shown by the increase in the fluorescent signal in p53-null HCT 116 p53−/− and H1299 cancer cells. b PARP-1 cleavage in H1299 cells is induced by PpIX after 48 h treatment. c mRNA levels of NOXA and PUMA in H1299 cells treated with 1 μg/ml PpIX are elevated after 12 h. d, e PpIX induces TAp73 and its proapoptotic targets in H1299 (d) and HCT 116 TP53−/− (e) cancer cells. 20 µM CDDP and 10 µM Nutlin were used as positive controls for induction of p73. The uncropped blots for (d) are presented in Additional file 4: Figure S4a. f PpIX downregulates ΔNp73 protein levels in HCT 116 p53−/− cancer cellsBack to article page