Fig. 1.

PpIX inhibits proliferation of cancer cells lacking p53. a Schematic representation of the splice variants in TP73 gene (upper panel) and domain structure of p73 (lower panel). TA transactivation domain, DBD DNA binding domain, OD oligomerization domain, CT C terminus. b PpIX induces dose-dependent growth inhibition in a long-term proliferation assay. c Ectopic expression of TAp73α sensitizes cells to PpIX after 24 h as demonstrated by WST-1 proliferation assay. Inserted blot represents the level of expression of TAp73α. Please note that the blot has been cropped. Dotted line represents where the blot has been cut. The uncropped full length version is presented in Additional file 3: Figure S3a. d TAp73α overexpression sensitizes H1299 to PpIX-induced inhibition of proliferation. e, f PpIX does not induce DNA damage in cancer cells at the effective therapeutic concentrations. g 2.5 μg/ml PpIX induces PARP-1 cleavage in HCT 116 p53−/− but not in non-transformed human diploid fibroblasts. Dotted line represents where the blot has been cut. The uncropped blot is presented in Additional file 3: Figure S3b