Protoporphyrin IX (PpIX) enhances the generation of reactive oxygen species in cells following physicochemical interactions with X-rays. To evaluate the use of porphyrins as radio-sensitizers in radiotherapy, the transcriptomic effects of PpIX and/or X-ray irradiation were investigated in HeLa cells. Microarray experiments were performed using Agilent-014,850 Whole Human Genome Microarray 4x44K G4112F (GEO#: GSE61805). We selected the condition corresponding to 1 μg/mL PpIX exposure prior to 3 Gy-irradiation of cells, and collected cells 24 h post irradiation. X-ray exposure at a dose of 3 Gy did not affect cell survival 24 h post irradiation, regardless of the concentration of PpIX. Approximately 50% cells exposed to X-ray irradiation alone (XT) and 70% cells exposed to PpIX treatment for 6 h before X-ray irradiation (PpIX-XT) lost clonogenic ability. Based on p-values (p < 0.01), we selected genes for functional analysis. The majority of the regulated genes in the XT and PpIX-XT groups were related to cell cycle arrest. Furthermore, transcriptome analysis of the cells collected 24 h post irradiation revealed the fate of the cells that lost clonogenic ability due to cell cycle arrest.
Keywords: Cancer; Photodynamic therapy; Protoporphyrin IX (PpIX); Radiotherapy; Sensitizer; X-ray.