The effects of photosensitization by hematoporphyrin derivative on the protein content of cultured human lung cancer cells. A flow cytometric analysis

In order to study the cytotoxic mechanisms of photodynamic therapy (PDT), the changes in the intracellular content of protein and DNA of cultured human lung cancer cells were examined by flow cytometry using the fluorescent dyes fluorescein isothiocyanate (FITC) and propidium iodide (PI). Immediately after PDT, the protein content increased while the DNA content showed little change. After more than 24 hours, the protein and DNA content were markedly decreased in lethally damaged cells; in sublethally damaged cells, however, the protein content gradually decreased to the level of that before PDT while the DNA content showed little change. These changes in the protein content may reflect the impairment of the plasma membrane function by PDT and its subsequent recovery in some cells.