title: Oxygen Availability for Porphyrin Biosynthesis Enzymes Determines the Production of Protoporphyrin IX (PpIX) during Hypoxia.
abstract: 5-Aminolevulinic acid (ALA), a precursor of porphyrin, is specifically converted to the fluorescent substance protoporphyrin IX (PpIX) in tumors to be used as a prodrug for photodynamic therapy and diagnosis. Hypoxia, a common feature of solid tumors, decreases the efficacy of ALA-based photodynamic therapy and diagnosis. This decrease results from the excretion of porphyrin precursor coproporphyrinogen III (CPgenIII), an intermediate in the biosynthesis of PpIX. However, the mechanism of CPgenIII excretion during hypoxia remains unclear. In this study, we revealed the importance of mitochondrial respiration for the production of PpIX during hypoxia. Porphyrin concentrations were estimated in human gastric cancer cell lines by HPLC. Expression levels of porphyrin biosynthesis genes were measured by qRT-PCR and immunoblotting. Blockage of porphyrin biosynthesis was an oxygen-dependent phenomenon resulting from decreased PpIX production in mitochondria under hypoxic conditions. PpIX production was increased by the inhibition of mitochondrial respiration complexes, which indicates that the enzymes of porphyrin biosynthesis compete with respiration complexes for molecular oxygen. Our results indicate that targeting the respiration complexes is a rationale for enhancing the effect of ALA-mediated treatment and diagnosis.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 B47 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Shimpei
authors.initials: S
authors.lastname: Otsuka
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 B47 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Matsumoto
authors.affiliation: SBI pharmaceuticals CO., LTD., Izumi Garden Tower 20F, 1-6-1, Roppongi, Minato-ku, Tokyo, 106-6020, Japan.
authors.forename: Motowo
authors.initials: M
authors.lastname: Nakajima
authors.affiliation: SBI pharmaceuticals CO., LTD., Izumi Garden Tower 20F, 1-6-1, Roppongi, Minato-ku, Tokyo, 106-6020, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 B47 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Shun-Ichiro
authors.initials: S
authors.lastname: Ogura
mesh_terms: D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D005786:Gene Expression Regulation; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D011166:Porphyrins / Q000096:biosynthesis*; D011524:Protoporphyrins / Q000096:biosynthesis*; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D011166:Porphyrins; D011524:Protoporphyrins; C028025:protoporphyrin IX; D010100:Oxygen