Abstract 1693: Intracellular hypoxia is dominantly determined by mitochondrial respiratory activity.

Intracellular oxygen concentration ([O 2 ] i.c. ) regulates key biological functions such as HIF-1α activation, glucose transport, potassium pumps, intracellular calcium concentration, P450 family enzymes and HMGR expression. However, the mechanisms regulating [O 2 ] i.c remain to be defined. Here, we provide direct evidence of the mitochondrion9s role in [O 2 ] i.c. regulation. We used bis(2-(2′-benzothienyl)-pyridianto-N,C 3’ irridium(acetylacetonate) (BTP) to measure [O 2 ] i.c. in living cells via microscopy. 5 Well-differentiated cancers, LNCaP and MCF-7 showed intracellular hypoxia without exogenous hypoxia. In contrast, poorly-differentiated cancers exhibited intracellular normoxia, and exogenous hypoxia could induce hypoxia. The specific complex I inhibitor, rotenone, and the reduction of mitochondrial DNA (mtDNA) content increased in [O 2 ] i.c, , indicating that [O 2 ] i.c. is regulated by mitochondrial respiratory activity. [O 2 ] i.c. is additionally regulated by glucose, but the dose-dependent relationship is parabolic. The no glucose condition induced normoxia, and the low concentration glucose condition (0.045mg/ml) induced strong hypoxia. [O 2 ] i.c. was found to be additionally determined by the presence of FCS in the growth medium, and this effect was mimicked by an androgen analog, R1881, suggesting that androgen, glucose concentration and respiratory function are important regulators of [O 2 ] i.c. . Citation Format: Sara Prior, Ara Kim, Seiji Tobita, Toshiyuki Takeuchi, Masahiro Higuchi. Intracellular hypoxia is dominantly determined by mitochondrial respiratory activity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1693. doi:10.1158/1538-7445.AM2013-1693