title: Detection of different hypoxic cell subpopulations in human melanoma xenografts by pimonidazole immunohistochemistry.
abstract: This study aimed at developing immunohistochemical assays for different subpopulations of hypoxic cells in tumors. BALB/c-nu/nu mice bearing A-07 or R-18 tumors were given a single dose of 90 mg/kg body weight or three doses (3 h apart) of 30 mg/kg body weight of pimonidazole hydrochloride intravenously. The fraction of pimonidazole-labeled cells was assessed in paraffin-embedded and frozen tumor sections and compared with the fraction of radiobiologically hypoxic cells. The staining pattern in paraffin-embedded sections indicated selective staining of chronically hypoxic cells. Frozen sections showed a staining pattern consistent with staining of both chronically and acutely/repetitively hypoxic cells. Fraction of pimonidazole-labeled cells in paraffin-embedded sections was lower than the fraction of radiobiologically hypoxic cells (single-dose and triple-dose experiment). In frozen sections, fraction of pimonidazole-labeled cells was similar to (single-dose experiment) or higher than (triple-dose experiment) fraction of radiobiologically hypoxic cells. Three different subpopulations of hypoxic cells could be quantified by pimonidazole immunohistochemistry: the fraction of cells that are hypoxic because of limitations in oxygen diffusion, the fraction of cells that are hypoxic simultaneously because of fluctuations in blood perfusion, and the fraction of cells that are exposed to one or more periods of hypoxia during their lifetime because of fluctuations in blood perfusion.
authors.affiliation: Group of Radiation Biology and Tumor Physiology, Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Montebello, Oslo, Norway.
authors.forename: Kristine
authors.initials: K
authors.lastname: Gulliksrud
authors.forename: Ida K
authors.initials: IK
authors.lastname: Vestvik
authors.forename: Kanthi
authors.initials: K
authors.lastname: Galappathi
authors.forename: Berit
authors.initials: B
authors.lastname: Mathiesen
authors.forename: Einar K
authors.initials: EK
authors.lastname: Rofstad
mesh_terms: D000818:Animals; D015687:Cell Hypoxia; D005260:Female; D005629:Frozen Sections; D006801:Humans; D007150:Immunohistochemistry; D008546:Melanoma, Experimental / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D009593:Nitroimidazoles / Q000032:analysis / Q000378:metabolism*; D016612:Paraffin Embedding; D014183:Transplantation, Heterologous
chemical_list: D009593:Nitroimidazoles; C033815:pimonidazole