Monitoring oxygen levels in orthotopic human glioma xenograft following carbogen inhalation and chemotherapy by implantable resonator‐based oximetry

Abstract

Hypoxia is a critical hallmark of glioma, and significantly compromises treatment efficacy. Unfortunately, techniques for monitoring glioma pO2 to facilitate translational research are lacking. Furthermore, poor prognoses of patients with malignant glioma, in particular glioblastoma multiforme, warrant effective strategies that can inhibit hypoxia and improve treatment outcome. EPR oximetry using implantable resonators was implemented for monitoring pO2 in normal cerebral tissue and U251 glioma in mice. Breathing carbogen (95% O2 + 5% CO2) was tested for hyperoxia in the normal brain and glioma xenografts. A new strategy to inhibit glioma growth by rationally combining gemcitabine and MK-8776, a cell cycle checkpoint inhibitor, was also investigated. The mean pO2 of left and right hemisphere were approximately 56 – 69 mmHg in the normal cerebral tissue of mice. The mean baseline pO2 of U251 glioma on the first and fifth day of measurement was 21.9 ± 3.7 and 14.1 ± 2.4 mmHg, respectively. The mean brain pO2 including glioma increased by at least 100% on carbogen inhalation, although the response varied between the animals over days. Treatment with gemcitabine + MK-8776 significantly increased pO2 and inhibited glioma growth assessed by MRI. In conclusion, EPR oximetry with implantable resonators can be used to monitor the efficacy of carbogen inhalation and chemotherapy on orthotopic glioma in mice. The increase in glioma pO2 of mice breathing carbogen can be used to improve treatment outcome. The treatment with gemcitabine + MK-8776 is a promising strategy that warrants further investigation.

M2 macrophages are more resistant than M1 macrophages following radiation therapy in the context of glioblastoma

“…Normoxia (20% O 2 ) cells were cultured in a humidified 5% CO 2 /air atmosphere. Moderate (1% O 2 , the O 2 level commonly found in GB) [ 22 ] and severe (0.2% O 2 , the O 2 level found around necrotic areas of GB) hypoxic cells were cultured in a humidified 5% CO 2 /balance N 2 gas mixture in a hypoxic chamber (Invivo2 500, Ruskinn, Awel) at 37°C. For radiation treatment, M0 MΦ were cultured either in normoxia or in hypoxia 6h before radiation.…”

“…However, as 2Gy produces only modest cell death, 8Gy was also delivered to amplify any differences in the radiosensitivities of the different cell populations. Given the hypoxic nature of GB and that hypoxia represents a factor of poor prognosis and also influences inflammation [ 12 ], experiments were conducted under normoxic, moderate (1% O 2 , the O 2 level commonly found in GB) [ 22 ] and severe (0.2% O 2 , the O 2 level found around necrotic areas of GB) hypoxic conditions, to recapitulate the various oxygen level that are present in the tumor situation.…”

HIF1α regulates glioma chemosensitivity through the transformation between differentiation and dedifferentiation in various oxygen levels

“…Glioma cells were exposed to different oxygen levels (hypoxia, 1%O 2 ; normoxia, 21%O 2 ; hyperoxia, 95%O 2 ) under normobaric conditions with or without TMZ. For hypoxic and normoxic treatments, cells were exposed to corresponding oxygen levels at all times 13 ; for hyperoxic treatment, cells were exposed to 95%O 2 for 60 min every 12 h 15 , 16 , 46 . CD133 − CD15 − NESTIN − glioma cells were maintained in DMEM/F12 + 1%FBS.…”

Hypoxia induces macrophage polarization and re-education toward an M2 phenotype in U87 and U251 glioblastoma models

“… 30,31 However, up until now, the detailed relationship between hypoxia and the M1 to M2 transition has never been formally analyzed in vivo and warrants an in-depth investigation. Using robust and pertinent models of GBM, previously shown to develop severe hypoxia 32 such as that observed in patients, 33 we evaluated whether GBM hypoxia, in addition to its well described effect on the infiltration of MΦ, could affect the acquisition of an M2 phenotype.…”