DW-MRI and (18) F-FLT PET for early assessment of response to radiation therapy associated with hypoxia-driven interventions. Preclinical studies using manipulation of oxygenation and/or dose escalation.

Early markers of treatment response may help in the management of patients by predicting the outcome of a specific therapeutic intervention. Here, we studied the potential value of diffusion-weighted MRI (DW-MRI) and (18)F-fluorothymidine ((18)F-FLT), markers of cell death and cell proliferation respectively, to predict the response to irradiation. In addition, dose escalation and/or carbogen breathing were used to modulate the response to irradiation.

Potential role of hypoxia imaging using (18)F-FAZA PET to guide hypoxia-driven interventions (carbogen breathing or dose escalation) in radiation therapy.

Background And Purpose: Hypoxia-driven intervention (oxygen manipulation or dose escalation) could overcome radiation resistance linked to tumor hypoxia. Here, we evaluated the value of hypoxia imaging using (18)F-FAZA PET to predict the outcome and guide hypoxia-driven interventions.

Material And Methods: Two hypoxic rat tumor models were used: rhabdomyosarcoma and 9L-glioma.

Tumor hypoxia does not drive differentiation of tumor-associated macrophages but rather fine-tunes the M2-like macrophage population.

Tumor-associated macrophages (TAM) are exposed to multiple microenvironmental cues in tumors, which collaborate to endow these cells with protumoral activities. Hypoxia, caused by an imbalance in oxygen supply and demand because of a poorly organized vasculature, is often a prominent feature in solid tumors. However, to what extent tumor hypoxia regulates the TAM phenotype in vivo is unknown.

Optimization of tumor radiotherapy with modulators of cell metabolism: toward clinical applications.

Most solid tumors are characterized by unstable perfusion patterns, creating regions of hypoxia that are detrimental to radiotherapy treatment response. Because postsurgical radiotherapy, alone or in combination with other interventions, is a first-line treatment for many malignancies, strategies aimed at homogeneously increasing tumor pO2 have been the focus of intense research over the past decades. Among other approaches of demonstrable clinical and preclinical utility, this review focuses on those directly targeting oxygen consumption to redirect oxygen from a metabolic fate to the stabilization of radiation-induced DNA damage, more particularly drugs targeting glucose and lactate metabolism, nitric oxide donors or inducers, and mitogen-activated protein kinase pathway inhibitors.

Tumor reoxygenation following administration of the EGFR inhibitor, gefitinib, in experimental tumors.

It is well recognized that tumor hypoxia is a critical determinant for response to therapy. The effect of an EGFR inhibitor/gefitinib (Iressa®) on tumor oxygenation was monitored daily using in vivo EPR (electron paramagnetic resonance) oximetry on TLT and FSaII tumor models. An increase in pO2 was shown at a dose of 45 mg/kg i.

Multimodal imaging of tumor response to sorafenib combined with radiation therapy: comparison between diffusion-weighted MRI, choline spectroscopy and 18F-FLT PET imaging.

The purpose of this study was to determine the value of different imaging modalities, that is, magnetic resonance imaging/spectroscopy (MRI/MRS) and positron emission tomography (PET), to assess early tumor response to sorafenib with or without radiotherapy. Diffusion-weighted (DW)-MRI, choline (1)H MRS at 11.7 T, and (18)F-FLT PET imaging were used to image fibrosarcoma (FSaII) tumor-bearing mice over time.

Electron paramagnetic resonance highlights that the oxygen effect contributes to the radiosensitizing effect of paclitaxel.

Background: Paclitaxel (PTX) is a potent anti-cancer chemotherapeutic agent and is widely used in the treatments of solid tumors, particularly of the breast and ovaries. An effective and safe micellar formulation of PTX was used to administer higher doses of PTX than Taxol® (the current commercialized drug). We hypothesize that PTX-loaded micelles (M-PTX) may enhance tumor radiosensitivity by increasing the tumor oxygenation (pO(2)).

Tumor reoxygenation following administration of Mitogen-Activated Protein Kinase inhibitors: a rationale for combination with radiation therapy.

Background And Purpose: The relevance of Mitogen Activated Protein Kinase (MAPK) inhibitors as co-treatments for radiation therapy is investigated, with special focus on a potential link between the MAPK pathway and tumor hypoxia, which is a critical determinant for response to therapy.

Materials And Methods: The effects of two MAPK inhibitors, Sorafenib and PD0325901, were monitored daily using in vivo EPR (Electron Paramagnetic Resonance) oximetry in FSaII and TLT tumor models in order to identify a window of reoxygenation, during which tumor blood flow, oxygen consumption and radiation sensitivity were assessed.

Results: Reoxygenation was shown after two days of treatments with Sorafenib or PD0325901 in two tumor models, which was further successfully exploited with Sorafenib for improving the radiation response of FSaII tumors by a factor of 1.

Arsenic trioxide treatment decreases the oxygen consumption rate of tumor cells and radiosensitizes solid tumors.

Arsenic trioxide (As(2)O(3)) is an effective therapeutic against acute promyelocytic leukemia and certain solid tumors. Because As(2)O(3) inhibits mitochondrial respiration in leukemia cells, we hypothesized that As(2)O(3) might enhance the radiosensitivity of solid tumors by increasing tumor oxygenation [partial pressure of oxygen (pO(2))] via a decrease in oxygen consumption. Two murine models of radioresistant hypoxic cancer were used to study the effects of As(2)O(3).

The impact of hyperglycemia and the presence of encapsulated islets on oxygenation within a bioartificial pancreas in the presence of mesenchymal stem cells in a diabetic Wistar rat model.

This study investigates the potential of bone marrow (BM-MSCs) versus adipose mesenchymal stem cells (AMSCs) to potentiate the oxygenation of encapsulated islets in a subcutaneous bioartificial pancreas. Oxygen pressures (inside subcutaneous implants) were followed in vivo (by electronic paramagnetic resonance) in non-diabetic/diabetic rats transplanted with encapsulated porcine islets or empty implants up to 4 weeks post-transplantation. After graft explantation, neoangiogenesis surrounding the implants was assessed by histomorphometry.

Comparative in vivo dissociation of gadolinium chelates in renally impaired rats: a relaxometry study.

Purpose: Investigation of dissociated versus chelated gadolinium (Gd) in plasma, skin, and bone of rats with impaired renal function after administration of ionic macrocyclic (gadoterate or Dotarem) or nonionic linear (gadodiamide or Omniscan) Gd chelates.

Materials And Methods: Subtotally nephrectomized Wistar rats were subjected to receive daily injections of 2.5 mmol/kg of Omniscan, gadodiamide without excess ligand caldiamide, Dotarem, or saline (n = 7-10 rats/group) for 5 consecutive days.

Captopril and S-nitrosocaptopril as potent radiosensitizers: Comparative study and underlying mechanisms.

In an effort to improve the issue of radiotherapy treatments, we tested whether S-nitrosocaptopril, a molecule combining a NO donor and an angiotensin converting enzyme inhibitor (ACE inhibitor), could temporarily improve the hemodynamic status of experimental tumors. We monitored the effect of S-nitrosocaptopril in TLT tumors using non rinvasive magnetic resonance techniques. We identified a time window during which tumor oxygenation was improved, as a result of a combined effect on tumor blood flow and oxygen consumption.