Microbeam Radiation Therapy controls local growth of radioresistant melanoma and treats out-of-field locoregional metastasis.

PURPOSE Synchrotron-generated microbeam radiotherapy (MRT) represents an innovative preclinical type of cancer radiotherapy with an excellent therapeutic ratio. Beyond local control, metastatic spread is another important endpoint to assess the effectiveness of radiotherapy treatment. Currently, no data exists on an association between MRT and metastasis. Here, we evaluated the ability of MRT to delay B16F10 murine melanoma progression and locoregional metastatic spread. METHODS AND MATERIALS We assessed the primary tumor response and the extent of metastasis in sentinel lymph nodes in two cohorts of C57BL/6J mice, one receiving a single MRT and another receiving two MRT delivered with a 10-day interval. We compared these two cohorts with synchrotron broad beam-irradiated and non-irradiated mice. In addition, using multi-plex quantitative platforms, we measured plasma concentrations of 34 pro- and anti-inflammatory cytokines and frequencies of immune cell subsets infiltrating primary tumors that received either one or two MRT treatments. RESULTS Two MRT treatments were significantly more effective for local control than single MRT. Remarkably, the second MRT also triggered a pronounced regression of out-of-radiation field locoregional metastasis. Augmentation of CXCL5, CXCL12 and CCL22 levels after the second MRT indicated that inhibition of melanoma progression could be associated with increased activity of anti-tumor neutrophils and T-cells. Indeed, we demonstrated elevated infiltration of neutrophils and activated T-cells in the tumors following the second MRT. CONCLUSIONS Our study highlights the importance of monitoring metastasis following MRT and provides the first MRT fractionation schedule that promotes local and locoregional control with the potential to manage distant metastasis

High-Precision Radiosurgical Dose Delivery by Interlaced Microbeam Arrays of High-Flux Low-Energy Synchrotron X-Rays

Microbeam Radiation Therapy (MRT) is a preclinical form of radiosurgery dedicated to brain tumor treatment. It uses micrometer-wide synchrotron-generated X-ray beams on the basis of spatial beam fractionation. Due to the radioresistance of normal brain vasculature to MRT, a continuous blood supply can be maintained which would in part explain the surprising tolerance of normal tissues to very high radiation doses (hundreds of Gy). Based on this well described normal tissue sparing effect of microplanar beams, we developed a new irradiation geometry which allows the delivery of a high uniform dose deposition at a given brain target whereas surrounding normal tissues are irradiated by well tolerated parallel microbeams only. Normal rat brains were exposed to 4 focally interlaced arrays of 10 microplanar beams (52 µm wide, spaced 200 µm on-center, 50 to 350 keV in energy range), targeted from 4 different ports, with a peak entrance dose of 200Gy each, to deliver an homogenous dose to a target volume of 7 mm3 in the caudate nucleus. Magnetic resonance imaging follow-up of rats showed a highly localized increase in blood vessel permeability, starting 1 week after irradiation. Contrast agent diffusion was confined to the target volume and was still observed 1 month after irradiation, along with histopathological changes, including damaged blood vessels. No changes in vessel permeability were detected in the normal brain tissue surrounding the target. The interlacing radiation-induced reduction of spontaneous seizures of epileptic rats illustrated the potential pre-clinical applications of this new irradiation geometry. Finally, Monte Carlo simulations performed on a human-sized head phantom suggested that synchrotron photons can be used for human radiosurgical applications. Our data show that interlaced microbeam irradiation allows a high homogeneous dose deposition in a brain target and leads to a confined tissue necrosis while sparing surrounding tissues. The use of synchrotron-generated X-rays enables delivery of high doses for destruction of small focal regions in human brains, with sharper dose fall-offs than those described in any other conventional radiation therapy

[Alban Köhler (1874-1947): Inventor of grid therapy]

Grid (or sieve) therapy ("Gitter-" oder "Siebtherapie"), spatially fractionated kilo- and megavolt X-ray therapy, was invented in 1909 by Alban Köhler, a radiologist in Wiesbaden, Germany. He tested it on several patients before 1913 using approximately 60-70kV Hittorf-Crookes tubes. Köhler pushed the X-ray tube's lead-shielded housing against a stiff grid of 1 mm-square iron wires woven 3.0-3.5mm on center, taped tightly to the skin over a thin chamois. Numerous islets unshielded by iron in the pressure-blanched skin were irradiated with up to about 6 erythema doses (ED). The skin was then thoroughly cleansed, disinfected, and bandaged; delayed punctate necrosis healed in several weeks. Although grid therapy was disparaged or ignored until the 1930s, it has been used successfully since then to shrink bulky malignancies. Also, advanced cancers in rats and mice have been mitigated or ablated using Köhler's concept since the early 1990s by unidirectional or stereotactic exposure to an array of nearly parallel microplanar (25-75μm-wide) beams of very intense, moderately hard (median energy approximately 100 keV) synchrotron-generated X rays spaced 0.1-0.4mm on center. Such beams maintain sharp edges at high doses well beneath the skin yet confer little toxicity. They could palliate some otherwise intractable malignancies, perhaps in young children too, with tolerable sequelae. There are plans for such studies in larger animals

Death receptor-mediated suicide : a novel target of autoimmune disease treatment

In the thymus, based on the reactivity of their T-cell receptor with self-MHC and antigenic peptides, developing immature T-cells undergo positive and negative selection. Cells recognising self-peptides and MHC with high affinity are considered autoreactive, and thus potentially harmful, and are eliminated by induction of apoptotic cell death. Thymic negative selection is, however, only incomplete and autoreactive T-cells escape into the periphery. It is not the presence of autoreactive mature T- and B-lymphocytes as the underlying cause of tissue destruction and development of autoimmune diseases, but their uncontrolled and excessive clonal expansion upon activation by self-antigen. Thus, potent regulatory mechanisms must keep these autoreactive cells under control to avoid their inappropriate activation. Recent evidence indicates that death receptors of the tumour necrosis factor receptor family play a central role in mediating antigen receptor-induced suicide of autoreactive T-lymphocytes. Defects in these apoptosis-inducing regulatory mechanisms may result in the development of autoimmune diseases. Therefore, enhancing the cell's own suicide program, offers a most attractive therapeutic target for the treatment of autoimmune diseases

Transient and Efficient Vascular Permeability Window for Adjuvant Drug Delivery Triggered by Microbeam Radiation

Background: Microbeam Radiation Therapy (MRT) induces a transient vascular permeability window, which offers a novel drug-delivery system for the preferential accumulation of therapeutic compounds in tumors. MRT is a preclinical cancer treatment modality that spatially fractionates synchrotron X-rays into micrometer-wide planar microbeams which can induce transient vascular permeability, especially in the immature tumor vessels, without compromising vascular perfusion. Here, we characterized this phenomenon using Chicken Chorioallantoic Membrane (CAM) and demonstrated its therapeutic potential in human glioblastoma xenografts in mice. Methods: the developing CAM was exposed to planar-microbeams of 75 Gy peak dose with Synchrotron X-rays. Similarly, mice harboring human glioblastoma xenografts were exposed to peak microbeam doses of 150 Gy, followed by treatment with Cisplatin. Tumor progression was documented by Magnetic Resonance Imaging (MRI) and caliper measurements. Results: CAM exposed to MRT exhibited vascular permeability, beginning 15 min post-irradiation, reaching its peak from 45 min to 2 h, and ending by 4 h. We have deemed this period the "permeability window". Morphological analysis showed partially fragmented endothelial walls as the cause of the increased transport of FITC-Dextran into the surrounding tissue and the extravasation of 100 nm microspheres (representing the upper range of nanoparticles). In the human glioblastoma xenografts, MRI measurements showed that the combined treatment dramatically reduced the tumor size by 2.75-fold and 5.25-fold, respectively, compared to MRT or Cisplatin alone. Conclusions: MRT provides a novel mechanism for drug delivery by increasing vascular transpermeability while preserving vessel integrity. This permeability window increases the therapeutic index of currently available chemotherapeutics and could be combined with other therapeutic agents such as Nanoparticles/Antibodies/etc

Differential in situ expression of the genes encoding the chemokines MCP-1 and RANTES in human inflammatory bowel disease.

Two chemotactic cytokines, monocyte chemoattractant protein-1 (MCP-1) and RANTES, possibly contribute to the recruitment and activation of leukocytes in inflamed tissues. The expression of these cytokine genes was evaluated in tissue sections from resected bowel segments of 14 patients with inflammatory bowel disease (IBD) and seven control patients by use of 35S-labelled antisense RNA probes. MCP-1 and RANTES transcripts were generally increased in the intestinal mucosa of patients with IBD, compared with controls. Whereas MCP-1 gene expression in the mucosa was restricted to the lamina propria, the gene coding for RANTES was expressed in intraepithelial lymphocytes and in the subepithelial lamina propria. Furthermore, MCP-1 mRNA, but not RANTES mRNA, was abundant in vessel-associated cells, such as endothelial cells, medial smooth muscle cells, and intraluminal cells; in smooth muscle cells of the intestinal tunica muscularis; and in cells of the myenteric plexus. Compared with controls, a significant increase of MCP-1-expressing cells was observed in tissue specimens from patients with IBD, in endothelial cells of venules, and in cells present in the lumen of intestinal vessels. Conversely, the expression of MCP-1 mRNA in smooth muscle cells and myenteric plexus cells appeared to be comparable in control and diseased intestines. The increased number of MCP-1 and RANTES mRNA-expressing cells in mucosa from patients with IBD suggests that these cytokines play a role in the pathogenesis of mucosal inflammation. Furthermore, the expression of the MCP-1 gene in vessel-associated cells may indicate its involvement in mechanisms regulating the adhesion of blood monocytes to endothelial cells