Permanent Occlusion of Feeding Arteries and Draining Veins in Solid Mouse Tumors by Vascular Targeted Photodynamic Therapy (VTP) with Tookad

Antiangiogenic and anti-vascular therapies present intriguing alternatives to cancer therapy. However, despite promising preclinical results and significant delays in tumor progression, none have demonstrated long-term curative features to date. Here, we show that a single treatment session of Tookad-based vascular targeted photodynamic therapy (VTP) promotes permanent arrest of tumor blood supply by rapid occlusion of the tumor feeding arteries (FA) and draining veins (DV), leading to tumor necrosis and eradication within 24–48 h.A mouse earlobe MADB106 tumor model was subjected to Tookad-VTP and monitored by three complementary, non-invasive online imaging techniques: Fluorescent intravital microscopy, Dynamic Light Scattering Imaging and photosensitized MRI. Tookad-VTP led to prompt tumor FA vasodilatation (a mean volume increase of 70%) with a transient increase (60%) in blood-flow rate. Rapid vasoconstriction, simultaneous blood clotting, vessel permeabilization and a sharp decline in the flow rates then followed, culminating in FA occlusion at 63.2 sec±1.5SEM. This blockage was deemed irreversible after 10 minutes of VTP treatment. A decrease in DV blood flow was demonstrated, with a slight lag from FA response, accompanied by frequent changes in flow direction before reaching a complete standstill. In contrast, neighboring, healthy tissue vessels of similar sizes remained intact and functional after Tookad-VTP.Tookad-VTP selectively targets the tumor feeding and draining vessels. To the best of our knowledge, this is the first mono-therapeutic modality that primarily aims at the larger tumor vessels and leads to high cure rates, both in the preclinical and clinical arenas

Detection of Light Images by Simple Tissues as Visualized by Photosensitized Magnetic Resonance Imaging

In this study, we show how light can be absorbed by the body of a living rat due to an injected pigment circulating in the blood stream. This process is then physiologically translated in the tissue into a chemical signature that can be perceived as an image by magnetic resonance imaging (MRI). We previously reported that illumination of an injected photosynthetic bacteriochlorophyll-derived pigment leads to a generation of reactive oxygen species, upon oxygen consumption in the blood stream. Consequently, paramagnetic deoxyhemoglobin accumulating in the illuminated area induces changes in image contrast, detectable by a Blood Oxygen Level Dependent (BOLD)-MRI protocol, termed photosensitized (ps)MRI. Here, we show that laser beam pulses synchronously trigger BOLD-contrast transients in the tissue, allowing representation of the luminous spatiotemporal profile, as a contrast map, on the MR monitor. Regions with enhanced BOLD-contrast (7-61 fold) were deduced as illuminated, and were found to overlap with the anatomical location of the incident light. Thus, we conclude that luminous information can be captured and translated by typical oxygen exchange processes in the blood of ordinary tissues, and made visible by psMRI (Fig. 1). This process represents a new channel for communicating environmental light into the body in certain analogy to light absorption by visual pigments in the retina where image perception takes place in the central nervous system. Potential applications of this finding may include: non-invasive intra-operative light guidance and follow-up of photodynamic interventions, determination of light diffusion in opaque tissues for optical imaging and possible assistance to the blind

Temporal correlation between illumination and BOLD-contrast changes.

<p>A. Time-course of the BOLD response in the deduced illuminated area (white circle in G). The first 4 min included the pretreatment (PC) and the light control (LC) pulses (200 mW/cm²). Each time point corresponds to a 12 s T₂* BOLD-sensitive image. Black arrow indicates WST11 injection to begin photosensitization, using an alternating light∶dark sequence (12 s∶110 s), paradigm P1 (red bars). B. Percent BOLD activation map at t = 6.4 min, overlaid on the anatomic image, C. C. MRI coronal view of the rat thigh, s.c. grafted with MADB106 tumor. A light beam (φ 1 cm) was projected onto the tumor area. The white dotted circle depicts the tumor. D–F. Correlation coefficient maps (p<0.02) obtained after the 1^st, 2^nd and 3^rd light pulses respectively, overlaid on the anatomic image. G. Correlation coefficient map of the entire paradigm (60 images) overlaid on the anatomy, allowing deduction of the illuminated field on the psMR image (white circle) that spatially overlaps with the incident light. The colored pixel clusters represent high blood vessel densities and/or larger vessels in the illuminated zone; while the dark areas represent low/no vascularity. The contrast enhancement ratio of illuminated relative to the surrounding areas was 49-fold (average 33±23SD, n = 8). H. Gd-DTPA contrast enhanced imaging (20 min post-treatment) marks functional, permeable blood vessels. The inset shows the correlation map overlaid on the GdDTPA enhanced image. Note: non-illuminated vasculature is not visible on the correlation map (compare red arrows in G versus H). Dashed white circles represent copies of the white circle in G. BOLD-contrast scale bar relates to (B) and correlation scale bar to (D–G).</p

Shape-recognition of illumination field by BOLD-contrast changes: P2 paradigm.

<p>Homogeneous light (55 mW/cm²) was delivered via a diffuser onto the rat thigh. With the use of respective masks the light beam-cross section was circular (φ 1.6 cm, A–D) or kite-shaped (0.6 cm length, E–H). B&F. Representative BOLD-contrast activation maps acquired at the end of the photosensitization phase are overlaid on the anatomic image and D&G. are the respective correlation coefficient maps (p<0.02). Colored pixel clusters on the anatomic image outline the deduced shape of the light field. Contrast enhancements of the deduced circle and the kite shapes were respectively 21 and 24-fold higher than their neighboring surroundings. D&H. Locations and shapes of the projected light fields on the respective anatomic images are deduced from the above correlations (white shapes). I. The BOLD-MRI protocol, using an acquisition time of 25 s/image yielded a total of 45 (A–D) or 40 images (E–H). J. Paradigm P2 consists of a single 10 min illumination. PI = Post-illumination.</p