This Article Abstract Full Text Full Text (PDF) Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tozer, G M Search for Related Content PubMed PubMed Citation Articles by Tozer, G M

Measuring tumour vascular response to antivascular and antiangiogenic drugs

Tumour Microcirculation Group, Gray Cancer Institute, PO Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR, UK

View larger version (151K): [in a new window]   Figure 1. Measurement of permeability of the tumour vasculature to fluoroscein isothiocyanate (FITC)-albumin using intravital microscopy of tumours growing in dorsal skin flap "window" chambers. A time sequence (0–2 h) of FITC-albumin extravasation in the P22 rat tumour was detected by multiphoton fluorescence imaging, which provides images with no out of focus fluorescence for full quantification. "Patlak" plots of four random vessels are shown. KI, the plasma clearance constant for albumin was calculated from the gradient of the straight line portion of the graph in ml blood per ml tissue per minute (ml•ml–1•min–1). The vascular permeability–surface area product (PS product) is equivalent to KI for a high molecular weight compound whose uptake into tissue is permeability (rather than flow) limited and whose backflux into the blood is low.

View larger version (39K): [in a new window]   Figure 2. The effects of 10 mg kg–1 CA-4-P on mean arterial blood pressure (MABP) and blood flow rate to the P22 tumour and selected normal tissues in the BDIX rat. MABP was measured via an intra-arterial cannula. Comparison of MABP and skeletal muscle blood flow results suggest that the initial hypertensive effect is due to vasoconstriction in muscle. Spleen is the most responsive normal tissue but the greatest effect is found in tumour. Blood flow rate was measured using the tissue uptake of radiolabelled iodo-antipyrine, where tracer concentration versus time curves for arterial blood and tissue are deconvolved to extract tissue blood flow rates for tumour and normal tissues. Values are the mean±1 standard error (SE). The shaded bars show the limits of the SE for the control animals. A significant difference from control at the 5% level is represented by *. Figure adapted from reference [80].

View larger version (72K): [in a new window]   Figure 3. Upper panels show pseudocolour images of tissue blood flow, in ml blood per gram tissue per minute (ml g–1 min–1), computed from autoradiograms of 20 µm thick frozen sections of 15 mm diameter P22 rat tumours. Tumours were excised from an untreated rat (a) or at various times after treatment from rats treated with a clinically relevant dose of 10 mg kg–1 CA-4-P (b–d). Blood flow was computed pixel by pixel using the methods described in Figure 2. Lower panels show paraffin-embedded 3 µm thick tumour sections stained with haematoxylin and eosin from a separate group of rats treated as for the upper panel. Images in (a) show typical heterogeneity of blood flow in untreated tumours and spindle-shaped tumour cells in this sarcoma. Images in (b) show severely reduced blood flow accompanied by tumour cell shape changes and some dilated vessels and coagulation. Images in (c) show sustained blood flow reduction, more dilated, congested and coagulated vessels and extensive haemorrhage. The shaded areas in the upper panel indicate the extent of haemorrhage. Images in (d) show extensive necrosis (delineated in the upper panel) accompanied by very low blood flow, surrounded by a regrowing rim of tumour with flow values similar to controls. Figure adapted from reference [80]. Arrows indicate coagulation.

View larger version (129K): [in a new window]   Figure 4. A P22 rat tumour (4 mm diameter) growing in a dorsal skin flap "window" chamber surgically implanted into a BDIX rat before and 3 h after treatment with 10 mg kg–1 CA-4-P. Blood vessels are visualized by intravital microscopy under transmitted light using low power (upper panels) and high power (lower panels). After 3 h, when tumour blood flow is severely reduced (see Figures 2 and 3), blood vessels are clearly distended and there is significant haemorrhage especially around the tumour periphery.

View larger version (50K): [in a new window]   Figure 5. Vascular end-points, which will inform on the efficacy of antiangiogenic and antivascular drugs and which are accessible by clinically-applicable imaging techniques, are shown. Analysis of the initial tissue uptake kinetics of an intravenously administered contrast agent/radiotracer allows calculation of blood flow rate or the vascular permeability–surface area product, depending on whether the tissue uptake of the marker is flow or permeability limited. This will depend on characteristics of both the contrast agent itself and the vascular wall. Full quantification requires an arterial input function. The tissue/blood partition coefficient is the relative concentration of the agent in tissue and blood at equilibrium. The apparent tissue/blood partition coefficient can be accurately determined given relatively long imaging times and is equal to the true tissue/blood partition coefficient in well-perfused tissues. In poorly perfused tissue, it is reduced and reflects the perfused fraction of the tissue (see text). Measurement of the fraction of the tissue occupied by functional blood vessels (blood volume) is made using agents which are essentially confined to the vasculature. Analysis of venous blood samples allows for full quantification.