Human model of burn injury that quantifies the benefit of cooling as a first aid measure

BACKGROUND

Burn injuries are a major cause of morbidity and mortality worldwide. Cooling is widely practised as a first aid measure, but the efficacy of cooling burns in human skin has not been demonstrated. A safe, consistent, ethically acceptable model of burning and cooling in live human skin in vivo was developed, and used to quantify the effects of cooling.

METHODS

Novel apparatus was manufactured to create and cool burns in women who were anaesthetized for breast reconstruction surgery using a deep inferior epigastric artery perforator flap. Burns were excised between 1 and 3 h after creation, and analysed using histopathological assessment.

RESULTS

All 25 women who were approached agreed to take part in the study. There were no adverse events. Increased duration of contact led to increased burn depth, with a contact time of 7·5 s at 70°C leading to a mid-dermal burn. Burn depth progressed over time following injury, but importantly this was modified by cooling the burn at 16°C for 20 min. On average, cooling salvaged 25·2 per cent of the dermal thickness.

CONCLUSION

This study demonstrated the favourable effects of cooling on human burns. Public heath messaging should emphasize cooling as first aid for burns. This model will allow analysis of the molecular effects of cooling burns, and provide a platform for testing novel therapies aimed at reducing the impact of burn injury.

Improved urethral fluorescence during low rectal surgery: a new dye and a new method

BACKGROUND

The aim of this study was to demonstrate highlighting of the urethra during surgery through the use of two different methods: a new near-infrared fluorophore IRDye800BK, and indocyanine green (ICG) mixed with silicone.

METHODS

Male cadavers from the department of anatomy at the University of Oxford were used to visualise the urethra during near-infrared fluorescence excitation. To assess IRDye800BK, a perineal incision was utilised after infiltrating the urethra directly with an IRDye800BK solution mixed with Instillagel. ICG-silicone was assessed when the urethra was purposely exposed as part of a simulated transanal total mesorectal dissection. ICG was previously mixed with ethanol and silicone and left to set in a Foley catheter. Fluorescence was visualised using an in-house manufactured fluorescence-enabled laparoscopic system.

RESULTS

IRDye800BK demonstrated excellent penetration and visualisation of the urethra under fluorescence at an estimated tissue depth of 2 cm. An ICG-silicone catheter demonstrated excellent fluorescence without leaving any residual solution behind in the urethra after its removal.

CONCLUSIONS

The newly described ICG-silicone method opens up the possibility of new technologies in this area of fluorescence guided surgery. IRDye800BK is a promising alternative to ICG in visualising the urethra using fluorescence imaging. Its greater depth of penetration may allow earlier detection of the urethra during surgery and prevent wrong plane surgery sooner.

From interventionist imaging to intraoperative guidance: New perspectives by combining advanced tools and navigation with radio-guided surgery

The integration of medical imaging technologies into diagnostic and therapeutic approaches can provide a preoperative insight into both anatomical (e.g. using computed tomography, magnetic resonance imaging, or ultrasound), as well as functional aspects (e.g. using single photon emission computed tomography, positron emission tomography, lymphoscintigraphy, or optical imaging). Moreover, some imaging modalities are also used in an interventional setting (e.g. computed tomography, ultrasound, gamma or optical imaging) where they provide the surgeon with real-time information during the procedure. Various tools and approaches for image-guided navigation in cancer surgery are becoming feasible today. With the development of new tracers and portable imaging devices, these advances will reinforce the role of interventional molecular imaging.

The Development of Technology for Effective Respiratory-Gated Irradiation Using an Image-Guided Small Animal Irradiator

The development of image-guided small animal irradiators represents a significant improvement over standard irradiators by enabling preclinical studies to mimic radiotherapy in humans. The ability to deliver tightly collimated targeted beams, in conjunction with gantry or animal couch rotation, has the potential to maximize tumor dose while sparing normal tissues. However, the current commercial platforms do not incorporate respiratory gating, which is required for accurate and precise targeting in organs subject to respiration related motions that may be up to the order of 5 mm in mice. Therefore, a new treatment head assembly for the Xstrahl Small Animal Radiation Research Platform (SARRP) has been designed. This includes a fast X-ray shutter subsystem, a motorized beam hardening filter assembly, an integrated transmission ionization chamber to monitor beam delivery, a kinematically positioned removable beam collimator and a targeting laser exiting the center of the beam collimator. The X-ray shutter not only minimizes timing errors but also allows beam gating during imaging and treatment, with irradiation only taking place during the breathing cycle when tissue movement is minimal. The breathing related movement is monitored by measuring, using a synchronous detector/lock-in amplifier that processes diffuse reflectance light from a modulated light source. After thresholding of the resulting signal, delays are added around the inhalation/exhalation phases, enabling the "no movement" period to be isolated and to open the X-ray shutter. Irradiation can either be performed for a predetermined time of X-ray exposure, or through integration of a current from the transmission monitor ionization chamber (corrected locally for air density variations). The ability to successfully deliver respiratory-gated X-ray irradiations has been demonstrated by comparing movies obtained using planar X-ray imaging with and without respiratory gating, in addition to comparing dose profiles observed from a collimated beam on EBT3 radiochromic film mounted on the animal's chest. Altogether, the development of respiratory-gated irradiation facilitates improved dose delivery during animal movement and constitutes an important new tool for preclinical radiation studies. This approach is particularly well suited for irradiation of orthotopic tumors or other targets within the chest and abdomen where breathing related movement is significant.

Detecting intratumoral heterogeneity of EGFR activity by liposome-based in vivo transfection of a fluorescent biosensor

Despite decades of research in the epidermal growth factor receptor (EGFR) signalling field, and many targeted anti-cancer drugs that have been tested clinically, the success rate for these agents in the clinic is low, particularly in terms of the improvement of overall survival. Intratumoral heterogeneity is proposed as a major mechanism underlying treatment failure of these molecule-targeted agents. Here we highlight the application of fluorescence lifetime microscopy (FLIM)-based biosensing to demonstrate intratumoral heterogeneity of EGFR activity. For sensing EGFR activity in cells, we used a genetically encoded CrkII-based biosensor which undergoes conformational changes upon tyrosine-221 phosphorylation by EGFR. We transfected this biosensor into EGFR-positive tumour cells using targeted lipopolyplexes bearing EGFR-binding peptides at their surfaces. In a murine model of basal-like breast cancer, we demonstrated a significant degree of intratumoral heterogeneity in EGFR activity, as well as the pharmacodynamic effect of a radionuclide-labeled EGFR inhibitor in situ. Furthermore, a significant correlation between high EGFR activity in tumour cells and macrophage-tumour cell proximity was found to in part account for the intratumoral heterogeneity in EGFR activity observed. The same effect of macrophage infiltrate on EGFR activation was also seen in a colorectal cancer xenograft. In contrast, a non-small cell lung cancer xenograft expressing a constitutively active EGFR conformational mutant exhibited macrophage proximity-independent EGFR activity. Our study validates the use of this methodology to monitor therapeutic response in terms of EGFR activity. In addition, we found iNOS gene induction in macrophages that are cultured in tumour cell-conditioned media as well as an iNOS activity-dependent increase in EGFR activity in tumour cells. These findings point towards an immune microenvironment-mediated regulation that gives rise to the observed intratumoral heterogeneity of EGFR signalling activity in tumour cells in vivo.

Abstract P5-01-01: Lymphoid tissue inducer cells: Identification of a novel immune cell within the breast tumour microenvironment and its role in promoting tumour cell invasion

Within breast cancers, trans-endothelial migration of tumour cells through lymphatic vessels is the first step to tumour dissemination and lympho-vascular invasion has been shown to stratify breast cancer phenotypes into distinct prognostic groups. The exact molecular mechanisms mediating tumor cell entry and persistence within the lymphatic system remain unclear. Lymphoid tissue inducer (LTi) cells are members of the emerging family of retinoic acid related orphan receptor (ROR)gt+ innate lymphoid cells (ILCs), and their interaction with stromal cells induces production by the stromal cells of VEGF-C and “lymphoid” chemokines, essential for lymphoid organogenesis. We hypothesized that tumour cells manipulate the normal processes that govern chemokine-dependent, trans-lymphatic migration of immune cells, including LTi cells; shaping its microenvironment. Results: We analyzed the expression of lymphoid chemokines genes (CXCL12, CXCL13, CCL19, CCL20 and CCL21) and their corresponding receptors (CXCR4, CXCR5, CCR6 and CCR7) within the METABRIC (Molecular Taxonomy of Breast Cancer International Consortium) Tissue Bank. An unsupervised hierarchical cluster analysis revealed co-expression of these genes, categorizing breast tumors as relatively high/low expressors. Tumors exhibiting relatively high expression of these genes were found to be enriched for “basal-like” breast cancers according to PAM50 intrinsic subtype assignments. Immunofluorescence of the primary tumour sections identified cells that were comparable in phenotype to LTi cells. In a blinded study, we observed that patients with high LTi counts within the tumour microenvironment were also likely to have a gene expression corresponding to high expression for the lymphoid chemokines. IHC for the lymphatic marker, podoplanin found that the LTi count correlated with both an increased lymphatic vessel density and tumor invasion into lymphatic vessels. Within the basal and HER2+ve subtypes, patients with more than 4 lymph nodes were found to exhibit higher numbers of intratumoural LTi cells. In vitro studies, alongside multi-photon in vivo imaging were performed to investigate the interaction between intra-tumoural LTi and mesenchymal stromal cells. CXCL13 was shown to be essential for LTi clustering around stromal cells in vitro, and, the administration of a blocking antibody in vivo delayed the onset of lymph node metastasis in a murine mammary tumour (4T1.2) model. CXCLl3 has been identified as having independent prognostic significance in breast cancer, but we and others report that breast cancer cell lines are not the source of CXCL13. We show that an increase in stromal CXCL13 concentration within the tumour microenvironment following LTi recruitment promotes an EMT phenotype in the 4T1.2 cancer cell line, possibly via activation of the RANKL/RANK axis promoting tumorigenesis. We report for the first time, the identification of LTi cells within the human breast cancer tumour microenvironment and propose a pivotal role for these cells, through stromal cell interactions in the tumour microenvironment, in facilitating lymphatic invasion of tumour cells by modulation of the local lymphoid chemokine profile.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-01-01.

"Broadbeam" irradiation of mammalian cells using a vertical microbeam facility

A "broadbeam" facility is demonstrated for the vertical microbeam at Surrey's Ion Beam Centre, validating the new technique used by Barazzuol et al. (Radiat Res 177:651-662, 2012). Here, droplets with a diameter of about 4 mm of 15,000 mammalian cells in suspension were pipetted onto defined locations on a 42-mm-diameter cell dish with each droplet individually irradiated in "broadbeam" mode with 2 MeV protons and 4 MeV alpha particles and assayed for clonogenicity. This method enables multiple experimental data points to be rapidly collected from the same cell dish. Initially, the Surrey vertical beamline was designed for the targeted irradiation of single cells with single counted ions. Here, the benefits of both targeted single-cell and broadbeam irradiations being available at the same facility are discussed: in particular, high-throughput cell irradiation experiments can be conducted on the same system as time-intensive focused-beam experiments with the added benefits of fluorescent microscopy, cell recognition and time-lapse capabilities. The limitations of the system based on a 2 MV tandem accelerator are also discussed, including the uncertainties associated with particle Poisson counting statistics, spread of linear energy transfer in the nucleus and a timed dose delivery. These uncertainties are calculated with Monte Carlo methods. An analysis of how this uncertainty affects relative biological effect measurements is made and discussed.

Abstract P2-10-29: Time dependent breast cancer metastasis prediction using novel biological imaging, clinico-pathological and genomic data combined with Bayesian modeling to reduce over-fitting and improve on inter-cohort reproducibility

Background: Breast cancer heterogeneity demands that prognostic models must be biologically driven and recent clinical evidence indicates that future prognostic signatures need evaluation in the context of early versus late metastatic risk prediction. The aim of our work was to identify biologically validated quantitative imaging parameters with improved correlation to clinical outcome, and to address some of the remaining obstacles for a truly robust prognostic model in clinical use.

Method: We identified 4 seed proteins (ezrin/radixin/moesin-cofilin), along with several kinases as biologically relevant subnetwork of proteins that control tumor cell motility and metastasis. Patient-derived breast cancer tumour samples were used to perform a combination of imaging methods such as Fluoresecence lifetime imaging microscopy, automated segmentation and co-localisation intensity analysis. A complexity optimized Bayesian proportional hazard regression model was performed on a total of 419 breast cancer patients to validate time dependent predictions using traditional clinicopathological, genomic and our novel optical imaging-derived parameters. An independent dataset of 300 patient samples from the Leeds Institute of Molecular Medicine is currently being evaluated, representing a large cross centre validation of our integrated model.

Results: We demonstrate that the traditional gold standard clinico-pathological variables are poor predictors for patients that survive long periods, and that their predictive significance (in terms of hazard ratios) varies significantly between two temporal cohorts where the adjuvant treatments are vastly different. Moreover, we investigate the predictive accuracy of a combined imaging/clinicopathological model compared with genomic/clinicopathological models. We demonstrate how to reduce over-fitting to help improve the performance of prognostic models. Results of an integrated model combining genomic and imaging parameters are still awaited.

Discussion: We have produced the first optical imaging-derived multivariate tumour metastatic signature, which measures underlying key biological variables involved in regulating cancer cell motility. Using Bayesian proportional hazards regression in a time-dependent manner, we highlight the inadequacies of existing prediction tools and present a model combining the clinicopathological parameters with our imaging-based metastatic signature, as an integrative reproducible prognostic tool across different temporal cohorts.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-29.

Revisiting the ultra-high dose rate effect: implications for charged particle radiotherapy using protons and light ions

OBJECTIVE

To reinvestigate ultra-high dose rate radiation (UHDRR) radiobiology and consider potential implications for hadrontherapy.

METHODS

A literature search of cellular UHDRR exposures was performed. Standard oxygen diffusion equations were used to estimate the time taken to replace UHDRR-related oxygen depletion. Dose rates from conventional and novel methods of hadrontherapy accelerators were considered, including spot scanning beam delivery, which intensifies dose rate.

RESULTS

The literature findings were that, for X-ray and electron dose rates of around 10(9) Gy s(-1), 5-10 Gy depletes cellular oxygen, significantly changing the radiosensitivity of cells already in low oxygen tension (around 3 mmHg or 0.4 kPa). The time taken to reverse the oxygen depletion of such cells is estimated to be over 20-30 s at distances of over 100 μm from a tumour blood vessel. In this time window, tumours have a higher hypoxic fraction (capable of reducing tumour control), so the next application of radiation within the same fraction should be at a time that exceeds these estimates in the case of scanned beams or with ultra-fast laser-generated particles.

CONCLUSION

This study has potential implications for particle therapy, including laser-generated particles, where dose rate is greatly increased. Conventional accelerators probably do not achieve the critical UHDRR conditions. However, specific UHDRR oxygen depletion experiments using proton and ion beams are indicated.

The challenges of integrating molecular imaging into the optimization of cancer therapy

We review novel, in vivo and tissue-based imaging technologies that monitor and optimize cancer therapeutics. Recent advances in cancer treatment centre around the development of targeted therapies and personalisation of treatment regimes to individual tumour characteristics. However, clinical outcomes have not improved as expected. Further development of the use of molecular imaging to predict or assess treatment response must address spatial heterogeneity of cancer within the body. A combination of different imaging modalities should be used to relate the effect of the drug to dosing regimen or effective drug concentration at the local site of action. Molecular imaging provides a functional and dynamic read-out of cancer therapeutics, from nanometre to whole body scale. At the whole body scale, an increase in the sensitivity and specificity of the imaging probe is required to localise (micro)metastatic foci and/or residual disease that are currently below the limit of detection. The use of image-guided endoscopic biopsy can produce tumour cells or tissues for nanoscopic analysis in a relatively patient-compliant manner, thereby linking clinical imaging to a more precise assessment of molecular mechanisms. This multimodality imaging approach (in combination with genetics/genomic information) could be used to bridge the gap between our knowledge of mechanisms underlying the processes of metastasis, tumour dormancy and routine clinical practice. Treatment regimes could therefore be individually tailored both at diagnosis and throughout treatment, through monitoring of drug pharmacodynamics providing an early read-out of response or resistance.

Time-lapse FRET microscopy using fluorescence anisotropy

We present recent data on dynamic imaging of Rac1 activity in live T-cells. Förster resonance energy transfer between enhanced green and monomeric red fluorescent protein pairs which form part of a biosensor molecule provides a metric of this activity. Microscopy is performed using a multi-functional high-content screening instrument using fluorescence anisotropy to provide a means of monitoring protein-protein activity with high temporal resolution. Specifically, the response of T-cells upon interaction of a cell surface receptor with an antibody coated multi-well chamber was measured. We observed dynamic changes in the activity of the biosensor molecules with a time resolution that is difficult to achieve with traditional methodologies for observing Förster resonance energy transfer (fluorescence lifetime imaging using single photon counting or frequency domain techniques) and without spectral corrections that are normally required for intensity based methodologies.

Use of novel optical proteomics to profile breast cancer patients leading to individualised prognosis and tailored treatment

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Background: Optical proteomics quantifies interactions between proteins and post-translational modifications by measuring Förster resonance energy transfer (FRET) quantified by fluorescence lifetime imaging microscopy (FLIM). This project aims to derive multiple high throughput optical proteomic markers, to predict metastatic risk at first diagnosis, and to perturb ‘high risk' protein-protein interactions using targeted therapeutics. This initial step develops robust FRET/FLIM assays, suitable for use in formalin fixed paraffin embedded (FFPE) tissue to be correlated with patient outcome. Methods: Fluorophore-conjugated antibodies to proteins involved in cell migration and survival, were applied to tissue microarrays (TMA), created from archived FFPE invasive ductal breast carcinoma samples. Where fluorophores are located within nanometer proximity, FRET occurs, thus allowing quantification of protein-protein interaction. Ezrin and PKCα phosphorylation, distribution, and interaction were imaged on four TMAs (patients diagnosed with early breast cancer 1984 -1987: 20 years follow-up data). Results: 71 patient samples were optically imaged. Patients were clustered based on the pairwise distances between 18 optical variables ‘input data'. Data are represented on self organising maps and dendrograms and correlated with clinical outcome ‘output data', displaying a heatmap distribution. Conclusions: Ezrin and PKCα phosphorylation, distribution, and interaction imaged optically within FFPE contain prognostic information regarding metastatic outcome in breast cancer, thus stepping ever closer to individualising prognosis. These advanced optics-based parameters informing on metastatic potential will be validated in prospective studies in conjunction with FRET/FLIM assays measuring HER2/HER3 dimerisation, and EGFR and HER2 ubiquitination in order to improve patient selection for targeted therapy.

No significant financial relationships to disclose.

Tumour vascular disrupting agents: combating treatment resistance

A large group of tubulin-binding microtubule-depolymerizing agents act as tumour vascular disrupting agents (VDAs). Several members of this group are now in clinical trials in combination with conventional anticancer drugs and radiotherapy. Here we briefly update on the development of tubulin-binding combretastatins as VDAs, summarize what is known of their mechanisms of action and address issues relating to treatment resistance, using disodium combretastatin A-4 3-O-phosphate (CA-4-P) as an example. Characteristically, VDAs cause a rapid shutdown of blood flow to tumour tissue with much less effect in normal tissues. However, the tumour rim is relatively resistant to treatment. Hypoxia (or hypoxia reoxygenation) induces upregulation of genes associated with angiogenesis and drug resistance. It may be possible to take advantage of treatment-induced hypoxia by combining with drugs that are activated under hypoxic conditions. In summary, VDAs provide a novel approach to cancer treatment, which should effectively complement standard treatments, if treatment resistance is addressed by judicious combination treatment strategies.

Multiphoton time-domain fluorescence lifetime imaging microscopy: practical application to protein–protein interactions using global analysis

Förster resonance energy transfer (FRET) detected via fluorescence lifetime imaging microscopy (FLIM) and global analysis provide a way in which protein–protein interactions may be spatially localized and quantified within biological cells. The FRET efficiency and proportion of interacting molecules have been determined using bi-exponential fitting to time-domain FLIM data from a multiphoton time-correlated single-photon counting microscope system. The analysis has been made more robust to noise and significantly faster using global fitting, allowing higher spatial resolutions and/or lower acquisition times. Data have been simulated, as well as acquired from cell experiments, and the accuracy of a modified Levenberg–Marquardt fitting technique has been explored. Multi-image global analysis has been used to follow the epidermal growth factor-induced activation of Cdc42 in a short-image-interval time-lapse FLIM/FRET experiment. Our implementation offers practical analysis and time-resolved-image manipulation, which have been targeted towards providing fast execution, robustness to low photon counts, quantitative results and amenability to automation and batch processing.

Substrate evaluation for a microbeam endstation using unstained cell imaging

A cellular imaging system, optimized for unstained cells seeded onto a thin substrate, is under development. This system will be a component of the endstation for the microbeam cell-irradiation facility at the University of Surrey. Previous irradiation experiments at the Gray Cancer Institute (GCI) have used Mylar film to support the cells [Folkard, M., Prise, K., Schettino, G., Shao, C., Gilchrist, S., Vojnovic, B., 2005. New insights into the cellular response to radiation using microbeams. Nucl. Instrum. Methods B 231, 189-194]. Although suitable for fluorescence microscopy, the Mylar often creates excessive optical noise when used with non-fluorescent microscopy. A variety of substrates are being investigated to provide appropriate optical clarity, cell adhesion, and radiation attenuation. This paper reports on our investigations to date.

Bevacizumab, a vascular endothelial growth factor (VEGF) specific antibody reduces interstitial fluid pressure (IFP) in human rectal cancer xenograft (HT29) by day 5: Is this evidence for rescheduling its timing relative to chemotherapy?

4043

Background: Interstitial fluid pressure (IFP) of most solid tumours is increased relative to normal tissues; this is thought to be associated with the development of structurally and functionally abnormal blood and lymphatic vessels and interstitial fibrosis. Such interstitial hypertension creates a barrier for tumour transvascular transport, consequently compromising the delivery and efficacy of chemotherapy. We investigated the effect of Bevacizumab on IFP of a human rectal cancer xenograft. Methods: SCID mice bearing subcutaneous HT29 tumours of =8.5 mm diameter received a single dose of 10 mg/kg Bevacizumab intraperitoneally; controls received saline. Tumour IFP was measured in sedated mice (Hypnorm) on days 1, 3 and 5 post injection, using the wick-in-needle technique. Experiments were conducted under Home Office licence and approved by the local ethical committee. Results: Groups of 8 treated and control tumours were examined on days 1, 3 and 5 (n = 48). IFP was significantly lower (p<0.0001) on day 5 in treated than control tumours (mean ± SD 15.1 ± 4.7 cf 36.9 ± 5.6 mm Hg). No significant differences (p>0.05) between treated and control groups were seen on day 1 (31.8 ± 3.5 cf 30.6 ± 3.1 mm Hg) or day 3 (33.4 ± 5.5 cf 31.5 ± 3.2 mm Hg). No data were acquired on day 7 as the tumours ulcerated. Conclusions: Our data show that Bevacizumab causes a significant reduction of tumour IFP, but not until 5 days after treatment. Reduced IFP could augment uptake of cytotoxic drugs into tumour cells, hence timing of Bevacizumab relative to the first dose of chemotherapy could be of critical importance.

No significant financial relationships to disclose.

Profiling cytochrome P450 CYP1 enzyme expression in primary melanoma and disseminated disease utilizing spectral imaging microscopy (SIM)

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Background: The aim of this study was to profile cytochrome CYP1 family (CYP1A1/1A2, and CYP1B1) mono-oxygenase enzymes during the malignant progression of primary melanoma and metastatic disease. Methods: Tissue microarrays of primary (n = 75), and metastatic (n = 104) melanoma were constructed with the patient demographics: (1) primary melanoma; age 22 to 93 (median 59); sex M/F 36/44; Breslow thickness 0.4 to 15 mm (median 2.5 mm); ulceration 25/80, and (2) metastatic melanoma; age 26 to 92 (median 60 mm); sex M/F 54/49; ulceration 30/104; number of nodes 1 to 15 (median 2); extra-capsular spread 20/95. CYP1 protein was detected by IHC using validated selective poly- and monoclonal antibodies. Vector SG (grey) stain for CYP1 was used with nuclear fast red counterstain to aid spectral resolution from background melanin. Staining intensity was scored visually (negative 0, weak 1, moderate 2, strong 3) and using SIM at every pixel of a captured image of each melanoma core. Reference spectra of individual chromophores were used to spectrally ‘un-mix’ CYP1 staining before the mean normalised absorbance intensity was determined. Grading was by the 2002 AJCC classification system: primary stage I n = 27 (1A 8, 1B 19), and stage II n = 48 (2A 22, 2B 16, 2C 10), lymph node metastasis stage III n = 98 (3B 53, 3C 45), visceral metastasis stage IV n = 6. Normal skin (n = 27), benign naevi (n = 14), and dysplastic naevi (n = 21) were also included. Results: CYP1B1 was not in normal skin but was over-expressed in both primary and metastatic melanoma (visual: 71% & 65%, SIM: 91% & 83%). Primary melanoma (stage I & II) was significantly greater (p = 0.004) than metastasis (stage III & IV). CYP1B1 did not correlate with ulceration or Breslow thickness but did correlate with N stage lymph node metastasis (p = 0.005). CYP1B1 expression in dysplastic naevi indicated up-regulation at an early stage of melanoma progression. CYP1A1/1A2 was not expressed in normal skin nor primary/metastatic melanoma. Conclusions: CYP1B1 protein expression is maintained with advancing AJCC stage from primary through to visceral metastasis. Future work will seek to correlate protein expression with functionality with a view to exploiting CYP1B1 in the enzyme/prodrug therapy of malignant melanoma.

No significant financial relationships to disclose.

Time-correlated single-photon counting fluorescence lifetime confocal imaging of decayed and sound dental structures with a white-light supercontinuum source

We report the demonstration of time-correlated single-photon counting (TCSPC) fluorescence lifetime imaging (FLIM) to ex vivo decayed and healthy dentinal tooth structures, using a white-light supercontinuum excitation source. By using a 100 fs-pulsed Ti:Sapphire laser with a low-frequency chirp to pump a 30-cm long section of photonic crystal fibre, a ps-pulsed white-light supercontinuum was created. Optical bandpass interference filters were then applied to this broad-bandwidth source to select the 488-nm excitation wavelength required to perform TCSPC FLIM of dental structures. Decayed dentine showed significantly shorter lifetimes, discriminating it from healthy tissue and hard, stained and thus affected but non-infected material. The white-light generation source provides a flexible method of producing variable-bandwidth visible and ps-pulsed light for TCSPC FLIM. The results from the dental tissue indicate a potential method of discriminating diseased tissue from sound, but stained tissue, which could be of crucial importance in limiting tissue resection during preparation for clinical restorations.

Technique for measurement of fluorescence lifetime by use of stroboscopic excitation and continuous-wave detection

A study of the practicality a simple technique for obtaining time-domain information that uses continuous wave detection of fluorescence is presented. We show that this technique has potential for use in assays for which a change in the lifetime of an indicator occurs in reaction to an analyte, in fluorescence resonance energy transfer, for example, and could be particularly important when one is carrying out such measurements in the scaled-down environment of a lab on a chip (biochip). A rate-equation model is presented that allows an objective analysis to be made of the relative importance of the key measurement parameters: optical saturation of the fluorophore and period of the excitation pulse. An experimental demonstration of the technique that uses a cuvette-based analysis of a carbocyanine dye and for which the excitation source is a 650 nm wavelength, self-pulsing AlGaInP laser diode is compared with the model.

Advanced microscopy solutions for monitoring the kinetics and dynamics of drug-DNA targeting in living cells

Many anticancer drugs require interaction with DNA or chromatin components of tumor cells to achieve therapeutic activity. Quantification and exploration of drug targeting dynamics can be highly informative in the rational development of new therapies and in the drug discovery pipeline. The problems faced include the potential infrequency and transient nature of critical events, the influence of micropharmacokinetics on the drug-target equilibria, the dependence on preserving cell function to demonstrate dynamic processes in situ, the need to map events in functional cells and the confounding effects of cell-to-cell heterogeneity. We demonstrate technological solutions in which we have integrated two-photon laser scanning microscopy (TPLSM) to track drug delivery in subcellular compartments, with the mapping of sites of critical molecular interactions. We address key design concepts for the development of modular tools used to uncover the complexity of drug targeting in single cells. First, we describe the combination of two-photon excitation with fluorescence lifetime imaging microscopy (FLIM) to map the nuclear docking of the anticancer drug topotecan (TPT) at a subset of DNA sites in nuclear structures of live breast tumor cells. Secondly, we demonstrate how we incorporate the smart design of a two-photon 'dark' DNA binding probe, such as DRAQ5, as a well-defined quenching probe to uncover sites of drug interaction. Finally, we discuss the future perspectives on introducing these modular kinetic assays in the high-content screening arena and the interlinking of the consequences of drug-target interactions with cellular stress responses.

Imaging protein–protein interactions in cell motility using fluorescence resonance energy transfer (FRET)

Protein–protein interactions and signal transduction pathways have traditionally been analysed using biochemical techniques or standard microscopy. Although invaluable in the delineation of protein hierarchy, these methods do not provide information on the true spatial and temporal nature of complex formation within the intact cell. Recent advances in microscopy have allowed the development of new methods to analyse protein–protein interactions at very high resolution in both fixed and live cells. The present paper provides a brief overview of using fluorescence resonance energy transfer to analyse directly molecular interactions and conformational changes in various proteins involved in the regulation of cell adhesion and motility.

Low-Dose Studies of Bystander Cell Killing with Targeted Soft X Rays

The Gray Cancer Institute ultrasoft X-ray microprobe was used to quantify the bystander response of individual V79 cells exposed to a focused carbon K-shell (278 eV) X-ray beam. The ultrasoft X-ray microprobe is designed to precisely assess the biological response of individual cells irradiated in vitro with a very fine beam of low-energy photons. Characteristic CK X rays are generated by a focused beam of 10 keV electrons striking a graphite target. Circular diffraction gratings (i.e. zone plates) are then employed to focus the X-ray beam into a spot with a radius of 0.25 microm at the sample position. Using this microbeam technology, the correlation between the irradiated cells and their nonirradiated neighbors can be examined critically. The survival response of V79 cells irradiated with a CK X-ray beam was measured in the 0-2-Gy dose range. The response when all cells were irradiated was compared to that obtained when only a single cell was exposed. The cell survival data exhibit a linear-quadratic response when all cells were targeted (with evidence for hypersensitivity at low doses). When only a single cell was targeted within the population, 10% cell killing was measured. In contrast to the binary bystander behavior reported by many other investigations, the effect detected was initially dependent on dose (<200 mGy) and then reached a plateau (>200 mGy). In the low-dose region (<200 mGy), the response after irradiation of a single cell was not significantly different from that when all cells were exposed to radiation. Damaged cells were distributed uniformly over the area of the dish scanned (approximately 25 mm2). However, critical analysis of the distance of the damaged, unirradiated cells from other damaged cells revealed the presence of clusters of damaged cells produced under bystander conditions.

Semi-automated software for the three-dimensional delineation of complex vascular networks

The understanding of tumour angiogenesis is of great importance in cancer research, as is the tumour response to vascular-targeted drugs. This paper presents software aimed at aiding these investigations and other situations where linear or dendritic structures are to be delineated from three-dimensional (3D) data sets. This software application was written to analyse the data from 3D data sets by allowing the manual and semi-automated tracking and delineation of the vascular tree, including the measurement of vessel diameter. A new algorithm, CHARM, based on a compact Hough transform and the formation of a radial map, has been used to locate vessel centres and measure diameters automatically. The robustness of this algorithm to image smoothing and noise has been investigated.

Investigating the cellular effects of isolated radiation tracks using microbeam techniques

Studies of the effects of radiation at the cellular level have generally been carried out by exposing cells randomly to the charged-particle tracks of a radiation beam. Recently, a number of laboratories have developed techniques for microbeam irradiation of individual cells. These approaches are designed to remove much of the randomness of conventional methods and allow the nature of the targets and pathways involved in a range of radiation effects to be studied with greater selectivity. Another advantage is that the responses of individual cells can be followed in a time-lapse fashion and, for example, processes such as "bystander" effects can be studied clearly. The microbeam approach is of particular importance in mechanistic studies related to the risks associated with exposure to low fluences of charged particles. This is because it is now possible to determine the actions of strictly single particle tracks and thereby mimic, under in vitro conditions, exposures at low radiation dose that are significant for protection levels, especially those involving medium- to high-LET radiations. Overall, microbeam methods provide a new dimension in exploring mechanisms of radiation effect at the cellular level. Microbeam methods and their application to the study of the cellular effects of single charged-particle traversals are described.

Upgrading of the Gray Laboratory soft X ray microprobe and V79 survival measurements following irradiation of one or all cells with a CK X ray beam of different size

The X ray microprobe developed at the Gray Laboratory was originally designed to produce carbon K X rays (278 eV) by electron bombardment and focus them to a few hundred nanometers spot by using a circular diffraction grating with increasing line density (zone plate). The very fine focus achieved (< 0.25 micron radius spot) and the highly localised energy deposition of CK X rays (photoelectron range < 7 nm), represent unique tools to investigate modern radiobiological phenomena. Recent improvements have been directed to increase the dose rate (up to approximately 6 Gy.s-1 entrance dose averaged over a typical V79 cell) and to evaluate the possibility of using higher energy photons (AlK of 1.48 keV). The efficiency of the microprobe system has been tested by assessing the clonogenic potential of V79 cells irradiated with CK X ray beams of different sizes (5 and 0.25 microns radius) and investigating the relevance of the spatial distribution of cells for the bystander effect.

A focused ultrasoft x-ray microbeam for targeting cells individually with submicrometer accuracy

The application of microbeams is providing new insights into the actions of radiation at the cell and tissue levels. So far, this has been achieved exclusively through the use of collimated charged particles. One alternative is to use ultrasoft X rays, focused by X-ray diffractive optics. We have developed a unique facility that uses 0.2-0.8-mm-diameter zone plates to focus ultrasoft X rays to a beam of less than 1 microm diameter. The zone plate images characteristic K-shell X rays of carbon or aluminum, generated by focusing a beam of 5-10 keV electrons onto the appropriate target. By reflecting the X rays off a grazing-incidence mirror, the contaminating bremsstrahlung radiation is reduced to 2%. The focused X rays are then aimed at selected subcellular targets using rapid automated cell-finding and alignment procedures; up to 3000 cells per hour can be irradiated individually using this arrangement.

Low-dose hypersensitivity in Chinese hamster V79 cells targeted with counted protons using a charged-particle microbeam

The Gray Laboratory charged-particle microbeam has been used to assess the clonogenic ability of Chinese hamster V79 cells after irradiation of their nuclei with a precisely defined number of protons with energies of 1.0 and 3.2 MeV. The microbeam uses a 1-microm silica capillary collimator to deliver protons to subcellular targets with high accuracy. The detection system is based on a miniature photomultiplier tube positioned above the cell dish, which detects the photons generated by the passage of the charged particles through an 18-microm-thick scintillator placed below the cells. With this system, a detection efficiency of greater than 99% is achieved. The cells are plated on specially designed dishes (3-microm-thick Mylar base), and the nuclei are identified by fluorescence microscopy. After an incubation period of 3 days, the cells are revisited individually to assess the formation of colonies from the surviving cells. For each energy investigated, the survival curve obtained for the microbeam shows a significant deviation below 1 Gy from a response extrapolated using the LQ model for the survival data above 1 Gy. The data are well fitted by a model that supports the hypothesis that radioresistance is induced by low-dose hypersensitivity. These studies demonstrate the potential of the microbeam for performing studies of the effects of single charged particles on cells in vitro. The hypersensitive responses observed are comparable with those reported by others using different radiations and techniques.

Mechanisms associated with tumor vascular shut-down induced by combretastatin A-4 phosphate: intravital microscopy and measurement of vascular permeability

The tumor vascular effects of the tubulin destabilizing agent disodium combretastatinA-4 3-O-phosphate (CA-4-P) were investigated in the rat P22 tumor growing in a dorsal skin flap window chamber implanted into BD9 rats. CA-4-P is in clinical trial as a tumor vascular targeting agent. In animal tumors, it can cause the shut-down of blood flow, leading to extensive tumor cell necrosis. However, the mechanisms leading to vascular shut-down are still unknown. Tumor vascular effects were visualized and monitored on-line before and after the administration of two doses of CA-4-P (30 and 100 mg/kg) using intravital microscopy. The combined effect of CA-4-P and systemic nitric oxide synthase (NOS) inhibition using N(omega)-nitro-L-arginine (L-NNA) was also assessed, because this combination has been shown previously to have a potentiating effect. The early effect of CA-4-P on tumor vascular permeability to albumin was determined to assess whether this could be involved in the mechanism of action of the drug. Tumor blood flow reduction was extremely rapid after CA-4-P treatment, with red cell velocity decreasing throughout the observation period and dropping to <5% of the starting value by 1 h. NOS inhibition alone caused a 50% decrease in red cell velocity, and the combined treatment of CA-4-P and NOS inhibition was approximately additive. The mechanism of blood flow reduction was very different for NOS inhibition and CA-4-P. That of NOS inhibition could be explained by a decrease in vessel diameter, which was most profound on the arteriolar side of the tumor circulation. In contrast, the effects of CA-4-P resembled an acute inflammatory reaction resulting in a visible loss of a large proportion of the smallest blood vessels. There was some return of visible vasculature at 1 h after treatment, but the blood in these vessels was static or nearly so, and many of the vessels were distended. The hematocrit within larger draining tumor venules tended to increase at early times after CA-4-P, suggesting fluid loss from the blood. The stacking of red cells to form rouleaux was also a common feature, coincident with slowing of blood flow; and these two factors would lead to an increase in viscous resistance to blood flow. Tumor vascular permeability to albumin was increased to approximately 160% of control values at 1 and 10 min after treatment. This could lead to an early decrease in tumor blood flow via an imbalance between intravascular and tissue pressures and/or an increase in blood viscosity as a result of increased hematocrit. These results suggest a mechanism of action of CA-4-P in vivo. Combination of CA-4-P with a NOS inhibitor has an additive effect, which it may be possible to exploit therapeutically.

Measurement of tumor oxygenation: in vivo comparison of a luminescence fiber-optic sensor and a polarographic electrode in the p22 tumor

Hypoxia is important in tumor biology and therapy. This study compared the novel luminescence fiber-optic OxyLite sensor with the Eppendorf polarographic electrode in measuring tumor oxygenation. Using the relatively well-oxygenated P22 tumor, oxygen measurements were made with both instruments in the same individual tumors. In 24 air-breathing animals, pooled electrode pO(2) readings lay in a range over twice that of sensor pO(2(5min)) values (-3.2 to 80 mm Hg and -0.1 to 34.8 mm Hg, respectively). However, there was no significant difference between the means +/- 2 SE of the median pO(2) values recorded by each instrument (11.0 +/- 3.3 and 8.1 +/- 1.9 mm Hg, for the electrode and sensor respectively, P = 0.07). In a group of 12 animals treated with carbon monoxide inhalation to induce tumor hypoxia, there was a small but significant difference between the means +/- 2 SE of the median pO(2) values reported by the electrode and sensor (1.7 +/- 0.9 and 2.9 +/- 0.7 mm Hg, respectively, P = 0.009). A variable degree of disparity was seen on comparison of pairs of median pO(2) values from individual tumors in both air-breathing and carbon monoxide-breathing animals. Despite the differences between the sets of readings made with each instrument from individual tumors, we have shown that the two instruments provide comparable assessments of tumor oxygenation in groups of tumors, over the range of median pO(2) values of 0.6 to 28.1 mm Hg.

Effects of combretastatin A4 phosphate on endothelial cell morphology in vitro and relationship to tumour vascular targeting activity in vivo

BACKGROUND

Combretastatin A4 Phosphate (CA4P) is a tubulin binding agent which causes rapid tumour vascular shutdown. It has anti-proliferative and apoptotic effects on dividing endothelial cells after prolonged exposure, but these effects occur on a much longer time scale than the reduction in tumour blood flow. This study compared the time course of CA4P effects on endothelial cell shape and reduction in red cell velocity.

METHODS

Endothelial cell area and form factor (1-4 pi x area x perimeter-2) were measured for proliferating and confluent HUVECs after CA4P treatment. Recovery of shape after CA4P and colchicine was compared. Window chamber studies of tumours were used to measure red cell velocity. Results 70% reduction in red cell velocity and 44% reduction in HUVEC form factor occurred by 10 minutes. Proliferating HUVECs underwent greater cell shape change after CA4P, which occurred at lower doses than for confluent cells. Cell shape recovered 24 hours after 30 minutes exposure to CA4P, but not after colchicine.

CONCLUSIONS

The similar time course of cell shape change and red cell velocity reduction suggests endothelial cell shape change may be involved early in the in vivo events leading to vascular shutdown. Differences in the recovery from the shape changes induced by CA4P and colchicine could underlie the different toxicity profiles of these drugs.

Automated counting of mammalian cell colonies

Investigating the effect of low-dose radiation exposure on cells using assays of colony-forming ability requires large cell samples to maintain statistical accuracy. Manually counting the resulting colonies is a laborious task in which consistent objectivity is hard to achieve. This is true especially with some mammalian cell lines which form poorly defined or 'fuzzy' colonies, typified by glioma or fibroblast cell lines. A computer-vision-based automated colony counter is presented in this paper. It utilizes novel imaging and image-processing methods involving a modified form of the Hough transform. The automated counter is able to identify less-discrete cell colonies typical of these cell lines. The results of automated colony counting are compared with those from four manual (human) colony counts for the cell lines HT29, A172, U118 and IN1265. The results from the automated counts fall well within the distribution of the manual counts for all four cell lines with respect to surviving fraction (SF) versus dose curves, SF values at 2 Gy (SF2) and total area under the SF curve (Dbar). From the variation in the counts, it is shown that the automated counts are generally more consistent than the manual counts.

Optical sensor-based oxygen tension measurements correspond with hypoxia marker binding in three human tumor xenograft lines

Hypoxia has a negative effect on the outcome of radiotherapy and surgery and is also related to an increased incidence of distant metastasis. In this study, tumor pO(2) measurements using a newly developed time-resolved luminescence-based optical sensor (OxyLitetrade mark) were compared with bioreductive hypoxia marker binding (pimonidazole). Single pO(2) measurements per tumor were compared to hypoxia marker binding in tissue sections using image analysis. Both assays were performed in the same tumors of three human tumor lines grown as xenografts. Both assays demonstrated statistically significant differences in the oxygenation status of the three tumor lines. There was also a good correlation between hypoxia marker binding and the pO(2) measurements with the OxyLitetrade mark device. A limitation of the OxyLitetrade mark system is that it is not yet suited for sampling multiple sites in one tumor. An important strength is that continuous measurements can be taken at the same position and dynamic information on the oxygenation status of tumors can be obtained. The high spatial resolution of the hypoxia marker binding method can complement the limitations of the OxyLitetrade mark system. In the future, a bioreductive hypoxic cell marker for global assessment of tumor hypoxia may be combined with analysis of temporal changes in pO(2) with the OxyLitetrade mark to study the effects of oxygenation-modifying treatment on an individual basis.

Critical energies for SSB and DSB induction in plasmid DNA by low-energy photons: action spectra for strand-break induction in plasmid DNA irradiated in vacuum

PURPOSE

To measure action spectra for the induction of single-strand breaks (SSB) and double-strand breaks (DSB) in plasmid DNA by low-energy photons and provide estimates for the energy dependence of strand-break formation important for track-structure simulations of DNA damage.

MATERIALS AND METHODS

Plasmid pMSG-CAT was irradiated as a monolayer, under vacuum, with 7 150eV photons produced by a synchrotron source. Yields of SSB and DSB were determined by the separation of the three plasmid forms by gel electrophoresis.

RESULTS

The yields of SSB per incident photon increased from 1.4x 10(-15) SSB per plasmid per photon/cm2 at 7eV to 7.5 x 10(-14) SSB per plasmid per photon/cm2 at 150 eV. Direct induction of DSB was also detected increasing from 3.4 x 10(-17) DSB per plasmid per photon/cm2 at 7eV to 4.1 x 10(-15) DSB per plasmid per photon/cm2 at 150eV. When the absorption cross-section of the DNA was considered, the quantum efficiency for break formation increased over the energy range studied. Over the entire energy range, the ratio of SSB to DSB remained constant.

CONCLUSIONS

These studies provide evidence for the ability of photons as low as 7 eV to induce both SSB and DSB. The common action spectrum for both lesions suggests that they derive from the same initial photoproducts under conditions where the DNA is irradiated in vacuum and a predominantly direct effect is being observed. The spectral and dose-effect behaviour indicates that DSB are induced predominantly by single-event processes in the energy range covered.

Critical energies for ssb and dsb induction in plasmid DNA by vacuum-UV photons: an arrangement for irradiating dry or hydrated DNA with monochromatic photons

PURPOSE

Theoretical modelling techniques are often used to simulate the action of ionizing radiations on cells at the nanometre level. Using monoenergetic vacuum-UV (VUV) radiation to irradiate DNA either dry or humidified, the action spectra for the induction of DNA damage by low energy photons and the role of water and can be studied. These data provide inputs for the theoretical models.

METHODS

Various combinations of monochromator, grating and VUV window have been used to obtain monochromatic photons from the 2 GeV electron synchrotron at the CLRC, Daresbury Laboratory. A sample chamber containing plasmid DNA is installed at the end of the beamline. The chamber can be evacuated or water can be introduced (as water vapour or humidified helium). In this way, DNA can be irradiated either dry or humidified.

RESULTS

An arrangement for irradiating dry or humidified DNA using monoenergetic photons from 7 eV to 150 eV has been developed. At the energies used, exposure rates vary from about 5 x 10(10) to 3 x 10(12) photons cm(-2) s(-1) over a 1 cm2 sample area. At all but the lowest energies this is sufficient to produce significant levels of DNA damage in just a few minutes. The measured dose variation over the sample area is typically 30%, but this is reduced significantly using sample scanning techniques.

Sweat gland function as a measure of radiation change

BACKGROUND

Radiotherapy may result in dryness of the skin even when no other change can be detected. We describe a system for recording the electrical conductance of skin as a measure of sweat gland function.

PATIENTS AND METHODS

In 22 normal volunteers close agreement was obtained between measurements obtained from comparable sites on both sides of the chest. Measurements were subsequently made in 38 patients treated by radiotherapy to one side of the chest for tumours of the breast or lung using one of five different fractionation schedules. Simultaneous readings were obtained from both sides of the chest with the non irradiated side acting as a control.

RESULTS

A dose response relationship was demonstrated: five patients who received the equivalent total dose of 15 Gy in 2-Gy fractions showed no change in conductance. Sixteen out of 23 who received an equivalent total dose of 42-46 Gy in 2-Gy fractions had a greater than 22% reduction in mean skin conductance compared with that of the control areas despite the skin appearing normal in the large majority. Marked changes in skin conductance were seen after higher total doses. In a prospective study 18 women receiving breast irradiation underwent weekly readings during treatment. A mean reduction of 40% in skin conductance was noted by the end of the second week of treatment prior to any clinical evidence of radiation change. Skin conductance returned to normal in 44% of patients by 6 months. In the remainder, those patients who showed the greatest reduction in skin conductance during treatment demonstrated the least recovery.

CONCLUSIONS

Changes in sweat gland function can be detected and quantified in skin which may otherwise appear normal. Differences may so be demonstrated between areas treated using different fractionation schedules and the method may be applied to the detection during radiotherapy of unusually sensitive patient.

Combretastatin A-4 phosphate as a tumor vascular-targeting agent: early effects in tumors and normal tissues

The potential for tumor vascular-targeting by using the tubulin destabilizing agent disodium combretastatin A-4 3-0-phosphate (CA-4-P) was assessed in a rat system. This approach aims to shut down the established tumor vasculature, leading to the development of extensive tumor cell necrosis. The early vascular effects of CA-4-P were assessed in the s.c. implanted P22 carcinosarcoma and in a range of normal tissues. Blood flow was measured by the uptake of radiolabeled iodoantipyrine, and quantitative autoradiography was used to measure spatial heterogeneity of blood flow in tumor sections. CA-4-P (100 mg/kg i.p.) caused a significant increase in mean arterial blood pressure at 1 and 6 h after treatment and a very large decrease in tumor blood flow, which-by 6 h-was reduced approximately 100-fold. The spleen was the most affected normal tissue with a 7-fold reduction in blood flow at 6 h. Calculations of vascular resistance revealed some vascular changes in the heart and kidney for which there were no significant changes in blood flow. Quantitative autoradiography showed that CA-4-P increased the spatial heterogeneity in tumor blood flow. The drug affected peripheral tumor regions less than central regions. Administration of CA-4-P (30 mg/kg) in the presence of the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester, potentiated the effect of CA-4-P in tumor tissue. The combination increased tumor vascular resistance 300-fold compared with less than 7-fold for any of the normal tissues. This shows that tissue production of nitric oxide protects against the damaging vascular effects of CA-4-P. Significant changes in tumor vascular resistance could also be obtained in isolated tumor perfusions using a cell-free perfusate, although the changes were much less than those observed in vivo. This shows that the action of CA-4-P includes mechanisms other than those involving red cell viscosity, intravascular coagulation, and neutrophil adhesion. The uptake of CA-4-P and combretastatin A-4 (CA-4) was more efficient in tumor than in skeletal muscle tissue and dephosphorylation of CA-4-P to CA-4 was faster in the former. These results are promising for the use of CA-4-P as a tumor vascular-targeting agent.

Tumour radiosensitization by high-oxygen-content gases: influence of the carbon dioxide content of the inspired gas on PO2, microcirculatory function and radiosensitivity

PURPOSE

To measure the effects of breathing high-oxygen-content gases, with a CO2 fraction of between 0 and 10%, on tumour radiosensitivity, blood flow and oxygenation.

METHODS AND MATERIALS

The murine sarcoma F was used, implanted subcutaneously (s.c.) in syngeneic CBA mice. We assessed the induced changes in tumour microregional blood flow and oxygenation using laser Doppler flowmetry, and pO2 histography, respectively. Radiation response was determined using an in vivo-in vitro clonogenic assay 18-20 h post treatment.

RESULTS

The results show that the level of radiosensitization achieved is dependent on both the CO2 content of the inspired gas and the duration of gas breathing. No radiosensitization was evident following inhalation of 90% O2 + 10% CO2. All other gases elicited radiosensitization; however, that achieved with 100% O2 disappeared at the extended preirradiation breathing time of 45 min. At this time, radiosensitization was maintained for gases containing 1%, 2.5%, or 5% CO2. Changes in oxygenation, as measured by PO2 electrodes, did indicate improved oxygenation status during inhalation of the gases. However, the time-course and extent of the changes did not mirror accurately the changes in radiosensitization. All the gases with a CO2 content of 2.5% or greater induced a 10-20% reduction in microregional blood flow, with no change evident following inhalation of 100% O2 or 99% O2 + 1% CO2.

CONCLUSIONS

The data imply that the decreased radiosensitization seen at extended breathing times of oxygen is unrelated to blood flow changes. The fact that radiosensitization is seen with extended breathing times of gases containing 2.5% and 5% CO2, despite blood flow decreases, is indicative of other overriding physiological changes, perhaps related to oxygen utilisation. The studies overall indicate that, at least in the tumour investigated, radiosensitization is not affected if the CO2 content of the inspired gas is reduced from 5% to 2.5%, or even 1%. Further evaluation of the radiosensitizing effects of such gas mixtures is now warranted. In addition, comparison with recent studies of other tumour types, where carbogen has been shown to improve tumour blood flow, suggests that this may be a tumour-specific phenomenon. Based on these data, further effort is required to elucidate the physiological mechanisms that determine these blood flow changes.

Post-traumatic AV fistulas and pseudoaneurysms

METHODS

The authors present the surgical treatment of 20 post-traumatic arteriovenous fistulas and 33 arterial pseudoaneurysms that have been treated in the last 5 years in the Centre for Vascular Surgery of the Institute for Cardiovascular Diseases, Clinical Centre of Serbia in Belgrade. Five women and 45 men (mean age 31.7 years) were examined. There were 28 war and 22 non-combatant injuries. In most cases superficial femoral artery and vein were involved. The average time elapsed from the moment of injury until the operation started, was 9 months in patients with AV fistulas, and one month for patients with pseudoaneurysms.

RESULTS

In all of the patients with AV fistulas, arterial and venous reconstructions were performed, except in 4 cases where the veins were ligated. Surgical reconstruction was performed in 26 patients with pseudoaneurysms, while in 7 cases the artery was ligated. There were no cases of postoperative ischemia in patients due to arterial ligation. Patients were followed for 2 years and 2 months postoperatively. As far as the reconstructive operations are concerned, the postoperative patency rate was 100%, while limb salvage was achieved in 96.9%. Namely, one amputation was done in spite of high arterial patency rate, which was indicated by massive bone-muscle tissue loss, occurring during mine explosive injury.

CONCLUSIONS

Because of the rapid disease progress, the authors suggest that the operative treatment of post-traumatic AV fistulas and pseudoaneurysms should be performed as soon as possible. This was supported by good follow-up results in operatively treated patients.

A charged-particle microbeam: I. Development of an experimental system for targeting cells individually with counted particles

Charged-particle microbeams provide a unique opportunity to control precisely, the dose to individual cells and the localization of dose within the cell. The Gray Laboratory is now routinely operating a charged-particle microbeam capable of delivering targeted and counted particles to individual cells, at a dose-rate sufficient to permit a number of single-cell assays of radiation damage to be implemented. By this means, it is possible to study a number of important radiobiological processes in ways that cannot be achieved using conventional methods. This report describes the rationale, development and current capabilities of the Gray Laboratory microbeam.

A charged-particle microbeam: II. A single-particle micro-collimation and detection system

The use of a charged-particle microbeam provides a unique opportunity to control precisely, the number of particles traversing individual cells and the localization of dose within the cell. The accuracy of 'aiming' and of delivering a precise number of particles crucially depends on the design and implementation of the collimation and detection system. This report describes the methods available for collimating and detecting energetic particles in the context of a radiobiological microbeam. The arrangement developed at the Gray Laboratory uses either a 'V'-groove or a thick-walled glass capillary to achieve 2-5 microns spatial resolution. The particle detection system uses an 18 microns thick transmission scintillator and photomultiplier tube to detect particles with > 99% efficiency.

Measurement of tumor oxygenation: a comparison between polarographic needle electrodes and a time-resolved luminescence-based optical sensor

A novel oxygen sensor which does not rely on electrochemical reduction has been used to measure the oxygenation of the murine sarcoma F in a comparative study with an existing polarographic electrode that is available commercially. The prototype luminescence sensor yielded an oxygen distribution comparable with readings made using a pO2 histograph. The percentage of regions detected that had a pO2 less than 5 mm Hg was 79 and 75 using the Eppendorf pO2 histograph and the luminescence fiber optic sensor, respectively. These values were compatible with a measured radiobiologically hypoxic fraction of 67% in this tumor. The polarographic method detected more regions with a pO2 of 2.5 mm Hg or less (69%) compared with the optical sensor (50%) (P < 0.05). This could reflect differences in the oxygen use of the sensing devices. This initial assessment indicates the potential of a fiber-optic-based oxygen-monitoring system. Such a system should have several advantages including monitoring temporal oxygen changes in a given microregion and use with NMR procedures.

Measurement of oxygen tension in tumours by time-resolved fluorescence

Tumour oxygenation is important in clinical radiotherapy because hypoxic cells are radioresistant. Knowledge of the state of tumour oxygenation would be advantageous for maximising effectiveness of treatment. A prototype fibre optic fluorosensor for measuring low (radiobiologically relevant) levels of oxygen is described. Based on oxygen quenching of the fluorescence of an excited fluorophor immobilised in a polymer at the end of an optical fibre, the sensor shows promise in overcoming some of the limitations of existing oxygen sensor systems. The prototype fibre optic sensor operates most effectively in the 0-2% oxygen range with fast response and settling times. Preliminary results from measurements in tumours are presented.

Inactivation of V79 cells by low-energy protons, deuterons and helium-3 ions

Previous work by ourselves and by others has demonstrated that protons with a linear energy transfer (LET) about 30 keVmum(-1)are more effective at killing cells than doubly charged particles of the same LET. In this work we show that by using deuterons, which have about twice the range of protons with the same LET, it is possible to extend measurements of the RBE of singly charged particles to higher LET (up to 50 keVmum(-1). We report the design and use of a new arrangement for irradiating V79 mammalian cells. Cell survival measurements have been made using protons in the energy range 1.0-3.7 MeV, deuterons in the energy range 0.9-3.4MeV and 3He2+ ions in the energy range 3.4-6.9 MeV. This corresponds to volume-averaged LET (within the cell nucleus) between 10 and 28 keVmum(-1) for protons, 18-50 keVmum(-1) for deuterons, and 59-106 keVmum(-1) for helium ions. Our results show no difference in the effectiveness of protons and deuterons matched for LET. However, for LET above about 30 keVmum(-1) singly charged particles are more effective at inactivating cells than doubly-charged particles of the same LET and that this difference can be understood in terms of the radial dose distribution around the primary ion track.

Radiosensitisation in normal tissues with oxygen, carbogen or nicotinamide: therapeutic gain comparisons for fractionated x-ray schedules

METHODS

Radiosensitisation with oxygen, carbogen or nicotinamide alone and oxygen or carbogen combined with nicotinamide was compared in early and late responding normal tissues in rodents. X-ray treatments were delivered as single doses or fractionated schedules of 2 fractions in 1 day, 2, 12 and 36 fractions in an overall time of 12 days and 10 fractions in 5 or 12 days. Acute skin reactions, survival of intestinal crypts, breathing rate, reduction in the packed red-cell volume and clearance of 51Cr-EDTA were used as assays of epidermal, gut, lung and renal damage.

RESULTS

Relative to air-breathing mice, carbogen or oxygen produced a small, and not always significant, increase in sensitivity (enhancement ratios < or = 1.15) in gut, lung and kidneys; however, in skin a dose enhancement of 1.2-1.3 was observed. The effect of nicotinamide in air, carbogen or oxygen was studied only in lung and gut. The drug produced variable but generally significant increases in radiosensitisation ( < or = 1.26) in all three gases. Relative to treatments in air, enhancement ratios for nicotinamide alone were usually slightly higher than those observed when either carbogen or oxygen were administered without the drug. With all three modifiers (i.e. oxygen, carbogen, nicotinamide alone or for the drug-gas combinations) there was no significant change in the enhancement ratios observed as the number of radiation dose fractions was varied.

CONCLUSIONS

Comparisons with fractionated X-ray studies done previously in rodent tumours indicate that a therapeutic benefit, relative to lung, gut and renal damage, would be observed with oxygen or carbogen alone but not with nicotinamide alone. The greatest gain would be achieved with the combination of carbogen and nicotinamide, with which a benefit was observed even relative to epidermal damage. These results indicate that some decrease in normal tissue tolerance could be observed when using these modifiers in clinical radiotherapy and, although small, the appropriate dose reductions should be considered; caution should be exercised especially when carbogen and nicotinamide are used in conjunction with the more radical accelerated schedules.