Assessment of the WAP-Myc mouse mammary tumor model for spontaneous metastasis.

Breast cancer is the most common form of cancer in women. Despite significant therapeutic advances in recent years, breast cancer also still causes the greatest number of cancer-related deaths in women, the vast majority of which (> 90%) are caused by metastases. However, very few mouse mammary cancer models exist that faithfully recapitulate the multistep metastatic process in human patients. Here we assessed the suitability of a syngrafting protocol for a Myc-driven mammary tumor model (WAP-Myc) to study autochthonous metastasis. A moderate but robust spontaneous lung metastasis rate of around 25% was attained. In addition, increased T cell infiltration was observed in metastatic tumors compared to donor and syngrafted primary tumors. Thus, the WAP-Myc syngrafting protocol is a suitable tool to study the mechanisms of metastasis in MYC-driven breast cancer.

Self-Delivery Nanomedicine for O2-Economized Photodynamic Tumor Therapy.

Tumor hypoxia is the Achilles heel of oxygen-dependent photodynamic therapy (PDT), and tremendous challenges are confronted to reverse the tumor hypoxia. In this work, an oxidative phosphorylation inhibitor of atovaquone (ATO) and a photosensitizer of chlorine e6 (Ce6)-based self-delivery nanomedicine (designated as ACSN) were prepared via π-π stacking and hydrophobic interaction for O2-economized PDT against hypoxic tumors. Specifically, carrier-free ACSN exhibited an extremely high drug loading rate and avoided the excipient-induced systemic toxicity. Moreover, ACSN not only dramatically improved the solubility and stability of ATO and Ce6 but also enhanced the cellular internalization and intratumoral permeability. Abundant investigations confirmed that ACSN effectively suppressed the oxygen consumption to reverse the tumor hypoxia by inhibiting mitochondrial respiration. Benefiting from the synergistic mechanism, an enhanced PDT effect of ACSN was observed on the inhibition of tumor growth. This self-delivery system for oxygen-economized PDT might be a potential appealing clinical strategy for tumor eradication.

Assessment of novel core-shell Fe3O4@poly l­DOPA nanoparticles for targeted Taxol® delivery to breast tumor in a mouse model.

Drug delivery systems using nanoparticles can deliver to tumor cells without affecting normal cells. In this study, a novel well dispersed magnetic nano drug was synthesized. Thus, a selective drug delivery system was designed for potential cancer treatment. A new nanocomposite, poly 3,4­dihydroxy­l­phenylalanine/Fe3O4 (l­DOPA/Fe3O4), was synthesized and used for targeted Taxol® delivery to breast tumor in inbreed Balb/c mice model with or without magnetic field. Fe and Taxol® concentrations were measured by flame atomic absorption spectrometry and high-performance liquid chromatography, respectively. Antitumor effectiveness was investigated in terms of tumor growth features. In the presence of magnetic field, Taxol® was significantly deposited in tumor tissue in Taxol-nanocomposite-treated group. In addition, the Taxol®-nanocomposite-treated group with magnetic field showed higher antitumor efficacy than the commercial Taxol and Taxol-nanocomposite without magnetic field. The magnetic nanocomposite is promising for targeted Taxol® delivery to breast tumor in a mouse model yielding high performance.

In Vivo EPR Assessment of pH, pO2, Redox Status, and Concentrations of Phosphate and Glutathione in the Tumor Microenvironment.

This protocol demonstrates the capability of low-field electron paramagnetic resonance (EPR)-based techniques in combination with functional paramagnetic probes to provide quantitative information on the chemical tumor microenvironment (TME), including pO2, pH, redox status, concentrations of interstitial inorganic phosphate (Pi), and intracellular glutathione (GSH). In particular, an application of a recently developed soluble multifunctional trityl probe provides unsurpassed opportunity for in vivo concurrent measurements of pH, pO2 and Pi in Extracellular space (HOPE probe). The measurements of three parameters using a single probe allow for their correlation analyses independent of probe distribution and time of the measurements.

Early assessment of tumor response to photodynamic therapy using combined diffuse optical and diffuse correlation spectroscopy to predict treatment outcome.

Photodynamic therapy (PDT) of cancer involves the use of a photosensitizer that can be light-activated to eradicate tumors via direct cytotoxicity, damage to tumor vasculature and stimulating the body's immune system. Treatment outcome may vary between individuals even under the same regime; therefore a non-invasive tumor response monitoring system will be useful for personalization of the treatment protocol. We present the combined use of diffuse optical spectroscopy (DOS) and diffuse correlation spectroscopy (DCS) to provide early assessment of tumor response. The relative tissue oxygen saturation (rStO2) and relative blood flow (rBF) in tumors were measured using DOS and DCS respectively before and after PDT with reference to baseline values in a mouse model. In complete responders, PDT-induced decreases in both rStO2 and rBF levels were observed at 3 h post-PDT and the rBF remained low until 48 h post-PDT. Recovery of these parameters to baseline values was observed around 2 weeks after PDT. In partial responders, the rStO2 and rBF levels also decreased at 3 h post PDT, however the rBF values returned toward baseline values earlier at 24 h post-PDT. In contrast, the rStO2 and rBF readings in control tumors showed fluctuations above the baseline values within the first 48 h. Therefore tumor response can be predicted at 3 to 48 h post-PDT. Recovery or sustained decreases in the rBF at 48 h post-PDT corresponded to long-term tumor control. Diffuse optical measurements can thus facilitate early assessment of tumor response. This approach can enable physicians to personalize PDT treatment regimens for best outcomes.

Dual in vivo photoacoustic and fluorescence imaging of HER2 expression in breast tumors for diagnosis, margin assessment, and surgical guidance.

Biomarker-specific imaging probes offer ways to improve molecular diagnosis, intraoperative margin assessment, and tumor resection. Fluorescence and photoacoustic imaging probes are of particular interest for clinical applications because the combination enables deeper tissue penetration for tumor detection while maintaining imaging sensitivity compared to a single optical imaging modality. Here we describe the development of a human epidermal growth factor receptor 2 (HER2)-targeting imaging probe to visualize differential levels of HER2 expression in a breast cancer model. Specifically, we labeled trastuzumab with Black Hole Quencher 3 (BHQ3) and fluorescein for photoacoustic and fluorescence imaging of HER2 overexpression, respectively. The dual-labeled trastuzumab was tested for its ability to detect HER2 overexpression in vitro and in vivo. We demonstrated an over twofold increase in the signal intensity for HER2-overexpressing tumors in vivo, compared to low-HER2-expressing tumors, using photoacoustic imaging. Furthermore, we demonstrated the feasibility of detecting tumors and positive surgical margins by fluorescence imaging. These results suggest that multimodal HER2-specific imaging of breast cancer using the BHQ3-fluorescein trastuzumab enables molecular-level detection and surgical margin assessment of breast tumors in vivo. This technique may have future clinical impact for primary lesion detection, as well as intraoperative molecular-level surgical guidance in breast cancer.

Tamoxifen-loaded nanostructured lipid carrier as a drug delivery system: characterization, stability assessment and cytotoxicity.

Cancer nanotherapeutics is beginning to overwhelm the global research and viewed to be the revolutionary treatment regime in the medical field. This investigation describes the development of a stable nanostructured lipid carrier (NLC) system as carrier for Tamoxifen (TAM). The TAM-loaded NLC (TAM-NLC) developed with 200mg of TAM showed a spherical particle with the size of 46.6nm, polydispersity index of 0.267, entrapment efficiency of 99.74% and with the zeta potential of -23.78mV. Besides, the equivalent cytotoxicity of TAM and TAM-NLC to human (MCF-7) and mice (4T1) mammary breast cancer cell lines were observed. Incubating the formulation at the physiological pH resulted into reduced Ostwald ripening rate but without any significant change in the absorptivity. When coupled with the measurements of zeta potential and Ostwald ripening rate, the absorbance assay may be used to predict the long-term stability of drug-loaded nanoparticle formulations. The results of the study also suggest that TAM-NLC is a promising drug delivery system for breast cancer therapy. This is the first encouraging report on the in vitro effect of TAM-NLC against human and mouse mammary adenocarcinoma cell lines.

Tumor angiogenic marker expression levels during tumor growth: longitudinal assessment with molecularly targeted microbubbles and US imaging.

PURPOSE: To evaluate the use of molecularly targeted microbubbles (MBs) and ultrasonography (US) in the noninvasive assessment of the level of expression of three angiogenic markers, α(v)ß(3) integrin, endoglin, and vascular endothelial growth factor receptor (VEGFR) 2, on tumor vascular endothelial cells in vivo during tumor growth. MATERIALS AND METHODS: All procedures using laboratory animals were approved by the Institutional Administrative Panel on Laboratory Animal Care. Binding specificity of three types of targeted MBs (MB(Integrin), MB(Endoglin), MB(VEGFR2)) was tested in cell culture under flow shear stress conditions. In vivo targeted contrast material-enhanced US imaging signal using the three MB types was measured at three tumor stages (small, medium, large) in three subcutaneous cancer xenografts (breast, ovarian, pancreatic cancer) in mice (n = 54). In vivo US imaging signal was correlated with ex vivo angiogenic marker expression. Significant differences were evaluated by using the Student t, analysis of variance, Wilcoxon, and Tukey Honest Significant Difference tests. RESULTS: Cell attachment of all three MB types was significantly (P = .016) higher compared with control MBs, and this attachment could be significantly (P = .026) decreased by blocking antibodies. Angiogenic marker-expressing cells bound significantly (P = .003) more targeted MBs than negative control cells, and MB attachment significantly (P < .001) correlated with marker expression levels on cells (ρ = 0.87). In early stage breast and ovarian cancers, in vivo targeted contrast-enhanced US demonstrated significantly (P ≤ .04) higher endoglin expression than both α(v)ß(3) integrin and VEGFR2 expression, whereas in early stage pancreatic cancer, marker expressions were not significantly different (P ≥ .07). There was good correlation (ρ ≥ 0.63; P ≤ .05) between in vivo targeted contrast-enhanced US imaging signals using the three MB types and ex vivo immunoblotting results regarding expression levels of the three angiogenic markers. Immunofluorescence confirmed expression of α(v)ß(3) integrin, endoglin, and VEGFR2 on tumor vascular endothelial cells. CONCLUSION: Targeted contrast-enhanced US imaging allows noninvasive in vivo assessment of the expression levels of α(v)ß(3) integrin, endoglin, and VEGFR2, which vary during tumor growth in subcutaneous cancer xenografts.

Intrinsic susceptibility MR imaging of chemically induced rat mammary tumors: relationship to histologic assessment of hypoxia and fibrosis.

PURPOSE: To investigate relationships between magnetic resonance (MR) imaging measurements of R2* and carbogen-induced DeltaR2* in vivo with subsequent histologic assessment of grade, hypoxia, fibrosis, and necrosis in a chemically induced rat mammary tumor model. MATERIALS AND METHODS: All experiments were performed in accordance with the local ethics review panel, the UK Home Office Animals Scientific Procedures Act of 1986, and the UK Co-ordinating Committee on Cancer Research guidelines. Of 30 rats injected with N-methyl-N-nitrosourea, 17 developed mammary tumors. Prior to MR imaging, rats were administered pimonidazole. Tumor R2* was then quantified while the host first breathed air and then carbogen (95% O(2), 5% CO(2); n = 16). Tumor sections were subsequently stained for pimonidazole, sirius red, cytokeratin 14, and hematoxylin-eosin for quantitative assessment of hypoxia, fibrosis, malignancy, and necrosis, respectively, and graded according to the Scarff-Bloom-Richardson scale. Linear regression analysis was used to identify any correlates of the MR imaging data with histologic data. RESULTS: Tumors exhibited wide heterogeneity in the magnitude of carbogen-induced reduction in R2*, an emerging imaging biomarker of fractional blood volume. Significant correlations were found between pimonidazole adduct formation and both baseline tumor R2* (r = -0.54, P = .03) and carbogen-induced DeltaR2* (r = 0.56, P = .02), demonstrating that tumors with a larger fractional blood volume were less hypoxic. There was also a significant correlation between pimonidazole and sirius red staining (r = 0.76, P < .01), indicating that more fibrotic tumors were also more hypoxic. There were no correlations of R2* with grade. CONCLUSION: In this model of breast cancer, baseline tumor R2* and carbogen-induced DeltaR2* are predictive imaging biomarkers for hypoxia and primarily determined by blood volume.

Using optical spectroscopy to longitudinally monitor physiological changes within solid tumors.

The feasibility of using quantitative diffuse reflectance spectroscopy to longitudinally monitor physiological response to cancer therapy was evaluated in a preclinical model. This study included two groups of nude mice bearing 4T1 flank tumors (N = 50), half of which were treated with a maximum tolerated dose of doxorubicin (DOX). Diffuse reflectance spectra were collected from tumors during a period of 2 weeks using a fiber-optic probe coupled to a spectrometer. These spectra were quantified using an inverse scalable Monte Carlo model of light transport in tissue to extract the concentrations of oxygenated, deoxygenated hemoglobin (dHb), and a wavelength mean reduced scattering coefficient (). The tumor growth rates of the treated and control groups were nearly identical, as were changes in the scattering parameter during this time frame. However, tumors treated with DOX showed a transient but significant increase in blood oxygen saturation. A comparison between the optically derived and immunohistochemical end points in a subset of the 50 animals showed that the temporal kinetics of dHb concentration and were highly concordant with those of hypoxic and necrotic fractions, respectively. In conclusion, optical methods could function as a "screening" technology in longitudinal studies of small animal tumor models to accelerate development and testing of new anticancer drugs. This technique could isolate specific landmark time points at which more expensive and sophisticated imaging methods or immunohistochemistry could be performed.

Assessment of 11C-labeled-4-N-(3-bromoanilino)-6,7-dimethoxyquinazoline as a positron emission tomography agent to monitor epidermal growth factor receptor expression.

The aim of the present study was to investigate the biodistribution of (11)C-labeled-4-N-(3-bromoanilino), 6,7-dimethoxyquinazoline ((11)C-PD153035) and the relationship between accumulation of the tracer and epidermal growth factor receptor (EGFR) expression levels. Biodistribution studies of (11)C-PD153035 were performed in tumor-bearing nude mice. The amount of radioactivity in the lungs was small while concentrations were highest in the liver and intestine. From in vitro studies, the level of (11)C-PD153035 accumulation was detected in MDA-MB-468, A549, and MDA-MB-231 cells. The uptake of (11)C-PD153035 in cells was closely correlated with the EGFR expression level of cells (r(2) = 0.85; P < 0.001), and the results obtained in excised tumors were also significantly correlated (r(2) = 0.63; P = 0.003). Binding in MDA-MB-468, A549, and MDA-MB-231 tumors was reduced to background level at 60 min post injection( 11)C-PD153035 by pretreatment with cold PD153035. The present study showed that whether in vitro or ex vivo the uptake of (11)C-PD153035 closely correlated with EGFR expression levels. In contrast, blocking studies revealed specific binding in the three kinds of tumors. Thus (11)C-PD153035 may be used as a positron emission tomography tracer to yield useful information about tumors, particularly for lung cancer with different EGFR expression levels.

Recovery of hemoglobin oxygen saturation and intrinsic fluorescence with a forward-adjoint model.

We present two forward-adjoint models for recovering intrinsic fluorescence spectra and hemoglobin oxygen saturation of turbid samples. The first fits measured diffuse reflectance spectra to obtain the absorption and scattering spectra of the medium, and these are then used to correct distortions imposed on the fluorescence spectrum by absorption and scattering. The second fits only the measured fluorescence spectrum to determine simultaneously the amplitudes of absorption and fluorescence basis spectra and scattering parameters. Both methods are validated with Monte Carlo simulations and experimentally in scattering phantoms containing nicotinamide adenine dinucleotide and human erythrocytes. Preliminary measurements from murine tumors in vivo are presented.

Assessment of photosensitizer dosimetry and tissue damage assay for photodynamic therapy in advanced-stage tumors.

Photodynamic therapy (PDT) efficacy is a complex function of tissue sensitivity, photosensitizer (PS) uptake, tissue oxygen concentration, delivered light dose and some other parameters. To better understand the mechanisms and optimization of PDT treatment, we assessed two techniques for quantifying tissue PS concentration and two methods for quantifying pathological tumor damage. The two methods used to determine tissue PS concentration kinetic were in vivo fluorescence probe and ex vivo chemical extraction. Both methods show that the highest tumor to normal tissue PS uptake ratio appears 4 h after PS administration. Two different histopathologic techniques were used to quantify tumor and normal tissue damage. A planimetry assessment of regional tumor necrosis demonstrated a linear relationship with increasing light dose. However, in large murine tumors this finding was complicated by the presence of significant spontaneous necrosis. A second method (densitometry) assessed cell death by nuclear size and density. With some exceptions the densitometry method generally supported the planimetry results. Although the densitometry method is potentially more accurate, it has greater potential subjectivity. Finally, our research suggests that the tools or methods we are studying for quantifying PS levels and tissue damage are necessary for the understanding of PDT effect and therapeutic ratio in experimental in vivo tumor research.

Assessment of hypoxia in experimental mice tumours by [18F]fluoromisonidazole PET and pO2 electrode measurements. Influence of tumour volume and carbogen breathing.

The aim of this study was to compare a non-invasive 18F-fluoromisonidazole ([18F]FMISO) PET assessment of tumour hypoxia with invasive Eppendorf pO2 measurements in 150-1,500 mm3 C3H mammary carcinomas transplanted on the back of CDF1 mice. The tumour-bearing mice breathed either carbogen gas (95% oxygen, 5% CO2) or normal air during both examinations. Additional autoradiography was performed in separate tumours treated similarly. The PET [18F]FMISO examination significantly discriminated between tumours of carbogen and air-breathing mice. For the pO2 measurements, there was a significantly lower percentage of measurements below 2.5 mmHg for carbogen-treated mice compared with air-breathing mice. However, no direct correlation between the methods was seen. A correlation was found between tumour volume and Eppendorf estimates of tumour hypoxia for the animals breathing normal air, but no correlation was found between the PET endpoint and tumour volume. This may be due to low pO2 measurements obtained in necrotic tissue. Autoradiography confirmed lower [18F]FMISO uptake in tumours of carbogen-breathing animals compared with air-breathing animals, and demonstrated the heterogeneity of the tracer uptake in small compared with larger tumours.

Urea as a recovery marker for quantitative assessment of tumor interstitial solutes with microdialysis.

Microdialysis is a technique that enables measurement of extracellular concentrations of unbound analytes. A small probe with a semipermeable membrane is implanted in tissue and constantly perfused. Small analytes in the interstitial fluid diffuse into the perfusate and are collected. Often, microdialysate concentrations of an analyte are only a fraction of the unbound concentrations in the extracellular space attributable to incomplete equilibration between these two compartments. Thus, it is necessary to determine the degree of equilibration between microdialysate and interstitium for each probe to accurately estimate concentrations. In this study, we investigated tissue urea as a solute to continually correct for nonequilibrium conditions. We used this method, along with relative diffusivities of urea and glucose, to monitor glucose levels before and during hyperglycemia as an example of how this method can be applied. No-net-flux experiments were performed on 10 anesthetized female rats with mammary adenocarcinomas. Microdialysis probes 1 cm in length with a molecular weight cutoff of M(r) 100,000 were used. Urea was added to the perfusate in concentrations of 0.83, 2.5, 5.0, and 13.33 mM. Microdialysate samples were collected every 15 min. For each rat, there was a linear relationship between the net urea concentration (outflow-inflow) and the urea concentration in the perfusate (inflow). Net flux should equal zero when perfusate and interstitial concentrations are equal. In an additional series of 13 rats, microdialysate samples were obtained before, during, and after administration of glucose at a dose of 1 g/kg. The interstitial tumor urea concentration was 7.8 +/- 0.3 mM compared with 6.2+/- 0.3 mM in plasma. There was a significant linear relationship between plasma urea (measured directly) and tumor urea (microdialysis measurement). Plasma urea concentrations were constant over time in all of the experiments, including those where hyperglycemia was induced. Hyperglycemia caused 7.7- and 3.6-fold increases in tumor and plasma glucose, respectively. There was no effect of hyperglycemia on tumor blood flow. Urea appears to be a useful low molecular weight relative recovery marker for tumor microdialysis. In combination with the determination of relative diffusivity between urea and the solute of interest, this calibration method may allow for quantitative measurements of tumor metabolites and unbound drugs.

Assessment of induced rat mammary tumour response to chemotherapy using the apparent diffusion coefficient of tissue water as determined by diffusion-weighted 1H-NMR spectroscopy in vivo.

Chemosensitivity of N-methyl-N-nitrosourea-induced rat mammary tumours treated with 5-fluorouracil at a dose of 100 mg kg(-1) i.p. was assessed by using diffusion-weighted 1H-MRS to measure the average diffusion coefficient (ADC) of water in the tumour tissue. ADC measurements prior to any therapy correlated positively with necrotic fraction. Tumours with low initial ADC (< 0.95 x 10(9) m2 s(-1)) showed an increase in ADC 7 days after treatment, whereas tumours with a high initial ADC (> 1.2 x 10(9) m2 s(-1)) showed a decrease. All tumours decreased significantly in volume (P < 0.05) 2, 5 and 7 days after treatment. At day 7 post-treatment, tumours with a high pre-treatment ADC started to regrow. The initial ADC value, as well as changes after treatment predict tumour chemosensitivity, which could be clinically relevant.

Noninvasive assessment of tumor hypoxia with 99mTc labeled metronidazole.

PURPOSE: The assessment of tumor hypoxia by imaging modality prior to radiation therapy would provide a rational means of selecting patients for treatment with radiosensitizers or bioreductive drugs. This study aimed to develop a 99mTc-labeled metronidazole (MN) using ethylene-dicysteine (EC) as a chelator and evaluate its potential use to image tumor hypoxia. METHODS: EC was conjugated to amino analogue of MN using Sulfo-N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-HCl as coupling agents, the yield was 55%. Tissue distribution of 99mTc-EC-MN was determined in breast tumor-bearing rats at 0.5, 2, and 4 hrs. Planar imaging and whole-body autoradiograms were performed. The data was compared to that using 99mTc-EC (control), [18F]fluoromisonidazole (FMISO) and [(131)I] iodomisonidazole (IMISO). RESULTS: In vivo biodistribution of 9mTc-EC-MN in breast tumor-bearing rats showed increased tumor-to-blood and tumor-to-muscle ratios as a function of time. Conversely, tumor-to-blood values showed time-dependent decrease with 9mTc-EC in the same time period. Planar images and autoradiograms confirmed that the tumors could be visualized clearly with 99mTc-EC-MN from 0.5 to 4 hrs. There was no significant difference of tumor-to-blood count ratios between 99mTc-EC-MN and [(131)I]IMISO at 2 and 4 hrs postinjection. From 0.5 to 4 hrs, both 9mTc-EC-MN and [(131)I]MISO have higher tumor-to-muscle ratios compared to [18]FMISO. CONCLUSIONS: It is feasible to use 9mTc-EC-MN to image tumor hypoxia.

An assessment of artefacts in localized and non-localized 31P MRS studies of phosphate metabolites and pH in rat tumours.

UA hepatomas, GH3 prolactinomas and N-methyl-N-nitrosourea-induced mammary tumours, which were subcutaneously grown in rats, have been studied by 31P MRS using non-localized pulse-acquire, image selected in vivo spectroscopy (ISIS) and one-dimensional chemical shift imaging (1-D CSI) techniques. Comparisons have been made with measurements from acid extracts of these tumour types and surrounding tissues (i.e., muscle and skin). Since muscle containing high concentrations of phosphocreatine (PCr) is often found adjacent to the tumour, we have compared the ratio of the PCr to gamma-NTP peaks in the spectra with the same ratio calculated from the acid extract data, and have used deviations between the two sets of data to assess the discrimination of the MRS localization technique to signals from the tissue surrounding the tumour. Extract data showed an average NTP content of 1.25 mumol/g wet wt for all three tumour types. PCr (at 0.42 mumol/g wet wt), was significant only in the GH3 prolactinoma whereas it was negligible in the other tumour types (< 0.1 mumol/g wet wt). There was good agreement between the ISIS PCr/gamma-NTP ratio and the extract data for all tumours. However, the 1-D CSI data showed an unexpectedly large contamination of the tumour spectrum with PCr signals from the skin which was shown by subsequent phantom experiments to be due to the curved geometry of tumour and skin rather than Fourier bleed. In pH measurements by MRS it was found that biological variability was greater than the effects of artefacts (due to either the chemical shift artefact in the ISIS technique or partial volume effects) in the localization technique. An average pH of 7.2 was observed for all tumours. By initially comparing data from different localization schemes with that from chemical extracts potential sources of error have been highlighted and show that phantom studies alone are not sufficient to fully assess the accuracy of localized MRS data.

An assessment of 31P MRS as a method of measuring pH in rat tumours.

The contribution of extracellular components to the measurement of pHMRS of a variety of rat tumours (nitrosomethyl urea induced mammary tumours, GH3 prolactinomas, Hepatoma 9618a, UA hepatomas and Walker sarcomas) has been assessed. Acid extractable P(i) was between 2.6 and 12.5 mumol/G wet wt depending on tumour type, and of this 53 +/- 4.8% (mean +/- SEM) was MRS-visible. The P(i) content of tumour exudate was 2-3 mM, of interstitial fluid (sampled from a micropore chamber incorporated within a tumour) 1.7 mM, and of blood plasma 1.95 mM. The mean extracellular volumes of the tumours, measured by distribution of 3H2O and [14C]inulin, were 49-55% depending on tumour type and were at least twice that found in normal liver. Calculations suggested that for most tumours with an extracellular volume not exceeding 55%, at least 65% of the P(i)(MRS) signal was derived from intracellular P(i), and thus that pH(MRS) is a measure of pHi. For each tumour type, pHMRS was measured both in 'pulse-acquire' mode at 1.9 T which may include signals from surrounding tissue, and in localized mode at 4.7 T where the signal came uniquely from tumour tissue. The steady state pHMRS was either neutral or on the alkaline side of neutrality (pH range 7.04-7.37). Raised lactate content and decreased buffering capacity (compared to normal tissues) accompanied these neutral to alkaline pH values.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo assessment of 111In-labeled hematoporphyrin derivative in breast tumor-bearing animals.

The biological behavior of 111In-labeled HPD has been investigated in tumor-bearing animals. Mice mammary adenocarcinomas and 7,12-dimethylbenz(a)anthracine induced breast tumors in Sprague-Dawley female rats were clearly visualized by 111In-HPD nuclear scintigraphy. Optimal scans were obtained after a 48 h delay. In normal and tumor-bearing animals, the highest uptake of 111In-HPD 72 h post-injection was found in the liver, the spleen and the kidneys. Depending on the size and the extent of necrosis, the uptake of 111In-HPD by malignant breast tumors varied from 2.5% injected dose (ID) (range 0.14-5.3% ID) in mice to 1% (range 0.22-8.1% ID) in rats. Benign breast tumor uptake of 111In-HPD was less than 1% ID. No significant amount of the radiopharmaceutical was found in pulmonary abscesses and abdominal cysts (less than 0.1% ID). Scintigrams of these infectious or inflammatory lesions were normal. Malignant tumor to blood, heart and lung ratios averaged 50:1, 10:1 and 3:1 respectively. Tumor to brain ratio ranged from 72 to 444:1.