Small molecule nerve growth factor analogs image receptors in vivo

The in vivo targeting efficacy of small molecule analogs of nerve growth factor (NGF) that bind the NGF receptor p140 TrkA was evaluated and compared with that of a high-affinity anti-TrkA monoclonal antibody (Mab 5C3). Nuclear imaging studies were done after the injection of 99mTc-labeled compounds in nude mice bearing tumors. Kinetics of tumor targetting, blood clearance, and bioavailability of NGF mimics were equivalent or better than Mab 5C3. Tumors that do not express TrkA were not targeted, demonstrating the specificity of NGF mimics in vivo. This comparative biodistribution study demonstrates that receptor-specific small molecule analogs designed from large polypeptides may be more useful than antibodies and may be effective agents for the detection, diagnosis, and possible treatment of neoplasias involving overexpressed oncogenic receptors such as TrkA.

1995 Whitaker Lecture: delivery of molecules, particles, and cells to solid tumors

To reach cancer cells in a tumor, a blood-borne therapeutic agent must make its way into the blood vessels of the tumor and across the vessel wall into the interstitium, and finally migrate through the interstitium. Unfortunately, tumors often develop in ways that hinder each of these steps. Our research goals are to analyze each of these steps experimentally and theoretically, and then to integrate the resulting information in a unified theoretical framework. This paradigm of analysis and synthesis has allowed us to obtain a better understanding of physiological barriers in solid tumors, and to develop novel strategies to exploit and/or to overcome these barriers for improved cancer detection and treatment.

Targeting of glucose transport proteins for tumor imaging: is it feasible?

If glucose transport proteins (Glut) are elevated in tumors they may be good targets for tumor imaging. For targeting, the overexpression of Glut should be a general characteristic of tumors. Moreover agents which bind to Glut should accumulate selectively in tumors.

METHODS

To test this, we quantitated Glut in isolated membranes from three human tumor xenografts, two murine tumor models and normal murine tissues using direct binding studies. Additionally, the biodistribution of two compounds which bind to Glut, 7-[[(2-(3-(125I-p-hydroxyphenyl)propionyl)aminoethyl)amino]carbonyl]-7-+ ++desacetyl-forskolin([125I]HPP forskolin) and [3H]cytochalasin B, were studied in a tumor model which overexpressed Glut.

RESULTS

There were multiple classes of binding sites for [3H]cytochalasin B and a percentage of these sites were competitive with D-glucose but not L-glucose. The rank potency and IC50 values for [3H]cytochalasin B binding were: 2-deoxy-D-glucose (4.5 mM) > or = D-glucose (7 mM) > mannose (25 mM) > galactose (35 mM) > rhamnose (1-3 mM) > sorbitol (1-3 mM) and were similar to reported values for transport. The average density of Glut in four tumor models and normal tissues was between 0.7 and 4 pmole/mg protein, but Kd values were not significantly different (69 nM). In LX-1 human lung tumor xenograft (LX-1) Glut were 10-to-20-fold higher than other tissues (21.6 +/- 0.6 pmole/mg protein, p<0.01). Immunostaining of Glut-1 was more prominent in LX-1 than other xenograft tumors, consistent with the binding data. Glut density was highest in poorly vascularized regions suggesting that Glut upregulation was related to a biofeedback mediated event. Iodine-125 HPP-forskolin and [3H]cytochalasin B did not localize in LX-1 tumors.

CONCLUSION

Glut overexpression was not a common characteristic of the five tumors tested. Iodine-125 HPP-forskolin and [3H]cytochalasin B did not localize in LX-1 tumors, indicating that these agents did not target tumors with upregulated Glut. Results suggest that Glut are not a promising target for tumor imaging.

In vivo evaluation of magnetite nanoparticles for use as a tumor contrast agent in MRI

Magnetite nanoparticles, coated by three different artificial polypeptides, were conjugated to an antibody specific to the carcinoembryonic antigen (CEA). To protect the particles from fast blood elimination, the coats were modified by various sugars, polyethyleneglycol, albumin, and sialoproteins, respectively. The protective effect was determined by using a specific in vitro test and by analyzing the biodistribution of the nanoparticles in nude mice grafted with CEA-tumors. In particular, a prolongation of the blood circulation time has been expected, if a natural modifier is attached to the coated nanoparticles. Although the elimination rate could hardly be decreased by any modifiers, the tumor accumulation is slightly improved by using the specific sialoprotein glycophorin B. The usefulness of nanoparticles as image contrast agents is probably limited by their microdistribution within the tumor tissue. The requirements for a contrast agent to be highly tissue specific are discussed.

Determination of erythrocyte polyamines as a predictive method in tumour diagnosis. An animal study with chemically induced tumours

There have been numerous attempts in the past to use polyamine determinations in body fluids for tumour diagnosis. Since spermidine (Spd) and spermine (Spm) are mainly transported in blood by erythrocytes, this study was concerned with the diagnostic possibilities of red blood cell (RBC) polyamine determinations. In tumour-grafted animals we observed that RBC polyamine levels correlated with the tumour mass progression and increased before the tumour was palpable. Discrepancies between the evolution of RBC polyamine levels in tumour-grafted animals and in cancer patients were probably due to the non-continuous growth of the tumours in patients. Therefore, an animal model was sought which mimicked the clinical situation. In the present experiments, ethylnitrosourea induced tumours were used which, in analogy to the clinical situation, had an undetermined time of the appearance in a non-predetermined proportion of the animals. RBC polyamines were determined over a period of 7 months in 154 rats. A total of 2,290 RBC polyamine determinations were performed during this study. The data clearly demonstrate the appearance of elevated Spd concentrations in advance of tumour diagnosis by conventional clinical methods. In 71% of the rats which later developed a tumour, abnormal Spd levels (> 40 nmol/8.109 RBC) preceded, by 35 +/- 31 days, the first clinical symptoms for the presence of a tumour. In 29% of the animals, abnormal RBC Spd concentrations were observed at the time of tumour diagnosis. Elevation of Spm concentrations (> 6 nmol/8.10(9) RBC) was less frequent. RBC polyamine levels did not allow discrimination between malignant and non malignant tumours. This confirms earlier findings that RBC polyamines are markers of the cell proliferation rate, but not for the presence of a malignant tumour. Elevated RBC polyamine concentrations are an index of the intensity of hyperplastic processes, which can be clinically used for the early detection of proliferative phases of tumours, thus allowing timely therapeutic measures.

Tumor labeling in vivo using cyanine-conjugated monoclonal antibodies

Far-red-emitting cyanine fluorochromes have many properties desirable for in vivo imaging: absorption and emission at wavelengths where blood and tissue are relatively transparent, high quantum yields, and good solubility even at high molar ratios of fluorochrome to antibody. Potentially, conjugation by multiple linkages should minimize hydrolysis in vivo. We conjugated two tumor-targeting monoclonal antibodies: anti-SSEA-1 (IgM, kappa) at ratios of 1.2-35 mol dye/mol antibody and 9.2.27 (IgG2a, kappa) at 0.6-6 mol dye/mol antibody, using the cyanine fluorochromes Cy3.18, Cy5.18, and Cy5.5.18. Nude mice were inoculated using the SSEA-1-expressing MH-15 teratocarcinoma or the 9.2.27 antigen-expressing SK-MEL-2 melanoma to give tumors at several sites. Conjugated antibody was injected, and mice were imaged immediately after injection and at appropriate intervals thereafter using a standard camera lens, dissecting microscope, or endoscopes. Images were acquired using either an image-intensified video camera or cooled CCD cameras. Immediately after injection, major blood vessels and the heart, liver, and kidneys were readily visualized. After 1 day, tumor-targeting antibody conjugates were concentrated in tumors and there was little circulating conjugate; however, the bladder and kidneys were still visible. Tumors labeled by specific antibody were the most fluorescent tissues at 2 days after injection, but non-specific antibody conjugates did not concentrate in the tumors. The small intestine was weakly visualized by both specific and non-specific antibody conjugates. These data support the possibility of visualizing tumor metastasis by optical means, including currently available endoscopes.

delta-Aminolevulinic acid induced fluorescence in tumour-bearing mice

The potential of protoporphyrin IX fluorescence induced by the systemic administration of delta-aminolevulinic acid (ALA) for the detection of tumours was tested in three different murine models (MS-2 fibrosarcoma, L1210 leukaemia, and Lewis lung carcinoma). Time-gated fluorescence images were acquired up to 4 h after the intraperitoneal injection of ALA (200 mg (kg body mass (BM))-1). For comparison images were acquired also after the administration of 25 mg (kg BM)-1 of haematoporphyrin derivative. The latter drug was characterized by better localization in the tumour area, leading to higher fluorescence contrast between neoplastic mass and surrounding healthy tissue, and consequently was preferable for tumour diagnosis in all the models under study.

Syngeneic anti-idiotypic antibodies eliminate excess radiolabeled idiotypes at experimental radioimmunolocalization

Significant improvements in tumor/nontumor ratio can be achieved by injections of nonlabeled anti-idiotypic monoclonal antibodies (MAbs) during radioimmunolocalization and radioimmunotherapy using MAbs to target experimental tumors. The in vivo effects of an anti-idiotypic MAb (alpha H7) against a radioiodinated, high affinity, low dissociation rate, monoclonal antiplacental alkaline phosphatase antibody (H7) was investigated. Following in vivo injection of the anti-idiotypic MAb, the radioactivity in experimental tumors was found to decrease only 25% while the reduction of corresponding radioactivity in nontumor tissues amounted to 65-85%, compared to the group receiving no anti-idiotypic MAbs. These results indicate that it is possible to partially clear the circulation and nontumor tissues from excess of radiolabeled idiotypic antibody, without significant decrease in specific tumor localization, increasing the tumor/nontumor ratio three- to fourfold. Circulating nontumor targeting radiolabeled antibodies is one of the major limiting factors in radioimmunotherapy today. Injection of anti-idiotypic MAbs could selectively significantly reduce the radiation dose to radio-sensitive tissues, i.e., bone marrow and intestine, thus improving efficiency in radioimmunoscintigraphy and radioimmunotherapy.

[Radio-somatomedins. III. Ovarian growth factor. Its clinical use]

We label ovaric growth factor (OGF) with Iodine-131 and probed its distribution in experimental mouse with radiopharmacology, toxicology and genetical test with encouraging results. The next step was its distribution in human volunteers and ovarian cancer. The new radiopharmaco have high concentration in ovarian cancer; that make possible its scan visualization "in vivo" for diagnoses and its internal radiation treatment without collateral or adverse effects in 6 month of follow-up (clinical and laboratorial) of the volunteers and patients in where the new radiopharmaco was probed.

A comparative study on contrast enhancement between 0.5- and 2.0-Tesla field strength in rabbit VX2 carcinomas

RATIONALE AND OBJECTIVES

Theoretically, the degree of contrast enhancement in magnetic resonance (MR) is affected by magnetic field strength. The authors conducted this study to compare the degree of MR contrast enhancement between 0.5 Tesla (T) and 2.0 T in VX carcinomas of rabbits.

METHODS

In 12 rabbits with VX2 tumors, both 0.5 T and 2.0 T MR imaging was performed within 1 day before and after intravenous injection of gadopentetate dimeglumine. Each rabbit received an initial standard dose (0.1 mmol/KG) followed by and additional standard dose (total, double dose) during the MR study at each field strength. The degree of contrast enhancement in the VX2 tumors was assessed quantitatively.

RESULTS

With standard and double dose studies, overall mean tumor and muscle contrast-to-noise ratio was higher at 2.0 T than 0.5 T by 95% and 81%, respectively. The double dose study showed higher contrast-to-noise ratio than the standard dose study at both field strengths.

CONCLUSIONS

Results indicate that the effect of contrast enhancement increases with field strength.

[Use of a neodymium lasers for fluorescent diagnosis and photodynamic destruction of tumors]

Fluorescence and photodynamic destruction of tumor tissues containing hematoporphyrin derivative was studied during excitation by II and III harmonics of AY:Nd(3+)-laser. This laser system can be effectively used for diagnosis of malignant tumours and photodynamic therapy.

[Experimental study of differentiation between tumor and inflammation using MR imaging: correlation between VX2 tumors and croton oil induced inflammation in the rabbit's femoral muscle]

We evaluated the various Magnetic Resonance (MR) sequences for differentiation between tumors and inflammation. Experimental models of rabbit's tumors (VX2) and inflammation induced by croton oil in the femoral muscle were used for this evaluation. Both types of lesions presented a high intensity area on T2-weighted and heavy T2-weighted images. An inflammatory lesion was revealed with iso-/low intensity area and tumors were defined as high signal lesions on Sinc saturation fat suppression T1-weighted, standard T1-weighted and fat suppression T1-weighted images by the 3 Point dixon method. T1, T2 values of tumor and inflammatory lesions were also measured. The T1 value of the tumors was 1186 +/- 58 msec (n = 5) and that of the inflammatory lesion was 1097 +/- 40 msec (n = 3). The T2 value of the tumors was 71 +/- 13 msec (n = 5) and that of the inflammatory lesions was 70 +/- 5.5 msec (n = 3). There were no significant differences between both the T1 and T2 values. Calculated relative proton density was 0.69 +/- 0.14 (n = 4) in the tumors, and 0.42 +/- 0.12 (n = 3) in the inflammatory lesions. A statistical difference (p < 0.05) was found in both value. These results suggest that a T2-weighted image is not useful for differentiation between tumors and inflammation, and a T1-weighted image might be useful for such differentiation. This phenomenon is related to the difference of the proton density.

Dynamics of tumor imaging with Gd-DTPA-polyethylene glycol polymers: dependence on molecular weight

Macromolecular contrast media offer potential advantages over freely diffusible agents in magnetic resonance (MR) imaging outside the central nervous system. To identify an optimum molecular weight for macromolecular contrast media, the authors studied a novel macromolecular contrast agent, gadolinium diethylenetriaminepentaacetic acid polyethylene glycol (DTPA-PEG), synthesized in seven polymer (average) molecular weights ranging from 10 to 83 kd. Twenty-eight rabbits bearing V2 carcinoma in thighs underwent T1-weighted spin-echo imaging before injection and 5-60 minutes and 24 hours after injection of the Gd-DTPA-PEG polymers or Gd-DTPA at a gadolinium dose of 0.1 mmol/kg. Tumor region-of-interest measurements were obtained at each time point to determine contrast enhancement dynamics. Blood-pool enhancement dynamics were observed for the Gd-DTPA-PEG polymers larger than 20 kd. Polymers smaller than 20 kd displayed dynamics similar to those of the freely diffusible agent Gd-DTPA. Above the 20 kd threshold, tumor enhancement was more rapid for smaller polymers. The authors conclude that the 21.9-kd Gd-DTPA-PEG polymer is best suited for clinical MR imaging.

Preclinical evaluation of gadolinium (III) texaphyrin complex. A new paramagnetic contrast agent for magnetic resonance imaging

RATIONALE AND OBJECTIVES

Gadolinium III texaphyrin (Gd[III] texaphyrin) complex, a new magnetic resonance imaging contrast (MRI) agent, was evaluated.

METHODS

In vitro relaxivity (1.5 T) and stability studies (5% dextrose) were conducted. Subchronic toxicity (8 males, 8 females; 2-20 mumol Gd(III) texaphyrin complex/kg body weight; 3 times per week for 3 weeks). Biodistribution and excretion studies were conducted in Sprague-Dawley rats; MRI studies were conducted in normal and tumor-bearing rats and rabbits.

RESULTS

Relaxivity values were as follows: r1 = 19 (mumol/L.sec)-1 and r2 = 22 (mumol/L.sec)-1. The 21-day subchronic toxicity study revealed no abnormalities. The compound is stable. Biodistribution demonstrated liver uptake. Magnetic resonance imaging in normal (n = 34) and tumor-bearing (n = 4) rats and normal (n = 8) and tumor-bearing (n = 19) rabbits revealed: significant (P < .05) contrast enhancement of liver and kidney after 1-17 mumol/kg of Gd(III) texaphyrin complex. Gadolinium (III) texaphyrin complex (2.5 mumol/kg) produced significant contrast enhancement of liver carcinomas in rabbits (n = 8). Thigh V2 carcinomas (n = 22) had selective (P < .05) enhancement, 5 mumol/kg. In rat fibrosarcomas (n = 4), 17 mumol Gd(III) texaphyrin complex produced significant enhancement up to 24 hours.

CONCLUSIONS

Gadolinium (III) texaphyrin complex appears to be an effective and safe MRI contrast agent.

Tumor-localizing fluorescent diagnostic agents without phototoxicity

In order to develop tumor-localizing fluorescent diagnostic agents without phototoxicity, various heterodimers linked by some spacers between a chlorine derivative and its Mn or Cu complex were synthesized. The representative agent of them was named HAT-DO1 and has a molecular formula of m-phthalyl-([13,17-bispropanoic acid-3-ethenyl-8-formylethylidene-7-hydroxy-2,7,12,18-tetramethyl- porphyrinate]-manganese (III))-[3'-ethenyl-8'-formylethylidene-7'-hydroxy-2',7',12',18'-te tramethyl- porphine-13',17'-bispropanoyl aspartic acid]-bishydrazone.

Carotenoporphyrins as selective photodiagnostic agents for tumours

The covalent binding of a carotene moiety to one phenyl ring and meso-tetraphenyl-substituted porphyrins (see Figure 1) efficiently quenches the photosensitising activity of the porphyrin while a relatively large yield of fluorescence emission around 650 nm is retained. Pharmacokinetic studies performed with two carotenoporphyrins (CPs) and the corresponding porphyrins (Ps) in Balb/c mice bearing an MS-2 fibrosarcoma show that the two Ps give a high selectivity of tumour localisation (tumour/peritumoral tissue ratios of dye concentration ranging between c. 30 and 90 at 24 h after injection of 4.2-8.4 mumol kg-1 in a Cremophor emulsion) and photosensitive tumour necrosis upon red light irradiation. For the same injected doses, the two CPs show no tumour-photosensitising activity even though they localise in the tumour in concentrations of the order of 10-40 micrograms g-1 at 24 h with tumour/peritumoral ratios larger than 10. Thus, the fluorescence emitted by these CPs in the tumour can be used for photodiagnostic purposes with no risk of skin photosensitisation. However, this approach is presently limited by the large accumulation and prolonged retention of the CPs in the liver and spleen.

In vivo 31P MRS of experimental tumours

More than 50% of cancers fail to respond to any individual treatment and tumour follow-up after treatment plays a major role in routine therapy planning and pharmacological research. Today, MRS is the only technological approach providing non-invasive access to tumour biochemistry. Ten years ago, expectations were raised concerning 31P MRS as an exciting and promising technical approach to the study of tumours. However the expectations have not always come to fruition. How close are we now to seeing routine 31P NMR in clinical oncology? This review of the 127 published papers shows spectroscopy results in more than 150 experimental animal tumour models. These tumour/host/treatment systems provide us with a useful basis to evaluate the current state of the art, summarize the basic knowledge presently available, determine the key points underlying the present disappointment of some clinical oncologists and stimulate new basic research. The information collected concerns the discussion of the reliability of experimental models in oncology, the technical improvement of magnetic resonance technology and the monitoring of bioenergetic status, pH regulation and phospholipid metabolism in treated and untreated tumours. Recent advances (two-thirds of the papers have been published in the last 5 years) seem to provide more optimistic perspectives than those generally accepted a few years ago, in the depressing period following early pioneering work.

Factors affecting perceived tumor volumes in magnetic resonance imaging

Irregularly structured brain tumors, such as glioblastomas, challenge attempts to visualize and quantify their three dimensional structure. Magnetic resonance imaging (MRI) represents one tool for attempting to noninvasively track tumor size. MR images demonstrate widely varying perceived tumor margins. In addition, adjunct therapies, such as the administration of steroids, greatly affect the volumes perceived in images formed by certain pulse sequences. In this study tumors were grown in 15 dogs and the tumor size tracked for a period of time. The dogs were placed on dexamethasone for a week and another series of scans was obtained. No other therapies were provided. The data for visualized tumor size are provided for T1, T2, and proton density. Weighted images are provided and the relationships between the scans are discussed.

Pattern recognition of 31P magnetic resonance spectroscopy tumour spectra obtained in vivo

Pattern recognition has been applied to the analysis of in vivo 31P NMR spectra. Using four different classes of tumour and three types of normal tissue, cluster analysis and artificial neural networks were successful in separating and classifying the majority of samples analysed. Although the phosphomonoester and P(i) regions appeared to be the most important spectral features, data representing the entire 31P spectrum were required for best separation of the tumour and tissue classes.

Laser-induced fluorescence in malignant and normal tissue of rats injected with benzoporphyrin derivative

Laser-induced fluorescence was used to characterize the localization of intravenously administered benzoporphyrin derivative-monoacid (BPD-MA) 3 h postinjection in different rat tissue types, including an induced experimental malignant tumor. A comparison of the fluorescence properties and demarcation potential between the newer sensitizer BPD-MA and four other substances, hematoporphyrin (HP), polyhematoporphyrin ester (PHE), tetrasulfonated phthalocyanine (TSPc) and the commercially available Photofrin earlier investigated, is included. The fluorescence light was induced with a nitrogen laser, emitting at 337 nm. The fluorescence spectrum in the region 380-750 nm was analyzed by a polychromator equipped with a diode array detector. The demarcation potential between tumor and surrounding tissue in terms of fluorescence signal for the tumor model used was 2:1 for BPD-MA. In comparison with the other drugs, HP shows about the same demarcation potential, whereas Photofrin and PHE exhibit about 3 times better and TSPc about 1.5 times better demarcation. By also employing the endogenous tissue fluorescence signature the contrast was enhanced by a factor of about 2 for each of the five drugs.

[Effect of lipiodol on MR images evaluation by dynamic MR imaging with intraarterial lipiodol injection in the rabbit VX-2 tumor]

We evaluated the effect of lipiodol on the MR image by using dynamic MR imaging (MRI) with an intraarterial lipiodol injection in the VX-2 tumor. The signal intensity of the tumor had been risen gradually during the dynamic MRI, using T 1-weighted Spin Echo techniques. The high intensity areas on the dynamic MRI nearly corresponded with the lipiodol accumulated areas on CT. On the micrograph, no necrosis or degeneration of the tumor cell was visible. We conclude that the presence of lipiodol will affect the signal intensity of T 1-weighted MR images.

Proton spectroscopy in vivo

1H magnetic resonance spectroscopy (MRS) has attracted much attention in recent years. Since the proton is the most sensitive stable nucleus for MRS, and since almost all metabolites contain hydrogen atoms, it is possible to perform a noninvasive chemical analysis on tissues deep within the body of a subject. Technical solutions to the elimination of water and lipid signals as well as resolution of the large number of potential metabolite peaks have been found. Most current work is on the brain, much of it in humans. This review begins with a consideration of these technical problems and also localization, editing, quantitation, and interpretation of spectra. Two diseases are considered in detail: cerebral ischemia (including stroke and neonatal ischemic/hypoxic injury) and cancer; a further section briefly reviews studies on other diseases. In the immediate future, 1H MRS is likely to benefit from a number of technical advances: higher field magnets, better control of gradients and eddy currents, more sophisticated radiofrequency (RF) pulses, and 1H-observe/13C-edited spectroscopy all offer potential improvements. Another major improvement will come from increased user-friendliness of clinical spectrometers and use of automated objective methods for spectroscopic data analysis.

A new technique for detecting fluorescently labelled cells at very low densities

We have developed a new cytometric method that has the potential for detecting fluorescently labelled cells at very low densities against a high density background of non-fluorescing cells of similar size. The method uses a Waveform Analysis Interface which is an electronic device that is essentially an "add-on" to a flow cytometer. It takes the amplified fluorescence and scatter signals from the flow cytometer and measures their intensities at microsecond intervals. It can be programmed to react only to cells with specific characteristics and ignore all others. In this mode it is possible to detect fluorescently labelled cells at densities down to about 1.mL-1 against a background density of non-fluorescent cells of similar size of more than 1 x 10(7).mL-1. This application may have considerable potential for cancer diagnosis and therapy.

Improved tumor localization with (strept)avidin and labeled biotin as a substitute for antibody

Because of its short physical half life, the use of anti-tumor antibodies radiolabeled with 99mTc has necessitated early (i.e. 2-6 h post-administration) imaging. It is possible that at these early times localization of antibodies in certain tumors may be largely due to non-specific processes. If so, other proteins or agents may be preferred for early imaging of solid tumors. We have investigated tumor localization with labeled biotin administered subsequent to unlabeled and unconjugated streptavidin. Nude mice bearing anti-CEA tumors (LS174T) received 10 micrograms of 111In-labeled anti-CEA antibody (C110) or 111In-labeled streptavidin with sacrifice 5 h later. In an examination of pretargeting, other animals received 50 micrograms of unlabeled streptavidin followed 3 h later with 1 micrograms of 111In-labeled biotin (EB1) and sacrifice 2 h later. The biodistribution of labeled streptavidin was similar to that of labeled specific antibody except for lower blood and higher kidney levels. Tumor levels were also lower with labeled streptavidin but, because of still lower levels in liver and blood, the tumor/normal tissue ratios were improved. When unlabeled streptavidin was administered and followed by labeled biotin (pretargeting), tumor levels were further reduced modestly; however, normal tissue levels were greatly reduced such that the tumor/blood and tumor/liver ratios were 10.6 and 2.2 vs 1.5 and 0.5 for the specific antibody. Improvements were seen in all tissues sampled with the exception of kidney and muscle. A further control of labeled biotin alone (without the preinjection of streptavidin) showed minimal accumulations in all tissues with the exception of kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor diagnosis by PET: potential of seven tracers examined in five experimental tumors including an artificial metastasis model

The potential of seven tracers for the metabolic imaging of tumors by positron emission tomography was studied using five experimental tumor models. The tracers examined were 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), 2-deoxy-2-[18F]fluoro-D-galactose (2-[18F]FdGal) and 2-deoxy-2-[18F]fluoro-L-fucose (2-[18F]FdFuc) for investigating energy metabolism. L-[methyl-11C]Methionine ([11C]Met) and 6-[18F]fluoro-L-fucose (6-[18F]FFuc) were used for assessing protein and glycoprotein synthesis, while [3H]thymidine ([3H]Thd) and 2-deoxy-5'-[18F]fluorouridine ([18F]FdUrd) were used to investigate nucleic acid metabolism. The highest mean uptake by the five different tumors was found for [3H]Thd, followed in order by [18F]FDG, [11C]Met, 2-[18F]FdGal, [18F]FdUrd, 2-[18F]FdFuc and 6-[18F]FFuc. The tumor-to-tissue uptake ratios indicated that the nucleosides, [11C]Met and 6-[18F]FFuc were better tracers in the brain region. All the tracers except for the fucose analogs were suitable for the thoracic region, while [11C]Thd and [18F]FDG were superior in the abdominal region. In comparison with the primary tumor model of Lewis lung carcinoma (3LL), [3H]Thd uptake in the artificial metastatic 3LL model showed the maximum enhancement, followed by [18F]FDG, [11C]Met and the other tracers. The [18F]FDG uptake correlated with the [3H]Thd uptake. [18F]FdUrd, 6-[18F]FFuc and 2-[18F]FdGal could be used for distinguishing different types of tumors. The combined use of these radiotracers can possibly allow the assessment of tumor metabolism, and this indicates the viability of tumors.

Alkaline phosphatase as a reporter of cancerous transformation

Serum levels of alkaline phosphatase (AP) have been used in the clinical evaluation of numerous diseases, including malignancies, for half a century. The aberrant expression of AP genes in cancer cells has led to the suggestion that APs are oncofetal proteins and thus, could be involved in tumorigenesis. Tumors which express these AP isozymes can be broadly divided into two groups: (a) those with an enhanced production of an isozyme normally expressed in the tissue (eutopic expression) and (b) those showing expression of one or more isozymes not identified in the normal tissue (ectopic expression). Moreover, many tumors show simultaneous expression of two or more different AP isozymes. In the absence of known biological functions of the AP isozymes several different mechanisms underlying their expression in tumor cells could explain the findings. In an attempt to clarify the function of APs, this laboratory is engaged in the study of unique properties of the mammalian APs as possible clues to their function, i.e., (a) the phosphatidylinositol glycan attachment of APs to the cytoplasmic membrane, (b) the uncompetitive inhibition properties of APs and (c) the extracellular matrix binding domain of APs. This laboratory is also undertaking the task of targeting each of the mouse AP isozymes by homologous recombination to generate mouse models of hypophosphatasia to analyze in detail the in vivo consequences of AP isozyme deficiencies.

[Experimental studies on the dynamics of anticancer agents in transcatheter arterial chemo-embolization. Magnetic resonance imaging using emulsions containing lipiodol and Gd-DTPA]

Transcatheter arterial chemo-embolization with lipiodol and anticancer agents (LP-TACE) is a highly effective therapeutic method for treating liver cancer. It has been difficult, however, to evaluate how lipiodol, an oil, and anticancer agents dissolved in an aqueous contrast medium are retained in tumors. This paper reports the study on the dynamics of anticancer agents administered in LP-TACE both in vitro and in tumor-bearing animals using emulsions produced by mixing lipiodol and adriamycin (ADM) dissolved in Gd-DTPA. The results were as follows. 1) ADM was dissolved in contrast mediums (60% Urografin and Gd-DTPA) and each solution was emulsified by mixing with lipiodol. The emulsion separated into two distinct layers 5 min. after mixing. From this observation it is guessed that lipiodol and anticancer agents also separate in tumors after administration in LP-TACE. 2) Rabbits with VX2 carcinoma implanted in their lower limbs were treated by chemo-embolization and subjected to serial observations for changes in signals on MRI. The signal intensity markedly increased, persisting until one week after administration, when the tumor was resected. This change may have been owing to Gd-DTPA retained in the tumor, indicating that the anticancer agent is not washed out, even after separating from lipiodol, but is retained in the tumor. 3) When ADM was dissolved in Gd-DTPA and intraarterially infused without being mixed with lipiodol, the intensity of the signal on MRI was the same as that in LP-TACE immediately after the administration, and gradually decreased thereafter. This result indicates earlier washout of the anticancer agent when administered without being combined with lipiodol. Quantitative analysis of the tumor resected one week after the treatment also revealed ADM levels with less than 10% of those in LP-TACE, suggesting the possibility of estimating intratumoral concentration of anticancer agents. This was evaluated on the basis of the signal intensity in the tumor using MRI. 4) A comparison of lipiodol accumulation on CT and signal changes induced by Gd-DTPA on MRI suggested that even after separation from lipiodol, the anticancer agent extends to microvessels in the interior part of the tumor.

Photodynamic therapy in general surgery

Authors' experience in detecting neoplasms by a computerized telethermographic system in animal models is reported. The new technique seems to have a great potential as a photo-diagnostic method particularly when followed by the surgical treatment or the photodynamic therapy (PDT) of the neoplastic lesions. Literature reports on the PDT of tumors are reviewed.

From laboratory to clinic: the development of an immunological reagent

Access to a wide range of high quality and increasingly sophisticated reagents and equipment has underpinned the great surge of knowledge in basic immunology and the growing interest in clinical immunointervention. In this article, the first in an occasional series on immunological research and development in industry, Sue Bright and colleagues outline the key steps in a development programme to take a humanized monoclonal antibody into the clinic. The procedures involved in developing such reagents, particularly for clinical use, are long and require considerable ingenuity and scientific creativity.

Tissue oxygenation: a novel determination using 19F surface coil NMR spectroscopy of sequestered perfluorocarbon emulsion

This work examines the variation with oxygen tension (pO2) of the individual spin-lattice relaxation times (T1) of the 19F resonances of the perfluorocarbon emulsion Oxypherol-ET (FC-43). A linear relationship between 1/T1 and pO2 has been confirmed for all four resonances at any specific temperature. Using a saturation recovery sequence, T1 has been successfully measured using surface coil NMR spectroscopy. This has facilitated measurement of T1 in vivo in a subcutaneous murine tumor. Mice were predosed with Oxypherol-ET emulsion: following complete vascular clearance of the perfluorocarbon, 19F signal was observed specifically from material sequestered in tissue, thus avoiding flow artifacts. Comparison of the pO2 estimated from each of the 19F resonances provided an internal consistency check. A pO2 = 0.1 +/- 2.2% was determined in a Meth-A murine tumor. When the mouse breathed carbogen (95% O2, 5% CO2) no significant change in tumor pO2 was detected, whereas the pO2 in the liver showed a distinct increase.

New concepts in monoclonal antibody based radioimmunodiagnosis and radioimmunotherapy of carcinoma

It is now generally agreed that while numerous monoclonal antibodies (MAbs) have been shown to efficiently target tumors in patients, much still needs to be accomplished to optimize MAb based tumor targeting and the use of MAbs in the therapy of human carcinoma. This article will review some recent studies undertaken in our laboratory in an attempt to generate novel recombinant constructs and test new principles to aid in optimizing MAb based diagnosis and therapy. Three areas will be covered: (a) the analysis of dose fractionation protocols; (b) the generation of recombinant/chimeric (rec/chi) MAbs including the generation of a single chain antigen binding protein (SCA); and (c) the use of recombinant interferons (rec IFNs) to selectively up-regulate tumor antigen expression. Each of these topics has been previously described in detail and appropriate references to these articles are included.

Assays for 8-hydroxy-2'-deoxyguanosine: a biomarker of in vivo oxidative DNA damage

HPLC with electrochemical detection (HPLC-EC) is a highly sensitive and a selective method for detecting 8-hydroxy-2'-deoxyguanosine (oh8dG), a biomarker of oxidative DNA damage that is formed from hydroxyl radical attack of guanine residues in DNA. We propose that the noninvasive measurement of oh8dG in urine can be used to estimate in vivo oxidative damage. Application of this assay to urine samples obtained from rats of different ages and various species provide examples of the utility of this assay. The measurement of steady-state levels of oh8dG in DNA combined with the urinary excretion rates of oh8dG and oh8Gua, offer a powerful approach for estimating oxidative DNA damage and its repair. This method will be useful for studies designed to investigate the relationship of oxidative stress in DNA damage and the role of this damage in aging and cancer.

The reliability of palpation in the assessment of tumours

There is now a joint UICC-AJC classification for cervical lymph nodes based mainly on the size of the nodes. There is a recognized error in palpation, not only for detecting the presence of tumour but also its size. This study used an animal tumour model system to compare the ability of 6 independent observers of varying experience to detect and stage superficially transplanted growths. A preclinical medical student was as good as a Consultant ENT Surgeon in predicting the presence of tumour but the ability to stage tumours accurately was related to experience. Whilst the most experienced observers accurately estimated the size of tumours less than 2 cm, they were less accurate for larger (greater than 2 cm) tumours which were constantly understaged. This phenomenon may have important clinical implications particularly related to current nodal staging criteria.

Identification of tumor hemorrhage in an animal model using spin echoes and gradient echoes

We report here how magnetic resonance imaging can be used to gain definitive information about tissue pathology by the combined use of spin-echo and gradient-echo sequences. We also show how artifacts arising from respiratory motion can be eliminated by using a simple respiratory gating technique.

Tissue-localizing properties of some photosensitizers studied by in vivo fluorescence imaging

Using fluorescence imaging, the tissue-localizing properties of five photosensitizers were studied in vivo in tumours in 'sandwich' observation chambers and in tumours growing on thigh muscle. The preliminary results indicate that of the three photodynamically active dyes tested (haematoporphyrin derivative, Photofrin II and aluminium phthalocyanine tetrasulphonate), the phthalocyanine possesses the best tumour-localizing properties. This makes it possible to combine tumour fluorescence detection and photodynamic therapy with reduced skin photosensitivity. The two photodynamically inactive dyes tested (uroporphyrin I and acridine red) may be useful for application in fluorescence imaging to localize superficial tumours without inducing skin photosensitivity. In particular, acridine red has remarkable tumour-localizing properties, but is rather toxic.

Prediction of cancer potency using a battery of mutation and toxicity data

Correlations between the carcinogenic potencies of 146 known mouse carcinogens and potency estimates determined from (i) Ames test results, (ii) a battery of mutation test results, and (iii) a battery of mutation and toxicity data are presented. The lowest correlation was found using Salmonella mutagenic potency (r = 0.37). The highest correlations were found using the battery of mutation and toxicity data to predict the potency of lung carcinogens (r = 0.94) and liver carcinogens (r = 0.91). The results suggest that short-term batteries which include tests for both mutagenicity and toxicity will be able to predict carcinogenic potency better than current batteries relying solely on mutagenicity tests.

Disulfide bond-targeted radiolabeling: tumor specificity of a streptavidin-biotinylated monoclonal antibody complex

A site-specific labeling method was developed in which sulfhydryl groups of a murine IgG2a anti-ovarian monoclonal antibody, 5G6.4, were biotinylated with N-iodoacetyl-N'-biotinylhexylenediamine (Compound 1) following partial reduction of disulfide bonds with dithiothreitol. Reaction of 1-alkylated 5G6.4 with 125I-streptavidin gave immunoreactive streptavidin-1-biotinylated complexes. Radio-fast protein liquid chromatography data were consistent with the formation of a stable monovalent streptavidin-half-antibody complex as the major species. In vivo specific localization of these radioantibody conjugates to human tumor xenografts of ovarian carcinoma was confirmed by a comparative biodistribution study in nude mice using as a control the nonspecific 125I-streptavidin-1-alkylated UPC-10 (an irrelevant IgG2a monoclonal antibody) complex prepared analogously as described above. Tumor uptake for radiolabeled 5G6.4 [0.279 +/- 0.041% (SE) kg injection dose/g) was significantly greater [P less than 0.025] than for UPC-10 [0.165 +/- 0.027% kg injection dose/g]. The tumor:blood ratio (7.38 +/- 1.285) for 5G6.4 was approximately 3 times that for UPC-10 (2.48 +/- 0.708, P less than 0.01). This sulfhydryl site-directed approach demonstrated that reduced disulfides of monoclonal antibodies are viable sites for attaching labels without significant loss of in vitro and in vivo immunoreactivity.

Site-specifically radioiodinated antibody for targeting tumors

Labeling of an antibody site specifically through its carbohydrate regions preserves its antigen-binding activity (Rodwell et al., Proc. Natl. Acad. Sci., 83: 2632, 1986). Previously site-specific labeling studies have conjugated antibodies with metallic radioisotopes or drugs. We now report site-specific labeling with a new radioiodinated compound, 2-hydroxy-5-iodo-3-methylbenzoyl hydrazide, whose synthesis we described earlier (Belinka et al., Biochemistry, 27: 3084, 1988). The compound is reacted with aldehyde groups produced by specific oxidation of the carbohydrate portion of the antibody with sodium m-periodate. Optimized conjugation conditions give good recovery of active antibody containing 10 groups per molecule. The conjugate is stable in solution for at least several weeks at both 4 and -70 degrees C. When injected into nude mice bearing LS174T human cancer xenografts, the conjugate of B72.3 antibody localizes well to tumor tissue, with low uptake by other organs. This biodistribution is similar to that of conjugate prepared by using solid-phase chloramine-T (Iodohead). There are only two significant differences. First, the carbohydrate conjugate is much less susceptible to dehalogenation, and thus shows much less thyroid uptake. Secondly, the biological half-life of the carbohydrate conjugate was about half that of the chloramine-T one. This could be due primarily to lysis of the hydrazine bond through which the antibody is attached to the compound, which would then be excreted rapidly by itself. The new reagent will be especially useful for antibodies which either cannot be labeled by chloramine-T methods, or whose activity is impaired by them.

Contribution of immunohistochemistry toward the diagnosis of tumors of laboratory rats

A polyclonal antibody detecting S-100 protein (S-100) and a monoclonal antibody demonstrating epithelial cell (Lu-5) were used in addition to routine, hematoxylin-eosin stain to improve the identification of tumors of neural or epithelial origin diagnosed in conventionally treated tissue from rat bioassays. Among 108 lesions tested for S-100, 51 reacted positively; they included benign and malignant schwannoma, endomyocardial disease, some cases of benign and malignant thymoma, and renal tubular adenoma. S-100 protein is considered particularly useful for discriminating of neoplasms of Schwann cell origin from mesenchymal tumors. 31 of 51 lesions tested for Lu-5 reacted positively: they comprised adenoma, carcinoma, benign and malignant thymoma and atriocaval node tumor of the heart. Lu-5 was especially useful to distinguish epithelial from mesenchymal neoplasms and was capable of identifying epithelial elements in lymphocyte-rich thymomas as well as in dedifferentiated or autolytic tumors. The binding of both antibodies in neoplastic tissue was compared with a complete set of anatomically normal rat tissues.

Applications of immunohistochemistry in rodent tumor pathology

Immunohistochemistry can serve as a valuable adjunct to rodent tumor pathology. Specific antigens may be localized to cells and tissues in normal organs, preneoplastic lesions, and benign and malignant tumors. The immunoreactivity of polyclonal and monoclonal antibodies to these antigens provide a more accurate basis for tumor diagnosis and aid in understanding pathogenesis. Ultimately, the application of more precise understanding of tumor histogenesis and diagnosis will lead to more accurate interpretations of tumor incidence data for safety assessment in toxicology.

Tumor characterization using unconventional MR modalities

This article reviews many of the promising new magnetic resonance (MR) modalities for the characterization of tumor structure and metabolism, excluding 31P magnetic resonance spectroscopy (MRS). The report focuses on recent work with localized proton MRS, MR imaging of diffusion and perfusion, and work on imaging bound pools of sodium ions. The technical problems associated with these methods are discussed, along with the unique information each provides. Many of these techniques have already been used in studies of human disease, or are of sufficient importance that clinical applications are imminent.

Monoclonal antibody-coated magnetite particles as contrast agents in magnetic resonance imaging of tumors

A highly specific and powerful magnetic resonance imaging contrast agent has been prepared by coating magnetite (Fe3O4) particles with monoclonal antibodies directed against a tumor antigen. The preparation maintains both the immunoreactivity of the monoclonal antibody and the full relaxing capability of the magnetite particle. MRI image contrast by spin-echo methods can be easily induced in a concentration range of 1-10 nM of the antibody-coated magnetite particles.

Applications of magnetic resonance techniques to deep tumor hyperthermia

Magnetic resonance imaging and spectroscopy have the potential for supporting clinical hyperthermia advances in the treatment of deep tumors. Current spectroscopic techniques can monitor treatment delivery and effectiveness through changes in metabolism and blood flow. Spectra can be obtained in vivo, repetitively and noninvasively; furthermore, current techniques have been implemented to give spatially resolved information. Further advances in MRI/MRS techniques may make it possible to obtained the information necessary for individualized treatment planning, for qualitative monitoring and assessment of treatment results, and for the measurement of thermal fields in vivo.

Perfluorocarbon imaging in vivo: a 19F MRI study in tumor-bearing mice

Multiresonance perfluorocarbon emulsions (Oxypherol and Fluosol-DA) were imaged in tumor-bearing mice using 19F spin-echo magnetic resonance imaging in vivo. Multiple thin-slice fluorine images free of chemical shift artifacts were obtained in 13 minutes and these were correlated with proton images obtained during the same experiment to delineate the anatomic distribution of perfluorocarbons. Sequential images were used to determine the time course of the distribution and the retention of the compounds in tumors and organs. 19F MR spectroscopy was used ex vivo to determine with high sensitivity the relative concentration of perfluorocarbons in different tissues and organs and to confirm the results obtained from imaging experiments. The fluorine images visually demonstrated the preferential localization of the perfluorocarbons in the liver and spleen; shortly after injection, the images also revealed the highly vascularized tumor-chest wall interface. Imaging and spectroscopy together showed that the perfluorocarbons were removed from the blood pool within hours and remained sequestered in tissues at later times; the highest concentrations were found in the spleen and liver, where the agents were retained without spectral changes for the duration of these studies. The perfluorocarbons accumulated within tumors at dose-dependent concentrations, one to two orders of magnitude smaller than those observed in the spleen and liver.

[Gd-DTPA-supported magnetic resonance tomographic perfusion follow-up of shockwave-treated tumors]

The signal characteristics of 14 shockwave-treated and 14 solid control tumors were studied before and after injection of Gd-DTPA in an animal model. T1-weighted images of shockwave-treated tumors documented no significant signal intensity increase after contrast media injection in comparison with the untreated control tumors. The reduction of perfusion in shockwave-treated tumors can be documented in vivo by the signal intensity changes of the tumors after contrast media injection.

Doubly tuned solenoidal resonators for small animal imaging and spectroscopy at 1.5 Tesla

The design and construction of solenoidal resonators for use with small animals in a 1.5-Tesla clinical imaging system are described. The coils have been designed to exploit the B1 distributions of two resonant modes of a four-turn solenoid whose windings are in parallel. Both singly and doubly tuned versions have been constructed. 1H images of normal and pathologic anatomy in mice and rats as well as a 31P spectrum of a Walker 256 rat sarcoma are presented. A primary advantage of this design is that the coils are easy to build and implement while providing the necessary sensitivity to allow high quality images to be obtained with no changes to the hardware or software of the clinical unit.