Biomedical subjects

M Rusckowski

Publications and source records attributed to M Rusckowski.

At least 55 records · Page 3Linked to original sources

PubMed1991

New indium-111 labeled biotin derivatives for improved immunotargeting.

Investigations into the use of streptavidin-conjugated antibodies and labeled biotin to improve radioimmunotargeting have shown background levels drastically reduced over the conventional approach. Nevertheless, accumulation of 111In-biotin in normal tissue as well as streptavidin-independent accumulation in tumor, was observed. In this work, the effect of altering the biotin molecule to reduce this nonspecific uptake without decreasing specific localization has been investigated. Three EDTA and DTPA derivatives of biotin have been synthesized and investigated along with a commercial biotin derivative (DTPA-B2). The labeled biotin chelates were administered i.p. to normal mice implanted with avidin beads in one thigh. A wide variation in biodistribution was seen among the biotin derivatives. The most favorable results were obtained with biotinyl-hydrazino-EDTA (EDTA-B1), which showed the lowest accumulation in normal tissues but equivalent uptake in the target with respect to the other compounds. Averaged over 8 tissues sampled, the target-to-nontarget ratio was 140 vs 9 for EDTA-B1 vs DTPA-B2 (N = 6) at 24 h post administration. Similar observations have been made in culture with two tumor cell lines: positive accumulation of both DTPA-B2 and EDTA-B1 was measured in tumor cells independent of streptavidin-antibody conjugate, however in the case of the latter derivative, this accumulation was 3-5 fold lower. These studies show that modification of the biotin species can alter accumulation in normal tissues as well as the antibody-streptavidin independent accumulation in tumor tissue.

Animals↗

PubMed1991

Initial clinical study of indium-111-labeled clone 110 anticarcinoembryonic antigen antibody in patients with colorectal cancer.

A murine monoclonal antibody directed against carcinoembryonic antigen (CEA) was labeled with indium-111 (111In) by means of a benzylisothiocyanate derivative of diethylenetriamine penta-acetic acid (DTPA) and used for clinical radioimmunodetection studies. Twenty-one patients having a history of surgically resected colorectal cancer and rising serum CEA levels suggestive of tumor recurrence were studied. Patients were infused over 20 minutes with 5, 10, or 20 mg of the monoclonal antibody labeled with 5 mCi of 111In. The mean radiochemical purity was greater than 96%. No toxicity was seen. The stability of the radiolabel on antibody in patient serum was demonstrated by high-performance liquid chromatography (HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with autoradiography, and immunoprecipitation for up to 96 hours after infusion. Tumor sites were identified in 20 of 21 patients. Sites of antibody accumulation in 20 patients were confirmed as tumor either by resection at laparotomy (16 patients) or fine-needle biopsy (four patients). Nine patients who had the identified lesion resected or irradiated showed return of the serum CEA antigen level to normal or near normal values. In the absence of high levels of circulating CEA (greater than 500 ng/mL), the disappearance of radioactivity from patient serum demonstrated first order elimination kinetics, with a mean half-life of 38 hours. The serum half-life was not affected by the dose of antibody administered or by serum CEA titers below 500 ng/mL. Despite a mean liver uptake of 18% injected dose (ID) 24 hours after administration, hepatic metastases were easily visualized as areas of increased uptake of radioactivity. Radioimmunodetection of recurrent colorectal cancer, not detected by computed tomographic (CT) scans, appears achievable with this agent. This may allow successful clinical intervention in selected patients.

Adult↗

PubMed1990

Pharmacokinetics in patients of an anti-carcinoembryonic antigen antibody radiolabeled with indium-111 using a novel diethylenetriamine pentaacetic acid chelator.

The pharmacokinetics of the C110 anti-carcinoembryonic antigen antibody radiolabeled with 111In via a novel benzylisothiocyanate derivative of diethylenetriamine pentaacetic acid have been determined in 12 patients. The chelator was attached to the protein via a thiourea bond and in such a way that all 5 carboxymethyl arms were presumably able to participate in chelation. Patients with known or suspected colorectal carcinoma received between 5 and 20 mg of the IgG antibody labeled with 5 mCi of 111In. Individual organ radioactivity levels were quantitated, and serum and urine samples were analyzed, principally by size exclusion high-performance liquid chromatography (HPLC). Total urinary excretion averaged 0.18% of the injected dose/h with large patient to patient variation. At early times postadministration (less than 8 h) the predominant radiolabeled species in urine was free diethylenetriamine pentaacetic acid most probably administered as a small radiocontaminant in the injectate. Thereafter, radioactivity in urine was primarily present as a low molecular weight catabolic product. Analysis of serum by size exclusion HPLC occasionally showed 3 radioactivity peaks, 2 of which are due to circulating immune complexes and labeled antibody. The third peak is of low molecular weight and is due to one or more products of antibody catabolism. Transchelation of 111In to circulating transferrin was observed but at modest levels. Quantitation of organ radioactivity showed that 18 +/- 4 (SD)% of the injected dose was in the liver at 1 day postadministration and 1.4 +/- 1.1 and 1.2 +/- 0.9% was in the spleen and in both kidneys, respectively, at this time. The mean half-life for clearance of total injected radioactivity was fitted to a single exponential and was found to be 34 h (SD, 14 h; N = 13) and that for antibody alone, assessed by size exclusion HPLC analysis of serum samples, was calculated to be 22 h (SD, 8 h; N = 10). Neither of these values nor organ radioactivity levels were affected by antibody-loading dose.

Adult↗

PubMed1990

Pharmacokinetic modeling of radiolabeled antibody distribution in man.

This paper describes a method for the interpretation of the pharmacokinetics in cancer patients of an anti-CEA monoclonal antibody labeled with 111In. To determine the fate of the radiolabeled antibody administered i.v. to ten colon patients, the radioactivity contained in liver, spleen, kidneys, bone marrow, and tumor was measured and serum samples were counted. In addition each serum and urine sample was also analyzed by HPLC. The labeled antibody and two other radioactive species were observed in serum: an immunocomplex and a catabolic product. The computer program SAAM was used to fit the data. Thus, the rate constants for a number of pharmacokinetic models were calculated using the time-dependent serum radioactivity curves for each of the three species and the time-dependent radioactivity contained in normal organs. We also computed the model parameters for different connections between different organs, and using noncompartmental methods, the transit time, permanence time, and yield of those organs. Our results suggest that the immunocomplexes are formed in the circulation between circulating antibody and antigen, and that the rate of uptake by the liver depends on the concentration of the antibody in blood and not of the immunocomplex. Following deposition in the liver, free antibody does not appear to reenter the circulation, but once there it is catabolized. All breakdown products are then cleared into urine via serum.

Antibodies, Monoclonal↗

PubMed1990

Imaging of tumor in patients with indium-111-labeled biotin and streptavidin-conjugated antibodies: preliminary communication.

Tumor localization in patients has been achieved through the in vivo use of streptavidin and biotin. In these preliminary studies, the monoclonal antibody HMFG1 was conjugated with streptavidin and 1 mg was administered intravenously to each of 10 patients with documented squamous cell carcinoma of the lung. Two to 3 days later, 111In-labeled biotin was also administered intravenously. No evidence of toxicity was observed. Background radioactivity levels were reduced in liver (1% ID at 24 hr) and kidneys (2%) and in all other normal tissues and blood. Images of lung tumor were obtained in as little as 2 hr following administration of labeled biotin. In eight patients, tumor was detected with labeled biotin alone without the previous administration of streptavidin-conjugated antibody but in three of these patients, the images were improved with the prior administration of conjugated antibody. These results suggest that this approach may improve the tumor-to-normal tissue radioactivity ratios in radioimmunotargeting.

Antibodies, Monoclonal↗

PubMed1987

Pharmacokinetics of 111In-labeled OC-125 antibody in cancer patients compared with the 19-9 antibody.

We recently reported on the pharmacokinetics in 14 cancer patients of the 19-9 antibody radiolabeled with 111In. We have now repeated this investigation in 18 cancer patients using the OC-125 antibody, in part to compare the in vivo behavior of two murine monoclonal antibodies of the same subclass administered as the F(ab')2 fragments, by the same route and at the same dose. As in the earlier investigation, 1 mg of fragments was infused i.v., and organ quantitation was obtained for up to 72 h along with frequent blood and urine samples for chromatographic evaluation. Analysis of urine showed that activity clearance by this route amounted to 0.29%/h and consisted of labeled DTPA only in early samples and metabolic products thereafter. Analysis of serum samples often showed the presence of a high-molecular-weight species appearing within 24 h. This species is probably due to antibody binding to circulating antigen, although the percentage of circulating activity present as this species did not correlate well with circulating antigen levels. As before, organ accumulation was greatest in the liver, although levels were significantly reduced (12% compared to 20% of administered dose at 24 h, P less than 0.01). Plasma clearance was also significantly different: whereas the label in the case of the OC-125 antibody showed one-compartment clearance kinetics and remained in the plasma compartment, in the 19-9 case the label diffused to a second, unidentified compartment.

Antibodies, Monoclonal↗

PubMed1987

Investigations of avidin and biotin for imaging applications.

The attractive properties of avidin (streptavidin) and biotin, in particular their strong affinities (Kd = 10(-15)M), may be used to advantage in imaging applications. These molecules have been used in this preliminary investigation to improve the targeting of 111In in animals. Antibodies have been conjugated with biotin and administered unlabeled while, at a later time, the radiolabel was administered attached to DTPA-coupled avidin or streptavidin. An alternative procedure was also considered whereby the antibodies were conjugated with avidin and administered before the administration of radiolabeled biotin. Using a model in which the target consisted of conjugated agarose beads deposited in the peritoneum of mice, it has been shown that the target/nontarget radioactivity ratios may be significantly improved with respect to the conventional procedures through the use of this approach.

Animals↗

PubMed1985

A simple in vitro method of screening panels of monoclonal antibodies for tumor binding.

We have developed a simple in vitro method of evaluating the relative binding properties of anti-tumor antibodies to human tumor and normal tissues. Cryopreserved surgical explants of tissues as 1 mm cubes are incubated in microtiter plate wells containing media and radiolabeled antibody. We show that the accumulation of antibody in tumor tissue is a specific process which may be reduced by preincubation with saturating levels of unlabeled specific antibody. Evaluation of 7 anti-breast and 4 anti-colorectal tumor antibodies against their respective tumor tissues showed good reproducibility of repeat measurements and up to a 100-fold difference in accumulation among different antibodies to the same tissue. Equivalent results were obtained with the same tissues employed fresh and after cryopreservation. Because of the simplicity of the assay, panels of antibodies may be screened against the large numbers of tumor and normal tissues required to identify superior antibodies for human trials.

Acid Phosphatase↗

PubMed1985

Biological similarities of rat fibroblast interferon to human and mouse alpha interferons.

High titres of rat interferon (IFN) can be produced by rat embryo fibroblast (CD) cells after treatment with Newcastle disease virus. This CD IFN was characterized by SDS-PAGE, and was found to contain three species at 30K to 33K, 25K to 27K and 17K to 22K mol. wt. Antibody affinity chromatography revealed that 95% of the CD IFN bound to an anti-human leukocyte IFN antibody column, 34% to an anti-mouse L cell IFN antibody column and none to an anti-human fibroblast IFN antibody column. The IFN that bound to the anti-human leukocyte IFN antibody column contained all three molecular weight species of IFN. However, the material bound to the anti-mouse L cell IFN antibody column only showed IFN activity of the 30K and 20K species. Examination of the heterologous antiviral activity of the unseparated CD IFN and of the IFN separated by antibody affinity chromatography revealed the same patterns of activity: 35 to 50% of homologous activity on guinea-pig cells, 10 to 20% on mouse cells, 2 to 4% on human cells and none on bovine cells. The data suggest that a major portion of this rat fibroblast IFN is related to alpha IFNs produced by other species.

Animals↗

PubMed1985

Pharmacokinetics of an indium-111-labeled monoclonal antibody in cancer patients.

We have evaluated the pharmacokinetics in patients of a monoclonal antibody (19-9) F(ab')2 fragment coupled with DTPA and labeled with 111In. In addition to imaging and organ uptake determinations, serum and urine samples were analyzed to help determine the in vivo behavior of the label. Using a competitive binding assay, the immunoreactivity of the coupled fragment was found to be indistinguishable from that of the unmodified fragment. The absence of radiocolloids in the injectate was confirmed as was the in vivo stability of the attached DTPA groups. By a variety of techniques, we show that the only significant source of label instability was transcomplexation to circulating transferrin. About 9% per day of label exposed to transferrin (about 1-2% of the injected dose) dissociated with slight bone marrow accumulation. Following i.v. administration, serum activity levels fell rapidly (T 1/2 alpha 2 hr, T 1/2 beta 19 hr). Whole-body clearance of the label was slow (T 1/2 160 hr) and may be attributed entirely to urinary excretion (0.26% of the injected dose per hour). Organ accumulation was greatest in the liver and persisted after rapidly attaining high values (20% of the injected dose). A total of 14 cancer patients were studied, nine with identifiable sites of metastatic disease from colorectal [8], pancreatic [2], ovarian [3], or small cell lung [1] primaries. Eight of the 12 sites of documented tumor were visualized by external imaging (67%) most distinctly at 48-72 hr postadministration.

Adult↗

PubMed1984

Production and partial purification of rat fibroblast-derived interferon induced in a newly established cell line.

Interferon (IFN) production induced by either Newcastle disease virus (NDV) or Sendai virus was compared in 10 different rat cell lines. Although there was variation in the IFN titers produced, NDV proved to be the best inducer in each cell line with optimum IFN yields occurring with a multiplicity of infection (MOI) of 1.0. A new continuous rat fibroblast cell line (CD) produced high titers of IFN similar to those reported for other high producers; while Ratec cells were shown to be the most sensitive to the antiviral activity of rat IFN. Partial purification and characterization of IFN produced in CD cells was accomplished by column chromatography. Four sorbents with varying modes of action for binding the IFN (Affi-Gel 202, Poly(U)-Sepharose 4B, CM-Sepharose CL-6B, and Phenyl-Sepharose CL-4B) were compared. The Phenyl-Sepharose CL-4B matrix proved to be the most successful for purification of rat IFN; one passage through this column, increased the specific activity more than 100-fold, with a concomitant recovery of 90%-95% biologic activity. The binding characteristics of rat IFN on each of the column matrices, however, demonstrated differences between the physicochemical nature of CD rat IFN and murine and hamster IFNs.

Animals↗

PubMed1983

Production, screening and characterization of a monoclonal antibody to murine interferon-beta.

A hybrid murine myeloma (2-13F5) secreting a monoclonal antibody that specifically bound and neutralized murine interferon beta has been isolated. Affinity chromatography with immobilized 2-13F5 monoclonal antibody of murine IFN (containing both IFN-alpha and IFN-beta) separated an IFN-beta preparation that demonstrated one band with Coomassie Brilliant Blue staining of SDS-PAGE at a molecular weight of 35000 and a specific activity of 4.3 x 10(8) units/mg of protein. This monoclonal antibody neither bound nor neutralized murine IFN-alpha. In addition, it bound only 87% of the interferon demonstrating a molecular weight of 35K. Possible explanations of this partial binding are discussed.

Animals↗

PubMed1982

Chemical modification of mouse interferons.

Mouse interferon (MuIFN) preparations containing both the alpha and beta species were treated with chemical modifying reagents specific for lysine, cysteine and tryptophan residues. The purpose was to ascertain whether reagents which modify specific amino acid residues distinguished MuIFN-alpha from MuIFN-beta, and if biologic properties could be correlated with specific amino acid residues. MuIFN species were characterized by their activity on homologous and heterologous cells and by antibody neutralization. Modification of lysine residues with increasing concentrations of fluorescamine resulted in a concomitant loss of biologic and antigenic activities of both MuIFN species. Modification of cysteine residues with 5,5'-dithio-bis (2-nitrobenzoic acid) showed an enhancement of antiviral activity of MuIFN-alpha but a gradual decrease in all activities of MuIFN-beta. Modification of tryptophan residues with 2-methoxy-5-nitrobenzyl bromide enhanced somewhat MuIFN-alpha activity, but resulted in the loss of MuIFN-beta activity. These results show that amino-modifying reagents rendered both major species of MuIFN inactive; however, they can be distinguished by reagents which affect cysteine and tryptophan residues. The fact that biologic activity is accompanied by the loss of antigenicity implies that the biologic and antigenic sites may be the same or closely associated. Chemical modification of interferons may provide a useful approach for relating the properties of interferons to their primary structure.

Amino Acid Sequence↗

PubMed1982

Allophycocyanin I and the 95 Kilodalton Polypeptide : The Bridge between Phycobilisomes and Membranes.

Allophycocyanin was isolated from dissociated phycobilisomes from Nostoc sp. and was separated into allophycocyanin I, II, III, and B as described elsewhere. If the separation of the proteins following phycobilisome isolation is done in the presence of the protease inhibitor, phenylmethylsulfonylfluoride, associated with allophycocyanin I are two colored polypeptides of 95 kilodalton (kD) and 80 kD, belonging to the class of Group I polypeptides as defined by Tandeau de Marsac and Cohen-Bazire (Proc Natl Acad Sci USA 1977 74: 1635-1639). Allophycocyanin I has a fluorescence maximum of 680 nanometers as do intact phycobilisomes and has thus been suggested to be the final emitter of excitation energy in phycobilisomes. Thylakoid membranes washed in low ionic strength buffer containing phenylmethylsulfonylfluoride lose all biliproteins, but retain the 95 kD and 80 kD polypeptides. As suggested by Tandeau de Marsac and Cohen-Bazire, these are likely to be the polypeptides involved in binding the phycobilisome to the membrane. As these polypeptides are isolated with allophycocyanin I, structural evidence is provided for placing allophycocyanin I as the bridge between the phycobilisome and the membrane. These Group I polypeptides and the 29 kD polypeptide (involved in rod attachment to the APC core) are particularly susceptible to proteolytic breakdown. It is thought that in vivo the active protease may be selectively attacking these polypeptides to detach the phycobilisome from the membrane and release the phycoerythrin and phycocyanin containing rods from the allophycocyanin core for greater susceptibility of the biliproteins to protease attack.

Journal Article↗

PubMed1980

Chlorophyll-Protein Complexes of the Cyanophyte, Nostoc sp.

Four chlorophyll-protein complexes have been resolved from the cyanophyte, Nostoc sp., by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis at 4 C. Complexes solubilized by SDS from Spinacia oleracea were run for comparison. As has been well documented, the P700-chlorophyll a-protein complex from the higher plant and blue-green algal samples are similar, and the light-harvesting pigment protein complex is present only in the former. Most noteworthy are two closely migrating chlorophyll proteins in Nostoc sp. which have approximately the same mobility as a single chlorophyll-protein band resolvable from spinach. The absorption maximum of the complex from spinach is at 667 nanometers, and those of the two complexes from Nostoc sp. are at 667 and 669 nanometers; the fluorescence emission maximum at -196 C is at 685 nanometers, and the 735 nanometer fluorescence peak, characteristic of the P700-chlorophyll a-protein complex, is absent. The apoproteins of these new complexes from Nostoc sp. and spinach are in the kilodalton range. It appears that at least one of these two chlorophyll-protein complexes from Nostoc sp. compares with those recently described by others from higher plants and green algae as likely photosystem II complexes, perhaps containing P680, although no photochemical data are yet available.

Journal Article↗

PubMedDate not supplied

Recombinant metallothionein-conjugated streptavidin labeled with 188Re and 99mTc.

Consideration is now being given to the use of avidin (or streptavidin) and biotin for radiotherapy of tumor. Accordingly, the goal of this study was to radiolabel a mouse metallothionein-streptavidin fusion protein with 188Re and to compare its properties to those of the same fusion protein radiolabeled with 99mTc. A recombinant metallothionein-streptavidin fusion protein was radiolabeled by transchelation with 99mTc- and 188Re-glucoheptonate. Labeling efficiency, which was not optimized for either radionuclide, was approximately 60% for 99mTc and 20% for 188Re. Radiochemical purity was demonstrated by size exclusion HPLC both by nearly quantitative shifts of the 188Re label to higher molecular weight upon the addition of biotinylated antibody and by the absence of a shift with biotinsaturated 188Re-metallothionein-streptavidin. Stability of the labels in 37 degrees C serum was evaluated by comparing the HPLC radiochromatograms of serum samples both before and after the addition of biotinylated antibody. The 188Re label behaved like 99mTc in that the same peaks were evident, including one prominent peak due to labeled cysteine. Recoveries during HPLC analysis of serum samples showed that oxidation rates to perrhenate and pertechnetate were identical. However, instability to cysteine challenge was greater for 188Re; for example, the loss of label to cysteine after 24 h under one set of conditions was 41% for 188Re and 22% with 99mTc. Analysis by HPLC of liver and kidney homogenates from mice administered the labeled antibodies were qualitatively and, in large measure, quantitatively independent of label. Biodistributions at 5 h in normal mice were statistically identical between the two labels in blood and in most tissues. In conclusion, streptavidin may be radiolabeled with radiorhenium using recombinant mouse metallothionein as a bifunctional chelator, and under one set of labeling conditions at least, 188Re showed similar in vitro and in vivo behavior to that of 99mTc labeled to the same fusion protein.

Animals↗

PubMedDate not supplied

Pretargeting with amplification using polymeric peptide nucleic acid.

One goal of this investigation was to develop a polymer conjugated with multiple copies of peptide nucleic acid (PNA) and with pharmacokinetic properties suitable for applications in vivo. The second goal was to establish whether the multiple copies of PNA on the polymer could be targeted by hybridization in vitro and in vivo with (99m)Tc-labeled complementary PNA (cPNA). If successful, this approach could then be considered in further investigations as an alternative to existing pretargeting approaches because of the potential for signal amplification in the target. A 80 KDa poly(methyl vinyl ether-alt-maleic acid) (PA) polymer was conjugated with multiple copies of PNA and with multiple copies of poly(ethylene glycol) (PEG) by reacting the NHS derivative of PA with the amine derivatives of PNA and PEG. Using (99m)Tc-MAG(3)-cPNA, targeting of PNA-PA-PEG was studied in vitro and in vivo in inflammation and tumor mouse models, in both cases relying upon nonspecific diffusion for localization. In addition, cPNA-avidin was considered as a clearing agent with biotinylated PNA-PA-PEG. About 80 PNAs could be conjugated to PA provided that about 200 PEGs were also conjugated to raise the aqueous solubility of the PNA-PA-PEG polymer lowered by the addition of the PNAs. About 70% of the PNAs on this polymer in vitro either in solution or attached to beads could be successfully targeted with (99m)Tc-cPNA. In both the inflammation and tumor mouse models, between 35 and 60% of these PNAs could be targeted in the lesions. The advantage of amplification was evident when less favorable results were obtained with PNA-PA-PEG conjugated with only six PNAs. We conclude that amplification can be achieved in vivo using polymers of PNA followed by radiolabeled complementary PNA and that the application of pretargeting using polymers of PNA for amplification can improve localization.

Animals↗

PubMedDate not supplied

Evidence of antisense tumor targeting in mice.

Even though increased accumulations of radiolabeled antisense DNAs compared to control DNAs are becoming a routine observation in cultured tumor cells, trustworthy evidence of tumor targeting in vivo by an antisense mechanism remains elusive. The goal of this study was to obtain convincing evidence of antisense tumor targeting in nude mice by using two different tumors and both intratumoral (i.t.) and intravenous (i.v.) administration of radiolabeled antisense and control sense DNAs. Both the MDR++ cell line KB-G2 and its parent MDR+ cell line KB-31 were used in this study. The antisense (AS) DNA was directed against the AUG start codon of the MDR1 mRNA and, along with the sense (S) control DNA, was a uniform phosphorothioate administered naked. In previous cell culture studies from our laboratories, the accumulation of this AS DNA was strikingly high in KB-G2 cells and only average in KB-31 cells, a fact we attribute to the 1000-fold higher expression by RT-PCR of MDR1 mRNA in the former cell line. In this study, both DNAs were radiolabeled with (99m)Tc via MAG3 and administered i.t. or i.v. at 1 microg (100 microCi) per animal 24 h prior to sacrifice and dissection in mice bearing thigh tumors of about 1 g. Following i.t. administration, no statistically significant differences (Student's t test, p < 0.05, N = 4) between the AS and S DNA biodistributions in normal tissues were observed except in the KB-G2 mice in which muscle levels were lower for the S control. In contrast, tumor levels in the KB-G2 animals were significantly higher for the AS DNA vs S DNA (14.7 vs 8.5% ID/g) while this difference (8.6 vs 4.3% ID/g) was insignificant in the KB-31 animals. The whole body images obtained just prior to sacrifice clearly show improved targeting of AS DNA vs S DNA in the KB-G2 but not the KB-31 animals. Calculations based on these results show that about 60 000 AS DNAs accumulated specifically (i.e. AS DNA - S DNA) per KB-G2 tumor cell following i.t. administration. When administered i.v. rather than i.t., higher tumor levels in KB-G2 animals compared to KB-31 were not observed, most likely because of the lower dosage reaching the tumors. When the KB-G2 and KB-31 results are combined, no statistically significant differences between the AS and S DNA biodistributions in normal tissues were observed except in blood in which S DNA levels were higher and in spleen in which they were lower. In contrast, tumor levels were significantly higher for the AS DNA vs S DNA (0.100 vs 0.063% ID/g). Calculations based on these results show that about 400 AS DNAs accumulated specifically per tumor cell following i.v. administration. Therefore evidence for tumor targeting in vivo by an antisense mechanism has been obtained in that statistically higher tumor accumulations of the (99m)Tc-AS DNA were observed compared to the control (99m)Tc-S DNA both following i.t. and i.v. administrations. The successful localization of AS DNA in tumor demonstrates that in vivo AS targeting of tumor is feasible although improvements in tumor delivery and normal tissue clearance are needed for practical antisense imaging.

Animals↗