Biomedical subjects

R M Sharkey

Publications and source records attributed to R M Sharkey.

138 records · Page 8Linked to original sources

PubMed1977

The prognostic significance of carcinoembryonic antigen in the plasma and tumors of patients with endometrial adenocarcinoma.

Carcinoembryonic antigen (CEA) levels in plasma and the immunocytochemical detection of tumor CEA were studied in patients with endometrial adenocarcinoma treated at the University of Kentucky Medical Center from 1973 to 1976. The incidence of CEA elevation in a group of 60 patients varied directly with uterine size, histologic differentiation, and stage of disease. Immunoperoxidase staining for CEA was performed on 42 specimens, and four were positive, indicating a tissue concentration of CEA of at least 5 microng per gram. Following operation, CEA levels returned to normal within eight weeks in all but two patients, both of whom were later shown to have persistent or recurrent cancer. These data suggest that serial plasma CEA determinations may be useful in predicting occult recurrence of endometrial cancer in patients in whom the plasma or tumor initially contains elevated concentrations of this antigen.

Adenocarcinoma↗

PubMed1977

Localization by immunoperoxidase and estimation by radioimmunoassay of carcinoembryonic antigen in colonic polyps.

A 3-layer immunoperoxidase technique was used to demonstrate carcinoembryonic antigen (CEA) in colonic polyps from patients with or without previous or concurrent malignancy. CEA was demonstrated in a higher percentage of the polyps received as fresh specimens that were rapidly frozen and fixed in ethanol, than in formalin-fixed, paraffin-embedded sections. Tissue CEA content of both colonic carcinomas and polyps was determined by radioimmunoassay, and it was found that benign colonic tumours had levels of tissue CEA comparable to colonic cancer, indicating that CEA concentration in a tumour does not reflect its grade of malignancy. In fact, in one case in which both colonic cancer and polyps were removed, the polyps had the higher quantities of tissue CEA. Further, tissue CEA concentration of a polyp was not dependent on its size or location. Studying the titres of circulating CEA in these patients revealed an elevation of plasma CEA in one-third of the patients with only colonic polyps, whilst the patients with cancer all had increased titres.

Carcinoembryonic Antigen↗

PubMed1976

Carcinoembryonic antigen in histopathology: immunoperoxidase staining of conventional tissue sections.

A triple-bridge, indirect peroxidase-antiperoxidase method for demonstrating carcinoembryonic antigen (CEA) in frozen, ethanol-fixed or formalin-fixed, paraffin-embedded specimens was evaluated. Examination of 359 tissue specimens--234 malignant tumors, 37 benign neoplasms, 41 nonneoplastic diseased tissues, and 47 normal specimens--showed that CEA could usually be demonstrated in a group of cancers. We could detect CEA in carcinomas of the stomach, colon, rectum, pancreas, lung, and cervix. However, malignant tumors of the breast, prostate, kidney, larynx, brain, lymphoreticular system, soft tissues, and skin proved negative for CEA by the immunoperoxidase test. CEA could be detected in ethanol- or formalin-fixed sections. The only nonmalignant specimens showing CEA staining were a few benign tumors, the mucosae of some cases of colitis, and the resection margins of 2 cases of colon cancer; however, these were commonly very weak reactions. Measurement of tumor CEA content by radioimmunoassay revealed two causes for this relative specificity of the immunoperoxidase test for CEA:1) a quantitative difference existed in tissue CEA among the various specimens, and 2) the threshold for CEA staining in malignant specimens was usually above that in nonmalignant specimens. An analysis of the formalin-paraffin-treated sections showed that immunoperoxidase-tested CEA positivity reflected CEA levels in tissue of at least 3.0-5.0 mug/g; this permitted retrospective estimates of minimal tissue CEA concentrations in older histopathologic specimens by the immunoperoxidase reaction method. Formalin-paraffin-treated sections as old as 10 years still had demonstrable CEA. Although tumor CEA concentration correlated well with immunoperoxidase staining for CEA, plasma CEA titer did not necessarily reflect tumor CEA content. CEA positivity in primary and secondary tumors was strongly correlated; it was less strongly correlated with level of tumor differentiation.

Carcinoembryonic Antigen↗

PubMed1975

Detection of carcinoembryonic antigen in tissue sections by immunoperoxidase.

A triple-bridge, indirect, immunoperoxidase method for detecting and localizing carcinoembryonic antigen (CEA) in tissue sections is described. By this technique, a cell-surface localization of CEA in colonic carcinoma and ovarian mucinous cystadenocarcinoma cells could be visualized. In the case of the colonic cancer, both the tumor from the descending colon and a metastasis to the skin gave positive peroxidase reactions for CEA. This immunocytochemical method for demonstrating the presence of CEA functioned in both frozen, ethanol-fixed and formalin-fixed, paraffin-embedded tissues, thus making it applicable for use with tissue sections conventionally prepared for light microscopy.

Adenocarcinoma↗

PubMedDate not supplied

Localization of pancreatic cancer with radiolabeled monoclonal antibody PAM4.

Experimental animal studies were performed with (111)In-labeled PAM4 anti-MUC1 antibody along with (111)In-labeled control antibody. Tumor uptake of radiolabeled PAM4 was significantly higher than for the control antibody at all time points. When normalized to a blood dose of 1500 cGy as an estimate of myelotoxicity, (90)Y-labeled PAM4 would provide 5344 cGy to the tumor, whereas an equitoxic dose of (90)Y-labeled control antibody would provide only 862 cGy to the tumor. In addition to the animal studies, five patients with proven pancreatic cancer were administered either (131)I-PAM4 IgG (n=2) or 99mTc-PAM4 Fab' (n=3). Tumor targeting was observed in four out of five patients. By immunohistochemistry, PAM4 was non-reactive with tumor from the one patient not targeted. Dosimetry from the patients given (131)I-PAM4 predicted that tumors would receive 10-20 cGy/mCi with tumor/red marrow dose ratios ranging from 3 to 10. Based upon these results, we have established a phase-I (111)In-labeled PAM4 imaging and (90)Y-labeled PAM4 therapy trial.

Aged↗

PubMedDate not supplied

Experimental pretargeting studies of cancer with a humanized anti-CEA x murine anti-[In-DTPA] bispecific antibody construct and a (99m)Tc-/(188)Re-labeled peptide.

The aim of this study was to localize (99m)Tc and (188)Re radionuclides to tumors, using a bispecific antibody (bsMAb) in a two-step approach where the radionuclides are attached to novel peptides incorporating moieties recognized by one arm of the bsMAb. A chemically cross-linked human/murine bsMAb, hMN-14 x 734 (Fab' x Fab'), anti-carcinoembryonic antigen [CEA] x anti-indium-DTPA was prepared as a prelude to constructing a fully humanized bsMAb for future clinical application. N,N'-o-Phenylenedimaleimide was used to cross-link the Fab' fragments of the two antibodies at their hinge regions. This construct was shown to be >92% pure and fully reactive with CEA and a divalent (indium)DTPA-peptide. For pretargeting purposes, a peptide, IMP-192 [Ac-Lys(In-DTPA)-Tyr-Lys(In-DTPA)-Lys(TscG-Cys-)-NH(2) ¿TscG = 3-thiosemicarbazonylglyoxyl¿], with two indium-DTPAs and a chelate for selectively binding (99m)Tc or (188)Re, was synthesized. IMP-192 was formulated in a "single dose" kit and later radiolabeled with (99m)Tc (94-99%) at up to 1836 Ci/mmol and with (188)Re (97%) at 459-945 Ci/mmol of peptide. [(99m)Tc]IMP-192 was shown to be stable by extensive in vitro and in vivo testing and had no specific uptake in the tumor with minimal renal uptake. The biodistribution of the hMN-14 x murine 734 bsMAb was compared alone and in a pretargeting setting to a fully murine anti-CEA (F6) x 734 bsMAb that was reported previously [Gautherot, E., Bouhou, J., LeDoussal, J.-M., Manetti, C., Martin, M., Rouvier, E., and Barbet, J. (1997) Therapy for colon carcinoma xenografts with bispecific antibody-targeted, iodine-131-labeled bivalent hapten. Cancer 80 (Suppl.), 2618-2623]. Both bsMAbs maintained their integrity and dual binding specificity in vivo, but the hMN-14 x m734 was cleared more rapidly from the blood. This coincided with an increased uptake of the hMN-14 x m734 bsMAb in the liver and spleen, suggesting an active reticuloendothelial cell recognition mechanism of this mixed species construct in naive mice. Animals bearing GW-39 human colonic cancer xenografts were injected with bsMAb (15 microg) and after allowing 24 or 72 h for the bsMAb constructs to clear from the blood (hMN-14 and murine F6 x 734, respectively), [(188)Re]IMP-192 (7 microCi) or [(99m)Tc]IMP-192 (10 microCi) was injected at a bsMAb:peptide ratio of 10:1. Tumor uptake of [(99m)Tc] or [(188)Re]IMP-192 was 12.6 +/- 5.2 and 16.9 +/- 5.5% ID/g at 3 h postinjection, respectively. Tumor/nontumor ratios were between 5.6 and 23 to 1 for every major organ, indicating that early imaging with (99m)Tc will be possible. Radiation absorbed doses showed a 4.8-, 7.2-, and a 12.6 to 1.0 tumor to blood, kidney, and liver ratios when (188)Re was used. Although this new bsMAb pretargeting approach requires further optimization, it already shows very promising targeting results for both radioimmunodetection and radioimmunotherapy of colorectal cancer.

Animals↗

PubMedDate not supplied

Conjugation of phenyl isothiocyanate derivatives of carborane to antitumor antibody and in vivo localization of conjugates in nude mice.

A systematic study of the conjugation of 1-(p-isothiocyanatophenyl)-1,2-dicarba-closo-[2-3H]dodeca borane(12), 3H-1, and 7-(p-isothiocyanatophenyl)dodecahydro-7,8-dicarba-nido -[8-3H] undecaborate(1-)ion, 3H-2, to the murine monoclonal anti-CSAp antibody, Mu-9, was carried out to compare charged and uncharged boron cages in their effect upon antibody loading. Approximately one neutral cage and four of the anionic cages were successfully linked to antibody in two separate conjugates which were subsequently radioiodinated and evaluated in vivo. No significant loss of the antibody or its immunoreactivity was observed in either case. In nude mice bearing GW-39 tumor xenografts the conjugate containing the anionic carborane derivative showed a reduced tumor uptake although the tumor:non-tumor ratio was similar to that of the native antibody. The carborane cage in 2 was radiolabeled with 125I followed by attempts to purify and conjugate product 4 to a model goat IgG protein. This exploratory conjugation study was undertaken as a prelude to linking new conjugation reagents, which contain multiple anionic boron cages, to antitumor antibodies. The latter conjugates are required to maximize boron loading for the purpose of neutron-capture therapy.

Animals↗

PubMedDate not supplied

Technetium labeling of monoclonal antibodies with functionalized BATOs: 2. TcCl(DMG)3CPITC labeling of B72.3 and NP-4 whole antibodies and NP-4 F(ab')2.

BATO (boronic acid adduct of technetium dioximes) complexes, TcCl(dioxime)3BR, were prepared in which the boron substituent (R) was the protein-reactive 2-carboxy-4-phenyl isothiocyanate (CPITC). The 99Tc complexes, where the dioxime was either dimethylglyoxime (DMG) or cyclohexanedione dioxime (CDO), were prepared and characterized. The 99mTc complex TcCl(DMG)3CPITC was prepared from a freeze-dried kit and used to label B72.3 (anti-TAG.72) and NP-4 (anti-CEA) whole antibodies, and the NP-4 F(ab')2 fragment. SDS-PAGE electrophoresis indicated that the labeling reagent was strongly bound to antibody. The labeled antibodies displayed high binding to affinity columns and good tumor uptake in GW39 tumor-bearing mice.

Animals↗

PubMedDate not supplied

Pretargeting for cancer radioimmunotherapy with bispecific antibodies: role of the bispecific antibody's valency for the tumor target antigen.

The use of a divalent effector molecule improves bispecific antibody (bsMAb) pretargeting by enabling the cross-linking of monovalently bound bsMAb on the cell surface, thereby increasing the functional affinity of a bsMAb. In this work, it was determined if a bsMAb with divalency for the primary target antigen would improve bsMAb pretargeting of a divalent hapten. The pretargeting of a (99m)Tc-labeled divalent DTPA-peptide, IMP-192, using a bsMAb prepared by chemically coupling two Fab' fragments, one with monovalent specificity to the primary target antigen, carcinoembryonic antigen (CEA), and to indium-loaded DTPA [DTPA(In)], was compared to two other bsMAbs, both with divalency to CEA. One conjugate used the whole anti-CEA IgG, while the other used the anti-CEA F(ab')(2) fragment to make bsMAbs that had divalency to CEA, but with different molecular weights to affect their pharmacokinetic behavior. The rate of bsMAb blood clearance was a function of molecular weight (IgG x Fab' < F(ab')(2) x Fab' < Fab' x Fab' conjugate). The IgG x Fab' bsMAb conjugate had the highest uptake and longest retention in the tumor. However, when used for pretargeting, the F(ab')(2) x Fab' conjugate allowed for superior tumor accretion of the (99m)Tc-IMP-192 peptide, because its more rapid clearance from the blood enabled early intervention with the radiolabeled peptide when tumor uptake of the bsMAb was at its peak. Excellent peptide targeting was also seen with the Fab' x Fab' conjugate, albeit tumor uptake was lower than with the F(ab')(2) x Fab' conjugate. Because the IgG x Fab' bsMAb cleared from the blood so slowly, when the peptide was given at the time of its maximum tumor accretion, the peptide was captured predominantly by the bsMAb in the blood. Several strategies were explored to reduce the IgG x Fab' bsMAb remaining in the blood to take advantage of its 3-4-fold higher tumor accretion than the other bsMAb conjugates. A number of agents were tested, including those that could clear the bsMAb from the blood (e.g., galactosylated or nongalactosylated anti-id antibody) and those that could block the anti-DTPA(In) binding arm [e.g., DTPA(In), divalent-DTPA(In) peptide, and DTPA coupled to bovine serum albumin (BSA) or IgG]. When clearing agents were given 65 h after the IgG x Fab' conjugate (time of maximum tumor accretion for this bsMAb), (99m)Tc-IMP-192 levels in the blood were significantly reduced, but a majority of the peptide localized in the liver. Increasing the interval between the clearing agent and the time the peptide was given to allow for further processing of the bsMAb-clearing agent complex did not improve targeting. At the dose and level of substitution tested, galacosylated BSA-DTPA(In) was cleared too quickly to be an effective blocking agent, but BSA- and IgG-DTPA(In) conjugates were able to reduce the uptake of the (99m)Tc-IMP-192 in the blood and liver. Tumor/nontumor ratios compared favorably for the radiolabeled peptide using the IgG x Fab'/blocking agent combination and the F(ab')(2) x Fab' (no clearing/blocking agent), and peptide uptake 3 h after the blocking agent even exceeded that of the F(ab')(2) x Fab'. However, this higher level of peptide in the tumor was not sustained over 24 h, and actually decreased to levels lower than that seen with the F(ab')(2) x Fab' by this time. These results demonstrate that divalency of a bsMAb to its primary target antigen can lead to higher tumor accretion by a pretargeted divalent peptide, but that the pharmacokinetic behavior of the bsMAb also needs to be optimized to allow for its clearance from the blood. Otherwise, blocking agents will need to be developed to reduce unwanted peptide uptake in normal tissues.

Animals↗

PubMedDate not supplied

Development of a streptavidin-anti-carcinoembryonic antigen antibody, radiolabeled biotin pretargeting method for radioimmunotherapy of colorectal cancer. Studies in a human colon cancer xenograft model.

Pretargeting methodologies can produce high tumor:blood ratios, but their role in cancer radioimmunotherapy (RAIT) is uncertain. A pretargeting method was developed using a streptavidin (StAv) conjugate of MN-14 IgG, an anti-carcinoembryonic antigen (CEA) murine monoclonal antibody (mab) as the primary targeting agent, an anti-idiotype antibody (WI2 IgG) as a clearing agent, and DTPA- or DOTA-conjugated biotin as the radiolabeled targeting agent. A variety of reagents and conditions were examined to optimize this method. At 3 h, 111In-DTPA-peptide-biotin tumor uptake was 3.9 +/- 0.8% per gram and tumor:blood ratios were > 11:1. By 24 h, this ratio was 178:1, but tumor accretion declined in accordance with the gradual loss of StAv-MN-14 from the tumor. Tissue retention was highest in the liver and kidneys, but their tumor:organ ratios were > 2:1. Dosimetry predicted that radiolabeled MN-14 alone would deliver higher tumor doses than this pretargeting method. Increasing the specific activity and using DOTA-biotin in place of DTPA increased tumor uptake nearly 2-fold, but analysis of StAv-MN-14's biotin-binding capacity indicated over 90% of the initial biotin-binding sites were blocked within 24 h. Animals fed a biotin-deficient diet had 2-fold higher 111In-DOTA-biotin uptake in the tumor, but higher uptake also was observed in all normal tissues. Although exceptionally adept at achieving high tumor:blood ratios rapidly, the tumor uptake of radiolabeled biotin with this pretargeting method is significantly (p < 0.0001) lower than that with a radiolabeled antibody. Endogenous biotin and enhanced liver and kidney uptake may limit the application of this method to RAIT, especially when evaluating the method in animals, but with strategies to overcome these limitations, this pretargeting method could be an effective therapeutic alternative.

Animals↗

PubMedDate not supplied

Development of a streptavidin-anti-carcinoembryonic antigen antibody, radiolabeled biotin pretargeting method for radioimmunotherapy of colorectal cancer. Reagent development.

With pretargeting, radioisotope delivery to tumor is decoupled from the long antibody localization process, and this can increase tumor:blood ratios dramatically. Several reagents were prepared for each step of a "two-step" pretargeting method, and their properties were investigated. For pretargeting tumor, streptavidin-monoclonal antibody (StAv-mab) conjugates were prepared by cross-linking sulfo-SMCC-derivatized streptavidin to a free thiol (SH) group on MN-14 [a high-affinity anti-carcinoembryonic antigen (CEA) mab]. Thiolated mabs were generated either by reaction of 2-iminothiolane (2-IT) with mab lysine residues or by reduction of mab disulfide bonds with (2-mercaptoethyl)amine (MEA). Both procedures gave protein-protein conjugates isolated in relatively low yields (20-25%) after preparative size-exclusion (SE) chromatography purification with conservative peak collection. Both StAv-MN-14 conjugates retained their ability to bind to CEA, to an anti-idiotypic antibody to MN-14 (WI2), and to biotin, as demonstrated by SE-HPLC. Two clearing agents, WI2 mab and a biotin-human serum albumin (biotin-HSA) conjugate, were developed to remove excess circulating StAv-MN-14 conjugates in animals. Both clearing proteins were also modified with galactose residues, introduced using an activated thioimidate derivative, to produce clearing agents which would clear rapidly and clear primary mab rapidly. At least 14 galactose residues on WI2 were required to reduce blood levels to 5.9 +/- 0.7% ID/g in 1 h. Faster blood clearance (0.7 +/- 0.2% ID/g) was observed in 1 h using 44 galactose units per WI2. For the delivery of radioisotope to tumor, several biotinylated conjugates consisting of biotin, a linker, and a chelate were prepared. Conjugates showed good in vitro and in vivo stability when D-amino acid peptides were used as linkers, biotin-peptide-DOTA-indium-111 had a slightly longer blood circulation time (0.09 +/- 0.02% ID/g in 1 h) than biotin-peptide-DTPA-indium-111 (0.05 +/- 0.03% ID/g in 1 h) in nude mice. A longer circulation time with the neutral DOTA complex might allow higher tumor uptake.

Animals↗

PubMedDate not supplied

90Yttrium-labeled complementarity-determining-region-grafted monoclonal antibodies for radioimmunotherapy: radiolabeling and animal biodistribution studies.

90Yttrium-labeled monoclonal antibodies (mAbs) are likely to be important to radioimmunotherapy (RAIT) of a variety of cancers. The goal of this study was to select and evaluate a form of [90Y]mAb suitable for RAIT and determine conditions for high-yield, reproducible radiolabelings. 90Y-Labelings, at 2-40 mCi levels, of cdr-grafted versions of anti-B-cell lymphoma (hLL2) and anti-CEA (hIMMU-14) mAbs were optimized to >90% incorporations using the macrocyclic chelator DOTA as the metal carrier. In in vitro challenge assays, the stability of mAbs labeled with [90Y]DOTA was better than that of the corresponding [90Y]benzyl-DTPA conjugates. The retention of [90Y]DOTA-hLL2 on Raji tumor cells in vitro was similar to that of the same mAb labeled with [90Y]benzyl-DTPA and was about twice as much as with [125I]hLL2, indicating residualization of metalated mAb. Both [90Y]hLL2 conjugates, prepared using DOTA and Bz-DTPA, had similar maximum tolerated doses of 125 muCi in BALB/c mice and showed no discernible chelator-induced immune responses. Animal biodistribution studies in nude mice bearing Ramos human B-cell lymphoma xenografts revealed similar tumor and tissue uptake over a 10 day period, with the exception of bone uptake which was up to 50% lower for [88Y]DOTA-hLL2 compared to [88Y]Bz-DTPA-hLL2 at time points beyond 24 h. With [90Y]DOTA-hLL2 fragments, in vivo animal tumor dosimetries were inferior to those for the IgG, and kidney uptake was relatively high even with D-lysine administration. The ability of [111In]DOTA-hLL2 to accurately predict [90Y]DOTA-hLL2 biodistribution was established. These preclinical findings demonstrate that [90Y]DOTA-(CDR-grafted) mAbs are suitable for examination in clinical RAIT.

Animals↗