Unaltered brain levels of 1,N2-propanodeoxyguanosine adducts of trans-4-hydroxy-2-nonenal in Alzheimer's disease.

In recent years, an important role for the pathogenesis of Alzheimer's disease (AD) has been ascribed to oxidative stress. Trans-4-hydroxy-2-nonenal, a product of lipid peroxidation, forms stable adducts with a variety of nucleophilic substituents such as thiols or amino moieties. Here, we report the quantification of 1,N2-propanodeoxyguanosine adducts of trans-4-hydroxy-2-nonenal (HNE-dGp) using the specific and very sensitive method of 32P-postlabeling of deoxyguanosine adducts derived from nuclear DNA in neuron rich areas of the hippocampus, the parietal cortex, and the cerebellum of postmortem brains from patients with AD and age matched controls. Adduct levels were highest in the hippocampus, followed by the cerebellum and parietal cortex irrespective of the disease. Neither age, postmortem delay time, gender, nor the extent of neurofibrillary deposits affected tissue adduct levels in the brain areas examined. Although distinctively present in the human brain, the level of HNE-dGp adducts appears not to be useful as a biomarker for AD.

Detection of 1,N2-propanodeoxyguanosine adducts of trans-4-hydroxy-2-nonenal after gavage of trans-4-hydroxy-2-nonenal or induction of lipid peroxidation with carbon tetrachloride in F344 rats.

The 1,N2-propanodeoxyguanosine adducts of trans-4-hydroxy-2-nonenal (HNE-dGp-adducts) were quantitated in tissues of rats treated with trans-4-hydroxy-2-nonenal (HNE) or carbon tetrachloride, respectively, using a 32P-postlabeling method. The method development was based on chemically synthesized HNE-1,N2-propanodeoxyguanosine adduct standard, which was characterized by NMR and mass spectra. The adducts were enriched by Nuclease P1. They were subsequently reacted with gamma-32P-ATP to give the respective 3'-5'-bisphosphates, which were two-directionally separated on PEI-cellulose-TLC and quantitated by autoradiography. The labeling efficiency for the adduct standard was 27%, and the recovery of spiked amounts of adduct standard in the enzymatical procedure was about 80%. Internal standard was used to eliminate methodological variations. The determination of the limit of quantitation in DNA from rat tissues by spiking of HNE-dGp-adduct standard revealed a sensitivity of about 20 HNE-dGp-adducts/10(9) normal nucleotides. Background levels of HNE-dGp-adducts in tissues of rats including liver, kidney, lung, colon and forestomach were found in the range of 18-158 adducts/10(9) nucleotides with relatively high adduct levels in the liver and low adduct levels in kidney, lung and colon. These background levels were statistically significantly increased by the factor of 2 in liver, lung, colon and forestomach after induction of lipid peroxidation by carbon tetrachloride. The finding that background HNE-dGp-adduct levels may be in context with different metabolic activities of the tissues and the increase of HNE-dGp-adduct levels after application of carbon tetrachloride indicate that HNE-dGp-adducts are an endogenous lesion and that they are probably formed from radical initiated lipid peroxidation.

Development of a (32)P-postlabeling method for the detection of 1,N(2)-propanodeoxyguanosine adducts of trans-4-hydroxy-2-nonenal in vivo.

A (32)P-postlabeling method was developed for the sensitive detection of 1,N(2)-propanodeoxyguanosine adducts of the lipid peroxidation product trans-4-hydroxy-2-nonenal in vivo. The method development was based on the chemically synthesized HNE-1, N(2)-propanodeoxyguanosine adduct standard, which was characterized by NMR and mass spectra. The adducts were enriched by nuclease P1. They were subsequently reacted with [gamma-(32)P]ATP to give the respective 3'-5'-bisphosphates, which were two-directionally separated on PEI-cellulose TLC and quantitated by autoradiography. The medium labeling efficiency for the mixture of the two pairs of diastereomers was 27%, and the recovery of spiked amounts of adduct standard in the enzymatical procedure was about 80%. The method is applicable for the separation and quantitation of HNE-dGp-propano adducts in vivo. It was applied to DNA from colon and brain tissue of untreated Fischer 344 rats and humans. The determination of the limit of quantitation in DNA from rat colon by spiking of adduct standard revealed a sensitivity of <21 adducts/10(9) nucleotides. The analytical quantitation of 4-HNE-dGp-propano adducts resulted in adduct-levels per 10(9) normal nucleotides +/- the standard deviation of 223.32 +/- 79.84 in rat colon tissue, 90.37 +/- 11.94 in rat brain tissue, 378.44 +/- 52.42 in human colon tissue, and 185.15 +/- 6.48 in human brain tissue. The results clearly demonstrate the applicability of this method for the sensitive detection of endogenously formed 1,N(2)-propanodeoxyguanosine adducts of trans-4-hydroxy-2-nonenal, a specific marker for the lipid peroxidation process.

A method including edge effects for the estimation of radioimmunotherapy absorbed doses in the tumor xenograft model.

The temporal relationship of radiolabeled monoclonal antibody (Mab) uptake to tumor size in a nude mouse human colon cancer xenograft model (LS174T) was evaluated as an aid to developing a method for estimation of radioimmunotherapy absorbed dose. Tumors of heterogeneous size were treated with 4.4 MBq (120 microCi) of 90Y-labeled anti-Carcinoembryonic Antigen Mab (90Y-ZCE025). Regression analysis demonstrated an inverse log-log relationship of antibody uptake (%ID/g) to tumor mass in four time intervals investigated (N > 10 points/interval):12-24 h, 2-3 d, 5-7 d, and 10-14 d. Curves of predicted radionuclide concentration vs time were then constructed for a range of constant tumor sizes. Xenograft radiation dose was obtained by temporal integration of each curve and application of appropriate dose estimation formulas. For each assumed tumor mass, an edge correction for loss of beta energy outside the target volume was applied assuming a spherical tumor shape. Estimated average absorbed doses were found to vary only from 13.8-10.3 Gy for a 20-fold change in tumor sizes (0.1-2.0 g, respectively). Such constancy of dose may explain xenograft stasis observed by our group in earlier experiments at this level of administered 90Y activity.

Comparison of radioimmunotherapy and external beam radiotherapy in colon cancer xenografts.

Radioimmunotherapy and external beam radiotherapy were compared in a nude mouse human colon cancer model. Radioimmunotherapy was delivered by intraperitoneal injection of 90Y-labeled anticarcinoembryonic antigen monoclonal antibody (anti-CEA MAB). Single fraction external beam radiotherapy was delivered using a 60Co teletherapy unit. Control groups received saline, unlabeled anti-CEA monoclonal antibody and labeled nonspecific monoclonal antibody. Subcutaneous CEA-expressing LS174T human colon carcinoma tumors were measured over time. Tumor growth suppression was expressed as delay to reach 2g compared to saline controls. Unlabeled anti-CEA monoclonal antibody and labeled nonspecific monoclonal antibody had no effect. External beam radiotherapy of 300, 600, 1000 and 2000 cGy produced growth delays of 3, 12, 17, and 22 days, respectively. Radioimmunotherapy with 120 microCi, 175 microCi, and 225 microCi resulted in growth delays of 20, 34, and 36 days. Estimated absorbed tumor dose was 1750 cGy in the 120 microCi group. Similar comparisons were done with the more radioresistant WiDr human colon carcinoma cell line. External beam radiotherapy doses of 400, 800, 1200, and 1600 cGy resulted in growth delays of 6, 21, 36 and 48 days, respectively. Radioimmunotherapy of 120 microCi and 175 microCi resulted in growth delays of 9 and 19 days, respectively. The 120 microCi dose delivered an estimated absorbed tumor dose of 1080 cGy to WiDr tumors. In summary, for the radiosensitive LS174T line, radioimmunotherapy produced biologic effects that were comparable to a similar dose of single fraction external beam radiotherapy. For the more radioresistant WiDr tumor, radioimmunotherapy produced a biologic effect which was less than a similar dose of single fraction external beam radiotherapy. These studies suggest that a tumor's response to radioimmunotherapy relative to that of external beam radiotherapy is, in part, dependent on tumor radiosensitivity and repair capacity.

CD69, an early activation antigen on lymphocytes, is constitutively expressed by human epidermal Langerhans cells.

When screening skin cryosections with a panel of monoclonal antibodies (MoAb), we found that the anti-CD69 MoAb Leu-23 reacted with a subpopulation of epidermal dendritic cells, presumably Langerhans cells (LC). The staining intensity was enhanced by gentle trypsin pretreatment of the sections. Flow cytometric analysis of LC-enriched epidermal cells (EC) revealed that nearly all CD1a-bearing LC display anti-CD69 reactivity when tested briefly after termination of the enrichment procedure. Immunoprecipitation experiments showed that isolated LC specifically express a disulphide-linked dimer composed of 26/30kDa subunits that therefore slightly differs from the 28/32kDa CD69 complex described on activated T or natural killer (NK) cells. This difference is probably due to a different post-translational glycosylation pattern as evidenced by Endoglycosidase-F treatment of the immunoprecipitate disclosing the 24-kDa core protein of CD69. When freshly isolated LC-enriched EC were kept in culture, anti-CD69 reactivity gradually decreased but the addition of IFN-gamma to the culture medium sustained the CD69 expression on LC in vitro. These results strongly suggest that resident but not LC recovered from EC cultures bear CD69 moieties. It remains to be seen whether the expression of this antigen can be linked to (a) particular functional property (ies) of intraepidermal LC.

Carcinoembryonic antigen expression of resurgent human colon carcinoma after treatment with therapeutic doses of 90Y-alpha-carcinoembryonic antigen monoclonal antibody.

We have previously shown that the colon carcinoma (LS174T) xenografts that emerged shortly after radioimmunotherapy with 90Y-labeled anti-CEA monoclonal antibody (MAb) ZCE025 lacked significant expression of CEA in comparison with the untreated tumors. The present study was designed to establish if the immunophenotype of the treated tumors was the result of CEA specific therapy and if the effect was permanent. Athymic mice bearing LS174T tumors were treated either with 120 mu Ci of 90Y-ZCE025, an equal dose of 90Y-96.5 (nonspecific MAb), or received no treatment. When the treated tumors grew to approximately 1.5 cm in diameter (6 weeks after therapy), they were resected and aliquoted to be transplanted to other mice, plated in tissue culture, fixed in formalin, and homogenized for CEA quantitation. The procedure was repeated 3 times (a total of 4 months after treatment). The CEA content was evaluated 2 and 6 weeks after therapy and when the tumors were transplanted. We confirmed a 4-fold decrease of CEA in the resurgent tumors 6 weeks after specific 90Y-ZCE025 therapy, which was twice the decrease experienced by the tumors treated with nonspecific 90Y-96.5, indicating substantial and specific killing of CEA-expressing cells. The CEA content slowly but progressively increased with each new pass of the tumor in the mice, reaching approximately one-half the value of the controls at the end of the study. The resurgent tumors were also studied by immunohistochemistry with MAbs detecting different epitopes of CEA, keratin, TAG-72, and epithelial membrane antigen to evaluate possible additional immunophenotypic changes induced by radioimmunotherapy. Only the expression of TAG-72 (recognized by MAb B72.3) increased immediately after therapy, but it returned to the original levels by the end of the study. These results suggest that: (a) specific radioimmunotherapy with 90Y-ZCE025 selectively kills cells that express higher levels of CEA; (b) the immunophenotype of the surviving fraction of the tumor appears to slowly revert to its original form; and (c) other tumor markers unrelated to CEA can also be affected. These observations have important implications for the design of radioimmunotherapy trials.

Interferon enhancement of radioimmunotherapy for colon carcinoma.

Recombinant human gamma-interferon (IFN-gamma) has recently been shown to enhance localization of radiolabeled monoclonal antibodies (MAb) to human colon carcinoma xenografts in athymic mice. The present study investigates the ability of gamma-interferon to enhance radioimmunotherapy of a low carcinoembryonic antigen-expressing human colon cancer (WiDr) in athymic mice. Growth curve analysis, antibody localization, and dose estimation studies were performed. A significant tumor growth delay, measured as the time to reach 1.0 g, was noted for animals receiving specific anti-carcinoembryonic antigen 90Y-MAb (ZCE025, 120 microCi) plus IFN-gamma (61.8 days) as compared to animals that received specific 90Y-MAb with phosphate-buffered saline (34.9 days; P less than 0.005). IFN-gamma (100,000 units) was given i.p. every 8 h for 2 days before and 4 days after 90Y-MAb therapy. The time required to reach 1.0 g for animals treated with nonspecific 90Y-MAb (ZME018) was significantly less either with (38.3 days) or without (34.4 days) IFN-gamma. The difference was more apparent when compared to animals receiving IFN-gamma alone (30.0 days) or phosphate-buffered saline alone (28.9 days; P less than 0.001). Increased antibody localization in the tumors of animals treated with IFN-gamma plus specific 90Y-MAb (43.2% injected dose/g) was seen in comparison to animals treated with specific 90Y-MAb without IFN-gamma (18.2% injected dose/g). The estimate of radiation dose delivered to the tumors, based on biodistribution data over time, revealed significantly higher levels in animals treated with specific 90Y-MAb with IFN-gamma (2477 cGy) compared to animals treated without IFN-gamma (1217 cGy). These results provide support for the use of gamma-interferon as an immunomodulating agent prior to radioimmunotherapy.

Targeting and therapy of human glioma xenografts in vivo using radiolabeled antibodies.

Radiolabeled antibodies provide a potential basis for selective radiotherapy of human gliomas. Monoclonal P96.5, a mouse IgG2a immunoglobulin, defines an epitope of a human melanoma cell surface protein and specifically binds the U-251 human glioma as measured by immunoperoxidase histochemistry. 111In-radiolabeled P96.5 specifically targets the U-251 human glioma xenograft and yields 87.0 microCuries (uCi) of tumor activity per gram per 100 uCi injected activity compared to 4.5 uCi following administration of radiolabeled irrelevant monoclonal antibody. Calculations of targeting ratios demonstrate deposited dose to be 11.6 times greater with radiolabeled P96.5 administration compared to irrelevant monoclonal antibody. Tumor dose found in normal organs is less than 20% of the tumor dose, further supporting specific targeting of the human glioma xenograft by this antibody. Monoclonal antibodies QCI054 and ZME018, which define a tumor-associated and a second melanoma-associated antigen, respectively, demonstrate positive immunoperoxidase staining of the tumor, but comparatively decreased targeting. To test the therapeutic potential of 90Y-radiolabeled P96.5, QCI054, and ZME018, tumors and normal sites were implanted with miniature thermoluminescent dosimeters (TLD). Average absorbed doses of 3770 +/- 445 (mean +/- SEM), 2043 +/- 134, and 645 +/- 48 cGy in tumor, 353 +/- 41, 243 +/- 22, and 222 +/- 13 cGy in a contralateral control intramuscular site, 980 +/- 127, 815 +/- 41, and 651 +/- 63 cGy in liver, and 275 +/- 14, 263 +/- 11, and 256 +/- 18 cGy in total body were observed 7 days following administration of 100 uCi 90Y-radiolabeled P96.5, QCI054, and ZME018, respectively. To test the therapeutic potential, tumor-bearing nude mice were given intracardiac injections of either buffer or 90Y-radiolabeled P96.5, QCI054, or ZME018. Striking tumor regression and prolonged survival were measured following administration of 90Y-labeled P96.5. Average maximal decreases in tumor volume were 42.7 +/- 11.9 and 94.2 +/- 3.3 percent 28 and 58 days following 100 and 200 uCi 90Y-radiolabeled P96.5 administration, respectively. The time required to achieve four times the initial tumor volume was 6.1 +/- 0.9 days for buffer; 43 +/- 12 and 63 +/- 10 days for 50 and 100 uCi 90Y-radiolabeled P96.5; 7 +/- 2, 20 +/- 1, and 53 +/- 4 for 50, 100, and 200 uCi 90Y-radiolabeled QCI054; and 9 +/- 1, 13 +/- 1, and 29 +/- 3 days for 50, 100, and 200 uCi 90Y-radiolabeled ZME018, respectively. Average tumor regrowth failed to occur 180 days following administration of 200 uCi 90Y-labeled P96.5.(ABSTRACT TRUNCATED AT 400 WORDS)

Targeting of human glioma xenografts in vivo utilizing radiolabeled antibodies.

Radiolabeled antibodies provide a potential basis for selective radiotherapy of human gliomas. We have measured tumor targeting by radiolabeled monoclonal and polyclonal antibodies directed against neuroectodermal and tumor-associated antigens in nude mice bearing human glioma xenografts. Monoclonal P96.5, a mouse IgG2a immunoglobulin, defines an epitope of a human melanoma cell surface protein, and specifically binds the U-251 human glioma as measured by immunoperoxidase histochemistry. 111In-radiolabeled P96.5 specifically targets the U-251 human glioma xenograft and yields 87.0 microCuries (microCi) of tumor activity per gram per 100 microCi injected activity compared to 4.5 microCi following administration of radiolabeled irrelevant monoclonal antibody. Calculations of targeting ratios demonstrate deposited dose to be 11.6 times greater with radiolabeled P96.5 administration compared to irrelevant monoclonal antibody. The proportion of tumor dose found in normal organs is less than 10%, further supporting specific targeting of the human glioma xenograft by this antibody. Monoclonal antibody ZME018, which defines a second melanoma-associated antigen, and polyclonal rabbit antiferritin, which defines a tumor-associated antigen, demonstrate positive immunoperoxidase staining of the tumor, but comparatively decreased targeting. When compared to the 111In-radiolabeled antibody, 90Y-radiolabeled P96.5 demonstrates comparable tumor targeting and percentages of tumor dose found in normal organs. To test the therapeutic potential of 90Y-radiolabeled P96.5, tumors and normal sites were implanted with miniature thermoluminescent dosimeters (TLD). Seven days following administration of 100 microCi 90Y-radiolabeled P96.5, average absorbed doses of 3770, 980, 353, and 274 cGy were observed in tumor, liver, contralateral control site, and total body, respectively. Shared cell surface antigens among neuroectodermally derived neoplasms provide a basis for exploration of human glioma radioimmunotherapy.

Radioimmunotherapy of human colon cancer in nude mice.

Nude mice bearing subcutaneous human colon cancer xenografts (LS174T) were treated with 120 microCi of yttrium 90-labeled anti-carcinoembryonic antigen monoclonal antibodies (specific therapy), 120 microCi of 90Y-labeled anti-melanoma monoclonal antibodies (nonspecific therapy), or phosphate-buffered saline solution (no treatment control). Mean (+/- SD) tumor growth rates (percent increase per day) over the first 30 days of the study were as follows: 0.6% +/- 0.2% per day (specific therapy); 17.7% +/- 5.7% per day (nonspecific therapy); and 30.5% +/- 4.2% per day (control). In all three groups, tumors over 1 g had similar doubling times (5.74 +/- 0.71 d). Specific therapy caused a lag in tumor growth corresponding to a 3-logarithm cell kill. Estimated tumor dose of radiation obtained by tissue analysis was 34 and 14 Gy for specific and nonspecific therapy, respectively. In conclusion, 120 microCi of 90Y-labeled anti-carcinoembryonic antigen monoclonal antibodies was effective in suppressing growth of human colon cancer xenografts. Clinical studies with this preparation are recommended.

Role of bone marrow transplantation in 90Y antibody therapy of colon cancer xenografts in nude mice.

The efficacy of bone marrow transplantation (BMT) for the prevention of 90Y toxicity and extension of survival in nude mice with i.p. LS174T carcinomatosis was evaluated. 90Y-labeled monoclonal antibody (MAB) directed against carcinoembryonic antigen (90Y-anti-CEA MAB) at a dose of 120 microCi caused no deaths due to treatment toxicity and increased the duration of animal survival. No long term cures were obtained in these mice. At doses of 160 microCi or more 90Y-anti-CEA MAB led to hematological deaths. Nude mice were given i.p. injections of 10(6) LS174T tumor cells on day 0. On day 7 the mice received 90Y-anti-CEA MAB i.p. at doses of 120-225 microCi. Syngeneic bone marrow cells (10(7) cells) were then injected i.v. into the mice at 1, 3, 5, 7, 10, or 14 days following 90Y treatment. In the absence of BMT, toxic deaths for animals given 175 microCi 90Y were 11 of 24 (46%) with a median survival of 17 days and 13 of 20 (65%) for animals given 225 microCi 90Y with a median survival of 14 days. Animals receiving the same two doses of 90Y and given BMT 5 days following the 90Y treatment showed 0 of 24 (0%) and 0 of 54 (0%) toxicity deaths, respectively. The optimal time of BMT in relation to 90Y therapy was dependent upon the dose of 90Y-anti-CEA MAB (225 microCi, 3-5 days; 175 microCi, 5-14 days). The mean survival in tumor bearing animals was extended from 31.7 +/- 1.2 (SE) to 45.3 +/- 2.0 days by treatment with 120 microCi of 90Y-anti-CEA MAB. By increasing the dose of 90Y-anti-CEA MAB to 225 microCi and undertaking BMT 5 days later the mean survival was further extended to 63.2 +/- 3.6 days (P less than 0.005). BMT administered at the optimal times can prevent toxic deaths and facilitates higher, more effective doses of tumor specific 90Y-MAB.

Targeting and therapy of human glioma xenografts in vivo utilizing radiolabeled antibodies.

Radiolabeled antibodies provide a potential basis for selective radiotherapy of human gliomas. We have measured tumor targeting by radiolabeled monoclonal antibodies directed against neuroectodermal and tumor-associated antigens in nude mice bearing human glioma xenografts. Monoclonal P96.5, a mouse IgG2a immunoglobulin, defines an epitope of a human melanoma cell surface protein and specifically binds the U-251 human glioma as measured by immunoperoxidase histochemistry. IIIIn-radiolabeled P96.5 specifically targets the U-251 human glioma xenograft and yields 87.0 microCi of tumor activity/g/100 microCi injected activity compared to 4.5 microCi following administration of 100 microCi radiolabeled irrelevant monoclonal antibody. Calculations of targeting ratios demonstrate the deposited dose to be 11.6 times greater with radiolabeled P96.5 administration compared to irrelevant monoclonal antibody. The dose found in normal organs is less than 20% of that in the tumor, further supporting specific targeting of the human glioma xenograft by this antibody. Monoclonal antibody ZME018, which defines a second melanoma-associated antigen, demonstrates positive immunoperoxidase staining of the tumor, but comparatively decreased targeting. To test the therapeutic potential of 90Y-radiolabeled P96.5 and ZME018, tumors and normal sites were implanted with miniature thermoluminescent dosimeters. Average absorbed doses of 3770 +/- 445 (SEM) and 645 +/- 48 cGy in tumor, 353 +/- 41 and 222 +/- 13 cGy in a contralateral control i.m. site, 980 +/- 127 and 651 +/- 63 cGy in liver, and 275 +/- 14 and 256 +/- 18 cGy in total body were observed 7 days following administration of 100 microCi 90Y-radiolabeled P96.5 and ZME018, respectively. Calculations of absorbed dose by the medical internal radiation dose method confirmed thermoluminescent dosimeter absorbed dose measurements. To test the therapeutic potential, tumor-bearing nude mice were given intracardiac injections of either buffer or 90Y-radiolabeled P96.5 or ZME018. Tumor regression was measured in 1 of 12, 9 of 10, and 12 of 12 compared to 0 of 10, 1 of 10, and 2 of 10 animals following administration of 50, 100, or 200 microCi 90Y-labeled P96.5 and ZME018, respectively. Average maximal decreases in tumor volume were 42.7 +/- 11.9 and 94.2 +/- 3.3% 28 and 58 days following 100 and 200 microCi 90Y-radiolabeled P96.5 administration, respectively. In contrast, no average decrease in tumor volume was noted following 50, 100, or 200 microCi 90Y-labeled ZME018.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of yttrium-90-labeled anti-carcinoembryonic antigen monoclonal antibody on the morphology and phenotype of human tumors grown as peritoneal carcinomatosis in athymic mice.

Grossly visible peritoneal carcinomatosis resembling that seen in man was produced in athymic mice 7 days after intraperitoneal injection of 8 x 10(5) cells of the carcinoembryonic antigen (CEA)-producing human colon carcinoma cell line LS174T. The mice received intraperitoneal injections of 40 to 160 microCi of yttrium-90 (90Y)-labeled anti-CEA monoclonal antibody (MAb). When the mice were killed 12 days after injection, a significant inhibition of tumor growth, ranging from 40% to 95%, was observed in the treated animals when compared to the growth of tumors in the untreated animals (P less than 0.001). No mortality secondary to the therapy was seen. The bone marrow was depleted significantly at the higher doses of labeled MAb, but total recovery was observed 4 weeks after treatment. Histologically, the treated tumors showed extensive radiation effects early in the posttherapy period and massive necrosis at later times. Minute foci of viable tumor remained in the periphery. New tumor outgrowths with histologic features similar to those in the untreated controls began to appear 3 weeks after therapy. The CEA expression of the treated tumors was similar to that of the untreated controls during the early posttreatment period, diminishing progressively as the tumors became necrotic. Newly grown tumor nodules in the treated animals lacked significant CEA expression both initially and at later times. Our studies suggest that therapy with 90Y-anti-CEA MAb therapy results in selection of tumor clones lacking CEA, and that a single large dose of 90Y-MAb should be more effective than multiple fractions of smaller doses.

Prolongation of survival of nude mice bearing human colon cancer. Treatment with yttrium 90-labeled anti-carcinoembryonic antigen antibody.

Nude mice bearing diffuse intraperitoneal carcinomatosis of the human colon cancer cell line LS174T were treated with an anti-carcinoembryonic antigen monoclonal antibody (MAB) that was labeled with yttrium 90 (90Y-ZCE025). Control animals were either untreated or treated with nonspecific 90Y-MAB (90Y-96.5c). The median survival (MS) for untreated animals was 26 days. The MS for specific and nonspecific therapy that consisted of 120 microCi of 90Y-MAB was 69 and 34 days, respectively. No significant improvement in the MS was observed with a second 120-microCi administration of 90Y-MAB given two weeks later. A decreased MS was observed with 80 microCi of 90Y-MAB given every four days for three cycles. In each category, specific therapy had a significant advantage over nonspecific therapy in increased effectiveness and decreased toxicity. The 90Y-ZCE025 therapy gave an increased life span of almost 200%. The therapeutic effects with different dosing regimens have important implications for treatment planning.

Rapid radioiodination of rose bengal at room temperature.

Published methods for radioiodination of rose bengal require reaction times of 1 hr or more at temperature from 50 to 120 degrees C. Through the use of an acidified ethanol solvent and potassium iodate oxidant, purified rose bengal is radioiodinated at room temperature within 15 min with chemical yields ranging between 93 and 97%. Radiochemical impurities are sufficiently minimized to permit preparation in a single 10-ml serum vial, requiring no additional purification steps. The method reported here is readily adaptable to cold-kit preparation.