scJVAE: A novel method for integrative analysis of multimodal single-cell data.

The study of cellular decision-making can be approached comprehensively using multimodal single-cell omics technology. Recent advances in multimodal single-cell technology have enabled simultaneous profiling of more than one modality from the same cell, providing more significant insights into cell characteristics. However, learning the joint representation of multimodal single-cell data is challenging due to batch effects. Here we present a novel method, scJVAE (single-cell Joint Variational AutoEncoder), for batch effect removal and joint representation of multimodal single-cell data. The scJVAE integrates and learns joint embedding of paired scRNA-seq and scATAC-seq data modalities. We evaluate and demonstrate the ability of scJVAE to remove batch effects using various datasets with paired gene expression and open chromatin. We also consider scJVAE for downstream analysis, such as lower dimensional representation, cell-type clustering, and time and memory requirement. We find scJVAE a robust and scalable method outperforming existing state-of-the-art batch effect removal and integration methods.

Multi-source domain adaptation of social media data for disaster management.

Labeled data scarcity at the time of an ongoing disaster has encouraged the researchers to use the labeled data from some previous disaster for training and transferring the knowledge to the current disaster task using Domain Adaptation (DA). However, often labeled data from more than one previous disaster may be available. As all deep learning models are data-hungry and perform better if fed with more annotated data, it is advisable to use data from multiple sources for training a Deep Convolutional Neural Network (DCNN). One of the easiest ways is to simply combine the data from multiple sources and use it for training. However, this arrangement is not that straightforward. The models trained on the combined data from various sources do not perform well on the target, mainly due to distribution discrepancies between multiple sources. This has motivated us to explore the challenging area of multi-source domain adaptation for disaster management. The aim is to learn the domain invariant features and representations across the domains and transfer more related knowledge to solve the target task with improved accuracy than single-source or combined-source domain adaptation. This study proposes a Multi-Source Domain Adaptation framework for Disaster Management (MSDA-DM) to classify disaster images posted on social media based on unsupervised DA with adversarial training. The empirical results obtained confirm that the proposed model MSDA-DM performs better than single-source DA by up to 10.83% and combined-source DA by up to 5.06% in terms of F1-score for different sets of source and target disaster domains. We also compare our model with current state-of-the-art models. The main challenge of multi-source DA is the choice of the relevant sources taken for training since, unlike single-source DA that handles only source-target distribution drift, the multi-source DA network has to address both source-target and source-source distribution drifts.

A novel reversible logic gate and its systematic approach to implement cost-efficient arithmetic logic circuits using QCA.

Quantum-dot cellular automata, is an extremely small size and a powerless nanotechnology. It is the possible alternative to current CMOS technology. Reversible QCA logic is the most important issue at present time to reduce power losses. This paper presents a novel reversible logic gate called the F-Gate. It is simplest in design and a powerful technique to implement reversible logic. A systematic approach has been used to implement a novel single layer reversible Full-Adder, Full-Subtractor and a Full Adder-Subtractor using the F-Gate. The proposed Full Adder-Subtractor has achieved significant improvements in terms of overall circuit parameters among the most previously cost-efficient designs that exploit the inevitable nano-level issues to perform arithmetic computing. The proposed designs have been authenticated and simulated using QCADesigner tool ver. 2.0.3.

Association of Periodontal Health with Orthodontic Appliances among Indian Patients.

BACKGROUND: To assess the association of periodontal status of the patients with and without orthodontic treatment. MATERIALS AND METHODS: This cross-sectional study was conducted among 520 patients (220 undergoing orthodontic procedure and 300 non-orthodontic patients). Periodontal health status was assessed using community periodontal index and loss of attachment. Data were analyzed using SPSS version 16 and level of significance used was 5% level. RESULT: Overall mean number of segments for bleeding component (Score 1) was 0.86 ± 0.708, that of calculus (Score 2) 0.30 ± 0.460, for shallow pockets (4-5 mm) (Score 3) 0.33 ± 0.744 and for deep pockets (6 mm or more) (Score 4) 0.38 ± 0.476. Patients with orthodontic appliances had poor periodontal status than the non-orthodontic patients (P < 0.05). CONCLUSION: Patients undergoing orthodontic treatment have increased the level of periodontal status as it leads to more retention of food debris. Hence, these patients should be motivated to maintain good oral hygiene.

Transbronchial administration of adenoviral-mediated interleukin-10 gene to the donor improves function in a pig lung transplant model.

Interleukin-10 (IL-10) gene transfection of donor lungs prior to transplantation is an attractive strategy to reduce ischemia-reperfusion induced lung injury. However, experimental data with gene therapy in large animal models of lung transplantation are generally lacking. We have developed a simple clinically applicable technique for adenoviral-mediated gene delivery of human IL-10 to the lung of large animals that provides homogenous gene expression after 12-24 h of transfection. Using this technique of gene delivery, we have studied the dynamics of adenoviral gene delivery to the lung in the setting of lung transplantation. Although there is a persistent inflammatory response to the adenoviral vector, we achieved significant expression of human IL-10 in lung tissue before lung retrieval to obviate the deleterious impact of the adenoviral vector on the donor lung. The administration of adenoviral-mediated human IL-10 to the donor lung reduced ischemia-reperfusion injury and improved graft function after lung transplantation in this pig lung transplantation model. Transfection of adenoviral-mediated human IL-10 to the donor lung prevented the release of inflammatory cytokines such as IL-6 in lung tissue and plasma. We have demonstrated that IL-10 gene therapy has significant potential to prevent or treat the inflammatory response associated with ischemia-reperfusion injury in lung transplantation. In the future, IL-10 gene therapy could also be used for immunomodulation or tolerance induction.

Radiolabeled immunoglobulin therapy: old barriers and new opportunities.

The development of cancer-selective therapies, in particular radiolabeled immunoglobulin therapy (RIT), has stalled. RIT limitations/opportunities are identified in translational research in nude mice, beagles and rhesus monkeys, and in patients with Hodgkin's disease, neurological paraneoplastic syndromes or small vessel vasculitis. Intravenous RIT is most successful in patients with hematological malignancies due to high tumor uptake and long tumor retention of radiolabeled immunoglobulins. Patients with solid tumors are only expected to benefit from RIT by the administration of radiolabeled immunoglobulins directly into the tumor. Tumor-reactive IgG is the best vehicle for i.v. RIT. Tumor-reactive IgM is the best vehicle for intratumoral RIT. The authors do not intend to review the whole clinical RIT experience, but instead analyze the current limitations to success and how they can be circumvented. When the scientific community can reach a consensus on the development and use of these promising and economical radiopharmaceuticals, increasing numbers of patients with recurrent cancer will start to benefit from RIT.

Intraperitoneal radioimmunotherapy with human monoclonal IGM in nude mice with peritoneal carcinomatosis.

UNLABELLED: In an effort to improve loco-regional control of ovarian cancer, intraperitoneal (i.p.) administration of an yttrium-90 (90Y) labeled human IgM was studied in a nude mouse model of the disease. METHODS: Athymic nude mice bearing i.p. nodules of SKOV3 NMP2, a human ovarian carcinoma cell line, received single (50-400 microCi) or fractionated (150-510 microCi) administrations of 90Y-labeled 2B12. Untreated mice and mice treated with unlabeled immunoconjugate served as controls. Mice were monitored for weight loss, blood counts and survival. RESULTS: Mice that received at least 300 microCi of 90Y-labeled 2B12 in a single administration lost more than 10% of their body weight with some early deaths, both of which were prevented with fractionated administration. Granulocytes and lymphocytes declined with treatment while red blood cell counts were relatively stable. Untreated mice and mice treated with unlabeled immunoconjugate had a median survival time of 20 and 17 days respectively. Treatment with 90Y-labeled 2B12 increased median survival by 11-12 days per 100 microCi for single (50-300 microCi) and fractionated administrations (150-510 microCi). The highest fractionated activity produced over three logs of tumor cell kill without significant toxicity. CONCLUSION: Intraperitoneal RIT with 90Y-labeled 2B12 appears to be an attractive modality to treat peritoneal carcinomatosis and warrants further development.

Radiolabeled immunoglobulin therapy in patients with Hodgkin's disease.

Translational research supports the use of radiolabeled antiferritin for recurrent Hodgkin's disease. A 60% tumor response rate is obtained after treatment of out-patients with polyclonal radiolabeled antiferritin. Hodgkin's disease masses shrink after radiolabeled antiferritin treatment due to the radiation delivered by the radioimmunoconjugate. Unlabeled antiferritin does not cause tumor shrinkage. Hodgkin's disease provides unique opportunities for the development and optimization of radiolabeled immunoglobulin therapy for other malignancies as well. Radiolabeled Immunoglobulin Therapy is a useful addition to the cancer treatment armamentarium due to its high therapeutic ratio: high tumor response rates with side effects limited to hematopoetic tissues.

Pharmacokinetics of radiolabeled polyclonal antiferritin in patients with Hodgkin's disease.

The objective was to identify pharmacokinetic parameters predictive for tumor response and normal tissue side effects after i.v. administered radiolabeled rabbit antihuman ferritin IgG. Twenty-eight patients with recurrent Hodgkin's disease received 2 mg of rabbit antihuman ferritin i.v., labeled with 4-7 mCi of In-111 followed by two doses of 0.25, one dose of 0.3, or one dose of 0.4 mCi of Y-90-labeled antiferritin per kg of body weight 1 week later. Radioactivity and HPLC measurements of blood and urine samples and liver and tumor volumes identified on sequential whole-body scans provided the data for a pharmacokinetic analysis covering the first 6 days after the administration of the radioimmunoconjugate. Side effects and tumor response were recorded. Temporary hematological toxicity was noted in all patients. Sixteen patients showed a tumor response. The Y-90 blood level at 1 h after administration correlated with the severity of subsequent hematological toxicity. The rapid blood elimination half-life of radioactivity was 4.4 h. Less than 5% of the administered radioactivity was eliminated in the first 24 h urine. The slow blood elimination half-life was 44 and 37 h for In-111 and Y-90, respectively. One of 12 retreated patients produced anti-rabbit IgG antibodies. The volume of distribution was larger for Y-90 than for In-111-labeled antiferritin (160 versus 110% of estimated blood volume). Accidentally extravasated rabbit IgG was rapidly catabolized in perivascular tissues with an effective half-life of less than 35 h. Slower catabolism was noted for rabbit IgG in blood (t(1/2) = 40 h), liver (t(1/2) = 62 h) or tumor (t(1/2) = 40-80 h). Twelve of 13 patients with an effective tumor half-life > 57 h showed a tumor response. I.v. administered polyclonal rabbit antihuman ferritin, labeled with In-111 or Y-90 is stable in vivo and targets Hodgkin's disease. Intravascular Y-90 causes a vascular leak and a larger volume of distribution for antiferritin. Elevated Y-90 blood levels at 1 h and a tumor half-life of >57 h predict for hematological toxicity and tumor response, respectively.

Fractionated radiolabeled antiferritin therapy for patients with recurrent Hodgkin's disease.

The objective of this study was to determine the therapeutic ratio of fractionated radiolabeled immunoglobulin therapy (RIT) for patients with recurrent Hodgkin's disease. Ninety patients with recurrent Hodgkin's disease received 2 mg of yttrium-90-labeled polyclonal rabbit antihuman ferritin IgG i.v. Fifty-seven patients received a single (unfractionated) administration per treatment cycle; 11 of them were treated with 0.3 mCi/kg body weight, 39 were treated with 0.4 mCi/kg body weight, and 7 received 0.5 mCi/kg body weight per treatment cycle. Thirty-three patients had their radiolabeled immunoglobulin administration separated (fractionated) in 2 x 0.25 mCi/kg body weight (total activity, 0.5 mCi/kg). The interval between fractions was 1 week. Radioimmunoconjugates did not cause serious acute side effects. In vivo radioimmunoconjugates were stable. Human antirabbit IgG antibodies were found in 2 of 50 retreated patients (<5%). Hematological toxicity was the only side effect noted in all patients, and it was usually temporary. Response rates (RRs) were 20%, 61%, and 86% after 0.3, 0.4, or 0.5 mCi/kg unfractionated yttrium-90-labeled antiferritin. The RR for patients treated with fractionated RIT was 42%. In the fractionated RIT group, complete responses were decreased, and progressive disease increased (P < 0.05). Complete responses had a medium duration of 6 months. Median survival times were 390 days for 1 x 0.4 mCi/kg and 300 days for the 2 x 0.25 mCi/kg patient group. Fractionation did not provide the expected decrease in hematological toxicity or the expected increase in tumor RRs.

Indium-111- and yttrium-90-labeled human monoclonal immunoglobulin M targeting of human ovarian cancer in mice.

UNLABELLED: Most patients with ovarian cancer have disease in the peritoneal cavity. Treatment of this region is inadequate because recurrences are frequent. Increased radiation doses to tumor and, hence, greater tumor control may be possible with intraperitoneal (i.p.) administration of radiolabeled human monoclonal immunoglobulin M (IgM), which is reactive with tumor-associated antigens. METHODS: Biodistribution studies were performed in nude mice bearing i.p. nodules of human ovarian cancer after administration of human monoclonal IgMlambda (AC6C3-2B12), labeled with 111In or 90Y. Irrelevant 111In-labeled human IgMlambda (CH-1B9) and 90Y-aggregate served as specificity controls. RESULTS: Intravenous administration of 111In-labeled AC6C3-2B12 produced low tumor and high liver and spleen uptake. Intraperitoneal administration of AC6C3-2B12 labeled with 111In or 90Y resulted in rapid, high tumor uptake (>45% of injected dose per gram of tumor at 3 hr) that was at least three-fold higher than any normal organ. Biodistribution results were similar for 111In- and 90Y-labeled IgM. Tumor uptake of 111In-labeled AC6C3-2B12 was two-fold greater than that of 111In-labeled CH-1B9. Normal organ uptakes were similar for tumor-reactive and irrelevant IgM. Radioimmunoconjugates were retained in the peritoneal cavity for a prolonged period of time. Yttrium-90 aggregate demonstrated high tumor and bone uptake. CONCLUSION: Higher tumor uptake was observed after i.p. administration of tumor-reactive IgM than after irrelevant IgM. The in vivo behavior of tumor-reactive IgM was similar when it was radiolabeled with either 111In or 90Y. Therefore, 111In-based imaging studies can be used to predict the biodistribution of subsequently administered 90Y-labeled IgM. Further development of radiolabeled AC6C3-2B12 as a diagnostic and therapeutic agent for patients with advanced ovarian carcinoma is warranted.

Tumour therapy with radiolabelled antibodies: optimisation of therapy.

The promise of radiolabelled immunoglobulin therapy (RIT) for selective, patient friendly, cancer treatment has not yet been fulfilled. Only patients with haematological malignancies show sizable response rates after RIT. With solid tumours, intravenous administration of radiolabelled antibodies does not provide sufficient tumour targeting. However, intracompartmental administration may solve this problem, particularly if tumour reactive IgM is used. Clinical progress in RIT depends on understanding the important RIT variables: antigen, antibody, radioisotope, conjugation chemistry, activity escalation, fractionation and protein dose. These are reviewed and a new translational decision tree/flow diagram is presented that can limit analysis to the most important RIT variables for a particular disease. These variables may differ depending on the type and stage of cancer, but the guiding principles in RIT development remain the same: selectivity and accountability. The proper application of these principles leads to the definition of a new series of phase I, II, III studies. These studies are more appropriate for the clinical exploration of RIT and place an emphasis on therapeutic ratio rather than toxicity.

Effects of linker chemistry on the pharmacokinetics of radioimmunoconjugates.

Radiolabeled monoclonal antibodies reactive with tumor-associated antigens can selectively deliver cytotoxic or diagnostic isotopes to malignant cells in vivo. To achieve maximum retention of radiolabel in tumor and a more rapid clearance of radioisotope from normal tissues, six linker immunoconjugates were evaluated in studies using nude mice and beagle dogs. All radioimmunoconjugates contained a mouse monoclonal IgG (QCI) reactive with human ferritin. Different chemical linkages were inserted between immunoglobulins and the radiolabeled chelate (DTPA). Three linkers (ITCB, DSS and BSOCOES) were stable in in vitro and in vivo studies. Three linkers (EGS, DST and DSP) were labile in in vitro and in vivo studies. Indium-111 labeled antiferritin-containing ITCB or DSS linker showed high uptake in human hepatoma xenografts in nude mice. In addition, long blood half-lives and higher normal liver uptakes were noted. Studies of whole body retention of radioimmunoconjugates showed approximately three-fold faster elimination of radioimmunoconjugates containing a labile linker (EGS). EGS linker is the labile linker with the highest therapeutic ratio: higher tumor uptake, but low normal liver uptake and a shortened blood half-life of the radioimmunoconjugate. The differences in normal tissue uptake (liver) between EGS and ITCB were confirmed in beagle dogs. Urine elimination studies and incubation or radioimmunoconjugates in serum or tissue homogenates of tumor, liver or muscle, showed that enzymes in serum and liver homogenates were able to cleave the labile linkers, which led to a more rapid elimination of low molecular weight radioactive metabolites in urine. The metabolism of linker radioimmunoconjugates in tumor was less effective. The labile linker DSP appears less useful because sulphydryl groups that are generated by cleavage of cause higher uptake radioactivity in normal kidney. Biodistribution studies in nude mice were confirmed by serial immunoscintigraphy studies on individual mice. The immunoscintigraphy studies are semi-quantitative only, but enable the use of lower numbers of experimental animals. This is of particular significance in large experimental animals such as beagle dogs. The labile linker approach can reduce normal tissue radiation exposure. The study also provides an example of preclinical optimization of radioimmunoconjugates. Continued use of the appropriate preclinical animal models will accelerate more successful applications of radioimmunoconjugates in cancer patients.

Preclinical analysis of radiolabeled anti-GD2 immunoglobulin G.

BACKGROUND: Unlabeled murine monoclonal anti-GD2 immunoglobulin (Ig)G (14G2a) reactive with nervous system diganglioside and neuroblastoma, melanoma, and small cell lung carcinoma produces tumor regression. However, serious acute abdominal pain, paresthesia, hypotension and hypertension, syndrome of inappropriate secretion of antidiuretic hormone (SIADH), and occasional motor weakness occur. Studies in preclinical animal models can elucidate the mechanism of the observed neurotoxicity and lead to anti-GD2 antibody treatment with a higher therapeutic ratio. METHODS: One mg of 14G2a or control IgG was labeled with 1-2 mCi of indium-111 and administered intravenously to beagles (n = 8). In 2 dogs, additional high dose (200 mg) unlabeled 14G2a was given over 5 days. Whole body gamma camera images and SPECT scans were obtained repeatedly over 7 days. On Day 7, sciatic nerve conduction studies were performed, and after euthanasia radioactivity was determined in major organs. RESULTS: Unlabeled high dose 14G2a administered to mice, rats, or rabbits did not cause neurotoxicity within 3 weeks. GD2 antigens were shown by immunochemistry to be present in brain and peripheral nerve tissues of rodents and beagles. After in vivo administration of radiolabeled 14G2a, canine lymph nodes showed specific uptake, but only minimal radioactivity was found in the nervous system. Dogs that received additional high dose unlabeled 14G2a showed much higher lymph node uptake and follicular lymph node hyperplasia. Low motor response amplitudes on nerve conduction studies were noted. CONCLUSIONS: A radioisotope label on IgG and its visualization in a large series of animal models indicate that a low protein dose of anti-GD2 IgG will not cause neurologic side effects in patients. High protein dose anti-GD2 IgG may enhance antineoplastic effects and contribute to neurotoxicity through stimulation of normal lymphocytes with subsequent release of cytokines.

Recurrence of Hodgkin's disease after indium-111 and yttrium-90 labeled antiferritin administration.

BACKGROUND: Indium-111 labeled antiferritin targets 95% of all Hodgkin's disease lesions with a diameter of 1 cm or more. Subsequent treatment with yttrium-90 labeled antiferritin secures a high response rate in patients with recurrent Hodgkin's disease. METHODS: A total of 87 patients were entered on one of three different yttrium-90 labeled antiferritin protocols. Recurrences after yttrium-90 treatment were analyzed. Nine patients were retreated with involved external beam radiation fields, selected with the help of indium-111 labeled antiferritin. RESULTS: In single-agent yttrium-90 antiferritin studies, a response rate of more than 60% was found, with an average response duration of 6 months. One-third of the patients had recurrences in previously uninvolved areas. Repeat indium antiferritin scintigraphy allowed for the selection of new radiation fields for recurrences. In-field disease control was obtained for a median of 8 months, but new recurrences in new areas occurred. Chemotherapy or radiation therapy given immediately before antiferritin decreased tumor targeting with indium-111 labeled antiferritin. CONCLUSIONS: Recurrences after radiolabeled antiferritin treatment are not due to radioresistant Hodgkin's disease. In contrast, Hodgkin's disease less than 1 cm in diameter is not targeted and not controlled by radiolabeled antiferritin. New multimodality regimens with a higher therapeutic ratio are needed for treatment of Hodgkin's disease with curative intent. Radiolabeled antiferritin can be incorporated in such regimens to secure better control of bulky Hodgkin's disease (>1 cm in diameter), but it should be given before chemotherapy or radiation therapy.

Intralesional radiolabeled human monoclonal IgM in human tumor xenografts.

BACKGROUND AND PURPOSE: Intralesional (i.l.) administration of radiolabeled human monoclonal IgM could provide a new method for increasing the radiation dose delivered to a tumor without exceeding normal tissue tolerance. MATERIALS AND METHODS: Nude mice with subcutaneous human head and neck squamous cell carcinoma nodules were injected either intralesionally or intravenously with a tumor-reactive human monoclonal IgM (CR4E8) labeled with indium-111 (111In) or yttrium-90 (90Y). Groups of mice were sacrificed at different time points and their tumors and major organs were excised and counted for radioactivity. Additional mice that were treated with i.l. 90Y-labeled CR4E8 were sacrificed at the same time points for tumor autoradiography. Serial whole-body gamma camera images were obtained from additional mice treated with i.l. 111In-labeled CR4E8. Intralesionally administered 111In-labeled irrelevant IgM (CH-1B9) and 90Y-aggregate served as specificity controls. RESULTS: Intralesional administration of radiolabeled IgM resulted in prolonged high tumor radioactivity with little normal tissue uptake, with kidney and liver having the highest values. The biodistribution of i.l. CR4E8 was similar whether labeled with 111In or 90Y. Tumor uptake of i.l. irrelevant IgM appeared to be lower and tumor retention appeared to be shorter. Intravenous administration of tumor-reactive IgM resulted in very low tumor radioactivity with high liver and moderate spleen uptake. The i.l. administration of 90Y-aggregate produced prolonged high tumor radioactivity with little normal tissue uptake, with bone having the highest value. Tumor autoradiographs demonstrated that the radiolabeled IgM diffused through the tumor over time while the 90Y-aggregate remained localized at the injection site. Gamma camera scintigraphy corroborated the results of the biodistribution studies. CONCLUSIONS: Intralesional but not intravenous administration of 111In- or 90Y-labeled human IgM results in high tumor radioactivity with low normal tissue exposure. Myelotoxicity is not anticipated to be the dose-limiting normal tissue toxicity of this treatment. Further development of human IgM for the i.l. treatment of human malignancies appears to be warranted.

Proposal for translational analysis and development of clinical radiolabeled immunoglobulin therapy.

BACKGROUND AND PURPOSE: Radiolabeled immunoglobulin therapy (RIT) can be a selective, effective, low-toxicity outpatient cancer therapy. A consensus on the best approach for the preclinical and clinical development of RIT reagents needs to be developed. We report the M.D. Anderson Cancer Center prior experience in translating RIT from laboratory to clinic for the treatment of Hodgkin's disease and propose a flow diagram for the development of RIT for other malignancies. MATERIAL AND METHODS: Three different animal models are described: nude mice bearing human tumor xenografts, normal beagle dogs, and normal rhesus monkeys. We produced and purified antibodies and prepared chelate-immunoconjugates reactive with six different human tumor-associated antigens. The Igs used were derived from rabbits, mice, and humans (human-derived RIT reagents being less immunogenic in human patients). Eighty patients with refractory Hodgkin's disease were treated with radiolabeled antiferritin. RESULTS: We recommend a two-injection scheme using, (1) an indium-111-labeled radioimmunoconjugate for diagnosis, pharmacokinetic studies, and dosimetry, and (2) a yttrium-90-labeled radioimmunoconjugate for therapy. The animal models provide useful data on tumor targeting, radiotoxicology, and undesirable biodistributions. A 70% response rate is obtained in patients with advanced recurrent Hodgkin's disease. More extensive preclinical testing allows for safer and more effective clinical RIT studies. CONCLUSIONS: We recommend, (1) preclinical optimization of chelation chemistry, Ig size, Ig origin, route of administration, and fractionation, (2) new clinical Phase I-III studies more appropriate for RIT development than the classical Phase I-III studies used for the development of chemotherapeutic agents, and (3) more extensive preclinical testing of RIT reagents.

Intraperitoneal indium-111- and yttrium-90-labeled human IgM (AC6C3-2B12) in nude mice bearing peritoneal carcinomatosis.

UNLABELLED: Radiolabeled monoclonal antibodies are utilized increasingly for the diagnosis and treatment of human cancer. Tumor targeting of radiolabeled human monoclonal IgM improves with compartmental administration and might be useful for the diagnosis or treatment of peritoneal carcinomatosis. METHODS: A human monoclonal antibody IgM lambda (AC6C3-B12) reactive with human adenocarcinomas was conjugated to isothiocyanato-2-benzyl-3-methyl-diethylenetriamine-penta-a cetic acid and labeled with either 111In or 90Y. Nude mice bearing intra-abdominal lumps of a human colorectal carcinoma cell line (SW620) were used as a model for peritoneal carcinomatosis. A human monoclonal antibody IgM lambda (CR4E8) reactive with human squamous-cell carcinoma was used as a control. RESULTS: Indium-111-IgM and 90Y-IgM immunoconjugates were compared in nude mice at 2, 24, 72, 120 and 144 hr after intraperitoneal administration. Both showed high specific tumor uptake. The tumor-effective half-lives of the immunoconjugates were 39 hr for indium and 46 hr for yttrium. Tumor-to-normal organ ratios were high and similar for both reagents. Only the femur uptake at later time points was relatively higher for the 90Y-IgM than for 111In-IgM. The tumor uptake of specific AC6C3-2B12 was about fourfold higher than the uptake of aspecific CR4E8 at 24 and 120 hr. CONCLUSION: The combination of 111In- and 90Y-labeled AC6C3-2B12 offers a new opportunity to develop safer and more effective methods for diagnosing and treating human patients with peritoneal carcinomatosis.

Maleimido derivatives of diethylenetriaminepentaacetic acid and triethylenetetraaminehexaacetic acid: their synthesis and potential for specific conjugation with biomolecules.

Immunoconjugates sometimes suffer changes in immunoreactivity and tumor targeting because the chelators used interfere with antigen binding. To try to circumvent such problems, two new homobifunctional chelating agents, 2,6-bis[p-[(beta-maleimidopropionyl) amino]benzyl]diethylenetriamine- N,N,N',N",N"-pentaacetic acid (MPBz-DTPA) and 2,9-bis [p-(beta-maleimidopropionyl)amino]benzyl] triethylenetetraamine-N,N,N',N',N",N"-hexaacetic acid (MPBz-TTHA), were synthesized for chelation of 111In and 90Y metal ions. Each of the new chelators contains two maleimido functional groups substituted at the carbon backbone. In this study, the overall chemical yields for MPBz-DTPA and MPBz-TTHA were approximately 5 and 4%, respectively. The intermediate and final compounds were purified by flash chromatography and fully characterized by 1H-NMR, 13C-NMR, and mass spectroscopy. Chemical modification of the maleimido group on each of these derivatives allowed specific conjugation with a sulfhydryl group at the hinge region of an antibody molecule and conjugation with other peptides. For instance, the two Fab' fragments, through their hinge-region sulfhydryl groups, could covalently attach to a homobifunctional chelator via thioether linkage to generate a Fab'-S-chelator-S-Fab' immunoconjugate. By design, immunoconjugates containing these new chelators will contain only one chelator derivative at a known region of antibody away from the antigen binding site. Consequently, these chelators may minimize changes in the immunoreactivity and improve tumor targeting of immunoconjugates that contain them.

Hematologic side effects of radiolabeled immunoglobulin therapy.

Radiolabeled immunoglobulin therapy (RIT) is a new cancer treatment that is more selective than its predecessors. Its dose-limiting normal tissue side effect is bone marrow toxicity, and hematopoietic stem cell damage appears to be its most significant mechanism. Platelet consumption in irradiated normal liver tissues and apoptosis of circulating peripheral blood lymphocytes are other, less important, hematologic side effects. 131I and 90Y are the radioisotopes most commonly used for RIT; in addition, animal toxicology and initial clinical studies of chelate immunoglobulins radiolabeled with 111In (for diagnosis) or 90Y (for therapy) are reviewed. The bone-seeking properties of free 90Y are not considered to be a major component of the hematologic damage caused by yttrium-labeled immunoglobulins. The microenvironment of the bone marrow system is not significantly damaged by current RIT protocols. Moreover, granulocyte colony-stimulating factor (G-CSF) can open the blood-marrow barrier. Bone marrow toxicity after RIT can be corrected by bone marrow transplantation, growth factors, blood products, or fractionation of RIT. Selection of the appropriate corrective regimen depends on the severity of the bone marrow damage and will further enhance the therapeutic ratio of RIT.