The effect of irradiation on the biodistribution of radiolabeled pegylated liposomes.

Purpose: The effect of total-body irradiation (TBI) on the biodistribution and pharmacokinetics of (111)In-DTPA-labeled pegylated liposomes (IDLPL) was evaluated in tumor-bearing nude mice as part of an ongoing effort to develop liposome-targeted radiosensitizers.

Methods And Materials: Mice received TBI (2 Gy or 5 Gy) according to two protocols: (1) to test the effect of radiation delivered 30 min before liposome injection on the time course of IDLPL biodistribution to tumor and normal tissues over 96 h; (2) to test the effect of radiation at times ranging from 72 h to 1 h before liposome injection on tumor and normal tissue uptake of IDLPL at 24 h. Tumor and tissue/organ levels of liposome uptake were measured by dissection and quantitation in a gamma counter.

Comparative biodistribution and metabolism of carbon-11-labeled N-[2-(dimethylamino)ethyl]acridine-4-carboxamide and DNA-intercalating analogues.

The tricyclic carboxamide N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA) is a DNA-intercalating agent capable of inhibiting both topoisomerases I and II and is currently in Phase II clinical trial. Many related analogues have been developed, but despite their potent in vitro cytotoxicities, they exhibit poor extravascular distribution. As part of an ongoing drug development program to obtain related "minimal intercalators" with lower DNA association constants, we have compared the biodistribution and metabolite profiles of the prototype compound, DACA, with three analogues to aid rational drug selection.

Single-fraction irradiation has no effect on uptake of radiolabeled pegylated liposomes in a tumor xenograft model.

Purpose: These studies were performed with the intention of examining the effect of single-fraction doses of radiotherapy (RT) on the tumor deposition of radiolabeled pegylated liposomes in an animal xenograft tumor model.

Methods And Materials: Human KB head-and-neck xenograft tumors were established in female nude mice. The effect of single fraction tumor RT doses (5, 10, 15, and 20 Gy) on the tumor uptake of intravenously administered (111)In-DTPA-labeled pegylated liposomes (IDLPL) was examined using two protocols: (1) to test the effect of RT delivered 30 min before liposome injection on the time course of tumor uptake over a 96-h period; (2) to test the effect of RT at times ranging from 72-h to 1-h before liposome injection on the levels of liposome uptake at 24 h.

Pegylated liposome-encapsulated doxorubicin and cisplatin enhance the effect of radiotherapy in a tumor xenograft model.

Concomitant chemotherapy and radiotherapy (CCRT) has recently been shown to improve treatment outcome in a range of solid tumors. Pegylated liposomes have the potential to target drugs directly to tumors and may increase the efficacy and reduce the toxicity of CCRT by selectively delivering radiosensitizing agents to tumor, as opposed to normal, tissues. In these studies, we have assessed CCRT using pegylated liposome encapsulated doxorubicin (PLED) and pegylated liposome encapsulated cisplatin (PLEC) against KB head and neck cancer xenograft tumors in nude mice.

Influence of tumour size on uptake of(111)ln-DTPA-labelled pegylated liposomes in a human tumour xenograft model.

The relationship between tumour size and uptake of(111)In-DTPA-labelled pegylated liposomes has been examined in a human head and neck cancer xenograft model in nude mice. The mean tumour uptake of(111)In-labelled pegylated liposomes at 24 hours was 7.2 +/- 6.

Pegylated liposome-encapsulated doxorubicin and cisplatin in the treatment of head and neck xenograft tumours.

Purpose: To evaluate the in vitro and in vivo activity of unencapsulated doxorubicin (DOX) and cisplatin (CDDP) and their pegylated liposome encapsulated counterparts (PLED and PLEC) in a subcutaneous model of human squamous cell cancer of the head and neck.

Methods: In vitro cytotoxicity was determined by means of the sulphorhodamine B assay and in vivo activity was assessed in terms of tumour growth delay following single intravenous doses of the various agents. Treatment-related toxicity was evaluated by means of serial weight measurement.

Biodistribution and pharmacokinetics of 111In-DTPA-labelled pegylated liposomes in a human tumour xenograft model: implications for novel targeting strategies.

The biodistribution and pharmacokinetics of 111In-DTPA-labelled pegylated liposomes in tumour-bearing nude mice was studied to examine possible applications of pegylated liposome-targeted anti-cancer therapies. Nude mice received an intravenous injection of 100 microl of 111In-DTPA-labelled pegylated liposomes, containing 0.37-0.

Pegylated liposomes have potential as vehicles for intratumoral and subcutaneous drug delivery.

The potential value of intratumoral or s.c. injections of pegylated liposomes as locoregionally targeted therapy of tumors and their draining lymph nodes was assessed in nude mice as part of an ongoing program aimed at developing pegylated liposomal radiosensitizers for the treatment of head and neck cancers.

Diagnostic and therapeutic evaluation of an anti-Langerhans cell histiocytosis monoclonal antibody (NA1/34) in a new xenograft model.

Scintigraphy using monoclonal antibodies has been suggested as a possible adjunct to conventional staging techniques for the routine staging and diagnosis of Langerhans cell histiocytosis. In this study we have developed a model for Langerhans cell histiocytosis comprising a CD1a-positive subcutaneous xenograft in the flanks of nude (nu/nu) mice. The anti-CD1a murine monoclonal antibody NA1/34 was investigated for its potential both as an imaging and as a therapeutic targeting agent in this model.

Determination of the immunoreactivity of radiolabeled monoclonal antibodies.

Radiolabeled monoclonal antibodies (mAbs) are in use for numerous immunoassays and localization studies both in vitro and in vivo. It is often important to determine to what extent the radiolabeling procedure has affected the immunoreactivity of the antibody. If, for example, the radioisotope was inserted in the antigen-binding site, this would adversely affect the ability of the antibody to bind to its antigen.

Animal models for tumor localization.

Many factors influence the uptake of radiolabeled monoclonal antibodies (mAbs) in tumors. Some are dependent on the antibody, such as affinity, intact immunoglobulin or fragment, route of administration, choice of radio isotope, or method of labeling. Others depend on properties of the tumor, such as site, size, vasculature, and antigen density on the tumor cell surface.

Phenotypic characterization of histiocytes infiltrating a leiomyofibrosarcoma.

We described previously a unique cutaneous tumour in a young pig, which was characterized by several criteria as a histiocytic leiomyofibrosarcoma. The lipid-laden macrophages (histiocytes) which permeated the tumour were CD2+/CD18+/CD49d+ but MAC387 (L1 antigen) and CD15 negative. The present study compared the phenotypes of histiocytes in tumour metastases in the liver with resident liver macrophages, revealing differential expression of certain macrophage activation markers.

In vitro cytotoxicity following specific activation of amygdalin by beta-glucosidase conjugated to a bladder cancer-associated monoclonal antibody.

We describe a novel version of antibody-directed enzyme prodrug therapy (ADEPT), with the use of amygdalin as prodrug. Amygdalin is a naturally occurring cyanogenic glycoside, which can be cleaved by sweet almond beta-glucosidase to yield free cyanide. If amygdalin could be activated specifically at the tumour site, then malignant cells would be killed without the systemic toxicity usually associated with chemotherapy.

Improving tumour targeting and decreasing normal tissue uptake by optimizing the stoichiometry of a two-step biotinylated-antibody/streptavidin-based targeting strategy: studies in a nude mouse xenograft model.

We aimed to study in detail the in vivo stoichiometry of the individual elements of the 2-step streptavidin based approach to tumour targeting, in a nude mouse xenograft model, by the administration of a first step consisting of biotinylated anti-tumour specific antibody and a second step consisting of streptavidin. This process was undertaken to identify the optimum conditions for radiotherapeutic tumour targeting using this approach. Antibody was biotinylated to various degrees (1-25 biotins per antibody).

Redesigned anti-human placental alkaline phosphatase single-chain Fv: soluble expression, characterization and in vivo tumour targeting.

Although much progress has been made in the production of recombinant antibodies and their fusions, there are still problems with solubility and folding. Useful antibodies produced from cloned hybridomas do not always result in scFvs behaving favourably. We report here further work on an scFv (H17E2) against the oncofetal antigen human placental alkaline phosphatase.

E-cadherin expression in bladder cancer using formalin-fixed, paraffin-embedded tissues: correlation with histopathological grade, tumour stage and survival.

To determine the potential prognostic value of epithelial cadherin (E-cadherin), a Ca(2+)-dependent cell-cell adhesion molecule, we have analysed its immunoreactivity and cellular localisation in 67 transitional cell carcinomas (TCC) using an avidin-biotin immunoperoxidase technique on formalin-fixed, paraffin-embedded tissues. These results were correlated with histopathological grade, tumour stage, presence of metastases and survival. In addition, 10 cystitis and 11 normal bladder biopsies were evaluated as controls.

Specific targeting of a mutant, activated FGF receptor found in glioblastoma using a monoclonal antibody.

A truncated epidermal growth factor receptor (EGFR) expressed from a rearranged and amplified EGFR gene is present at high frequency in gliomas. In this work we show that when this receptor is expressed in NIH3T3 fibroblasts it is partially activated and confers tumorigenicity to this cell line in vivo but no growth advantage in in vitro anchorage-independent growth assays. Because the mutation occurs in the extracellular domain of the receptor, it can be considered to represent a glioma-specific tumour marker.

Effect of tumour necrosis factor on the uptake of specific and control monoclonal antibodies in a human tumour xenograft model.

The investigations reported in this paper aim to exploit tumour necrosis factor (TNF)-induced vascular changes in an attempt to increase the tumour uptake of specific monoclonal antibody. The vascular permeability to monoclonal antibody of a human tumour xenograft increased 2.6-fold by 1 h post injection of 2.

Pharmacokinetics, biodistribution, and dosimetry of specific and control radiolabeled monoclonal antibodies in patients with primary head and neck squamous cell carcinoma.

The pharmacokinetics, biodistribution, and dosimetry of an IgG1 radiolabeled anti-mucin mAb (HMFG1) and an isotype-matched control (4D513) were studied in 29 patients with primary head and neck squamous cell carcinoma. Patients were given injections at 3 fixed time points prior to surgery, i.e.

Radiolabeled antibody combined with external radiotherapy for the treatment of head and neck cancer: reconstruction of a theoretical phantom of the larynx for radiation dose calculation to local tissues.

We propose to use radiolabeled antibodies in combination with external beam radiotherapy to improve locoregional control of head and neck cancer. In this case radiation toxicity to mucosa may become a dose-limiting factor and a calculation of the possible compensatory decrease to the external beam radiotherapy would be needed. For this purpose, the following theoretical phantom of a representative organ of this anatomic region, the larynx, was reconstructed and local dosimetric data were derived for a selection of beta-emitting isotopes.

Genetically engineered antibodies for diagnostic pathology.

Antibody genes can be cloned, genetically manipulated, and expressed in both homologous and heterologous expression systems to produce viable antigen-binding proteins complete with natural effector functions. Manipulation of antibody genes permits the expression of fusion proteins or truncated proteins that retain antigen-binding activity. The new antibody technologies are becoming increasingly sophisticated, permitting the alteration of antigen-binding responses, the transfer of antigen specificity between antibodies, and the expression of minimal-size antigen-binding protein domains.

90Y-labeled antibody uptake by human tumor xenografts and the effect of systemic administration of EDTA.

Purpose: A human tumor xenograft model was used to compare the tumor and normal tissue uptake of a tumor-associated monoclonal antibody radiolabeled with 125I or 90Y.

Methods And Materials: Nude mice bearing SC xenografts of the human colon adenocarcinoma, HT29, were injected with a mixture of 125I- and 90Y-DTPA-labeled AUA1 monoclonal antibody, which recognizes an antigen expressed on the surface of the tumor cells. In addition, the effect of systemic ethylenediaminetetraacetic acid (EDTA) administration on 90Y-labeled antibody clearance, tumor uptake of antibody and bone accumulation of 90Y was studied in a nude mouse model of intraperitoneal cancer.

Construction, characterisation and kinetics of a single chain antibody recognising the tumour associated antigen placental alkaline phosphatase.

The murine monoclonal antibody H17E2 recognises placental alkaline phosphatase (PLAP), an antigen present in the human term placenta and also expressed by many tumours. The antibody is of value in both immunoscintigraphy and radioimmunotherapy in testicular and ovarian cancer. The small size of genetically engineered single chain antibodies (SCAs) should give diagnostic and therapeutic advantages of improved tumour penetration and increased blood clearance compared to IgG.

Targeted delivery of biologic and other antineoplastic agents.

This review summarizes several strategies under investigation for targeted delivery of antineoplastic agents to tumor cells, which avoids normal tissue damage. Monoclonal antibodies remain the molecules of choice for targeted therapy, and several improvements to immunotargeting are discussed. These improvements include the use of novel radioisotopes, cytokines, new linkers for chemotherapeutic drugs, more potent drugs, and improved immunotoxins.