Quantitative and qualitative effects of experimental radioimmunotherapy on tumor vascular permeability.

Localization of radiolabeled antibodies in the perivascular space of tumors resulted in morphological changes in blood vessel structure and physiological changes in tumor vessel function. Vessel diameter decreased by day 14 and was associated with a significant decline in vascular volume (VV). Upon recovery of VV, the basement membrane surrounding the endothelium had thickened.

Targeting of xenografted pancreatic cancer with a new monoclonal antibody, PAM4.

We have examined the ability of murine monoclonal antibody PAM4, directed against a pancreatic cancer-derived mucin, to target human pancreatic cancers carried as xenografts in athymic nude mice. Four tumor lines were used representing the range of expected differentiation; CaPan1, AsPc1, Hs766T, and BxPc3. In each case tumor uptake of PAM4 (range, 21-48% injected dose/g on day 3) was significantly higher than concomitantly administered, nonspecific, isotype-matched Ag8 antibody (range, 3.

The fate of antibodies and their radiolabels bound to tumor cells in vitro: the effect of cross-linking at the cell surface and of anti-idiotype antibodies.

In order to obtain rapid blood clearance of circulating antibodies (Ab) at a desired time, cross-linking reagents such as second Ab are often employed. Such reagents will generally bind to Ab located at the tumor site as well as free Ab, and we therefore investigated whether the cross-linking of Ab bound to the surface of tumor cells affects the processing of those Ab. Cross-linking was induced in various ways: a polyclonal second Ab [rabbit anti-(mouse IgG)], a monoclonal rat anti-(mouse IgG constant region) Ab, and streptavidin used in conjunction with a biotinylated first Ab.

Immunoscintigraphy of Pneumocystis carinii pneumonia in AIDS patients.

Unlabelled: The diagnosis of Pneumocystis carinii pneumonia (PCP) currently relies upon cytological demonstration of the organism in sputum or bronchoscopy specimens. The purpose of this study was to develop a radiolabeled monoclonal antibody (Mab) against Pneumocystis carinii (P. carinii) and to evaluate its use for imaging PCP.

The processing and fate of antibodies and their radiolabels bound to the surface of tumor cells in vitro: a comparison of nine radiolabels.

Unlabelled: Processing radiolabeled degradation products is the key factor affecting retention of antibodies within the cell. In this study, we have analyzed the processing of antibodies labeled in nine different ways.

Methods: Antibodies were labeled with three different radioisotopes and seven different forms of 125I.

Characterization of monoclonal antibody PAM4 reactive with a pancreatic cancer mucin.

A monoclonal antibody (MAb), PAM4, having reactivity with pancreatic carcinoma has been developed. PAM4 is an IgG1 immunoglobulin produced by immunization of mice with mucin purified from the xenografted RIP1 human pancreatic carcinoma. An immunohistochemical study of normal adult tissues showed the PAM4 reactive epitope to be restricted to the gastrointestinal tract and absent from normal pancreas.

Internalization and intracellular processing of an anti-B-cell lymphoma monoclonal antibody, LL2.

The successful clinical experience with antibody LL2 (an IgG2a, anti-B-cell lymphoma antibody) in radioimmunodetection and radioimmunotherapy suggests that this antibody may have potential as a carrier of cytotoxic agents. The internalization, cellular trafficking, and catabolism of this antibody in target human Burkitt lymphoma cells (Raji) were investigated. Internalization of intact antibody as well as of the F(ab')2 and Fab' fragments was detected by an FITC-labeled anti-mouse second antibody probe, and evaluated by fluorescence microscopy.

Phase I clinical evaluation of a new murine monoclonal antibody (Mu-9) against colon-specific antigen-p for targeting gastrointestinal carcinomas.

Background: Colon-specific antigen-p is a tumor-associated antigen present in approximately 60% of colorectal cancers. Preclinical studies have shown that the murine monoclonal antibody Mu-9 has excellent tumor-targeting abilities; therefore, clinical studies were initiated.

Methods: The immunoglobulin G and F(ab')2 were radiolabeled with 131I and administered to 13 and 12 patients, respectively, with advanced gastrointestinal cancer (colon, rectal, and pancreatic) for radioimmunodetection or radioimmunotherapy.

Comparative biodistribution and radioimmunotherapy of monoclonal antibody RS7 and its F(ab')2 in nude mice bearing human tumor xenografts.

Background: RS7 is a murine monoclonal antibody immunoglobulin G1 with pan-carcinoma reactivity, which was raised against human squamous cell carcinoma of the lung. To optimize the use of monoclonal antibody RS7 as a carrier of radionuclides for tumor targeting and therapeutic applications, whole RS7 immunoglobulin G and its F(ab')2 fragment were radiolabeled, and their biodistribution and effectiveness as radioimmunotherapeutic agents in nude mice bearing established human tumor xenografts were evaluated. The contributions of the tumor model, monoclonal antibody form (fragment vs.

Processing of antibody-radioisotope conjugates after binding to the surface of tumor cells.

Background: Previous experiments indicated that most antibodies binding to cell surface antigens are internalized gradually and degraded within lysosomes, with a half-life of degradation of approximately 1 day, for most antibodies. The research discussed in this article extended our studies to eight additional antibodies reacting with six different antigens, including three antigens anchored in the membrane by glycosyl-phosphatidylinositol. The authors also tested antibodies labeled with 111indium, as well as 125iodine, to determine whether different radiolabels would be processed differently.

Cytokine intervention permits dose escalation of radioantibody. An analysis of myelostimulation by bolus versus continuous infusion of IL-1/GM-CSF.

Background: The authors recently reported that a 12-day schedule (beginning 3 days before radioantibody treatment) of twice-daily dosing of rH-IL-1 (1 x 10(3) U/dose) and rM-GM-CSF (0.5 micrograms/dose) can reduce the magnitude and duration of radioantibody-induced myelosuppression, thereby permitting a 25-30% increase in the dose of radioantibody that can be administered without the dose proving lethal. In an effort to further reduce toxicity and escalate the tolerated dose, the authors altered the method of administration of cytokines from daily bolus dosing to continuous infusion by implantable osmotic pumps.

New developments in monoclonal antibodies for cancer detection and therapy.

Monoclonal antibodies have provided clinicians with an intriguing, target-specific approach to cancer management. Used alone or conjugated with drugs, toxins, or radionuclides, monoclonal antibodies have been shown to be useful in the detection and/or treatment of several cancers. Recent advances, such as the development of "humanized" antibodies, promise to increase their effectiveness even more.

Comparison of equitoxic radioimmunotherapy and chemotherapy in the treatment of human colonic cancer xenografts.

The therapeutic efficacy of 5-fluorouracil (5-FUra; 0.6 mg/day x 5 days) + leucovorin (LV; 1.8 mg/day x 5 days) and of 131I-labeled MN-14 anticarcinoembryonic antigen IgG (275 microCi single dose) was evaluated in size-matched (0.

Characterization of cluster 13: the epithelial/carcinoma antigen recognized by MAb RS7.

Cluster 13 was defined by 2 independently derived murine monoclonal antibodies (MAbs), RS7 (IgG1) and MR54 (IgG2a), which were raised against human squamous-cell carcinoma of the lung and a human ovarian-carcinoma cell line, respectively. Immunologic and biochemical evidence demonstrated that RS7 and MR54, as well as 2 additional MAbs, MR6 (IgG2a) and MR23 (IgG1), generated in the same fusion as MR54, recognize the same antigen, a 46- to 48-kDa glycoprotein. Evaluation of the expression of antigen on the surface of tumor cell lines, Western blotting analyses, competitive binding studies, and double-determinant ELISA assays, support this conclusion.

Specificity and properties of MAb RS7-3G11 and the antigen defined by this pancarcinoma monoclonal antibody.

The murine monoclonal antibody (MAb) RS7-3G11 is an IgG1 with pancarcinoma reactivity, which has been raised against human squamous-cell carcinoma of the lung. Immunoperoxidase staining of frozen tissue sections demonstrated that the antigen defined by RS7-3G11 is present in tumors of the lung, stomach, bladder, breast, ovary, uterus and prostate. The rate and extent of internalization of RS7-3G11 into Calu-3, an adenocarcinoma of the lung cell line, was investigated using unconjugated MAb, followed by fluorescence labelling, and by binding 125I-RS7-3G11 followed by acid removal of surface-bound antibody.

Re-evaluation of the concept of functional affinity as applied to bivalent antibody binding to cell surface antigens.

Although it is recognized that the bivalent binding of an antibody to a multivalent antigen cannot be characterized by true affinity, "functional affinity" is frequently determined. "Functional affinity" is calculated by the same methods used for true affinity, and is presumed to have similar biological significance. The data presented herein demonstrate, for IgG antibodies binding to cell surface antigens, that "functional affinity" does not adequately describe the interactions that occur.

Epitope specificity of the anti-(B cell lymphoma) monoclonal antibody, LL2.

LL2 is a murine monoclonal antibody IgG2a reactive with B cells and non-Hodgkin's B-cell lymphoma, which, in a radioiodinated form, induces responses in lymphoma patients [Goldenberg et al. (1991) J Clin Oncol 9:548-564]. In this report we identify LL2 as a member of the CD22 cluster.

An extended primer set for PCR amplification of murine kappa variable regions.

The design and successful usage of an extended primer set for the PCR amplification of murine variable kappa light chain sequences from mouse hybridomas are described. Since some of these primer pairs also amplify the endogenous SP2/0 aberrant light chain sequence, strategies to distinguish the irrelevant SP2/0 from the sequence of interest are also provided.

Structure and binding properties of monoclonal antibodies to core histones from autoimmune mice.

Histones are frequent targets of self-reactive antibodies during autoimmune syndromes. We report the specificities and V region genes of three IgG anti-histone MAbs obtained from autoimmune mice. Each of the MAbs, named LG2-1, LG2-2 and BWA3, is directed against a different determinant located in the basic amino-terminal domain of core histones.

The specificity of alternative complement pathway-mediated lysis of erythrocytes: a survey of complement and target cells from 25 species.

Sera from 20 species of mammals were tested for their ability to lyse erythrocytes from 18 species of mammals and birds by the alternative complement pathway. Erythrocytes were not lysed by homologous complement, with one minor exception, but all erythrocytes tested were lysed by at least one complement source, and all sera tested except that of the horse lysed at least one type of erythrocyte. Control experiments indicated that lysis was via the alternative complement pathway and that antibodies were not involved.

New imaging techniques in gastrointestinal cancer.

Impressive advances in both anatomic and functional imaging of gastrointestinal tumors have been made in recent years, with several interesting studies appearing this past year. Increasingly, different imaging modalities have been used in combination and have shown complementation and improved accuracy. Improvements in detecting and defining local versus extended sites of cancer in various gastrointestinal organs have been made by conventional methods and by newer functional tests, including positron-emission tomography, receptor scintigraphy, and radioimmunodetection.

Monoclonal antibodies in cancer detection and therapy.

Anticancer antibodies have had a long history in the management of cancer, with major applications having been shown in the immunohistochemistry and immunoassay of tumor-associated antigen markers. With the advent of hybridoma-derived monoclonal antibodies, attempts to use these more reproducible reagents in vivo for cancer detection and therapy have intensified. Radiolabeled monoclonal antibodies appear to be gaining a role in the management of cancer by means of imaging methods to detect sites of increased radioactivity, and several products have been developed and tested clinically.

The coming of age of cancer radioimmunoconjugates.

Great progress in imaging and therapy with radioimmunoconjugates was discussed at the fourth conference on radioimmunodetection and radioimmunotherapy of cancer. Monoclonal antibody-based cancer imaging agents are awaiting marketing approval and newer, potentially improved forms are in development. Tumor responses to radioimmunoconjugates are also being reported in increasing numbers, this is especially so with radiosensitive tumors and in regional or direct applications.

Colorectal cancer imaging with iodine-123-labeled CEA monoclonal antibody fragments.

This prospective, randomized multicenter study in 62 patients was designed to evaluate the efficacy and safety of radioimmunodetection (RAID) with 123I-labeled fragments, F(ab')2 and Fab', of IMMU-4, an anti-CEA monoclonal antibody (Immu-RAID-CEA). It was found that ImmuRAID-CEA was safe and disclosed colorectal cancer sites at least 1 cm in size. The positive predictive value by lesions was 77% initially, and increased to 91% after 7 mo of follow-up.