Monoclonal antibodies in cancer treatment

Potential for Artifacts in Monitoring for the Detection of Tumor Associated Antigens (TAG-72 and CEA) in Serum from Patients Undergoing MAb-based Diagnostic and Therapeutic Protocols

The administration of murine monoclonal antibodies (MAbs) induces, in many patients, an immunological response represented by the development of human anti-mouse antibodies (HAMA). HAMA have been previously shown to interfere in some assays for the detection of CEA, as well as other non tumor related analytes. The present study was performed to determine whether the CA 72-4 assay is affected by the presence of HAMA, and to establish conditions capable of overcoming this artifact. Serum samples obtained from 8/9 patients entered into a therapeutic protocol using 131I-labeled MAb B72.3 showed the development of apparently high levels of TAG-72 during the clinical follow-up concurrent with the appearance of elevated titers of HAMA. Heat treatment at 90°C at pH 5.0 sodium acetate, previously reported as a method of abolishing HAMA interference without affecting CEA levels, resulted in a considerable loss of detectable TAG-72. However, treatment of these samples at 90°C in pH 6.5 Bis Tris abolished the artifact due to HAMA and resulted in the reversion of reported TAG-72 levels to those observed prior to any MAb administration.

As the use of murine M Abs, for both diagnostic and therapeutic applications continues to expand, the identification of this artifactual increase in reported antigen levels due to the development of HAMA has become an important factor in the use of tumor markers, e.g. TAG-72 and CEA, in the follow-up of carcinoma patients.

Radioimmunotherapy for pancreatic carcinoma using (131)I-labeled monoclonal antibody Nd2 in xenografted nude mice

We investigated the biodistribution, radiolocalization, and radioimmunotherapeutic potential of (131)I-labeled Nd2 in athymic nude mice bearing human pancreatic carcinoma xenografts. (131)I-Nd2 was accumulated at high levels in the tumor, in contrast to blood, liver, spleen, and other normal organs. The tumor was clearly delineated in scintigraphs. The volumes of tumors of mice injected with 7.4 MBq of (131)I-Nd2 were 80% less than those of tumors before injection of radiolabeled Nd2. Fibrous or vacuolar degeneration was seen in histological sections of tumors of 7-week-treated mice. The growth of tumors in mice treated with misonidazole, a hypoxic cell radiosensitizer, and then injected twice with 3.7 MBq of (131)I-Nd2 was suppressed over 7 weeks. Neither leucocytopenia nor thrombocytopenia was severe after injection of radiolabeled Nd2. Thus (131)I-labeled Nd2 may have clinical application in the radioimmunotherapy of pancreatic cancer.

Antibody directed enzyme prodrug therapy (ADEPT). A review of some theoretical, experimental and clinical aspects

The concept of generating cytotoxic agents from non-toxic prodrugs at tumour sites by antibody vectored enzyme introduces a wide range of opportunities. Various prodrug-enzyme combinations have been described and encouraging results reported in xenograft models. Whilst the mouse model is a valuable tool in this approach translation to the human patient may expose more complex issues. The objective of restricting drug action to tumour sites and thus allowing greatly increased cytotoxic action requires more precise restriction of enzyme activity to tumour sites than has been achieved with an antibody vector and natural clearance alone. Assisted clearance mechanisms have been found effective. Alternatively, or additionally, the difference between prodrug and active drug creates the opportunity to degrade active drug selectively in blood and thus protect normal tissues. In order to give more than one cycle of treatment it will be necessary for the antibody-enzyme conjugate to be nonimmunogenic or for the concurrent administration of immunosuppressive agents. A pilot scale clinical trial with a prototype prodrug indicated the feasibility of antibody directed enzyme prodrug therapy (ADEPT).

Imaging of ovarian cancer with radiolabelled monoclonal antibodies

This article presents the state of the art of immunoscintigraphy (IS) of ovarian cancer. We will review the monoclonal antibodies (MoAbs) used in clinical trials: (HMFG1/2, OC125, H317, H17E2, NDOG2 and 791T/36). We conclude that none of the afore mentioned MoAbs are clearly superior and that IS cannot yet replace laparotomy for the diagnosis of ovarian cancer but may have a role in the follow-up of ovarian cancer, in timing second-look surgery and assessing the response/TD treatment.

Characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA)

This study describes the characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA) to quantify murine monoclonal antibodies of all IgG isotypes. Two physical methods (transmission electron microscopy (TEM) and dynamic light scattering (DLS], were used to obtain information about particle size and morphology of the gold sols, but only with DLS antibody labelling could be detected. In addition, electrophoretic methods like agarose electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed also that antibody labelling was successful. The biological activity of the antibody gold conjugates was determined by using them in a SPIA and as an electrondense marker in an immunogold labelling procedure to visualize meningococcal surface exposed outer membrane proteins labelled with monoclonal antibodies. The SPIA was applicable to determine murine monoclonal antibodies of all IgG isotypes with a sensitivity of 20-80 ng/ml and a coëfficiënt of variation of 6.7 +/- 2.2%.

In vivo localization of a bispecific antibody which targets human T lymphocytes to lyse human colon cancer cells

A bispecific MAb was derived from the fusion of a hybridoma producing MAb CD3 with a hybridoma producing MAb L-DI (which is directed against a 41-kDa glycoprotein expressed in most gastro-intestinal and pancreatic carcinomas). Bispecific antibody molecules were isolated from parental antibody molecules by the use of hydroxylapatite-HPLC and shown to target human cytolytic T lymphocytes, irrespective of their original specificity, to specifically lyse human colon carcinoma cells. Localization studies in vivo using nude mice bearing human colon carcinoma xenografts showed significant accumulation of the HPLC-purified 125I-labelled bispecific antibodies into the tumor compared to 131I-labelled control CD3 antibody.

Review: the treatment of hepatocellular carcinoma

Surgical resection offers the only realistic hope of cure in hepatocellular carcinoma (HCC) but is usually not possible, either because the tumour is widespread throughout the liver at diagnosis, or because liver function is adversely affected by concomitant cirrhosis. The results of operation in early asymptomatic disease are, however, encouraging and efforts should be made to screen regularly the cirrhotic population at risk of HCC development. The prognosis for inoperable patients remains gloomy, though exciting new treatment methods exist which require extensive evaluation. An anthracycline given as single agent intravenous therapy is probably the current treatment of choice for inoperable patients, though only 20-30% will show a response. Intra-arterial therapy has not yet been convincingly shown to have any advantages over intravenous therapy. The evaluation of clinical trials in HCC would be made easier if response criteria were standardized and universally adopted, and if trials were properly controlled and of sufficient sample size to test adequately the hypothesis in question. This review deals only with the specific treatment of HCC. HCC prevention, the early diagnosis of HCC, and the relief of symptoms in HCC, though areas of obvious importance, are outside the scope of this review.

Anti-ovarian carcinoma anti-T3 heteroconjugates or hybrid antibodies induce tumor cell lysis by cytotoxic T-cells

In the perspective of therapeutic in vivo targeting for T-cell attack, the monoclonal antibody (MAb) MOv18, selected for its restricted reactivity with human ovarian carcinoma, and an anti-T3 MAb were used to produce heteroconjugate or hybrid antibodies derived by fusion of relevant hybridomas. Specificity and activity of bispecific MAbs were analyzed by solid-phase RIA, immunofluorescence and a 51Cr-release assay on the ovarian carcinoma cell line OVCA 432, which expresses the relevant tumor-associated antigen, and on several irrelevant tumor cell lines. Both reagents efficiently promoted, at picomolar concentration, target cell lysis by cytotoxic T-cell (CTL) clones. Although the pattern of tumor cell lines which were lysed was wider than that predicted by binding studies, further studies using a double-determinant immunoradiometric assay confirmed the specificity of MAb targeting. Analysis of reagents indicated that the hybrid MAb was superior to the heteroaggregate as far as purification recovery and storage stability were concerned. Besides CTL clones, peripheral blood lymphocytes could also be used as cytolytic effectors, provided that a suitable in vitro activation scheme was used.

Human monoclonal antibodies and monoclonal antibody multispecificity

The majority of human anti-tumour monoclonal antibodies (Mabs) isolated to date have been disappointing. Firstly, they react or cross react with intracellular cytoskeletal proteins or nuclear antigens and therefore are of limited value as blood borne agents. They are also generally of the IgM isotype and show relatively low intrinsic affinity for the primary epitope. Secondly, such Mabs can be generated from normal, non tumour bearing subjects at a frequency comparable to their production from tumour patients. This latter observation is true also for common autoantigens such as DNA and IgG since Mabs to these can also be generated from normal subjects in addition to autoimmune individuals. This article rationalises these observations in the context of the requirement for clinical use for human Mabs. It discusses the evidence that there is a potentially useful B cell response to be immortalised, and examines the consequences of the newly recognised phenomenon of monoclonal antibody multispecificity both on the methodology of their generation and on their subsequent use as imaging and therapeutic tools.

Evaluation of a method of production and purification of monoclonal antibodies for clinical applications

A procedure is described for the purification of monoclonal antibodies (Mab) from ascitic fluids, which meets the quality control required for in vivo applications of immunoglobulins (Ig) in man. Additional assays were performed to calculate viral and DNA content of the purified Mab. These studies are important to prevent the possible side effects, oncogenic events and virus-related diseases which could follow immunotherapy with Mab.