Intra-thecal treatment of leptomeningeal lymphoma with immunotoxin

Hyperuricaemia, Xanthine Oxidoreductase and Ribosome-Inactivating Proteins from Plants: The Contributions of Fiorenzo Stirpe to Frontline Research

The enzymes called ribosome-inactivating proteins (RIPs) that are able to depurinate nucleic acids and arrest vital cellular functions, including protein synthesis, are still a frontline research field, mostly because of their promising medical applications. The contributions of Stirpe to the development of these studies has been one of the most relevant. After a short biographical introduction, an overview is offered of the main results obtained by his investigations during last 55 years on his main research lines: hyperuricaemia, xanthine oxidoreductase and RIPs.

Flt3L and TK gene therapy eradicate multifocal glioma in a syngeneic glioblastoma model

The disseminated characteristics of human glioblastoma multiforme (GBM) make it a particularly difficult tumor to treat with long-term efficacy. Most preclinical models of GBM involve treatment of a single tumor mass. For therapeutic outcomes to translate from the preclinical to the clinical setting, induction of an antitumor response capable of eliminating multifocal disease is essential. We tested the hypothesis that expression of Flt3L (human soluble FMS-like tyrosine kinase 3 ligand) and TK (herpes simplex virus type 1-thymidine kinase) within brain gliomas would mediate regression of the primary, treated tumor mass and a secondary, untreated tumor growing at a distant site from the primary tumor and the site of therapeutic vector injection. In both the single-GBM and multifocal-GBM models used, all saline-treated control animals succumbed to tumors by day 22. Around 70% of the animals bearing a single GBM mass treated with an adenovirus expressing Flt3L (AdFlt3L) and an adenovirus expressing TK (AdTK + GCV) survived long term. Approximately 50% of animals bearing a large primary GBM that were implanted with a second GBM in the contralateral hemisphere at the same time the primary tumors were being treated with AdFlt3L and AdTK also survived long term. A second multifocal GBM model, in which bilateral GBMs were implanted simultaneously and only the right tumor mass was treated with AdFlt3L and AdTK, also demonstrated long-term survival. While no significant difference in survival was found between unifocal and multifocal GBM-bearing animals treated with AdFlt3L and AdTK, both treatments were statistically different from the saline-treated control group (p < 0.05). Our results demonstrate that combination therapy with AdFlt3L and AdTK can eradicate multifocal brain tumor disease in a syngeneic, intracranial GBM model.

Animal models of leptomeningeal cancer

Animal models are a critical tool for our understanding of pathogenic mechanisms and the development of therapeutic strategies. Since the 1970's, numerous syngeneic and allogeneic rodent models of leptomeningeal cancer have been developed; in this chapter, we present representative models and discuss their clinical and translational implications.

Treatment of neoplastic meningeal xenografts by intraventricular administration of an antiganglioside monoclonal antibody, 3F8

Leptomeningeal (LM) neoplastic metastases are painful, debilitating and inevitably lethal. Intrathecal (IT) anti-tumor antibodies may have therapeutic potential. We evaluated 3F8, an anti-G(D2) murine IgG(3) monoclonal antibody (MAb) in the treatment of human melanoma (SKMEL-1) and neuroblastoma (NMB7) xenografts in athymic rats. Both tumors were lysed efficiently in vitro by 3F8 in the presence of rat neutrophils or rat complement. Antibody-dependent cellular cytotoxicity (ADCC) was not augmented by recombinant human GM-CSF (rhGM-CSF), rhG-CSF, recombinant rat MIP-2 (rrMIP-2) or lipopolysaccharide (LPS). In vivo, continuous intraventricular administration of 3F8 and LPS prevented tumor engraftment, retarded tumor growth and eradicated 3-day-old established xenografts whereas 3F8 alone, LPS alone or F(ab)'(2) plus LPS had no or only marginal effects. Tumor establishment in brain was completely prevented in 36% of animals implanted with SKMEL-1 and 65% of animals implanted with NMB7. Twenty percent of established xenografts around the brain were eradicated but all animals had persistent tumor in the lumbosacral meninges despite treatment. Continuous intraventricular infusion of LPS produced a variable polymorphonuclear (PMN) pleocytosis that was dose-dependent. Continuous intraventricular infusion of 3F8 produced immunohistochemically detectable attachment to 86% of persistent brain deposits of tumor but <1% of spinal lumbosacral deposits. We conclude that regional therapy with anti-G(D2) MAb could target neutrophils to inhibit LM tumor growth. However, optimal activation and mobilization of neutrophils into the cerebrospinal fluid (CSF) and improved penetration of MAb to tumor sites remain critical variables.

Intrathecal therapy of leptomeningeal CEM T-cell lymphoma in nude rats with anti-CD7 ricin toxin A chain immunotoxin

We have established a new xenogeneic animal model of leptomeningeal metastasis (LM) by intracisternal inoculation of human CEM T-cell lymphoma into nude rats, and used it to evaluate the anti-lymphoma efficacy of an anti-CD7 ricin A chain immunotoxin (DA7). In vitro incubation with 2 microg/ml DA7 for 72 h inhibited CEM cells by 90% in a trypan blue exclusion assay. To establish its anti-lymphoma activity, one and four days after cisternal inoculation of 10(6) CEM cells, eight animals each were treated cisternally with 10 microg DA7 in 50 microl PBS or sham-treated with 50 microl PBS. Histopathologically, all eight sham-treated and five of eight DA7 treated animals showed typical features of LM with multilayers of tumor cells along the whole subarachnoid space and the ventricular walls, as well as subependymal and diffuse parenchymal tumor cell infiltration. Three DA7 treated animals were free of tumor. Two of these animals were asymptomatic long-term survivors (> 90 days). The third tumor-free animal suddenly died on day 51. Histology revealed viral myocarditis. Median symptom-free survival was 51 days (range 29-90+ days) in DA7 treated and 34 days (range 29-87 days) in sham-treated animals (p = 0.12, log-rank test). Histologically, no signs of neurotoxicity or systemic toxicity was found. However, DA7 treated animals showed a tendency to a slower weight increase on days 6-28 after tumor cell inoculation. Our results indicate that this model is useful in studying leptomeningeal seeding and intracisternal treatment of lymphoma. The demonstrated anti-tumor effect of DA7 treatment deserves further evaluation especially regarding the application of DA7 in early stages of LM from T-cell lymphoma.

Animal models of leptomeningeal metastasis

Animal models of leptomeningeal metastasis (LM) should give insight into pathophysiological mechanisms and allow to evaluate new treatments including their neurotoxicity. Syngeneic models use tumor cells of mouse, rat, rabbit or guinea pig origin. Allogeneic models usually rely on human tumor cells injected into nude mice or rats. A review of the literature revealed 2 (4) different glioma, 3 medulloblastoma, 3 (3) carcinoma, 3 (1) melanoma, 1 rhabdomyosarcoma, 2 (8) leukemia and 2 (2) non-Hodgkin's lymphoma allogeneic (syngeneic) models of LM. These models have been used to study the evolution of LM and to evaluate systemic or intrathecal chemotherapy, intrathecal immunotherapy (interleukin-2, interferon-beta, uncoupled, toxin- or radionuclide-conjugated antibodies), and recently gene therapeutic approaches. On the whole, pathophysiological, therapeutic and neurotoxic findings have been well transferable to the clinical situation. Therefore, it seems rational to preclinically test new treatments in an appropriate animal model of LM before using them in patients.

Evaluation of immunotoxins containing single-chain ribosome-inactivating proteins and an anti-CD22 monoclonal antibody (OM124): in vitro and in vivo studies

Immunotoxins were prepared with three ribosome-inactivating proteins (RIP), momordin, pokeweed antiviral protein from seeds (PAP-S) and saporin-S6, linked to the anti-CD22 monoclonal antibody OM124. These immunotoxins inhibited protein synthesis by CD22-expressing cell lines Daudi, EHM, BJAB, Raji and BM21 with IC50 (concentration causing 50% inhibition) ranging from < 5 x 10(-15) to 7.6 x 10(-11) M as RIP, and IC90 (concentration causing 90% inhibition) ranging from 5 x 10(-14) to 5 x 10(-8)M, with no effect on a CD22-negative HL60 cell line at the highest concentration tested (5 x 10[-8] M). Apoptosis was induced in sensitive cells. The formation of bone marrow colonies was inhibited by no more than 40% by the immunotoxins at concentrations up to 10(-9) M. Treatment with the immunotoxins, alone or in combination, significantly extended the survival time of mice bearing transplanted Daudi cells. A treatment with cyclophosphamide and OM124/saporin immunotoxin was particularly effective in SCID mice transplanted with a low number of cells (3 x 10[-6]), when 60% of the animals remained tumour-free.

Quantitative studies of monoclonal antibody targeting to disialoganglioside GD2 in human brain tumors

Iodine-131 3F8, a murine IgG3 monoclonal antibody that targets to GD2-bearing tumors, was administered intravenously to 12 patients with brain tumors. Six patients received 2 mCi (0.74 Bq) of 131I-3F8, five patients 10 mCi (3.7 Bq)/1.73 m2 of 131I-3F8, and one patient 2.6 mCi (0.96 Bq) of 124I-3F8, with no side-effects. Nine of 11 malignant gliomas and the single metastatic melanoma showed antibody localization, with the best tumor delineation on single-photon emission tomography (SPET) following 10 mCi (3.7 Bq)/1.73 m2 dose. No nonspecific uptake in the normal craniospinal axis was detected. There was no difference in the pharmacokinetics of low-dose versus the higher-dose antibody groups; plasma and total-body half-lives were 18 h and 49 h, respectively. Surgical sampling and time-activity curves based on quantitative imaging showed peak uptake in high-grade glioma at 39 h, with a half-life of 62 h. Tumor uptake at time of surgery averaged 3.5 x 10(-3) %ID/g and peak activity by the conjugate view method averaged 9.2 x 10(-3) %ID/g (3.5-17.8). Mean radiation absorption dose was 3.9 rad per mCi injected (range 0.7-9.6) or 10.5 cGy/Bq (range 1.9-26). There was agreement on positive sites when immunoscintigraphy was compared with technetium-99m glucoheptonate/diethylene triamine penta-acetic acid planar imaging, thallium-201 SPET, and fluorine-18 fluorodeoxyglucose positron emission tomography. Taken together, these data suggest that quantitative estimates of antibody targeting to intracranial tumors can be made using the modified conjugate view method.

In vivo efficacy of intrathecal transferrin-Pseudomonas exotoxin A immunotoxin against LOX melanoma

Neoplastic meningitis due to the dissemination of systemic cancer or primary central nervous system tumors through the cerebrospinal fluid carries a very poor prognosis. Current treatments for this disease are ineffective, and new therapeutic modalities such as immunotoxins may be beneficial. We created an animal model of human carcinomatous meningitis with LOX melanoma-derived tissue-culture cells in athymic rats for testing the efficacy of intrathecal therapy with transferrin-Pseudomonas exotoxin A (Tfn-PE) immunotoxin. An injection of 5 x 10(5) LOX cells into the intrathecal space through an indwelling catheter resulted in the reproducible development of lower-extremity paraplegia at 9.24 +/- 1.77 days because of focal deposits of tumor growth adjacent to the thoracic and lumbar spinal cord. A dose of 2.5 or 5 micrograms of intrathecal Tfn-PE immunotoxin was neurotoxic and resulted in the deaths of 8 of 10 animals within 24 hours. Histological evidence of central nervous system damage was seen as hemorrhagic degeneration around the central canal or a pathological cleft at the level of the cervical spinal cord. Because no neurotoxicity was seen with 1 microgram of intrathecal Tfn-PE immunotoxin, this dose was administered in treatment experiments. Twenty-four hours after the intrathecal instillation of LOX cells, 10 animals received intrathecally either 1 microgram of Tfn-PE or phosphate-buffered saline with 0.1% human serum albumin (control group).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunotoxin therapy of leptomeningeal neoplasia

Malignant tumors of the central nervous system can result from metastatic dissemination of a variety of cancers. Percutaneous intracisternal injection of an anti-idiotype monoclonal antibody (M6) ricin immunotoxin was shown to be moderately effective in prolonging the survival of tumor bearing animals supporting the use of immunotoxins for the treatment of central nervous system neoplasia (Zovickian J and Youle R.J. J. Neurosurg 68: 767, 1988). This report describes a method that significantly improves the survival of immunotoxin treated Strain 2 guinea pigs in a syngeneic animal model of leptomeningeal neoplasia. Strain 2 guinea pigs, implanted with subarachnoid catheters, received three courses of treatment with an (M6)-intract ricin immunotoxin following intracisternal inoculation of L2C leukemia tumor cells. Animals were treated with three to four micrograms of immunotoxin in three divided doses. This was found to be less toxic and more effective than single bolus administration of immunotoxin. These results demonstrate that a permanent indwelling catheter in this animal model facilitates multiple dose delivery of immunotoxin therapy allowing the assessment of various treatment schedules and the achievement of enhanced therapeutic effect. Furthermore, these results support the continued evaluation of immunotoxins for the treatment of central nervous system neoplasia.