Please use this identifier to cite or link to this item:
Title: Study of an interleukin-2 immunoconjugate as a novel tumor vasoactive agent in animal models
Authors: Cheung, Wai-kwan
Degree: M.Phil.
Issue Date: 2003
Abstract: The elevated levels of the HER2/neu protein in 60% of patients with ductal carcinoma in situ and in 30% of patients with invasive breast cancer make this oncogene product an attractive target for tumor-specific therapeutic agents. Despite some successes to date, vascular inaccessibility and tumor heterogeneity are two main factors that hindered the efficacy of anti-HER-2 antibody therapy. There is ample evidence suggesting that recombinant interleukin-2 (rIL-2) has profound antitumor properties, but was limited by its severe systemic toxicity known as vascular leakage syndrome (VLS). A fusion protein H520C9sFv-rhIL-2 has been constructed by combining the humanized VH and VLportions of a murine monoclonal antibody 520C9 specific for human HER2 with human rIL-2 to deliver effective concentration of IL-2 to HER2 positive tumors whilst avoiding toxic effects on normal tissues. In this study in vitro characteristics of the H520C9sFv-rhIL-2 were investigated. Western blot of partially purified conditioned medium from 293 cells transfected with the cDNA of the H520C9sFv-rhIL-2 revealed one major protein band with a molecular weight of 45 kDa, indicating that the fusion protein was expressed in the transfected 293 cells. The H520C9sFv-rhIL-2 was shown to preserve both immuno-stimulatory activities of IL-2 as measured by an IL-2 dependent CTLL2 cell proliferation assay and antigen binding specificity against HER2 positive SKOV3 and B16/neu cells. These in vitro results have stimulated interest in the in viva application of the H520C9sFv-rhIL-2. Present results demonstrated that a single intravenous dose of H520C9sFv-rhIL-2 to mice bearing HER2 positive tumors could preferentially increase the permeability of blood vessels in the tumors in a time- and dose-dependent manner. Using C57/BL mice bearing B16/neu s.c. tumors as a model, 18 ug of H520C9sFv-rhIL-2 and 24 h post injection of a vascular permeability tracer resulted in maximal tumor: nontumor uptake ratios of the tracer. Compared to a saline injection control group, the tumor: nontumor uptake ratios in bone, blood, kidney, lung, muscle and spleen ranged from 2.1 to 12.2. Nine ug of H520C9sFv-rhIL-2 only resulted in 4.5-fold and 2.3-fold increase respectively for tumor: bone and tumor: muscle uptake ratios when compared to the saline group 24 h post tracer injection. At 12-h and 72-h post tracer injection, no significant difference in tumor: nontumor uptake ratios was observed between the 9 ug H520C9sFv-rhIL-2 group and the saline group. Some fatality was observed at 18 ug dose of H520C9sFv-rhIL-2. Using nude mice carrying SKOV3 s.c. tumors as another model, a single intravenous dose of 9 ug H520C9sFv-rhIL-2 could not preferentially increase the permeability of blood vessels in the tumors 24 h post injection of a vascular permeability tracer, although a single intra-tumor dose of 9 ug of H520C9sFv-rhIL-2 could significantly increase tumor: nontumor uptake ratios for bone, kidney and spleen relative to a saline injection group. Although the mechanisms underlying IL-2 mediated VLS have not been investigated in detail in this study, present results suggest that at least one of the mechanisms depends on T cells. Another mechanism does not depend on T cells because vascular leak could be induced in the athymic nude mice lacking functional T cells by intra-tumoral injection of the fusion protein. Taken together, these encouraging in vitro and in vivo results of the H520C9sFv-rhIL-2 suggest that this fusion protein might provide a good approach to selectively increasing the permeability of tumor vasculature. It is hoped that this will translate into further investigation into its clinical application.
Subjects: Hong Kong Polytechnic University -- Dissertations
Interleukin 2 -- Therapeutic use
Antibody-toxin conjugates
Tumors -- Adjuvant treatment
Pages: xxii, 197 leaves : col. ill.; 30 cm
Appears in Collections:Thesis

Show full item record

Page views

Last Week
Last month
Citations as of Sep 24, 2023

Google ScholarTM


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.