Tumor vasculature‐targeted delivery of tumor necrosis factor‐α*

Abstract

BACKGROUND: Recently, considerable efforts have been directed toward antivascular therapy as a new modality to treat human cancers. However, targeting a therapeutic gene of interest to the tumor vasculature with minimal toxicity to other tissues remains the objective of antivascular gene therapy. Tumor necrosis factor‐α (TNF‐α) is a potent antivascular agent but has limited clinical utility because of significant systemic toxicity. At the maximum tolerated doses of systemic TNF‐α, there is no meaningful antitumor activity. Hence, the objective of this study was to deliver TNF‐α targeted to tumor vasculature by systemic delivery to examine its antitumor activity. METHODS: A hybrid adeno‐associated virus phage vector (AAVP) was used that targets tumor endothelium to express TNF‐α (AAVP‐TNF‐α). The activity of AAVP‐TNF‐α was analyzed in various in vitro and in vivo settings using a human melanoma tumor model. RESULTS: In vitro, AAVP‐TNF‐α infection of human melanoma cells resulted in high levels of TNF‐α expression. Systemic administration of targeted AAVP‐TNF‐α to melanoma xenografts in mice produced the specific delivery of virus to tumor vasculature. In contrast, the nontargeted vector did not target to tumor vasculature. Targeted AAVP delivery resulted in expression of TNF‐α, induction of apoptosis in tumor vessels, and significant inhibition of tumor growth. No systemic toxicity to normal organs was observed. CONCLUSIONS: Targeted AAVP vectors can be used to deliver TNF‐α specifically to tumor vasculature, potentially reducing its systemic toxicity. Because TNF‐α is a promising antivascular agent that currently is limited by its toxicity, the current results suggest the potential for clinical translation of this strategy. Cancer 2009. Published 2008 by the American Cancer Society.

Self-targeting of TNF-releasing cancer cells in preclinical models of primary and metastatic tumors

“…Such limitations may be partially overcome in the case of TNF and IFNγ by a liganddirected strategy based on cytokine fusion with peptides or antibodies selective for unique surface receptors on tumor endothelial or epithelial cells (12)(13)(14)(15)17). However, administration of targeted TNF or IFNγ close to the maximum tolerated dose still leads to systemic activation of counterregulatory mechanisms that reduce their potential anticancer activity (12).…”

“…To address this hypothesis experimentally, we engineered murine mammary adenocarcinoma, melanoma, and lung carcinoma cells to produce and release tumor necrosis factor alpha (TNF), a cytokine that damages the tumor vascular endothelia and has anticancer activity (9-11). The rationale for choosing this cytokine is based on our previous work that demonstrated ligand-based delivery of extremely low concentrations of TNF to tumor blood vessels markedly inhibits tumor growth in various xenograft (12)(13)(14) experimental mouse tumor models, and in a variety of native tumors in pet dogs (15). We show that systemic administration of several types of TNF-expressing cancer cells in syngeneic and nonsyngeneic tumor-bearing mice inhibits the growth of primary and metastatic cancers.…”

AAVP displaying octreotide for ligand-directed therapeutic transgene delivery in neuroendocrine tumors of the pancreas

“…Flow cytometry was used to demonstrate SSTR2 expression. AAVP activity in NET cells was evaluated using cell binding (24,25), internalization (45), and transgene expression (6,23) assays. Men1 transgenic mice (29) were studied for AAVP homing, human TNF expression (5-7), antitumor activity (34), and survival after treatment.…”

“…3C). AAVP particles are commonly identified in organs of the mononuclear phagocyte system, or reticuloendothelial system (RES), including the spleen, liver, and kidneys, and represents the long-recognized transient, nonspecific retention of particle processing, degradation, and excretion in vivo (6,31,32).…”

“…To this end, bacteriophage (phage)-based vectors are attractive, because ligand peptide motifs can be displayed on the pIII coat protein to allow viral binding to and internalization into target cells in vitro and in vivo (1), and the phage can be genetically modified to deliver gene products that kill tumor cells (2)(3)(4)(5)(6)(7). In previous work, we combined phage and adeno-associated virus (AAV) to form a hybrid AAV/phage (termed AAVP) vector that enables superior ligand-directed delivery and cellular transduction of transgenes as a targeted platform (2).…”