Angiogene Pharmaceuticals Ltd.

The efficacy of approaches in which vascular disrupting agents (VDA) are used in combination with conventional chemotherapy and/or radiation therapy in the treatment of cancer might be improved if there were a better understanding of the cellular and molecular changes induced in normal and malignant cells as a result of VD A exposure. Toward this goal, murine endothelial cells were treated in vitro with ANG501, a novel stilbene VDA developed in our laboratory, and alterations in gene expression determined by genome-wide microarray analysis and subsequently confirmed by Western blot analysis. Among the genes that were shown to be induced upon brief exposure to non-cytotoxic doses of ANG501 were several involved in the control of cell cycle progression and apoptosis, including p21Wafland the heat shock/stress proteins hsp25, hsp70 and anti-B-crystallin. Reflecting such induction, functional studies confirmed that normal cell cycling is temporarily inhibited following treatment with ANG501 such that the majority of cells accumulate at the radiation-sensitive G2/M phase of the cell cycle at 6 hr. The effects were transient and by 24 hr normal cell cycling had largely resumed. Combination experiments confirmed that endothelial cells treated 6 hr previously with ANG501 were more readily killed by radiation. Importantly, significant effects were evident at clinically relevant radiation doses. Taken together these findings emphasize the need to consider the radiosensitizing activity of VD As when developing therapies in which these promising compounds are used in combination with radiation.

The extracellular matrix glycosaminoglycan hyaluronan plays a key role in the development and pathogenesis of malignant disease. Reflecting its functional importance, the molecule is expressed at greatly elevated levels within many solid tumors. Although little explored, differences in the level of hyaluronan present in normal and malignant tissues could potentially be exploited to more effectively target gene therapy to tumor sites in vivo. As a first step toward this goal, we describe here a family of chimeric proteins in which the extracellular ligand-binding domain of the hyaluronan receptor CD44 is fused in-frame to the cytoplasmic “death domain” of the pro-apoptotic protein Fas. Although these chimeric proteins can be stably expressed on the surface of transduced tumor cells in the absence of hyaluronan, upon interaction with the ligand, apoptosis is rapidly induced. Both exogenous and endogenous tumor produced hyaluronan can function as triggers, dramatically reducing clonogenic potential. Together, these studies help validate a broadly applicable gene therapy approach in which the presence of particular multivalent ligands within the tumor microenvironment can be exploited for therapeutic gain.

Nitrothienylprop-2-yl ether formation on the 3′-phenolic position of combretastatin A-4 (1) abolishes the cytotoxicity and tubulin polymerization-inhibitory effects of the drug. 5-Nitrothiophene derivatives of 1 were synthesized following model kinetic studies with analogous coumarin derivatives, and of these, compound 13 represents a promising new lead in bioreductively targeted cytotoxic anticancer therapies. In this compound, optimized gem-dimethyl α-carbon substitution enhances both the aerobic metabolic stability and the efficiency of hypoxia-mediated drug release. Only the gem-substituted derivative 13 released 1 under anoxia in either in vitro whole-cell experiments or supersomal suspensions. The rate of release of 1 from the radical anions of these prodrugs is enhanced by greater methyl substitution on the α-carbon. Cellular and supersomal studies showed that this α-substitution pattern controls the useful range of oxygen concentrations over which 1 can be effectively released by the prodrug. [Mol Cancer Ther 2006;5(11):2886–94]