No abstract

Chronic transplant dysfunction (CTD) is

Previously, we demonstrated potent tumor cell-selective pro-apoptotic activity of scFv425:sTRAIL, a recombinant fusion protein comprised of EGFR-directed antibody fragment (scFv425) genetically fused to human soluble TNF-related apoptosis-inducing ligand (sTRAIL). Here, we report on the promising therapeutic systemic tumoricidal activity of scFv425:sTRAIL when produced by the replication-deficient adenovirus Ad-scFv425:sTRAIL. In vitro treatment of EGFR-positive tumor cells with Ad-scFv425:sTRAIL resulted in the potent induction of apoptosis of not only infected tumor cells, but importantly also of up to 60% of noninfected EGFR-positive tumor cells. A single intraocular injection of Ad-scFv425:sTRAIL in tumor-free nu/nu mice resulted in predominant liver infection and concomitant high blood plasma levels of scFv425:sTRAIL. These mice showed no sign of Ad-scFv425:sTRAIL-related liver toxicity. Identical treatment of mice with established intraperitoneal renal cell carcinoma xenografts resulted in rapid and massive tumor load reduction and subsequent long-term survival. Taken together, adenoviral-mediated in vivo production of scFv425:sTRAIL may be exploitable for systemic treatment of EGFR-positive cancer.

Multidrug resistance (MDR) of cancer cells is characterized by cross-resistance toward multiple chemotherapeutic agents. Several MDR mechanisms have been described, the best characterized of which is the overexpression of ATP binding cassette (ABC) drug transporter proteins such as P-glycoprotein (Pgp) and multidrug resistanceassociated protein 1 (MRP1) (1-3). These proteins function by decreasing the intracellular concentration of cytotoxic drugs. ABC proteins probably recognize these drugs in the membrane by virtue of their hydrophobic nature (4, 5). After recognition, they are either pumped out of the cell or translocated to the outer leaflet of the plasma membrane, from which they eventually diffuse in the surrounding fluid (6-8).Most ABC transporter-overexpressing MDR cell lines display changes in lipid composition compared with drugsensitive counterparts (9-12). Pgp and MRP1 are known to depend on the lipid environment for optimal functioning (13,14). In membrane model systems, the ATPase activity of both proteins is dependent on the close proximity of specific phospholipids, especially phosphatidylethanolamine (PE) (15)(16)(17)(18)(19)(20). Moreover, Pgp has a higher affinity for its substrates when the surrounding lipids are in the gel phase rather than in the liquid-crystalline phase (21). This gel phase occurs when lipids have a high degree of saturation, which enables them to pack tightly. This is also an important characteristic of cellular membrane microdomains (rafts) (22,23). These domains are enriched in sphingolipids (usually containing saturated fatty acids) and cholesterol and are characterized by insolubility in Abbreviations: ABC, ATP binding cassette; DIG, detergent-insoluble glycosphingolipid-enriched membrane domain; ESI-MS/MS, liquid chromatography-electrospray tandem mass