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We have recently described a novel cyclic peptide inhibitor CTTHWGFTLC (CTT) for matrix metalloproteinases (MMP)-2 and MMP-9, also called type IV collagenases or gelatinases (E. Koivunen et al., NAT: BIOTECHNOL:, 17: 768-774, 1999). As indicated by its amino acid composition, CTT is hydrophobic, and its partitioning into phospholipid films could be verified by the monolayer technique. Augmented fluorescence emission anisotropy (from 0.064 to 0.349) and reduced collisional quenching by I(-) of the Trp residue in CTT was evident in the presence of unilamellar phosphatidylcholine/phosphatidylethanolamine liposomes, revealing the association of CTT with the lipid bilayers. Gelatinases are potential targets of therapeutic intervention in cancer, and inhibitors of these enzymes can prevent tumor progression in animal models. CTT enhanced 3- to 4-fold the cellular uptake of liposome-encapsulated water-soluble fluorescent marker, rhodamine B by gelatinase-expressing cells. Gelatinase targeting seems to be essential, as modified peptides that were less potent gelatinase inhibitors were also less efficient in promoting the cellular uptake of liposomes. Augmented killing ( approximately 4-fold) of U937 leukemia and HT1080 sarcoma cells was obtained by the CTT-enhanced delivery of Adriamycin-containing liposomes, compared with control liposomes administered without the peptide. These results suggest a novel type of utility for small gelatinase inhibitors in targeted cancer therapy.

Cyclosporin A (CsA) is a highly hydrophobic drug used to prevent graft rejection after organ transplantation. Interactions of CsA with phosphatidylcholine as well as with binary mixtures containing phosphatidylcholine and cholesterol were investigated by measuring the penetration of CsA into lipid monolayers at an air/water interface, by differential scanning calorimetry, and by imaging with fluorescence microscopy the effects of CsA on the lateral distribution of a fluorescent probe, 1-palmitoyl-2-(N-4-nitrobenz-2-oxa-1, 3-diazol)aminocaproyl-phosphocholine, in monolayers. Film penetration studies revealed the association of CsA with lipids to be a biphasic process. Cholesterol diminished the intercalation of CsA into the monolayer at surface pressures of >19 mN/m. CsA broadened the main transition of dimyristoylphosphatidylcholine (DMPC)/beta-cholesterol (10:1, mol/mol) multilamellar vesicles. The behavior of the transition enthalpy was more complex; the behavior of DMPC/beta-cholesterol multilamellar vesicles in the XCsA of 0 to 0.1 showed at most ratios a increase, but several well distinct dips were observed. The results are interpreted in terms of regular structures in tertiary alloy. Influence of CsA on lateral organization could be verified for lipid domains observed by fluorescence microscopy of lipid monolayers. More specifically, CsA altered the distribution of 1-palmitoyl-2-(N-4-nitrobenz-2-oxa-1, 3-diazol)aminocaproyl-phosphocholine in a dipalmitoylphosphatidylcholine film and in DPPC/beta-cholesterol (88:10, mol/mol) mixtures in a manner that suggests that CsA partitions into the boundaries between fluid and gel domains. To our knowledge, this constitutes the first demonstration of a change in lipid domain morphology to be induced by a drug molecule.