Hydrophobic Derivatives of Glycopeptide Antibiotics as Inhibitors of Protein Kinases.

As key regulators of cell signaling, protein kinases (PKs) are attractive targets for therapeutic intervention in a variety of diseases. Herein, we report for the first time the inhibitory activity of polycyclic peptides, particularly, derivatives of glycopeptide antibiotics teicoplanin and eremomycin, against a panel of 12 recombinant human protein kinases and two protein kinases (CK1 and CK2) isolated from rat liver. Several of the investigated compounds inhibited various PKs with IC50 values below 10 µM and caused >90% suppression of the enzyme activity at 10 µM concentration. Kinetic analysis of the protein kinase CK2α inhibition by the teicoplanin aglycon analogue (7) demonstrated the non-competitive mechanism of inhibition (with regard to ATP). Interestingly, the inhibitory activity of some investigated compounds correlated with the earlier described antiviral activity against HIV, HCV, and other corona- and flaviviruses.

A new liposomal formulation of Gemcitabine is active in an orthotopic mouse model of pancreatic cancer accessible to bioluminescence imaging.

Despite its rapid enzymatic inactivation and therefore limited activity in vivo, Gemcitabine is the standard drug for pancreatic cancer treatment. To protect the drug, and achieve passive tumor targeting, we developed a liposomal formulation of Gemcitabine, GemLip (Ø: 36 nm: 47% entrapment). Its anti-tumoral activity was tested on MIA PaCa-2 cells growing orthotopically in nude mice. Bioluminescence measurement mediated by the stable integration of the luciferase gene was employed to randomize the mice, and monitor tumor growth. GemLip (4 and 8 mg/kg), Gemcitabine (240 mg/kg), and empty liposomes (equivalent to 8 mg/kg GemLip) were injected intravenously once weekly for 5 weeks. GemLip (8 mg/kg) stopped tumor growth, as measured via in vivo bioluminescence, reducing the primary tumor size by 68% (SD +/- 8%; p < 0.02), whereas Gemcitabine hardly affected tumor size (-7%; +/- 1.5%). In 80% of animals, luciferase activity in the liver indicated the presence of metastases. All treatments, including the empty liposomes, reduced the metastatic burden. Thus, GemLip shows promising antitumoral activity in this model. Surprisingly, empty liposomes attenuate the spread of metastases similar to Gemcitabine and GemLip. Further, luciferase marked tumor cells are a powerful tool to observe tumor growth in vivo, and to detect and quantify metastases.

Anti-inflammatory properties of the protein kinase C inhibitor, 3-[1-[3-(dimethylamino)propyl]-1H-indol-3-yl]-4-(1H-indol-3-yl)-1H- pyrrole-2,5-dione monohydrochloride (GF109203X) in the PMA-mouse ear edema model.

Protein kinase C (PKC) mediates a number of intracellular signal transduction pathways implicated in the pathogenesis of inflammation, including phospholipase A2-dependent arachidonic acid release and eicosanoid production. Recent studies demonstrate that the PKC inhibitor GF109203X significantly reduces a number of inflammatory processes resulting from PKC activation by the topical application of phorbol myristate acetate (PMA) to mouse ears. In this model, GF109203X significantly reduced edema at doses similar to the PKC inhibitor staurosporine, and more effectively than indomethacin, zileuton, or sodium meclofenamate. Histological and biochemical analysis of biopsies from control and drug-treated ears revealed a marked reduction in edema, infiltrating neutrophils, and levels of the neutrophil-specific marker, myeloperoxidase, in GF109203X-treated mice. Prostaglandin E2 levels were also reduced in ears treated with GF109203X. These data suggest that GF109203X is an effective antiinflammatory agent as evaluated in the PMA model of edema, and implicates PKC as a potential target in the development of novel anti-inflammatory agents.