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The HIV-1 encoded apoptogenic protein Vpr induces mitochondrial membrane permeabilization (MMP) via interactions with the voltage-dependent anion channel (VDAC) and the adenine nucleotide translocator (ANT). We have designed a peptide, TEAM-VP, composed of two functional domains, one a tumor blood vessel RGD-like 'homing' motif and the other an MMP-inducing sequence derived from Vpr. When added to isolated mitochondria, TEAM-VP interacts with ANT and VDAC, reduces oxygen consumption and overcomes Bcl-2 protection to cause inner and outer MMP. TEAM-VP specifically recognizes cell-surface expressed a V b 3 integrins, internalizes, temporarily localizes to lysosomes and progressively co-distributes with the mitochondrial compartment with no sign of lysosomal membrane permeabilization. Finally TEAM-VP reaches mitochondria of angiogenic endothelial cells to induce mitochondrial fission, dissipation of the mitochondrial transmembrane potential (DW m ), cytochrome c release and apoptosis hallmarks. Hence, this chimeric peptide constitutes the first example of a virus-derived mitochondriotoxic compound as a candidate to kill selectively tumor neo-endothelia. Within the integrin family, a V b 3 receptors are considered to be an important target for anticancer therapy being upregulated in certain invasive tumors.1 a V b 3 recognizes a specific consensus sequence, an RGD motif, which is present in a number of extracellular matrix proteins like vitronectin, fibronectin, fibrinogen and thrombospondin.2 RGD-containing peptides have been shown to reduce angiogenesis induced by cytokines and to mediate apoptosis in endothelial cells.3 It appears that RGD peptides that are constrained in a cyclic conformation, show an increased affinity for binding to integrins. 4 One example is the cyclic RGD-4C peptide, a potent binder of a 5 b 1 , a V b 3 and a V b 5 used to selectively deliver doxorubicin to tumor blood vessels 5 and to internalize the amphipatic peptide (KLAKLAK) 2 in endothelial cells resulting in cellular apoptosis.

Dengue viruses belong to the Flavivirus family and are responsible for hemorrhagic fever in Human. Dengue virus infection triggers apoptosis especially through the expression of the small membrane (M) protein. Using isolated mitochondria, we found that synthetic peptides containing the C-terminus part of the M ectodomain caused apoptosis-related mitochondrial membrane permeabilization (MMP) events. These events include matrix swelling and the dissipation of the mitochondrial transmembrane potential (DeltaPsi(m)). Protein M Flavivirus sequence alignments and helical wheel projections reveal a conserved distribution of charged residues. Moreover, when combined to the cell penetrating HIV-1 Tat peptide transduction domain (Tat-PTD), this sequence triggers a caspase-dependent cell death associated with DeltaPsi(m) loss and cytochrome c release. Mutational approaches coupled to functional screening on isolated mitochondria resulted in the selection of a protein M derived sequence containing nine residues with potent MMP-inducing properties on isolated mitochondria. A chimeric peptide composed of a Tat-PTD linked to the 9-mer entity triggers MMP and cell death. Finally, local administration of this chimeric peptide induces growth inhibition of xenograft prostate PC3 tumors in immuno-compromised mice, and significantly enhances animal survival. Together, these findings support the notion of using viral genomes as valuable sources to discover mitochondria-targeted sequences that may lead to the development of new anticancer compounds.

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