In vivo and in vitro distribution of type 5 and fiber-modified oncolytic adenoviruses in human blood compartments.

Background: Successful tumor targeting of systemically administered oncolytic adenoviruses may be hindered by interactions with blood components.

Materials And Methods: Blood distribution of oncolytic adenoviruses featuring type 5 adenovirus fiber, 5/3 capsid chimerism, or RGD-4C in the fiber knob was investigated in vitro and in patients with refractory solid tumors.

Results: Virus titers and prevalence in serum of patients increased over the first post-treatment week, suggesting replication.

Tissue-specific promoters active in CD44+CD24-/low breast cancer cells.

It has been proposed that human tumors contain stem cells that have a central role in tumor initiation and posttreatment relapse. Putative breast cancer stem cells may reside in the CD44(+)CD24(-/low) population. Oncolytic adenoviruses are attractive for killing of these cells because they enter through infection and are therefore not susceptible to active and passive mechanisms that render stem cells resistant to many drugs.

Cancer, stem cells, and oncolytic viruses.

Cells with stem cell-like attributes, such as self-renewal and pluripotency, have been isolated from hematological malignancies and from several solid tumor types. Tumor-initiating cells, also referred to as cancer stem cells, are thought to be responsible for the initiation and growth of tumors. Like their normal counterparts, putative cancer stem cells show remarkable resistance to radiation and chemotherapy.

Virotherapy as an approach against cancer stem cells.

It has been hypothesized that cancers originate from a small population of cells with stem cell-like characteristics, including self-renewal and pluripotency. Such tumor-initiating cells, also referred to as cancer stem cells, are thought to account for relapses following seemingly successful treatments, because their slow turnover and capacity for expelling anti-tumor drugs leaves them untouched by conventional treatment regimens. Targeting of cancer stem cells might be key for improving survival and producing cures in patients with metastatic tumors.

An elementary reaction step of the proton pump is revealed by mutation of tryptophan-164 to phenylalanine in cytochrome c oxidase from Paracoccus denitrificans.

Cytochrome c oxidase couples reduction of dioxygen to water to translocation of protons over the inner mitochondrial or bacterial membrane. A likely proton acceptor for pumped protons is the Delta-propionate of heme a(3), which may receive the proton via water molecules from a conserved glutamic acid (E278 in subunit I of the Paracoccus denitrificans enzyme) and which receives a hydrogen bond from a conserved tryptophan, W164. Here, W164 was mutated to phenylalanine (W164F) to further explore the role of the heme a(3) Delta-propionate in proton translocation.

Gating of proton and water transfer in the respiratory enzyme cytochrome c oxidase.

The membrane-bound enzyme cytochrome c oxidase is responsible for cell respiration in aerobic organisms and conserves free energy from O2 reduction into an electrochemical proton gradient by coupling the redox reaction to proton-pumping across the membrane. O2 reduction produces water at the bimetallic heme a3/CuB active site next to a hydrophobic cavity deep within the membrane. Water molecules in this cavity have been suggested to play an important role in the proton-pumping mechanism.

The catalytic cycle of cytochrome c oxidase is not the sum of its two halves.

Membrane-bound cytochrome c oxidase catalyzes cell respiration in aerobic organisms and is a primary energy transducer in biology. The two halves of the catalytic cycle may be studied separately: in an oxidative phase, the enzyme is oxidized by O(2), and in a reductive phase, the oxidized enzyme is reduced before binding the next O(2) molecule. Here we show by time-resolved membrane potential and pH measurements with cytochrome oxidase liposomes that, with both phases in succession, two protons are translocated during each phase, one during each individual electron transfer step.