Mononuclear nonheme iron(III)-peroxo complexes bearing N-tetramethylated cyclam (n-TMC) ligands, [FeIII(O2)(n-TMC)]+ (n = 12, 13, and 14), Show more
Mononuclear nonheme iron(III)-peroxo complexes bearing N-tetramethylated cyclam (n-TMC) ligands, [FeIII(O2)(n-TMC)]+ (n = 12, 13, and 14), have recently shown highly intriguing reactivities in various oxidation reactions, such as the cis-dihydroxylation and C-H functionalization reactions, which were previously associated only with high-valent iron-oxo intermediates in heme and nonheme iron enzymes. Herein, we extend our study to report [FeIII(O2)(n-TMC)]+ mediated N-demethylation of N,N-dimethylanilines (DMAs), another reaction that was previously associated only with high-valent iron-oxo cores. Most importantly, we provide definitive evidence of the occurrence of electron transfer from DMAs to [FeIII(O2)(n-TMC)]+, thereby establishing an electron-transfer (ET) pathway for the N-demethylation reaction. Investigation of the ET reactivity of [FeIII(O2)(n-TMC)]+ in light of the Marcus theory of ET, and a comparison of the N-demethylation and the ET rate constants corroborate a mechanism, whereby N-demethylation of DMAs by [FeIII(O2)(n-TMC)]+ proceeds via the peroxide O-O bond cleavage of [FeIII(O2)(n-TMC)]+ to form a transient [FeIV(O2-)(O• -)(n-TMC)]+ species, which undergoes a proton-coupled electron-transfer (PCET) or an uncoupled electron transfer-proton transfer (ET/PT) in the presence of DMAs. Saturation kinetics support the rate-determining formation of [FeIV(O2-)(O• -)(n-TMC)]+ in a pre-equilibrium step with the same values of the O-O bond cleavage rate constants irrespective of the substrates, such as DMAs and one-electron oxidants. The present study corroborates that mononuclear nonheme iron(III)-peroxo cores are not mere pass-through points en route to high-valent metal-oxo intermediates, but they can play an important role in the diverse oxidation reactions of Rieske oxygenases, such as in the N-demethylation reaction. Show less
Mitochondria are central actors in diverse physiological phenomena ranging from energy metabolism to stress signaling and immune modulation. Accumulating scientific evidence points to the critical inv Show more
Mitochondria are central actors in diverse physiological phenomena ranging from energy metabolism to stress signaling and immune modulation. Accumulating scientific evidence points to the critical involvement of specific mitochondrial-associated events, including mitochondrial quality control, intercellular mitochondrial transfer, and mitochondrial genetics, in potentiating the metastatic cascade of neoplastic cells. Furthermore, numerous recent studies have consistently emphasized the highly significant role mitochondria play in coordinating the regulation of tumor-infiltrating immune cells and immunotherapeutic interventions. This review provides a comprehensive and rigorous scholarly investigation of this subject matter, exploring the intricate mechanisms by which mitochondria contribute to tumor metastasis and examining the progress of mitochondria-targeted cancer therapies. Show less
Developing novel therapeutics often follows three steps: target identification, design of strategies to suppress target activity and drug development to implement the strategies. In this review, we re Show more
Developing novel therapeutics often follows three steps: target identification, design of strategies to suppress target activity and drug development to implement the strategies. In this review, we recount the evidence identifying the basic leucine zipper transcription factors ATF5, CEBPB, and CEBPD as targets for brain and other malignancies. We describe strategies that exploit the structures of the three factors to create inhibitory dominant-negative (DN) mutant forms that selectively suppress growth and survival of cancer cells. We then discuss and compare four peptides (CP-DN-ATF5, Dpep, Bpep and ST101) in which DN sequences are joined with cell-penetrating domains to create drugs that pass through tissue barriers and into cells. The peptide drugs show both efficacy and safety in suppressing growth and in the survival of brain and other cancers in vivo, and ST101 is currently in clinical trials for solid tumors, including GBM. We further consider known mechanisms by which the peptides act and how these have been exploited in rationally designed combination therapies. We additionally discuss lacunae in our knowledge about the peptides that merit further research. Finally, we suggest both short- and long-term directions for creating new generations of drugs targeting ATF5, CEBPB, CEBPD, and other transcription factors for treating brain and other malignancies. Show less
Simple Summary The gene-regulatory factors ATF5, CEBPB and CEBPD promote survival, growth, metastasis and treatment resistance of a range of cancer cell types. Presently, no drugs target all three at Show more
Simple Summary The gene-regulatory factors ATF5, CEBPB and CEBPD promote survival, growth, metastasis and treatment resistance of a range of cancer cell types. Presently, no drugs target all three at once. Here, with the aim of treating cancers, we designed novel cell-penetrating peptides that interact with and inactivate all three. The peptides Bpep and Dpep kill a range of cancer cell types in culture and in animals. In animals with tumors, they also significantly increase survival time. In contrast, they do not affect survival of non-cancer cells and have no apparent side effects in animals. The peptides work in combination with other anti-cancer treatments. Mechanism studies of how the peptides kill cancer cells indicate a decrease in survival proteins and increase in death proteins. These studies support the potential of Bpep and Dpep as novel, safe agents for the treatment of a variety of cancer types, both as mono- and combination therapies. Abstract Transcription factors are key players underlying cancer formation, growth, survival, metastasis and treatment resistance, yet few drugs exist to directly target them. Here, we characterized the in vitro and in vivo anti-cancer efficacy of novel synthetic cell-penetrating peptides (Bpep and Dpep) designed to interfere with the formation of active leucine-zipper-based dimers by CEBPB and CEBPD, transcription factors implicated in multiple malignancies. Both peptides similarly promoted apoptosis of multiple tumor lines of varying origins, without such effects on non-transformed cells. Combined with other treatments (radiation, Taxol, chloroquine, doxorubicin), the peptides acted additively to synergistically and were fully active on Taxol-resistant cells. The peptides suppressed expression of known direct CEBPB/CEBPD targets IL6 , IL8 and asparagine synthetase ( ASNS ), supporting their inhibition of transcriptional activation. Mechanisms by which the peptides trigger apoptosis included depletion of pro-survival survivin and a required elevation of pro-apoptotic BMF. Bpep and Dpep significantly slowed tumor growth in mouse models without evident side effects. Dpep significantly prolonged survival in xenograft models. These findings indicate the efficacy and potential of Bpep and Dpep as novel agents to treat a variety of cancers as mono- or combination therapies. Show less