Pro-apoptotic Activity of BH3-only Proteins and BH3 Mimetics: from Theory to Potential Cancer Therapy.
ABSTRACT The evasion of cancer cells from the induction of cell death pathways results in the resistance of tumor to current treatment modalities. Therefore, the resistance to cell death, one of the hallmarks of cancer, is a major target in the development of new approaches to selectively affect cancer cells. The complex interplay between individual members of Bcl-2 family regulates both cell survival and the mitochondrial pathway of apoptosis by maintaining mitochondrial membrane integrity (anti-apoptotic Bcl-2 subfamily) and by triggering its disruption in response to stress stimuli (Bax-like subfamily). BH3-only proteins, another Bcl-2 subfamily, act either by direct stimulation of pro-apoptotic proteins of the Bax subfamily or by interfering with anti-apoptotic proteins of the Bcl-2 subfamily. Thus, pro-apoptotic BH3 mimetics, thought to function as BH3-only proteins, are expected to improve the effectiveness of cancer treatment. BH3 mimetics could be either natural or synthetic, peptidic or only based on a helical peptide-like scaffold. Experimental and clinical evidence indicates that BH3 mimetics may not be sufficient to cure cancer patients when used as a single agent. BH3 profiling of cancer cells was introduced to better predict the in vivo responsiveness of tumor to BH3 mimetics combined with conventional therapies. In summary, targeting the Bcl-2 proteins is a promising tool with potential to generate new treatment modalities and to complement existing anti-cancer therapies. This review presents the current knowledge on BH3-only proteins and the spectrum of strategies employing BH3 mimetics in preclinical and clinical studies that aim at tumor targeting.
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ABSTRACT: Despite recent developments for new targeted therapies in melanoma, as BRAF inhibitors and immune-stimulating antibodies, tumor relapse frequently follows with less than a year. Therapy resistance should be explained by defects in proapoptotic signaling. Thus, efficient induction of apoptosis in tumor cells appears as predominant therapeutic goal. In apoptosis control of melanoma, the balance between pro- and antiapoptotic Bcl-2 proteins plays a decisive role. In particular, members of the subfamily of BH3-only proteins function as proapoptotic triggers, and mimetics of these proteins are already in clinical trials in other cancers. Recent experimental work has revealed that the effects of different treatments in melanoma are related to the activation of BH3-only proteins, and also the proapoptotic effects of BRAF inhibitors are prevented by knockdown of the BH3-only protein Bim. Thus, melanoma therapy might be critically improved by the combination of survival pathway antagonists as BRAF inhibitors with BH3 mimetics. This article is protected by copyright. All rights reserved.Experimental Dermatology 03/2014; · 3.58 Impact Factor
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ABSTRACT: Intracellular eukaryotic parasites and their host cells constitute complex, coevolved cellular interaction systems that frequently cause disease. Among them, Plasmodium parasites cause a significant health burden in humans, killing up to one million people annually. To succeed in the mammalian host after transmission by mosquitoes, Plasmodium parasites must complete intracellular replication within hepatocytes and then release new infectious forms into the blood. Using Plasmodium yoelii rodent malaria parasites, we show that some liver stage (LS)-infected hepatocytes undergo apoptosis without external triggers, but the majority of infected cells do not, and can also resist Fas-mediated apoptosis. In contrast, apoptosis is dramatically increased in hepatocytes infected with attenuated parasites. Furthermore, we find that blocking total or mitochondria-initiated host cell apoptosis increases LS parasite burden in mice, suggesting that an anti-apoptotic host environment fosters parasite survival. Strikingly, although LS infection confers strong resistance to extrinsic host hepatocyte apoptosis, infected hepatocytes lose their ability to resist apoptosis when anti-apoptotic mitochondrial proteins are inhibited. This is demonstrated by our finding that B-cell lymphoma 2 family inhibitors preferentially induce apoptosis in LS-infected hepatocytes and significantly reduce LS parasite burden in mice. Thus, targeting critical points of susceptibility in the LS-infected host cell might provide new avenues for malaria prophylaxis.Cell Death & Disease 01/2013; 4:e762. · 6.04 Impact Factor
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ABSTRACT: Melanoma is a therapy-resistant skin cancer due to numerous mechanisms supporting cell survival. Although components of melanoma cytoprotective mechanisms are overexpressed in many types of tumors, some of their regulators are characteristic for melanoma. Several genes mediating pro-survival functions have been identified as direct targets of microphthalmia-associated transcription factor (MITF), a melanocyte-specific modulator also recognized as a lineage addiction oncogene in melanoma. BRAF(V600E) and other proteins deregulated in melanoma influence MITF expression and activity, or they are the partners of MITF in melanoma response to radiotherapy and chemotherapeutics. In this review, the pro-survival activity of MITF is discussed.Journal of Investigative Dermatology advance online publication, 21 August 2014; doi:10.1038/jid.2014.319.The Journal of investigative dermatology. 08/2014;