Editorial [Hot Topic:Anti-Cancer-Drugs (Executive Editor: E. Bergmann-Leitner)]

The development of cancer therapies has diversified tremendously in the last decade and this development is in part due to our significantly improved understanding of the biological processes leading to tumor progression and metastasis. Despite this encouraging development, the success rate of cancer therapies is still disappointingly low. Investigating such treatment failures and shortcomings can greatly advance our understanding of tumor biology. For example, the study of drug resistant phenotypes in tumors has led to either the discovery of genes responsible for the phenotype and/or the identification of pathways that substitute or bypass those pathways targeted by the drugs. Such crucial findings guide researchers in the development of analogues of conventional drugs or result in the discovery of new anti-cancer reagents many of which are either contained within natural foods or are novel compounds isolated from plants or marine life. The current issue of Current Pharmaceutical Design reflects some of those most recent approaches in the development of anti-cancer drugs, that is the attempt to either identify and target specific signaling pathways used by tumor cells or to characterize novel anti-cancer agents. To reflecting these recent research efforts, this issue of “Anti-Cancer-Drugs” consists two parts: the first part contains two reports on novel approaches and novel molecular targets to either inhibit undesirable or to reconstitute proper signaling in cancer cells and thus an effort to revert cancer cells into a mortal somatic cell. To this end, Bianco et al. [1] describe efforts of combination therapies that bypass mechanisms, which render tumor cells resistant to blockers of epidermal growth factor (EGF)-receptor mediated signaling. Pennington et al. [2] outline strategies that target redox-sensitive signaling factors such as thioredoxin and thioredoxin reductase for cancer therapy. The idea here is to revert the pro-survival signals that tumor cells receive and thus promote the apoptosis induced by oxidative stress. This represents an attractive approach to render tumor cells susceptible to various otherwise only moderately effective treatments and drugs. The second part of this issue contains several reports on the discovery of novel anti-cancer agents that had originally been used for therapy of other diseases and disorders. Michaelis et al. [3] report on the efficacy of Valproic acid (VP) for treatment of various leukemias and solid tumors. Moreover, the authors review recent developments in the research surrounding VP and its anti-neoplastic activities. Nishino et al. [4] assess the effects of various phytochemicals on cancer growth as well as the potential molecular targets of such agents. Ichikawa et al. [5] review the re-discovery of ancient drugs as well as substances from fruits and plants, which had been used in ancient medicines. Their review focuses on the effect of such substances on targeting the NF-κB pathway and other signaling pathways known to be involved in tumorigenesis. Thomas Adrian [6] provides a comprehensive overview of novel marine-derived anti-cancer drugs, their origins as well as their efficacy in the treatment of various malignancies and - where known - their mode of action and molecular targets. Finally, Le Tourneau et al. [7] outline the difficulties and challenges involved in tumor therapy with one of those marine-derived anti-cancer agents, specifically Aplidine. I would like to thank all the authors for their efforts in reviewing their own research data and the encompassing body of literature in order to make this issue a comprehensive overview of current efforts to identify and target molecular pathways as well as to discover efficacious novel anti-cancer drugs.