Current Drug Targets (v.17, #10)

Meet Our Editorial Board Member by Manuel S. Yepes (1101-1101).

Cancer: A Problem of Developmental Biology; Scientific Evidence for Reprogramming and Differentiation Therapy by Stewart Sell, Andrea Nicolini, Paola Ferrari, Pier M. Biava (1103-1110).
Current medical literature acknowledges that embryonic micro-environment is able to suppress tumor development. Administering carcinogenic substances during organogenesis in fact leads to embryonic malformations, but not to offspring tumor growth. Once organogenesis has ended, administration of carcinogenic substances causes a rise in offspring tumor development. These data indicate that cancer can be considered a deviation in normal development, which can be regulated by factors of the embryonic microenvironment. Furthermore, it has been demonstrated that teratoma differentiates into normal tissues once it is implanted in the embryo. Recently, it has been shown that implanting a melanoma in Zebrafish embryo did not result in a tumor development; however, it did in the adult specimen. This demonstrates that cancer cells can differentiate into normal tissues when implanted in the embryo. In addition, it was demonstrated that other tumors can revert into a normal phenotype and/or differentiate into normal tissue when implanted in the embryo. These studies led some authors to define cancer as a problem of developmental biology and to predict the present concept of "cancer stem cells theory". In this review, we record the most important researches about the reprogramming and differentiation treatments of cancer cells to better clarify how the substances taken from developing embryo or other biological substances can induce differentiation of malignant cells. Lastly, a model of cancer has been proposed here, conceived by one of us, which is consistent with the reality, as demonstrated by a great number of researches. This model integrates the theory of the "maturation arrest" of cancer cells as conceived by B. Pierce with the theory which describes cancer as a process of deterministic chaos determined by genetic and/or epigenetic alterations in differentiated cells, which leads a normal cell to become cancerous. All the researches here described demonstrated that cancer can be considered a problem of developmental biology and that one of the most important hallmarks of cancer is the loss of differentiation as already described by us in other articles.

Tumor Stroma Manipulation By MSC by Giulia Grisendi, Carlotta Spano, Filippo Rossignoli, Naomi D';souza, Giulia Golinelli, Agnese Fiori, Edwin M Horwitz, Valentina Guarneri, Federico Piacentini, Paolo Paolucci, Massimo Dominici (1111-1126).
Tumor stroma (TS) plays relevant roles in all steps of cancer development. We here address several fundamental aspects related with the interaction between cancer cells and their stromal counterparts. Dissecting these players is of pivotal importance to understand oncogenesis, immunoescape and drug resistance. In addition, this better comprehension will allow the introduction of novel and more effective therapeutic approaches where manipulated stromal elements may become detrimental for tumor growth. Our group and others rely on the use of multipotent mesenchymal stromal/stem cells (MSC) as anti-cancer tools, since these putative TS cell precursors can deliver potent apoptosis-inducing agents. Multimodal-armed MSC can target a variety of cancers in vitro and, when injected in vivo, they localize into tumors mediating cell death without evident toxicities to normal tissues. While several aspects of these strategies shall require further investigations, these approaches collectively indicate how TS manipulation by MSC represents a tool to influence the fate of cancer cells, creating a new generation of anti-cancer strategies.

Immunotherapy and Hormone-therapy in Metastatic Breast Cancer: A Review and an Update by Andrea Nicolini, Angelo Carpi, Paola Ferrari, Pier Mario Biava, Giuseppe Rossi (1127-1139).
Historically, antiestrogen is the first targeted therapy used in breast cancer treatment. In fact, its rationale lies in the molecular pathways elucidated by basic research. In estrogen receptor (ER)-alpha positive metastatic breast cancer patients, hormone-therapy remains the first option of treatment. While tamoxifen concomitant with suppression of ovarian function with luteinizing hormone releasing hormone (LHRH) agonists is the standard first line treatment in premenopausal, third generation aromatase inhibitors (AIs) are the first line standard hormone therapy in postmenopausal. However, the development of acquired resistance during antiestrogen therapy continues to be a central clinical problem. This review provides an update on the antiestrogen action and report on immunological treatment of the advanced disease by some cytokines. Interleukin-2, interleukin-12 and interferons used alone or in combination demonstrated an anti-tumor action directly and/or through synergism with antiestrogens. A rationale for the addition of interferon-beta and interleukin-2 to antiestrogens is described. Furthermore, we summarize and interpret the clinical and laboratory data of a recent long-term hormone- immunotherapy study in metastatic endocrine dependent breast cancer patients. Prospective randomized trials are necessary to confirm some recent promising results based on an immunological approach in addition to antiestrogens to overcome or delay acquired hormone resistance.

Cancer cachexia is a debilitating paraneoplastic wasting syndrome characterized by skeletal muscle depletion and unintentional weight loss. It affects up to 50-80% of patients with cancer and directly accounts for one-quarter of cancer-related deaths due to cardio-respiratory failure. Muscle weakness, one of the hallmarks of this syndrome, has been postulated to be due to a combination of muscle breakdown, dysfunction and decrease in the ability to repair, with effective treatment strategies presently limited. Excessive inflammatory cytokine levels due to the host-tumor interaction, such as Interleukin (IL)-6 and Tumor Necrosis Factor (TNF)-α, are hypothesised to drive this pathological process but the specific mechanisms by which these cytokines produce skeletal muscle dysfunction in cancer cachexia remain undefined. Endoplasmic Reticulum (ER) stress and the associated disruptions in calcium signaling have been implicated in cytokine-mediated disruptions in skeletal muscle and function. Disrupted ER stress-related processes such as the Unfolded Protein Response (UPR), calcium homeostasis and altered muscle protein synthesis have been reported in clinical and experimental cachexia and other inflammation-driven muscle diseases such as myositis, potentially suggesting a link between increased IL-6 and TNF-α and ER stress in skeletal muscle cells. As the concept of upregulated ER stress in skeletal muscle cells due to elevated cytokines is novel and potentially very relevant to our understanding of cancer cachexia, this review aims to examine the potential relationship between inflammatory cytokine mediated muscle breakdown and ER stress, in the context of cancer cachexia, and to discuss the molecular signaling pathways underpinning this pathology.

A-kinase anchoring proteins (AKAPs) control the localization of cAMP-dependent protein kinase A (PKA) by tethering PKA to distinct cellular compartments. Through additional direct proteinprotein interactions with PKA substrates and other signaling molecules they form multi-protein complexes. Thereby, AKAPs regulate the access of PKA to its substrates in a temporal and spatial manner as well as the local crosstalk of cAMP/PKA with other signaling pathways. Due to the increasing information on their molecular functioning and three-dimensional structures, and their emerging roles in the development of diseases, AKAPs move into the focus as potential drug targets. Targeting AKAP dependent protein-protein interactions for interference with local signal processing inside cells potentially allows for the development of therapeutics with high selectivity and fewer side effects.

Delivery of Therapeutic Proteins: Challenges and Strategies by Kanwal Rehman, Muhammad Sajid Hamid Akash, Bushra Akhtar, Muhammad Tariq, Abid Mahmood, Muhammad Ibrahim (1172-1188).
Recent advances in genetic engineering and pharmaceutical biotechnology have made possible to combat life-threatening diseases with efficient delivery of therapeutic proteins. These advancements have increased the significance of therapeutic proteins in pharmaceutical market, but their therapeutic delivery to the targeted site is still a major obstacle to achieve desired therapeutic outcomes. In most cases, majority of the therapeutic proteins are usually administered via oral routes which encounter many problems notably enzymatic degradation, poor solubility and nonlinear pharmacokinetics. Besides this route, many other routes like mucosal, intra-nasal, intra-vaginal, pulmonary and transdermal have also been used for the delivery of therapeutic proteins. In order to keep these therapeutic proteins safe from enzymatic degradation and improve their therapeutic efficacy, several strategies have been designed and investigated various therapeutic delivery routes for efficient delivery of therapeutic proteins to the targeted site with minimal side effects. In this article, we have comprehensively summarized the recent advances and developments that have been adopted for delivery systems of these therapeutic proteins via invasive and/or non-invasive routes.

Perspectives On Membrane-associated Progesterone Receptors As Prospective Therapeutic Targets by Sae Hasegawa, Mayu Kasubuchi, Kazuya Terasawa, Ikuo Kimura (1189-1197).
Progesterone receptor membrane components 1 and 2, neudesin, and neuferricin belong to the membraneassociated progesterone receptor (MAPR) family. Recently, sex steroid membrane receptors have gained attention because of their potential involvement in sex hormone-mediated rapid non-genomic effects, which cannot currently be explained by the genomic action of nuclear receptors. Progesterone may increase cell proliferation and survival via nongenomic effects including the activation of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3- kinase (PI3K) pathways through MAPRs. Moreover, the unique expression of MAPRs suggests that they could be used as biomarkers and drug targets for sex steroid-related cancers and other diseases. In this review, we summarize the physiological roles of the MAPRs, provide a comprehensive overview of their progesterone-mediated non-genomic actions, and discuss new insights into their potential as therapeutic targets.

Untapped Potential of Disordered Proteins in Current Druggable Human Proteome by Gang Hu, Zhonghua Wu, Kui Wang, Vladimir N. Uversky, Lukasz Kurgan (1198-1205).
Current efforts in design and characterization of drugs often rely on the structure of their protein targets. However, a large fraction of proteins lack unique 3-D structures and exist as highly dynamic structural ensembles. These intrinsically disordered proteins are involved in pathogenesis of various human diseases and are highly abundant in eukaryotes. Based on a comprehensive analysis of the current druggable human proteome covering 12 drug classes and 18 major classes of drug targets we show a significant bias toward high structural coverage and low abundance of intrinsic disorder. We review reasons for this bias including widespread use of the structural information in various stages of drug development and characterization process and difficulty with attaining structures for the intrinsically disordered proteins. We also discuss future of intrinsically disordered proteins as drug targets. Given the overall high disorder content of the human proteome and current bias of the druggable human proteome toward structural proteins, it is inevitable that disordered proteins will have to raise up on the list of prospective drug targets. The protein disorder-assisted drug design can draw from current rational drug design techniques and would also need novel approaches that no longer rely on a unique protein structure.

Resolving Inflammation in Heart Failure: Novel Protective Lipid Mediators by Marta Reina-Couto, Luís Vale, Jorge Carvalho, Paulo Bettencourt, António Albino-Teixeira, Teresa Sousa (1206-1223).
Inflammation is an important pathogenic mechanism in chronic heart failure (HF). The perpetuation of the inflammatory response in this syndrome may result either from excessive activation of proinflammatory cascades or disturbances in the resolution of inflammation. However, although cardiovascular research has extensively investigated the proinflammatory processes involved in chronic HF pathophysiology, the mechanisms responsible for inflammation resolution in this disease remain largely disregarded. The resolving response is currently considered an active process involving specific effectors that limit the progression of inflammation and promote tissue regeneration. This article aims at reviewing the major classes of lipid mediators of inflammation resolution, their cardiovascular, metabolic and renal protective effects that might putatively delay the onset and progression of chronic HF, and their therapeutic modulation. Furthermore, it also aims to emphasize the importance of adopting therapeutic strategies that stimulate the resolution of inflammation in chronic HF.

ERRATUM (1224-1224).