Anti-Cancer Agents in Medicinal Chemistry (v.14, #10)

Differential Effects of Antofine N-Oxide on Solid Tumor and Leukemia Cells by Tania Bour, Xianwen Yang, Weihong Li, Francois Bernardin, Tony Kaoma, Arnaud Muller, Laurent Vallar, Andre Steinmetz (1315-1323).
We have studied the anti-cancer activities of antofine N-oxide isolated and purified from the medicinal plant Cynanchumvincetoxicum. Antofine N-oxide displayed a strong inhibitory effect on several solid tumor cell lines (glioblastoma, breast carcinoma andlung carcinoma) and on a T-cell leukemia cell line. Remarkably, its cytotoxic effect was considerably weaker in non-cancer cells.Antofine N-oxide was found to inhibit proliferation of the solid tumor cells whereas it caused apoptotic cell death in the leukemia cells. Amicroarray analysis after a short treatment revealed that the number of differentially expressed genes was considerably higher in solidtumor than in leukemia cells. Up-regulated genes in the three solid tumor cell lines include genes related to TNFα signaling, of whichTNFα was among the most significantly induced. A functional analysis revealed that TNFR1 signaling was most likely activated in thesolid tumor cells. The increased mRNA levels of several genes of this pathway (namely TNFα, TNFAIP3 and BIRC3) were confirmed byreal-time quantitative PCR after different treatment durations. Finally a slight inhibition of NF?B-mediated transcription was observed in thesame cells. Together our results suggest that inhibition of cell proliferation in solid tumor cells essentially occurs through TNFα signalingwhereas this pathway is not activated in leukemia cells. Apoptotic cell death in the latter is induced by a distinct yet unknown pathway.

White Poplar (Populus alba L.) Suspension Cultures as a Model System to Study Apoptosis Induced by Alfalfa Saponins by Alma Balestrazzi, Daniela Carbonera, Pinarosa Avato, Aldo Tava (1324-1331).
In animal cells, the anticancer function played by plant saponins involves a complex network of molecular processes that stilldeserves investigation and apoptosis seems to be the outstanding pathway. An intriguing aspect of the biological activity of saponins isrelated to their effects on genome integrity. As demonstrated by the studies carried out in white poplar (Populus alba L., cv Villafranca)cell suspension cultures, plant cells can as well be used as a model system to unravel the molecular mechanisms activated by plantsaponins. These recent studies have evidenced that animal and plant cells share common features in their response to saponins, paving theway for novel opportunities for both basic and applied research. Indeed, there is a certain interest in replacing the animal models forpharmacological research, at least when preliminary large-scale cytotoxicity tests are performed on wide collections of natural extractsand/or purified compounds. The review provides an up-date of the molecular pathways (signal transduction, antioxidant response, DNArepair) associated with plant saponin bioactivity, with an emphasis on apoptosis induced by alfalfa (Medicago sativa L.) saponins. Thecomparison between animal and plant cells as tools for the study of saponin bioactivity is also discussed in view of the most recentliterature and innovative future applications.

Improving the Efficacy of Plant Polyphenols by Lucia Biasutto, Andrea Mattarei, Nicola Sassi, Michele Azzolini, Matteo Romio, Cristina Paradisi, Mario Zoratti (1332-1342).
Plant polyphenols exhibit potentially useful effects in a wide variety of pathophysiological settings. They interact with proteinssuch as signalling kinases, transcription factors and ion channels, and modulate redox processes, such as those taking place inmitochondria. Biomedical applications of these natural compounds are however severely hindered by their low bioavailability, rapidmetabolism, and often by unfavourable physico-chemical properties, e.g. a generally low water solubility. Derivatives are underdevelopment with the aim of improving their bioavailability and/or bioefficacy. Various strategies can be adopted. An increase incirculating blood levels of non-metabolized natural compound may be attainable through prodrugs. In the ideal prodrug, phenolichydroxyls are protected by capping groups which a) help or at least do not hinder permeation of epithelia; b) prevent conjugativemodifications during absorption and first-pass through the liver; c) are eliminated with opportune kinetics to regenerate the parentcompound. Moreover, prodrugs may be designed with the goals of modulating physical properties of the parent compound, and/orchanging its distribution in the body. A more specific action may be achieved by concentrating the compounds at specific sites of action.An example of the second approach is represented by mitochondria-targeted redox-active polyphenol derivatives, designed to interveneon radical processes in these organelles and as a tool either to protect cells from oxidative insults or to precipitate their death.Mitochondrial targeting can be achieved through conjugation with a triphenylphosphonium lipophilic cation. Quercetin and resveratrolwere chosen as model polyphenols for these proof-of-concept studies. Data available at the moment show that both quercetin andresveratrol mitochondria-targeted derivatives are pro-oxidant and cytotoxic in vitro, selectively killing fast-growing and tumoural cellswhen supplied in the low ?M range; the mechanism of ROS generation appears to differ between the two classes of compounds.;These approaches are emerging as promising strategies to obtain new efficient chemopreventive and/or chemotherapeutic drugs based onpolyphenols derivatives.

Tea catechins exhibit a broad range of pharmacological activities that impart beneficial effects on human health.Epigallocatechin-3-gallate (EGCG), one of the major tea catechins, has been widely associated with cancer prevention and treatment. Inaddition, tea catechins in combination with anticancer drugs are being evaluated as a new cancer treatment strategy. However, theinteractions of anticancer drugs with tea catechins are largely unknown. Accumulated data indicate significant interactions betweenanticancer drugs and tea catechins, such as synergistic tumor inhibition or antagonist activity. Therefore, it is critical to understandcomprehensively the effects of tea catechins on anticancer drugs. Focusing on evidence from preclinical studies, this paper will reviewthe interactions between anticancer drugs and tea catechins, including pharmacodynamics and pharmacokinetics effects. We hope that bydetailing the interactions between anticancer drugs and tea catechins, more attention will be directed to this important therapeuticcombination in the future.

Plant Coumestans: Recent Advances and Future Perspectives in Cancer Therapy by Tereza Nehybova, Jan Smarda, Petr Benes (1351-1362).
Natural products are often used in drug development due to their ability to form unique and diverse chemical structures.Coumestans are polycyclic aromatic plant secondary metabolites containing a coumestan moiety, which consists of a benzoxole fused toa chromen-2-one to form 1-Benzoxolo[3,2-c]chromen-6-one. These natural compounds are known for large number of biologicalactivities. Many of their biological effects can be attributed to their action as phytoestrogens and polyphenols. In the last decade,anticancer effects of these compounds have been described in vitro but there is only limited number of studies based on models in vivo.More information concerning their in vivo bioavailability, stability, metabolism, toxicity, estrogenicity, cellular targets and druginteractions is therefore needed to proceed further to clinical studies. This review focuses on coumestans exhibiting anticancer propertiesand summarizes mechanisms of their toxicity to cancer cells. Moreover, the possible role of coumestans in cancer prevention isdiscussed.

Pro-Oxidative Action of Polyphenols as Action Mechanism for their Pro-Apoptotic Activity by Raffaella Marina Lecci, Antonio Logrieco, Antonella Leone (1363-1375).
Polyphenols, secondary metabolites widely present in plant kingdom, are known for their positive effects on human health,such as treatments of degenerative disease and cancer. Many dietary polyphenols show anti-inflammatory, immunomodulatory and antioxidantproperties and they are proposed as chemopreventive agents for many skin disorders and cancer. Exposure to solar UV radiationis widely considered to cause skin cancer and a consistent carcinogenic dose derived from UVA causes several skin disorders as aconsequence of free radicals generation and DNA damages.;In this study, verbascoside, isoverbascoside and tyrosol were investigated for their effects on HEKa (Human Epidermal Keratinocytesadult) cell cultures challenged from UVA-rays. Non-toxic doses of each polyphenol were assayed on HEKa before, during and after theexposure to a damaging dose of UVA. Treatment with polyphenols before and after the UVA-irradiation exerted a pro-oxidant effect,while the simultaneous treatment caused a weak decrease of ROS production. The increasing of ROS levels was associated with a proapoptoticeffect on HEKa, detected by AnnexinV/Propidiun Iodide, mainly evident in surviving cells treated with the polyphenols afterthe UVA-irradiation. The pro-apoptotic effect was confirmed by the immunodetection of significant changes in the Bax and Bcl-xLprotein levels, leading to apoptotic events.;The hypothesis that these polyphenols could trigger the apoptosis pathway mainly in UVA-damaged cells, via ROS increase, is hereproposed as action mechanism behind their protective effect.

Antioxidant Activity and Chemical Components as Potential Anticancer Agents in the Olive Leaf (Olea europaea L. cv Leccino.) Decoction by Simona De Marino, Carmen Festa, Franco Zollo, Antonella Nini, Lina Antenucci, Gennaro Raimo, Maria Iorizzi (1376-1385).
Epidemiological studies have shown that a reduced risk of chronic diseases such as cancer and cardiovascular diseases iscorrelated with a regular consumption of fruits and vegetable, many of which are rich in polyphenols. The additive and synergistic effectof phytochemicals in fruits and vegetables may reduce chronic diseases related to oxidative stress in human body. Olea europaea L. leafare rich in phenolic components, which have been proposed to play a role in cancer prevention. The purpose of this study was to identifythe main components in the Olea europaea L. leaf (cv. Leccino) preserved during the decoction preparation, in order to delineate theantioxidant activities of the crude extracts and its isolated compounds by using different in vitro assays including DPPH radicalscavengingcapacity, total antioxidant capacity (TAC), xanthine oxidase (XO) inhibitory effect and the ability to delay the linoleic acidperoxidation process (ALP). The aqueous decoction was partitioned obtaining four extracts and the n-butanol extract showed the highestantioxidant activity and the highest total phenolic content. Phytochemical investigation leads to the isolation of thirteen secondarymetabolites including simple phenolics, flavonoids, secoiridoids whose structures were elucidated by spectroscopic data (1D and 2DNMR) and spectrometric techniques. A significant free radical scavenging effect against DPPH has been evidenced in fraxamoside (1)(EC50 62.6 µM) and taxifolin (5) (EC50 50.0 µM), isolated for the first time from the water decoction. The most active compound in theTAC evaluation, was the 3,4 dihydro-phenyl glycol (8) (0.90 caffeic acid equiv.) while taxifolin and fraxamoside resulted as the mostefficient inhibitors of XO activity (IC50 2.7 and 5.2 µM, respectively). Secoxyloganin (4), oleuropein (2) and tyrosol (6) showed thehighest ALP activity. This study adds to the growing body of data supporting the bioactivities of phytochemicals and their potentialimpact on human health.

Intracellular Distribution and Biological Effects of Phytochemicals in a Sex Steroid- Sensitive Model of Human Prostate Adenocarcinoma by Antonella Smeriglio, Domenico Trombetta, Daniele Marcoccia, Laura Narciso, Alberto Mantovani, Stefano Lorenzetti (1386-1396).
Prostate function is critical for male fertility and its well-known oncological biomarker, namely Prostate-Specific Antigen(PSA), can be also used to monitor prostate epithelial human cells upon treatment with pharmaceutical drugs or natural bioactivecompounds.;The LNCaP human prostate cell line was previously set up as a model system to investigate chemicals affecting prostate epitheliumfunctionality by means of a tiered approach integrating two different toxicological endpoints, cell viability (MTS) and PSA secretionassays. Here, the same approach has been used to characterize the biological effects of phytochemicals on prostate epithelium. The antiandrogenicability of phytochemicals to inhibit DHT-induced PSA secretion has been investigated also characterizing their intracellulardistribution, in the presence or absence of sex steroids. Intracellular distribution allows to verify whether and to which extent eachphytochemical is able to enter the cell and to reach the nucleus, the latter being the target of the supposed transcriptional modulatoryactivity upon phytochemicals' binding to sex steroid receptors.;Some phytochemicals, supposed to have a role in the functionality of the prostate epithelium, have been tested in a dose-dependentmanner in both MTS and PSA secretion assays. In parallel, to establish the “effective concentration”, in comparison to the “nominalone”, the intracellular amount of each phytochemical has been assessed upon cell fractionation of LNCaP-treated cells and subsequentchromatographic measurements.

Anticancer and Antibacterial Activity of Hyperforin and Its Derivatives by Brigida Immacolata Pia Schiavone, Luisella Verotta, Antonio Rosato, Muraglia Marilena, Simon Gibbons, Ezio Bombardelli, Carlo Franchini, Filomena Corbo (1397-1401).
Hyperforin is a natural phloroglucinol that has been known for the treatment of depression. Hyperforin displays alsoantibacterial, antiproliferant and antiangiogenic activity. Synthetic derivatives of hyperforin have also recently been reported to possessincreased bioactivity. The clinical applications are limited by the hydrophobic characteristics and the instability of the molecule. In thisreview we discuss about some of the derivatives of hyperforin (aristoforin, tetrahydrohyperforin and octahydrohyperforin) thatdemonstrated promising antitumor activity. Among these, octahydrohyperforin also possesses antibacterial activity against both theplanktonic and biofilm states of bacteria.

Bergamot Juice Extract Inhibits Proliferation by Inducing Apoptosis in Human Colon Cancer Cells by Giuseppa Visalli, Nadia Ferlazzo, Santa Cirmi, Pietro Campiglia, Sebastiano Gangemi, Angela Di Pietro, Gioacchino Calapai, Michele Navarra (1402-1413).
Colorectal cancer (CRC) is a leading cause of cancer mortality in the industrialized world, second to lung cancer. A lot ofevidences highlight that a diet rich in fruits and vegetables may reduce the risk of some types of cancer including CRC. In this study wedemonstrate that Citrus bergamia juice extracts (BJe) reduces CRC cell growth by multiple mechanisms. Low BJe concentrations inhibitMAPKs pathway and alter apoptosis-related proteins, that in turn induce cell cycle arrest and apoptosis in HT-29 cells. Instead, highconcentrations of BJe induce oxidative stress causing DNA damage. Our study highlights the role of BJe as modulator of cell apoptosis inCRC cells and strengthens our previous hypothesis that the flavonoid fraction of bergamot juice may play a role as anti-cancer drug.

Breast cancer (BC) is the leading cause of death among women all over the world. Estrogen receptor (ER) based therapy is oneof the major approaches to target BC and is associated with various problems such as primary as well as secondary resistance. ERsignaling is a complex pathway as many factors are involved; including several types of ERs and their associated co-regulators.Increasing understanding of ER signals results in new approaches targeting towards BCs. In this context, ER co-regulators have beenexplored and many modulators of ER co-regulators have been found out. EGFR and mTOR pathways also have significant impact on BCendocrine therapy because of the complex crosstalk mechanism which is responsible for primary and secondary resistance. Triplenegative breast cancer (TNBC) is majorly associated with BRCA mutations. Currently there is no approved targeted therapy available insuch form of cancer. Although PARP inhibitors seem to be suitable candidates for it. The present review is focused on the currentscenario of ER, EGFR, as well as mTOR signaling target therapy. We have also discussed the current status of PARP inhibitors in BCchemotherapy.

3-(Aminoalkylamino)-1,2,4-benzotriazine-1,4-dioxide-extended derivatives were synthesized by the structural modification of3-amino-1,2,4-benzotriazine-1,4-dioxide (tirapazamine, TPZ) that incorporated homologue-alkyl linkers, without or with an extended 3-amino-1,2,4-benzotriazine-1-oxide moiety at the 3-position of the TPZ. According to sequential evaluation of preferentially normoxicand hypoxic cytotoxicities against MCF-7, NCI-H460 and HCT-116, most of the synthesized compounds exhibited hypoxic cytotoxicitygreater than or comparable to that of TPZ. Among them, compounds 9a and 9b more powerfully inhibited the proliferation of MCF-7,NCI-H460 and HCT-116 in hypoxia than did TPZ. The representative of 3-(aminoalkylamino)-1,2,4-benzotriazine-1,4-dioxide-extendedderivatives, 9a exhibited greater hypoxic cytotoxicity than TPZ, mediated by cell cycle arrest. The induction of DNA damage, theactivation of caspase 3/7 and cleaved poly(ADP-ribose) polymerase-related apoptosis, which were detected in HCT-116 cells in bothnormoxia and hypoxia. In vitro anti-angiogenic assay of co-cultured HUVECs and fibroblasts that were exposed to the selected 7b, 8g,9a and 9b exhibited 80-90% inhibition of tube formation at 20 µM, whereas TPZ exhibited approximately 50% inhibition oftube formation at 20 µM. At 2 µM, 9a and 9b significantly reduced the areas, lengths, paths and joints of tube formation by 70-80% and45-50%, respectively. These results reveal that most of synthesized TPZ derivatives in this study exhibited more potent anti-angiogenesisthan TPZ.