Double Attack to Oxidative Stress in Neurodegenerative Disorders: MAO-B and Nrf2 as Elected Targets

Oxidative stress and neuroinflammation play a pivotal role in triggering the neurodegenerative pathological cascades which characterize neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases. In search for potential efficient treatments for these pathologies, that are still considered unmet medical needs, we started from the promising properties of the antidiabetic drug pioglitazone, which has been repositioned as an MAO-B inhibitor, characterized by promising neuroprotective properties. Herein, with the aim to broaden its neuroprotective profile, we tried to enrich pioglitazone with direct and indirect antioxidant properties by hanging polyphenolic and electrophilic features that are able to trigger Nrf2 pathway and the resulting cytoprotective genes' transcription, as well as serve as radical scavengers. After a preliminary screening on MAO-B inhibitory properties, caffeic acid derivative 2 emerged as the best inhibitor for potency and selectivity over MAO-A, characterized by a reversible mechanism of inhibition. Furthermore, the same compound proved to activate Nrf2 pathway by potently increasing Nrf2 nuclear translocation and strongly reducing ROS content, both in physiological and stressed conditions. Although further biological investigations are required to fully clarify its neuroprotective properties, we were able to endow the pioglitazone scaffold with potent antioxidant properties, representing the starting point for potential future pioglitazone-based therapeutics for neurodegenerative disorders.

From Monoamine Oxidase Inhibition to Antiproliferative Activity: New Biological Perspectives for Polyamine Analogs

Monoamine oxidases (MAOs) are well-known pharmacological targets in neurological and neurodegenerative diseases. However, recent studies have revealed a new role for MAOs in certain types of cancer such as glioblastoma and prostate cancer, in which they have been found overexpressed. This finding is opening new frontiers for MAO inhibitors as potential antiproliferative agents. In light of our previous studies demonstrating how a polyamine scaffold can act as MAO inhibitor, our aim was to search for novel analogs with greater inhibitory potency for human MAOs and possibly with antiproliferative activity. A small in-house library of polyamine analogs (2-7) was selected to investigate the effect of constrained linkers between the inner amine functions of a polyamine backbone on the inhibitory potency. Compounds 4 and 5, characterized by a dianiline (4) or dianilide (5) moiety, emerged as the most potent, reversible, and mainly competitive MAO inhibitors (Ki < 1 μM). Additionally, they exhibited a high antiproliferative activity in the LN-229 human glioblastoma cell line (GI50 < 1 μM). The scaffold of compound 5 could represent a potential starting point for future development of anticancer agents endowed with MAO inhibitory activity.

2-Hydroxyoleic Acid as a Self-Assembly Inducer for Anti-Cancer Drug-Centered Nanoparticles

A potent nontoxic antitumor drug, 2-hydroxyoleic acid (6, 2OHOA) used for membrane lipid therapy, was selected as a self-assembly inducer due to its ability to form nanoparticles (NPs) in water. For this purpose, it was conjugated with a series of anticancer drugs through a disulfide-containing linker to enhance cell penetration and to secure drug release inside the cell. The antiproliferative evaluation of the synthesized NP formulations against three human tumor cell lines (biphasic mesothelioma MSTO-211H, colorectal adenocarcinoma HT-29, and glioblastoma LN-229) showed that nanoassemblies 16-22a,bNPs exhibit antiproliferative activity at micromolar and submicromolar concentrations. Furthermore, the ability of the disulfide-containing linker to promote cellular effects was confirmed for most nanoformulations. Finally, 17bNP induced intracellular ROS increase in glioblastoma LN-229 cells similarly to free drug 8, and such elevated production was decreased by pretreatment with the antioxidant N-acetylcysteine. Also, nanoformulations 18bNP and 21bNP confirmed the mechanism of action of the free drugs.

Dual targeted 2-Benzylideneindanone pendant hydroxamic acid group exhibits selective HDAC6 inhibition along with tubulin stabilization effect

Abnormal epigenetics has been recognised as an early event in tumour progression and aberrant acetylation of lysine in particular has been understood in tumorigenesis. Therefore, it has become an attractive target for anticancer drug development. However, HDAC inhibitors have limited success due to toxicity and drug resistance concerns. Present study deals with design and synthesis of bivalent indanone based HDAC6 and antitubulin ligands as anticancer agents. Two of the analogues 9 and 21 exhibited potent antiproliferative activities (IC₅₀, 0.36-3.27 µM) and high potency against HDAC 6 enzyme. Compound 21 showed high selectivity against HDAC 6 while 9 exhibited low selectivity. Both the compounds also showed microtubule stabilization effects and moderate anti-inflammatory effect. Dual targeted anticancer agents with concomitant anti-inflammatory effects will be more attractive clinical candidates in future.

Coinage Metal Compounds With 4-Methoxy-Diphenylphosphane Benzoate Ligand Inhibit Female Cancer Cell Growth

In the continuous effort to find new metal-based compounds as alternatives to platinum-related anticancer drugs, 11th group metal phosphane compounds have been thoroughly taken into consideration. Tris-arylphosphane metal derivatives have been extensively considered as heteroleptic metal compounds exhibiting remarkable cytotoxic activities. Functional groups in the aryl moieties modulate the activity reinforcing or eliminating it. Previous works have highlighted that the presence of hydrophilic groups in the phosphane ligands, such as COOH or OH, hampers the anticancer activity of gold azolate/PPh3 compounds. To increase the polarity of the triarylphosphane ligand without affecting the activity, we considered the preparation of esters starting from the 4-diphenylphosphane-benzoic acid. The resulting phosphanes are poorer donators than the PPh3, leading to poly-phosphane M(I) compounds, and they exhibit intense emissive properties. A homologous series of L3MX-type compounds (where M = Au and X = Cl, M = Cu and X = BF4, and M = Ag and X = PF6) were obtained with the 4-methoxy-diphenylphosphane benzoate. The homologous metal compounds have been characterized by analytical and spectroscopic methods and, remarkably, their formation was associated with high frequencies of 31P NMR chemical shift variations (5–35 ppm in CDCl3). The new complexes and the ligand were evaluated on sensitive and cisplatin-resistant human tumor cell lines. The ligand is ineffective on cells while the complexes exert a notable antiproliferative effect. The homologous series of the L3MX complexes were able to significantly reduce the cell viability of human triple-negative breast cancer cells (MDA-MB-231), representing the most aggressive subtype of breast cancer, and of ovarian carcinoma (A2780). Among these coinage metal compounds, L3AgPF6 results the most interesting, showing the lowest GI50 values in all cell lines. Interestingly, this silver complex is more cytotoxic than cisplatin, taken as reference drug. The investigation of the mechanism of action of L3AgPF6 in A2780 cells highlighted the induction of the apoptotic pathway, the depolarization of the mitochondrial inner membrane, and a significant accumulation in cells.

Biological properties of aqueous extract and pyranocoumarins obtained from the bark of Brosimum alicastrum tree

ETHNOPHARMACOLOGICAL RELEVANCE

Brosimum alicastrum is a tree used in Mexican traditional medicine for the treatment of several diseases, including uterine cancer.

AIM OF THE STUDY

In this study, the cytotoxic activity of aqueous extract of B. alicastrum bark and isolated compounds xanthyletin (1), luvangetin (2), and 8-hydroxyxanthyletin (3) on three human cancer cell lines was determined. Moreover, the biological effects of 8-hydroxyxanthyletin (3) were investigated.

MATERIALS AND METHODS

The aqueous extract was prepared according to the ethnomedical information reported from the bark. The compounds were purified using chromatographic methods and their structures were elucidated by spectroscopic techniques. The antiproliferative effect of aqueous extract and isolates was determined in three human tumor cell lines: HeLa, A2780, and MSTO-211H, and evaluated by trypan blue exclusion assay. The cell cycle and the mitochondrial transmembrane potential (ΔΨ) were measured by flow cytometry, while Reactive Oxygen Species (ROS) levels were determined using 2',7'-dichlorofluorescein diacetate (DCFH-DA) probe. The effect on the relaxation activity, mediated by topoisomerase I and II, was evaluated by electrophoresis, and docking studies were performed using Autodock 4.2 to analyze the interactions.

RESULTS

Aqueous extract of B. alicastrum bark showed significant antiproliferative effect on the evaluated cancer cell lines (IC₅₀ = 1.6, 8.5, and 21.4 μg/ml). Four coumarins were identified in the extract and three of them were also evaluated. A2780 cell line exhibited higher sensitivity against pyranocoumarins with IC₅₀ values ranging from 32 to 47 μmol/l. 8-hydroxyxanthyletin (3) exerts an interesting effect on human topoisomerases I and II, by inhibiting the enzymes at concentrations comparable to those obtained in antiproliferative assay. Moreover, 8-hydroxyxanthyletin (3) arrests the cell cycle at G₀/G₁ phase and induces in A2780 cells a concentration-dependent increase in ROS levels. The results of molecular docking suggest the participation of the hydroxyl group in the interaction between 8-hydroxyxanthyletin (3) and topoisomerase I and II.

CONCLUSION

This is the first report that demonstrates the cytotoxic activity of the aqueous extract of B. alicastrum bark, and determines the main metabolites.

trans-Dichloro(triphenylarsino)(N,N-dialkylamino)platinum(II) Complexes: In Search of New Scaffolds to Circumvent Cisplatin Resistance

The high incidence of the resistance phenomenon represents one of the most important limitations to the clinical usefulness of cisplatin as an anticancer drug. Notwithstanding the considerable efforts to solve this problem, the circumvention of cisplatin resistance remains a challenge in the treatment of cancer. In this work, the synthesis and characterization of two trans-dichloro(triphenylarsino)(N,N-dialkylamino)platinum(II) complexes (1 and 2) were described. The trypan blue exclusion assay demonstrated an interesting antiproliferative effect for complex 1 in ovarian carcinoma-resistant cells, A2780cis. Quantitative analysis performed by ICP-AES demonstrated a scarce ability to platinate DNA, and a significant intracellular accumulation. The investigation of the mechanism of action highlighted the ability of 1 to inhibit the relaxation of supercoiled plasmid DNA mediated by topoisomerase II and to stabilize the cleavable complex. Cytofluorimetric analyses indicated the activation of the apoptotic pathway and the mitochondrial membrane depolarization. Therefore, topoisomerase II and mitochondria could represent possible intracellular targets. The biological properties of 1 and 2 were compared to those of the related trans-dichloro(triphenylphosphino)(N,N-dialkylamino)platinum(II) complexes in order to draw structure–activity relationships useful to face the resistance phenotype.

Promising Non-cytotoxic Monosubstituted Chalcones to Target Monoamine Oxidase-B

A library of monosubstituted chalcones (1-17) bearing electron-donating and electron-withdrawing groups on both aromatic rings were selected. The cell viability on human tumor cell lines was evaluated first. The compounds unable to induce detectable cytotoxicity (1, 13, and 14) were tested using the monoamine oxidase (MAO) activity assay. Interestingly, they inhibit MAO-B, acting as competitive inhibitors, with 13 and 14 showing the best profiles. In particular, 13 exhibited a potency higher than that of safinamide, taken as a reference. Docking studies and crystallographic analysis showed that in human MAO-B 13 binds with the halogen-substituted aromatic ring in the entrance cavity, similar to safinamide, whereas 14 is accommodated in the opposite way. The main conclusion of this cell biology, biochemistry, and structural study is to highlights 13 as a chalcone derivative that is worth consideration for the development of novel MAO-B-selective inhibitors for the treatment of neurodegenerative diseases.

New Platinum(II) Complexes Affecting Different Biomolecular Targets in Resistant Ovarian Carcinoma Cells

Resistance to platinum-based anticancer drugs represents an important limit for their clinical effectiveness and one of the most important field of investigation in the context of platinum compounds. From our previous studies, PtII complexes containing the triphenylphosphino moiety have been emerging as promising agents, showing significant cytotoxicity to resistant ovarian carcinoma cells. Two brominated triphenylphosphino trans-platinum derivatives were prepared and evaluated on human tumor cell lines, sensitive and resistant to cisplatin. The new complexes exert a notable antiproliferative effect on resistant ovarian carcinoma cells, showing a remarkable intracellular accumulation and the ability to interact with different intracellular targets. The interaction with DNA, the collapse of mitochondrial transmembrane potential, and the impairment of intracellular redox state were demonstrated. Moreover, a selectivity towards the selenocysteine of thioredoxin reductase was observed. The mechanism of action is discussed with regard to the resistance phenomenon in ovarian carcinoma cells.

Design, physico-chemical characterization and in vitro biological activity of organogold(III) glycoconjugates

To develop new metal-based glycoconjugates as potential anticancer agents, four organometallic gold(iii)-dithiocarbamato glycoconjugates of the type [AuIII(2-Bnpy)(SSC-Inp-GlcN)](PF6) (2-Bnpy: 2-benzylpyridine; Inp: isonipecotic moiety; GlcN: amino-glucose scaffold; Au3-Au6) and the corresponding model non-glycosylated counterparts [AuIII(2-Bnpy)(SSC-Inp-R)](PF6) (R: OEt (Au1), NH2 (Au2)) have been generated and characterized by means of several analytical techniques (elemental analysis, FT-IR, 1H-/13C-NMR, ESI-MS, UV-Vis, X-ray crystallography). Their stability under physiologically-relevant conditions (PBS solution) and n-octanol/PBS distribution coefficient (D7.4) have also been evaluated. Gold(iii) glycoconjugates showed an antiproliferative effect against ovarian carcinoma A2780 cells, with GI50 values in the low micromolar range. Remarkably, their cell growth inhibitory effect increases upon the addition of a glucose transporter 1 (GLUT1) inhibitor, thus ruling out the involvement of GLUT1 in their transport inside the cell. Additional mechanistic studies have been carried out in A2780 cells, supporting the hypothesis of a facilitated diffusion mechanism (possibly mediated by glucose transporters other than GLUT1), and revealing their capability to act as topoisomerase I and II inhibitors and to disrupt mitochondrial membrane integrity, leading to the generation of ROS, thus resulting in the promotion of oxidative stress and, eventually, cell death.

Cytotoxicity and DNA interaction in a series of aryl terminated iminopyridine Pt(II) complexes

A series of iminopyridine complexes of platinum(II), bearing a flexible diethereal, aryl terminated residue, where the size of aryl group is varied from phenyl to 9-anthracenyl, was synthesized. The new complexes are soluble and stable in DMSO/H₂O mixtures. Besides the metal center, aryl groups are available for further interactions with DNA, due to the good side chain flexibility. The new aryl functionalized iminopyridine dichlorido platinum(II) complexes show a significant antiproliferative activity on ovarian carcinoma cells and notably, complex 13 is able to overcome cisplatin resistance. The study of the interaction mode of 13 with DNA highlighted the ability to form a molecular complex characterized by a dual (intercalative and groove binding) geometry. The complex is also able to covalently add to DNA even though interstrand cross-links appear significantly hampered with respect to cisplatin. The interactions with the macromolecule are discussed in view of the observed cell effect.

Biological Properties of New Chiral 2-Methyl-5,6,7,8-tetrahydroquinolin-8-amine-based Compounds

The synthesis of a small library of 8-substituted 2-methyl-5,6,7,8-tetrahydroquinoline derivatives is presented. All the compounds were tested for their antiproliferative activity in non-cancer human dermal microvascular endothelial cells (HMEC-1) and cancer cells: human T-lymphocyte cells (CEM), human cervix carcinoma cells (HeLa), human dermal microvascular endothelial cells (HMEC-1), colorectal adenocarcinoma (HT-29), ovarian carcinoma (A2780), and biphasic mesothelioma (MSTO-211H). Compounds 3a, 5a, and 2b, showing significant IC₅₀ values against the whole panel of the selected cells, were further synthesized and tested as pure enantiomers in order to shed light on how their stereochemistry might impact on the related biological effect. The most active compound (R)-5a was able to affect cell cycle phases and to induce mitochondrial membrane depolarization and cellular ROS production in A2780 cells.

Modulation of relaxation activity of human topoisomerases by Pt(II)-based complexes

The clinical efficiency of Pt(II)-based drugs is founded on articulate mechanisms of action. Indeed it depends on a balanced combination of metal ion reactivity towards proteins and nucleic acids. Here we analysed the effect of two trans-platinum planar amines in comparison to cisplatin and transplatin on the DNA processivity by human topoisomerases I and IIα. Each tested metal complex produces DNA adducts with unique geometrical features and, consistently, they exert different effects on the activity of tested enzymes. Moreover, our results highlighted more subtle consequences on the enzymatic activity by the tested metal complexes which derive from a combination of preferential DNA or protein platination. Moreover, we observed that it is not possible to predict the overall output based only on the cis- vs trans- geometry of the tested metal complexes. This variable behaviour reflects the chemical reactivity profile of each single metal complex and can be usefully addressed to describe their different properties in the complex physiological environment.

Synthesis, Antiproliferative Effect, and Topoisomerase II Inhibitory Activity of 3-Methyl-2-phenyl-1H-indoles

A series of 3-methyl-2-phenyl-1H-indoles was prepared and investigated for antiproliferative activity on three human tumor cell lines, HeLa, A2780, and MSTO-211H, and some structure-activity relationships were drawn up. The GI₅₀ values of the most potent compounds (32 and 33) were lower than 5 μM in all tested cell lines. For the most biologically relevant derivatives, the effect on human DNA topoisomerase II relaxation activity was investigated, which highlighted the good correlation between the antiproliferative effect and topoisomerase II inhibition. The most potent derivative, 32, was shown to induce the apoptosis pathway. The obtained results highlight 3-methyl-2-phenyl-1H-indole as a promising scaffold for further optimization of compounds with potent antiproliferative and antitopoisomerase II activities.

New Class of Betulinic Acid-Based Nanoassemblies of Cabazitaxel, Podophyllotoxin, and Thiocolchicine

Betulinic acid is validated as a new self-assembly inducer for the formation of nanoparticles (NPs) in combination with different drugs. The target compounds are characterized by the presence of anticancer drugs acting on tubulin dynamics and of a linker that could be a carbon chain or a triazole-based one. Nanoparticles formed are characterized and their biological activity is evaluated.

Aged garlic extract and its constituent, S-allyl-L-cysteine, induce the apoptosis of neuroblastoma cancer cells due to mitochondrial membrane depolarization

Aged garlic extract (AGE) has been demonstrated to have therapeutic properties in tumors; however its mechanisms of action have not yet been fully elucidated. A previous study revealed that AGE exerts an anti-proliferative effect on a panel of both sensitive [wild-type (WT)] and multidrug-resistant (MDR) human cancer cells. Following treatment of the cells with AGE, cytofluorimetric analysis revealed the occurrence of dose-dependent mitochondrial membrane depolarization (MMD). In this study, in order to further clarify the mechanisms of action of AGE, the effects of AGE on mitochondria isolated from rat liver mitochondria (RLM) were also examined. AGE induced an effect on the components of the electrochemical gradient (Δµ_H⁺), mitochondrial membrane potential (ΔΨ_m) and mitochondrial electrochemical gradient (ΔpH_m). The mitochondrial membrane dysfunctions of RLM induced by AGE, namely the decrease in both membrane potential and chemical gradient were associated with a higher oxidation of both the endogenous glutathione and pyridine nucleotide content. To confirm the anti-proliferative effects of AGE, experiments were performed on the human neuroblastoma (NB) cancer cells, SJ-N-KP and the MYCN-amplified IMR5 cells, using its derivative S-allyl-L-cysteine (SAC), with the aim of providing evidence of the anticancer activity of this compound and its possible molecular mechanism as regards the induction of cytotoxicity. Following treatment of the cells with SAC at 20 mM, cell viability was determined by MTT assay and apoptosis was detected by flow cytometry, using Annexin V-FITC labeling. The percentages of cells undergoing apoptosis was found to be 48.0% in the SJ-N-KP and 50.1% in the IMR5 cells. By cytofluorimetric analysis, it was suggested that the target of SAC are the mitochondria. Mitochondrial activity was examined by labeling the cells with the probe, 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylimidacarbocyanine iodide (JC-1). Following treatment with SAC at 50 mM, both NB cell lines exhibited a marked increase in MMD. On the whole, the findings of this study indicate that both natural products, AGE and SAC, cause cytotoxicity to tumor cells via the induction of mitochondrial permeability transition (MPT).

The neuroleptic drug fluphenazine induces a significant UVA-mediated cytotoxic effect on three human cancer cell lines through apoptosis

The cytotoxic activity of fluphenazine (FPZ) in combination with UVA light was evaluated on three human tumor cell lines, HeLa, MSTO-211H and A431. The photobiological effect was determined following irradiation treatment in the presence of/or after the removal of incubated FPZ. Under both conditions, FPZ proved to be very effective in killing tumor cells, with GI₅₀ values in the micromolar range. However, when FPZ was present during irradiation, the photocytotoxicity was at least two times higher than that after its removal suggesting the contribution of the drug both outside and inside the cells. The uptake of FPZ was very fast and, after only 15 minutes of incubation, the compound was accumulated inside lysosomes, as evidenced through fluorescence microscopy. FPZ distribution covered also the nucleus and the cytoplasm without significant plasma membrane association. After irradiation, the membrane of lysosomes in which FPZ was accumulated lost its integrity suggesting that the released lysosomal enzymes played an important role in cell death, and mitochondria were damaged as well, following apoptosis. Indeed, cytofluorimetric studies demonstrated that apoptosis was the main mechanism of cell death. Finally, an extremely high production of ROS was found, indicating a significant photodynamic mechanism involved in the photocytotoxic effect of FPZ. Taken together, our data show that FPZ following UVA irradiation behaves as an effective photoantiproliferative compound inducing apoptosis on various human tumor cells.

2-Phenyloxazole-4-carboxamide as a Scaffold for Selective Inhibition of Human Monoamine Oxidase B

A series of 2-phenyloxazoles bearing an amide group at position 4 were designed and synthesized for evaluation as potential inhibitors of human recombinant monoamine oxidases (hrMAOs). Results of kinetics experiments demonstrated that all compounds behave as competitive MAO inhibitors, with good selectivity toward the MAO-B isoform. The most potent and selective derivatives are characterized by inhibition constant (K_i ) values in the sub-micromolar range and a good selectivity index (K_i MAO-A /K_i MAO-B >50). Some derivatives were also found to be able to inhibit MAO activity in nerve growth factor (NGF)-differentiated PC12 cells, taken as a model of neuronal cells. In particular, 2-(2-hydroxyphenyl)-N-phenyloxazole-4-carboxamide (compound 4 a) may be a promising new scaffold, exerting the highest selectivity and inhibitory effect toward MAOs in NGF-differentiated PC12 cell lysates, without compromising cell viability. Molecular docking analysis allowed a rationalization of the experimentally observed binding affinity and selectivity.

Unravelling the Antiproliferative Activity of 1,2,5-oxadiazole Derivatives

AIM

To develop several new derivatives aimed to complete the studies concerning the antiproliferative profile of the oxadiazole derivative MD77.

MATERIALS AND METHODS

The substitution pattern around the phenyl rings of this compound was analyzed through the synthesis of positional isomers and of analogues bearing different substituents at the para positions (2-12).

RESULTS

The results of the antiproliferative activity of these derivatives versus HCT-116 and HeLa cancer cell lines shed light on the effects of the presence, nature and position of such substituents. Notably, derivative 4, a regioisomer of 1 in which the substituents at the para positions of the phenyl rings were inverted, showed the best antiproliferative profile, exhibiting a significant activity also against MCF7 and MDA-MB 468 cancer cell lines.

CONCLUSION

Preliminary results showed the ability of compound 4 to reduce the viability of cancer cells by counteracting human recombinant topoisomerase II α relaxation activity.

Cytotoxic Acetogenins from the Roots of Annona purpurea

Annona purpurea, known in Mexico as "cabeza de negro" or "ilama", belongs to the Annonaceae family. Its roots are employed in folk medicine in several regions of Mexico. Taking that information into account, a chemical and biological analysis of the components present in the roots of this species was proposed. Our results demonstrated that the dichloromethane (DCM) extract was exclusively constituted by a mixture of five new acetogenins named annopurpuricins A-E (1-5). These compounds have an aliphatic chain of 37 carbons with a terminal α,β unsaturated γ-lactone. Compounds 1 and 2 belong to the adjacent bis-THF (tetrahydrofuran) α-monohydroxylated type, while compounds 3 and 4 belong to the adjacent bis-THF α,α'-dihydroxylated type; only compound 5 possesses a bis-epoxide system. Complete structure analysis was carried out by spectroscopy and chemical methods. All compounds were evaluated for their antiproliferative activity on three human tumor cell lines (MSTO-211H, HeLa and HepG2). Compounds 1-4 inhibited significantly the growth of HeLa and HepG2 cells, showing GI50 values in the low/subnanomolar range, while 5 was completely ineffective under the tested conditions. The investigation of the mechanism of action responsible for cytotoxicity revealed for the most interesting compound 1 the ability to block the complex I activity on isolated rat liver mitochondria (RLM).

Discovery of Pyrido[3',2':5,6]thiopyrano[4,3-d]pyrimidine-Based Antiproliferative Multikinase Inhibitors

Protein kinases dysregulation is extremely common in cancer cells, and the development of new agents able to simultaneously target multiple kinase pathways involved in angiogenesis and tumor growth may offer several advantages in the treatment of cancer. Herein we report the discovery of new pyridothiopyranopyrimidine derivatives (2-4) showing high potencies in VEGFR-2 KDR inhibition as well as antiproliferative effect on a panel of human tumor cell lines. Investigation on the selectivity profile of the representative 2-anilino-substituted compounds 3b, 3i, and 3j revealed a multiplicity of kinase targets that should account for the potent antiproliferative effect produced by these pyridothiopyranopyrimidine derivatives.

Self-assembling Releasable Thiocolchicine-Diphenylbutenylaniline Conjugates

The design and the synthesis of new self-assembling conjugates is reported. The target compounds are characterized by the presence of a self-immolative linker that secures a controlled release induced by lipase cleavage. 4-(1,2-Diphenylbut-1-en-1-yl)aniline is used as a self-assembling inducer and amino-thiocolchicine as prototype of drug. The release of thiocolchicine derivative has been demonstrated in vitro in the presence of porcine pancreatic lipase and Celite-supported lipase. The formation of nanoparticles is confirmed by dynamic light scattering, atomic force microscopy, and fluorescence microscopy. The antiproliferative activity has been proved on two human cancer cell lines.

Benzothiopyranoindole- and pyridothiopyranoindole-based antiproliferative agents targeting topoisomerases

New benzothiopyranoindoles (5a-l) and pyridothiopyranoindoles (5m-t), featuring different combinations of substituents (H, Cl, OCH₃) at R²-R⁴ positions and protonatable R¹-dialkylaminoalkyl chains, were synthesized and biologically assayed on three human tumor cell lines, showing significant antiproliferative activity (GI₅₀ values spanning from 0.31 to 6.93 μM) and pro-apoptotic effect. Linear flow dichroism experiments indicate the ability of both chromophores to form a molecular complex with DNA, following an intercalative mode of binding. All compounds displayed a moderate ability to inhibit the relaxation activity of both topoisomerases I and II, reasonably correlated to their intercalative capacities. Cleavable assay performed with topoisomerase I revealed a significant poisoning effect for compounds 5g, 5h, 5s, and 5t. A theoretical model provided by hydrated docking calculations clarified the role of the R¹-R⁴ substituents on the topoisomerase I poison activity, revealing a crucial role of the R²-OCH₃ group.

Exploring the Biological Activity of a Library of 1,2,5-Oxadiazole Derivatives Endowed With Antiproliferative Activity

BACKGROUND/AIM

The identification of a series of oxadiazole-based compounds, as promising antiproliferative agents, has been previously reported. The aim of this study was to explore the SAR of newly-synthesized oxadiazole derivatives and identify their molecular targets.

MATERIALS AND METHODS

A small library of 1,2,5-oxadiazole derivatives was synthetized and their antiproliferative activity was tested by the MTT assay. Their interaction with topoisomerase I was evaluated and a molecular docking study was performed.

RESULTS

Several candidates showed cytotoxicity towards two human tumor cell lines, HCT-116 (colorectal carcinoma) and HeLa (cervix adenocarcinoma). Some derivatives exhibited inhibitory effects on the catalytic activity of topoisomerase I and this effect was supported by docking studies.

CONCLUSION

The enzyme inhibition results, although not directly related to cytotoxicity, suggest that a properly modified 1,2,5 oxadiazole scaffold could be considered for the development of new anti-topoisomerase agents.

The antioxidant, aged garlic extract, exerts cytotoxic effects on wild-type and multidrug-resistant human cancer cells by altering mitochondrial permeability

Aged garlic extract (AGE) has been shown to possess therapeutic properties in cancer; however its mechanisms of action are unclear. In this study, we demonstrate by MTT assay that AGE exerts an anti-proliferative effect on a panel of both sensitive and multidrug-resistant (MDR) human cancer cell lines and enhances the effects of hyperthermia (42˚C) on M14 melanoma cells. The evaluation of the mitochondrial activity in whole cancer cells treated with AGE, performed by cytofluorimetric analysis in the presence of the lipophilic cationic fluorochrome JC-1, revealed the occurrence of dose-dependent mitochondrial membrane depolarization. Membrane potential was measured by the TPP+ selective electrode. In order to shed light on its mechanisms of action, the effects of AGE on isolated rat liver mitochondria were also examined. In this regard, AGE induced a mitochondrial membrane hyperpolarization of approximately 15 mV through a mechanism that was similar to that observed with the ionophores, nigericin or salinomycin, by activating an exchange between endogenous K+ with exogenous H+. The prolonged incubation of the mitochondria with AGE induced depolarization and matrix swelling, indicative of mitochondrial permeability transition induction that, however, occurs through a different mechanism from the well-known one. In particular, the transition pore opening induced by AGE was due to the rearrangement of the mitochondrial membranes following the increased activity of the K+/H+ exchanger. On the whole, the findings of this study indicate that AGE exerts cytotoxic effects on cancer cells by altering mitochondrial permeability. In particular, AGE in the mitochondria activates K+/H+ exchanger, causes oxidative stress and induces mitochondrial permeability transition (MPT).

Anticancer Gold(III) Peptidomimetics: From Synthesis to in vitro and ex vivo Biological Evaluations

Five new Au^III -peptidodithiocarbamato complexes of the type [Au^III Br₂ (dtc-AA₁ -AA₂ -OR] (in which AA₁ =N-methylglycine (Sar), l/d-Pro; AA₂ =l/d-Ala, α-aminoisobutyric acid (Aib); R=OtBu, triethylene glycol methyl ether), differing with regard to the amino acid sequence and/or the chiral amino acid configuration, were designed to enhance tumor selectivity and bioavailability. The gold(III)-based moiety was functionalized to exploit the targeting properties of the peptidomimetic ligand toward two peptide transporters (namely PEPT1 and PEPT2), which are upregulated in several tumor cells. The compounds were synthesized and fully characterized, mainly by means of elemental analysis, one- and two-dimensional NMR spectroscopy, FT-IR, and UV/Vis spectrophotometry. The crystal structures of three compounds were also solved by X-ray diffraction. In vitro cytotoxicity studies using a panel of human tumor cell lines (A549 [non-small-cell lung carcinoma], MCF-7 [breast cancer], A2780 [ovarian carcinoma], H1975 [non-small-cell lung carcinoma], H460 [large-cell lung carcinoma], and A431 [human epidermoid carcinoma]) showed the dtc-Pro-Aib-OtBu derivative to be very effective, with GI₅₀ values much lower than those of cisplatin. This complex was thus selected for evaluating stability under physiological conditions and possible interactions with serum albumin, as well in PARP-1 enzyme inhibition assays and preliminary ex vivo toxicity experiments on healthy rat tissues.

Heteronanoparticles by Self-Assembly of Ecdysteroid and Doxorubicin Conjugates To Overcome Cancer Resistance

Heteronanoparticles (H-NPs) consisting of conjugates characterized by a squalene tail linked to doxorubicin and ecdysteroid derivatives are presented. Biological evaluation on A2780ADR cell line confirms not only the maintenance of the activity of the parental drug but also the ability to overcome cancer resistance. The in vitro cell uptake was demonstrated, and the involvement of an endosomal-mediated pathway was suggested.

New insights in the structure-activity relationships of 2-phenylamino-substituted benzothiopyrano[4,3-d]pyrimidines as kinase inhibitors

Inhibition of angiogenesis via blocking vascular endothelial growth factor receptor (VEGFR) signaling pathway emerged as an established approach in anticancer therapy. So far, many monoclonal antibodies and ATP-competitive small molecule inhibitors have been clinically validated and approved. In this study, structure-activity relationships (SAR) within the 2-phenylamino-substituted benzothiopyrano[4,3-d]pyrimidine class of kinase inhibitors were further refined by the synthesis and biological evaluation of new compounds 1-21 featuring different substitution patterns on the pendant phenyl moiety, combined with H, OCH₃, or Cl at 8-position. Most compounds showed a promising human kinase insert domain receptor (KDR) inhibition profile, with IC₅₀ values in the submicromolar/low micromolar range, and promising antiproliferative activity on human umbilical vein endothelial cells (HUVECs) as well as on a panel of three human tumor cell lines. The angio-kinase selectivity profile was assessed for the most promising compound 16 against a set of six human kinases. Finally, computational studies allowed clarifying at molecular level the interaction pattern established by the compounds with KDR, highlighting key stable cation-π interactions, and thus providing the basis for further designing novel inhibitors.

Self-assembled 4-(1,2-diphenylbut-1-en-1-yl)aniline based nanoparticles: podophyllotoxin and aloin as building blocks

The ability of 4-(1,2-diphenylbut-1-en-1-yl)aniline as a self-assembly inducer is reported. The conjugation of this moiety with aloin or podophyllotoxin resulted in spherical nanoparticles that were characterized by Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) and NanoSight technology. A preliminary biological evaluation on two cancer cell lines is reported.

New insights into the mechanism of action of pyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-one derivatives endowed with anticancer potential

Due to the scarce biological profile, the pyrazolo[1,2-a]benzo[1,2,3,4]tetrazine-3-one scaffold (PBT) has been recently explored as promising core for potential anticancer candidates. Several suitably decorated derivatives (PBTs) exhibited antiproliferative activity in the low-micromolar range associated with apoptosis induction and cell cycle arrest on S phase. Herein, we selected the most active derivatives and submitted them to further biological explorations to deepen the mechanism of action. At first, a DNA targeting is approached by means of flow Linear Dichroism experiments so as to evaluate how small planar molecules might interact with DNA, including the interference with the catalytic cycle of topoisomerase II and the influence on the cleavable complex stabilization (poisoning effect). In support of the experimental data, in silico studies have been achieved to better understand the chemical space of the interactions. Interestingly some meaningful structural features, useful for further developments, were found. The 8,9-di-Cl substituted derivative revealed as the most effective in the intercalative process, as well as on the inhibition of catalytic activity of topoisomerase II. Predicted ADME studies confirm that PBTs are promising as potential drug candidates.

Correction: Self-assembled 4-(1,2-diphenylbut-1-en-1-yl)aniline based nanoparticles: podophyllotoxin and aloin as building blocks

Correction for ‘Self-assembled 4-(1,2-diphenylbut-1-en-1-yl)aniline based nanoparticles: podophyllotoxin and aloin as building blocks’ by Gaia Fumagalli, et al., Org. Biomol. Chem., 2017, DOI: 10.1039/c6ob02591a.

Spermine cycling in mitochondria is mediated by adenine nucleotide translocase activity: mechanism and pathophysiological implications

Spermine, besides to be transported in mitochondria by an energy dependent electrophoretic mechanism, can be also released by two different mechanisms. The first one is induced in deenergizing conditions by FCCP or antimycin A and it is mediated by an electroneutral exchange spermine protons. The second one takes place in energizing conditions during the activity of the adenine nucleotide translocase and is mediated by an electroneutral symport mechanism involving the efflux in co-transport of spermine and phosphate and the exchange of exogenous ADP with endogenous ATP. The triggering of this mechanism permits an alternating cycling of spermine across the mitochondrial membrane, that is spermine is transported or released by energized mitochondria in the absence or presence of ATP synthesis, respectively. The physiological implications of this cycling of spermine are related to the induction or prevention of mitochondrial permeability transition and, consequently, on apoptosis or its prevention.

New trans dichloro (triphenylphosphine)platinum(II) complexes containing N-(butyl),N-(arylmethyl)amino ligands: Synthesis, cytotoxicity and mechanism of action

Some new platinum(II) complexes have been prepared, of general formula trans-[PtCl2(PPh3){NH(Bu)CH2Ar}], where the dimension of the Ar residue in the secondary amines has been varied from small phenyl to large pyrenyl group. The obtained complexes, tested in vitro towards a panel of human tumor cell lines showed an interesting antiproliferative effect on both cisplatin-sensitive and -resistant cells. For the most cytotoxic derivative 2a the investigation on the mechanism of action highlighted the ability to induce apoptosis on resistant cells and interestingly, to inhibit the catalytic activity of topoisomerase II.

Photobiological properties of 3-psoralenacetic acids

Some 4,8-dimethyl-3-psoralenacetic acids were synthesized and studied. All the designed psoralenacetic acids bear alkyl or cycloalkyl substituents at the furan ring. These psoralenacetic acids were shown to be a novel class of psoralen derivatives characterized by an interesting photobiological profile. The carboxylic group at the 3 position, useful to confer hydrophilic properties, appears to be detrimental to the classical intercalation into DNA, likely because of repulsive interactions with the negative surface of the macromolecule. Nevertheless, the new derivatives possess a notable photoantiproliferative activity, due to a peculiar mechanism of action consisting of a decarboxylation step before exerting their photobiological activity. The most active compound 2 is able to induce a noteworthy photocytotoxic effect, with GI50 values being submicromolar on human tumor cell lines and no effect in the dark. The involvement of DNA photoaddition after UVA light-mediated decarboxylation and ROS formation is responsible for its biological activity, as demonstrated comparing the activity profile of the decarboxylated analogue. However, other biological targets seem to be involved in the photooxidative damage, such as proteins. Compound 2 could thus be considered as a prodrug, inactive without UVA light but activated upon specific irradiation, thus preventing unselective side effects and opening new perspectives on agents useful in photochemotherapy.

CCK8 peptide-labeled Pluronic® F127 micelles as a targeted vehicle of gold-based anticancer chemotherapeutics

A sparingly water-soluble gold(iii) complex was encapsulated in micelles functionalized with the CCK8-targeting moiety for the selective delivery of an anticancer drug.

Mitochondrial permeability transition as target of anticancer drugs

Mitochondria are the cell powerhouses but also contain the mechanisms leading to cell death. Many signals converge on mitochondria to cause the permeabilization of mitochondrial membranes by the mitochondrial permeability transition (MPT) induction and the opening of transition pores (PTPs). These events cause loss of ionic homeostasis, matrix swelling, outer membrane rupture leading to pro-apoptotic factors release, and impairment of bioenergetics functions. The molecular mechanism underlying MPT induction is not completely elucidated however, a growing body of evidence supports the concept that pharmacological induction of PTPs in mitochondria of neoplastic cells is an effective and promising strategy for therapeutic approaches against cancer. The first part of this article presented as a review also evidences the main constituents of PTP and several compounds targeting them for inducing the phenomenon. The second part of the article regards the recent experimental development in the field, in particular, the effects of peniocerol (PEN), a sterol isolated from the root of Myrtillocactus geometrizans, at cellular and mitochondrial level. PEN exhibits a cytotoxic activity on some human tumor cell lines, whose mechanism is attributable to the oxidation of critical thiols located on adenine nucleotide translocase, the protein mainly involved in PTP. This event in the presence of Ca(2+) induces the MPT with the release of the pro-apoptotic factors cytochrome c and apoptosis inducing factor. These observations evidence that PEN may trigger both the caspase-dependent and caspaseindependent apoptotic pathways. This characteristic renders PEN a very interesting compound that could be developed to obtain more effective antiproliferative agents targeting mitochondria for anticancer therapy.