Design, synthesis and biological profile of new inhibitors of multidrug resistance associated proteins carrying a polycyclic scaffold

Anticancer activity of Mannich bases: a review of recent literature

This report summarizes the latest published data on the antiproliferative action and cytotoxic activity of Mannich bases, a structurally heterogeneous category of chemical entities that includes compounds which are synthesized via the grafting of an aminomethyl function onto diverse substrates by means of the Mannich reaction. The present overview of the topic is an update to the information assembled in a previously published review that covered the literature up to 2014.

Microwave-Assisted Cu(I)-Catalyzed Synthesis of Unsymmetrical 1,4-Diamino-2-butynes via Cross-A3-Coupling/Decarboxylative A3-Coupling

1,4-Diamino-2-butynes display both chemical and physiological properties. Here a highly efficient synthesis avenue to generate unsymmetric 1,4-diamino-2-butynes has been developed by microwave-assisted Cu(I)-catalyzed cross-A³-coupling/decarboxylative coupling of two different amines, formaldehyde, and propiolic acid through a domino process. This multicomponent reaction provides a series of target products in moderate to good yields with high chemoselectivity.

One-pot three-component tandem annulation of 4-hydroxycoumarine with aldehyde and aromatic amines using graphene oxide as an efficient catalyst

A convenient and efficient solvent-free, facile, one-pot three-component graphene oxide catalysed approach has been described for the synthesis of chromeno-[4,3-b]quinolin-6-one derivatives from 4-hydroxycoumarin with aldehydes and aromatic amines. Graphene oxide (GO) has proved to be a new class of heterogeneous carbocatalyst which could be easily recovered and reused up to 5th run without significant loss of its catalytic activity. A broad scope of substrate applicability is offered and a plausible mechanism is also suggested for this developed protocol.

Multifaceted activity of polyciclic MDR revertant agents in drug-resistant leukemic cells: Role of the spacer

A small library of derivatives carrying a polycyclic scaffold recently identified by us as a new privileged structure in medicinal chemistry was designed and synthesized, aiming at obtaining potent MDR reverting agents also endowed with antitumor properties. In particular, as a follow-up of our previous studies, attention was focused on the role of the spacer connecting the polycyclic core with a properly selected nitrogen-containing group. A relevant increase in reverting potency was observed, going from the previously employed but-2-ynyl- to a pent-3-ynylamino moiety, as in compounds 3d and 3e, while the introduction of a triazole ring proved to differently impact on the activity of the compounds. The docking results supported the data obtained by biological tests, showing, for the most active compounds, the ability to establish specific bonds with P-glycoprotein. Moreover, a multifaceted anticancer profile and dual in vitro activity was observed for all compounds, showing both revertant and antitumor effects on leukemic cells. In this respect, 3c emerged as a "triple-target" agent, endowed with a relevant reverting potency, a considerable antiproliferative activity and a collateral sensitivity profile.

Chemical molecular-based approach to overcome multidrug resistance in cancer by targeting P-glycoprotein (P-gp)

Multidrug resistance (MDR) remains one of the major impediments for efficacious cancer chemotherapy. Increased efflux of multiple chemotherapeutic drugs by transmembrane ATP-binding cassette (ABC) transporter superfamily is considered one of the primary causes for cancer MDR, in which the role of P-glycoprotein (P-gp/ABCB1) has been most well-established. The clinical co-administration of P-gp drug efflux inhibitors, in combination with anticancer drugs which are P-gp transport substrates, was considered to be a treatment modality to surmount MDR in anticancer therapy by blocking P-gp-mediated multidrug efflux. Extensive attempts have been carried out to screen for sets of nontoxic, selective, and efficacious P-gp efflux inhibitors. In this review, we highlight the recent achievements in drug design, characterization, structure-activity relationship (SAR) studies, and mechanisms of action of the newly synthetic, potent small molecules P-gp inhibitors in the past 5 years. The development of P-gp inhibitors will increase our knowledge of the mechanisms and functions of P-gp-mediated drug efflux which will benefit drug discovery and clinical cancer therapeutics where P-gp transporter overexpression has been implicated in MDR.

Design, Synthesis and Biochemical Evaluation of Novel Ethanoanthracenes and Related Compounds to Target Burkitt's Lymphoma

Lymphomas (cancers of the lymphatic system) account for 12% of malignant diseases worldwide. Burkitt’s lymphoma (BL) is a rare form of non-Hodgkin’s lymphoma in which the cancer starts in the immune B-cells. We report the synthesis and preliminary studies on the antiproliferative activity of a library of 9,10-dihydro-9,10-ethanoanthracene based compounds structurally related to the antidepressant drug maprotiline against BL cell lines MUTU-1 and DG-75. Structural modifications were achieved by Diels-Alder reaction of the core 9-(2-nitrovinyl)anthracene with number of dienophiles including maleic anhydride, maleimides, acrylonitrile and benzyne. The antiproliferative activity of these compounds was evaluated in BL cell lines EBV⁻ MUTU-1 and EBV⁺ DG-75 (chemoresistant). The most potent compounds 13j, 15, 16a, 16b, 16c, 16d and 19a displayed IC₅₀ values in the range 0.17–0.38 μM against the BL cell line EBV⁻ MUTU-1 and IC₅₀ values in the range 0.45–0.78 μM against the chemoresistant BL cell line EBV⁺ DG-75. Compounds 15, 16b and 16c demonstrated potent ROS dependent apoptotic effects on the BL cell lines which were superior to the control drug taxol and showed minimal cytotoxicity to peripheral blood mononuclear cells (PBMCs). The results suggest that this class of compounds merits further investigation as antiproliferative agents for BL.

Targeting the Bacterial Membrane with a New Polycyclic Privileged Structure: A Powerful Tool To Face Staphylococcus aureus Infections

In this paper, a small series of anthracene-maleimide-based compounds was prepared and evaluated to assess the antimicrobial potential of this polycyclic core, a scaffold previously unexplored for new antibiotic development. Some of the new compounds showed appreciable anti-Staphylococcus aureus activity, together with good safety profiles. In particular, compound 13 proved to be the most promising of the series, showing remarkable antimicrobial activity toward planktonic and sessile bacterial cells within a mature preformed biofilm. The mechanism of action seems to be related to the ability of this compound to interfere with bacterial membrane functionality, probably through the targeting of key enzymes responsible for membrane redox homeostasis and energy production. The data reported confirm the ability of this polycyclic nucleus to behave as a new "privileged structure", suitable to be further exploited in the antimicrobial field.

Overexpression of the mitochondrial Mg channel MRS2 increases total cellular Mg concentration and influences sensitivity to apoptosis

The mechanism of action of the mitochondrial Mg channel MRS2 and its involvement in cell viability remain unclear. Deletion of MRS2 has been reported to abolish Mg influx into mitochondria, to induce functional defects in mitochondrial organelles, and to result in cell death. We evaluated whether MRS2 expression had an impact on total Mg cellular content by inducing the overexpression of MRS2 in HEK-293 cells. We observed a remarkable increase of total intracellular Mg concentration in cells overexpressing MRS2 compared with control cells. In order to investigate whether and in what manner the detected Mg increment was involved in the MRS2 influence on cell viability, we treated MRS2-overexpressing cells with two known apoptotic inducers. We found that cells overexpressing the MRS2 channel became less responsive to these pharmacological insults. Our experimental evidence indicates that the MRS2 channel controls overall intracellular Mg levels, the alteration of which might have a role in the molecular signaling leading to apoptotic cell death.

Polycyclic Maleimide-based Scaffold as New Privileged Structure for Navigating the Cannabinoid System Opportunities

The discovery of the relevant role played by a dysregulation of the endogenous cannabinoid system in several pathological conditions has prompted an extensive research in this field. In this Letter, a series of cannabinoid receptor ligands bearing a previously unexplored polycyclic scaffold was designed and synthesized, in order to evaluate the potential of a new easily affordable privileged structure. The new compounds showed an appreciable affinity and a significant selectivity for the CB2 receptor and are endowed with an intriguing noncompetitive antagonist behavior. Due to the ability of the polycyclic structure to be easily modified in different ways, these compounds could represent convenient chemical tools to be exploited in order to better understand the endocannabinoid system impact on physiopathological conditions.

GRP78-mediated antioxidant response and ABC transporter activity confers chemoresistance to pancreatic cancer cells

Chemoresistance is a major therapeutic challenge that plays a role in the poor statistical outcomes in pancreatic cancer. Unfolded protein response (UPR) is one of the homeostasis mechanisms in cancer cells that have been correlated with chemoresistance in a number of cancers including pancreatic cancer. In this study, we show that modulating glucose regulatory protein 78 (GRP78), the master regulator of the UPR, can have a profound effect on multiple pathways that mediate chemoresistance. Our study showed for the first time that silencing GRP78 can diminish efflux activity of ATP-binding cassette (ABC) transporters, and it can decrease the antioxidant response resulting in an accumulation of reactive oxygen species (ROS). We also show that these effects can be mediated by the activity of specificity protein 1 (SP1), a transcription factor overexpressed in pancreatic cancer. Thus, inhibition of SP1 negatively affects the UPR, deregulates the antioxidant response of NRF2, as well as ABC transporter activity by inhibiting GRP78-mediated ER homeostasis. Sp1 and NRF2 have been classified as nononcogene addiction genes and thus are imperative to understanding the molecular mechanism of resistance. These finding have huge clinical relevance as both Sp1 and GRP78 are overexpressed in pancreatic cancer patients and increased expression of these proteins is indicative of poor prognosis. Understanding how these proteins may regulate chemoresistance phenotype of this aggressive cancer may pave the way for development of efficacious therapy for this devastating disease.

Coumarin derivatives as potential antitumor agents: Growth inhibition, apoptosis induction and multidrug resistance reverting activity

A small library of coumarins, carrying butynyl-amino chains, was synthesized continuing our studies in the field of MDR reverting ageEnts and in order to obtain multipotent agents to combat malignancies. In particular, the reported anticancer and chemopreventive natural product 7-isopentenyloxycoumarin was linked to different terminal amines, selected on the basis of our previously reported results. The anticancer behaviour and the MDR reverting ability of the new compounds were evaluated on human colon cancer cells, particularly prone to develop the MDR phenotype. Some of the new derivatives showed promising effects, directly acting as cytotoxic compounds and/or counteracting MDR phenomenon. Compound 1e emerged as the most interesting of this series, showing a multipotent biological profile and suggesting that conjugation of an appropriate coumarin core with a properly selected butynyl-amino chain allows to obtain novel hybrid molecules endowed with improved in vitro antitumor activity.

Controlling chemoselectivity in copper-catalyzed decarboxylative A3/A3 cross-couplings: direct formation of unsymmetrical 1,4-diamino-2-butynes

A direct cross-coupling of propiolic acid with two kinds of in situ formed iminiums has been achieved via a CuI/CuCl₂-catalyzed decarboxylative A³/A³ domino process.

Extending the structure-activity relationship study of marine natural ningalin B analogues as P-glycoprotein inhibitors

In the present study, a total of 25 novel ningalin B analogues were synthesized and evaluated for their P-gp modulating activity in a P-gp overexpressed breast cancer cell line LCC6MDR. Preliminary structure-activity study shows that A ring and its two methoxy groups are important pharmacophores for P-gp inhibiting activity. Among all derivatives, 23 is the most potent P-gp modulator with EC₅₀ of 120-165 nM in reversing paclitaxel, DOX, vinblastine and vincristine resistance. It is relatively safe to use with selective index at least greater than 606 compared to verapamil. Mechanistic study demonstrates that compound 23 reverses P-gp mediated drug resistance by inhibiting transport activity of P-gp, thereby restoring intracellular drug accumulation. In summary, our study demonstrates that ningalin B analogue 23 is a non-cytotoxic and effective P-gp chemosensitizer that can be used in the future for reversing P-gp mediated clinical cancer drug resistance.

Mathematical analysis of multi-antibiotic resistance

BACKGROUND

Multi-antibiotic resistance in bacterial infections is a growing threat to public health. Some experiments were carried out to study the multi-antibiotic resistance.

METHODS

The changes of the multi-antibiotic resistance with time were achieved by numerical simulations and the mathematical models, with the calculated temperature field, velocity field, and the antibiotic concentration field.

RESULTS

The computed results and experimental results are compared.

CONCLUSIONS

Both numerical simulations and the analytic models suggest that minor low concentrations of antibiotics could induce antibiotic resistance in bacteria.