Marine Natural Products as Models to Circumvent Multidrug Resistance

Isolation and structure elucidation of the compounds from Teucrium hyrcanicum L. and the investigation of cytotoxicity, antioxidant activity, and protective effect on hydrogen peroxide-induced oxidative stress

BACKGROUND

Teucrium hyrcanicum L. (family Lamiaceae) is widely distributed in the North and Northwest of Iran. It has been used in the form of tea, tonic, and tincture for the treatment of various diseases such as cough, rheumatism, and fever.

METHODS

In this study, the total phenolic and flavonoid contents, antioxidant and cytotoxic activities of methanol extract and different fractions of T. hyrcanicum were measured. Furthermore, the potential ability of T. hyrcanicum to protect against H2O2-induced oxidative stress was tested on the NIH3T3 cell line. Then, the isolation and structure elucidation of the compounds were performed on the most potent fractions. Finally, the quantification of isolated compounds in methanol extract (ME) was done by the HPLC method. Isolated phytochemicals were assessed for the cytotoxic and antioxidant activities.

RESULTS

The results indicated that the methanol fraction (MF) had the highest amount of phenolic and flavonoid contents (69.36 mg GAE/g extract and 68.95 mg QE/g extract). The highest radical scavenging activities were observed from MF and ME (IC50 44.32 and 61.12 μg.ml-1, respectively). The best cytotoxicity was obtained by ethyl acetate fraction (EF) against A431 and MCF7 cell lines (IC50 values of 235.4and 326.6 μg.ml-1, respectively). The pretreatment with MF exerts the highest reduction in malondialdehyde (MDA) formation (IC50 2.51 μM, p < 0.001) compared to the H2O2 group (5.77 μM). Also, MF significantly inhibited H2O2-induced Glutathione (GSH) oxidation (p < 0.001). Furthermore, two phenolic compounds, acteoside and quercetin, were isolated and identified in MF and EF, respectively. The IC50 values of acteoside and quercetin in the DPPH assay were 7.19 and 5.56 µg.ml-1, respectively. Both quercetin and acteoside significantly reduced the MDA formation and inhibited GSH oxidation, which was comparable with BHA (as a standard antioxidant) (p < 0.05). Acteoside demonstrated significant cytotoxicity against all tested cell lines (IC50 = 32 to 145 μg.ml-1). The HPLC quantification of isolated compounds revealed that the quantity of acteoside and quercetin in ME were 93.31 and 16.87 μg.mg-1, respectively.

CONCLUSION

The isolated compounds (quercetin and acteoside) had significant antioxidant activities and revealed a protective effect on H2O2-induced oxidative stress which was comparable with BHA.

Bioactive Usual and Unusual Triterpenoids Derived from Natural Sources Used in Traditional Medicine

Triterpenoids are accessible in several terrestrial plants as well as marine organisms, including sponges, algae, fungi, and sea cucumbers are examples of marine creatures. So far, more than 20,000 natural triterpenoids have exhibited several varied bioactivities, including anticancer, antimalarial, anti-HIV, inhibit HIF-1 activation, antibacterial, chemopreventive, anti-inflammatory, antioxidant, cardioprotective, antiviral, neuroprotective, hepatoprotective, insecticidal, antidiabetic, cytotoxic. Several plants are used in folklore medicine to treat numerous ailments, and the preparation or uses of traditional practices have been scientifically validated. Although various structural diversity has been observed in the triterpenoids, this review presents the sources and uses of those triterpenoids that showed significant biological activities which could be accessible and promoted to familiar people in the form of traditional medicine or for industrial, or pharmaceutical applications.

Remodeling tumor microenvironment with natural products to overcome drug resistance

With cancer incidence rates continuing to increase and occurrence of resistance in drug treatment, there is a pressing demand to find safer and more effective anticancer strategy for cancer patients. Natural products, have the advantage of low toxicity and multiple action targets, are always used in the treatment of cancer prevention in early stage and cancer supplement in late stage. Tumor microenvironment is necessary for cancer cells to survive and progression, and immune activation is a vital means for the tumor microenvironment to eliminate cancer cells. A number of studies have found that various natural products could target and regulate immune cells such as T cells, macrophages, mast cells as well as inflammatory cytokines in the tumor microenvironment. Natural products tuning the tumor microenvironment via various mechanisms to activate the immune response have immeasurable potential for cancer immunotherapy. In this review, it highlights the research findings related to natural products regulating immune responses against cancer, especially reveals the possibility of utilizing natural products to remodel the tumor microenvironment to overcome drug resistance.

Bioprospecting the microbiome of Red Sea Atlantis II brine pool for peptidases and biosynthetic genes with promising antibacterial activity

Background

The search for novel antimicrobial agents is crucial as antibiotic-resistant pathogens continue to emerge, rendering the available antibiotics no longer effective. Likewise, new anti-cancer drugs are needed to combat the emergence of multi-drug resistant tumors. Marine environments are wealthy sources for natural products. Additionally, extreme marine environments are interesting niches to search for bioactive natural compounds. In the current study, a fosmid library of metagenomic DNA isolated from Atlantis II Deep Lower Convective Layer (ATII LCL), was functionally screened for antibacterial activity as well as anticancer effects.

Results

Two clones exhibited antibacterial effects against the marine Bacillus Cc6 strain, namely clones 102-5A and 88-1G and they were further tested against eleven other challenging strains, including six safe relatives of ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter  spp.), a safe relative to Mycobacterium tuberculosis and four resistant clinical isolates. Clone 88-1G resulted in clear zones of inhibition against eight bacterial strains, while clone 102-5A resulted in zones of inhibition against five bacterial strains. The whole cell lysates of clone 88-1G showed 15% inhibition of Mtb ClpP protease -Mycobacterium tuberculosis drug target-, while whole cell lysates of clone 102-5A showed 19% inhibition of Mtb ClpP protease. Whole cell lysates from the selected clones exhibited anticancer effects against MCF-7 breast cancer cells (cell viability at 50% v/v was 46.2% ± 9.9 for 88-1G clone and 38% ± 7 for 102-5A clone), U2OS osteosarcoma cells (cell viability at 50% v/v was 64.6% ± 12.3 for 88-1G clone and 28.3% ± 1.7 for 102-5A clone) and 1BR hTERT human fibroblast cells (cell viability at 50% v/v was 74.4% ± 5.6 for 88-1G clone and 57.6% ± 8.9 for 102-5A clone). Sequencing of 102-5A and 88-1G clones, and further annotation detected putative proteases and putative biosynthetic genes in clones 102-5A and 88-1G, respectively.

Conclusions

The ATII LCL metagenome hosts putative peptidases and biosynthetic genes that confer antibiotic and anti-cancer effects. The tested clones exhibited promising antibacterial activities against safe relative strains to ESKAPE pathogens and Mycobacterium tuberculosis. Thus, searching the microbial dark matter of extreme environments is a promising approach to identify new molecules with pharmaceutical potential use.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01835-z.

Cancer Cell Inhibiting Sea Cucumber (Holothuria leucospilota) Protein as a Novel Anti-Cancer Drug

Cancer remains the primary cause of death worldwide. To develop less toxic anti-cancer drugs to relieve the suffering and improve the survival of cancer patients is the major focus in the anti-cancer field. To this end, marine creatures are being extensively studied for their anti-cancer effects, since extracts from at least 10% of the marine organisms have been shown to possess anti-tumor activities. As a classic Chinese traditional medicine, sea cucumbers and compounds extracted from the sea cucumbers, such as polysaccharides and saponins, have recently been shown to exhibit anti-cancer, anti-inflammatory, and anti-oxidant effects. Holothuria leucospilota (H. leucospilota) is a tropical edible sea cucumber species that has been successfully cultivated and farmed in large scales, providing a readily available source of raw materials to support the development of novel marine anti-cancer drugs. However, very few studies have so far been performed on the biological activities of H. leucospilota. In this study, we first investigated the anti-cancer effect of H. leucospilota protein on three cancer cell lines (i.e., HepG2, A549, Panc02) and three normal cell lines (NIH-3T3, HaCaT, 16HBE). Our data showed that H. leucospilota protein decreased the cell viabilities of HepG2, A549, HaCaT, 16HBE in a concentration-dependent manner, while Panc02 and NIH-3T3 in a time- and concentration-dependent manner. We also found that the inhibitory effect of H. leucospilota protein (≥10 μg/mL) on cell viability is near or even superior to EPI, a clinical chemotherapeutic agent. In addition, our data also demonstrated that H. leucospilota protein significantly affected the cell cycle and induced apoptosis in the three cancer cell lines investigated; in comparison, it showed no effects on the normal cell lines (i.e., NIH-3T3, HaCaT and 16HBE). Finally, our results also showed that H. leucospilota protein exhibited the excellent performance in inhibiting cell immigrations. In conclusion, H. leucospilota protein targeted the cancer cell cycles and induced cancer cell apoptosis; its superiority to inhibit cancer cell migration compared with EPI, shows the potential as a promising anti-cancer drug.

Molecular evidences on anti-inflammatory, anticancer, and memory-boosting effects of frankincense

Chemical diversity of natural products with drug-like features has attracted much attention from medicine to develop more safe and effective drugs. Their anti-inflammatory, antitumor, analgesic, and other therapeutic properties are sometimes more successful than chemical drugs in controlling disease due to fewer drug resistance and side effects and being more tolerable in a long time. Frankincense, the oleo gum resin extracted from the Boswellia species, contains some of these chemicals. The anti-inflammatory effect of its main ingredient, boswellic acid, has been traditionally used to treat many diseases, mainly those target memory functions. In this review, we have accumulated research evidence from the beneficial effect of Frankincense consumption in memory improvement and the prevention of inflammation and cancer. Besides, we have discussed the molecular pathways mediating the therapeutic effects of this natural supplement.

Metabolites from Marine-Derived Fungi as Potential Antimicrobial Adjuvants

Marine-derived fungi constitute an interesting source of bioactive compounds, several of which exhibit antibacterial activity. These acquire special importance, considering that antimicrobial resistance is becoming more widespread. The overexpression of efflux pumps, capable of expelling antimicrobials out of bacterial cells, is one of the most worrisome mechanisms. There has been an ongoing effort to find not only new antimicrobials, but also compounds that can block resistance mechanisms which can be used in combination with approved antimicrobial drugs. In this work, a library of nineteen marine natural products, isolated from marine-derived fungi of the genera Neosartorya and Aspergillus, was evaluated for their potential as bacterial efflux pump inhibitors as well as the antimicrobial-related mechanisms, such as inhibition of biofilm formation and quorum-sensing. Docking studies were performed to predict their efflux pump action. These compounds were also tested for their cytotoxicity in mouse fibroblast cell line NIH/3T3. The results obtained suggest that the marine-derived fungal metabolites are a promising source of compounds with potential to revert antimicrobial resistance and serve as an inspiration for the synthesis of new antimicrobial drugs.

Diketopiperazine Gels: New Horizons from the Self-Assembly of Cyclic Dipeptides

Cyclodipeptides (CDPs) or 2,5-diketopiperazines (DKPs) can exert a variety of biological activities and display pronounced resistance against enzymatic hydrolysis as well as a propensity towards self-assembly into gels, relative to the linear-dipeptide counterparts. They have attracted great interest in a variety of fields spanning from functional materials to drug discovery. This concise review will analyze the latest advancements in their synthesis, self-assembly into gels, and their more innovative applications.

Design, synthesis and bioactivity study on 5-phenylfuran derivatives as potent reversal agents against P-glycoprotein-mediated multidrug resistance in MCF-7/ADR cell

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) is a phenomenon in which cells become resistant to structurally and mechanistically unrelated drugs resulting in low intracellular drug concentrations. It is one of the noteworthy problems in malignant tumor clinical therapeutics. So P-gp protein is one of the ideal targets to solve MDR. Based on the lead compound 5m obtained from our previous work, a series of furan derivatives featuring alkyl-substituted phenols and 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline were designed and synthesized as reversal agents against P-gp in this paper. Compound 16 containing isopropoxy possessed good potency against P-gp mediated MDR in MCF-7/ADR (IC₅₀ (doxorubicin) = 0.73 μM, RF = 69.6 with 5 μM 16 treated). Western blot results and Rh123 accumulation assays showed that 16 effectively inhibited P-gp efflux function but not its expression. The preliminary structure-activity relationship and docking studies demonstrated that compound 16 would be a potential P-gp inhibitor. Most worthy of mention is that compound 16 has achieved satisfactory results in combination with a variety of anti-tumor drugs, such as doxorubicin, paclitaxel, and vincristine. This study forwards a hopeful P-gp inhibitor for withstanding malignant tumor cell with multidrug resistance setting the basis for further studies.

Dynamic disequilibrium of macromolecular transport as possible mechanism for hydrocephalus associated with long-term spaceflight

Hydrocephalus associated with long term spaceflight (HALS) for missions lasting over five months is well described but poorly understood. While structural changes of the brain due to microgravitational forces affecting the circulation of cerebrospinal fluid (CSF) have been described as one potential cause, we propose an alternative hypothesis based on dynamic disequilibrium of macromolecular transport across the blood brain barrier. We propose that factors altering physiology under conditions of spaceflight such as microgravity, hypercapnia, venous hypertension, medications, and dietary substances contribute to increased protein load in the ventricles and/or contribute to impairment of transport out of the ventricles that results in HALS. Individual variation in the genetic expression of efflux transporters (p-glycoprotein) has been shown to correlate with the presence and degree of hydrocephalus in animal studies. We describe the evidence behind this concept and propose how these factors can be studied in order to determine the underlying pathogenesis which is imperative in order to cure or prevent HALS.

The Phylum Bryozoa: From Biology to Biomedical Potential

Less than one percent of marine natural products characterized since 1963 have been obtained from the phylum Bryozoa which, therefore, still represents a huge reservoir for the discovery of bioactive metabolites with its ~6000 described species. The current review is designed to highlight how bryozoans use sophisticated chemical defenses against their numerous predators and competitors, and which can be harbored for medicinal uses. This review collates all currently available chemoecological data about bryozoans and lists potential applications/benefits for human health. The core of the current review relates to the potential of bryozoan metabolites in human diseases with particular attention to viral, brain, and parasitic diseases. It additionally weighs the pros and cons of total syntheses of some bryozoan metabolites versus the synthesis of non-natural analogues, and explores the hopes put into the development of biotechnological approaches to provide sustainable amounts of bryozoan metabolites without harming the natural environment.

Phytosterols in Cancer: From Molecular Mechanisms to Preventive and Therapeutic Potentials

Cancer is the second leading cause of death worldwide. Compelling evidence supports the hypothesis that the manipulation of dietary components, including plant compounds termed as phytochemicals, demonstrates certain important health benefits in humans, including those in cancer. In fact, beyond their well-known cardiovascular applications, phytosterols may also possess anticancer properties, as has been demonstrated by several studies. Although the mechanism of action by which phytosterols (and derivatives) may prevent cancer development is still under investigation, data from multiple experimental studies support the hypothesis that they may modulate proliferation and apoptosis of tumor cells. Phytosterols are generally considered safe for human consumption and may also be added to a broad spectrum of food matrices; further, they could be used in primary and secondary prevention. However, few interventional studies have evaluated the relationship between the efficacy of different types and forms of phytosterols in cancer prevention. In this context, the purpose of this review was to revisit and update the current knowledge on the molecular mechanisms involved in the anticancer action of phytosterols and their potential in cancer prevention or treatment.

Medicinal chemistry strategies to discover P-glycoprotein inhibitors: An update

The presence of multidrug resistance (MDR) in malignant tumors is one of the primary causes of treatment failure in cancer chemotherapy. The overexpression of the ATP binding cassette (ABC) transporter, P-glycoprotein (P-gp), which significantly increases the efflux of certain anticancer drugs from tumor cells, produces MDR. Therefore, inhibition of P-gp may represent a viable therapeutic strategy to overcome cancer MDR. Over the past 4 decades, many compounds with P-gp inhibitory efficacy (referred to as first- and second-generation P-gp inhibitors) have been identified or synthesized. However, these compounds were not successful in clinical trials due to a lack of efficacy and/or untoward toxicity. Subsequently, third- and fourth-generation P-gp inhibitors were developed but dedicated clinical trials did not indicate a significant therapeutic effect. In recent years, an extraordinary array of highly potent, selective, and low-toxicity P-gp inhibitors have been reported. Herein, we provide a comprehensive review of the synthetic and natural products that have specific inhibitory activity on P-gp drug efflux as well as promising chemosensitizing efficacy in MDR cancer cells. The present review focuses primarily on the structural features, design strategies, and structure-activity relationships (SAR) of these compounds.

Bioinformatics for Marine Products: An Overview of Resources, Bottlenecks, and Perspectives

The sea represents a major source of biodiversity. It exhibits many different ecosystems in a huge variety of environmental conditions where marine organisms have evolved with extensive diversification of structures and functions, making the marine environment a treasure trove of molecules with potential for biotechnological applications and innovation in many different areas. Rapid progress of the omics sciences has revealed novel opportunities to advance the knowledge of biological systems, paving the way for an unprecedented revolution in the field and expanding marine research from model organisms to an increasing number of marine species. Multi-level approaches based on molecular investigations at genomic, metagenomic, transcriptomic, metatranscriptomic, proteomic, and metabolomic levels are essential to discover marine resources and further explore key molecular processes involved in their production and action. As a consequence, omics approaches, accompanied by the associated bioinformatic resources and computational tools for molecular analyses and modeling, are boosting the rapid advancement of biotechnologies. In this review, we provide an overview of the most relevant bioinformatic resources and major approaches, highlighting perspectives and bottlenecks for an appropriate exploitation of these opportunities for biotechnology applications from marine resources.

ABC Transporter-Mediated Multidrug-Resistant Cancer

ATP-binding cassette (ABC) transporters are involved in active pumping of many diverse substrates through the cellular membrane. The transport mediated by these proteins modulates the pharmacokinetics of many drugs and xenobiotics. These transporters are involved in the pathogenesis of several human diseases. The overexpression of certain transporters by cancer cells has been identified as a key factor in the development of resistance to chemotherapeutic agents. In this chapter, the localization of ABC transporters in the human body, their physiological roles, and their roles in the development of multidrug resistance (MDR) are reviewed. Specifically, P-glycoprotein (P-GP), multidrug resistance-associated proteins (MRPs), and breast cancer resistance protein (BCRP/ABCG2) are described in more detail. The potential of ABC transporters as therapeutic targets to overcome MDR and strategies for this purpose are discussed as well as various explanations for the lack of efficacy of ABC drug transporter inhibitors to increase the efficiency of chemotherapy.

Frankincense essential oil suppresses melanoma cancer through down regulation of Bcl-2/Bax cascade signaling and ameliorates heptotoxicity via phase I and II drug metabolizing enzymes

Melanoma is a deadly form of malignancy and according to the World Health Organization 132,000 new cases of melanoma are diagnosed worldwide each year. Surgical resection and chemo/drug treatments opted for early and late stage of melanoma respectively, however detrimental post surgical and chemotherapy consequences are inevitable. Noticeably melanoma drug treatments are associated with liver injuries such as hepatitis and cholestasis which are very common. Alleviation of these clinical manifestations with better treatment options would enhance prognosis status and patients survival. Natural products which induce cytotoxicity with minimum side effects are of interest to achieve high therapeutic efficiency. In this study we investigated anti-melanoma and hepatoprotective activities of frankincense essential oil (FEO) in both in vitro and in vivo models. Pretreatment with FEO induce a significant (p < 0.05) dose-dependent reduction in the cell viability of mouse (B16-F10) and human melanoma (FM94) but not in the normal human epithelial melanocytes (HNEM). Immunoblot analysis showed that FEO induces down regulation of Bcl-2 and up regulation of BAX in B16-F10 cells whereas in FM94 cells FEO induced dose-dependent cleavage of caspase 3, caspase 9 and PARP. Furthermore, FEO (10 μg/ml) treatment down regulated MCL1 in a time-dependent manner in FM94 cells. In vivo toxicity analysis reveals that weekly single dose of FEO (1200 mg/kg body weight) did not elicit detrimental effect on body weight during four weeks of experimental period. Histology of tissue sections also indicated that there were no observable histopathologic differences in the brain, heart, liver, and kidney compare to control groups. FEO (300 and 600 mg/kg body weight) treatments significantly reduced the tumor burden in C57BL/6 mice melanoma model. Acetaminophen (750 mg/kg body weight) was used to induce hepatic injury in Swiss albino mice. Pre treatment with FEO (250 and 500 mg/kg body weight) for seven days retained hematology (complete blood count), biochemical parameters (AST, ALT, ALK, total bilirubin, total protein, glucose, albumin/globulin ratio, cholesterol and triglyceride), and the level of phase I and II drug metabolizing enzymes (cytochrome P450, cytochromeb5, glutathione-S-transferase) which were obstructed by the administration of acetaminophen. Further liver histology showed that FEO treatments reversed the damages (central vein dilation, hemorrhage, and nuclei condensation) caused by acetaminophen. In conclusion, FEO elicited marked anti-melanoma in both in vitro and in vivo with a significant heptoprotection.

An LC-MS/MS Method for Synchronous Determination of Paclitaxel and Curcumin: Development, Validation, and Application to a Pharmacokinetic Study

Background:

A chromatography tandem mass spectrometry method was first established and validated for the synchronous determination of curcumin(CUR) and paclitaxel (PTX) in this study. </P><P> Objective: An LC-MS/MS Method for Determination of Paclitaxel and Curcumin.

Methods:

The analytes were extracted with methanol, and docetaxel was used as the internal standard (IS). The analytes and the IS were separated on a C18 (4.6 mm × 50 mm, 3.5 µm) column with a mobile phase of 0.1% formic acid solution and methanol (80:20, v/v). The flow velocity of the mobile phase was 0.5 mL/min. And then, the method was applied to study the pharmacokinetic behavior of CUR and PTX in rats.

Results:

The calibration curves were linear within the concentration ranges of 2–1000 ng/mL for PTX and 5–500 ng/mL for CUR, the mean extraction recoveries and matrix effects of PTX, CUR, and the IS were within an acceptable range. The apparent volume of distribution of PTX was different between the group of administration of PTX and the group of co-administration with CUR and PTX.

Conclusion:

A sensitive and simple liquid chromatography-tandem mass spectrometry method was established and validated for the synchronous determination of PTX and CUR in rat plasma, CUR increased the apparent volume of distribution of PTX when CUR and PTX were co-administered.

Antibacterial and anticancer activities of orphan biosynthetic gene clusters from Atlantis II Red Sea brine pool

BACKGROUND

Cancer and infectious diseases are problematic because of continuous emergence of drug resistance. One way to address this enormous global health threat is bioprospecting the unlikeliest environments, such as extreme marine niches, which have tremendous biodiversity that is barely explored. One such environment is the Red Sea brine pool, Atlantis II Deep (ATII). Here, we functionally screened a fosmid library of metagenomic DNA isolated from the ATII lower convective layer (LCL) for antibacterial and anticancer activities.

RESULTS

Selected clones, 14-7E and 10-2G, displayed antibacterial effects on the marine strain Bacillus sp. Cc6. Moreover, whole cell lysates from 14-7E and 10-2G exhibited decreased cell viability against MCF-7 (39.1% ± 6.6, 42% ± 8.1 at 50% v/v) and U2OS cells (35.7% ± 1.9, 79.9% ± 5.9 at 50% v/v), respectively. By sequencing the insert DNA from 14-7E and 10-2G, we identified two putative orphan biosynthetic gene clusters. Both clusters harbored putative ATP-binding cassette (ABC) transporter permeases and S-adenosylmethionine-related genes. Interestingly, the biosynthetic gene cluster identified on 14-7E is of archaeal origin and harbors a putative transcription factor. Several identified genes may be responsible for the observed antibacterial and anticancer activities. The 14-7E biosynthetic gene cluster may be encoding enzymes producing a specialized metabolite (effect of detected genes involved in C-C bond formation and glycosylation). The bioactivity may also be due to predicted subtilases encoded by this cluster. The 10-2G cluster harbored putative glycosyltransferase and non-ribosomal peptide synthase genes; thus the observed activity of this clone could be caused by a bioactive peptide.

CONCLUSIONS

The ATII LCL prokaryotic metagenome hosts putative orphan biosynthetic gene clusters that confer antibiotic and anticancer effects. Further biochemical studies should characterize the detected bioactive components, and the potential use of 14-7E metabolite for antibiosis and 10-2G metabolite as a selective anti-breast cancer drug.

The Effects of Synthetically Modified Natural Compounds on ABC Transporters

Multidrug resistance (MDR) is a major hurdle which must be overcome to effectively treat cancer. ATP-binding cassette transporters (ABC transporters) play pivotal roles in drug absorption and disposition, and overexpression of ABC transporters has been shown to attenuate cellular/tissue drug accumulation and thus increase MDR across a variety of cancers. Overcoming MDR is one desired approach to improving the survival rate of patients. To date, a number of modulators have been identified which block the function and/or decrease the expression of ABC transporters, thereby restoring the efficacy of a range of anticancer drugs. However, clinical MDR reversal agents have thus far proven ineffective and/or toxic. The need for new, effective, well-tolerated and nontoxic compounds has led to the development of natural compounds and their derivatives to ameliorate MDR. This review evaluates whether synthetically modifying natural compounds is a viable strategy to generate potent, nontoxic, ABC transporter inhibitors which may potentially reverse MDR.

Ascidian Toxins with Potential for Drug Development

Ascidians (tunicates) are invertebrate chordates, and prolific producers of a wide variety of biologically active secondary metabolites from cyclic peptides to aromatic alkaloids. Several of these compounds have properties which make them candidates for potential new drugs to treat diseases such as cancer. Many of these natural products are not produced by the ascidians themselves, rather by their associated symbionts. This review will focus mainly on the mechanism of action of important classes of cytotoxic molecules isolated from ascidians. These toxins affect DNA transcription, protein translation, drug efflux pumps, signaling pathways and the cytoskeleton. Two ascidian compounds have already found applications in the treatment of cancer and others are being investigated for their potential in cancer, neurodegenerative and other diseases.

Selective cytotoxicity of the herbal substance acteoside against tumor cells and its mechanistic insights

Natural products are characterized by extreme structural diversity and thus they offer a unique source for the identification of novel anti-tumor agents. Herein, we report that the herbal substance acteoside being isolated by advanced phytochemical methods from Lippia citriodora leaves showed enhanced cytotoxicity against metastatic tumor cells; acted in synergy with various cytotoxic agents and it sensitized chemoresistant cancer cells. Acteoside was not toxic in physiological cellular contexts, while it increased oxidative load, affected the activity of proteostatic modules and suppressed matrix metalloproteinases in tumor cell lines. Intraperitoneal or oral (via drinking water) administration of acteoside in a melanoma mouse model upregulated antioxidant responses in the tumors; yet, only intraperitoneal delivery suppressed tumor growth and induced anti-tumor-reactive immune responses. Mass-spectrometry identification/quantitation analyses revealed that intraperitoneal delivery of acteoside resulted in significantly higher, vs. oral administration, concentration of the compound in the plasma and tumors of treated mice, suggesting that its in vivo anti-tumor effect depends on the route of administration and the achieved concentration in the tumor. Finally, molecular modeling studies and enzymatic activity assays showed that acteoside inhibits protein kinase C. Conclusively, acteoside holds promise as a chemical scaffold for the development of novel anti-tumor agents.

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Acteoside was not toxic in physiological cellular or tissue contexts.

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This natural compound modulated antioxidant responses and proteostatic modules.

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Acteoside showed in vitro and in vivo selective cytotoxicity against tumor cells.

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IP administration of acteoside in a mouse tumor model activated immune responses.

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Acteoside inhibited Protein Kinase C.

Expression of genes and proteins of multidrug resistance in gastric cancer cells treated with resveratrol

Multidrug resistance (MDR) is a notable problem in the use of chemotherapy. Therefore, studies aimed at identifying substances capable of overcoming resistance of cancer cells are required. Examples of these compounds are polyphenols, including resveratrol, that exert a range of various biological activities. The aim of the present study was to demonstrate the effect of 3,5,4'-trihydroxy-trans-stilbene (resveratrol) on the expression of ATP binding cassette subfamily B member 1, Annexin A1 (ANXA1) and thioredoxin (TXN) genes, and the proteins encoded by these genes, which are associated with MDR. The experiments were performed in human gastric cancer cell lines EPG85-257RDB (RDB) and EPG85-257RNOV (RNOV), which are resistant to daunorubicin and mitoxantrone, respectively, in addition to EPG85-257P (control), which is sensitive to cytostatic drugs. Cells were treated with 30 or 50 µM resveratrol for 72 h and changes in the expression levels of the genes were analysed with the use of a reverse transcription-quantitative polymerase chain reaction. The cellular levels of P-glycoprotein (P-gp), ANXA1 and TXN were evaluated using immunofluorescence and western blot analysis. Resveratrol in both concentrations has been shown to have a statistically significant influence on expression of the mentioned genes, compared with untreated cells. In RDB cells, resveratrol reduced the expression level of all analyzed genes, compared with untreated cells. Similar results at the protein level were obtained for P-gp and TXN. In turn, in the RNOV cell line, resveratrol reduced TXN expression at mRNA and protein levels, compared with untreated cells. The results of the present study indicate that resveratrol may reduce the resistance of cancer cells by affecting the expression of a number of the genes and proteins associated with MDR.

A vascular disrupting agent overcomes tumor multidrug resistance by skewing macrophage polarity toward the M1 phenotype

Multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transporters is the major obstacle for chemotherapeutic success. Although attempts have been made to circumvent ABC transporter-mediated MDR in past decades, there is still no effective agent in clinic. Here, we identified a vascular disrupting agent, Z-GP-DAVLBH, that significantly inhibited the growth of multidrug-resistant human hepatoma HepG2/ADM and human breast cancer MCF-7/ADR tumor xenografts, although these cells were insensitive to Z-GP-DAVLBH in vitro. Z-GP-DAVLBH increased the secretion of granulocyte-macrophage colony-stimulating factor in tumor tissues and serum of tumor-bearing mice to skew tumor-associated macrophages from the pro-tumor M2 phenotype to the antitumor M1 phenotype, thereby contributing to the induction of HepG2/ADM and MCF-7/ADR cell apoptosis. Our findings shed new light on the underlying mechanisms of VDAs in the treatment of drug-resistant tumors and provide strong evidence that Z-GP-DAVLBH should be a promising agent for overcoming MDR.

Role of ATP-binding cassette transporters, apoptosis, and long non-coding RNAs in gastric cancer multidrug resistance

Cancer multidrug resistance refers to the cross resistance of cancer cells to a variety of anticancer drugs, which can be primary or secondary. Several mechanisms attribute to cancer multidrug resistance. In this paper, the recent progress in the understanding of the mechanisms of multi-drug resistance of gastric cancer cells with regard to the role of adenosine triphosphate binding cassette transporters, apoptosis, and long non-coding RNAs is reviewed.

Blood-Brain Barrier Driven Pharmacoresistance in Amyotrophic Lateral Sclerosis and Challenges for Effective Drug Therapies

The blood-brain barrier (BBB) is essential for proper neuronal function, homeostasis, and protection of the central nervous system (CNS) microenvironment from blood-borne pathogens and neurotoxins. The BBB is also an impediment for CNS penetration of drugs. In some neurologic conditions, such as epilepsy and brain tumors, overexpression of P-glycoprotein, an efflux transporter whose physiological function is to expel catabolites and xenobiotics from the CNS into the blood stream, has been reported. Recent studies reported that overexpression of P-glycoprotein and increase in its activity at the BBB drives a progressive resistance to CNS penetration and persistence of riluzole, the only drug approved thus far for treatment of amyotrophic lateral sclerosis (ALS), rapidly progressive and mostly fatal neurologic disease. This review will discuss the impact of transporter-mediated pharmacoresistance for ALS drug therapy and the potential therapeutic strategies to improve the outcome of ALS clinical trials and efficacy of current and future drug treatments.

Metabolic Disorder in Chronic Obstructive Pulmonary Disease (COPD) Patients: Towards a Personalized Approach Using Marine Drug Derivatives

Metabolic disorder has been frequently observed in chronic obstructive pulmonary disease (COPD) patients. However, the exact correlation between obesity, which is a complex metabolic disorder, and COPD remains controversial. The current study summarizes a variety of drugs from marine sources that have anti-obesity effects and proposed potential mechanisms by which lung function can be modulated with the anti-obesity activity. Considering the similar mechanism, such as inflammation, shared between obesity and COPD, the study suggests that marine derivatives that act on the adipose tissues to reduce inflammation may provide beneficial therapeutic effects in COPD subjects with high body mass index (BMI).

The Role of Eukaryotic and Prokaryotic ABC Transporter Family in Failure of Chemotherapy

Over the years chemotherapy failure has been a vital research topic as researchers have been striving to discover reasons behind it. The extensive studies carried out on chemotherapeutic agents confirm that resistance to chemotherapy is a major reason for treatment failure. “Resistance to chemotherapy,” however, is a comprehensive phrase that refers to a variety of different mechanisms in which ATP-binding cassette (ABC) mediated efflux dominates. The ABC is one of the largest gene superfamily of transporters among both eukaryotes and prokaryotes; it represents a variety of genes that code for proteins, which perform countless functions, including drug efflux – a natural process that protects cells from foreign chemicals. Up to date, chemotherapy failure due to ABC drug efflux is an active research topic that continuously provides further evidence on multiple drug resistance (MDR), aiding scientists in tackling and overcoming this issue. This review focuses on drug resistance by ABC efflux transporters in human, viral, parasitic, fungal and bacterial cells and highlights the importance of the MDR permeability glycoprotein being the mutual ABC transporter among all studied organisms. Current developments and future directions to overcome this problem are also discussed.