Tryptanthrin inhibits MDR1 and reverses doxorubicin resistance in breast cancer cells

Tryptanthrins as multi-bioactive agents: discovery, diversity distribution and synthesis

Tryptanthrin and its derivatives, representing a type of alkaloids with indoloquinazoline structures, were first obtained from blue plants and indigo, and then extracted from fungi, marine bacteria and a number of many other natural sources. Various strategies for their chemical synthesis have been reported while tryptanthrin biosynthesis has been less investigated. Tryptanthrin and its derivative products have a broad range of pharmacological and biological functions. In this review, we cover the sources, chemical synthesis and biosynthesis, modes of action and biological activities of tryptanthrin and its derivatives.

Therapeutic Potential of Natural Compounds to Modulate WNT/β-Catenin Signaling in Cancer: Current State of Art and Challenges

Targeted therapies and immunotherapies have improved the clinical outcome of cancer patients; however, the efficacy of treatment remains frequently limited due to low predictability of response and development of drug resistance. Therefore, novel therapeutic strategies for various cancer types are needed. Current research emphasizes the potential therapeutic value of targeting WNT/β-catenin dependent signaling that is deregulated in various cancer types. Targeting the WNT/β-catenin signaling pathway with diverse synthetic and natural agents is the subject of a number of preclinical studies and clinical trials for cancer patients. The usage of nature-derived agents is attributed to their health benefits, reduced toxicity and side effects compared to synthetic agents. The review summarizes preclinical studies and ongoing clinical trials that aim to target components of the WNT/β-catenin pathway across a diverse spectrum of cancer types, highlighting their potential to improve cancer treatment.

Tryptanthrin Down-Regulates Oncostatin M by Targeting GM-CSF-Mediated PI3K-AKT-NF-κB Axis

BACKGROUND

Oncostatin M (OSM) is involved in several inflammatory responses. Tryptanthrin (TRYP), as a natural alkaloid, is a bioactive compound derived from indigo plants. Objectives/ Methods: The purpose of this study is to investigate the potential inhibitory activity of TRYP on OSM release from neutrophils using neutrophils-like differentiated (d)HL-60 cells and neutrophils from mouse bone marrow.

RESULTS

The results showed that TRYP reduced the production and mRNA expression levels of OSM in the granulocyte-macrophage colony-stimulating factor (GM-CSF)-stimulated neutrophils-like dHL-60 cells. In addition, TRYP decreased the OSM production levels in the GM-CSF-stimulated neutrophils from mouse bone marrow. TRYP inhibited the phosphorylation of phosphatidylinositol 3-kinase (PI3K), AKT, and nuclear factor (NF)-κB in the GM-CSF-stimulated neutrophils-like dHL-60 cells.

CONCLUSIONS

Therefore, these results reveal for the first time that TRYP inhibits OSM release via the down-regulation of PI3K-AKT-NF-κB axis from neutrophils, presenting its potential as a therapeutic agent for inflammatory responses.

Discovery of the tryptanthrin-derived indoloquinazoline as an anti-breast cancer agent via ERK/JNK activation

Tryptanthrin, an alkaloid applied in traditional Chinese medicine, exhibits a variety of pharmacological activities. This study aimed to investigate the anti-tumor activity of the tryptanthrin derivative (8-cyanoindolo[2,1-b]quinazoline-6,12-dione [CIQ]) in breast cancer cells. In both MDA-MB-231 and MCF-7 breast cancer cells, CIQ inhibited cell viability and promoted caspase-dependent apoptosis. At the concentration- and time-dependent ways, CIQ increased the levels of p-ERK, p-JNK, and p-p38 in breast cancer cells. We found that exposure to the JNK inhibitor or the ERK inhibitor partially reversed CIQ's viability. We also observed that CIQ increased reactive oxygen species (ROS) generation, and upregulated the phosphorylation and expression of H2AX. However, the pretreatment of the antioxidants did not protect the cells against CIQ's effects on cell viability and apoptosis, which suggested that ROS does not play a major role in the mechanism of action of CIQ. In addition, CIQ inhibited the invasion of MDA-MB-231 cells and decreased the expression of the prometastatic factors (MMP-2 and Snail). These findings demonstrated that the possibility of this compound to show promise in playing an important role against breast cancer.

Recent advances of tryptanthrin and its derivatives as potential anticancer agents

Tryptanthrin is one of the well-known natural alkaloids with a broad spectrum of biological activities and can act as anti-inflammatory, anticancer, antibacterial, antifungal, antiviral, antitubercular, and other agents. Owing to its potent anticancer activity, tryptanthrin has been widely explored for the therapy of various cancers besides being effective against other diseases. Tryptanthrin with a pharmacological indoloquinazoline moiety can not only be modified by different functional groups to achieve various tryptanthrin derivatives, which may realize the improvement of anticancer activity, but also bind with different metal ions to obtain varied tryptanthrin metal complexes as potential anticancer agents, due to their higher anticancer activities in comparison with tryptanthrin (or its derivatives) and cisplatin. This review outlines the recent advances in the syntheses, structures, and anticancer activities of tryptanthrin derivatives and their metal complexes, trying to reveal their structure-activity relationships and to provide a helpful way for medicinal chemists in the development of new and effective tryptanthrin-based anticancer agents.

Visible-light promoted catalyst-free (VLCF) multi-component synthesis of spiro indolo-quinazolinone-pyrrolo[3,4-a]pyrrolizine hybrids: evaluation of in vitro anticancer activity, molecular docking, MD simulation and DFT studies

A new and highly efficient visible-light-promoted catalyst free (VLCF) strategy for neat and clean synthesis of spiro indolo-quinazolinone-pyrrolo[3,4-a]pyrrolizine hybrids (6a-d) has been introduced. We have performed visible-light triggered 1,3-Dipolar cycloaddition reaction of maleimide (5a-d) with azomethine ylide generated in situ derived from tryptanthrin (3) and L-proline (4) to obtain desired products (6a-d) in good to excellent yield. Authentication and characterization of product was done using various spectroscopic techniques such as IR, 1H NMR, 13C NMR, Mass spectrometry and single crystal XRD analysis. To explain the reaction spontaneity, product stability, reactivity as well as possible mode of the interaction a quantum chemical investigation was performed and depicted through DFT studies. The synthesized compound 6a was also evaluated for anti-proliferative activity against a panel of five cancer cell lines (MCF-7, MDA-MB-231, HeLa, PC-3 and Ishikawa) and normal human embryonic kidney (HEK-293) cell line by using MTT assay. Compound 6a showed very good in vitro anti-proliferative activity (IC50  = 6.58-17.98 μM) against four cancer cell lines and no cytotoxicity against normal HEK-293. In order to evaluate the anticancer potential of compounds 6a-d, molecular docking was performed against wild type and mutant EGFR. The results suggest that all the compounds occupied the active site of both enzymes, with a strong binding energy (-10.2 to -11.5 kcal/mol). These results have been confirmed by molecular dynamics simulation by evaluating root mean square deviation (RMSD) and root mean square fluctuation (RMSF), along with principal component analysis (PCA).Communicated by Ramaswamy H. Sarma.

Discovery of Tryptanthrin and Its Derivatives and Its Activities against NSCLC In Vitro via Both Apoptosis and Autophagy Pathways

In this study, a series of novel tryptanthrin derivatives were synthesized and their inhibitory activities against selected human cancer cell lines, namely, lung (A549), chronic myeloid leukemia (K562), prostate (PC3), and live (HepG2), were evaluated using a methyl thiazolyl tetrazolium colorimetric (MTT) assay. Among the tested compounds, compound C1 exhibited a promising inhibitory effect on the A549 cell line with an IC₅₀ value of 0.55 ± 0.33 µM. The observation of the cell morphological result showed that treatment with C1 could significantly inhibit the migration of A549 cells through the cell migration assay. Moreover, after treatment with C1, the A549 cells exhibited a typical apoptotic morphology and obvious autophagy. In addition, the detection of apoptosis and the mitochondrial membrane potential indicated that C1 induced A549 cell apoptosis via modulating the levels of Bcl2 family members and disrupted the mitochondrial membrane potential. Compound C1 also suppressed the expression of cyclin D1 and increased the expression of p21 in the A549 cells, inducing cell cycle arrest in the G2/M phase in a dose dependent manner. The further mechanism study found that C1 markedly increased the transformation from LC3-I to LC3-II. Taken together, our results suggest that C1 is capable of inhibiting the proliferation of non-small cell lung cancer (NSCLC) cells, inducing cell apoptosis, and triggering autophagy.

Tryptanthrin ameliorates imiquimod-induced psoriasis in mice by suppressing inflammation and oxidative stress via NF-κB/MAPK/Nrf2 pathways

Nowadays, approximately 3% of the world's population suffers from psoriasis, an inflammatory dermatosis with high recurrence. Tryptanthrin (TRYP) is a natural alkaloid that possesses anti-inflammatory activities on multiple diseases. The present study aimed to unravel whether TRYP could relieve psoriasis and how it works. Imiquimod (IMQ)-induced psoriatic mouse models were administered saline (model), TRYP (25 and 100 mg/kg), or methotrexate (MTX, 1 mg/kg) and considered as the positive control. TNF-α-induced keratinocytes (HaCaT cells) with TRYP (0, 10, 20 and 50 nM) were used for in vitro verification. Psoriasis area severity index (PASI) and spleen index were evaluated. Th17 cell infiltration in both spleens and lymph nodes was detected by flow cytometry. The expression levels of inflammatory cytokines, glutathione (GSH), malondialdehyde (MDA) and catalase (CAT), as well as superoxide dismutase (SOD), were examined by ELISA, while the NF-κB/MAPK/Nrf2 pathways-related proteins were determined by western blot. TRYP significantly attenuated psoriatic skin lesions, increased GSH, SOD, and CAT levels, reduced spleen index, accumulation of MDA, the abundance of Th17 cells in both the spleen and lymph nodes, and secretion of inflammatory cytokines in IMQ-induced psoriatic mouse models. Mechanically, TRYP suppressed IMQ-activated NF-κB (IκB and p65), MAPK (JNK, ERK1/2, and p38), and activated Nrf2 signaling pathways. Similar alterations for inflammation and oxidative stress parameters and NF-κB/MAPK/Nrf2 pathways were also observed in TNF-α-treated HaCaT cells upon TRYP treatment. Our findings suggested TRYP is effective in protecting against inflammation and oxidative stress in psoriasis-like pathogenesis by modulating the NF-κB/MAPK/Nrf2 pathways.

Phytochemical Targeting of Mitochondria for Breast Cancer Chemoprevention, Therapy, and Sensitization

Breast cancer is a common and deadly disease that causes tremendous physical, emotional, and financial burden on patients and society. Early-stage breast cancer and less aggressive subtypes have promising prognosis for patients, but in aggressive subtypes, and as cancers progress, treatment options and responses diminish, dramatically decreasing survival. Plants are nutritionally rich and biologically diverse organisms containing thousands of metabolites, some of which have chemopreventive, therapeutic, and sensitizing properties, providing a rich source for drug discovery. In this study we review the current landscape of breast cancer with a central focus on the potential role of phytochemicals for treatment, management, and disease prevention. We discuss the relevance of phytochemical targeting of mitochondria for improved anti-breast cancer efficacy. We highlight current applications of phytochemicals and derivative structures that display anti-cancer properties and modulate cancer mitochondria, while describing future applicability and identifying areas of promise.

Pharmacological attenuation of melanoma by tryptanthrin pertains to the suppression of MITF-M through MEK/ERK signaling axis

Melanoma is the most aggressive among all types of skin cancers. The current strategies against melanoma utilize BRAFV600E, as a focal point for targeted therapy. However, therapy resistance developed in melanoma patients against the conventional anti-melanoma drugs hinders the ultimate benefits of targeted therapies. A major mechanism by which melanoma cells attain therapy resistance is via the activation of microphthalmia-associated transcription factor-M (MITF-M), the key transcription factor and oncogene aiding the survival of melanoma cells. We demonstrate that tryptanthrin (Tpn), an indole quinazoline alkaloid, which we isolated and characterized from Wrightia tinctoria, exhibits remarkable anti-tumor activity towards human melanoma through the down-regulation of MITF-M. Microarray analysis of Tpn-treated melanoma cells followed by a STRING protein association network analysis revealed that differential expression of genes in melanoma converges at MITF-M. Furthermore, in vitro and in vivo studies conducted using melanoma cells with differential MITF-M expression status, endogenously or ectopically, demonstrated that the anti-melanoma activity of Tpn is decisively contingent on its efficacy in down-regulating MITF-M expression. Tpn potentiates the degradation of MITF-M via the modulation of MEK1/2-ERK1/2-MITF-M signaling cascades. Murine models demonstrate the efficacy of Tpn in attenuating the migration and metastasis of melanoma cells, while remaining pharmacologically safe. In addition, Tpn suppresses the expression of mutated BRAFV600E and inhibits Casein Kinase 2α, a pro-survival enzyme that regulates ERK1/2 homeostasis in many tumor types, including melanoma. Together, we point to a promising anti-melanoma drug in Tpn, by virtue of its attributes to impede melanoma invasion and metastasis by attenuating MITF-M.

The Natural Alkaloid Tryptanthrin Induces Apoptosis-like Death in Leishmania spp

Leishmaniasis is a vector-borne disease against which there are no approved vaccines, and the treatment is based on highly toxic drugs. The alkaloids consist of a chemical class of natural nitrogen-containing substances with a long history of antileishmanial activity. The present study aimed at determining the antileishmanial activity and in silico pharmacokinetic and toxicological potentials of tryptanthrin alkaloid. The anti-Leishmania amazonensis and anti-L. infantum assays were performed against both promastigotes and intracellular amastigotes. Cellular viability was determined by parasites’ ability to grow (promastigotes) or differentiate (amastigotes) after incubation with tryptanthrin. The mechanisms of action were explored by mitochondrion dysfunction and apoptosis-like death evaluation. For the computational pharmacokinetics and toxicological analysis (ADMET), tryptanthrin was submitted to the PreADMET webserver. The alkaloid displayed anti-promastigote activity against L. amazonensis and L. infantum (IC₅₀ = 11 and 8.0 μM, respectively). Tryptanthrin was active against intracellular amastigotes with IC₅₀ values of 75 and 115 μM, respectively. Mitochondrial membrane depolarization was observed in tryptanthrin-treated promastigotes. In addition, parasites undergoing apoptosis-like death were detected after 18 h of exposure. In silico ADMET predictions revealed that tryptanthrin has pharmacokinetic and toxicological properties similar to miltefosine. The results presented herein demonstrate that tryptanthrin is an interesting drug candidate against leishmaniasis.

Cancer Chemoprevention: A Strategic Approach Using Phytochemicals

Cancer chemoprevention approaches are aimed at preventing, delaying, or suppressing tumor incidence using synthetic or natural bioactive agents. Mechanistically, chemopreventive agents also aid in mitigating cancer development, either by impeding DNA damage or by blocking the division of premalignant cells with DNA damage. Several pre-clinical studies have substantiated the benefits of using various dietary components as chemopreventives in cancer therapy. The incessant rise in the number of cancer cases globally is an issue of major concern. The excessive toxicity and chemoresistance associated with conventional chemotherapies decrease the success rates of the existent chemotherapeutic regimen, which warrants the need for an efficient and safer alternative therapeutic approach. In this scenario, chemopreventive agents have been proven to be successful in protecting the high-risk populations from cancer, which further validates chemoprevention strategy as rational and promising. Clinical studies have shown the effectiveness of this approach in managing cancers of different origins. Phytochemicals, which constitute an appreciable proportion of currently used chemotherapeutic drugs, have been tested for their chemopreventive efficacy. This review primarily aims to highlight the efficacy of phytochemicals, currently being investigated globally as chemopreventives. The clinical relevance of chemoprevention, with special emphasis on the phytochemicals, curcumin, resveratrol, tryptanthrin, kaempferol, gingerol, emodin, quercetin genistein and epigallocatechingallate, which are potential candidates due to their ability to regulate multiple survival pathways without inducing toxicity, forms the crux of this review. The majority of these phytochemicals are polyphenols and flavanoids. We have analyzed how the key molecular targets of these chemopreventives potentially counteract the key drivers of chemoresistance, causing minimum toxicity to the body. An overview of the underlying mechanism of action of these phytochemicals in regulating the key players of cancer progression and tumor suppression is discussed in this review. A summary of the clinical trials on the important phytochemicals that emerge as chemopreventives is also incorporated. We elaborate on the pre-clinical and clinical observations, pharmacokinetics, mechanism of action, and molecular targets of some of these natural products. To summarize, the scope of this review comprises of the current status, limitations, and future directions of cancer chemoprevention, emphasizing the potency of phytochemicals as effective chemopreventives.

Synthetic Tryptanthrin Derivatives Induce Cell Cycle Arrest and Apoptosis via Akt and MAPKs in Human Hepatocellular Carcinoma Cells

Trytanthrin, found in Ban-Lan-Gen, is a natural product containing an indoloquinazoline moiety and has been shown to possess anti-inflammatory and anti-viral activities. Chronic inflammation and hepatitis B are known to be associated with the progression of hepatocellular carcinoma (HCC). In this study, a series of tryptanthrin derivatives were synthesized to generate potent anti-tumor agents against HCC. This effort yielded two compounds, A1 and A6, that exhibited multi-fold higher cytotoxicity in HCC cells than the parent compound. Flow cytometric analysis demonstrated that A1 and A6 caused S-phase arrest and downregulated the expression of cyclin A1, B1, CDK2, and p-CDC2. In addition to inducing caspase-dependent apoptosis, A1 and A6 exhibited similar regulation of the phosphorylation or expression of multiple signaling targets, including Akt, NF-κB, and mitogen-activated protein kinases. The anti-tumor activities of A1 and A6 were also attributable to the generation of reactive oxygen species, accompanied by an increase in p-p53 levels. Therefore, A1 and A6 have potential clinical applications since they target diverse aspects of cancer cell growth in HCC.

Smart transformable nanomedicines for cancer therapy

Despite that great progression has been made in nanoparticulate drug delivery systems (nano-DDS), multiple drug delivery dilemmas still impair the delivery efficiency of nanomedicines. Rational design of smart transformable nano-DDS based on the in vivo drug delivery process represents a promising strategy for overcoming delivery obstacle of nano-DDS. In recent years, tremendous efforts have been devoted to developing smart transformable anticancer nanomedicines. Herein, we provide a review to outline the advances in this emerging field. First, smart size-reducible nanoparticles (NPs) for deep tumor penetration are summarized, including carrier degradation-induced, protonation-triggered and photobleaching-induced size reduction. Second, emerging transformable nanostructures for various therapeutic applications are discussed, including prolonging tumor retention, reversing drug-resistance, inhibiting tumor metastasis, preventing tumor recurrence and non-pharmaceutical therapy. Third, shell-detachable nanocarriers are introduced, focusing on chemical bonds breaking-initiated, charge repulsion-mediated and exogenous stimuli-triggered shell detachment approaches. Finally, the future perspectives and challenges of transformable nanomedicines in clinical cancer therapy are highlighted.

Strobilanthes cusia (Nees) Kuntze, a multifunctional traditional Chinese medicinal plant, and its herbal medicines: A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Strobilanthes cusia (Nees) Kuntze (SCK, Malan), a traditional Chinese medicinal plant, has long applied to detoxification, defervescence, detumescence and antiphlogosis. "Southern Banlangen" (Rhizoma et Radix Baphicacanthis Cusiae, RRBC), root and rhizome of SCK, is widely used for treatment of many epidemic diseases. Malanye (Southern Daqingye), stem and leaf of SCK, is an antipyretic-alexipharmic drug frequently-used in southern China. Qingdai (Indigo Naturalis, IN), a processed product of SCK, is always applied to dermatoses in the folk.

AIM OF THE REVIEW

In order to elucidate the historical uses, recent advances and pharmaceutical prospects of SCK, we summarized roundly in aspects of history, processing method, chemical constitution, quality control, pharmacological activity and toxicity. Some deficiencies in current studies and research directions in the future are also discussed. This is the first comprehensive review of SCK and its herbal medicines, which may be of some help for further research.

METHODOLOGY

Comprehensive analysis was conducted on the basis of academic papers, pharmaceutical monographs, ancient medicinal works, and drug standards of China. All available information on SCK and its herbal medicines was collected by using the keywords such as "Strobilanthes cusia", "Southern Banlangen", "indirubin", "tryptanthrin" through different electronic databases including NCBI Pubmed, Google Scholar, Chinese National Knowledge Infrastructure and so on. Pharmacopoeia of China and some ancient works were obtained from National Digital Library of China.

RESULT

Medicinal uses of SCK were already described by famous ancient researchers. Because of vague description, plant species in some works cannot be confirmed. Literature demonstrated that multiple components including total 36 alkaloids and 35 glycosides, the main bioactive components of SCK, were found in SCK and its herbal medicines. Modern studies indicated that SCK and some of its components had multiple pharmacological effects including resistance to cancer, remission of inflammation, suppression of microorganisms, relief of dermatoses, and so on. However, studies on pharmacology, pharmacokinetics, and quality control are still not enough.

CONCLUSION

A number of reports suggested that SCK and its processed medicines could be promising drug candidates for multiple diseases especially promyelocytic leukemia, ulcerative colitis (UC) and psoriasis. However, bioactive activities of most components, especially glycosides should still be explored further. It is crucial to elucidate the in-depth molecular mechanisms, and pharmacokinetic characteristics of main components in those herbal medicines. Moreover, to ensure the effectiveness of clinical medication, future studies should undoubtedly give the priority to clarifying the effective compositions of SCK, and then a measurement standard of those indicators should be protocolled to establish a comprehensive quality evaluation mode.

Tryptanthrin from microwave-assisted reduction of isatin using solid-state-supported sodium borohydride: DFT calculations, molecular docking and evaluation of its analgesic and anti-inflammatory activity

Tryptanthrin is a potent natural alkaloid with good in vitro pharmacological properties. Herein, we report the synthesis of the compound via a new method involving the reduction of isatin with solid-state-supported sodium borohydride under microwave irradiation. The title compound has been tested for its analgesic and anti-inflammatory activity. The results showed that tryptanthrin dose dependently inhibits oedema and pain formation in all the models used. The agent also exhibited significant higher effects in its anti-inflammatory and analgesic activities better than positive drugs (aspirin and indomethacin) being currently used in the treatment and in the management of acute and chronic forms of pain and inflammatory disorders. The inhibitory potential of the compound was investigated by molecular docking using the software AutoDock Vina. The docking results were used to better rationalize the action and prediction of the binding affinity of tryptanthrin. Density Functional Theory (DFT) calculations at the B3LYP/6-311++G (2df, 2pd) level of theory showed that compared to ascorbic acid, tryptanthrin shows higher antioxidant activity which may be improved upon by functionalizing the aromatic core to enhance its solubility in polar solvents. The calculated electronic and thermodynamic properties obtained for tryptanthrin compete well with the standard ascorbic acid.

From natural dye to herbal medicine: a systematic review of chemical constituents, pharmacological effects and clinical applications of indigo naturalis

Background

Indigo naturalis is a blue dye in ancient, as well as an extensive used traditional Chinese medicine. It has a wide spectrum of pharmacological properties and can be used to treat numerous ailments such as leukemia, psoriasis, and ulcerative colitis. This article aims to expand our understanding of indigo naturalis in terms of its chemical constituents, pharmacological action and clinical applications.

Methods

We searched PubMed, web of science, CNKI, Google academic, Elsevier and other databases with the key words of “Indigo naturalis”, and reviewed and sorted out the modern research of indigo naturalis based on our research results.

Results

We outlined the traditional manufacturing process, chemical composition and quality control of indigo naturalis, systematically reviewed traditional applictions, pharmacological activities and mechanism of indigo naturalis, and summarized its clinical trials about treatment of psoriasis, leukemia and ulcerative colitis.

Conclusions

Indigo naturalis has a variety of pharmacological activities, such as anti-inflammatory, antioxidant, antibacterial, antiviral, immunomodulatory and so on. It has very good clinical effect on psoriasis, leukemia and ulcerative colitis. However, it should be noted that long-term use of indigo naturalis may produce some reversible adverse reactions. In summarize, indigo naturalis is an extremely important drug with great value and potential.

Isatis tinctoria L. (Woad): A Review of its Botany, Ethnobotanical Uses, Phytochemistry, Biological Activities, and Biotechnological Studies

Isatis tinctoria L. (Brassicaceae), which is commonly known as woad, is a species with an ancient and well-documented history as an indigo dye and medicinal plant. Currently, I. tinctoria is utilized more often as medicinal remedy and also as a cosmetic ingredient. In 2011, I. tinctoria root was accepted in the official European phytotherapy by introducing its monograph in the European Pharmacopoeia. The biological properties of raw material have been known from Traditional Chinese Medicine (TCM). Over recent decades, I. tinctoria has been investigated both from a phytochemical and a biological point of view. The modern in vitro and in vivo scientific studies proved anti-inflammatory, anti-tumour, antimicrobial, antiviral, analgesic, and antioxidant activities. The phytochemical composition of I. tinctoria has been thoroughly investigated and the plant was proven to contain many valuable biologically active compounds, including several alkaloids, among which tryptanthrin, indirubin, indolinone, phenolic compounds, and polysaccharides as well as glucosinolates, carotenoids, volatile constituents, and fatty acids. This article provides a general botanical and ethnobotanical overview that summarizes the up-to-date knowledge on the phytochemistry and biological properties of this valuable plant in order to support its therapeutic potential. Moreover, the biotechnological studies on I. tinctoria, which mainly focused on hairy root cultures for the enhanced production of flavonoids and alkaloids as well as on the establishment of shoot cultures and micropropagation protocols, were reviewed. They provide input for future research prospects.

Biodegradable reduction and pH dual-sensitive polymer micelles based on poly(2-ethyl-2-oxazoline) for efficient delivery of curcumin

A series of disulfide-linked amphiphilic polymers polyoxaline-SS-poly(lactide) (PEtOx-SS-PLA) were prepared and self-assembled into nano-micelles in water.

Nano-encapsulated tryptanthrin derivative for combined anticancer therapy via inhibiting indoleamine 2,3-dioxygenase and inducing immunogenic cell death

Aim: We developed a polycaprolactone-based nanoparticle (NP) to encapsulate tryptanthrin derivative CY-1-4 and evaluated its antitumor efficacy. Materials & methods: CY-1-4 NPs were prepared and evaluated for their cytotoxicity and associated mechanisms, indoleamine 2,3-dioxygenase (IDO)-inhibitory ability, immunogenic cell death (ICD)-inducing ability and antitumor efficacy. Results: CY-1-4 NPs were 123 nm in size. In vitro experiments indicated that they could both induce ICD and inhibit IDO. In vivo studies indicated that a medium dose reduced 58% of the tumor burden in a B16-F10-bearing mouse model, decreased IDO expression in tumor tissues and regulated lymphocytes subsets in spleen and tumors. Conclusion: CY-1-4 is a potential antitumor candidate that could act as a single agent with combined functions of IDO inhibition and ICD induction.

Inhibiting eukaryotic ribosome biogenesis

BACKGROUND

Ribosome biogenesis is a central process in every growing cell. In eukaryotes, it requires more than 250 non-ribosomal assembly factors, most of which are essential. Despite this large repertoire of potential targets, only very few chemical inhibitors of ribosome biogenesis are known so far. Such inhibitors are valuable tools to study this highly dynamic process and elucidate mechanistic details of individual maturation steps. Moreover, ribosome biogenesis is of particular importance for fast proliferating cells, suggesting its inhibition could be a valid strategy for treatment of tumors or infections.

RESULTS

We systematically screened ~ 1000 substances for inhibitory effects on ribosome biogenesis using a microscopy-based screen scoring ribosomal subunit export defects. We identified 128 compounds inhibiting maturation of either the small or the large ribosomal subunit or both. Northern blot analysis demonstrates that these inhibitors cause a broad spectrum of different rRNA processing defects.

CONCLUSIONS

Our findings show that the individual inhibitors affect a wide range of different maturation steps within the ribosome biogenesis pathway. Our results provide for the first time a comprehensive set of inhibitors to study ribosome biogenesis by chemical inhibition of individual maturation steps and establish the process as promising druggable pathway for chemical intervention.

One-pot mild and efficient synthesis of [1,3]thiazino[3,2-a]indol-4-ones and their anti-proliferative activity

One-pot synthesis of [1,3]thiazino[3,2-a]indol-4-one frameworks is developed in aqueous medium and the anti-proliferative activity of the synthesized compounds is evaluated against two triple negative breast cancer cell lines.

Sesquiterpene lactone 6-O-angeloylplenolin reverses vincristine resistance by inhibiting YB-1 nuclear translocation in colon carcinoma cells

Multidrug resistance (MDR) is a major obstacle to cancer chemotherapy efficacy. In the present study, 6-O-angeloylplenolin repressed the overexpression of ATP binding cassette subfamily B member 1 (MDR1) and increasing the intracellular concentration of anticancer drugs. A reduction in P-glycoprotein expression (encoded by MDR1) was observed in parallel with a decline in mRNA expression in vincristine-resistant HCT (HCT-8/VCR) cells treated with 6-O-angeloylplenolin. In addition, 6-O-angeloylplenolin suppressed the activity of the MDR1 gene promoter. Treatment with 6-O-angeloylplenolin also decreased the amount of the specific protein complex that interacted with the MDR1 gene promoter in HCT-8/VCR cells, potentially leading to the suppression of MDR1 expression. Treatment with 6-O-angeloylplenolin inhibited the nuclear translocation of Y-box binding protein-1 in HCT-8/VCR cells treated with 6-O-angeloylplenolin, contributing to the negative regulation of MDR1. Finally, 6-O-angeloylplenolin reversed VCR resistance in an HCT/VCR xenograft model. In conclusion, 6-O-angeloylplenolin exhibited a MDR-reversing effect by downregulating MDR1 expression and could represent a novel adjuvant agent for chemotherapy.

Synthesis of visible-light mediated tryptanthrin derivatives from isatin and isatoic anhydride under transition metal-free conditions

Visible light mediated transition metal-free protocol for synthesis of tryptanthrin from isatin and isatoic anhydride in mild reaction conditions.

GMZ-1 is a podophyllotoxin derivative that suppresses growth and induces apoptosis in adriamycin-resistant K562/A02 cells through modulation of MDR1 expression

The incidence of multidrug resistance (MDR) during cancer chemotherapy is a major challenge for treatment. With the aim of identifying drugs that are capable of targeting treatment‑resistant cancer cells, the present study evaluated the efficacy of GMZ‑1 in cancer chemotherapy using K562/A02, an MDR leukemia cell line. Cell viability and apoptosis were measured by MTT assay and flow cytometry/Giemsa staining, respectively. The expression levels of the MDR protein 1 (MDR1) gene transcript and protein in K562/A02 cells were determined by reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. GMZ‑1 suppressed the viability of various human cancer cell lines and induced apoptosis in the K562/A02 cell line in a time‑ and concentration‑dependent manner. GMZ‑1 toxicity may be associated with a decrease in MDR gene expression. These findings demonstrated that GMZ‑1 may have efficacy as a potential antitumor drug to overcome leukemia cell resistance to apoptosis induced by chemotherapy.

Natural alkaloids as P-gp inhibitors for multidrug resistance reversal in cancer

The biggest challenge associated with cancer chemotherapy is the development of cross multi-drug resistance to almost all anti-cancer agents upon chronic treatment. The major contributing factor for this resistance is efflux of the drugs by the p-glycoprotein pump. Over the years, inhibitors of this pump have been discovered to administer them in combination with chemotherapeutic agents. The clinical failure of first and second generation P-gp inhibitors (such as verapamil and cyclosporine analogs) has led to the discovery of third generation potent P-gp inhibitors (tariquidar, zosuquidar, laniquidar). Most of these inhibitors are nitrogenous compounds and recently a natural alkaloid CBT-01^® (tetrandrine) has advanced to the clinical phase. CBT-01 demonstrated positive results in Phase-I study in combination with paclitaxel, which warranted conducting it's Phase II/III trial. Apart from this, there exist a large number of natural alkaloids possessing potent inhibition of P-gp efflux pump and other related pumps responsible for the development of resistance. Despite the extensive contribution of alkaloids in this area, has never been reviewed. The present review provides a comprehensive account on natural alkaloids possessing P-gp inhibition activity and their potential for multidrug resistance reversal in cancer.

Deciphering the Mechanism of Action of Wrightia tinctoria for Psoriasis Based on Systems Pharmacology Approach

OBJECTIVE

Psoriasis is a chronic immune-mediated disorder of the skin. The disease manifests itself with red or silvery scaly plaques distributing over the lower back, scalp, and extensor aspects of limbs. Several medications are available for the treatment of psoriasis; however, high rates of remission and side-effects still persist as a major concern. Siddha, one of the traditional systems of Indian medicine offers cure to many dermatological conditions, including psoriasis. The oil prepared from the leaves of Wrightia tinctoria is prescribed by many healers for the treatment of psoriasis. This work aims to decipher the mechanism of action of the W. tinctoria in curing psoriasis and its associated comorbidities.

DESIGN

The work integrates various pharmacology approaches such as drug-likeness evaluation, oral bioavailability predictions, and network pharmacology approaches to understand the roles of various bioactive components of the herb.

RESULTS

This work identified 67 compounds of W. tinctoria interacting with 238 protein targets. The compounds were found to act through synergistic mechanism in reviving the disrupted process in the diseased state.

CONCLUSION

The results of this work not only shed light on the pharmacological action of the herb but also validate the usage of safe herbal drugs.

Reversal of P-glycoprotein-mediated multidrug resistance is induced by saikosaponin D in breast cancer MCF-7/adriamycin cells

Multidrug resistance (MDR) cells over expressing P-glycoprotein (P-gp) encoded by the MDR1 gene is major obstacles for successful cancer chemotherapy. P-gp could extrude anti-cancer drugs out of cancer cells and decrease effective intracellular drug concentrations. MDR reversal agents for P-gp can restore the sensitivity of MDR cells to such drugs. Saikosaponin D (SSd), one of the major triterpenoid saponins derived from Bupleurum chinense DC (BCDC), has been shown to possess anti-inflammatory, anti-infectious and anti-tumor properties. The aim of the present study was to investigate the reversal effect of SSd on MDR in MCF-7/adriamycin (ADR) human breast cancer cells and investigate the underlying mechanisms of SSd. The results demonstrated that SSd inhibited the proliferation of MCF-7/ADR and MCF-7 cells in a dose-dependent manner. Moreover, SSd increased the cytotoxicity of ADR on MCF-7/ADR cells and the resistance fold of SSd treatment was demonstrated to be significantly higher when compared with that of the group without SSd treatment. Additionally, the effects of the drug combination showed that SSd and ADR combination were synergistic. Accumulation and efflux studies with the P-gp substrate, rhodamine 123 (Rh123), demonstrated that SSd restored Rh123 accumulation and inhibited P-gp-mediated drug efflux. Importantly, we found that SSd could enhance the sensitivity of MCF-7/ADR cells towards ADR by down-regulating MDR1 and P-gp expression. In conclusion, the results of the present study indicated that SSd may represent a potent reversal agent for P-gp-mediated MDR in breast cancer therapy.

Tryptanthrin Suppresses the Activation of the LPS-Treated BV2 Microglial Cell Line via Nrf2/HO-1 Antioxidant Signaling

Microglia are the resident macrophages in the central nervous system (CNS) and play essential roles in neuronal homeostasis and neuroinflammatory pathologies. Recently, microglia have been shown to contribute decisively to neuropathologic processes after ischemic stroke. Furthermore, natural compounds have been reported to attenuate inflammation and pathologies associated with neuroinflammation. Tryptanthrin (indolo[2,1-b]quinazoline-6,12-dione) is a phytoalkaloid with known anti-inflammatory effects in cells. In present study, the authors confirmed middle cerebral artery occlusion (MCAO) injury triggers the activation of microglia in brain tissue, and investigated whether tryptanthrin influences the function of mouse murine BV2 microglia under LPS-induced inflammatory conditions in vitro. It was found tryptanthrin protected BV2 microglia cells against LPS-induced inflammation and inhibited the induction of M1 phenotype microglia under inflammatory conditions. In addition, tryptanthrin reduced the production of pro-inflammatory cytokines in BV2 microglia cells via nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) signaling and NF-κB signaling. The authors suggest that tryptanthrin might alleviate the progress of neuropathologies by controlling microglial functions under neuroinflammatory conditions.

Characterization of anti-leukemia components from Indigo naturalis using comprehensive two-dimensional K562/cell membrane chromatography and in silico target identification

Traditional Chinese Medicine (TCM) has been developed for thousands of years and has formed an integrated theoretical system based on a large amount of clinical practice. However, essential ingredients in TCM herbs have not been fully identified, and their precise mechanisms and targets are not elucidated. In this study, a new strategy combining comprehensive two-dimensional K562/cell membrane chromatographic system and in silico target identification was established to characterize active components from Indigo naturalis, a famous TCM herb that has been widely used for the treatment of leukemia in China, and their targets. Three active components, indirubin, tryptanthrin and isorhamnetin, were successfully characterized and their anti-leukemia effects were validated by cell viability and cell apoptosis assays. Isorhamnetin, with undefined cancer related targets, was selected for in silico target identification. Proto-oncogene tyrosine-protein kinase (Src) was identified as its membrane target and the dissociation constant (Kd) between Src and isorhamnetin was 3.81 μM. Furthermore, anti-leukemia effects of isorhamnetin were mediated by Src through inducing G2/M cell cycle arrest. The results demonstrated that the integrated strategy could efficiently characterize active components in TCM and their targets, which may bring a new light for a better understanding of the complex mechanism of herbal medicines.

Gain-of-function p53 mutant with 21-bp deletion confers susceptibility to multidrug resistance in MCF-7 cells

The majority of p53 mutations, which are responsible for gain of oncogenic function, are missense mutations in hotspot codons. However, in our previous study, we demonstrated that a deletion spanning codons 127-133 in the p53 gene (designated as del p53) was detected in doxorubicin-resistant MCF-7 cell lines following various induction processes. In the present study, we aimed to investigate the role of del p53 and its association with the proliferation, metastasis and drug resistance of MCF-7 cells. The MCF-7/del p53 cell line is a representative of the del p53 stably expressed clones which were constructed by transfection of the del p53-containing construct into MCF-7/wt cells. Markers of multidrug resistance (MDR), epithelial-mesenchymal transition (EMT) and stem cell-like properties were examined in the MCF-7/del p53 cells. The results revealed that the MCF-7/del p53 cells expressed full-length p53 and del p53 mRNA and protein, as well as P-glycoprotein (P-gp). The MCF-7/del p53 cells acquired resistance to doxorubicin with increased P-gp efflux function. Using a transient expression assay, the mdr1 promoter was found to be significantly activated by external or integrated del p53 (P<0.001). The inhibition of nuclear factor (NF)-κB by cyclosporine sensitized the MCF-7/del p53 cells to doxorubicin toxicity. In addition, the morphological characteristics of the MCF-7/del p53 and MCF-7/adr were similar. EMT was observed in the MCF-7/del p53 cells as demonstrated by the presence of the mesenchymal markers, Slug and vimentin, and the decrease in the epithelial marker, cadherin 1, type 1, E-cadherin (CDH1), as well as an enhanced migration ability (P<0.001). Furthermore, the number of cells expressing the cancer stem cell-like marker, CD44, increased, accompanied by mammosphere formation. Taken together, these findings indicate that the expression of del p53 in MCF-7/del p53 cells enables the cells to partially acquire doxorubicin resistance characteristics of the MCF-7/adr cells. Thus, del p53 may be an important factor in non-invasive MCF-7 cells, activating NF-κB signaling and the mdr1 promoter and partially attributing to EMT; the cells thus acquire stem cell‑like properties, which facilitates drug resistance. Therefore, the 21-bp deletion of p53 may prove to be a therapeutic strategy with which to prevent cancer cells from acquiring resistance to drugs.

Quercetin and Tryptanthrin: Two Broad Spectrum Anticancer Agents for Future Chemotherapeutic Interventions

The idea and practice of developing or identifying compounds capable of eliminating the transformed cells or cancer cells without being nontoxic to their normal counterparts deserves much importance. Since ages, plants have been considered and proven to be repertoires of chemicals possessing immense therapeutic potential. A proportion of these plant-derived compounds or phytochemicals were shown to be highly competent anticancer agents besides being effective against many other diseases. Representative compounds of different classes of phytochemicals are in clinical use against cancer. In this chapter, we discuss the anticancer potential of two compounds: quercetin, a flavonoid and tryptanthrin, an indoloquinazoline alkaloid, and the mechanisms behind their cytotoxic effects on cancers of different origin. The chapter also gives a brief mention of their properties that make them effective against cancer.

DW-F5: A novel formulation against malignant melanoma from Wrightia tinctoria

Wrightia tinctoria is a constituent of several ayurvedic preparations against skin disorders including psoriasis and herpes, though not yet has been explored for anticancer potential. Herein, for the first time, we report the significant anticancer properties of a semi-purified fraction, DW-F5, from the dichloromethane extract of W. tinctoria leaves against malignant melanoma. DW-F5 exhibited anti-melanoma activities, preventing metastasis and angiogenesis in NOD-SCID mice, while being non-toxic in vivo. The major pathways in melanoma signaling mediated through BRAF, WNT/β-catenin and Akt-NF-κB converging in MITF-M, the master regulator of melanomagenesis, were inhibited by DW-F5, leading to complete abolition of MITF-M. Purification of DW-F5 led to the isolation of two cytotoxic components, one being tryptanthrin and the other being an unidentified aliphatic fraction. The overall study predicts Wrightia tinctoria as a candidate plant to be further explored for anticancer properties and DW-F5 as a forthcoming drug formulation to be evaluated as a chemotherapeutic agent against malignant melanoma.

Synthesis and evaluation of the antiplasmodial activity of tryptanthrin derivatives

•

We report the synthesis of tryptanthrin derivatives.

•

We report the activity of tryptanthrin derivatives against Plasmodium falciparum.

•

We discuss the potential of tryptanthrin derivatives as multi-stage drugs.

•

We recommend the formulation and testing of tryptanthrins in in vivo studies.

Malaria remains one of the most deadly diseases threatening humankind and is still affecting a significant proportion of the world population, especially in Africa. Chemotherapy is a vital component of the fight against the disease and new antimalarial agents are urgently needed to curb the spread of malaria parasites that are resistant to existing drugs. The natural product tryptanthrin is known for its wide range of activities, including antiplasmodial activity, but its poor solubility has undermined its development as potent antimicrobial and antiprotozoan agent. The aim of this work was to synthesize analogues of tryptanthrin and to evaluate their antiplasmodial activity against the asexual and sexual blood stages of Plasmodium falciparum. Our results suggest that most tryptanthrin analogues retained their antiplasmodial activity against chloroquine-sensitive and chloroquine-resistant malaria parasites in the nanomolar range (30–100 nM). The antiplasmodial activity of the most active compound NT1 (IC₅₀: 30 nM; SI: 155.9) was similar in both strains and close to that of chloroquine (IC₅₀: 20 nM) on the sensitive strain. The antiplasmodial activity was improved with derivatization, thus pointing out the necessity to explore tryptanthrin using medicinal chemistry approaches. Ten (10) of the tested derivatives met the criteria, allowing for advancement to animal testing, i.e., SI > 100 and IC₅₀ < 100 nM. In addition to their activity on the asexual stages, tryptanthrin and two selected derivatives (NT1 and T8) prevented the maturation of gametocytes at their IC₉₀ concentrations, indicating a transmission-blocking potential. Moreover, NT1 was able to impair gametogenesis by reducing the exflagellation of microgametes by 20% at IC₉₀, while tryptanthrin and T8 had no influence on exflagellation. The results of this study confirm that tryptanthrin and its derivatives are potential antimalarial candidates with abilities to kill the intraerythrocytic asexual stages and prevent the formation of sexual stages of the parasite.

A critical dose of doxorubicin is required to alter the gene expression profiles in MCF-7 cells acquiring multidrug resistance

Cellular mechanisms of multidrug resistance (MDR) are related to ABC transporters, apoptosis, antioxidation, drug metabolism, DNA repair and cell proliferation. It remains unclear whether the process of resistance development is programmable. We aimed to study gene expression profiling circumstances in MCF-7 during MDR development. Eleven MCF-7 sublines with incremental doxorubicin resistance were established as a valued tool to study resistance progression. MDR marker P-gp was overexpressed only in cells termed MCF-7/ADR-1024 under the selection dose approaching 1024 nM. MCF-7/ADR-1024 and authentic MCF-7/ADR shared common features in cell morphology and DNA ploidy status. MCF-7/ADR-1024 and authentic MCF-7/ADR down regulated repair genes BRCA1/2 and wild type p53, apoptosis-related gene Bcl-2 and epithelial-mesenchymal transition (EMT) epithelial marker gene E-cadherin. While detoxifying enzymes glutathione-S transferase-π and protein kinase C-α were up-regulated. The genes involving in EMT mesenchymal formation were also overexpressed, including N-cadherin, vimentin and the E-cadherin transcription reppressors Slug, Twist and ZEB1/2. PI3K/AKT inhibitor wortmannin suppressed expression of Slug, Twist and mdr1. Mutant p53 with a deletion at codons 127-133 markedly appeared in MCF-7/ADR-1024 and authentic MCF-7/ADR as well. In addition, MCF-7/ADR-1024 cells exerted CSC-like cell surface marker CD44 high/CD24 low and form mammospheres. Overall, results suggest that resistance marker P-gp arises owing to turn on/off or mutation of the genes involved in DNA repair, apoptosis, detoxifying enzymes, EMT and ABC transporters at a turning point (1.024 μM doxorubicin challenge). Behind this point, no obvious alterations were found in most tested genes. Selection for CSC-like cells under this dose may importantly attribute to propagation of the population presenting invasive properties and drug resistance. We thereby suggest two models in the induction of drug resistance. Model 1: Selection for CSC-like cells. Model 2: Mutations for gain-of resistance. Either model 1 or model 2 requires doxorubicin dose approaching 1 μM to alter gene regulation.

The synthetic tryptanthrin analogue suppresses STAT3 signaling and induces caspase dependent apoptosis via ERK up regulation in human leukemia HL-60 cells

Tryptanthrin is a natural product which has been reported to have several medicinal properties. In this study, we tried to investigate the detailed molecular mechanism of its bromo analogue (TBr), a potent cytotoxic agent in the induction of cancer cell death. It was found that TBr primarily targets STAT3 and ERK signaling during the induction of apoptosis in several human leukemia cell lines. In HL-60 cells, TBr treatment caused early down regulation of p-STAT3 with concomitant up regulation of p-ERK which led to the activation of intrinsic and extrinsic pathways of apoptosis. The mechanism of TBr mediated inhibition of p-STAT3 was found to be due to the activation of ubiquitin dependent degradation of tyrosine 705 and serine 727 p-STAT3. As IL-6 is the main driver of the STAT3 pathway, the effect of TBr on cell death was subdued when treated in the combination with IL-6 in HL60 cells. Interestingly, PD98059 significantly reduced the apoptotic effects of TBr, thus showing the direct involvement of p-ERK in TBr mediated cell death. It was further shown that apoptotic protein Bax silencing in HL-60 cells resists TBr mediated ERK dependent apoptosis. In summary, for the first time we report the mechanism of TBr mediated cell death in human leukemia cell lines by targeting STAT3 and ERK pathways.

Efficient pH dependent drug delivery to target cancer cells by gold nanoparticles capped with carboxymethyl chitosan

Doxorubicin (DOX) was immobilized on gold nanoparticles (AuNPs) capped with carboxymethyl chitosan (CMC) for effective delivery to cancer cells. The carboxylic group of carboxymethyl chitosan interacts with the amino group of the doxorubicin (DOX) forming stable, non-covalent interactions on the surface of AuNPs. The carboxylic group ionizes at acidic pH, thereby releasing the drug effectively at acidic pH suitable to target cancer cells. The DOX loaded gold nanoparticles were effectively absorbed by cervical cancer cells compared to free DOX and their uptake was further increased at acidic conditions induced by nigericin, an ionophore that causes intracellular acidification. These results suggest that DOX loaded AuNPs with pH-triggered drug releasing properties is a novel nanotheraputic approach to overcome drug resistance in cancer.

Modulation of drug resistance in ovarian adenocarcinoma using chemotherapy entrapped in hyaluronan-grafted nanoparticle clusters

Resistance to anticancer drugs is considered a major cause of chemotherapy failure. One of the major mediators of resistance is the multidrug extrusion pump protein, P-glycoprotein (P-gp), an ATP-binding cassette (ABC) transporter with broad substrate specificity. In order to bypass this drug resistance mechanism, we have devised phospholipid-based nanoparticle clusters coated with the glycosaminoglycan hyaluronan, the major ligand of CD44, which is upregulated and undergoes different splice variations in many types of cancer cells. These particles, termed glycosaminoglycan particle nanoclusters or gagomers (GAGs), were self-assembled into ∼500 nm diameter clusters, with zeta-potential values of ∼-70 mV. Flow cytometry analysis provided evidence that, unlike free doxorubicin (DOX), a model chemotherapy, DOX entrapped in the GAGs (DOX-GAGs) accumulated in P-gp-overexpressing human ovarian adenocarcinoma cell line and dramatically decreased cell viability, while drug-free GAGs and the commercially available drug DOXIL (PEGylated liposomal DOX) did not produce therapeutic benefit. Furthermore, by using RNA interference strategy, we showed that DOX-GAGs were able to overcome the P-gp-mediated resistant mechanism of these cells. Most importantly, DOX-GAGs showed a superior therapeutic effect over free DOX in a resistant human ovarian adenocarcinoma mouse xenograft model. Taken together, these results demonstrated that GAGs might serve as an efficient platform for delivery of therapeutic payloads by bypassing P-gp-mediated multidrug resistance.