The wisdom of crowds and the repurposing of artesunate as an anticancer drug

Tween 80 Micelles Loaded with Fe3O4 Nanoparticles and Artemisinin for Combined Oxygen-Independent Ferroptosis Therapy of Cancer

Artemisinin has an endoperoxide bridge structure, which can be cleaved by ferrous ions to generate various carbonyl radicals in an oxygen-independent manner, highlighting its potential for treating hypoxic tumors. In our study, we fabricated Tween 80 micelles loaded with Fe3O4 nanoparticles and artemisinin for cancer therapy. The synthesized Fe3O4 nanoparticles and drug-loaded micelles have particle sizes of about 5 nm and 80 nm, respectively, both exhibiting excellent dispersibility and stability. After uptake by MCF-7 cells, drug-loaded micelles release Fe2+ and ART into the cytoplasm, effectively inducing the generation of reactive oxygen species (ROS) in hypoxic conditions, thereby enhancing toxicity against cancer cells. In vitro and in vivo studies have demonstrated that ART and Fe3O4 nanoparticles are encapsulated in Tween 80 to form micelles, which effectively prevent premature release during circulation in the body. Although free ART and Fe3O4 nanoparticles can inhibit tumor growth, TW80-Fe3O4-ART micelles demonstrate a more pronounced inhibitory effect, with a tumor suppression rate of up to 85%. A novel strategy based on artemisinin and ferroptosis is thus offered, holding a favorable prospect for hypoxic cancer therapy.

Repurposing approved non-oncology drugs for cancer therapy: a comprehensive review of mechanisms, efficacy, and clinical prospects

Cancer poses a significant global health challenge, with predictions of increasing prevalence in the coming years due to limited prevention, late diagnosis, and inadequate success with current therapies. In addition, the high cost of new anti-cancer drugs creates barriers in meeting the medical needs of cancer patients, especially in developing countries. The lengthy and costly process of developing novel drugs further hinders drug discovery and clinical implementation. Therefore, there has been a growing interest in repurposing approved drugs for other diseases to address the urgent need for effective cancer treatments. The aim of this comprehensive review is to provide an overview of the potential of approved non-oncology drugs as therapeutic options for cancer treatment. These drugs come from various chemotherapeutic classes, including antimalarials, antibiotics, antivirals, anti-inflammatory drugs, and antifungals, and have demonstrated significant antiproliferative, pro-apoptotic, immunomodulatory, and antimetastatic properties. A systematic review of the literature was conducted to identify relevant studies on the repurposing of approved non-oncology drugs for cancer therapy. Various electronic databases, such as PubMed, Scopus, and Google Scholar, were searched using appropriate keywords. Studies focusing on the therapeutic potential, mechanisms of action, efficacy, and clinical prospects of repurposed drugs in cancer treatment were included in the analysis. The review highlights the promising outcomes of repurposing approved non-oncology drugs for cancer therapy. Drugs belonging to different therapeutic classes have demonstrated notable antitumor effects, including inhibiting cell proliferation, promoting apoptosis, modulating the immune response, and suppressing metastasis. These findings suggest the potential of these repurposed drugs as effective therapeutic approaches in cancer treatment. Repurposing approved non-oncology drugs provides a promising strategy for addressing the urgent need for effective and accessible cancer treatments. The diverse classes of repurposed drugs, with their demonstrated antiproliferative, pro-apoptotic, immunomodulatory, and antimetastatic properties, offer new avenues for cancer therapy. Further research and clinical trials are warranted to explore the full potential of these repurposed drugs and optimize their use in treating various cancer types. Repurposing approved drugs can significantly expedite the process of identifying effective treatments and improve patient outcomes in a cost-effective manner.

The Potential Mechanisms by which Artemisinin and Its Derivatives Induce Ferroptosis in the Treatment of Cancer

Artemisinin (ART) is a bioactive molecule derived from the Chinese medicinal plant Artemisia annua (Asteraceae). ART and artemisinin derivatives (ARTs) have been effectively used for antimalaria treatment. The structure of ART is composed of a sesquiterpene lactone, including a peroxide internal bridge that is essential for its activity. In addition to their well-known antimalarial effects, ARTs have been shown recently to resist a wide range of tumors. The antineoplastic mechanisms of ART mainly include cell cycle inhibition, inhibition of tumor angiogenesis, DNA damage, and ferroptosis. In particular, ferroptosis is a novel nonapoptotic type of programmed cell death. However, the antitumor mechanisms of ARTs by regulating ferroptosis remain unclear. Through this review, we focus on the potential antitumor function of ARTs by acting on ferroptosis, including the regulation of iron metabolism, generation of reactive oxygen species (ROS), and activation of endoplasmic reticulum stress (ERS). This article systematically reviews the recent progress in ferroptosis research and provides a basis for ARTs as an anticancer drug in clinical practice.

Exploring new uses for existing drugs: innovative mechanisms to fund independent clinical research

BACKGROUND

Finding new therapeutic uses for existing medicines could lead to safe, affordable and timely new treatment options for patients with high medical needs. However, due to a lack of economic incentives, pharmaceutical developers are rarely interested to invest in research with approved medicines, especially when they are out of basic patent or regulatory protection. Consequently, potential new uses for these medicines are mainly studied in independent clinical trials initiated and led by researchers from academia, research institutes, or collaborative groups. Yet, additional financial support is needed to conduct expensive phase III clinical trials to confirm the results from exploratory research.

METHODS

In this study, scientific and grey literature was searched to identify and evaluate new mechanisms for funding clinical trials with repurposed medicines. Semi-structured interviews were conducted with 16 European stakeholders with expertise in clinical research, funding mechanisms and/or drug repurposing between November 2018 and February 2019 to consider the future perspectives of applying new funding mechanisms.

RESULTS

Traditional grant funding awarded by government and philanthropic organisations or companies is well known and widely implemented in all research fields. In contrast, only little research has focused on the application potential of newer mechanisms to fund independent clinical research, such as social impact bonds, crowdfunding or public-private partnerships. Interviewees stated that there is a substantial need for additional financial support in health research, especially in areas where there is limited commercial interest. However, the implementation of new funding mechanisms is facing several practical and financial challenges, such as a lack of expertise and guidelines, high transaction costs and difficulties to measure health outcomes. Furthermore, interviewees highlighted the need for increased collaboration and centralisation at a European and international level to make clinical research more efficient and reduce the need for additional funding.

CONCLUSIONS

New funding mechanisms to support clinical research may become more important in the future but the unresolved issues identified in the current study warrant further exploration.

Enhanced lysosomal function is critical for paclitaxel resistance in cancer cells: reversed by artesunate

The mechanism underlying the resistance of cancer cells to chemotherapeutic drug varies with different cancer cells. Recent evidence shows that lysosomal function is associated with drug resistance of cancer cells. Artesunate, a derivative of artemisinin, displays broad antitumor activity and direct cytotoxicity on various tumor cells. Our previous study shows that artesunate increases autophagosome accumulation, while significantly decreases autolysosome number in cancer cells, suggesting that artesunate might impair the lysosomal function. In this study, we investigated the effects of artesunate on lysosomal function and its relationship with chemotherapeutic drug resistance in cancer cells. We found that the lysosomal function was significantly enhanced in two drug-resistant (A549/TAX and A549/DDP) cells. Furthermore, we showed that the enhanced lysosomal function by overexpression of transcription factor EB (TFEB) significantly increased MCF-7 cells resistance to doxorubicin (DOX), whereas the decreased lysosomal function by TFEB-knockdown or lysosome inhibitor chloroquine increased MCF-7 cells sensitivity to DOX. Treatment of A549/TAX cells with artesunate (2.5-50 μM) dose-dependently inhibited lysosomal function and the clearance of dysfunctional mitochondria, and induced cell apoptosis. Moreover, we demonstrated that artesunate exerted more potent inhibition on the resistant (A549/TAX and MCF-7/ADR) cells with higher activity of lysosomal function. Our results suggest that artesunate or other inhibitors of lysosomal function would be potential in the treatment of cancer cells with drug resistance caused by the enhanced lysosomal function.

Artemisinins as a novel anti-cancer therapy: Targeting a global cancer pandemic through drug repurposing

Artemisinins are a unique class of antimalarial drugs with significant potential for drug repurposing for a wide range of diseases including cancer. Cancer is a leading cause of death globally and the majority of cancer related deaths occur in Low and Middle Income Countries (LMICs) where conventional treatment options are often limited by financial cost. Drug repurposing can significantly shorten new therapeutic discovery pathways, ensuring greater accessibility and affordability globally. Artemisinins have an excellent safety and tolerability profile as well as being affordable for deployment in Low and Middle Class Income Countries at around USD1 per daily dose. Robust, well designed clinical trials of artemisinin drug repurposing are indicated for a variety of different cancers and treatment settings.

Antimalarial drug artesunate is effective against chemoresistant anaplastic thyroid carcinoma via targeting mitochondrial metabolism

Anaplastic thyroid carcinoma (ATC) is the most aggressive type of thyroid malignancies and resistant to chemotherapy. Novel therapeutic strategy is required for better management of ATC. In this work, we show that artesunate, an antimalarial drug, is active against chemoresistant ATC cells. Artesunate dose-dependently inhibits growth and induces apoptosis in chemo-sensitive (8505C and KAT-4) and -resistant (8505C-r and KAT-4-r) ATC cells, and acts synergistically with doxorubicin. Using multiple xenograft mouse models, artesunate is active against chemo-sensitive and -resistant ATC cells in vivo at doses that do not cause toxicity in mice. Our mechanism analysis reveals that artesunate acts on ATC cells through suppressing mitochondrial functions without affecting glycolysis, leading to oxidative stress and damage, regardless of whether they are sensitive or resistant to chemotherapy. Interestingly, KAT-4-r cells demonstrate decreased glycolysis, increased mitochondrial membrane potential and mitochondrial respiration compared to KAT-4 cells whereas such phenomenon is not observed between 8505C and 8505C-r cells. This suggests that some but not all ATC cells gain enhanced mitochondrial biogenesis after prolonged exposure to chemotherapy drug, which may explain the different sensitivities of 8505C-r and KAT-4-r to artesunate. Our work demonstrates that artesunate is a potential addition to the treatment armamentarium for ATC, particularly those with chemoresistance. Our findings also highlight the therapeutic value of targeting mitochondria in chemoresistant ATC.

Current status and contemporary approaches to the discovery of antitumor agents from higher plants

Higher plant constituents have afforded clinically available anticancer drugs. These include both chemically unmodified small molecules and their synthetic derivatives currently used or those in clinical trials as antineoplastic agents, and an updated summary is provided. In addition, botanical dietary supplements, exemplified by mangosteen and noni constituents, are also covered as potential cancer chemotherapeutic agents. Approaches to metabolite purification, rapid dereplication, and biological evaluation including analytical hyphenated techniques, molecular networking, and advanced cellular and animal models are discussed. Further, enhanced and targeted drug delivery systems for phytochemicals, including micelles, nanoparticles and antibody drug conjugates (ADCs) are described herein.

Drug Repurposing in the Development of Anticancer Agents

BACKGROUND

Research into repositioning known drugs to treat cancer other than the originally intended disease continues to grow and develop, encouraged in part, by several recent success stories. Many of the studies in this article are geared towards repurposing generic drugs because additional clinical trials are relatively easy to perform and the drug safety profiles have previously been established.

OBJECTIVE

This review provides an overview of anticancer drug development strategies which is one of the important areas of drug restructuring.

METHODS

Repurposed drugs for cancer treatments are classified by their pharmacological effects. The successes and failures of important repurposed drugs as anticancer agents are evaluated in this review.

RESULTS AND CONCLUSION

Drugs could have many off-target effects, and can be intelligently repurposed if the off-target effects can be employed for therapeutic purposes. In cancer, due to the heterogeneity of the disease, often targets are quite diverse, hence a number of already known drugs that interfere with these targets could be deployed or repurposed with appropriate research and development.

Artesunate induces mitochondria-mediated apoptosis of human retinoblastoma cells by upregulating Kruppel-like factor 6

Retinoblastoma (RB) is the most common primary intraocular malignancy in children. Intravitreal chemotherapy achieves favorable clinical outcomes in controlling RB vitreous seeds, which are a common reason for treatment failure. Thus, a novel, effective and safe intravitreal chemotherapeutic drug is urgently required. The malaria drug artesunate (ART) recently demonstrated remarkable anticancer effects with mild side effects. The purpose of this study is to investigate the anti-RB efficacy, the underlying mechanism and the intraocular safety of ART. Herein, we verified that ART inhibits RB cell viability and induces cell apoptosis in a dose- and time-dependent manner. Microarray analysis revealed that Kruppel-like factor 6 (KLF6) was upregulated after ART treatment, and this was further confirmed by real-time PCR and western blot assays. Silencing of KLF6 expression significantly reversed ART-induced RB cell growth inhibition and apoptosis. Furthermore, ART activated mitochondria-mediated apoptosis of RB cells, while silencing KLF6 expression significantly inhibited this effect. In murine xenotransplantation models of RB, we further confirmed that ART inhibits RB tumor growth, induces tumor cell apoptosis and upregulates KLF6 expression. In addition, KLF6 silencing attenuates ART-mediated inhibition of tumor growth in vivo. Furthermore, we proved that intravitreal injection of ART in Sprague-Dawley (SD) rats is safe, with no obvious retinal function damage or structural disorders observed by electrophysiology (ERG), fundal photographs, fundus fluorescein angiography (FFA) or optical coherence tomography (OCT) examinations. Collectively, our study revealed that ART induces mitochondrial apoptosis of RB cells via upregulating KLF6, and our results may extend the application of ART to the clinic as an effective and safe intravitreal chemotherapeutic drug to treat RB, especially RB with vitreous seeds.

Naturally occurring anti-cancer compounds: shining from Chinese herbal medicine

Numerous natural products originated from Chinese herbal medicine exhibit anti-cancer activities, including anti-proliferative, pro-apoptotic, anti-metastatic, anti-angiogenic effects, as well as regulate autophagy, reverse multidrug resistance, balance immunity, and enhance chemotherapy in vitro and in vivo. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2011) on the key compounds with anti-cancer effects derived from Chinese herbal medicine (curcumin, epigallocatechin gallate, berberine, artemisinin, ginsenoside Rg3, ursolic acid, silibinin, emodin, triptolide, cucurbitacin B, tanshinone I, oridonin, shikonin, gambogic acid, artesunate, wogonin, β-elemene, and cepharanthine) in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we focused on their recently discovered and/or investigated pharmacological effects, novel mechanism of action, relevant clinical studies, and their innovative applications in combined therapy and immunomodulation. In addition, the present review has extended to describe other promising compounds including dihydroartemisinin, ginsenoside Rh2, compound K, cucurbitacins D, E, I, tanshinone IIA and cryptotanshinone in view of their potentials in cancer therapy. Up to now, the evidence about the immunomodulatory effects and clinical trials of natural anti-cancer compounds from Chinese herbal medicine is very limited, and further research is needed to monitor their immunoregulatory effects and explore their mechanisms of action as modulators of immune checkpoints.

Artesunate suppresses inflammation and oxidative stress in a rat model of colorectal cancer

Anti-inflammatory drugs are well known to reduce the risk of colon cancer and prophylactic use of such agents is gaining acceptance as a cancer prevention therapy. As artesunate, an antimalarial drug, has been shown to exhibit chemopreventive properties, the present study was carried out to evaluate its inhibitory effect on oxidative stress and inflammation in a rat model of colon carcinogenesis. A chemical carcinogen, 1,2-dimethylhydrazine was injected twice at an interval of 1 week to induce preneoplastic lesions in the colon and the parameters indicating oxidative stress and inflammation were evaluated after 8 weeks. Artesunate (50 and 150 mg/kg) and aspirin (60 mg/kg) were administered orally throughout the study. Analysis of colon tissue revealed that both the drugs preserved histoarchitecture, inhibited cellular influx, decreased the levels of oxidative stress and inflammatory markers, downregulated cyclooxygenase-2, inducible nitric oxide synthase, nuclear factor κB, and interleukin 1β in comparison to the experimental control. Suppression of oxidative stress and pro-inflammatory signaling by both the drugs were found to contribute to inhibition of colon carcinogenesis. The protection afforded by these drugs was found to be comparable. Our study shows that like aspirin, use of artesunate could also reduce the risk of colon cancer and it has a potential for further evaluation for the treatment purpose.

Novel therapeutic roles of MC-4 in combination with everolimus against advanced renal cell carcinoma by dual targeting of Akt/pyruvate kinase muscle isozyme M2 and mechanistic target of rapamycin complex 1 pathways

Current clinical trials of new anticancer therapies against metastatic renal cell carcinoma (RCC), including molecular-targeted therapies, have not shown promise. The purpose of this study was to preclinically assess the antitumor effects of MC-4, a partially purified material of Artemisia annua L., as a monotherapy or in combination with the known mechanistic target of rapamycin complex 1 (mTORC1) inhibitor, everolimus, against Caki-1 (Von Hippel-Lindau (VHL)+/+) and 786-O (VHL-/-) human RCC cells. MC-4 monotherapy significantly increased tumor growth inhibition and autophagic cell death in RCC cells in vitro and in vivo. Everolimus led to compensatory Akt activation by inhibiting only mTORC1 signaling pathway. In contrast to everolimus, MC-4 enhanced phosphatase and tensin homolog expression and reduced its downstream effector, Akt/pyruvate kinase muscle isozyme M2 (PKM2), leading to decreased expression of glucose transporter 1, which is associated with cancer cell metabolism. The synergistic antitumor and anti-metastatic effects induced by co-administration of MC-4 and everolimus involve cell growth inhibition and autophagic cell death via dual targeting of phosphatidylinositol 3-kinase (PI3K)/Akt/PKM2 and mTORC1. These findings suggest that MC-4 is a novel Akt/PKM2 inhibitor that can overcome the limitation of existing mTOR inhibitors and can be considered a novel strategy to treat patients with rapidly progressing advanced RCC.

Novel natural product therapeutics targeting both inflammation and cancer

Inflammation is recently recognized as one of the hallmarks of human cancer. Chronic inflammatory response plays a critical role in cancer development, progression, metastasis, and resistance to chemotherapy. Conversely, the oncogenic aberrations also generate an inflammatory microenvironment, enabling the development and progression of cancer. The molecular mechanisms of action that are responsible for inflammatory cancer and cancer-associated inflammation are not fully understood due to the complex crosstalk between oncogenic and pro-inflammatory genes. However, molecular mediators that regulate both inflammation and cancer, such as NF-κB and STAT have been considered as promising targets for preventing and treating these diseases. Recent works have further demonstrated an important role of oncogenes (e.g., NFAT1, MDM2) and tumor suppressor genes (e.g., p53) in cancer-related inflammation. Natural products that target these molecular mediators have shown anticancer and anti-inflammatory activities in preclinical and clinical studies. Sesquiterpenoids (STs), a class of novel plant-derived secondary metabolites have attracted great interest in recent years because of their diversity in chemical structures and pharmacological activities. At present, we and other investigators have found that dimeric sesquiterpenoids (DSTs) may exert enhanced activity and binding affinity to molecular targets due to the increased number of alkylating centers and improved conformational flexibility and lipophilicity. Here, we focus our discussion on the activities and mechanisms of action of STs and DSTs in treating inflammation and cancer as well as their structure-activity relationships.

Chemoprevention by artesunate in a preclinical model of colorectal cancer involves down regulation of β-catenin, suppression of angiogenesis, cellular proliferation and induction of apoptosis

Use of anti-inflammatory drugs is well known to decrease the risk of colorectal cancer, one of the most common causes of cancer related mortality. In view of anti-inflammatory property of artesunate reported in various experimental models, the present study was carried out to evaluate its efficacy in rat model where colon carcinogenesis was induced by 1, 2 dimethylhydrazine (DMH). A time course study revealed that two injections of DMH given at an interval of one week resulted in appearance of multiple plaque lesions and aberrant crypt foci in the colon with a peak effect occurring at the end of 8 weeks. An efficacy study carried out with daily oral administration of artesunate (50 and 150 mg/kg) and aspirin (60 mg/kg) showed a marked reduction in pre-neoplastic changes with a significant decrease in the number of aberrant crypt foci, crypt multiplicity and restoration of histoarchitecture. Both the drugs down regulated β-catenin signaling, reduced the levels of angiogenic markers like VEGF, MMP-9 and inhibited cellular proliferation. The anti-cancer effect of these drugs was concomitant with the pro-apoptotic effect as revealed by increased DNA fragmentation, TUNEL positivity and Bax/Bcl₂ immunoreactivity. This is the first study to evaluate the inhibitory effect of artesunate on pre-neoplastic changes in colon where its chemopreventive effect was found to be comparable to that of aspirin. Our study strengthens the previous findings and shows that it has a preventive and therapeutic potential in the treatment of colon cancer.

Drug repurposing in cancer

Cancer is a major health issue worldwide, and the global burden of cancer is expected to increase in the coming years. Whereas the limited success with current therapies has driven huge investments into drug development, the average number of FDA approvals per year has declined since the 1990s. This unmet need for more effective anti-cancer drugs has sparked a growing interest for drug repurposing, i.e. using drugs already approved for other indications to treat cancer. As such, data both from pre-clinical experiments, clinical trials and observational studies have demonstrated anti-tumor efficacy for compounds within a wide range of drug classes other than cancer. Whereas some of them induce cancer cell death or suppress various aspects of cancer cell behavior in established tumors, others may prevent cancer development. Here, we provide an overview of promising candidates for drug repurposing in cancer, as well as studies describing the biological mechanisms underlying their anti-neoplastic effects.

Nrf2 inhibition reverses the resistance of cisplatin-resistant head and neck cancer cells to artesunate-induced ferroptosis

Artesunate, an anti-malarial drug, has been repurposed as an anticancer drug due to its induction of cell death via reactive oxygen species (ROS) production. However, the molecular mechanisms regulating cancer cell death and the resistance of cells to artesunate remain unclear. We investigated the molecular mechanisms behind the antitumor effects of artesunate and an approach to overcome artesunate resistance in head and neck cancer (HNC). The effects of artesunate and trigonelline were tested in different HNC cell lines, including three cisplatin-resistant HNC cell lines. The effects of these drugs as well as the inhibition of Keap1, Nrf2, and HO-1 were assessed by cell viability, cell death, glutathione (GSH) and ROS production, protein expression, and mouse tumor xenograft models. Artesunate selectively killed HNC cells but not normal cells. The artesunate sensitivity was relatively low in cisplatin-resistant HNC cells. Artesunate induced ferroptosis in HNC cells by decreasing cellular GSH levels and increasing lipid ROS levels. This effect was blocked by co-incubation with ferrostatin-1 and a trolox pretreatment. Artesunate activated the Nrf2-antioxidant response element (ARE) pathway in HNC cells, which contributed to ferroptosis resistance. The silencing of Keap1, a negative regulator of Nrf2, decreased artesunate sensitivity in HNC cells. Nrf2 genetic silencing or trigonelline reversed the ferroptosis resistance of Keap1-silenced and cisplatin-resistant HNC cells to artesunate in vitro and in vivo. Nrf2-ARE pathway activation contributes to the artesunate resistance of HNC cells, and inhibition of this pathway abolishes ferroptosis-resistant HNC.

CONDENSED ABSTRACT

Our results show the effectiveness and molecular mechanism of artesunate treatment on head and neck cancer (HNC). Artesunate selectively killed HNC cells but not normal cells by inducing an iron-dependent, ROS-accumulated ferroptosis. However, this effect may be suboptimal in some cisplatin-resistant HNCs because of Nrf2-antioxidant response element (ARE) pathway activation. Inhibition of the Nrf2-ARE pathway increased artesunate sensitivity and reversed the ferroptosis resistance in resistant HNC cells.

Phytomedicine-Modulating oxidative stress and the tumor microenvironment for cancer therapy

In spite of the current advances and achievements in systems biology and translational medicinal research, the current strategies for cancer therapy, such as radiotherapy, targeted therapy, immunotherapy and chemotherapy remain palliative or unsatisfactory due to tumor metastasis or recurrence after surgery/therapy, drug resistance, adverse side effects, and so on. Oxidative stress (OS) plays a critical role in chronic/acute inflammation, carcinogenesis, tumor progression, and tumor invasion/metastasis which is also attributed to the dynamic and complex properties and activities in the tumor microenvironment (TME). Re-educating or reprogramming tumor-associated stromal or immune cells in the TME provides an approach for restoring immune surveillance impaired by disease in cancer patients to increase overall survival and reduce drug resistance. Herbal medicines or plant-derived natural products have historically been a major source of anti-cancer drugs. Delving into the lore of herbal medicine may uncover new leads for anti-cancer drugs. Phytomedicines have been widely documented to directly or indirectly target multiple signaling pathways and networks in cancer cells. A combination of anti-cancer drugs and polypharmacological plant-derived extracts or compounds may offer a significant advantage in sensitizing the efficacy of monotherapy and overcoming drug-induced resistance in cancer patients. This review introduces several phytochemicals and phytoextracts derived from medicinal plants or dietary vegetables that have been studied for their efficacy in preclinical cancer models. We address the underlying modes of action of induction of OS and deregulation of TME-associated stromal cells, mediators and signaling pathways, and reference the related clinical investigations that look at the single or combination use of phytochemicals and phytoextracts to sensitize anti-cancer drug effects and/or overcome drug resistance.

Mefloquine effectively targets gastric cancer cells through phosphatase-dependent inhibition of PI3K/Akt/mTOR signaling pathway

Deregulation of PI3K/Akt/mTOR pathway has been recently identified to play a crucial role in the progress of human gastric cancer. In this study, we show that mefloquine, a FDA-approved anti-malarial drug, effectively targets human gastric cancer cells. Mefloquine potently inhibits proliferation and induces apoptosis of a panel of human gastric cancer cell lines, with EC50 ∼ 0.5-0.7 μM. In two independent gastric cancer xenograft mouse models, mefloquine significantly inhibits growth of both tumors. The combination of mefloquine with paclitaxel enhances the activity of either drug alone in in vitro and in vivo. In addition, mefloquine potently decreased phosphorylation of PI3K, Akt, mTOR and rS6. Overexpression of constitutively active Akt significantly restored mefloquine-mediated inhibition of mTOR phosphorylation and growth, and induction of apoptosis, suggesting that mefloquine acts on gastric cancer cells via suppressing PI3K/Akt/mTOR pathway. We further show that mefloquine-mediated inhibition of Akt/mTOR singaling is phosphatase-dependent as pretreatment with calyculin A does-dependently reversed mefloquine-mediated inhibition of Akt/mTOR phosphorylation. Since mefloquine is already available for clinic use, these results suggest that it is a useful addition to the treatment armamentarium for gastric cancer.