Icariin enhances cytotoxicity of doxorubicin in human multidrug-resistant osteosarcoma cells by inhibition of ABCB1 and down-regulation of the PI3K/Akt pathway

Exploring Synergistic Interactions between Natural Compounds and Conventional Chemotherapeutic Drugs in Preclinical Models of Lung Cancer

In the current work, the synergy between natural compounds and conventional chemotherapeutic drugs is comprehensively reviewed in light of current preclinical research findings. The prognosis for lung cancer patients is poor, with a 5-year survival rate of 18.1%. The use of natural compounds in combination with conventional chemotherapeutic drugs has gained significant attention as a potential novel approach in the treatment of lung cancer. The present work highlights the importance of finding more effective therapies to increase survival rates. Chemotherapy is a primary treatment option for lung cancer but it has limitations such as reduced effectiveness because cancer cells become resistant. Natural compounds isolated from medicinal plants have shown promising anticancer or chemopreventive properties and their synergistic effect has been observed when combined with conventional therapies. The combined use of an anti-cancer drug and a natural compound exhibits synergistic effects, enhancing overall therapeutic actions against cancer cells. In conclusion, this work provides an overview of the latest preclinical research on medicinal plants and plant-derived compounds as alternative or complementary treatment options for lung cancer chemotherapy and discusses the potential of natural compounds in treating lung cancer with minimal side effects.

New emerging targets in osteosarcoma therapy: PTEN and PI3K/Akt crosstalk in carcinogenesis

Osteosarcoma (OS) is a malignant bone carcinoma that affects people in childhood and adulthood. The heterogeneous nature and chromosomal instability represent certain characteristics of OS cells. These cancer cells grow and migrate abnormally, making the prognosis undesirable for patients. Conventional and current treatments fail to completely eradicate tumor cells, so new therapeutics targeting genes may be considered. PI3K/Akt is a regulator of events such as growth, cell death, migration, and differentiation, and its expression changes during cancer progression. PTEN reduces PI3K/Akt expression, and its mutations and depletions have been reported in various tumors. Experimental evidence shows that there is upregulation of PI3K/Akt and downregulation of PTEN in OS. Increasing PTEN expression may suppress PI3K/Akt to minimize tumorigenesis. In addition, PI3K/Akt shows a positive association with growth, metastasis, EMT and metabolism of OS cells and inhibits apoptosis. Importantly, overexpression of PI3K/Akt causes drug resistance and radio-resistance and its level can be modulated by miRNAs, lncRNAs and circRNAs. Silencing PI3K/Akt by compounds and drugs can suppress OS. Here, we review in detail the function of the PTEN/PI3K/Akt in OS, revealing its biological function, function in tumor progression, resistance to therapy, and pharmacological significance.

Unveiling the therapeutic potential of natural-based anticancer compounds inducing non-canonical cell death mechanisms

In the Mid-19th century, Rudolf Virchow considered necrosis to be a prominent form of cell death; since then, pathologists have recognized necrosis as both a cause and a consequence of disease. About a century later, the mechanism of apoptosis, another form of cell death, was discovered, and we now know that this process is regulated by several molecular mechanisms that "programme" the cell to die. However, discoveries on cell death mechanisms are not limited to these, and recent studies have allowed the identification of novel cell death pathways that can be molecularly distinguished from necrotic and apoptotic cell death mechanisms. Moreover, the main goal of current cancer therapy is to discover and develop drugs that target apoptosis. However, resistance to chemotherapeutic agents targeting apoptosis is mainly responsible for the failure of clinical therapy and adverse side effects of the chemotherapeutic agents currently in use pose a major threat to the well-being and lives of patients. Therefore, the development of natural-based anticancer drugs with low cellular and organismal side effects is of great interest. In this comprehensive review, we thoroughly examine and discuss natural anticancer compounds that specifically target non-canonical cell death mechanisms.

Icariin as a potential anticancer agent: a review of its biological effects on various cancers

Numerous chemical compounds used in cancer treatment have been isolated from natural herbs to address the ever-increasing cancer incidence worldwide. Therein is icariin, which has been extensively studied for its therapeutic potential due to its anti-inflammatory, antioxidant, antidepressant, and aphrodisiac properties. However, there is a lack of comprehensive and detailed review of studies on icariin in cancer treatment. Given this, this study reviews and examines the relevant literature on the chemopreventive and therapeutic potentials of icariin in cancer treatment and describes its mechanism of action. The review shows that icariin has the property of inhibiting cancer progression and reversing drug resistance. Therefore, icariin may be a valuable potential agent for the prevention and treatment of various cancers due to its natural origin, safety, and low cost compared to conventional anticancer drugs, while further research on this natural agent is needed.

Natural bioactive compounds-doxorubicin combinations targeting topoisomerase II-alpha: Anticancer efficacy and safety

Cancer is one of the leading causes of death worldwide, so pursuing effective and safe therapeutics for cancer is a key research objective nowadays. Doxorubicin (DOX) is one of the commonly prescribed chemotherapeutic agents that has been used to treat cancer with its antimitotic properties via inhibition of topoisomerase II (TOP2) activity. However, many problems hinder the broad use of DOX in clinical practice, including cardiotoxicity and drug resistance. Research in drug discovery has confirmed that natural bioactive compounds (NBACs) display a wide range of biological activities correlating to anticancer outcomes. The combination of NBACs has been seen to be an ideal candidate that might increase the effectiveness of DOX therapy and decreases its unfavorable adverse consequences. The current review discusses the chemo-modulatory mechanism and the protective effects of combined DOX with NBACs with a binding affinity (pKi) toward TOP2A more than pKi of DOX. This review will also discuss and emphasize the molecular mechanisms to provide a pathway for further studies to reveal other signaling pathways. Taken together, understanding the fundamental mechanisms and implications of combined therapy may provide a practical approach to battling cancer diseases.

Molecular mechanisms regulating the pharmacological actions of icariin with special focus on PI3K-AKT and Nrf-2 signaling pathways

Icariin is a primary active component of the traditional Chinese medicinal plant Epimedium grandiflorum. A range of pharmacological effects of icariin has been researched by modern science to explain its traditional medicinal uses. Attributing to the wide range of pharmacological properties like anti-osteoporosis, anti-inflammation, anti-oxidative stress, anti-depression, and anti-tumor property possessed by icariin, it is now being considered a potential therapeutic agent for a wide variety of disorders ranging from neoplasm, neurodegenerative disorders, osteoporosis, and cardiovascular diseases. Various signaling pathways including NFκB/NALP3, IGF-1, MiR-223-3p/ NALP3, TLR4/ NFκB, and WNT1/β-catenin are involved in the different biological actions exerted by icariin. Apart from these pathways, PI3K-AKT (Phosphoinositide 3 kinase-Protein kinase B) and Nrf-2 (nuclear erythroid 2-related factor 2) signaling pathways are two important pathways that form the fundamental basis for the pharmaceutical efficacy of icariin. This review gives an overview of previous in vitro and in vivo studies that investigated the potential role of icariin via PI3K-AKT and Nrf-2 signaling pathways to provide greater insights into its potential clinical use in a variety of disorders.

Icariin Regulates the hsa_circ_0003159/eIF4A3/bcl-2 Axis to Promote Gastric Cancer Cell Apoptosis

Objective

To clarify the mechanism of icariin (ICA) promoting gastric cancer (GC) cell apoptosis by regulating circ_0003159/eIF4A3/bcl-2 axis.

Methods

The mRNA or protein levels were detected by qRT-PCR or the western blot. The interaction between eIF4A3 protein and circ_0003159 or eIF4A3 protein and bcl-2 mRNA were validated by RNA pull down assays and the RNA immunoprecipitation (RIP) assay. The cell viability was measured by the cell counting kit (CCK)-8 kit. The cell apoptosis was measured by flow cytometry.

Results

Compared with the group Vector, the ratio of cytoplasmic eIF4A3/nuclear eIF4A3 in the cell with circ_0003159 overexpression was significantly higher. RIP and RNA pull down results proved the interaction between eIF4A3 and circ_0003159. The RIP assay further validated the interaction between eIF4A3 and bcl-2. By gain or loss of the functional experiment, hsa_circ_0003159 was proved to recruit eIF4A3 to inhibit bcl-2 expression. Hsa_circ_0003159 regulates eIF4A3/bcl-2 to reduce GC cell viability and increase apoptosis Furthermore, ICA regulates hsa_circ_0003159/eIF4A3/bcl-2 axis to inhibit GC cell activity and induce GC cell apoptosis in vitro.

Conclusion

These data showed that ICA could effectively reduce the GC cell activity and induce GC cell apoptosis via hsa_circ_0003159/eIF4A3/bcl-2 axis, which provides new theoretical evidence for the treatment of GC by ICA.

Cancer multidrug-resistance reversal by ABCB1 inhibition: A recent update

Chemotherapy is one of the most common treatments for cancer that uses one or more anti-cancer drugs as a part of the standardized chemotherapy regimen. Cytotoxic chemicals delay and prevent cancer cells from multiplying, invading, and metastasizing. However, the significant drawbacks of cancer chemotherapy are the lack of selectivity of the cytotoxic drugs to tumour cells and normal cells and the development of resistance by cells for the particular drug or the combination of drugs. Multidrug resistance (MDR) is the low sensitivity of specific cells against drugs associated with cancer chemotherapy. The most common mechanisms of anticancer drug resistance are: (a) drug-dependent MDR (b) target-dependent MDR, and (c) drug target-independent MDR. In all the factors, the overexpression of multidrug efflux systems contributes significantly to the increased resistance in the cancer cells. Multidrug resistance due to efflux of anticancer drugs by membrane ABC transporters includes ABCB1, ABCC1, and ABCG2. ABCB1 inhibition can restore the sensitivity of the cancerous cells toward chemotherapeutic drugs. In this review, we discussed ABCB1 inhibitors under clinical studies with their mode of action, potency and selectivity. Also, we have highlighted the contribution of repurposing drugs, biologics and nano formulation strategies to combat multidrug resistance by modulating the ABCB1 activity.

Metformin and Thymoquinone Synergistically Inhibit Proliferation of Imatinib-Resistant Human Leukemic Cells

Chemotherapy resistance is one of the major challenges in cancer treatment, including leukemia. A massive array of research is evaluating combinations of drugs directed against different intracellular signaling molecules to overcome cancer resistance, increase therapy effectiveness, and decrease its adverse effects. Combining chemicals with proven safety profiles, such as drugs already used in therapy and active substances isolated from natural sources, could potentially have superior effects compared to monotherapies. In this study, we evaluated the effects of metformin and thymoquinone (TQ) as monotherapy and combinatorial treatments in chronic myeloid leukemia (CML) cell lines sensitive and resistant to imatinib therapy. The effects were also evaluated in primary monocytic acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL) cells. Both compounds induced a dose- and time-dependent decrease of viability and proliferation in tested cells. Metformin had similar IC₅₀ values in imatinib-sensitive and imatinib-resistant cell lines. IC₅₀ values of TQ were significantly higher in imatinib-resistant cells, but with a limited resistance index (2.4). Synergistic effects of combinatorial treatments were observed in all tested cell lines, as well as in primary cells. The strongest synergistic effects were observed in the inhibition of imatinib-resistant cell line proliferation. Metformin and TQ inhibited the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling and induced apoptosis in tested cell lines and primary cells. The enhanced effects of combinatorial treatments on the induction of apoptosis were more dominant in imatinib-resistant compared to imatinib-sensitive CML cells. Primary cells were more sensitive to combinatorial treatments compared to cell lines. A combination of 1.25 mM metformin and 0.625 µM TQ increased the levels of cleaved poly (ADP-ribose) polymerase (PARP), decreased the levels of proliferation regulatory proteins, and inhibited protein kinase B (Akt) and NF-κB signaling in primary CLL cells. This study demonstrates that combinatorial treatments of imatinib-resistant malignant clones with metformin and TQ by complementary intracellular multi-targeting represents a promising approach in future studies.

Molecular signaling pathways as potential therapeutic targets in osteosarcoma

Among primary bone malignancies, osteosarcoma (OS) is the most common form causing morbidity and mortality in both adults and children. The interesting point about this malignancy is that nearly 10-20% of its newly diagnosed cases have developed metastasis. This adds up to the fact that the survival rate of both metastatic and non-metastatic patients of osteosarcoma hasn't changed in the past 30 years and suggests that we need to revise our therapeutic options for OS. In recent years, diverse signaling pathways have drawn the attention of the scientific community since they can be great candidates for treating complicated diseases such as cancer. In this review, we have tried to explain the pathophysiology of osteosarcoma by the help of different signaling pathways taking part in its initiation/progression and investigate how this pathway can be targeted for providing more efficient methods.

Salidroside Promotes Sensitization to Doxorubicin in Human Cancer Cells by Affecting the PI3K/Akt/HIF Signal Pathway and Inhibiting the Expression of Tumor-Resistance-Related Proteins

Salidroside (Sal), the major active constituent of Rhodiola rosea L., is considered as a potential pro-drug with various activities; however, its role in tumor therapy is not clear. Here, we demonstrated in vitro and in vivo that Sal enhanced the inhibitory activity of doxorubicin (DOX) in drug-resistant cancer cell lines. Our results showed that combination drug treatment (Sal and DOX) significantly decreased cell proliferation, migration, and motility. Besides biological validation, a luciferase-labeled animal tumor xenograft model and bioluminescence imaging (BLI) were applied for assessing the tumor progression. Sal combined with DOX inhibited the growth of HeLa-ADR-luc cells in vivo and downregulated the DOX-induced high expression of MDR1. Also, Sal downregulated the Bcl-2, MMP-2, MMP-9, PI3K, and AKT and upregulated BAX proteins. Sal demonstrated high safety and cardiac protection activity. We discovered that Sal enhances DOX sensitivity through the regulation of PI3K/Akt/HIF-1α and DOX-induced resistance pathways. Our results suggest that Sal could be a novel chemosensitization agent for the treatment of multi-drug-resistance tumors.

Icariin inhibits gastric cancer cell growth by regulating the hsa_circ_0003159/miR-223-3p/NLRP3 signaling axis

This study aimed to clarify the expression and role of hsa_circ_0003159 in gastric carcinogenesis, and validate the protective effects of Icariin (ICA) against gastric cancer (GC) cell growth through the in vitro and in vivo experiments. The levels of hsa_circ_0003159, microRNA (miR)-223-3p and NLRP3 were measured by Quantitative real time Polymerase Chain Reaction or western blot. The cell counting kit (CCK)-8 was used to determine cell proliferation. The target relationship of miR-223-3p/hsa_circ_0003159 and miR-223-3p/NLRP3 was predicted by bioinformatics and validated by the dual-luciferase reporter and pull-down assays. Xenograft model was constructed to assess the roles of hsa_circ_0003159 and protective effects of ICA in GC in vivo. Results showed that hsa_circ_0003159 was downregulated in GC cell lines and its overexpression promoted GC cell viability. MiR-223-3p was identified as a target of hsa_circ_0003159. By competitively sponging miR-223-3p, hsa_circ_0003159 positively regulated NLRP3 expression. MiR-223-3p mimics reversed the suppressive effect of hsa_circ_0003159 on GC cell viability and cell pyroptosis. Importantly, ICA inhibited GC cell viability and triggered GC cell pyroptosis by regulating the hsa_circ_0003159/miR-223-3p/NLRP3 axis in vitro and in vivo. In conclusion, this study indicated ICA inhibits GC cell growth by regulating the hsa_circ_0003159/miR-223-3p/NLRP3 signaling axis. This study not only reveals the mechanism of gastric carcinogenesis but also provides potential molecular targets and therapeutic tools for its treatment.

Function of selected natural antidiabetic compounds with potential against cancer via modulation of the PI3K/AKT/mTOR cascade

Diabetes mellitus (DM) is a metabolic disorder with growing global incidence, as 387 million people were diagnosed in 2014 with an expected projection of 642 million in 2040. Several complications are associated with DM including heart attack, stroke, kidney failure, blindness, and cancer. The latter is the second leading cause of death worldwide accounting for one in every six deaths, with liver, pancreas, and endometrium cancers are the most abundant among patients with diabetes. Phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway plays a vital role in developing a wide array of pathological disorders, among them diabetes and cancer. Natural secondary metabolites that counteract the deleterious effects of reactive oxygen species (ROS) and modulate PI3K/Akt/mTOR pathway could be a promising approach in cancer therapy. Here, 717 medicinal plants with antidiabetic activities were highlighted along with 357 bioactive compounds responsible for the antidiabetic activity. Also, 43 individual plant compounds with potential antidiabetic activities against cancer via the modulation of PI3K/Akt/mTOR cascade were identified. Taken together, the available data give an insight of the potential of repurposing medicinal plants and/or the individual secondary metabolites with antidiabetic activities for cancer therapy.

Isolation, characterization and in vitro cytotoxicity studies of bioactive compounds from Alseodaphne semecarpifolia Nees

Alseodaphne semecarpifolia (Lauraceae) is a traditional medicinal plant historically used in Indian Western Ghats to treat various human diseases. From the past few decades it has been traditionally recognized as an effective agent in cancer treatment. The phytochemical investigation of the stem bark and leaves of A. semecarpifolia led to the isolation of bioactive flavonoid compounds Icariin and Baicalein. Their structures were elucidated from obtained spectral data (¹H NMR, ¹³C NMR, ¹H ¹H COSY, FTIR and MS). Cytotoxic activity of Icariin and Baicalein evaluated against MCF-7 cells revealed their potent activity with an IC₅₀ of 42.15 ± 4.78 μg/ml and 44.37 ± 3.46 μg/ml, respectively, while very least effect was observed on normal cells (L6). Present study has suggested that both Icariin and Baicalein have potent cytotoxic activity against MCF-7 cells.

MicroRNA-221 Upregulates the Expression of P-gp and Bcl-2 by Activating the Stat3 Pathway to Promote Doxorubicin Resistance in Osteosarcoma Cells

MicroRNA-221 (miRNA-221) is upregulated in several malignant tumors and is associated with poor patient prognosis. Therefore, the present study aimed to investigate the role and underlying mechanism of miRNA-221 in doxorubicin (DOX) resistance in osteosarcoma cells. We constructed DOX-resistant Saos-2/DOX cells and treated them with DOX. Cell viability was determined by performing a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cells were transfected with either miRNA-221 mimic or miRNA-221 inhibitor; quantitative (q)RT-PCR was performed to detect the expression of miRNA-221. Flow cytometry and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling (TUNEL) staining were used to detect cell apoptosis. The immunofluorescence method was also used to detect cell signal transduction and activator of transcription 3 (Stat3) protein expression distribution. In addition, Western blotting was used to detect changes in the expression of each protein. We found that miRNA-221 was upregulated in Saos-2/DOX cells. Moreover, the miRNA-221 mimic induced DOX resistance in Saos-2 cells, whereas the miRNA-221 inhibitor enhanced DOX sensitivity in Saos-2/DOX cells. The miRNA-221 mimic upregulated the expression of phosphorylated-Stat3, P-glycoprotein (P-gp), and B-cell lymphoma-2 (Bcl-2) proteins in Saos-2 cells and induced the entry of Stat3 into the nucleus, whereas the miRNA-221 inhibitor exerted the opposite effect. Pretreatment with the Stat3 chemical inhibitor, STAT3-IN-3, significantly inhibited the upregulation of P-gp and Bcl-2 protein expression induced by the miRNA-221 mimic in Saos-2 cells; it also caused the Saos-2 cells to overcome DOX resistance induced by the miRNA-221 mimic. Thus, miRNA-221 increased the expression of P-gp and Bcl-2 by activating the Stat3 pathway to promote DOX resistance in osteosarcoma cells, indicating a potential use of miRNA-221 in osteosarcoma treatment.

Poncirin downregulates ATP-binding cassette transporters to enhance cisplatin sensitivity in cisplatin-resistant osteosarcoma cells

Poncirin, a flavanone glycoside with bitter taste extracted from dried immature fruit of Poncirus trifoliate, exhibits multiple biological activities including anti-tumor activity. Our study aimed to determine the effect and potential mechanism of poncirin on cisplatin resistance in osteosarcoma (OS) cells. CCK-8, flow cytometry analysis, and caspase-3/7 activity assays were used to evaluate cisplatin sensitivity. The expression changes of multidrug resistance 1 (MDR1), multidrug resistance-associated protein (MRP1), breast cancer resistance protein (BCRP), and phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) pathway-related proteins were detected by RT-qPCR or western blot analyses. Results showed that poncirin exposure enhanced cisplatin sensitivity, promoted apoptosis, and increased caspase-3/7 activity in cisplatin-resistant OS cells. Poncirin decreased the expression levels of MDR1, MRP1, and BCRP, and inhibited the PI3K/Akt signaling in OS cells. Rescue experiments suggested that activation of the PI3K/Akt signaling by 740Y-P abolished poncirin-induced expression reduction of MDR1, MRP1, and BCRP, and attenuated the facilitative effects of poncirin on cisplatin sensitivity and apoptosis in cisplatin-resistant OS cells. In summary, poncirin suppressed cisplatin resistance in cisplatin-resistant OS cells by downregulating the expression of MDR1, MRP1, and BCRP through inhibiting the PI3K/Akt pathway.

Prenylflavonoid Icariin Induces Estrogen Response Element-Independent Estrogenic Responses in a Tissue-Selective Manner

Icariin, a flavonoid phytoestrogen derived from Herba epimedii, has been reported to exert estrogenic effects in bone and activate phosphorylation of estrogen receptor (ER) α in osteoblastic cells. However, it is unclear whether icariin selectively exerts estrogenic activities in bone without inducing undesirable effects in other estrogen-sensitive tissues. The present study aimed to investigate the tissue-selective estrogenic activities of icariin in estrogen-sensitive tissues in vivo and in vitro. Long-term treatment with icariin effectively prevented bone of ovariectomized (OVX) rats from estrogen deficiency–induced osteoporotic changes in bone structure, bone mineral density, and trabecular properties. Moreover, icariin regulated the transcriptional events of estrogen-responsive genes related to bone remodeling and prevented dopaminergic neurons against OVX-induced changes by rescuing expression of estrogen-regulated tyrosine hydroxylase and dopamine transporter in the striatum. Unlike estrogen, icariin did not induce estrogenic effects in the uterus and breast in mature OVX rats or immature CD-1 mice. In vitro studies demonstrated that icariin exerted estrogen-like activities and regulated the expression of estrogen-responsive genes but did not induce estrogen response element–dependent luciferase activities in ER-positive cells. Our results support the hypothesis that icariin, through its distinct mechanism of actions in activating ER, selectively exerts estrogenic activities in different tissues and cell types.

Icariin protects human nucleus pulposus cells from hydrogen peroxide-induced mitochondria-mediated apoptosis by activating nuclear factor erythroid 2-related factor 2

Intervertebral disc degeneration (IVDD) is a well-known cause of lower back pain. Icariin has been shown to exert a protective effect on human nucleus pulposus (NP) cells and accordingly has implications for the prevention and treatment of IVDD; however, the molecular mechanisms underlying its action are not fully established. In this study, the mechanisms underlying its protection against hydrogen peroxide (H₂O₂)-induced oxidative stress injury were investigated. In vitro, we demonstrated that icariin inhibits H₂O₂-induced mitochondria-mediated apoptosis. It upregulates oxidative stress mediators, i.e., reactive oxygen species, and downregulates mitochondrial membrane potential. Nuclear factor erythroid 2-related factor 2 (Nrf-2) is a key factor involved in the regulation of the endogenous defense system. It was proved that icariin could activate the Nrf-2 signaling pathway, upregulate the protein expression of nuclear respiratory factor-1 and the mitochondrial transcription factor, promoting mitochondrial biogenesis in human NP cells. An Nrf-2 agonist and inhibitor promoted or partly abolished the protective effects of icariin on mitochondrial homeostasis. Moreover, it was demonstrated that the Nrf-2 signaling pathway could be inhibited by the phosphatidylinositol 3-Kinase/AKT pathway. In vivo, icariin ameliorated IVDD in a rat model by promoting Nrf-2 activity, and preserving extracellular matrix in NP cells. These data suggest that icariin could ameliorate IVDD in rat models in vivo. In summary, the protective effects of icariin on human NP cells may suppress the pathogenesis of IVDD via the Nrf-2 signaling pathway. Our findings suggest that the Nrf-2 signaling pathway is a novel therapeutic target for the treatment of IVDD.

Tackling drug resistance with efflux pump inhibitors: from bacteria to cancerous cells

Drug resistance is a serious concern in a clinical setting jeopardizing treatment for both infectious agents and cancers alike. The wide-spread emergence of multi-drug resistant (MDR) phenotypes from bacteria to cancerous cells necessitates the need to target resistance mechanisms and prevent the emergence of resistant mutants. Drug efflux seems to be one of the preferred approaches embraced by both microbial and mammalian cells alike, to thwart the action of chemotherapeutic agents thereby leading to a drug resistant phenotype. Relative to microbes, which predominantly employs proton motive force (PMF) powered, Major Facilitator Superfamily (MFS)/Resistance Nodulation and Division (RND) classes of efflux pumps to efflux drugs, cancerous cells preferentially use ATP fuelled ATP binding cassette (ABC) transporters to extrude chemotherapeutic agents. The prevalence, evolutionary characteristics and overlapping functions of ABC transporters have been highlighted in this review. Additionally, we outline the role of ABC pumps in conferring MDR phenotype to both bacteria and cancerous cells and underscore the importance of efflux pump inhibitors (EPI) to mitigate drug resistance. Based on the literature reports and analysis, we reason out feasibility of employing bacteria as a tool to screen for EPI's targeting ABC pumps of cancerous cells.

Oestrogen-related receptor alpha mediates chemotherapy resistance of osteosarcoma cells via regulation of ABCB1

Chemotherapy resistance is one of the major challenges for the treatment of osteosarcoma (OS). The potential roles of oestrogenic signals in the chemoresistance of OS cells were investigated. As compare to the parental cells, the doxorubicin and cisplatin (CDDP) resistant OS cells had greater levels of oestrogen-related receptors alpha (ERRα). Targeted inhibition of ERRα by its specific siRNAs or inverse agonist XCT-790 can restore the sensitivity of OS resistant cells to chemotherapy. This might be due to that si-ERRα can decrease the expression of P-glycoprotein (P-gp, encoded by ABCB1), one important ABC membrane transporter for drug efflux. XCT-790 can decrease the transcription and mRNA stability of ABCB1, while had no effect on protein stability of P-gp. ERRα can bind to the transcription factor of SP3 to increase the transcription of ABCB1. Furthermore, XCT-790 treatment decreased the expression of miR-9, which can bind to the 3'UTR of ABCB1 and trigger its decay. Collectively, we found that ERRα can regulate the chemoresistance of OS cells via regulating the transcription and mRNA stability of ABCB1. Targeted inhibition of ERRα might be a potential approach for OS therapy.

DOX-Vit D, a Novel Doxorubicin Delivery Approach, Inhibits Human Osteosarcoma Cell Proliferation by Inducing Apoptosis While Inhibiting Akt and mTOR Signaling Pathways

Doxorubicin (DOX) is a very potent and effective anticancer agent. However, the effectiveness of DOX in osteosarcoma is usually limited by the acquired drug resistance. Recently, Vitamin D (Vit-D) was shown to suppress the growth of many human cancer cells. Taken together, we synthesized DOX-Vit D by conjugating Vit-D to DOX in order to increase the delivery of DOX into cancer cells and mitigate the chemoresistance associated with DOX. For this purpose, MG63 cells were treated with 10 µM DOX or DOX-Vit D for 24 h. Thereafter, MTT, real-time PCR and western blot analysis were used to determine cell proliferation, genes and proteins expression, respectively. Our results showed that DOX-Vit D, but not DOX, significantly elicited an apoptotic signal in MG63 cells as evidenced by induction of death receptor, Caspase-3 and BCLxs genes. Mechanistically, the DOX-Vit D-induced apoptogens were credited to the activation of p-JNK and p-p38 signaling pathway and the inhibition of proliferative proteins, p-Akt and p-mTOR. Our findings propose that DOX-Vit D suppressed the growth of MG63 cells by inducing apoptosis while inhibiting cell survival and proliferative signaling pathways. DOX-Vit D may serve as a novel drug delivery approach to potentiate the delivery of DOX into cancer cells.

Icariin reduces human colon carcinoma cell growth and metastasis by enhancing p53 activities

Icariin has been reported to possess high anticancer activity. Colon carcinoma is one of the leading causes of cancer-related mortality worldwide. Here, the anticancer activity of icariin against HCT116 colon carcinoma cells and the possible underlying mechanism were studied. The trypan blue staining assay, wound healing assay, clonogenic assay, CCK-8 assay, and Annexin V-FITC/PI double staining method were carried out to determine the changes of HCT116 cell growth and migration. mRNA and protein expressions were determined by quantitative real-time PCR and western blot, respectively. Moreover, small interfering RNA (siRNA) plasmid was used to examine the role of p53 in icariin-induced apoptosis in HCT116 cells. Icariin significantly suppressed colon carcinoma HCT116 cells by decreasing migration and viability, and simultaneously promoting apoptosis. Icariin exerted the anti-tumor effect in a dose-dependent manner by up-regulating p53. During treatment of icariin, p-p53, p21, and Bax levels increased, and Bcl-2 level decreased. Short time treatment with icariin induced DNA damage in HCT116 cells. Furthermore, the cytotoxicity of icariin was decreased after p53 knockdown or by using caspase inhibitors. p53 was involved in activities of caspase-9 and caspase-3. Icariin repressed colon carcinoma cell line HCT116 by enhancing p53 expression and activating p53 functions possibly through Bcl-2/Bax imbalance and caspase-9 and -3 regulation. Icariin treatment also induced DNA damage in HCT116 cells.

Reversal of multidrug resistance by icaritin in doxorubicin-resistant human osteosarcoma cells

Multidrug resistance (MDR) is one of the major obstacles in cancer chemotherapy. Our previous study has shown that icariin could reverse MDR in MG-63 doxorubicin-resistant (MG-63/DOX) cells. It is reported that icariin is usually metabolized to icariside II and icaritin. Herein, we investigated the effects of icariin, icariside II, and icaritin (ICT) on reversing MDR in MG-63/DOX cells. Among these compounds, ICT exhibited strongest effect and showed no obvious cytotoxicity effect on both MG-63 and MG-63/DOX cells ranging from 1 to 10 μmol·L^-1. Furthermore, ICT increased accumulation of rhodamine 123 and 6-carboxyfluorescein diacetate and enhanced DOX-induced apoptosis in MG-63/DOX cells in a dose-dependent manner. Further studies demonstrated that ICT decreased the mRNA and protein levels of multidrug resistance protein 1 (MDR1) and multidrug resistance-associated protein 1 (MRP1). We also verified that blockade of STAT3 phosphorylation was involved in the reversal effect of multidrug resistance in MG-63/DOX cells. Taken together, these results indicated that ICT may be a potential candidate in chemotherapy for osteosarcoma.

Solanine reverses multidrug resistance in human myelogenous leukemia K562/ADM cells by downregulating MRP1 expression

Multidrug resistance (MDR) in leukemia cells is a major obstacle to chemotherapeutic treatment. High expression and constitutive activation of multidrug resistance protein 1 (MRP1) has been associated with the development of resistance to anticancer drugs in a number of tumor types. The activity of c-Jun N-terminal kinase 1 (JNK1) is associated with the occurrence of MDR and MRP1 expression. The present study aimed to investigate the ability of solanine to resensitize the Adriamycin^® (ADR)-resistant human myelogenous leukemia cell line K562/ADM to ADR. Results of the Cell Counting Kit-8 assay demonstrated that solanine inhibited K562/ADM cell proliferation. K562/ADM cell sensitivity to ADR was increased following treatment with solanine, indicated by increased intracellular accumulation of ADR. Western blotting demonstrated that treatment with solanine led to reduced MRP1 protein expression, suggesting that solanine-induced ADR accumulation is due to the downregulation of MRP1 expression. Solanine-mediated MRP1 downregulation was observed to be dependent on the JNK signaling pathway. In conclusion, the results of the present study suggest that solanine reverses MDR in K562/ADM cells and may represent a novel therapeutic agent for the treatment of human myelogenous leukemia.

Icaritin induces ovarian cancer cell apoptosis through activation of p53 and inhibition of Akt/mTOR pathway

AIMS

Ovarian cancer (OC) has the highest mortality rate of all gynecological cancers. Currently, the first-line OC treatment consists of cytoreductive surgery and platinum-based chemotherapy. However, most patients develop chemoresistance after the first-line treatment limits the success of treatment. Therefore, there is an urgent need to identify effective therapeutic agents.

MAIN METHODS

Cell viabilities were detected by MTS assay; Annexin V-FITC/PI assay and western blotting assay were performed to analyze the apoptotic cells in vitro; An immunofluorescence assay was performed to analyze the TUNEL⁺ apoptotic cells in vivo; Patient-derived xenografts were established to test the in vivo antitumor effects; The key proteins of p53, caspase-mediated apoptotic pathway and Akt/mTOR pathway were detected by Western blotting.

KEY FINDINGS

Icaritin, a prenylflavonoid derivative from Epimedium Genus, inhibited the proliferation of drug-sensitive OC cells (OV2008 and C13*) and cisplatin resistant OC cells A2780cp. Icaritin induced OC cell apoptosis in vitro, as indicated by the increase of Annexin V⁺/PI⁺ apoptotic cells analyzed with flow cytometry, and the cleavage of caspase 9, caspase 3 and poly-ADP-ribose polymerase (PARP) detected with western blotting. Icaritin also inhibited tumor growth and induced OC cells apoptosis in patient-derived xenografts, as indicated by the tumor growth delay and increase of TUNEL-positive cells in tumor tissues. The icaritin-induced OC cell apoptosis may be associated with the activation of p53 and the suppression of Akt/mTOR pathway.

SIGNIFICANCE

This study sheds light on the underlying mechanisms of antitumor effect of icaritin, and warrants clinical trial for treatment of OC.

Interference of P-REX2a may inhibit proliferation and reverse the resistance of SGC7901 cells to doxorubicin

Drug resistance inhibits the efficacy of doxorubicin in gastric cancer. Phosphatidylinositol 3,4,5-trisphosphate RAC exchanger 2a (P-REX2a) activates the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway by binding to and inactivating phosphatase and tensin homolog (PTEN), which functions as a tumor promoter in a number of types of cancer. However, there is no research concerning the association between P-REX2a expression and drug resistance in gastric cancer. In the present study, the expression of P-REX2a in clinical gastric cancer tissues was detected, and the mechanism of doxorubicin resistance in the gastric cancer cell line SGC7901 was investigated. Using reverse transcription-quantitative polymerase chain reaction and western blotting, it was demonstrated that the mRNA and protein expression of P-REX2a was increased in gastric cancer tissues. MTT assays were also used to determine proliferation, and proliferation was revealed to be reduced following transfection of P-REX2a small interfering (si)RNA. When the cells were treated with 0.3 µM doxorubicin for 24 h, the rate of apoptosis in the siRNA-transfected groups significantly increased and no marked changes in of PTEN and Akt expression were observed. By contrast, the activity of PTEN increased, and the expression of p-Akt (S473) decreased in the P-REX2a siRNA-transfected group compared with the control. The detection of PTEN enzymatic activity in the present study was based on phosphatidylinositol-3,4,5-trisphosphate. Therefore, it was concluded that P-REX2a may participate in the generation of resistance to doxorubicin in gastric cancer, and this may be associated with the upregulation of the PI3K/Akt signaling pathway via inactivation of PTEN.

Icariin Prevents IL-1β-Induced Apoptosis in Human Nucleus Pulposus via the PI3K/AKT Pathway

Purpose

To explore the effect and possible mechanism of icariin, a prenylated flavonol glycoside derived from the Chinese herb Epimedium sagittatum that was applied to IL-1β pretreated human nucleus pulposus (NP) cells.

Methods

Human NP cells were isolated from intervertebral discs of patients with scoliosis and lumbar spondylolisthesis. The cells were divided into five groups: A (blank control); B (20 ng/ml IL-1β); C (20 ng/ml IL-1β + 20 μM icariin); D (20 μM icariin + 20 ng/ml IL-1β + 25 μM LY294002); E (20 ng/ml IL-1β + 25 μM LY294002). For each of the five groups, the CCK8, apoptosis rates, ROS rates, and JC-1 rates were determined and an electron micrograph was performed. Different expression levels of apoptosis proteins and proteins in the PI3K/AKT pathway were detected via western blot.

Results

We found that the damage effects on human nucleus pulposus cells from 20 ng/ml of IL-1β exposure were attenuated by icariin. When the PI3K/AKT pathway was blocked by LY294002, a specific inhibitor of this pathway, the protective effect of icariin was impaired. In summary, icariin might be a protective traditional Chinese medicine, which prevents inflammation-induced degeneration of intervertebral discs partly through the PI3K/AKT pathway.

Pleiotrophin promotes chemoresistance to doxorubicin in osteosarcoma by upregulating P-glycoprotein

Chemoresistance is a major hindrance to successful treatment of osteosarcoma (OS). Pleiotrophin (PTN), a neurotrophic growth factor, has been linked to the malignant characteristics of various cancer types. We retrospectively examined the correlation between PTN expression and chemoresistance in OS in a cohort of 133 OS patients. Immunohistochemistry revealed that PTN expression correlated with the necrosis rate and local OS recurrence. In a prognostic analysis, high PTN expression was associated with poor overall and disease-free survival, and was an independent adverse prognostic factor for disease-free survival. In doxorubicin-treated OS cells, PTN knockdown enhanced cellular chemosensitivity, increased the apoptosis rate and inhibited clone formation, while PTN overexpression had the opposite effects. In a xenograft model, PTN knockdown and overexpression respectively enhanced and reduced cellular sensitivity to doxorubicin. PTN upregulated anaplastic lymphoma kinase (ALK), p-Glycogen Synthase Kinase (GSK)3β, β-catenin and multidrug resistance protein 1/P-glycoprotein (MDR1/P-gp). In rescue assays with the β-catenin inhibitor XAV939 and the MDR1/P-gp inhibitor verapamil, PTN promoted chemoresistance to doxorubicin in OS cells by activating ALK/GSK3β/β-catenin signaling, thereby upregulating MDR1/P-gp. Therefore, PTN could be used as a biomarker predicting chemotherapeutic responses, and downregulating PTN could be a promising therapeutic strategy to prevent chemoresistance in OS patients.

Icarisid II inhibits the proliferation of human osteosarcoma cells by inducing apoptosis and cell cycle arrest

Icarisid II, one of the main active components of Herba Epimedii extracts, shows potent antitumor activity in various cancer cell lines, including osteosarcoma cells. However, the anticancer mechanism of icarisid II against osteosarcoma U2OS needs further exploration. This study aims to investigate further antitumor effects of icarisid II on human osteosarcoma cells and elucidate the underlying mechanism. We cultivated human osteosarcoma USO2 cells in vitro using different concentrations of icarisid II (0-30 µM). Cell viability was detected at 24, 48, and 72 h using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis. Cell cycle was tested by flow cytometry after treatment with icarisid II for 48 h. Annexin V-allophycocyanin and 7-aminoactinomycin D staining were conducted to detect cell apoptosis. Quantitative real-time polymerase chain reaction and Western blot assay were performed to measure the levels of genes and proteins related to cell cycle and apoptosis. Results showed that icarisid II significantly inhibited the proliferation and induced apoptosis of human osteosarcoma U2OS cells. The half maximal inhibitory concentration values were 14.44, 11.02, and 7.37 µM at 24, 48, and 72 h, respectively. Cell cycle was arrested in the G2/M phase in vitro. In addition, icarisid II upregulated the expression levels of P21 and CyclinB1 whereas downregulated the expression levels of CyclinD1, CDC2, and P-Cdc25C, which were related to cell cycle arrest in U2OS cells. The cell apoptotic rate increased in a dose-dependent manner after treatment with icarisid II for 48 h. Icarisid II induced apoptosis by upregulating Bax, downregulating Bcl-2, and activating apoptosis-related proteins, including cleaved caspase-3, caspase-7, caspase-9, and poly (ADP-ribose) polymerase. These data indicate that icarisid II exhibits an antiproliferation effect on human osteosarcoma cells and induces apoptosis by activating the caspase family in a time- and dose-dependent manner in vitro. Therefore, icarisid II may be used as a candidate agent for the clinical treatment of osteosarcoma in the future.

Icariin Prevents H2O2-Induced Apoptosis via the PI3K/Akt Pathway in Rat Nucleus Pulposus Intervertebral Disc Cells

Icariin is a prenylated flavonol glycoside derived from the Chinese herb Epimedium sagittatum. This study investigated the mechanism by which icariin prevents H₂O₂-induced apoptosis in rat nucleus pulposus (NP) cells. NP cells were isolated from the rat intervertebral disc and they were divided into five groups after 3 passages: (A) blank control; (B) 200 μM H₂O₂; (C) 200 μM H₂O₂ + 20 μM icariin; (D) 20 μM icariin + 200 μM H₂O₂ + 25 μM LY294002; (E) 200 μM H₂O₂ + 25 μM LY294002. LY294002 is a selective inhibitor of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. NP cell viability, apoptosis rate, intracellular reactive oxygen species levels, and the expression of AKT, p-AKT, p53, Bcl-2, Bax, caspase-3 were estimated. The results show that, compared with the control group, H₂O₂ significantly increased NP cell apoptosis and the level of intracellular ROS. Icariin pretreatment significantly decreased H₂O₂-induced apoptosis and intracellular ROS and upregulated p-Akt and BCL-2 and downregulated caspase-3 and Bax. LY294002 abolished the protective effects of icariin. Our results show that icariin can attenuate H2O2-induced apoptosis in rat nucleus pulposus cells and PI3K/AKT pathway is at least partly included in this protection effect.

The Anticancer Properties of Herba Epimedii and Its Main Bioactive Componentsicariin and Icariside II

Cancer is one of the leading causes of deaths worldwide. Compounds derived from traditional Chinese medicines have been an important source of anticancer drugs and adjuvant agents to potentiate the efficacy of chemotherapeutic drugs and improve the side effects of chemotherapy. HerbaEpimedii is one of most popular herbs used in China traditionally for the treatment of multiple diseases, including osteoporosis, sexual dysfunction, hypertension and common inflammatory diseases. Studies show HerbaEpimedii also possesses anticancer activity. Flavonol glycosides icariin and icariside II are the main bioactive components of HerbaEpimedii. They have been found to possess anticancer activities against various human cancer cell lines in vitro and mouse tumor models in vivo via their effects on multiple biological pathways, including cell cycle regulation, apoptosis, angiogenesis, and metastasis, and a variety of signaling pathways including JAK2-STAT3, MAPK-ERK, and PI3k-Akt-mTOR. The review is aimed to provide an overview of the current research results supporting their therapeutic effects and to highlight the molecular targets and action mechanisms.

Anti-Cancer Properties of the Naturally Occurring Aphrodisiacs: Icariin and Its Derivatives

Epimedium (family Berberidaceae), commonly known as Horny Goat Weed or Yin Yang Huo, is commonly used as a tonic, aphrodisiac, anti-rheumatic and anti-cancer agent in traditional herbal formulations in Asian countries such as China, Japan, and Korea. The major bioactive compounds present within this plant include icariin, icaritin and icariside II. Although it is best known for its aphrodisiac properties, scientific and pharmacological studies suggest it possesses broad therapeutic capabilities, especially for enhancing reproductive function and osteoprotective, neuroprotective, cardioprotective, anti-inflammatory and immunoprotective effects. In recent years, there has been great interest in scientific investigation of the purported anti-cancer properties of icariin and its derivatives. Data from in vitro and in vivo studies suggests these compounds demonstrate anti-cancer activity against a wide range of cancer cells which occurs through various mechanisms such as apoptosis, cell cycle modulation, anti-angiogenesis, anti-metastasis and immunomodulation. Of note, they are efficient at targeting cancer stem cells and drug-resistant cancer cells. These are highly desirable properties to be emulated in the development of novel anti-cancer drugs in combatting the emergence of drug resistance and overcoming the limited efficacy of current standard treatment. This review aims to summarize the anti-cancer mechanisms of icariin and its derivatives with reference to the published literature. The currently utilized applications of icariin and its derivatives in cancer treatment are explored with reference to existing patents. Based on the data compiled, icariin and its derivatives are shown to be compounds with tremendous potential for the development of new anti-cancer drugs.

Knockdown of HOXA10 reverses the multidrug resistance of human chronic mylogenous leukemia K562/ADM cells by downregulating P-gp and MRP-1

Multidrug resistance (MDR) of leukemia cells is a major obstacle in chemotherapeutic treatment. The high expression and constitutive activation of P-glycoprotein (P-gp) and multidrug resistance protein-1 (MRP-1) have been reported to play a vital role in enhancing cell resistance to anticancer drugs in many tumors. The present study aimed to investigate the reversal of MDR by silencing homeobox A10 (HOXA10) in adriamycin (ADR)-resistant human chronic myelogenous leukemia (CML) K562/ADM cells by modulating the expression of P-gp and MRP-1. K562/ADM cells were stably transfected with HOXA10-targeted short hairpin RNA (shRNA). The results of reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis showed that the mRNA and protein expression of HOXA10 was markedly suppressed following transfection with a shRNA-containing vector. The sensitivity of the K562/ADM cells to ADR was enhanced by the silencing of HOXA10, due to the increased intracellular accumulation of ADR. The accumulation of ADR induced by the silencing of HOXA10 may be due to the downregulation of P-gp and MRP-1. Western blot analysis revealed that downregulating HOXA10 inhibited the protein expression of P-gp and MRP-1. Taken together, these results suggest that knockdown of HOXA10 combats resistance and that HOXA10 is a potential target for resistant human CML.

Ginkgolide B protects human umbilical vein endothelial cells against xenobiotic injuries via PXR activation

AIM

Pregnane X receptor (PXR) is a nuclear receptor that regulates a number of genes encoding drug metabolism enzymes and transporters and plays a key role in xeno- and endobiotic detoxification. Ginkgolide B has shown to increase the activity of PXR. Here we examined whether ginkgolide B activated PXR and attenuated xenobiotic-induced injuries in endothelial cells.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with ginkgolide B. The expression of PXR, CYP3A4, MDR1, VCAM-1, E-selectin and caspase-3 were quantified with qRT-PCR and Western blot analysis. Cell apoptosis was analyzed with flow cytometry. Fluorescently labeled human acute monocytic leukemia cells (THP-1 cells) were used to examine cell adhesion.

RESULTS

Ginkgolide B (30-300 μmol/L) did not change the mRNA and protein levels of PXR in the cells, but dose-dependently increased nuclear translocation of PXR protein. Ginkgolide B increased the expression of CYP3A4 and MDR1 in the cells, which was partially reversed by pretreatment with the selective PXR signaling antagonist sulforaphane, or transfection with PXR siRNA. Functionally, ginkgolide B dose-dependently attenuated doxorubicin- or staurosporine-induced apoptosis, which was reversed by transfection with PXR siRNA. Moreover, ginkgolide B suppressed TNF-α-induced THP-1 cell adhesion and TNF-α-induced expression of vascular adhesion molecule 1 (VCAM-1) and E-selectin in the cells, which was also reversed by transfection with PXR siRNA.

CONCLUSION

Ginkgolide B exerts anti-apoptotic and anti-inflammatory effects on endothelial cells via PXR activation, suggesting that a PXR-mediated endothelial detoxification program may be important for protecting endothelial cells from xeno- and endobiotic-induced injuries.