Multidrug-resistant Cancer Cell Lines Research Articles

Cytotoxic flavonoids from two Lonchocarpus species

A new isoflavone, 4′-prenyloxyvigvexin A (1) and a new pterocarpan, (6aR,11aR)-3,8-dimethoxybitucarpin B (2) were isolated from the leaves of Lonchocarpus bussei and the stem bark of Lonchocarpus eriocalyx, respectively. The extract of L. bussei also gave four known isoflavones, maximaisoflavone H, 7,2′-dimethoxy-3′,4′-methylenedioxyisoflavone, 6,7,3′-trimethoxy-4′,5′-methylenedioxyisoflavone, durmillone; a chalcone, 4-hydroxylonchocarpin; a geranylated phenylpropanol, colenemol; and two known pterocarpans, (6aR,11aR)-maackiain and (6aR,11aR)-edunol. (6aR,11aR)-Edunol was also isolated from the stem bark of L. eriocalyx. The structures of the isolated compounds were elucidated by spectroscopy. The cytotoxicity of the compounds was tested by resazurin assay using drug-sensitive and multidrug-resistant cancer cell lines. Significant antiproliferative effects with IC50 values below 10 μM were observed for the isoflavones 6,7,3′-trimethoxy-4′,5′-methylenedioxyisoflavone and durmillone against leukemia CCRF-CEM cells; for the chalcone, 4-hydroxylonchocarpin and durmillone against its resistant counterpart CEM/ADR5000 cells; as well as for durmillone against the resistant breast adenocarcinoma MDA-MB231/BCRP cells and resistant gliobastoma U87MG.ΔEGFR cells.

Novel Inhibitors of P‐Glycoprotein from In Silico Optimizations of Inhibitor SMU‐29 using the ChemGen Program

P‐glycoprotein (P‐gp) is an integral membrane efflux pump that is capable of lowering the intracellular concentration of many drugs to sub‐therapeutic levels. Consequently, P‐gp has been implicated in multidrug resistances (MDR) to cancer chemotherapies. One promising P‐gp inhibitor, SMU‐29, was previously identified by us using in silico methods (Brewer et al., Molecular Pharmacology 86, 716–726, 2014) and was later confirmed to reverse MDR in cancer cell culture experiments (Follit et al., Pharmacol. Res. Perspect. 3, e00170, 2015). We created millions of SMU‐29 variants in silico using our novel medicinal chemistry program, ChemGen, in efforts to pharmacologically optimize SMU‐29. In one set of chemical variants, only part of the structure of SMU‐29 was varied; in a second set of variants, only the central structural scaffold of SMU‐29 was conserved. We used in silico docking to identify chemical variants of SMU‐29 that exhibited high estimated affinities for P‐gp's nucleotide binding domains (NBDs), and low estimated affinity for P‐gp's transmembrane drug‐binding domain (DBD). Using this approach, we identified over 2000 ChemGen‐created variants with equivalent or better estimated affinities at the P‐gp NBDs relative to SMU‐29. We selected a small set of these SMU‐29 variants for chemical synthesis and further screening in vitro against multidrug resistant cancer cell lines. All of the tested and synthesized SMU‐29 variants were observed to act as P‐gp inhibitors with improved PC50 values. Some of these variants were also observed to inhibit the breast cancer resistance protein (BCRP), a related ABC‐transporter that is also implicated in MDR in cancer. Our previous screens that identified SMU‐29 as a hit compound had a 33% P‐gp inhibitor identification success rate (hit rate); the present in silico optimization of SMU‐29 using ChemGen has demonstrated a very high success rate of identifying P‐gp inhibitors with improved affinities for the target protein.Support or Funding InformationThis work is supported by NIH NIGMS [R15GM094771‐02] to John G. Wise, SMU University Research Council, the SMU Center for Drug Discovery, Design and Delivery, the Communities Foundation of Texas, and a private gift from Ms. Suzy Ruff of Dallas, Texas.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hexane fraction of adlay (Coix lachryma-jobi L.) testa ethanolic extract inhibits human uterine sarcoma cancer cells growth and chemosensitizes human uterine sarcoma cells to doxorubicin

BackgroundCancer has remained among the top ten causes of death in Taiwan since 1982. Uterine sarcoma is a rare gynecologic cancer, and chemotherapy is one type of cancer treatment. Doxorubicin (Dox) is widely used for treating several cancers, including uterine sarcoma, however, multidrug resistance (MDR) is a major clinical problem and a critical cause of treatment failure. The ethanolic extracts of adlay testa (ATE) exhibited significant anticancer activities against many cancer types. PurposeIn this study we investigated the antitumor effects of the hexane fraction of the adlay testa ethanolic extracts (ATE-Hex) on the human uterine sarcoma cancer cell line MES-SA, as well as on the multidrug-resistant human uterine sarcoma cancer cell line MES-SA/Dx5. MethodsThe MTT assay was performed to assess the effects of the extracts of different parts of the adlay on the proliferation of human uterine sarcoma cells (MES-SA and MES-SA/Dx5) and human uterine smooth muscle cells (HUtSMCs). To determine whether ATE-Hex has a chemosensitizing effect on drug-resistant uterine sarcoma cells, the MTT assay was performed to examine the synergistic effects of ATE-Hex, the chemotherapeutic drug Dox alone, and in combination. Rhodamine accumulation was analyzed using fluorescence detection. Apoptotic cells were analyzed via flow cytometry. In addition, employing a flame ionization detector (GC/FID) gas chromatography was also developed as the analysis platform for ATE-Hex. ResultsThe results demonstrated that ATE-Hex exhibited the best effects of inhibition on MES-SA and MES-SA/Dx5 cells. Co-treatment of ATE-Hex and Dox could synergistically inhibit the proliferation of cancer cells. ATE-Hex reduced the rhodamine efflux in MES-SA/Dx5 cells, indicating that ATE-Hex could reduce the expression of P-gp. In addition, our results showed that treatment with ATE-Hex alone or in combination with Dox significantly inhibited the growth of cancer cells and induced apoptosis by increasing the sub-G1 phase and poly(ADP-ribose) polymerase (PARP) being cleaved. Flow cytometry revealed that ATE-Hex induced apoptosis. ConclusionThese results suggest that ATE-Hex can inhibit human uterine sarcoma cancer cells by inducing apoptosis and increasing the chemosensitivity of the multidrug-resistant human uterine sarcoma cancer cell MES-SA/Dx5 to Dox. Furthermore, the combination of ATE-Hex and Dox could decrease MDR and increase the synergistic effect.

A novel tubulin inhibitor STK899704 induces tumor regression in DMBA/TPA-induced skin carcinogenesis model.

Skin cancer is the most common type of cancer. The incidence rate of skin cancer has continuously increased over the past decades. In an effort to discover novel anticancer agents, we identified a novel tubulin inhibitor STK899704, which is structurally distinct from other microtubule-binding agents such as colchicine, vinca alkaloids and taxanes. STK899704 inhibited microtubule polymerization leading to mitotic arrest and suppressed the proliferation of various cancer cell lines as well as multidrug resistance cancer cell lines. In this study, our investigation is further extended into animal model to evaluate the effect of STK899704 on skin carcinogenesis in vivo. Surprisingly, almost 80% of the tumors treated with STK899704 were regressed with a one-fifth reduction in tumor volume. Furthermore, the efficacy of STK899704 was nearly 2 times higher than that of 5-fluorouracil, a widely used skin cancer therapeutic. Overall, our results suggest that STK899704 is a promising anticancer chemotherapeutic that may replace existing therapies, particularly for skin cancer.

Mechanism of action of cytotoxic compounds from the seeds of Euphorbia lathyris

BackgroundThe seeds of Euphorbia lathyris are used in traditional Chinese medicines for the treatment of various medical conditions. E. lathyris contains many natural diterpenes with a lathyrane skeleton. Purpose and study designFive lathyrane-type diterpenoids named Euphorbia factors L1, L2, L3, L8, and L9 (1–5), were investigated for cytotoxicity against A549, MDA-MB-231, KB, and MCF-7 cancer cell lines and the KB-VIN multidrug resistant (MDR) cancer cell line. Also, a tetraol derivative (6) of Euphorbia factor L2 (2) was synthesized to assess the effect of hydroxy moieties. MethodsAn ethanolic extract of seeds of Euphorbia lathyris was prepared and separated into petroleum ether, EtOAc, n-butanol, and n-hexane extracts. The natural diterpenes were isolated by using silica gel and Sephadex LH-20 column chromatography as well as preparative thin-layer chromatography. Saponification of 2 gave tetraol derivative 6. Cytotoxic activity was determined by the sulforhodamine B (SRB) colorimetric assay. Mechanism of action studies focused on the impact of compounds on the cell cycle progression as well as cell morphology. ResultsCompound 5 exhibited the strongest cytotoxicity against all cell lines, while compound 2 showed selectivity against KB-VIN. In cells treated with 3 and 5, accumulation of G1 to early S phase cells was obvious, while no effect was seen on G2/M phase. ConclusionAnalysis of the screening data compared with compound structures suggested that the substitutions at C-3, C-5, C-7, and C-15 are critical for cytotoxicity, as well as cell type-selectivity. Furthermore, results of cytotoxic mechanism analysis demonstrated for the first time that compounds 3 and 5 disrupted normal cell cycle progression, whereas compounds 2‒5 induced obvious actin filament aggregation, as well as partial interference of the microtubule network.

Cytotoxic activity of medicinal plants of the Kakamega County (Kenya) against drug-sensitive and multidrug-resistant cancer cells

Ethnopharmacological relevanceThe geographical location of Kakamega County proximal to the Kakamega Rain Forest in Kenya and its rich flora represents an interesting resource of traditional medicinal plants. The medicinal plants in the present study are traditionally used to treat cancer in Kakamega County as recorded in published literature. Aim of the studyDue to multidrug resistance (MDR) and severe side effects of currently used drugs in clinical oncology, new candidate compounds are urgently required to improve treatment outcome. The present study explored the in vitro cytotoxic potential of 34 organic and 19 aqueous extracts of Kakamega medicinal plants towards sensitive and multidrug-resistant cancer cell lines. Methods and resultsThe cytotoxicity was determined using the resazurin assay. Eight organic and two aqueous plant extracts inhibited the growth of CCRF-CEM leukemia cells by more than 50%. The organic extracts were Harungana madagascariensis Lam. ex poir (6.6% of untreated control), Prunus africana (Hook.f.) Kalkman (19.4%), Entada abyssinica Steud. ex A. Rich (38.6%), Phyllanthus fischeri Pax (40.7%), Shirakiopsis elliptica (Hochst.) Esser Synonym: Sapium ellipticum (Hochst. kraus) Pax (41.8%), Bridelia micrantha (Hochst.) Baill (45.4%) and Futumia africana Benth. (45.8%) and Microglossa pyrifolia (Lam.) Kuntze (48%). The aqueous extracts were Bridelia micrantha (Hochst.) Baill (31.3%) and Shirakiopsis elliptica (Hochst.) Esser Synonym: Sapium ellipticum (Hochst. Kraus) Pax (48.2%). In addition to P-glycoprotein-expressing tumor cells, we also investigated other mechanisms of drug resistance, i.e. BCRP- or EGFR-transfected and TP53-knockout tumor cells. Some extracts also showed considerable cytotoxic activity against these drug-resistant cell lines. As demonstrated for selected examples, some extracts exhibited enhanced cytotoxicity towards cancer cells, if applied in combination with other extracts. DiscussionThe panel of medicinal plants used in the Kakamega County for cancer treatment revealed indeed cytotoxicity to various extent towards cancer cells in vitro. Hence, our results may at least in part substantiate the traditional use of these compounds to treat cancer. Even more interesting, several extracts inhibited otherwise drug-resistant tumor cell lines with similar or even better efficacy than their drug-sensitive counterparts. This provides an attractive perspective for further exploration of their anticancer potential to combat drug resistance of refractory tumors.

Curcumin Co-Treatment Sensitizes Multi-Drug Resistant Ht29 Colon Cancer Cell Line

Curcumin Co-Treatment Sensitizes Multi-Drug Resistant Ht29 Colon Cancer Cell Line

Curcumin Co-Treatment Sensitizes Multi-Drug Resistant Ht29 Colon Cancer Cell Line

Colorectal cancer has been confirmed to be the third most dreadful cancer across the world. The latest reports show that the colorectal cancer is increasing in India at a high rate due to food habits, particularly consuming the foods with high fat content. Chemotherapy has been considered as a potential treatment in the control of a wide range of cancers recently, such as gastrointestinal cancers and so on. The scientists are looking to come up with new drugs to treat cancer by regulating the carcinogenesis with minimal toxicity. Curcumin is a phytochemical extracted from turmeric. It is highly effective product of the rhizomes of Curcuma longa L. (Zingiberaceae). It is also considered as a valuable drug for chemotherapeutic treatments in cancer. In case of animal studies, it has been clearly mentioned that curcumin controls carcinogenesis in various other organs as well as colon. Curcumin exhibits the capability to act as anti-mutagenic, anti-inflammatory drug as well. It has also been confirmed that the P-gp expression regulation is carried out by curcumin by inhibiting the COX-2 expression. Also, it has been clearly stated that curcumin down-regulates NF-kB pathway in various cell lines like Colo 205 colon cancer cell line etc. Multi Drug Resistance (MDR) plays a key role in case of the cancer cells to exhibit the resistance against the cytotoxicity of various chemotherapeutic drugs. This type of characteristics in cancer cells is developed due to low levels of the chemotherapeutic drug accumulated inside the cells during repeated exposure to the drug, showing the over-expression of P-glycoprotein (MDR-1). P-glycoprotein, a transporter protein, allows the cells to expel the wide range of chemotherapeutic drugs. The latest reports show that COX-2 expression and P-gp expression possess strong correlation with each other. In this research study, we generated the Multi-Drug Resistant HT29 Human colon cancer cells by treating the cells with increasing concentrations of a chemotherapeutic drug namely Doxorubicin Hydrochloride (DOX) and further we estimated the intracellular drug concentration in treated live as well as dead cells with the help of Doxorubicin Accumulation Assay. Also, the cell morphology change was studied in HT29 cells after every 24 hours of the DOX treatment separately as well as curcumin co-treatment (DOX+Curcumin). The curcumin co-treatment was carried out to observe the effect of curcumin on multi-drug resistant HT29 colon cancer cells and further study can be extended to investigate the various inflammatory genes controlled by NFkB at mRNA and protein level as well as the levels of cytokines which may get down-regulated by treatment. This study will help to completely understand the mechanism of reducing the effect of Multidrug Resistance (a unique property of cancer) by curcumin in case of colon cancer.

Metabolomics analysis of multidrug-resistant breast cancer cells in vitro using methyl-tert-butyl ether method.

The comprehensive characterization of metabolome and lipidome to reveal unknown pathological conditions, are being used to investigate the molecular mechanisms of cancer, especially in the field of early diagnosis, treatment, and prognosis. The multidrug resistance (MDR) of tumor cells limits the therapeutic effect of anti-cancer drugs and is the main obstacle for chemotherapy. Here, we adopted a methyl-tert-butyl ether (MTBE)-based extraction method to simultaneously extract small polar molecules and lipophilic metabolites for nontargeted metabolomics of multidrug-resistant breast cancer cell line MCF-7/ADR and its parental cell line MCF-7/S by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Distinctly different metabolic features were shown between MCF-7/ADR cells and MCF-7/S on the basis of multivariate analyses. 17 potential biomarkers were identified. And these potential biomarkers were mainly correlated with cell membrane lipids composition, cell signaling regulated by lipids, and anti-oxidation ability. The studies of cellular ultrastructure and morphology by in situ atomic force microscopy (AFM) also demonstrated the cellular membrane changed along with the MDR. We expect that this study could provide a new method for monitoring drug resistance during clinical chemotherapy and be useful for the development of drugs to overcome the MDR.

Vitexin induces apoptosis by suppressing autophagy in multi-drug resistant colorectal cancer cells.

Cancer treatment is limited due to the diverse multidrug resistance acquired by cancer cells and the collateral damage caused to adjacent normal cells by chemotherapy. The flavonoid compound vitexin exhibits anti-oxidative, anti-inflammatory and anti-tumor activity. This study elucidated the antitumor effects of vitexin and its underlying mechanisms in a multi-drug resistant human colon cancer cell line (HCT-116DR), which exhibits higher levels of multidrug-resistant protein 1 (MDR1) expression as compared with its parental cell line (HCT-116). Here, we observed that vitexin suppressed MDR-1 expression and activity in HCT-116DR cells and showed cytotoxic effect in HCT-116DR cells by inhibiting autophagy and inducing apoptosis in a concentration-dependent manner. Additionally, vitexin treatment caused cleavage of caspase-9 and caspase-3, and upregulated the expression of the pro-apoptotic proteins, BID and Bax. Moreover, the expression of autophagy-related proteins, such as ATG5, Beclin-1 and LC3-II, was markedly reduced by vitexin treatment. Furthermore, in vivo experiments showed that vitexin induced apoptosis and suppressed tumor growth in HCT-116DR xenograft model. These results revealed that vitexin induced apoptosis through suppression of autophagy in vitro and in vivo and provide insight into the therapeutic potential of vitexin for the treatment of chemo-resistant colorectal cancer.

Co-Delivery of Itraconazole and Docetaxel by Core/Shell Lipid Nanocells for Systemic Antiangiogenesis and Tumor Growth Inhibition.

The combination of antiangiogenesis with chemotherapy has become a promising multi-modal combinational therapy for solid tumor. However, hypoxia-mediated resistance and the subsequent treatment failure associated with antiangiogenesis therapy have limited the maximization of this promising approach. It remains a major challenge to balance the effect of angiogenesis and the accumulation of the cytotoxic drug within the tumor microenvironment. In this study, we report a nanotechnology based drug delivery solution that would improve both the antiangiogenic activity and cytotoxic efficacy of the loaded drugs. We designed core-shell 'lipid nanocells' drug delivery systems (denoted as DTX/ITZ-LNCs), which entrapped the antiangiogenic drug itraconazole (ITZ) in the outside liposomal shell and encapsulated anticancer drug docetaxel (DTX) in the inner hydrophobic PLGA core. In vitro evaluations showed that the dual drug loaded DTX/ITZ-LNCs retained the cytotoxic efficacy of the DTX against both the sensitive and multidrug resistant breast cancer cell line MCF-7. DTX/ITZ-LNCs also effectively inhibited the vascular endothelial growth factor (VEGF) induced migratory and invasive actions of HUVECs and neovascularization of subcutaneously implanted matrigel plugs. The tumor growth of MCF-7 tumor xenograft model was effectively inhibited by the systemic administration of the DTX/ITZ-LNCs. Taken together, these results showed that the DTX/ITZ-LNCs provided a drug delivery platform that can optimize the combinatory effects of the antiangiogenic agent with a conventional chemotherapeutic agent.

Computational design and synthesis of novel fluoro-analogs of combretastatins A-4 and A-1

Combretastatin A-1 (CA-1) and combretastatin A-4 (CA-4) isolated from the African bush willow Combretum caffrum are highly potent tubulin polymerization inhibitors, possessing strong antitumor activities because of their vascular disrupting properties. Extensive SAR studies have been done for CA-4 analogs. Because of poor solubility, water-soluble prodrugs of CA-4 and CA-1 have been developed, which are currently in human clinical trials. Fluorine plays an important role in the current drug discovery and development due to its unique properties. Thus, several fluorine-containing analogs of CA-4/CA-1 have been studied. However, no analogs, which have a CF3O-, CF2HO- or CF3- group instead of the 4′-methoxy group in the B ring, have been investigated. Therefore, we set out to design and synthesize those novel fluoro-analogs of CA-4/CA-1. For the design of the new analogs, we took a structure-based design approach based on the X-ray crystal structure of colchicine-tubulin complex (PDB: 4O2B) and computational docking analysis using the AutoDock Vina program. A library of novel fluoro-analogs of CA-4/CA-1 was generated and their docking energy scores obtained. It was found that those novel fluoro-analogs exhibited better docking energy scores than CA-4/CA-1. Also, docking poses of all of these fluoro-analogs were virtually superimposable and very good fit to the colchine binding site. Among 15 compounds designed and analyzed, we have synthesized 5 compounds and evaluated their cytotoxicity against drug-sensitive and multidrug-resistant cancer cell lines. All fluoro-analogs exhibited strong cytotoxicity even against multidrug-resistant cell line. However, the critical activity of this class of compounds is its vascular disrupting activity. Thus, further biological evaluations are warranted for those novel fluoro-analogs of CA-4/CA-1.

Tyrphostin RG14620 selectively reverses ABCG2-mediated multidrug resistance in cancer cell lines

The multidrug resistance (MDR) phenotype associated with the overexpression of ATP-binding cassette (ABC) drug transporters ABCB1, ABCC1 and ABCG2 is a major obstacle in cancer chemotherapy. Numerous epidermal growth factor receptor (EGFR) inhibitors have previously been shown capable of reversing MDR in ABCG2-overexpressing cancer cells. However, most of them are not transporter-specific due to the substantial overlapping substrate specificity among the transporters. In this study, we investigated the interaction between ABCG2 and tyrphostin RG14620, an EGFR inhibitor of the tyrphostin family, in multidrug-resistant cancer cell lines. We found that at nontoxic concentrations, tyrphostin RG14620 enhances drug-induced apoptosis and restores chemosensitivity to ABCG2-overexpressing multidrug-resistant cancer cells. More importantly, tyrphostin RG14620 is selective to ABCG2 relative to ABCB1 and ABCC1. Our findings were further supported by biochemical assays demonstrating that tyrphostin RG14620 stimulates ATP hydrolysis and inhibits photoaffinity labeling of ABCG2 with IAAP, and by a docking analysis of tyrphostin RG14620 in the drug-binding pocket of this transporter. Taken together, our findings indicate that tyrphostin RG14620 is a potent and selective modulator of ABCG2 that may be useful to overcome chemoresistance in patients with drug-resistant tumors.

Isatin-benzoazine molecular hybrids as potential antiproliferative agents: synthesis and in vitro pharmacological profiling.

In continuation of our endeavor with respect to the development of potent and effective isatin-based anticancer agents, we adopted the molecular hybridization approach to design and synthesize four different sets of isatin-quinazoline (6a–f and 7a–e)/phthalazine (8a–f)/quinoxaline (9a–f) hybrids. The antiproliferative activity of the target hybrids was assessed towards HT-29 (colon), ZR-75 (breast) and A-549 (lung) human cancer cell lines. Hybrids 8b–d emerged as the most active antiproliferative congener in this study. Compound 8c induced apoptosis via increasing caspase 3/7 activity by about 5-fold in the A-549 human cancer cell line. In addition, it exhibited an increase in the G1 phase and a decrease in the S and G2/M phases in the cell cycle effect assay. Furthermore, it displayed an inhibitory concentration 50% value of 9.5 µM against multidrug-resistant NCI-H69AR lung cancer cell line. The hybrid 8c was also subjected to in vitro metabolic investigations through its incubation with rat liver microsomes and analysis of the resulting metabolites with the aid of liquid chromatography-mass spectrometry.

Cytotoxicity and mode of action of a naturally occurring naphthoquinone, 2-acetyl-7-methoxynaphtho[2,3-b]furan-4,9-quinone towards multi-factorial drug-resistant cancer cells

IntroductionMalignacies are still a major public concern worldwide and despite the intensive search of new chemotherapeutic agents, treatment still remains a challenging issue. The present study was designed to evaluate the cytotoxicity of 2-acetyl-7-methoxynaphtho[2,3-b]furan-4,9-quinone (AMNQ) isolated from the bark of Milletia versicolor towards a panel of drug-sensitive and multidrug-resistant (MDR) cancer cell lines. MethodsThe resazurin reduction assay was used to evaluate the cytotoxicity of AMNQ against 9 drug-sensitive and multidrug-resistant (MDR) cancer cell lines. Cell cycle, mitochondrial membrane potential (MMP) and levels of reactive oxygen species were all analyzed by flow cytometry. ResultsFollowing resazurin assay, the naphthoquinone AMNQ displayed IC50 values ranging from 0.79 µM (against HepG2 hepatocarcinoma cells) to 3.26 µM (against MDA-MB231/BCRP breast cancer cells) on 9 tested cancer cell lines, whilst doxorubicin showed IC50 values ranging from 0.40 µM (against CCRF-CEM leukemia cells) to 91.37 µM (against CEM/ADR5000 leukemia cells). IC50 values below 1 µM were recorded with AMNQ towards CCRF-CEM cells (0.57 µM), U87MG.ΔEGFR gliobastoma multiforme cells (0.96 µM cells) and HepG2 cells (0.76 µM). Compared to its corresponding sensitive cell lines U87MG, sensitivity was observed in epidermal growth factor receptor-transfected U87MG.ΔEGFR cells to AMNQ. MMP was found to be the main mode of action of induction of apoptosis by AMNQ. ConclusionsThe results of this work demonstrate the cytotoxicity of AMNQ towards various types of cancer cell lines, including MDR phenotypes. AMNQ is a potential antiproliferative natural compound that deserves more investigations to develop novel cytotoxic drugs against sensitive and MDR cancers.

Cryptophycins: cytotoxic cyclodepsipeptides with potential for tumor targeting.

Cryptophycins are a class of 16-membered highly cytotoxic macrocyclic depsipeptides isolated from cyanobacteria. The biological activity is based on their ability to interact with tubulin. They interfere with microtubule dynamics and prevent microtubules from forming correct mitotic spindles, which causes cell-cycle arrest and apoptosis. Their strong antiproliferative activities with 100-fold to 1000-fold potency compared with those of paclitaxel and vinblastine have been observed. Cryptophycins are highly promising drug candidates, as their biological activity is not negatively affected by P-glycoprotein, a drug efflux system commonly found in multidrug-resistant cancer cell lines and solid tumors. Cryptophycin-52 had been investigated in phase II clinical trials but failed because of its high neurotoxicity. Recently, cryptophycin conjugates with peptides and antibodies have been developed for targeted delivery in tumor therapy. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

TNF-α exerts cytotoxic effects on multidrug resistant breast cancer MCF-7/MX cells via a non-apoptotic death pathway

Tumor necrosis factor-α (TNF-α) is a cytokine involved in the various physiopathological processes such as autoimmune disorders and inflammation related diseases. Some multidrug resistant (MDR) cancer cell lines including MCF-7/MX are more vulnerable to cytotoxic effects of TNF-α than their parental lines. In this study, breast cancer cell line MCF-7 and its MDR derivative MCF-7/MX were exposed to TNF-α afterward various downstream signaling mediators of TNF-α were analyzed. Although, treatment of MCF-7 cells with TNF-α activated NF-kB and caused RIP1 ubiquitination, TNF-α exposure led to JNK and RIP1 phosphorylation in MCF-7/MX cells. In both cell lines TNF-α did not activate the caspase cascade. Moreover, AnexinV/PI analysis showed that cytotoxic effects of TNF-α on MCF-7/MX is mediated via apoptosis independent mechanisms and inhibition of RIP1 kinase activity using necrostatin-1 revealed that kinase activity of RIP1 plays role in the production of ROS, activation of JNK and cellular death following exposure of MCF-7/MX cells to TNF-α. Overall, it seems that RIP1 ubiquitination and NF-kB activation are prosurvival signaling mediators protecting MCF-7 cells against cytotoxic effects of TNF-α while TNF-α drives MCF-7/MX cells to non-apoptotic cellular death via kinase activity of RIP1, activation of JNK and ROS production.

Cryptotanshinone induces ROS-dependent autophagy in multidrug-resistant colon cancer cells

The development of novel chemotherapeutic agents is highly desired for colon cancer treatment, in particular for the multidrug-resistant cancer types. Cryptotanshinone (CTS), an active quinoid diterpene isolated from Salvia miltiorrhiza Bunge, was previously reported to induce autophagy in various colon cancer cell lines. However, its mechanisms of action have not been fully understood. The current study aims to explore the mechanisms by which CTS induces autophagy in a multidrug-resistant human colon cancer cell line SW620 Ad300. Using MTT assay, CTS at 10 μM exhibited no significant cytotoxicity on human normal colon fibroblasts CCD-18Co, but induced 45.67% and 48.35% cell death in SW620 and SW620 Ad300 cells, respectively. Further studies revealed that CTS induced weak apoptosis (9.37%) and significant caspase-independent cell death in SW620 Ad300 cells. In the same cell line, CTS also induced significant autophagy, which was found to promote cell death and to mediate the cytotoxicity of CTS in these multidrug-resistant cells. Moreover, activation of ROS-p38 MAPK-NF-κB signaling pathway was involved in autophagic cell death induced by CTS in SW620 Ad300 cells. Interestingly, our results also demonstrated a complementary relationship between CTS-induced apoptosis and autophagic cell death in SW620 Ad300 cells. Taken together, CTS induces autophagic cell death in SW620 Ad300 cells via the ROS-p38 MAPK-NF-κB signaling pathway, and it might be a potential candidate as a chemotherapeutic agent for the treatment of multidrug-resistant colon cancer.

Synthesis and SAR Study of Anticancer Protoflavone Derivatives: Investigation of Cytotoxicity and Interaction with ABCB1 and ABCG2 Multidrug Efflux Transporters.

There is a constant need for new therapies against multidrug-resistant (MDR) cancer. Natural compounds are a promising source of novel anticancer agents. We recently showed that protoflavones display activity in MDR cancer cell lines that overexpress the P-glycoprotein (P-gp) drug efflux pump. In this study, 52 protoflavones, including 22 new derivatives, were synthesized and tested against a panel of drug-sensitive parental cells and their MDR derivatives obtained by transfection with the human ABCB1 or ABCG2 genes, or by adaptation to chemotherapeutics. With the exception of protoapigenone, identified as a weak ABCG2 substrate, all protoflavones bypass resistance conferred by these two transporters. The majority of the compounds were found to exhibit mild to strong (up to 13-fold) selectivity against the MCF-7Dox and KB-V1 cell lines, but not to transfected MDR cells engineered to overexpress the MDR transporters. Our results suggest that protoflavones can overcome MDR cancer by evading P-gp-mediated efflux.

DTA0100, dual topoisomerase II and microtubule inhibitor, evades paclitaxel resistance in P-glycoprotein overexpressing cancer cells

The efficacy of microtubule targeting agents in cancer treatment has been compromised by the development of drug resistance that may involve both, P-glycoprotein overexpression and the changes in β-tubulin isoforms' expression. The anti-Topoisomerase II activity of methyl 4-((E)-2-(methoxycarbonyl)vinyloxy)oct-2-ynoate (DTA0100) was recently reported. Herein, we further evaluated this propargylic enol ether derivative and found that it exerts inhibitory effect on tubulin polymerization by binding to colchicine binding site. DTA0100 mitotic arrest properties were investigated in two multi-drug resistant cancer cell lines with P-glycoprotein overexpression (colorectal carcinoma and glioblastoma). The sensitivity of multi-drug resistant cancer cell lines to DTA0100 was not significantly changed in contrast to microtubule targeting agents such as paclitaxel, vinblastine and colchicine. DTA0100 clearly induced microtubule depolymerization, leading to disturbance of cell cycle kinetics and subsequent apoptosis. The fine-tuning in β-tubulin isoforms expression observed in multi-drug resistant cancer cells may influence the efficacy of DTA0100. Importantly, DTA0100 blocked the P-glycoprotein function in both multi-drug resistant cancer cell lines without inducing the increase in P-glycoprotein expression. Therefore, DTA0100 acting as dual inhibitor of Topoisomerase II and microtubule formation could be considered as multi-potent anticancer agent. Besides, it is able to overcome the problem of drug resistance that emerges in the therapeutic approaches with either Topoisomerase II or microtubule targeting agents.