Combination of Vismodegib and Paclitaxel Enhances Cytotoxicity via Bak-mediated Mitochondrial Damage in EGFR-Mutant Non-Small Cell Lung Cancer Cells.

Half of NSCLC patients harbor epidermal growth factor receptor (EGFR) mutations, and their therapeutic responses are remarkably different from patients with wild-type EGFR (EGFR-WT) NSCLC. We previously demonstrated that the hedgehog inhibitor vismodegib (Vis) potentiates paclitaxel (PTX)-induced cytotoxicity via suppression of Bax phosphorylation, which promotes accumulation of mitochondrial damage and apoptosis in EGFR-WT NSCLC cells. In this study, we further delineated the anticancer activity and underlying mechanisms of this combination treatment in EGFR-mutant NSCLC cells. MTS/PMS activity and trypan blue exclusion assays were used to assess cell viability. Apoptosis was monitored by chromosome condensation, annexin V staining, and cleavage of PARP and caspase-3. Western blots were conducted to track proteins of interest after treatment. Reactive oxygen species (ROS) level was monitored by 2',7'-dichlorodihydrofluorescein diacetate. Mitochondrial status was analyzed by tetramethylrhodamine, ethyl ester. Hedgehog signaling was induced by PTX, which rendered H1975 and PC9 cells insensitive to PTX-induced mitochondrial apoptosis via suppression of Bak. However, Vis enhanced PTX-induced Bak activation, leading to mitochondrial damage, ROS accumulation, and subsequent apoptosis. Our findings suggest that the combination of Vis and PTX could be a potential therapeutic strategy to increase PTX sensitivity of EGFR-mutant NSCLC.

Vismodegib Potentiates Marine Antimicrobial Peptide Tilapia Piscidin 4-Induced Cytotoxicity in Human Non-Small Cell Lung Cancer Cells.

Non-small cell lung cancer (NSCLC) is a common cancer with several accepted treatments, such as chemotherapy, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, and immune checkpoint inhibitors. Nevertheless, NSCLC cells often become insensitive to these treatments, and therapeutic resistance is a major reason NSCLC still has a high mortality rate. The induction of therapeutic resistance in NSCLC often involves hedgehog, and suppression of hedgehog can increase NSCLC cell sensitivity to several conventional therapies. In our previous work, we demonstrated that the marine antimicrobial peptide tilapia piscidin 4 (TP4) exhibits potent anti-NSCLC activity in both EGFR-WT and EGFR-mutant NSCLC cells. Here, we sought to further explore whether hedgehog might influence the sensitivity of NSCLC cells to TP4. Our results showed that hedgehog was activated by TP4 in both WT and EGFR-mutant NSCLC cells and that pharmacological inhibition of hedgehog by vismodegib, a Food and Drug Administration-approved hedgehog inhibitor, potentiated TP4-induced cytotoxicity. Mechanistically, vismodegib acted by enhancing TP4-mediated increases in mitochondrial membrane potential and intracellular reactive oxygen species (ROS). MitoTempo, a specific mitochondrial ROS scavenger, abolished vismodegib/TP4 cytotoxicity. The combination of vismodegib with TP4 also reduced the levels of the antioxidant proteins catalase and superoxide dismutase, and it diminished the levels of chemoresistance-related proteins, Bcl-2 and p21. Thus, we conclude that hedgehog regulates the cytotoxic sensitivity of NSCLC cells to TP4 by protecting against mitochondrial dysfunction and suppressing oxidative stress. These findings suggest that combined treatment of vismodegib and TP4 may be a promising therapeutic strategy for NSCLC.

Repurposing the diuretic benzamil as an anti-osteosarcoma agent that acts by suppressing integrin/FAK/STAT3 signalling and compromising mitochondrial function.

Aims: Osteosarcoma is the most common primary bone malignancy among children and adolescents. We investigated whether benzamil, an amiloride analogue and sodium-calcium exchange blocker, may exhibit therapeutic potential for osteosarcoma in vitro. Methods: MG63 and U2OS cells were treated with benzamil for 24 hours. Cell viability was evaluated with the MTS/PMS assay, colony formation assay, and flow cytometry (forward/side scatter). Chromosome condensation, the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, cleavage of poly-ADP ribose polymerase (PARP) and caspase-7, and FITC annexin V/PI double staining were monitored as indicators of apoptosis. Intracellular calcium was detected by flow cytometry with Fluo-4 AM. The phosphorylation and activation of focal adhesion kinase (FAK) and signal transducer and activator of transcription 3 (STAT3) were measured by western blot. The expression levels of X-linked inhibitor of apoptosis protein (XIAP), B-cell lymphoma 2 (Bcl-2), B-cell lymphoma-extra large (Bcl-xL), SOD1, and SOD2 were also assessed by western blot. Mitochondrial status was assessed with tetramethylrhodamine, ethyl ester (TMRE), and intracellular adenosine triphosphate (ATP) was measured with BioTracker ATP-Red Live Cell Dye. Total cellular integrin levels were evaluated by western blot, and the expression of cell surface integrins was assessed using fluorescent-labelled antibodies and flow cytometry. Results: Benzamil suppressed growth of osteosarcoma cells by inducing apoptosis. Benzamil reduced the expression of cell surface integrins α5, αV, and ß1 in MG63 cells, while it only reduced the expression of αV in U2OS cells. Benzamil suppressed the phosphorylation and activation of FAK and STAT3. In addition, mitochondrial function and ATP production were compromised by benzamil. The levels of anti-apoptotic proteins XIAP, Bcl-2, and Bcl-xL were reduced by benzamil. Correspondingly, benzamil potentiated cisplatin- and methotrexate-induced apoptosis in osteosarcoma cells. Conclusion: Benzamil exerts anti-osteosarcoma activity by inducing apoptosis. In terms of mechanism, benzamil appears to inhibit integrin/FAK/STAT3 signalling, which triggers mitochondrial dysfunction and ATP depletion.

Impacts of hyperthermic chemotherapeutic agent on cytotoxicity, chemoresistance-related proteins and PD-L1 expression in human gastric cancer cells.

Objective: Gastric cancer with peritoneal metastasis is considered to be final stage gastric cancer. One current treatment approach for this condition is combined cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC). However, the therapeutic mechanisms of HIPEC remain largely undescribed. Method: In order to assess the cellular effects of HIPEC in vitro, we treated AGS human gastric adenocarcinoma cells with or without 5-fluorouracil (5-Fu) at 37 °C or at 43 °C (hyperthermic temperature) for 1 h followed by incubation at 37 °C for 23 h. The impacts of hyperthermia/5-Fu on apoptosis, cell survival signals, oxidative stress, chemoresistance-related proteins and programmed death-ligand 1 (PD-L1) expression were measured. Results: Our results showed that hyperthermia potentiates 5-Fu-mediated cytotoxicity in AGS cells. Furthermore, the combination of 5-Fu and hyperthermia reduces levels of both phosphorylated STAT3 and STAT3, while increasing the levels of phosphorylated Akt and ERK. In addition, 5-Fu/hyperthermia enhances reactive oxygen species and suppresses superoxide dismutase 1. Chemoresistance-related proteins, such as multidrug resistance 1 and thymidylate synthase, are also suppressed by 5-Fu/hyperthermia. Interestingly, hyperthermia enhances 5-Fu-mediated induction of glycosylated PD-L1, but 5-Fu-mediated upregulation of PD-L1 surface expression is prevented by hyperthermia. Conclusion: Taken together, our findings provide insights that may aid in the development of novel therapeutic strategies and enhanced therapeutic efficacy of HIPEC.

Marine Antimicrobial Peptide Epinecidin-1 Inhibits Proliferation Induced by Lipoteichoic acid and Causes cell Death in non-small cell lung cancer Cells via Mitochondria Damage.

Non-small cell lung cancer (NSCLC) is among the deadliest cancers worldwide. Despite the recent introduction of several new therapeutic approaches for the disease, improvements in overall survival and progression-free survival have been minimal. Conventional treatments for NSCLC include surgery, chemotherapy and radiotherapy. Except for surgery, these treatments can impair a patient's immune system, leaving them susceptible to bacterial infections. As such, Staphylococcus aureus infections are commonly seen in NSCLC patients receiving chemotherapy, and a major constituent of the S. aureus cell surface, lipoteichoic acid (LTA), is thought to stimulate NSCLC cancer cell proliferation. Thus, inhibition of LTA-mediated cell proliferation might be a useful strategy for treating NSCLC. Epinecidin-1 (EPI), a marine antimicrobial peptide, exhibits broad-spectrum antibacterial activity, and it also displays anti-cancer activity in glioblastoma and synovial sarcoma cells. Furthermore, EPI has been shown to inhibit LTA-induced inflammatory responses in murine macrophages. Nevertheless, the anti-cancer and anti-LTA activities of EPI and the underlying mechanisms of these effects have not been fully tested in the context of NSCLC. In the present study, we demonstrate that EPI suppresses LTA-enhanced proliferation of NSCLC cells by neutralizing LTA and blocking its effects on toll-like receptor 2 and interleukin-8. Moreover, we show that EPI induces necrotic cell death via mitochondrial damage, elevated reactive oxygen species levels, and disrupted redox balance. Collectively, our results reveal dual anti-cancer activities of EPI in NSCLC, as the peptide not only directly kills cancer cells but it also blocks LTA-mediated enhancement of cell proliferation.

Dietary fatty acids differentially affect secretion of pro-inflammatory cytokines in human THP-1 monocytes.

Monocytes are a major population of circulating immune cells that play a crucial role in producing pro-inflammatory cytokines in the body. The actions of monocytes are known to be influenced by the combinations and concentrations of certain fatty acids (FAs) in blood and dietary fats. However, systemic comparisons of the effects of FAs on cytokine secretion by monocytes have not be performed. In this study, we compared how six saturated FAs (SFAs), two monounsaturated FAs (MUFAs), and seven polyunsaturated FAs (PUFAs) modulate human THP-1 monocyte secretion of TNF, IL-1ß, and IL-6 in the absence or presence of lipopolysaccharide. SFAs generally stimulated resting THP-1 cells to secrete pro-inflammatory cytokines, with stearic acid being the most potent species. In contrast, MUFAs and PUFAs inhibited lipopolysaccharide-induced secretion of pro-inflammatory cytokines. Interestingly, the inhibitory potentials of MUFAs and PUFAs followed U-shaped (TNF and IL-1ß) or inverted U-shaped (IL-6) dose-response curves. Among the MUFAs and PUFAs that were analyzed, docosahexaenoic acid (C22:6 n-3) exhibited the largest number of double bonds and was found to be the most potent anti-inflammatory compound. Together, our findings reveal that the chemical compositions and concentrations of dietary FAs are key factors in the intricate regulation of monocyte-mediated inflammation.

Targeting BRD3 eradicates nuclear TYRO3-induced colorectal cancer metastasis.

Metastasis is the main cause of death in many cancers including colorectal cancer (CRC); however, the underlying mechanisms responsible for metastatic progression remain largely unknown. We found that nuclear TYRO3 receptor tyrosine kinase is a strong predictor of poor overall survival in patients with CRC. The metastasis-promoting function of nuclear TYRO3 requires its kinase activity and matrix metalloproteinase-2 (MMP-2)-mediated cleavage but is independent of ligand binding. Using proteomic analysis, we identified bromodomain-containing protein 3 (BRD3), an acetyl-lysine reading epigenetic regulator, as one of nuclear TYRO3's substrates. Chromatin immunoprecipitation-sequencing data reveal that TYRO3-phosphorylated BRD3 regulates genes involved in anti-apoptosis and epithelial-mesenchymal transition. Inhibition of MMP-2 or BRD3 activity by selective inhibitors abrogates nuclear TYRO3-induced drug resistance and metastasis in organoid culture and in orthotopic mouse models. These data demonstrate that MMP-2/TYRO3/BRD3 axis promotes the metastasis of CRC, and blocking this signaling cascade is a promising approach to ameliorate CRC malignancy.

Design and synthesis of benzylidenecyclohexenones as TrxR inhibitors displaying high anticancer activity and inducing ROS, apoptosis, and autophagy.

Oxidative therapy, a strategy that specifically increases reactive oxygen species (ROS) levels in tumor cells by disrupting the redox homeostasis has gained increasing interest. The antitumor effects of the natural product piperlongumine (PL) appear to result from its ability to increase intracellular ROS levels via inhibition of antioxidative thioredoxin reductase (TrxR). Twenty-seven benzylidenecyclohexenone-based PL analogues (2a-v and 15a-e) were designed, synthesized and evaluated for their pharmacological properties. Most of the compounds exhibited potent antiproliferative activities against five human cancer cell lines, especially against breast tumor cells. One of the most promising analogueues 2c showed 12-fold higher inhibitory activity against the thioredoxin reductase (TrxR) than PL and surpressed the expression of TrxR1 protein in breast cancer cells and inhibited TrxR enzymatic activity. In addition, 2c increased ROS levels and resulted in marked apoptosis by regulating apoptosis-related proteins expressed in the breast cancer cells. Compound 2c also triggered the formation of autophagosomes and autolysosomes by promoting the expression of LC3-II and Beclin-1 and diminishing the expression of LC3-I and p62 proteins. Finally, 2c displayed low acute toxicity and good inhibitory potency to tumors in mice. Overall, 2c is a promising anti-breast cancer candidate warranting further investigation.

Pathophysiological implications of hypoxia in human diseases.

Oxygen is essentially required by most eukaryotic organisms as a scavenger to remove harmful electron and hydrogen ions or as a critical substrate to ensure the proper execution of enzymatic reactions. All nucleated cells can sense oxygen concentration and respond to reduced oxygen availability (hypoxia). When oxygen delivery is disrupted or reduced, the organisms will develop numerous adaptive mechanisms to facilitate cells survived in the hypoxic condition. Normally, such hypoxic response will cease when oxygen level is restored. However, the situation becomes complicated if hypoxic stress persists (chronic hypoxia) or cyclic normoxia-hypoxia phenomenon occurs (intermittent hypoxia). A series of chain reaction-like gene expression cascade, termed hypoxia-mediated gene regulatory network, will be initiated under such prolonged or intermittent hypoxic conditions and subsequently leads to alteration of cellular function and/or behaviors. As a result, irreversible processes occur that may cause physiological disorder or even pathological consequences. A growing body of evidence implicates that hypoxia plays critical roles in the pathogenesis of major causes of mortality including cancer, myocardial ischemia, metabolic diseases, and chronic heart and kidney diseases, and in reproductive diseases such as preeclampsia and endometriosis. This review article will summarize current understandings regarding the molecular mechanism of hypoxia in these common and important diseases.

DUSP2 regulates extracellular vesicle-VEGF-C secretion and pancreatic cancer early dissemination.

Early dissemination is a unique characteristic and a detrimental process of pancreatic ductal adenocarcinoma (PDAC); however, the underlying mechanism remains largely unknown. Here, we investigate the role of dual-specificity phosphatase-2 (DUSP2)-vascular endothelial growth factor-C (VEGF-C) axis in mediating PDAC lymphangiogenesis and lymphovascular invasion. Expression of DUSP2 is greatly suppressed in PDAC, which results in increased aberrant expression of extracellular vesicle (EV)-associated VEGF-C secretion. EV-VEGF-C exerts paracrine effects on lymphatic endothelial cells and autocrine effects on cancer cells, resulting in the lymphovascular invasion of cancer cells. Tissue-specific knockout of Dusp2 in mouse pancreas recapitulates PDAC phenotype and lymphovascular invasion. Mechanistically, loss-of-DUSP2 enhances proprotein convertase activity and vesicle trafficking to promote the release of the mature form of EV-VEGF-C. Collectively, these findings represent a conceptual advance in understanding pancreatic cancer lymphovascular invasion and suggest that loss-of-DUSP2-mediated VEGF-C processing may play important roles in early dissemination of pancreatic cancer. Abbreviations: DUSP2: dual-specificity phosphatase-2; VEGF-C: vascular endothelial growth factor-C; EV: extracellular vesicles; PDAC: pancreatic ductal adenocarcinoma; KD: knockdown.

Scaffold Hopping-Driven Optimization of 4-(Quinazolin-4-yl)-3,4-dihydroquinoxalin-2(1H)-ones as Novel Tubulin Inhibitors.

Scaffold hopping-driven lead optimizations were performed based on our prior lead 7-methoxy-4-(2-methylquinazolin-4-yl)-3,4-dihydroquinoxalin-2(1H)-one (2a) by C-ring expansion and isometric replacement of the A/B-ring, successively, aimed at finding new potential alternative drug candidates with different scaffold(s), high antitumor activity, and other improved properties to replace prior, once promising drug candidates that failed in further studies. Two series of new compounds 7 (a-d) and 13 (a-j) were synthesized and evaluated for antitumor activity, leading to the discovery of three highly potent compounds 13c, 13d, and 13e with different scaffolds. They exhibited similar high antitumor activity with single digital low nanomolar GI50 values (4.6-9.6 nM) in cellular assays, comparable to lead 2a, clinical drug candidate CA-4, and paclitaxel in the same assays. Further biological evaluations identified new active compounds as tubulin polymerization inhibitors targeting the colchicine binding site. Moreover, 13d showed better aqueous solubility than 2a and a similar log P value.

Studies of Coumarin Derivatives for Constitutive Androstane Receptor (CAR) Activation.

Constitutive androstane receptor (CAR) activation has found to ameliorate diabetes in animal models. However, no CAR agonists are available clinically. Therefore, a safe and effective CAR activator would be an alternative option. In this study, sixty courmarin derivatives either synthesized or purified from Artemisia capillaris were screened for CAR activation activity. Chemical modifications were on position 5,6,7,8 with mono-, di-, tri-, or tetra-substitutions. Among all the compounds subjected for in vitro CAR activation screening, 6,7-diprenoxycoumarin was the most effective and was selected for further preclinical studies. Chemical modification on the 6 position and unsaturated chains were generally beneficial. Electron-withdrawn groups as well as long unsaturated chains were hazardous to the activity. Mechanism of action studies showed that CAR activation of 6,7-diprenoxycoumarin might be through the inhibition of EGFR signaling and upregulating PP2Ac methylation. To sum up, modification mimicking natural occurring coumarins shed light on CAR studies and the established screening system provides a rapid method for the discovery and development of CAR activators. In addition, one CAR activator, scoparone, did showed anti-diabetes effect in db/db mice without elevation of insulin levels.

Design, synthesis and evaluation of antiproliferative activity of fluorinated betulinic acid.

Betulinic acid (BA), a pentacyclic triterpenoid, exhibits broad spectrum antiproliferative activity, but generally with only modest potency. To improve BA's pharmacological properties, fluorine was introduced as a single atom at C-2, creating two diastereomers, or in a trifluoromethyl group at C-3. We evaluated the impact of these groups on antiproliferative activity against five human tumor cell lines. A racemic 2-F-BA (compound 6) showed significantly improved antiproliferative activity, while each diastereomer exhibited similar effects. We also demonstrated that 2-F-BA is a topoisomerase (Topo) I and IIα dual inhibitor in cell-based and cell-free assays. A hypothetical mode of binding to the Topo I-DNA suggested a difference between the hydrogen bonding of BA and 2-F-BA to DNA, which may account for the difference in bioactivity against Topo I.

Antiproliferative Aspidosperma-Type Monoterpenoid Indole Alkaloids from Bousigonia mekongensis Inhibit Tubulin Polymerization.

Monoterpenoid indole alkaloids are structurally diverse natural products found in plants of the family Apocynaceae. Among them, vincristine and its derivatives are well known for their anticancer activity. Bousigonia mekongensis, a species in this family, contains various monoterpenoid indole alkaloids. In the current study, fourteen known aspidosperma-type monoterpenoid indole alkaloids (1⁻14) were isolated and identified from a methanol extract of the twigs and leaves of B. mekongensis for the first time. Among them, compounds 3, 6, 9, and 13 exhibited similar antiproliferative activity spectra against A549, KB, and multidrug-resistant (MDR) KB subline KB-VIN cells with IC50 values ranging from 0.5⁻0.9 µM. The above alkaloids efficiently induced cell cycle arrest at the G2/M phase by inhibiting tubulin polymerization as well as mitotic bipolar spindle formation. Computer modeling studies indicated that compound 7 likely forms a hydrogen bond (H-bond) with α- or ß-tubulin at the colchicine site. Evaluation of the antiproliferative effects and SAR analysis suggested that a 14,15-double bond or 3α-acetonyl group is critical for enhanced antiproliferative activity. Mechanism of action studies demonstrated for the first time that compounds 3, 4, 6, 7, and 13 efficiently induce cell cycle arrest at G2/M by inhibiting tubulin polymerization by binding to the colchicine site.

Shear-Induced CCN1 Promotes Atheroprone Endothelial Phenotypes and Atherosclerosis.

BACKGROUND: Atherosclerosis occurs preferentially at the blood vessels encountering blood flow turbulence. The matricellular protein CCN1 is induced in endothelial cells by disturbed flow, and is expressed in advanced atherosclerotic lesions in patients and in the Apoe-/- mouse model. The role of CCN1 in atherosclerosis remains undefined. METHODS: To assess the function of CCN1 in vivo, knock-in mice carrying the integrin α6ß1-binding-defective mutant allele Ccn1-dm on the Apoe-/- background were tested in an atherosclerosis model generated by carotid artery ligation. Additionally, CCN1-regulated functional phenotypes of human umbilical vein endothelial cells, or primary mouse aortic endothelial cells isolated from wild-type and Ccn1 dm/dm mice, were investigated in the in vitro shear stress experiments under unidirectional laminar shear stress (12 dyn/cm2) versus oscillatory shear stress (±5 dyn/cm2) conditions. RESULTS: We found that Ccn1 expression was upregulated in the arterial endothelium 3 days after ligation before any detectable structural changes, and intensified with the progression of atherosclerotic lesions. Compared with Apoe-/- controls, Ccn1 dm/dm/ Apoe-/- mice were remarkably resistant to ligation-induced plaque formation (n=6). These mice exhibited lower oxidative stress, expression of endothelin-1 and monocyte chemoattractant protein-1, and monocyte homing. CCN1/α6ß1 critically mediated flow-induced activation of the pleiotropic transcription factor nuclear factor-κB and therefore the induction of atheroprone gene expression in the mouse arterial endothelium after ligation (n=6), or in cultured human umbilical vein endothelial cells or primary mouse aortic endothelial cells exposed to oscillatory shear stress (n=3 in triplicate). Interestingly, the activation of nuclear factor-κB by CCN1/α6ß1 signaling prompted more production of CCN1 and α6ß1. Blocking CCN1-α6ß1 binding by the Ccn1-dm mutation or by T1 peptide (derived from an α6ß1-binding sequence of CCN1) disrupted the positive-feedback regulation between CCN1/α6ß1 and nuclear factor-κB, and prevented flow-induced atheroprone phenotypic alterations in endothelial cells or atherosclerosis in mice. CONCLUSIONS: These data demonstrate a causative role of CCN1 in atherosclerosis via modulating endothelial phenotypes. CCN1 binds to its receptor integrin α6ß1 to activate nuclear factor-κB, thereby instigating a vicious circle to persistently promote atherogenesis. T1, a peptide antagonist selectively targeting CCN1-α6ß1, can be further optimized for developing T1-mimetics to treat atherosclerosis.

TYRO3: A potential therapeutic target in cancer.

IMPACT STATEMENT: Cancer is among the leading causes of death worldwide. In 2016, 8.9 million people are estimated to have died from various forms of cancer. The current treatments, including surgery with chemotherapy and/or radiation therapy, are not effective enough to provide full protection from cancer, which highlights the need for developing novel therapy strategies. In this review, we summarize the molecular biology of a unique member of a subfamily of receptor tyrosine kinase, TYRO3 and discuss the new insights in TYRO3-targeted treatment for cancer therapy.

Development of novel amino-quinoline-5,8-dione derivatives as NAD(P)H:quinone oxidoreductase 1 (NQO1) inhibitors with potent antiproliferative activities.

Fourteen novel amino-quinoline-5,8-dione derivatives (6a-h and 7a-h) were designed and synthesized by coupling different alkyl- or aryl-amino fragments at the C6- or C7-position of quinoline-5,8-dione. All target compounds showed antiproliferative potency in the low micromolar range in both drug sensitive HeLaS3 and multidrug resistant KB-vin cell lines. Compounds 6h, 6d, 7a, and 7d exhibited more potent antiproliferative effects than the other compounds. Especially, compounds 6d and 7d displayed NQO1-dependent cytotoxicity and competitive NQO1 inhibitory effects in both drug sensitive HeLaS3 and multidrug resistant KB-vin cell lines. Furthermore, compounds 6h, 6d, 7a, and 7d induced a dose-dependent lethal mitochondrial dysfunction in both drug sensitive HeLaS3 and multidrug resistant KB-vin cells by increasing intracellular reactive oxygen species (ROS) levels. Notably, compound 7d selectively inhibited cancer cells, but not non-tumor liver cell proliferation in vitro, and significantly triggered HeLaS3 cell apoptosis by regulating apoptotic proteins of Bcl-2, Bax, and cleaved caspase-3 in a dose-dependent manner. Our findings suggest that these novel C6- or C7-substituted amino-quinoline-5,8-dione derivatives, such as 7d, could be further developed in the future as potent and selective antitumor agents to potentially circumvent multi-drug resistance (MDR).

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

BACKGROUND: The 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 DESIGN: Five 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. METHODS: An 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. RESULTS: Compound 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. CONCLUSION: Analysis 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.

Design, semisynthesis and potent cytotoxic activity of novel 10-fluorocamptothecin derivatives.

Fluorination is a well-known strategy for improving the bioavailability of bioactive molecules in the lead optimization phase of drug discovery projects. In an attempt to improve the antitumor activity of camptothecins (CPTs), novel 10-fluoro-CPT derivatives were designed, synthesized and evaluated for cytotoxicity against five human cancer cell lines (A-549, MDA-MB-231, KB, KB-VIN and MCF-7). All of the derivatives showed more potent in vitro cytotoxic activity than the clinical CPT-derived drug irinotecan against the tumor cell lines tested, and most of them showed comparable or superior potency to topotecan. Remarkably, compounds 16b (IC50, 67.0nM) and 19b (IC50, 99.2nM) displayed the highest cytotoxicity against the multidrug-resistant (MDR) KB-VIN cell line and merit further development as preclinical drug candidates for treating cancer, including MDR phenotype. Our study suggested that incorporation of a fluorine atom into position 10 of CPT is an effective method for discovering new potent CPT derivatives.

In Vivo and Mechanistic Studies on Antitumor Lead 7-Methoxy-4-(2-methylquinazolin-4-yl)-3,4-dihydroquinoxalin-2(1H)-one and Its Modification as a Novel Class of Tubulin-Binding Tumor-Vascular Disrupting Agents.

7-Methoxy-4-(2-methylquinazolin-4-yl)-3,4-dihydroquinoxalin-2(1H)-one (2), a promising anticancer lead previously identified by us, inhibited tumor growth by 62% in mice at 1.0 mg/kg without obvious signs of toxicity. Moreover, compound 2 exhibited extremely high antiproliferative activity in the NIH-NCI 60 human tumor cell line panel, with low to sub-nanomolar GI50 values (10-10 M level). It also showed a suitable balance between aqueous solubility and lipophilicity, as well as moderate metabolic stability in vivo. Mechanistic studies using Mayer's hematoxylin and eosin and immunohistochemistry protocols on xenograft tumor tissues showed that 2 inhibited tumor cell proliferation, induced apoptosis, and disrupted tumor vasculature. Moreover, evaluation of new synthetic analogues (6a-6t) of 2 indicated that appropriate 2-substitution on the quinazoline ring could enhance antitumor activity and improve druglike properties. Compound 2 and its analogues with a 4-(2-methylquinazolin-4-yl)-3,4-dihydroquinoxalin-2(1H)-one scaffold thus represent a novel class of tubulin-binding tumor-vascular disrupting agents (tumor-VDAs) that target established blood vessels in tumors.