Oleanolic acid inhibits the activity of the multidrug resistance protein ABCC1 (MRP1) but not of the ABCB1 (P-glycoprotein): possible use in cancer chemotherapy

Functionalized chitosan for cancer nano drug delivery

Chitosan is a biotechnological derivative of chitin receiving a widespread pharmaceutical and biomedical applications. It can be used to encapsulate and deliver cancer therapeutics with inherent pH-dependent solubility to confer drug targeting at tumour microenvironment and anti-cancer activity synergizing cancer cytotoxic drug actions. To further reduce the off-target and by-stander adverse effects of drugs, a high targeted drug delivery efficiency at the lowest possible drug doses is clinically required. The chitosan has been functionalized with covalent conjugates or complexes and processed into nanoparticles to encapsulate and control drug release, to avoid premature drug clearance, to deliver drugs passively and actively to cancer site at tissue, cell or subcellular levels, and to promote cancer cell uptake of nanoparticles through membrane permeabilization at higher specificity and scale. Nanomedicine developed using functionalized chitosan translates to significant preclinical improvements. Future challenges related to nanotoxicity, manufacturability, selection precision of conjugates and complexes as a function of cancer omics and their biological responses from administration site to cancer target need critical assessments.

Natural Products as a Tool to Modulate the Activity and Expression of Multidrug Resistance Proteins of Intestinal Barrier

The role of intestinal barrier homeostasis in an individual’s general well-being has been widely addressed by the scientific community. Colorectal cancer is among the illnesses that most affect this biological barrier. While chemotherapy is the first choice to treat this type of cancer, multidrug resistance (MDR) is the major setback against the commonly used drugs, with the ATP-binding cassette transporters (ABC transporters) being the major players. The role of P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), or breast cancer resistance protein (ABCG2) in the efflux of chemotherapeutic drugs is well described in cancer cells, highlighting these proteins as interesting druggable targets to reverse MDR, decrease drug dosage, and consequently undesired toxicity. Natural products, especially phytochemicals, have a wide diversity of chemical structures, and some particular classes, such as phenolic acids, flavonoids, or pentacyclic triterpenoids, have been reported as inhibitors of P-gp, MRP1, and ABCG2, being able to sensitize cancer cells to chemotherapy drugs. Nevertheless, ABC transporters play a vital role in the cell’s defense against xenobiotics, and some phytochemicals have also been shown to induce the transporters’ activity. A balance must be obtained between xenobiotic efflux in non-tumor cells and bioaccumulation of chemotherapy drugs in cancer cells, in which ABC transporters are essential and natural products play a pivotal role that must be further analyzed. This review summarizes the knowledge concerning the nomenclature and function of ABC-transporters, emphasizing their role in the intestinal barrier cells. In addition, it also focuses on the role of natural products commonly found in food products, e.g., phytochemicals, as modulators of ABC-transporter activity and expression, which are promising nutraceutical molecules to formulate new drug combinations to overcome multidrug resistance.

Decrease of ABCB1 protein expression and increase of G1 phase arrest induced by oleanolic acid in human multidrug-resistant cancer cells

Oleanolic acid (OA) is a natural compound that can be found in a number of edible and medicinal plants and confers diverse biological actions. However, the direct target of OA in human tumor cells remains poorly understood, preventing its application in clinical and health settings. A previous study revealed that overexpression of caveolin-1 in human leukemia HL-60 cells can increase its sensitivity to OA. The present study aimed to investigate the effects of OA on the doxorubicin-resistant human breast cancer MCF-7 cell line (MCF-7/DOX), harringtonine-resistant human leukemia HL-60 cells (HL-60/HAR) and their corresponding parental cell lines. Western blotting was performed to measure protein expression levels, whilst Cell Counting Kit-8 (CCK-8) assays, cell cycle analysis (by flow cytometry) and apoptosis assays (with Annexin V/PI staining) were used to assess drug sensitivity. CCK-8 assay results suggested that MCF-7/DOX cells, which overexpress the caveolin-1 protein, have similar OA susceptibility to their parent line. In addition, sensitivity of MCF-7/DOX cells to OA was not augmented by knocking down caveolin-1 using RNA interference. HL-60/HAR cells exhibited a four-fold increased sensitivity to OA compared with that in their parental HL-60 cells according to CCK-8 assay. Both of the resistant cell lines exhibited higher numbers of cells at G₁ phase arrest compared with those in their parent lines, as measured via flow cytometry. Treatment of both MCF-7 cell lines with 100 µM OA for 48 h induced apoptosis, with increased effects observed in resistant cells. However, no PARP-1 or caspase-3 cleavage was observed, with some positive Annexin V staining found after HL-60/HAR cells were treated with OA, suggesting that cell death occurred via non-classical apoptosis or through other cell death pathways. It was found that OA was not a substrate of ATP-binding cassette subfamily B member 1 (ABCB1) in drug-resistant cells, as indicated by the accumulation of rhodamine 123 assessed using flow cytometry. However, protein expression of ABCB1 in both of the resistant cell lines was significantly decreased after treatment with OA in a concentration-dependent manner. Collectively, these results suggest that OA could reduce ABCB1 protein expression and induce G₁ phase arrest in multidrug-resistant cancer cells. These findings highlight the potential of OA for cancer therapy.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

P. Cardoso D, U. Ferreira MJ. Overcoming Multidrug Resistance: Flavonoid and Terpenoid Nitrogen-Containing Derivatives as ABC Transporter Modulators

Multidrug resistance (MDR) in cancer is one of the main limitations for chemotherapy success. Numerous mechanisms are behind the MDR phenomenon wherein the overexpression of the ATP-binding cassette (ABC) transporter proteins P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance protein 1 (MRP1) is highlighted as a prime factor. Natural product-derived compounds are being addressed as promising ABC transporter modulators to tackle MDR. Flavonoids and terpenoids have been extensively explored in this field as mono or dual modulators of these efflux pumps. Nitrogen-bearing moieties on these scaffolds were proved to influence the modulation of ABC transporters efflux function. This review highlights the potential of semisynthetic nitrogen-containing flavonoid and terpenoid derivatives as candidates for the design of effective MDR reversers. A brief introduction concerning the major role of efflux pumps in multidrug resistance, the potential of natural product-derived compounds in MDR reversal, namely natural flavonoid and terpenoids, and the effect of the introduction of nitrogen-containing groups are provided. The main modifications that have been performed during last few years to generate flavonoid and terpenoid derivatives, bearing nitrogen moieties, such as aliphatic, aromatic and heterocycle amine, amide, and related functional groups, as well as their P-gp, MRP1 and BCRP inhibitory activities are reviewed and discussed.

Olean-28,13b-olide 2 plays a role in cisplatin-mediated apoptosis and reverses cisplatin resistance in human lung cancer through multiple signaling pathways

Lung cancer, similar to other chronic diseases, occurs due to perturbations in multiple signaling pathways. Mono-targeted therapies are not ideal since they are not likely to be effective for the treatment and prevention of lung cancer, and are often associated with drug resistance. Therefore, the development of multi-targeted agents is required for novel lung cancer therapies. Thioredoxin reductase (TrxR or TXNRD1) is a pivotal component of the thioredoxin (Trx) system. Various types of tumor cells are able to overexpress TrxR/Trx proteins in order to maintain tumor survival, and this overexpression has been shown to be associated with clinical outcomes, including irradiation and drug resistance. Emerging evidence has indicated that oleanolic acid (OA) and its derivatives exhibit potent anticancer activity, and are able to overcome drug resistance in cancer cell lines. In the present study, it was demonstrated that a novel synthesized OA family compound, olean-28,13b-olide 2 (OLO-2), synergistically enhanced cisplatin (CDDP)-mediated apoptosis, led to the activation of caspase-3 and the generation of reactive oxygen species (ROS), induced DNA damage, and inhibited the activation of the extracellular-signal-regulated kinase (ERK), signal transducer and activator of transcription 3 (STAT3), AKT and nuclear factor-κB (NF-κB) pathways in human multidrug-resistant A549/CDDP lung adenocarcinoma cells. Subsequent analyses revealed that OLO-2 inhibited P-glycoprotein (P-gp or ABCB1) and TrxR by reducing their expression at the protein and mRNA levels, and by suppressing P-gp ATPase and TrxR activities. Further biological evaluation indicated that OLO-2 significantly reduced Trx and excision repair cross-complementary1 (ERCC1) protein expression and significantly inhibited the proliferation of drug-sensitive (A549) and multidrug-resistant (A549/CDDP) non-small cell lung cancer (NSCLC) cells, but had no effect on non-tumor lung epithelial-like cells. In addition, the present study demonstrated, for the first time, to the best of our knowledge, that overexpressing or knocking down TrxR in NSCLC cells enhanced or attenuated, respectively, the resistance of NSCLC cells against CDDP, which indicated that TrxR plays an important role in CDDP resistance and functions as a protector of NSCLC against chemotherapeutic drugs. OLO-2 treatment also exhibited up to 4.6-fold selectivity against human lung adenocarcinoma cells. Taken together, the results of the present study shed light on the drug resistance-reversing effects of OLO-2 in lung cancer cells.

Cytotoxic Effects of Pinnatane A Extracted from Walsura pinnata (Meliaceae) on Human Liver Cancer Cells

BACKGROUND

Pinnatane A from the bark of Walsura pinnata was investigated for its anti-cancer properties by analyzing the cytotoxic activities and cell cycle arrest mechanism induced in two different liver cancer cell lines.

METHODS

A 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to analyze the pinnatane A selectivity in inducing cell death in cancer and normal cells. Various biological assays were carried out to analyze the anti-cancer properties of pinnatane A, such as a live/dead assay for cell death microscopic visualization, cell cycle analysis using propidium iodide (PI) to identify the cell cycle arrest phase, annexin V-fluorescein isothiocyanate (annexin V-FITC)/PI flow cytometry assay to measure percentage of cell populations at different stages of apoptosis and necrosis, and DNA fragmentation assay to verify the late stage of apoptosis.

RESULTS

The MTT assay identified pinnatane A prominent dose- and time-dependent cytotoxicity effects in Hep3B and HepG2 cells, with minimal effect on normal cells. The live/dead assay showed significant cell death, while cell cycle analysis showed arrest at the G₀/G₁ phase in both cell lines. Annexin V-FITC/PI flow cytometry and DNA fragmentation assays identified apoptotic cell death in Hep3B and necrotic cell death in HepG2 cell lines.

CONCLUSIONS

Pinnatane A has the potential for further development as a chemotherapeutic agent prominently against human liver cells.

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

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

Oleanolic Acid Alters Multiple Cell Signaling Pathways: Implication in Cancer Prevention and Therapy

Nowadays, much attention has been paid to diet and dietary supplements as a cost-effective therapeutic strategy for prevention and treatment of a myriad of chronic and degenerative diseases. Rapidly accumulating scientific evidence achieved through high-throughput technologies has greatly expanded the understanding about the multifaceted nature of cancer. Increasingly, it is being realized that deregulation of spatio-temporally controlled intracellular signaling cascades plays a contributory role in the onset and progression of cancer. Therefore, targeting regulators of oncogenic signaling cascades is essential to prevent and treat cancer. A plethora of preclinical and epidemiological evidences showed promising role of phytochemicals against several types of cancer. Oleanolic acid, a common pentacyclic triterpenoid, is mainly found in olive oil, as well as several plant species. It is a potent inhibitor of cellular inflammatory process and a well-known inducer of phase 2 xenobiotic biotransformation enzymes. Main molecular mechanisms underlying anticancer effects of oleanolic acid are mediated by caspases, 5' adenosine monophosphate-activated protein kinase, extracellular signal-regulated kinase 1/2, matrix metalloproteinases, pro-apoptotic Bax and bid, phosphatidylinositide 3-kinase/Akt1/mechanistic target of rapamycin, reactive oxygen species/apoptosis signal-regulating kinase 1/p38 mitogen-activated protein kinase, nuclear factor-κB, cluster of differentiation 1, CKD4, s6k, signal transducer and activator of transcription 3, as well as aforementioned signaling pathways . In this work, we critically review the scientific literature on the molecular targets of oleanolic acid implicated in the prevention and treatment of several types of cancer. We also discuss chemical aspects, natural sources, bioavailability, and safety of this bioactive phytochemical.

Synthesis of CDDO-amino acid-nitric oxide donor trihybrids as potential antitumor agents against both drug-sensitive and drug-resistant colon cancer

Seventeen CDDO-amino acid-NO donor trihybrids (4a-q) were designed and synthesized. Biological evaluation indicated that the most active compound 4c produced high levels of NO and inhibited the proliferation of drug-sensitive (HCT-8, IC50 = 0.294 μM) and drug-resistant (HCT-8/5-FU, IC50 = 0.232 μM) colon cancer cells, which were attenuated by an NO scavenger or typical substrate of PepT1. Furthermore, 4c triggered HCT-8 and HCT-8/5-FU cell apoptosis more strongly than CDDO-Me, inhibited the HIF-1α, Stat3, AKT, and ERK signaling, and induced the nitration of P-gp, MRP1, and BCRP proteins in HCT-8/5-FU cells. Finally, 4c had 4.36-5.53-fold less inhibitory activity against nontumor colon epithelial-like cells (CCD841, IC50 = 1.282 μM) in vitro and inhibited the growth of implanted human drug-resistant colon cancers in mice more potently than CDDO-Me. Together, 4c is a novel trihybrid with potent antitumor activity and may be a promising candidate for the treatment of drug-resistant colon cancer.

3β-Acetyl tormentic acid reverts MRP1/ABCC1 mediated cancer resistance through modulation of intracellular levels of GSH and inhibition of GST activity

ABC transporter overexpression is an important mechanism of multidrug resistance (MDR) and one of the main obstacles to successful cancer treatment. As these proteins actively remove chemotherapeutics from the tumor cells, the pharmacological inhibition of their activity is a possible strategy to revert drug resistance. Moreover, the ability of MDR inhibitors to sensitize resistant cells to conventional drugs is important for their clinical use. Evidence has shown that the multidrug resistance protein 1 (MRP1/ABCC1) is a negative prognostic marker in patients with lung, gastric, or breast cancers or neuroblastoma. Previous data have shown that 3β-acetyl tormentic acid (3ATA) inhibits the transport activity of the protein MRP1/ABCC1. In this study, we evaluated the ability of 3ATA to sensitize an MDR cell line (GLC4/ADR), which overexpresses MRP1, and investigated the anti-MRP1 mechanisms activated by 3ATA. The results showed that 3ATA is able to reverse the resistance of the MDR cell line to doxorubicin and vincristine, two drugs that are commonly used in cancer chemotherapy. Regarding the sensitizing mechanism induced by 3ATA, this work shows that the triterpene does not modulate the expression of MRP1/ABCC1 but is able to reduce total intracellular glutathione (GSH) levels and decrease the activity of glutathione-s-transferase (GST), the enzyme responsible for the glutathione conjugation of xenobiotics. Together, these results show that 3ATA sensitizes the MDR cell line overexpressing MRP1/ABCC1 to antineoplastic drugs and that this effect is mediated by the modulation of intracellular levels of GSH and GST activity.

3-Methyladenine can depress drug efflux transporters via blocking the PI3K-AKT-mTOR pathway thus sensitizing MDR cancer to chemotherapy

Multi-drug resistance (MDR) cancer is an intractable problem. Over-expression of drug efflux transporters such as ABCB1, ABCC1 and ABCG2 contributes to it, by which they pump drugs out of cells, and result in the decrease in the efficacy of chemotherapy. To reverse the cancer MDR, we used 3-methyladenine (3-MA) treatment on taxol or doxorubicin stressed MDR cell lines A2780DX5 and SGC7091R and xeno-tumor implanted mice. The results indicate that ABCB1, ABCC1 and ABCG2 were depressed, and the PI3K-AKT-mTOR pathway was blocked. Moreover, using FITC-labeled taxol as the indicator, we observed that the drug accumulation was enhanced in MDR cells and more cells were killed after 3-MA administration. Thus suggesting that 3-MA can reverse cancer MDR via depressing agent-efflux transporters.

Recent advances in synthesis and biological activity of triterpenic acylated oximes

During the last few decades more and more attention has been paid to triterpenes-a group of compounds with five- or four-ring skeleton and carboxyl, hydroxyl or oxo groups. Triterpenes with unsubstituted C-3 hydroxyl group can be easily transformed into appropriate ketones and then into oximes. The carbonyl group can be created not only from the hydroxyl group at C-3 position, but also at C-2, C-12 or C-28 positions. Several methods of creation of two = NOH groups within one molecule of triterpene are known. There are also known triterpenes with two carbonyl groups, e.g. at C-3 and C-11 positions, which differ in reactivity: among them only C-3 group can be transformed into oxime. A reactive hydroxyimine group can undergo the action of acylating agents, such as carboxylic acids or their derivatives, also the ones with significant pharmacological activity. Acyl derivatives of triterpenic oximes exhibit important pharmacological activity. The biological tests performed with the use of cell cultures inoculated with viruses showed inhibitory activity of some triterpenic acyloximes against type 1 HSV (H7N1), ECHO-6 and HIV-1 viruses. Another acylated oximes derived from triterpenes shown cytotoxic or antiproliferative activity against many lines of cancer cells. In many cases the pharmacological effects of the tested acyloxyiminotriterpenes were comparable to those of appropriate standard drugs. One of the newest application of acyl derivatives of triterpenic oximes is their ability to form organogels.

Synthesis and cytotoxicity evaluation of oleanolic acid derivatives

Twelve derivatives of oleanolic acid (1) have been synthesized and evaluated for their inhibitory activities against the growth of prostate PC3, breast MCF-7, lung A549, and gastric BGC-823 cancer cells by MTT assays. Within these series of derivatives, compound 17 exhibited the most potent cytotoxicity against PC3 cell line (IC50=0.39 μM) and compound 28 displayed the best activity against A549 cell line (IC50=0.22 μM). SAR analysis indicates that H-donor substitution at C-3 position of oleanolic acid may be advantageous for improvement of cytotoxicity against PC3, A549 and MCF-7 cell lines.

Oleanolic acid derivative methyl 3,11-dioxoolean-12-en-28-olate targets multidrug resistance related to ABCB1

Multidrug resistance (MDR) in leukemia patients is a great incentive to the development of new drugs. In a search for potential multidrug resistance modulators we tested a group of oleanolic acid (OA) analogues modified at C-3, C-11, C-12 and C-28 using an experimental model consisting of three human acute lymphoblastic leukemia cell lines (CCRF-CEM and the multidrug resistant sublines CCRF-VCR1000 and CCRF-ADR5000). The most effective compound, methyl 3,11-dioxoolean-12-en-28-olate (DIOXOL) was more potent in cell viability inhibition than its precursor - OA, and showed similar or even higher activity in the drug resistant than in the wild-type cells. Resistance factor (RF) values obtained for CCRF-VCR1000 and CCRF-ADR-5000 cells using MTT assay were 0.7 and 0.8 (24 h of treatment) and after 72 h of treatment 0.9 and 1.1, respectively. Moreover, 5 μM DIOXOL significantly reduced the expression of the ABCB1 gene in MDR cells by around 30%, and also decreased the level of P-gp protein. Compared to untreated control cells, DIOXOL treatment resulted in a significant P-gp decrease (30% in CCRF-ADR5000 and 50% in CCRF-VCR1000), that was detected by western blot and confirmed by flow cytometry analysis. Moreover, DIOXOL (at 10 μM) significantly inhibited P-gp transport function by more than twofold comparing to control, untreated cells that was demonstrated using rhodamine 123-based functional test. The compound exhibited synergistic activity with ABCB1 substrate - adriamycin in CCRF-VCR1000 cells, indicating partial but significant MDR reversing ability.

Effects of 3β-acethyl tormentic acid (3ATA) on ABCC proteins activity

Multidrug resistance (MDR) is considered the main cause of cancer chemotherapy failure and patient relapse. The active drug efflux mediated by transporter proteins of the ABC (ATP-binding cassette) family is the most investigated mechanism leading to MDR. With the aim of inhibiting this transport and circumventing MDR, a great amount of work has been dedicated to identifying pharmacological inhibitors of specific ABC transporters. We recently showed that 3β-acetyl tormentic acid (3ATA) had no effect on P-gp/ABCB1 activity. Herein, we show that 3ATA strongly inhibited the activity of MRP1/ABCC1. In the B16/F10 and Ma104 cell lines, this effect was either 20X higher or similar to that observed with MK571, respectively. Nevertheless, the low inhibitory effect of 3ATA on A549, a cell line that expresses MRP1-5, suggests that it may not inhibit other MRPs. The use of cells transfected with ABCC2, ABCC3 or ABCC4 showed that 3ATA was also able to modulate these transporters, though with an inhibition ratio lower than that observed for MRP1/ABCC1. These data point to 3ATA as a new ABCC inhibitor and call attention to its potential use as a tool to investigate the function of MRP/ABCC proteins or as a co-adjuvant in the treatment of MDR tumors.

Oleanolic acid initiates apoptosis in non-small cell lung cancer cell lines and reduces metastasis of a B16F10 melanoma model in vivo

Background

Drug resistance, a process mediated by multiple mechanisms, is a critical determinant for treating lung cancer. The aim of this study is to determine if oleanolic acid (OA), a pentacyclic triterpene present in several plants, is able to circumvent the mechanisms of drug resistance present in non-small cell lung cancer (NSCLC) cell lines and to induce their death.

Principal Findings

OA decreased the cell viability of the NSCLC cell lines A459 and H460 despite the presence of active, multidrug-resistant (MDR) MRP1/ABCC1 proteins and the anti-apoptotic proteins Bcl-2 and survivin. These effects are due to apoptosis, as evidenced by the capacity of OA to induce fragmentation of DNA and activate caspase 3. Induction of NSCLC cell death by OA cannot be explained by inhibition of the MDR proteins, since treatment with triterpene had little or no effect on the activity or expression of MRP1. Moreover, treatment with OA had no effect on the expression of the anti-apoptotic protein Bcl-2, but increased the expression of the pro-apoptotic protein Bax, altering the Bcl-2/Bax balance towards a pro-apoptotic profile. OA also decreased the expression of the anti-apoptotic protein survivin. Furthermore, OA decreased the expression of the angiogenic vascular endothelial growth factor (VEGF) and decreased the development of melanoma-induced lung metastasis.

Conclusion

Our data provide a significant insight into the antitumoral and antimetastatic activity of OA in NSCLC and suggest that including OA in the NSCLC regimens may help to decrease the number of relapses and reduce the development of metastases.

Uptake, transport and regulation of JBP485 by PEPT1 in vitro and in vivo

Cyclo-trans-4-L-hydroxyprolyl-L-serine (JBP485) is a dipeptide with anti-hepatitis activity that has been chemically synthesized. Previous experiments in rats showed that JBP485 was well absorbed by the intestine after oral administration. The human peptide transporter (PEPT1) is expressed in the intestine and recognizes compounds such as dipeptides and tripeptides. The purposes of this study were to determine if JBP485 acted as a substrate for intestinal PEPT1, and to investigate the characteristics of JBP485 uptake and transepithelial transport by PEPT1. The uptake of JBP485 was pH dependent in human intestinal epithelial cells Caco-2. And JBP485 uptake was also significantly inhibited by glycylsarcosine (Gly-Sar, a typical substrate for PEPT1 transporters), JBP923 (a derivative of JBP485), and cephalexin (CEX, a β-lactam antibiotic and a known substrate of PEPT1) in Caco-2 cells. The rate of apical-to-basolateral transepithelial transport of JBP485 was 1.84 times higher than that for basolateral-to-apical transport. JBP485 transport was obviously inhibited by Gly-Sar, JBP923 and CEX in Caco-2 cells. The uptake of JBP485 was increased by verapamil but not by cyclosporin A (CsA) and inhibited by the presence of Zn(2+) or the toxic metabolite of ethanol, acetaldehyde (AcH) in Caco-2 cells. The in vivo uptake of JBP485 was increased by verapamil and decreased by ethanol in vivo, which was consisted with the in vitro study. PEPT1 mRNA levels were enhanced after exposure of the cells to JBP485 for 24h, compared to control. In conclusion, JBP485 was actively transported by the intestinal oligopeptide transporter PEPT1. This mechanism is likely to contribute to the rapid absorption of JBP485 by the gastrointestinal tract after oral administration.

Optimization of microwave-assisted extraction followed by RP-HPLC for the simultaneous determination of oleanolic acid and ursolic acid in the fruits of Chaenomeles sinensis

An optimized microwave-assisted extraction (MAE) method and an efficient HPLC analysis method were developed for fast extraction and simultaneous determination of oleanolic acid and ursolic acid in the fruit of Chaenomeles sinensis. The open vessel MAE process was optimized by using a central composite experimental design. The optimal conditions identified were microwave power 600 W, temperature 52 degrees C, solvent to material ratio 32 mL/g and extraction time 7 min. The results showed that MAE is a more rapid extraction method with higher yield and lower solvent consumption. The HPLC-photodiode array detection analysis method was validated to have good linearity, precision, reproduction and accuracy. Compared with conventional extraction and analysis methods, MAE-HPLC-photodiode array detection is a faster, convenient and appropriate method for determination of oleanolic acid and ursolic acid in the fruits of C. sinensis.

Protective effect of oleanolic acid on gentamicin induced nephrotoxicity in rats

Oleanolic acid is a molecule of current therapeutic interest. In the present study, oleanolic acid isolated from the cuticular epithelium of Viscum articulatum Burm. f. (Viscaceae) was investigated for its protective effects on gentamicin-induced renal damage in rats. Nephrotoxicity was induced in rats by intraperitoneal injection of gentamicin at a dose of 100 mg/kg/day for 8 days. The effect of Oleanolic acid administered orally at doses 40, 60 and 80 mg/kg/day was assessed biochemically by determination of albumin, urea and creatinine in serum and urine samples and also through histopathological examination of the kidneys. Oleanolic acid protected the rat kidneys from gentamicin-induced nephrotoxicity as evident from a decrease in the serum and urine levels of creatinine, albumin and urea. Oleanolic acid also protected the rat kidneys from histological alterations induced by gentamicin and also improved the glomerular filtration rate. Compared with an earlier report on intraperitoneal administration of oleanolic acid in paracetamol-induced nephrotoxicity in rats, the data show that orally administered oleanolic acid also exerted a nephroprotective effect even in the case of a nephrotoxicant such as gentamicin, which directly deteriorates the kidney function without prior metabolism.

Flow cytometric evaluation of multidrug resistance proteins

There are several ways to detect proteins on cells. One quite frequently used method is flow cytometry. This method needs fluorescently labeled antibodies that can attach selectively to the protein to be investigated for flow cytometric detection. Flow cytometry scans individual cells, virtually without their surrounding liquid, and can scan many cells in a very short time. Because of this advantage of flow cytometry, it was adapted to investigate transport proteins on normal and cancerous human cells and cell lines. These transport proteins play important roles in human metabolism. Absorption in the intestine, excretion at the kidney, protection of the CNS compartment and the fetus from xenobiotics, and other vital functions depend on these transporters. However, several transporters are overexpressed in cancer cells. These overexpressed transporters pump out anticancer drugs from the cells and prevent their curative effects. The detection and quantitation of these types of transporters in cancer cells is important for this reason. Here, we review literature on flow cytometric detection of the three most studied transporters: P-glycoprotein, multidrug resistance-associated proteins, and breast cancer resistance protein.

Oleanolic acid derivative Dex-OA has potent anti-tumor and anti-metastatic activity on osteosarcoma cells in vitro and in vivo

This study was undertaken to investigate the inhibitory effects of triterpenoid compound oleanolic acid and its synthetic derivatives on osteosarcoma cells in order to identify new therapeutic candidates for the treatment of this disease. We used the 3-(4,5-dimethyl-2 thiazolyl)-2,5-diphenyl tetrazolium bromide assay to assess the effect of oleanolic acid compounds on the proliferation of osteosarcoma cells. The effect of dextrose-oleanolic acid (the most potent oleanolic acid derivative) on apoptosis of osteosarcoma cells was evaluated using the Annexin-V method. The cell cycle of dextrose-oleanolic acid-treated cells was examined by flow cytometry, and the in vivo effects of dextrose-oleanolic acid were evaluated in a mouse osteosarcoma model. Oleanolic acid compounds had an overall inhibitory effect on the proliferation of osteosarcoma cells. Our in vitro data showed that the dextrose-oleanolic acid derivative brought about maximal inhibition of proliferation of osteosarcoma cells while inducing apoptosis. It could also inhibit the growth of osteosarcoma and decreased the rate of lung metastasis in vivo. Of the oleanolic acid derivatives, dextrose-oleanolic acid exhibited the most potent anti-osteosarcoma activity; it may represent a new frontier in the treatment of osteosarcoma.

Topological polar surface area defines substrate transport by multidrug resistance associated protein 1 (MRP1/ABCC1)

Multidrug resistance-associated protein 1 (MRP1/ABCC1) is a very promiscuous transporter. Herein we used topological polar surface area (TPSA), a descriptor defined as the sum of surfaces of polar atoms in a molecule, to analyze drug transport by MRP1. We suggested that compounds with high TPSA are transported while those with low TPSA are not. The conjugation to GSH increases TPSA values favoring transport. A strong correlation between TPSA and transport properties (K(m)) was also found.

Rapid and novel discrimination and quantification of oleanolic and ursolic acids in complex plant extracts using two-dimensional nuclear magnetic resonance spectroscopy-Comparison with HPLC methods

A novel strategy for NMR analysis of mixtures of oleanolic and ursolic acids that occur in natural products is described. These important phytochemicals have similar structure and their discrimination and quantification is rather difficult. We report herein the combined use of proton-carbon heteronuclear single-quantum coherence ((1)H-(13)C HSQC) and proton-carbon heteronuclear multiple-bond correlation ((1)H-(13)C HMBC) NMR spectroscopy, in the identification and quantitation of oleanolic acid (OA) and ursolic acid (UA)in plant extracts of the Lamiaceae and Oleaceae family. The combination of (1)H-(13)C HSQC and (1)H-(13)C HMBC techniques allows the connection of the proton and carbon-13 spins across the molecular backbone resulting in the identification and, thus, discrimination of oleanolic and ursolic acid without resorting to physicochemical separation of the components. The quantitative results provided by 2D (1)H-(13)C HSQC NMR data were obtained within a short period of time ( approximately 14min) and are in excellent agreement with those obtained by HPLC, which support the efficiency of the suggested methodology.

The adjuvant effects of Antrodia Camphorata extracts combined with anti-tumor agents on multidrug resistant human hepatoma cells

AIM OF THE STUDY

The objectives of this study were to investigate the adjuvant anti-tumor effects of Antrodia camphorate in human hepatoma cells (C3A and PLC/PRF/5) which are resistance to most anti-tumor agents, elucidate the possible regulation pathways, and measure the tumor growth and survival rate in xenograft-nude mice after combined with anti-tumor agents.

MATERIALS AND METHODS

The AC extracts were measured by using a phenol/sulfuric acid method as previously described. The in vitro cell proliferation assay of ACs and anti-tumor agents was tested on C3A and PLC/PRF/5 cell lines. The percentage of human hepatoma cells undergoing apoptosis and distributing in different phases of cell cycle were determined by Flow cytometric analysis. Western blot analysis for MDR-1 and apoptosis- related proteins. The measurements of tumor growth and survival analysis of hepatoma implanted nude mice treated with Antrodia camphorata extracts and anti-tumor agents alone or in combinations.

RESULTS

We have found that Antrodia camphorata extracts, when combined with anti-tumor agents, showed adjuvant antiproliferative effects on hepatoma cells (in vitro) and on xenografted cells in tumor-implanted nude mice (in vivo), which then extended their median survival days. Furthermore, solid-state extracts of Antrodia camphorata (AC-SS) showed its adjuvant effects through the inhibition of MDR gene expressions and the pathway of COX-2- dependent inhibition of p-AKT, which ultimately resulted in the induction of apoptosis in hepatoma cells.

CONCLUSIONS

In this study, we have found that Antrodia camphorata extract, when combined with anti-tumor agents, showed adjuvant antiproliferative effects on hepatoma cells (in vitro) and on xenografted cells in tumor-implanted nude mice (in vivo).

Natural triterpenoids from Cecropia lyratiloba are cytotoxic to both sensitive and multidrug resistant leukemia cell lines

The cytotoxicity of four triterpenoids, euscaphic acid (1), tormentic acid (2), 2alpha-acetyl tormentic acid (3), and 3beta-acetyl tormentic acid (4), isolated from the roots of Cecropia lyratiloba (Moraceae) by countercurrent chromatography, was evaluated in vitro in sensitive and multidrug resistant leukemia cell lines. A structure/activity relationship analysis of the compounds was performed. Acetylation of compound 2 at C2 increased its activity by a factor of 2 while acetylation at C3 had a smaller effect. Compound 1 induces death by activation of caspase-3, dependent apoptotic pathway. Furthermore, the four triterpenoids were also active toward a multidrug resistant (MDR) leukemia cell line, overexpressing glycoprotein-P (P-gp). These results reveal the potential of the terpenoids as source for the development of new anti-neoplastic and anti-MDR drugs.

Oleanolic acid induces apoptosis in human leukemia cells through caspase activation and poly(ADP-ribose) polymerase cleavage

It has been shown that Fructus Ligustri Lucidi (FLL), a promising traditional Chinese medicine, can inhibit the growth of tumors. However, the effective component and molecular mechanism of FLL act to inhibit tumor proliferation are unclear. In this study, we demonstrated that oleanolic acid (OA), a principal chemical component of FLL, inhibited the proliferation of human leukemia HL60 cells in culture. MTT assay showed that treatment of HL60 cells with FLL crude extracts or OA dramatically blocked the growth of target tumor cell in a time- and dose-dependent manner. Morphological changes of the nuclei and DNA fragmentation showed that apoptotic cell death occurred in the HL60 cells after treating with FLL extracts (20 mg/ml) or OA (3.65 x 10(-2) mg/ml). Furthermore, flow cytometry assay showed that treatment of HL60 cells with FLL or OA caused an increased accumulation of G(1) and sub-G(1) subpopulations. Western blot analysis showed that caspase-9 and caspase-3 were activated, accompanied by the cleavage of poly(ADP-ribose) polymerase (PARP) in the target cells during FLL- or OA-induced apoptosis. These results suggest that OA acts as the effective component of FLL by exerting its cytotoxicity towards target tumor cells through activation of caspases and cleavage of PARP.

Modulation of multidrug resistance protein (MRP1/ABCC1) expression: a novel physiological role for ouabain

Besides being a (Na(+),K(+))-ATPase inhibitor, high doses of the hormone ouabain have also been reported to modulate both the expression and activity of proteins belonging to the ATP binding cassette family of transporters, such as ABCC7 (CFTR), ABCB1 (P-glycoprotein), and ABCC1 (MRP1). Although these proteins are present in the kidney, only ABCB1 has a putative physiological role in this organ, secreting endobiotics and xenobiotics. In the present work, we studied the relationship between ouabain and ABCC1 expression and function, aiming to establish a physiological role for ouabain. It was observed that prolonged (24 h) but not short (30 min) incubation with 1 nmol/L or higher ouabain concentrations decreased the expression of ABCC1 protein and induced its mRNA expression. This decrease was rapidly reversible, reaching control levels after incubation of cells in ouabain-free medium for 3 h, denoting a hormonal action. Moreover, concentrations equal or higher than 100 nmol/L ouabain also induced impairment of ABCC1 activity, increasing the accumulation of carboxyfluorescein diacetate, an ABCC1 fluorescent substrate. Because ouabain is now accepted as an endogenous hormone, our results suggest that ABCC1 is regulated by hormones related to body volume control, which may have implications for the treatment of hypertensive cancer patients. Moreover, providing ABCC1 is expressed in several other tissues, such as brain, testis, and the immune system, and is related to the transport of glutathione, it is possible that ouabain release may control a number of functions within these organs and tissues by modulating both the expression and the activity of ABCC1.