Heleni Loutrari

Mastic oil from Pistacia lentiscus var. chia inhibits growth and survival of human K562 leukemia cells and attenuates angiogenesis.

Abstract: Mastic oil from Pistacia lentiscus var. chia, a natural plant extract traditionally used as a food additive, has been extensively studied for its antimicrobial activity attributed to the combination of its bioactive components. One of them, perillyl alcohol (POH), displays tumor chemopreventive, chemotherapeutic, and antiangiogenic properties. We investigated whether mastic oil would also suppress tumor cell growth and angiogenesis. We observed that mastic oil concentration and time dependently exerted an antiproliferative and proapoptotic effect on K562 human leukemia cells and inhibited the release of vascular endothelial growth factor (VEGF) from K562 and B16 mouse melanoma cells. Moreover, mastic oil caused a concentration-dependent inhibition of endothelial cell (EC) proliferation without affecting cell survival and a significant decrease of microvessel formation both in vitro and in vivo. Investigation of underlying mechanism(s) demonstrated that mastic oil reduced 1) in K562 cells the activation of extracellular signal–regulated kinases 1/2 (Erk1/2) known to control leukemia cell proliferation, survival, and VEGF secretion and 2) in EC the activation of RhoA, an essential regulator of neovessel organization. Overall, our results underscore that mastic oil, through its multiple effects on malignant cells and ECs, may be a useful natural dietary supplement for cancer prevention.

Zoledronic Acid Is Effective against Experimental Malignant Pleural Effusion

RATIONALE Aminobiphosphonates, such as zoledronic acid (ZA), exert potent indirect antitumor effects and are currently being tested against human solid tumors. The antitumor actions of aminobiphosphonates, including angiostasis, are relevant to the pathogenesis of malignant pleural effusion (MPE), but no study has addressed the efficacy of these compounds against malignant pleural disease. OBJECTIVES Here we hypothesized that treatment of immunocompetent mice with ZA would halt tumor progression in a mouse model of adenocarcinoma-induced MPE. METHODS To induce MPE in mice, Lewis lung carcinoma cells were delivered directly into the pleural space. Subsequently, animals were treated with ZA in both a prevention and a regression protocol. MEASUREMENTS AND MAIN RESULTS ZA treatment resulted in significant reductions in pleural fluid accumulation and tumor dissemination, while it significantly prolonged survival. These effects of ZA were linked to enhanced apoptosis of pleural tumor cells, decreased formation of new vessels in pleural tumors, and reduced pleural vascular permeability. In addition, ZA was able to inhibit the recruitment of mononuclear cells to pleural tumors, with concomitant reductions in matrix metalloproteinase-9 release into the pleural space. Finally, ZA limited the expression of proinflammatory and angiogenic mediators, as well as the activity of small GTP proteins Ras and RhoA, in tumor cells in vivo and in vitro. CONCLUSIONS ZA is effective against experimental MPE, suggesting that this intervention should be considered for testing in clinical trials.

Protective Effects of Mastic Oil From Pistacia Lentiscus Variation Chia Against Experimental Growth of Lewis Lung Carcinoma

Mastic oil from Pistacia lentiscus variation chia, a traditionally used dietary flavoring agent with medicinal properties, has been shown to exert in vitro antitumor activities, but no study has addressed in vivo efficacy and mechanisms of action. Presently, we demonstrated that treatment of immunocompetent mice with mastic oil (45 mg/kg body weight, intraperitoneally, 3 times a wk for ∼3 wk) significantly inhibited tumor growth (56.4% ± 5.7 maximum reduction in tumor volumes) without toxicity. Analysis of tumors by immunohistochemistry and ELISA indicated that this effect is associated with increased apoptosis, reduced neovascularization, and inhibition of chemokine expression. Likewise mastic oil reduced vascular endothelial growth factor and chemokine release by Lewis lung carcinoma (LLC) cells. Furthermore, mastic oil administration decreased small guanosine triphosphatases (GTPases) Ras, RhoA and nuclear factor-κ-B-dependent reporter gene expression in vivo and in vitro, indicating a mechanistic link between mastic oil activities and blocking of relevant signaling and transcription pathways. A dose-response comparison with perillyl alcohol and α-pinene, two of its components, revealed a higher efficacy of mastic oil, pointing to a beneficial collective interaction among its ingredients. Conclusively, our results provide novel in vivo evidence of mastic oil inhibitory effects on tumor growth and set a rational basis for its future application in cancer prevention.

A transcriptomic computational analysis of mastic oil-treated Lewis lung carcinomas reveals molecular mechanisms targeting tumor cell growth and survival.

BackgroundMastic oil from Pistacia lentiscus variation chia, a blend of bioactive terpenes with recognized medicinal properties, has been recently shown to exert anti-tumor growth activity through inhibition of cancer cell proliferation, survival, angiogenesis and inflammatory response. However, no studies have addressed its mechanisms of action at genome-wide gene expression level.MethodsTo investigate molecular mechanisms triggered by mastic oil, Lewis Lung Carcinoma cells were treated with mastic oil or DMSO and RNA was collected at five distinct time points (3-48 h). Microarray expression profiling was performed using Illumina mouse-6 v1 beadchips, followed by computational analysis. For a number of selected genes, RT-PCR validation was performed in LLC cells as well as in three human cancer cell lines of different origin (A549, HCT116, K562). PTEN specific inhibition by a bisperovanadium compound was applied to validate its contribution to mastic oil-mediated anti-tumor growth effects.ResultsIn this work we demonstrated that exposure of Lewis lung carcinomas to mastic oil caused a time-dependent alteration in the expression of 925 genes. GO analysis associated expression profiles with several biological processes and functions. Among them, modifications on cell cycle/proliferation, survival and NF-κB cascade in conjunction with concomitant regulation of genes encoding for PTEN, E2F7, HMOX1 (up-regulation) and NOD1 (down-regulation) indicated some important mechanistic links underlying the anti-proliferative, pro-apoptotic and anti-inflammatory effects of mastic oil. The expression profiles of Hmox1, Pten and E2f7 genes were similarly altered by mastic oil in the majority of test cancer cell lines. Inhibition of PTEN partially reversed mastic oil effects on tumor cell growth, indicating a multi-target mechanism of action. Finally, k-means clustering, organized the significant gene list in eight clusters demonstrating a similar expression profile. Promoter analysis in a representative cluster revealed shared putative cis-elements suggesting a common regulatory transcription mechanism.ConclusionsPresent results provide novel evidence on the molecular basis of tumor growth inhibition mediated by mastic oil and set a rational basis for application of genomics and bioinformatic methodologies in the screening of natural compounds with potential cancer chemopreventive activities.

Enzymatic transformation of flavonoids and terpenoids: Structural and functional diversity of the novel derivatives

Flavonoids and terpenoids are promising candidates for use as functional foods and novel therapeutics due to their prominent biological activities. However, the use of several bioactive plant compounds is limited by low stability and solubility problems. This review underlines the feasibility of enzymatic synthesis of novel bioactive analogs of selected flavonoids (silybin, rutin) and terpenoids (perillyl alcohol, POH) in nonconventional reaction systems. The effect of various parameters on the enzymatic acylation and/or glucosylation of these phytochemicals was studied. Also, the role of the structure of the novel molecules in relation to their biological function was investigated in various cancer cell lines.

The soluble guanylyl cyclase inhibitor NS-2028 reduces vascular endothelial growth factor-induced angiogenesis and permeability

Nitric oxide (NO) is known to promote vascular endothelial growth factor (VEGF)-stimulated permeability and angiogenesis. However, effector molecules that operate downstream of NO in this pathway remain poorly characterized. Herein, we determined the effect of soluble guanylyl cyclase (sGC) inhibition on VEGF responses in vitro and in vivo. Treatment of endothelial cells (EC) with VEGF stimulated eNOS phosphorylation and cGMP accumulation; pretreatment with the sGC inhibitor 4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one (NS-2028) blunted cGMP levels without affecting VEGF-receptor phosphorylation. Incubation of cells with NS-2028 blocked the mitogenic effects of VEGF. In addition, cells in which sGC was inhibited exhibited no migration and sprouting in response to VEGF. To study the mechanisms through which NS-2028 inhibits EC migration, we determined the effects of alterations in cGMP levels on p38 MAPK. Initially, we observed that inhibition of sGC attenuated VEGF-stimulated activation of p38. In contrast, the addition of 8-Br-cGMP to EC stimulated p38 phosphorylation. The addition of cGMP elevating agents (BAY 41-2272, DETA NO and YC-1) enhanced EC migration. To test whether sGC also mediated the angiogenic effects of VEGF in vivo, we used the rabbit cornea assay. Animals receiving NS-2028 orally displayed a reduced angiogenic response to VEGF. As increased vascular permeability occurs prior to new blood vessel formation, we determined the effect of NS-2028 in vascular leakage. Using a modified Miles assay, we observed that NS-2028 attenuated VEGF-induced permeability. Overall, we provide evidence that sGC mediates the angiogenic and permeability-promoting activities of VEGF, indicating the significance of sGC as a downstream effector of VEGF-triggered responses.

Enzymatic preparation of acylated derivatives of silybin in organic and ionic liquid media and evaluation of their antitumor proliferative activity

Biocatalytic preparation of acylated derivatives of silybin using several acyl donors (free fatty acids or their esters), catalyzed by immobilized Candida antarctica lipase B, was performed in various organic solvents as well as in imidazolium-based ionic liquids containing either or anions. Total conversion of silybin was achieved in acetone using short-chain acyl donors (vinyl butanoate) at a 10:1 molar ratio of acyl donor to silybin. The enzymatic process in ionic liquids depended strongly on the alkyl chain length of the cation as well the anion used. Higher conversion yields (up to 75.8%) and reaction rates (up to 0.31 mmol h−1 g−1 biocatalyst) were obtained in the as compared with - containing ionic liquids. The amounts of silybin ester formed in a one-step biocatalytic process were high (>40 g L−1) in both reaction media. The antiproliferative effect of acylated silybin derivatives on the growth of K562 human leukemia cells was estimated and compared with that of silybin.

Biocatalytic synthesis and antitumor activities of novel silybin acylated derivatives with dicarboxylic acids.

Novel silybin acylated derivatives with dicarboxylic acids were prepared in various organic solvents using immobilized Candida antarctica lipase B (Novozym 435(®)). The reaction parameters affecting the silybin conversion, such as the nature of the organic solvent and the acyl donor used were investigated. The antiproliferative effects of silybin monoesters, and their ability to modulate the secretion of vascular endothelial growth factor (VEGF) were estimated using K562 human lymphoblastoma cells and compared to the parental compound. The synthesized esters retained the biological function of silybin and in some cases were more effective, indicating that target biotransformation may generate novel compounds with improved antitumor and antiangiogenic activities.

Mastic oil inhibits the metastatic phenotype of mouse lung adenocarcinoma cells.

Mastic oil from Pistacia lentiscus variation chia, a natural combination of bioactive terpenes, has been shown to exert anti-tumor growth effects against a broad spectrum of cancers including mouse Lewis lung adenocarcinomas (LLC). However, no studies have addressed its anti-metastatic actions. In this study, we showed that treatment of LLC cells with mastic oil within a range of non-toxic concentrations (0.01–0.04% v/v): (a) abrogated their Matrigel invasion and migration capabilities in transwell assays; (b) reduced the levels of secreted MMP-2; (c) restricted phorbol ester-induced actin remodeling and (d) limited the length of neo-vessel networks in tumor microenvironment in the model of chick embryo chorioallantoic membrane. Moreover, exposure of LLC and endothelial cells to mastic oil impaired their adhesive interactions in a co-culture assay and reduced the expression of key adhesion molecules by endothelial cells upon their stimulation with tumor necrosis factor-alpha. Overall, this study provides novel evidence supporting a multipotent role for mastic oil in prevention of crucial processes related to cancer metastasis.

Enzymatic synthesis of perillyl alcohol derivatives and investigation of their antiproliferative activity

The monoterpene perillyl alcohol (POH), an intermediate in the plant terpenoid biosynthetic pathway, has well-established tumor chemopreventive and chemotherapeutic potential. We have previously shown that the primary hydroxyl group of POH is essential for its antitumor and anti-angiogenic activities. In the current study we present the enzymatic synthesis of two POH derivatives with different polar and hydrophobic characteristics, namely perillyl glucoside and perillyl glucoside fatty ester, through a two-step modification. Initial glucosylation of POH on its active hydroxyl group with D-(+)-glucose and subsequent esterification of the perillyl glucoside product with vinyl laurate were carried out using almond β-glucosidase and lipase B from Candida antarctica, respectively, in a low-water system. Optimization of enzymatic reactions was performed to achieve the highest possible conversion yields. The antitumor cell proliferation activity against mouse Lewis lung carcinoma cells was retained in both derivatives, although the perillyl glucoside ester showed greater inhibition than perillyl glucoside. Our results underline the feasibility of enzymatically producing novel bioactive analogs of phytochemicals displaying useful physicochemical properties.