Human KB Cells Research Articles

Inhibition of Urokinase-Type Plasminogen Activator Expression by Macelignan in Porphyromonas gingivalis Supernatant-Induced Human Oral Epithelial Cells

This study was to investigate the effect of macelignan on Porphyromonas gingivalis supernatant-induced uPA expression via regulating mitogen-activated protein kinase (MAPK) and activating protein-1 (AP-1) signaling pathways in human oral epithelial KB cells using casein zymography, Western blotting, reverse transcription-PCR and reporter gene assays. Zymographic analysis of secreted enzymes identified the main caseinolytic band at 54 kDa. Macelignan inhibited the expression of uPA protein and mRNA, as well uPA secretion, in KB cells exposed to P. gingivalis supernatant. Consistent with these findings, macelignan suppressed phosphorylation of p38 and c-Jun N terminal kinase (JNK) in P. gingivalis supernatant-induced KB cells. The levels of c-Fos and phosphorylated c-Jun, which together form AP-1, the transcription factor that is involved in uPA gene expression, were partially reduced by macelignan. Macelignan also blocked P. gingivalis supernatant-induced AP-1 activity in these cells. These results suggest that macelignan decreased P. gingivalis supernatant-induced uPA expression by blocking AP-1 activity, which may be mediated by inhibition of phosphorylation of p38 and JNK in KB cells. Macelignan may potently use for the modulation of periodontal inflammation.

Synthesis and evaluation of a technetium-99m labeled cytotoxic bombesin peptide conjugate for targeting bombesin receptor-expressing tumors

Conjugation of the cytotoxic drugs to receptor-binding peptides is an attractive approach for the targeted delivery of cytotoxic peptide conjugates to tumor cells. In an attempt to develop an efficient peptide-based radiopharmaceutical for targeting bombesin (BN) receptor-expressing tumors (i.e., breast and prostate), we have prepared by solid-phase peptide synthesis, a novel BN analog derived from the universal sequence of BN and conjugated to a widely characterized antineoplastic agent, methotrexate (MTX). MTX-BN, after radiolabeling with (99m)Tc via stannous-tartrate exchange, showed a good stability against cysteine and histidine transchelation as well as a high in vitro metabolic stability in human plasma. In vitro cell-binding and internalization on MDA-MB-231, MCF-7, T47-D breast cancer and PC-3 prostate cancer cell lines demonstrated high affinity and specificity of (99m)Tc-MTX-BN towards both human breast and prostate cancer cells (binding affinities in nanomolar range). In addition, the radioconjugate displayed a significant internalization (values ranged between 19-35%) into the tumor cells. In vivo biodistribution and clearance kinetics in Balb/c mice are characterized by an efficient clearance from the blood and excretion mainly through the renal-urinary pathway with some elimination via the hepatobiliary system. In vivo tumor uptake in nude mice bearing MDA-MB-231 cells was 2.70+/-0.44% ID/g at 1 h, whereas in nude mice with human epidermoid KB cells the accumulation in the tumor was found to be 1.48+/-0.31% ID/g at 1 h post injection. The tumor uptake was always higher than in the blood and muscle, with good tumor retention and good tumor-to-blood and tumor-to-muscle ratios. The accumulation/retention in the major organs (i.e., lungs, stomach, liver, intestines, etc.) was low to moderate (<6% ID/g) in both healthy and tumor-bearing mice. However, the uptake/retention in the kidneys was rather high (up to 11.05+/-1.80% ID/g), which is of a concern, particularly for radionuclide therapy. This initial study towards the development of a novel cytotoxic BN conjugate suggest that the combination of favorable in vitro and in vivo properties may render (99m)Tc-MTX-BN a potential candidate for the targeted imaging and eventually for radionuclide therapy (when labeled with an appropriate radionuclide) of BN receptor-positive tumors and deserves further evaluation.

Reversal Effect of A Novel N-sugar Substituted Thalidomide Analogue on Multidrug Resistant Human Nasopharyngeal Carcinoma Cells*

One major problem to successful treatment of cancer is the development of resistance by tumor cells to multiple chemotherapeutic drugs, a phenomenon named multidrug resistance (MDR). Searching for the novel chemotherapeutical agents is one of the important strategies for overcoming MDR. By using a cytotoxicity assay, flow cytometry analysis, Western-blotting and RT-PCR, a drug (Taxol, TAX) resistant human nasopharyngeal carcinoma KB cell line (KB/TAX) was established by addition of the drug to the cell cultures gradually, then a novel N-sugar substituted thalidomide analogue (STA-35) was investigated for its reversal effect on MDR of KB/TAX cells and possible mechanism. The results showed that KB/TAX cells were resistant to several chemotherapeutical agents, and the relative resistance to TAX was 73.1. Compared with parental KB cells, the function and protein expression of P-glycoprotein (P-gp), as well as mdr1 gene in the KB/TAX cells were remarkable reduced. Moreover, both KB and KB/TAX cells were sensitive to STA-35, the relative resistance to TAX on KB/TAX cells was decreased by the addition of STA-35. Furthermore, STA-35 (5 ～20 μmol/L)was capable to reduced the activity of P-gp by increasing the accumulation of rhodamine 123, decreasing P-gp expression in KB/TAX cells in a dose dependent manner , but had no effect on the mdr1 gene expression. These results suggest a potential action of STA-35 as MDR reversing agent, and one of the possible mechanisms could be the suppression of P-gp function and protein expression.

Hydrogenative desulphurization of thienopyrrolizinones: An easy and selective access to ( Z)-phenethylidenepyrrolizinones with in vitro cytotoxic activity

Attempts in view to dearomatize some previously reported tripentones with potent antineoplastic activities led in thiophene series to an unexpected hydrogenative desulphurization reaction. The resulting ( Z)-phenethylidenepyrrolizinones were tested in vitro over human epidermoid carcinoma KB cell line. The results of this biological evaluation indicated that the tricyclic core of our model can be cleaved with a partial respect of the activity.

Antimalarial acridines: Synthesis, in vitro activity against P. falciparum and interaction with hematin

A series of acridine derivatives were synthesised and their in vitro antimalarial activity was evaluated against one chloroquine-susceptible strain (3D7) and three chloroquine-resistant strains (W2, Bre1 and FCR3) of Plasmodium falciparum. Structure–activity relationship showed that two positives charges as well as 6-chloro and 2-methoxy substituents on the acridine ring were required to exert a good antimalarial activity. The best compounds possessing these features inhibited the growth of the chloroquine-susceptible strain with an IC 50 ⩽ 0.07 μM, close to that of chloroquine itself, and that of the three chloroquine-resistant strains better than chloroquine with IC 50 ⩽ 0.3 μM. These acridine derivatives inhibited the formation of β-hematin, suggesting that, like CQ, they act on the haem crystallization process. Finally, in vitro cytotoxicity was also evaluated upon human KB cells, which showed that one of them 9-(6-ammonioethylamino)-6-chloro-2-methoxyacridinium dichloride 1 displayed a promising antimalarial activity in vitro with a quite good selectivity index versus mammalian cell on the CQ-susceptible strain and promising selectivity on other strains.

A “Click Chemistry” Approach to the Efficient Synthesis of Multiple Imaging Probes Derived from a Single Precursor

Different imaging modalities can provide complementary information on biological processes at the cellular or molecular level in vitro and in vivo. However, specific molecular probes suitable for a comparison of different imaging modalities are often not readily accessible because their preparation is usually accomplished by individually developed and optimized syntheses. Herein, we present a general, modular synthetic approach that provides access to multiple probes derived from a single precursor by application of the same, efficient functionalization strategy, the Cu(I)-catalyzed cycloaddition of terminal alkynes and azides (click chemistry). To demonstrate the viability and efficiency of this approach, folic acid (FA) was selected as a targeting vector because the preparation of FA-based imaging probes used for SPECT, PET, MRI, and NIRF by reported synthetic strategies is usually difficult to achieve and often results in low overall yields. We prepared a versatile γ-azido-FA precursor as well as a set of alkyne functionalized probes and precursors including ligand systems suitable for the chelation of various (radio)metals, an NIR dye and (18)F- and (19)F-derivatives, which enabled the parallel development of new FA-imaging probes. The Cu(I)-mediated coupling of the alkynes with the γ-azido-FA precursor was accomplished in high yields and with minimal use of protective groups. The various probes were fully characterized spectroscopically as well as in vitro and in vivo. In vitro, all new FA-derivatives exhibited high affinity toward the folic acid receptor (FR) and/or were specifically internalized into FR-overexpressing KB cells. In vivo experiments with nude mice showed that all probes (except the MRI probes which have not been tested yet) accumulated specifically in FR-positive organs and human KB-cell xenografts. However, in vivo imaging revealed significant differences between the various FA-derivatives with respect to unspecific, off-target localization. In general, the comparison of different probes proved the superiority of the more hydrophilic, radiometal-based imaging agents, a result which will guide future efforts for the development of FA-based imaging probes and therapeutic agents. In addition, the strategy presented herein should be readily applicable to other molecules of interest for imaging and therapeutic purposes and thus represents a valuable alternative to other synthetic approaches.

Inhibition of nucleoside transport and synergistic potentiation of methotrexate cytotoxicity by cimicifugoside, a triterpenoid from Cimicifuga simplex

Cimicifugoside, a triterpenoid isolated from Cimicifuga simplex, which has been used as a traditional Chinese medicine due to its anti-inflammatory, analgesic or anti-pyretic action, was examined for inhibition of nucleoside transport and synergistic potentiation of methotrexate cytotoxicity. Cimicifugoside inhibited uptake of uridine, thymidine and adenosine in human leukemia U937 cells with the low nanomolar IC 50 values, but did not affect that of uracil, leucine or 2-deoxyglucose at ≤100 nM. Cimicifugoside analogs differentially inhibited uridine uptake in the order cimicifugoside > cimicifugenin (aglycon of cimicifugoside) > bugbanoside B > cimicifugenin A, O-methyl cimicifugenin and bugbanoside A. Cimicifugoside had less affinity for the binding site of nitrobenzylthioinosine (typical high-affinity inhibitor of equilibrative nucleoside transporter-1) in U937 cells, K562 cells and human erythrocyte membranes compared with the prototype nucleoside transport inhibitor dipyridamole. Cimicifugoside markedly potentiated methotrexate cytotoxicity in a culture of U937 cells and human carcinoma KB cells. Potentiation of methotrexate cytotoxicity by cimicifugoside analogs in U937 cells was in proportion to their inhibitory activity against uridine uptake. The present study demonstrates that cimicifugoside is a novel specific nucleoside transport inhibitor that displays synergistic potentiation of methotrexate cytotoxicity.

Folate-mediated targeting of albumin conjugates of paclitaxel obtained through a heterogeneous phase system

The study developed cytotoxic macromolecular conjugates that specifically target the folate receptor and deliver the drug into cell cytoplasm. The anticancer agent paclitaxel was conjugated to human serum albumin (HSA) and this drug–albumin conjugate was further equipped with folic acid, linked via an extended poly(ethylene glycol) spacer. Preparation was carried out in a heterogeneous phase system exploiting the binding ability of Cibacron Blue dye to HSA. Unreacted reagents were easily removed and, after purification by gel filtration, the conjugate was fully characterized. Binding and in vitro cytotoxicity studies on human nasopharyngeal epidermal carcinoma KB and colorectal carcinoma HT-29 cells (as negative control) demonstrated increased selectivity and anti-tumoral activity.

Controlling Trafficking with a Ubiquitin Switch

A monoubiquitinylation cycle appears to control the distribution of Lst2, a protein that contributes to the delivery of EGFR to lysosomes.

Kaempferia pandurata Roxb. inhibits Porphyromonas gingivalis supernatant-induced matrix metalloproteinase-9 expression via signal transduction in human oral epidermoid cells

Ethnopharmacological relevance Kaempferia pandurata Roxb., an edible tropical medicinal plant (Zingiberaceae), has been traditionally used to treat dental caries. However, its efficacy on inhibition of matrix metalloproteinase (MMP)-9 for preventing periodontal inflammation has been rarely studied to date. Aim of the study This present study was focused to investigate the effects of the ethanolic extract of Kaempferia pandurata Roxb. on inhibition of Porphyromonas gingivalis supernatant-induced MMP-9 expression through activation of mitogen-activated protein kinase (MAPK) signaling pathways in human oral epidermoid KB cells. Materials and methods MMP-9 expression and its signaling pathways in KB cells induced by Porphyromonas gingivalis supernatant were determined by gelatin zymogram, Western blotting and reporter gene assays. Results Kaempferia pandurata significantly decreased MMP-9 expression at both protein and mRNA levels in a dose-dependent manner. Kaempferia pandurata interfered Porphyromonas gingivalis supernatant-induced MMP-9 expression in KB cells by downregulating MAPK phosphorylation (extracellular signal-related kinase 1/2, p38 kinase and c-Jun N-terminal kinase), inhibiting transcriptional expression (Elk1, c-Jun and c-Fos), and blocking AP-1 and NF-κB activities. Conclusions Kaempferia pandurata could be employed as a candidate for MMP-9 inhibitor with therapeutic potential for treatment of periodontal inflammation.

A comprehensive map of the IL-1R signalling network

The interleukin-1 (IL-1) signalling pathway represents a paradigm for all IL-1 family cytokines (IL-1A, IL-1B, IL-18, IL-33, IL1F5 to IL1F10) as well as for the toll-like-receptor-induced pathways. Research on IL-1 signalling for more than 20 years has generated a large body of experimental data, which are scattered across many different publications. No signal transduction map exists that covers comprehensively this huge knowledge on IL-1-activated effector molecules. We attempted to improve the publicly accessible IL-1 signalling map currently deposited in Netpath http://www.netpath.org/pathways. This map contains 36 molecules and information for a total of 89 reactions including physical interactions, catalytic reactions (e.g. phosphorylations) and subcellular distributions. Netpath includes data from experimental results reported in 46 publications. We created an extended version that now contains 140 molecules and 245 reactions taken from original data out of 146 selected publications. In addition to visualization of molecules involved in IL-1 signal transduction this map enables direct access to the scientific evidence that was used to build up the map. Subsequently we imported the map into GenMAPP, Version 2.1 and mapped mRNA expression data from a time course experiment of human KB cells that were stimulated for 0.5, 1, 3, 16 and 24 h with 10 ng/ml IL-1alpha. This analysis revealed that several interconnected parts of the IL-1 signalling network are co-induced or co-repressed during stimulation. By treating the cells with 50 μM PD 98059 we were able to map the part of the IL-1-signalling network that responds to ERK-inhibition at the level of mRNA. In summary, this type of knowledge-based curated data base serves not only to sort and to store data from biochemical, cell biological and molecular biology experiments but may also help to depict nodes of signal transduction that can be used to design new hypothesis-driven experiments.

The synthesis and biological evaluation of some caffeic acid amide derivatives: E-2-Cyano-(3-substituted phenyl)acrylamides

A series of caffeic acid amide derivatives 2-cyano-(3-substituted phenyl)acrylamides were synthesized via Knoevenogal condensation of substituted benzaldehydes with cyanoacetamides. The structure of compound 1f was determined as E-isomer by X-ray diffractive analysis. The biological screening tests in vitro showed that compound 1b has obvious inhibitory activities against human gastric carcinoma cell line BGC-823, human nasopharyngeal carcinoma cell line KB and human hepatoma cell line BEL-7402 with IC 50 values of 5.6 μg/mL, 13.1 μg/mL and 12.5 μg/mL, respectively. Some preliminary structure–activity relationships (SAR) were also proposed which may provide a direction for further study.

Ultraviolet B Radiation Generated Platelet-Activating Factor Receptor Agonist Formation Involves EGF-R-Mediated Reactive Oxygen Species

Recent studies have implicated the lipid mediator platelet-activating factor (PAF) in UVB-mediated systemic immunosuppression known to be a major cause for skin cancers. Previously, our group has demonstrated that UVB irradiation triggers the production of PAF and oxidized glycerophosphocholines that act as PAF-receptor (PAF-R) agonists. The present studies explored the mechanisms by which UVB generates PAF-R agonists. UVB irradiation of human epidermal KB cells resulted in both increased levels of reactive oxygen species (ROS) and PAF-R agonistic activity. Pretreatment of KB cells with antioxidants vitamin C and N-acetylcysteine or the pharmacological inhibitor PD168393 specific for the epidermal growth factor receptor all inhibited UVB-induced ROS as well as PAF-R agonists, yet had no effect on fMLP-mediated PAF-R agonist production. In addition, in vivo production of PAF-R agonists from UVB-irradiated mouse skin was blocked by both systemic vitamin C administration and topical PD168393 application. Moreover, both vitamin C and PD168393 abolished UVB-mediated but not the PAF-R agonist 1-hexadecyl-2-N-methylcarbamoyl glycerophosphocholine-mediated immunosuppression as measured by the inhibition of delayed type contact hypersensitivity to the chemical dinitrofluorobenzene. These studies suggest that UVB-induced systemic immunosuppression is due to epidermal growth factor receptor-mediated ROS which results in PAF-R agonist formation.

Evaluation of the Cytotoxicity of Geosmin and 2-Methylisoborneol Using Cultured Human, Monkey, and Dog Cells

The cytotoxicity of musty odor-emitting substances, geosmin (GM) and 2-methylisoborneol, at a concentration of 10 ng/L - 300 mg/L was investigated using cultured mammalian cells. These two compounds exhibited no cytotoxicity in either the colony-formation of human KB cells or WST-1 assays of human-, monkey-, and dog-derived cells. These results suggest that the maximum concentration (700 ng/L) of GM found in the water of Lake Shinji is not toxic.

Inhibitory Effect of Panduratin A on c-Jun N-Terminal Kinase and Activator Protein-1 Signaling Involved in Porphyromonas gingivalis Supernatant-Stimulated Matrix Metalloproteinase-9 Expression in Human Oral Epidermoid Cells

Porphyromonas gingivalis, a type of Gram-negative periodontopathogen, causes periodontal disease by activating intracellular signaling pathways that produce excessive inflammatory responses such as matrix metalloproteinases (MMPs). Recently, we reported that panduratin A, a chalcone compound isolated from Kaempferia pandurata ROXB., caused the decreased levels of MMP-9 secretion, protein, and gene expression in human oral epidermoid KB cells exposed to P. gingivalis supernatant. In this study, we clarified if mitogen-activated protein kinase (MAPK) signaling mediated MMP-9 expression by examining the effect of specific MAPK inhibitors, i.e. U0126, SB203580, and SP600125, on P. gingivalis supernatant-stimulated MMP-9 expression in KB cells. We next elucidated the molecular mechanism by which panduratin A attenuated signaling pathways involved in MMP-9 expression by performing gelatin zymography, Western blotting, reverse transcription-polymerase chain reaction, and promoter assays. Exposure of KB cells to P. gingivalis supernatant up-regulated the expression of MMP-9 protein and gene, and activation of activator protein-1 (AP-1) element, MAPK phosphorylation (extracellular signal-related kinase 1/2 (ERK1/2), p38, and c-Jun N-terminal kinase (JNK)), and transcription factors (Elk1, c-Jun, and c-Fos). A JNK inhibitor (SP600125) significantly attenuated MMP-9 gene expression and AP-1 activity in KB cells in response to P. gingivalis supernatant. Similar to SP600125, panduratin A was found to strongly suppress the level of phosphorylated JNK and block AP-1 activity in P. gingivalis supernatant-stimulated KB cells. In summary, JNK and AP-1 are the major signaling for P. gingivalis supernatant-stimulated MMP-9 expression in KB cells, and panduratin A markedly down-regulates MMP-9 expression through inhibition of these signaling.

Effects of Panduratin A Isolated from Kaempferia pandurata ROXB. on the Expression of Matrix Metalloproteinase-9 by Porphyromonas gingivalis Supernatant-Induced KB Cells

Periodontitis is initiated by accumulation of microbial plaque and activation of gingival inflammation through overexpression of matrix metalloproteinases (MMPs), leading to tissue destruction. Natural MMP inhibitors may be developed as therapeutic agents against periodontitis. In this study, panduratin A, a natural bioactive compound isolated from Kaempferia pandurata ROXB., was used to test its in vitro inhibitory activity against MMP-9 secretion from Porphyromonas gingivalis supernatant-induced human oral epidermoid carcinoma KB cells. Gelatin zymography, Western blot and RT-PCR analyses were performed to evaluate MMP-9 expression. The gelatin zymograms revealed that the main gelatinase secreted by P. gingivalis supernatant-induced KB cells migrated at 92 kDa, representing MMP-9. MMP-9 protein and mRNA levels were significantly decreased after panduratin A treatment (p<0.05). In contrast, panduratin A had no effect on tissue inhibitor of metalloproteinases (TIMP)-1 and TIMP-2 mRNA. Panduratin A also suppressed urokinase type plasminogen activator (uPA) mRNA expression. These results suggest that panduratin A could potentially prevent periodontal inflammation by decreasing the levels of MMP-9 protein and mRNA.

Down-regulation of Survivin enhances sensitivity to BPR0L075 in human cancer cells via caspase-independent mechanisms

Abstract Background: BPR0L075 [6-methoxy-3-(3',4',5'-trimethoxy-benzoyl)-1H-indole] is a novel anti-cancer compound. It inhibits tubulin polymerization and induces mitochondrial-dependent apoptosis in various human cancer cells with different multi-drug resistance (MDR) status. Over-expression of an anti-apoptotic molecule, survivin, causes drug-resistance in various cancers. Survivin inhibits apoptosis by interfering caspase-3 and promotes cell growth by stabilizing microtubule networks. Here, we determined the effects of down-regulation of survivin in BPR0L075 (L075) treatment. Methods: Western blot analysis was used to determine the expression level of survivin in L075-untreated/-treated human oral carcinoma KB and nasopharyngeal carcinoma HONE-1 cancer cells. siRNA was used to down-regulate endogenous survivin. MTT cell viability assay, real-time caspase-3 activity assay and immuno-fluorescence microscopy were used to analyze downstream effects. Results: Survivin expression was up-regulated in both KB and HONE-1 cells in response to L075 treatment. Down-regulation of survivin induced hyper-sensitivity to L075 in KB and re-stored sensitivity to L075 in KB-derived L075-resistant KB-L30 cancer cells. At the molecular level, down-regulation of survivin induced changes in microtubule dynamics in both KB and KB-L30 cells. Surprisingly, down-regulation of survivin did not enhance the activity of caspase-3 in L075 therapy. Instead, down-regulation of survivin induced translocation of the apoptosis-inducing factor (AIF) from cytoplasm to nucleus. Conclusion: Down-regulation of survivin improved drug sensitivity to L075 in both KB and L075-resistant KB-L30 cancer cells, possibly through a tubulin-dependent and caspase-independent mechanism. We suggest that combining BPR0L075 and survivin inhibitor may give better clinical outcome than the use of BPR0L075 monotherapy in future clinical trials.

Design of Folate-Linked Liposomal Doxorubicin to its Antitumor Effect in Mice

Tumor cell targeting is a promising strategy for enhancing the therapeutic potential of chemotherapy agents. Polyethylene glycol (PEG)-coated (sterically stabilized) liposomes show enhanced accumulation on the surface of tumors, but steric hindrance by PEGylation reduces the association of the liposome-bound ligand with its receptor. To increase folate receptor (FR) targeting, we optimized the concentration and PEG spacer length of folate-PEG-lipid in liposomes. Three types of folate-linked liposomal doxorubicin were designed and prepared by optimizing the concentration and PEG spacer length of folate-PEG-lipid in PEGylated or non-PEGylated liposomes and by masking folate-linked liposomes where the folate ligand is "masked" by adjacent PEG spacers. The liposome targeting efficacy was evaluated in vitro and in vivo. In human oral carcinoma KB cells, which overexpress FR, modification with sufficiently long PEG spacer and a high concentration of folate ligand to non-PEGylated liposomes increased the FR-mediated association and cytotoxicity more than with PEGylated and masked folate-linked liposomes. On the contrary, in mice bearing murine lung carcinoma M109, modification with the folate ligand in PEGylated and masked folate-linked liposomes showed significantly higher antitumor effect than with non-PEGylated liposomes irrespective of the length of time in the circulation after intravenous injection. The results of this study will be beneficial for the design and preparation of ligand-targeting carriers for cancer treatment.

Potential Anticancer Activity against Human Epithelial Cancer Cells of Peumus Boldus Leaf Extract

The potential in vitro antineoplastic effect has been studied of a methanolic extract of leaves of Peumus boldus Molina (Monimiaceae) on two human cancer epithelial cell lines, DU-145 cells (androgen-insensitive prostate cancer cells) and KB cells (oral squamous carcinoma cells). Our findings show that this extract exhibited comparable effects on the cancer cells examined as judged by IC50 values (5.07±0.4 μg/mL and 5.28±0.5 μg/mL in DU-145 and KB cells, respectively). In addition, with respect to genomic DNA damage, determined by Comet assay, the results obtained show a high fragmentation of DNA, not correlated to lactic dehydrogenase (LDH) release, a marker of membrane breakdown, in both cell lines treated with the extract at 5–20 μg/mL concentrations. Taken together, our experimental evidence may justify further investigation of the chemopreventive and chemotherapeutic potential of this natural drug.

Effect of litreol on the viability of human cancer cells

Members of the family Anacardiaceae are known to contain a number of biologically active substances, such as phenolic lipids, alkyl-catechols and alkyl-resorcinols. In the present study, human cancer cell lines, DU-145 cells (androgen-insensitive prostate cancer cells), KB cells (human epidermoid cells), and human melanoma cell line, M14, were treated for 72 h with 0.59–9.5 μM litreol (3-[pentadecyl-10-enyl-catechol]), a alkyl-catechol isolated from Lithraea caustica (Molina) Hook. & Arn. The results showed, for the first time, that litreol inhibited cancer cell viability in a dose-dependent manner. In addition, the treatment with this compound at 0.59–1.18 μM concentrations induced apoptotic cell death, demonstrated by the fragmentation of genomic DNA and by a significant increase of caspase-3 activity. The significant production of reactive oxygen species (ROS) evidenced in these experimental conditions could trigger the apoptosis cascades. Taken together, these results demonstrate that litreol attenuate the growth of human cancer cells, at least in part, triggering an apoptotic process, and they may offer a further impulse to the development of its analogues with more potent efficacy against human cancer cells.