Download Geranylated 4 Phenylcoumarins Exhibit Anticancer Effects against Human Prostate Cancer Cells PDF

Geranylated 4 Phenylcoumarins Exhibit Anticancer Effects against Human Prostate Cancer Cells
Name: Geranylated 4 Phenylcoumarins Exhibit Anticancer Effects against Human Prostate Cancer Cells
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Year: 2016
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death proteins which could potentially be manipulated to develop anti cancer therapy in apoptosis resistant cells. Introduction Prostate cancer is the most common cancer as well as the second leading cause of cancer related deaths in men . Despite the availability of multiple treatment options, there are cur rently no effective therapies available for treatment of apoptotic resistant androgen indepen dent prostate cancer which often arises after hormonal deprivation or ablation therapy . Natural phytocompounds are considered as an important source of cancer chemopreventive and chemotherapeutic agents. Prominent examples include coumarin based compounds which are derived from fruits and stem barks of various plants, such asCasimora edulis, Calophyllum inophyllum,Mesua ferrea andMesua kunstleri. Coumarins have been recognized to possess anti inflammatory, antioxidant, antiallergic, hepatoprotective, antith rombotic, antimicrobial, anti arrythmic, anti osteoporosis, antiviral, and anticarcinogenic activities . Yang and colleagues, demonstrated fifteen isoprenylated coumarins isolated fromMammea americanaexhibited significant cytotoxic effects and high anti oxidant activity in human colon cancer cell lines . In a study with both coumarin and 7 hydroxycoumarin, inhibition of cell growth in lung carcinoma cell lines by inducing G 1 phase cell cycle arrest and apoptosis was demonstrated . In another report, geranylated coumarins were seen to exert anti proliferative actions through apoptotic cell death in leukemia cells . In this study, two major geranylated 4 phenylcoumarins; DMDP 1 & 2 isolated from the bark ofMesua elegans(Clusiaceae), locally known as"pokok penaga", were subjected to various cytotoxic and apoptotic assays. To the authors'knowledge, this is the first report on the induc tion of multiple"apoptosis like"caspase independent programmed cell death on prostate can cer cells by geranylated 4 phenylcoumarins. Materials and Methods Collection ofMesua elegans The bark ofMesua elegans(King) Kosterm was collected from Sungai Badak Forest Reserve, Kedah, Malaysia. The sample was identified by Mr Teo Leong Eng and deposited in the Depart ment of Chemistry, Faculty of Science, University of Malaya herbarium (Ref. No: KL5232). Extraction and purification of coumarin analogues Dried ground bark ofMesua elegans(1.5 kg) was macerated with hexane (3 x 4L, 48 h each time) at room temperature. The extract was dried off using rotary evaporator which yielded a yellow gummy residue (120.3 g). A portion of the crude hexane (13.0 g) was subjected to col umn chromatography fractionation over silica gel 60 (230 400 mesh) and eluted with hexane EtOAc (from 9.5 to 0) and EtOAc MeOH (from 5 to 0) to give fractions A H. Fraction A was subjected to silica gel chromatography and eluted with hexane EtOAc (from 9.7 to 9.5) to pro duce sub fractions A1 A4. Observations of fraction separation were done using TLC with silica gel 60 F 254 plates. Fraction A2 was subjected to HPLC analysis using ZORBAX Eclipse Plus C18, 4.6 mm i.d. x 150 mm x 3.5 m HPLC column, and separated using ZORBAX Eclipse Plus C18, 9.4 mm i.d. x 250 mm x 3.5 m HPLC column to purify isomers DMDP 1 & 2 (Fig 1). Water auto purification system was used for HPLC separation. NMR spectra were Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 20162/18


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Fig 1. Isolation and characterization of two 4 phenylcoumarins fromMesua elegans. (A)Chemical structure of DMDP 1 & 2.(B)(I) HPLC chromatogram of fraction A2 with the following experimental conditions (analytical): column, ZORBAX Eclipse Plus C18, 4.6 mm i.d. x 150 mm x 3.5 m; mobile phase, two solvents: A, 0.1% formic acid in H 2 0 and B, 0.1% formic acid in MeOH; the elution program at 0.6 mL/min as isocratic with 90% B (0 30 min) to afford isomers DMDP 1 & 2. (II) HPLC chromatogram of fraction A2 with the following experimental conditions (semi preparative): column, ZORBAX Eclipse Plus C18, 9.4 mm i. d. x 250 mm x 3.5 m; mobile phase, two solvents: A, 0.1% formic acid in H 2 0 and B, 0.1% formic acid in MeOH; the elution program at 3.0 mL/min as isocratic with 90% B (0 50 min) to afford isomers DMDP 1 & 2. doi:10.1371/journal.pone.0151472.g001 Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 20163/18


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obtained using JEOL LA400 FT NMR and JEOL ECA400 FT NMR Spectrometer System (400 MHz) with CDCl 3 as solvent. UV spectra were recorded on a Shimadzu UV Visible Recording Spectrophotometer using ethanol as solvent with mirror UV cell. The IR spectra were obtained through Perkin Elmer FT IR Spectrometer Spectrum RX1 with CHCl 3 as solvent. Mass spectra was carried out on Agilent Technologies 6530 Accurate Mass Q TOF LC MS, with ZORBAX Eclipse XDB C18 Rapid Resolution HT 4.6 mm i.d. x 50 mm x 1.8 m column (S1 Table). Cell lines and culture conditions A total of ten human cancer cell lines were used: Ca Ski, HeLa, HepG2, A549, PC 3, DU 145, MCF7 (purchased from ATCC), HSC4 (obtained from Cancer Research Initiative Foundation, Malaysia), MDA MB 231 and SK LU 1 (purchased from AseaCyte, Malaysia). NP69, the nor mal cell line was a gift from Prof GSW Tsao . Each cell line was maintained with the appro priate growth medium (RPMI 1640: for cells A549, SK LU 1, MDA MB 231, PC 3, DU 145, MCF7) and (DMEM: for cells Ca Ski, HepG2, HeLa, HSC4) and (Keratinocyte SFM: NP69), which were supplemented with 10% (v/v) fetal bovine serum. Cells were grown as monolayers at 37 C in humidified atmosphere with 5% CO 2 / 95% air. MTT assay The cytotoxic effects of DMDP 1 & 2 on cancer cell lines were determined using the MTT assay. A total of 1.0 x 10 4 cells were plated (100 l/well) and treated at concentrations of 10 to 100 M for 24 h with DMSO as a negative control. MTT solution (5 mg/ml) was added to each well and incubated at 37 C for 1 h. Absorbance was measured at 560 nm using a microplate reader (Tecan Sunrise 1 , Switzerland). Live/Dead assay Assessment of cell viability upon treatment with both analogues was conducted using the LIVE/DEAD 1 Viability/Cytotoxicity kit (Molecular Probes, Invitrogen, NY, USA). Cells were cultured on glass cover slip placed in 6 well plates and treated at IC 50 concentration for 24 h. Cells were stained using a dual fluorescence system consisting of 150.0 l of calcein AM (2.0 M) and ethidium homodimer (EthD) (4.0 M). Excitation and emission wavelengths were set at 494/517 nm for calcein AM and 528/617 nm for EthD respectively. Visualization of samples was done using a Nikon Eclipse TS 100 fluorescence microscope (Nikon, Japan) under 100 magnification. Flow cytometer analysis Detection of various cell death stages were conducted using Annexin V FITC Apoptosis Detec tion Kit (Calbiochem, USA). Briefly, 1.0 x 10 4 cells treated and untreated were incubated with Annexin V (200 g/ml). Samples were centrifuged and re suspended in 1 ice cold binding buffer with propidium iodide (PI). Detection and analysis was carried out using the BD FACS Canto II flow cytometer (Becton Dickenson, USA). For cell cycle analysis, 2.0 x 10 4 cells treated and untreated were suspended in PI (50.0 g/mL) and RNase A (10.0 mg/mL). These cells were fixed in ice cold 70.0% (v/v) ethanol and kept at 20 C overnight. Cell cycle distribu tion was analyzed by flow cytometer and the percentages at different phases were determined by ModFit LT cell cycle analysis software. Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 20164/18


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Apoptosis protein array A total of 1.0 x 10 6 cells were untreated and treated for 6 h. The cell lysates were normalized using BCA Protein Assay kit (Pierce, USA) and incubated at 4 C overnight with Raybio 1 Human Apoptosis Antibody Array slides (RayBiotech Inc. USA, GA). All slides were washed and a cocktail of biotinylated antibody mix was used to detect apoptosis related proteins. After incubation with Hylate Plus conjugated streptavidin, signals were detected with a fluores cence scanner by Axon Genepix 1 using the Cy2 channel. Shortlisted protein expression target were selected based on a fold change threshold of?1.5 or? 1.5. Western blotting Nuclear and cytoplasmic proteins were extracted from PC 3 and DU 145 cell lines treated with analogues IC 50 values for 6, 12, and 24 h using the NE PER 1 Nuclear and Cytoplasmic Extrac tion kit (Pierce, USA). Concentrations were determined using BCA Protein Assay kit (Pierce, USA). Equivalent amounts of protein (20 g) from both untreated and treated cells were sepa rated on 12% (w/v) SDS polyacrylamide gels and transferred onto nitrocellulose membranes, which were subsequently incubated with primary antibody overnight at 4 C, followed by incu bation with horseradish peroxidase (HRP) linked secondary antibodies. 14 primary antibodies from Cell Signaling Technology, Danvers, MA against GADPH, caspase 3, 8, 9, PARP, Bcl 2, Bax, microtubule associated light chain (LC3), granzyme B, cathepsin B, calpain 2, p53, phos pho p53 and p62/SQSTM1 were used. Protein bands were visualized via enhanced chemilumi nescence signals on x rays films. Intensities of all bands were quantified using image analysis software (NIH ImageJ v1.43, National Institutes of Health, USA). Anti GADPH control anti bodies were used for normalization of band intensities. Analysis of GFP LC3 PC 3 and DU 145 cells were plated at a density of 4.0 x 10 4 cells/well in 6 well plate, and left to adhere overnight in a 37 C incubator with 5% CO 2 . All cells were transduced with RFP GFP LC3B reagent using commercially available Premo Autophagy Tandem Sensor RFP GFP LC3B Kit (Life Technologies, USA) for 48 h. The following day, cells were incubated with 100 M chloroquine diphosphate (CQ), and treated with either DMDP 1, DMDP 2 or left untreated (control) for 24 h. The cells were visualized under an inverted fluorescent micro scope (Nikon Instruments, Japan) using a blue filter to detect the accumulation of GFP LC3 punctate with GFP emission. Statistical analysis All results were expressed as mean S.D of data obtained from at least three independent bio logical replicates. One way ANOVA was employed to assess the significant differences between controls and treated samples with ap value threshold of?0.05. Results Characterization of coumarin analogues Both DMDP 1 & 2 were isolated from the hexane extract of the bark ofMesua eleganswith >98% purity (S1 Fig). DMDP 1 was isolated as white crystals with m.p. 90 92 C while DMDP 2 as colorless oil. HRESIMS revealed an + ion peak at m/z 475.2728 (calculated 475.5945), corresponding to the molecular formula of C 30 H 34 O 5 for both analogues. NMR, IR and UV data of these compounds have been studied and compared with literature , and the structures of these compounds were confirmed as DMDP 1[5,7 dihydroxy 8 Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 20165/18


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(2 methylbutanoyl) 6 4 phenyl 2H chromen 2 one] and DMDP 2 4 phenyl 2H chromen 2 one] Cytotoxic effects of coumarin analogues Our results demonstrated induction of cytotoxicity in a dose and time dependent manner after 24 h of exposure on tested cell lines. Based on IC 50 values, DMDP 1 induced cell death most effectively in PC 3 cells with an IC 50 value of 9.0 M while DMDP 2 performed best in DU 145 cells with a value of 24.0 M, indicating a profound effect on prostate cancer cell lines (Table 1). Viability of cells treated with DMSO alone were insignificantly affected (?2.0%) thereby ruling out the involvement of solvent induced cytotoxicity. Live/Dead assays were per formed to confirm their cytotoxic effects, cell death was only observed in PC 3 and DU 145 cells after treatment, but not in NP69 cells where viability was maintained at 92.7%. Percentage of PC 3 cell viability decreased from 98.0% to 43.0% while the viability of DU 145 cells decreased from 95.0% to 38.0% (Fig 2A). This indicated that both compounds inflict a more gradual cytotoxic pharmacokinetic effect in slow growing normal cells compared to rapidly proliferating cancer cells, which is a common characteristic among chemotherapeutic drugs. DMDP 1 & 2 induces cell death Following initial cytotoxicity data, we decided to focus this study on androgen independent human prostate cancer cell lines. Annexin V FITC/PI flow cytometry assays were used to determine mode of cell death. Cell death percentage was calculated based on top right (late apoptotic cells) and bottom right quadrants (early apoptotic cells) of the flow cytometry. The dot blot from a total of 1.0 x 10 4 PC 3 cells after treatment with IC 50 of DMDP 1 showed an increase from 12.3% to 46.4%. Similar effects were observed in DMDP 2 treated DU 145 cells where cell death population increased from 3.1% to 49.7% (Fig 2B). Even though cell death was also observed in NP69 cells, the cell death population was maintained below 10.4% after 24 h of treatment. Table 1. Summary of DMDP 1 & 2 mean IC 50 values and mean viability levels obtained from MTT assays for ten human cancers and one normal cell lines after 24 h treatment.All values were presented as mean SD of three technical and three biological replicates. Mean IC 50 SD ( M) Mean Viability SD(%) Human Cell Lines Time (h) DMDP 1 DMDP 2 DMDP 1 DMDP 2 Prostate adenocarcinoma (PC 3) 24 9 1.2 38 2.5 48 5.1 34 6.5 Prostate adenocarcinoma (DU 145) 24 45 3.3 24 1.6 22 1.8 43 2.9 Cervical carcinoma (Ca Ski) 24 47 0.7 28 3.6 40 4.4 47 8.4 Cervical carcinoma (HeLa) 24 n.d 81 4.2 65 5.5 46 3.7 Oral squamous carcinoma (HSC4) 24 10 2.5 32 1.2 42 3.5 44 7.1 Breast adenocarcinoma (MCF7) 24 55 2.1 60 4.2 49 3.1 51 6.2 Breast adenocarcinoma (MDA MB 231) 24 n.d 56 1.1 86 0.6 44 0.4 Hepatocyte carcinoma (HepG2) 24 47 2.2 59 1.5 57 4.6 46 1.9 Lung adenocarcinoma (A549) 24 n.d n.d 87 2.7 80 3.5 Lung adenocarcinoma (SK LU 1) 24 n.d n.d 64 2.4 53 0.7 Immortalized nasopharyngeal epithelial (NP69) 24 25 3.0 38 4.2 45 9.4 25 3.1 Viability level of cells after treatment with 100 M DMDP 1 or DMDP 2 for 24 h n.d. denotes an overall cell viability level of>50% after treatment with either DMDP 1 or DMDP 2 at 100.0 M for 24 h. doi:10.1371/journal.pone.0151472.t001 Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 20166/18


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pathways. InTable 2, treatment of PC 3 cells with DMDP 1 demonstrated a reduced expres sion of survivin and insulin growth factor receptor 1 (IGF1R) coupled with an increased level of insulin growth factor binding protein 2 (IGFBP 2) and heat shock protein 27 (HSP 27). Meanwhile, treatment of DMDP 2 on DU 145 cells revealed reduced expressions of three pro teins, that is, CD40 ligand, tumour necrosis factor receptor 1 (sTNF R1) and TNF related apo ptosis inducing ligand 1 (TRAIL 1). All other proteins tested did not show any significant change (fold change<1.5 or> 1.5) in expression, including prominent apoptotic effectors such as caspases 8 and 3, as well as Bcl 2 members such as Bad, Bax, Bim and Bcl 2 itself. Interestingly, this indicated that the death receptor pathway and the mitochondrial pathway were not activated following DMDP 1 & 2 treatments, but instead suggested a caspase inde pendent mode of cell death. In order to investigate the caspase independent mechanisms involved, western blotting analysis of DMDP 1 & 2 treated PC 3 and DU 145 cells was carried out. The results was found to be consistent with data obtained from the protein array, where no induction of caspases 3, 8 and 9 proteins was observed, while the level of anti apoptotic Bcl 2 was found to increase concomitantly with the change in Bax (Fig 3a & 3b). This observa tion was also consistent with the negative result obtained from poly ADP ribose polymerase (PARP) cleavage, cell cycle arrest and DNA fragmentation assays where activation of caspases were found to be lacking (S2 Fig). DMDP 1 & 2 induces cell death via multiple pathways In order to identify which caspase independent mechanisms were involved, western blotting analysis of treated and untreated PC 3 and DU 145 cells were carried out. InFig 3, the absence of cleaved PARP, caspases 3, 8 and 9, up regulation of Bcl 2 and down regulation of Bax confirmed our hypothesis on the possible involvement of caspase independent pathways medi ated by autophagy or other organelles, such as lysosomes and endoplasmic reticulum (ER), which releases and activates death proteins such as, cathepsins, granzymes, and calpains. West ern data (Fig 4) demonstrated an increase in cathepsin B levels in DU 145 cells which indicated that DMDP 2 induced the activation of this lysosomal cysteine protease in place of caspases. Calpain 2 levels, which are auto degraded upon its activation, were decreased following Table 2. List of significant protein level changes following treatment with DMDP 1 & 2 for 6 h on PC 3 and DU 145 cell lines respectively.A total of 42 apoptosis related proteins were assayed using the Ray Bio 1 Human Apoptosis Antibody Array G Series 1. Mean protein fold changes were calculated in comparison to untreated cells from four biological replicates. Protein Name PC 3 treated with DMDP 1 (9 M) Mean Fold Change S.D. p value IGFBP 2 1.7 0.4 0.034 HSP 27 1.5 0.5 0.036 IGF1R 1.5 0.2 0.012 Survivin 1.6 0.3 0.048 DU 145 treated with DMDP 2 (24 M) Mean Fold Change S.D. p value CD40L 1.5 0.1 0.011 sTNF R1 1.5 0.4 0.042 TRAILR 1 1.5 0.3 0.045 Mean fold change threshold values were set at?1.5 or? 1.5 p value threshold value set at?0.05 doi:10.1371/journal.pone.0151472.t002 Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 20168/18


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treatment by DMDP 1 & 2. This result was further validated with combination treatment of each analogue with the calpain 2 inhibitor, calpeptin by western blot. However, granzyme B does not seem to play a role as its protein levels were reduced consistently over the 24 h course of treatment. Interestingly, the western results indicated that upon treatment, total and Fig 3. Western blotting confirmation on the effects of DMDP 1 & 2 treatment over 24 h on PC 3 and DU 145 caspase levels.(A) Treatment with DMDP 1 & 2 showed full length of protein levels and absence of cleaved PARP and caspases 9, 3 and 8. (B) Analysis of anti apoptotic Bcl 2 and pro apoptotic Bax protein levels. Quantification of protein band intensities were determined by densitometry analysis and normalized to GADPH using the ImageJ v1.43 software. All results were presented as mean normalized intensity S.D. of three independent experiments. doi:10.1371/journal.pone.0151472.g003 Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 20169/18


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phosphorylated p53 levels were both up regulated in a time dependent manner. Activation of p53 may increase the selectivity and safety of treatment with these two coumarin analogues by selective protection of normal cells and tissues. DMDP 1 induces autophagy and activates calpain 2 in PC 3 cells Western blotting on LC3 I/II protein level which is a standard marker for autophagy activation showed conversions of LC3 I to LC3 II after treatment with DMDP 1 and combined treatment of DMDP 1 and early autophagy inhibitor, 3MA in PC 3 cell line. However, no conversion was observed in the untreated and inhibitor treated cells. Furthermore, analysis of GFP LC3 result showed increased GFP LC3 punctate in PC 3 cells pre treated with chloroquine (CQ) and treated with DMDP 1, whereas the GFP LC3 was distributed evenly throughout the cells Fig 4. Activation of proteins involved in caspase independent pathways.(A) Cells were treated with DMDP 1 & 2 over 24 h, followed by examination of key proteins involved in multiple mode of cell death by western blotting. (B) Quantification of band intensities were determined by densitometry analysis and normalized to GADPH using the ImageJ v1.43 software. All results were presented as mean normalized intensity S.D. of three independent experiments. doi:10.1371/journal.pone.0151472.g004 Anticancer Effects of Geranylated 4 Phenylcoumarins on Prostate Cancer PLOS ONE | DOI:10.1371/journal.pone.0151472 March 14, 201610 / 18


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