Development of human prostate cancer stem cells involves epigenomic alteration and PI3K/AKT pathway activation.

BACKGROUND: Human prostate cancer spheres endowed with stem cell properties have been obtained from androgen-dependent cell line LNCaP after exposure to an epigenomic modulator phenethyl isothiocynate (PEITC). Sphere cells can self-renew and grow with androgen, and also without androgen. Little is known about the signaling pathway and mechanism in the development of the stem cells in the spheres. METHODS: Expression of phosphoinositol-3 kinase (PI3K) pathway members and histone acetylation were quantified in the tumor spheres and LNCaP cells by western immunoblotting. RESULTS: The level of phosphorylated AKT was significantly increased in the sphere stem cells than the LNCaP cells at an average of 7.4 folds (range 5.8-10.7 folds), whereas the P27 level was elevated 5.4 folds (range 4.8-6.3 folds) (P < 0.05). The acetylation level on histone H3 lysine 9 was decreased. CONCLUSIONS: PEITC appears to regulate the epigenome through histone acetylation and activate the PI3K/AKT pathway in the LNCaP cells. This mechanism may be responsible in part for the development of the prostate cancer stem cells.

Mitochondrial structure alteration in human prostate cancer cells upon initial interaction with a chemopreventive agent phenethyl isothiocyanate.

BACKGROUND: Phenethyl isothiocyanate (PEITC), present naturally in cruciferous vegetables, is a chemopreventive agent. It blocks initiation and post-initiation progression of carcinogenesis. Mechanism study in human prostate cancer cells revealed that PEITC is a dual inhibitor of aberrant DNA hypermethylation and histone deacetylases, reactivating silenced genes and regulating the androgen-mediated growth of tumor cells. The identity of the cellular organelle that initially interacts with PEITC has not been fully described. METHODS: Human prostate cancer LNCaP cells were exposed to PEITC and the effects on cellular fine structure examined by transmission electron microscopic studies. Alteration of mitochondrial membrane potential and cytochrome c release were evaluated as early events of apoptosis, and the TUNEL method for quantifying apoptotic cells. Mitochondria were isolated for determining their protein expression. RESULTS: Ultrastructural analyses have revealed condensed mitochondria and a perturbed mitochondrial cristae structure, which assumed a rounded and dilated shape within 4-hours of PEITC contact, and became more pronounced with longer PEITC exposure. They presented as the most prominent intracellular alterations in the early hours. Mitochondria structure alterations were demonstrated, for the first time, with the isothiocyanates. An increase in the number of smooth endoplasmic reticulum and vacuoles were also noted that is consistent with the presence of autophagy. Early events of apoptosis were detected, with cytochrome c released along with the appearance of mitochondrial alteration. Mitochondrial membrane potential was disrupted within 18 hours of PEITC exposure, preceding the appearance of apoptotic cells with DNA strand breaks. In parallel, the expression of the mitochondrial class III ß-tubulin in the outer membrane, which associates with the permeability transition pore, was significantly reduced as examined with isolated mitochondria. CONCLUSION: Mitochondria may represent the organelle target of the isothiocyanates, indicating that the isothiocyanates may be mitochondria-interacting agents to inhibit carcinogenesis.

Phenethyl isothiocyanate and paclitaxel synergistically enhanced apoptosis and alpha-tubulin hyperacetylation in breast cancer cells.

Combination of phenethyl isothiocyanate (PEITC) and paclitaxel (taxol) has been shown to work synergistically to increase apoptosis and cell cycle arrest in breast cancer cells. In this report, we further explored the mechanisms for the synergistic activity of PEITC and taxol in MCF7 and MDA-MB-231 (MB) breast cancer cell lines. By Western blotting analysis, treatment of MCF7 cells with both PEITC and taxol led to a 10.4-fold and 5.96-fold increase in specific acetylation of alpha-tubulin over single agent PEITC and taxol, respectively. This synergistic effect on acetylation of alpha-tubulin was also seen in MB cells. The combination of PEITC and taxol also reduced expressions of cell cycle regulator Cdk1, and anti-apoptotic protein bcl-2, enhanced expression of Bax and cleavage of PARP proteins. In conclusion, this study provided biochemical evidence for the mechanism of synergistic effect between the epigenetic agent PEITC and the chemotherapeutic agent taxol.

Synergistic effect of paclitaxel and epigenetic agent phenethyl isothiocyanate on growth inhibition, cell cycle arrest and apoptosis in breast cancer cells.

This study examined whether combining paclitaxel (taxol) with a novel epigenetic agent phenethyl isothiocyanate (PEITC) will yield a synergistic effect on inhibiting breast cancer cells. Two drug-resistant breast cancer cell lines, MCF7 and MDA-MB-231, were treated with PEITC and taxol. Cell growth, cell cycle, and apoptosis were examined. The combination of PEITC and taxol significantly decreased the IC50 of PEITC and taxol over each agent alone. The combination also increased apoptosis by more than two fold over each single agent in both cell lines. A significant increase of cells in the G2/M phases was detected. In conclusion, the combination of PEITC and taxol exhibits a synergistic effect on growth inhibition in breast cancer cells. This combination deserves further study in vivo.

Effect of phenylhexyl isothiocyanate on aberrant histone H3 methylation in primary human acute leukemia.

BACKGROUND: We have previously studied the histone acetylation in primary human leukemia cells. However, histone H3 methylation in these cells has not been characterized. METHODS: This study examined the methylation status at histone H3 lysine 4 (H3K4) and histone H3 lysine 9 (H3K9) in primary acute leukemia cells obtained from patients and compared with those in the non-leukemia and healthy cells. We further characterized the effect of phenylhexyl isothiocyanate (PHI), Trichostatin A (TSA), and 5-aza-2'-deoxycytidine (5-Aza) on the cells. RESULTS: We found that methylation of histone H3K4 was virtually undetectable, while methylation at H3K9 was significantly higher in primary human leukemia cells. The histone H3K9 hypermethylation and histone H3K4 hypomethylation were observed in both myeloid and lymphoid leukemia cells. PHI was found to be able to normalize the methylation level in the primary leukemia cells. We further showed that PHI was able to enhance the methyltransferase activity of H3K4 and decrease the activity of H3K9 methyltransferase. 5-Aza had similar effect on H3K4, but minimal effect on H3K9, whereas TSA had no effect on H3K4 and H3K9 methyltransferases. CONCLUSIONS: This study revealed opposite methylation level of H3K4 and H3K9 in primary human leukemia cells and demonstrated for the first time that PHI has different effects on the methyltransferases for H3K4 and H3K9.

A meta-analysis of CAG (cytarabine, aclarubicin, G-CSF) regimen for the treatment of 1029 patients with acute myeloid leukemia and myelodysplastic syndrome.

The regimen of cytarabine, aclarubicin and G-CSF (CAG) has been widely used in China and Japan for treatment of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We searched literature on CAG between 1995 and 2010 and performed a meta-analysis to determine its overall efficacy using a random-effects or fixed-effects model. Thirty five trials with a total of 1029 AML (n = 814) and MDS (n = 215) patients were included for analysis. The CR rate of AML (57.9%) was significantly higher than that of MDS (45.7%) (p < 0.01). No difference in CR was noted between the new (56.7%) and relapsed/refractory AML (60.1%) (p > 0.05). The CR rate was also significantly higher in patients with favorable (64.5%) and intermediate (69.6%) karyotypes than those with unfavorable one (29.5%) (p < 0.05). Remarkably, the CR rate of CAG was significantly higher than those of non-CAG regimens (odds ratio 2.43). CAG regimen was well tolerated, with cardiotoxicity in 2.3% and early death in 5.2% of the cases. In conclusion, CAG regimen was an effective and safe regimen for the treatment of AML, and may be more effective than non-CAG regimens. Randomized controlled trials are strongly recommended to evaluate its efficacy and safety in comparison with the current standard treatment.

Reactivating aberrantly hypermethylated p15 gene in leukemic T cells by a phenylhexyl isothiocyanate mediated inter-active mechanism on DNA and chromatin.

BACKGROUND: We have previously demonstrated that phenylhexyl isothiocyanate (PHI), a synthetic isothiocyanate, inhibits histone deacetylases and remodels chromatins to induce growth arrest in HL-60 myeloid leukemia cells in a concentration-dependent manner. METHODS: To investigate the effect of PHI, a novel histone deacetylases inhibitor (HDACi), on demethylation and activation of transcription of p15 in acute lymphoid leukemia cell line Molt-4, and to further decipher the potential mechanism of demethylation, DNA sequencing and modified methylation specific PCR (MSP) were used to screen p15-M and p15-U mRNA after Molt-4 cells were treated with PHI, 5-Aza and TSA. DNA methyltransferase 1 (DNMT1), 3A (DNMT3A), 3B (DNMT3B) and p15 mRNA were measured by RT-PCR. P15 protein, acetylated histone H3 and histone H4 were detected by Western Blot. RESULTS: The gene p15 in Molt-4 cells was hypermethylated and inactive. Hypermethylation of gene p15 was attenuated and p15 gene was activated de novo after 5 days exposure to PHI in a concentration-dependent manner. DNMT1 and DNMT3B were inhibited by PHI (P < 0.05). Alteration of DNMT3A was not significant at those concentrations. Acetylated histone H3 and histone H4 were accumulated markedly after exposure to PHI. CONCLUSION: PHI could induce both DNA demethylation and acetylated H3 and H4 accumulation in Molt-4 cells. Hypermethylation of gene p15 was reversed and p15 transcription could be reactivated de novo by PHI.

[Phenylhexyl isothiocyanate (PHI) regulates histone methylation and acetylation and induces apoptosis in SMMC-7721 cells].

OBJECTIVE: To investigate the effects of PHI on histone acetylation and methylation in hepatocellular carcinoma line SMMC-7721 cells. METHODS: Apoptosis was measured by TUNNEL assay. Histone methylation and acetylation were detected by Western blot. RESULTS: PHI inhibited cells growth and induced apoptosis. PHI treatment resulted in increased acetylation of histone H3 and H4 , elevated level of histone H3 lysine 4 methylation, and decreased level of histone H3 lysine 9 methylation. CONCLUSIONS: PHI can modulate both histone acetylation and methylation, which could remodel chromatin structure. PHI may be a novel anticancer drug.

Phenylhexyl isothiocyanate has dual function as histone deacetylase inhibitor and hypomethylating agent and can inhibit myeloma cell growth by targeting critical pathways.

Histone deacetylase (HDAC) inhibitors are a new class of chemotherapeutic agents. Our laboratory has recently reported that phenylhexyl isothiocyanate (PHI), a synthetic isothiocyanate, is an inhibitor of HDAC. In this study we examined whether PHI is a hypomethylating agent and its effects on myeloma cells. RPMI8226, a myeloma cell line, was treated with PHI. PHI inhibited the proliferation of the myeloma cells and induced apoptosis in a concentration as low as 0.5 muM. Cell proliferation was reduced to 50% of control with PHI concentration of 0.5 muM. Cell cycle analysis revealed that PHI caused G1-phase arrest of RPMI8226 cells. PHI induced p16 hypomethylation in a concentration- dependent manner. PHI was further shown to induce histone H3 hyperacetylation in a concentration-dependent manner. It was also demonstrated that PHI inhibited IL-6 receptor expression and VEGF production in the RPMI8226 cells, and reactivated p21 expression. It was found that PHI induced apoptosis through disruption of mitochondrial membrane potential. For the first time we show that PHI can induce both p16 hypomethylation and histone H3 hyperacetylation. We conclude that PHI has dual epigenetic effects on p16 hypomethylation and histone hyperacetylation in myeloma cells and targets several critical processes of myeloma proliferation.

Growth inhibition of a spectrum of bacterial and fungal pathogens by sulforaphane, an isothiocyanate product found in broccoli and other cruciferous vegetables.

In addition to its documented antitumor effects, previous in vitro and in vivo infectivity experiments have shown that sulforaphane (SFN), an isothiocyanate compound found abundantly in broccoli and other cruciferous vegetables, inhibits the growth of the bacterial pathogen Helicobacter pylori. No recent evidence exists, however, on the possible microbial activity of SFN against a broader range of microorganisms, including those that may develop resistance to conventional antibiotics. The aim of this study was to determine the in vitro susceptibility patterns of SFN against a wide variety of bacterial and fungal pathogens. Sensitivity testing was done on 28 different microbial species using a modified Kirby-Bauer disk-diffusion method and results were interpreted based on guidelines established by the National Committee for Clinical Laboratory Standards. The broad-spectrum antibiotic, ceftriaxone (CTX), was used as a positive control for antimicrobial inhibition. It was found that 23 out of 28 different microbial species were inhibited by SFN with a minimal inhibitory concentration (MIC) ranging from 1-4 microg/mL. Five pathogens--Pseudomonas aeruginosa, 3 methicillin-resistant Staphylococcus aureus (MRSA) isolates and Candida albicans--were considered resistant to SFN, having MICs >or= 16-32 microg/mL. These findings suggest that, with the dual action of SFN against a select group of microorganisms and its ability to inhibit tumor growth, SFN (or the consumption of SFN-containing vegetables) might be especially helpful in preventing certain types of infections in both cancer and non-cancer patients.

Sulforaphane induces growth arrest and apoptosis in human ovarian cancer cells.

OBJECTIVES: Isothiocyanates (ITC) from broccoli and other cruciferous vegetables have long been shown to have chemopreventive properties, as demonstrated in cancer models in rodents. Sulforaphane (SFN) is a major ITC present in broccoli. We examined the effects of SFN on the growth of the OVCAR-3 and SKOV-3 ovarian carcinoma cell lines. METHODS: Cell cycle phase determination was performed using a Coulter flow cytometer. DNA strand breaks in apoptotic cells were measured by terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end-labelling (TUNEL). RESULTS: There was a concentration dependent decrease in cell density. Approximately 50% decrease was observed after 48 h of incubation with SFN (2 µM). Analysis of cell cycle phase progression revealed a decrease in the cell populations in S and G2M phases, with an increase of G1 cell population, indicating a G1 cell cycle arrest. The degree of decrease in the replicating population was concentration and time dependent. Incubation of OVCAR-3 cells in cultures with concentrations of 2, 10 and 50 µM of SFN showed 6, 8 and 17% apoptosis, respectively. In addition, when OVCAR-3 cells were exposed to SFN for various time periods (1, 2 or 3 days), the percentage of cells undergoing apoptosis was directly proportional to the incubation period. In this regard, while 18% of the cells underwent apoptosis after 2 days, 42% of the cells showed apoptosis after 3 days of incubation. CONCLUSIONS: These results clearly demonstrated an effect of SFN in inducing growth arrest and apoptosis in ovarian carcinoma cell lines.

[Experiment study of PHI on histone methylation and acetylation in Molt-4 cells].

OBJECTIVE: To investigate the effect of phenyl-hexyl isothiocyanate (PHI) on acetylation and methylation of histone in acute lymphoblastic leukemia cell line Molt4. METHODS: The inhibition of cell proliferation was observed by MTT method and clone suppression test. Apoptosis and cell cycle arrest were measured by flow cytometry. The alterations in histone acetyltransferase and acetylation and methylation of histones were detected by Western blot. RESULTS: PHI could up-regulate the expression of acetyltransferase (P300/CBP), markedly induced the accumulation of acetylated histone H3, H4 and methylated histone H3 lysine 4 (H3K4), and inhibited methylation on lysine 9 of H3 (H3K9). The epigenetic regulation resulted in cell cycle arrest at G0/G1 phase, and induction of apoptosis. CONCLUSIONS: PHI can modulate both histone methylation and acetylation. It may serve as a histone deacetylase inhibitor, and might be a potential novel anti-leukemia agent.

Epigenetic mechanism of growth inhibition induced by phenylhexyl isothiocyanate in prostate cancer cells.

BACKGROUND: Isothiocyanates, the constituents of cruciferous vegetables, may be able to prevent prostate cancer. The hypothesis that they could remodel chromatins and activate cell cycle inhibitors, such as p21 for growth inhibition, was tested. MATERIALS AND METHODS: Prostate cancer LNCaP cells were exposed to phenylhexyl isothiocyanate (PHI). The status of histone acetylation and the activity of histone deacetylases (HDAC) were investigated. The association of p21 with hyperacetylated histones was examined by chromatin immunoprecipitation. RESULTS: The PHI-exposed LNCaP cells had diminished activity of HDAC 1 and 2. Global and selective histone acetylation was enhanced, consistent with the signs of chromatin unfolding. The hyperacetylated histones increased accessibility to the p21 promoter for transcription, leading to G1 arrest and apoptosis. CONCLUSION: PHI inhibited the activity of HDAC and remodeled chromatins to activate p21 for cell cycle arrest, underlying an epigenetic mechanism regulating the growth of prostate cancer cells.

Ingestion of an isothiocyanate metabolite from cruciferous vegetables inhibits growth of human prostate cancer cell xenografts by apoptosis and cell cycle arrest.

Epidemiological surveys indicate that intake of cruciferous vegetables is inversely related to prostate cancer incidence, although the responsible dietary factors have not been identified. Our studies demonstrated that exposure of human prostate cancer cells in culture to the N-acetylcysteine (NAC) conjugate of phenethyl isothiocyanate (PEITC-NAC), the major metabolite of PEITC that is abundant in watercress, inhibited proliferation and tumorigenesis. The PEITC-NAC is known to mediate cytoprotection at initiation of carcinogenesis. The relevance of PEITC-NAC in diets on the growth of prostate tumor cells has been evaluated in immunodeficient mice with xenografted tumors of human prostate cancer PC-3 cells. The daily PEITC-NAC (8 micromol/g) supplemented diet group showed a significant reduction in tumor size in 100% of the mice during the 9-week treatment period. Tumor weight at autopsy was reduced by 50% compared with mice on the diet without PEITC-NAC (P = 0.05). Mitosis and in vivo 5-bromo-2'-deoxyuridine labeled proliferating cells were reduced in these tumors. The PEITC-NAC diet up-regulated the inhibitors of cyclin-dependent kinases p21WAF-1/Cip-1 and p27Kip1, and reduced the expression of cyclins D and E, indicating they were potential molecular targets. As a result, phosphorylated Rb was significantly decreased and the G1- to S-phase transition retarded. The treated tumors also showed a significant increase in apoptosis as determined by in situ end-labeling, and by poly ADP-ribose polymerase cleavage. This study demonstrates the first in vivo evidence of dietary PEITC-NAC inhibiting tumorigenesis of prostate cancer cells. PEITC-NAC may prevent initiation of carcinogenesis and modulate the post-initiation phase by targeting cell cycle regulators and apoptosis induction.

Targeting cell cycle machinery as a molecular mechanism of sulforaphane in prostate cancer prevention.

Epidemiological studies recently concluded that consumption of cruciferous vegetables such as broccoli, cabbage, and cauliflower, etc. is inversely related to prostate cancer risk, although the mechanism of prevention and the responsible phytochemicals are unknown. Since clinically significant prostate cancer eventually can grow independent of androgen, the association of the growth and tumorigenesis of such prostate cancer cells with sulforaphane (SFN) which is a predominant isothiocyanate in cruciferous vegetables, investigated. These vegetables contain high concentrations of glucosinolate glucoraphanin, which yield sulforaphane when hydrolyzed by the plant enzyme myrosinase. This study showed that exposure of human androgen-independent DU-145 prostate cancer cells to SFN resulted in the inhibition of growth and tumorigenesis, as revealed by a reduction in cell density, DNA synthesis, and clonogenesis. Analyses of the mechanism revealed that SFN mediated cell cycle arrest by modulating the expression and functions of cell cycle regulators. SFN induced signals that inhibited the activity of cyclin-dependent kinase cdk4 with an up-stream induction of cdk inhibitor p21WAF-1/Cip-1, and reduced cyclin D1. The inhibition of cdk kinase activity could be affected with <1 micro M SFN within 24 h. As a result, phosphorylation of Rb proteins, which activates the transition from G1- to S-phase, was significantly decreased and the cell cycle progression retarded. SFN also down-regulated the expression of bcl-2, a suppressor of apoptosis, and activated caspases to execute apoptosis in the prostate cancer cells. The regulators of cell cycle have thus been revealed as targets of sulforaphane for growth arrest and apoptosis induction. The potential of SFN, as an active dietary factor to inhibit initiation and post-initiation of prostate cancer carcinogenesis is discussed.