Breast tumor metastasis is a leading cause of cancer-related deaths worldwide. Breast tumor cells frequently metastasize to brain and initiate severe therapeutic complications. The chances of brain metastasis are further elevated in patients with HER2 overexpression. In the current study, we evaluated the anti-metastatic effects of phenethyl isothiocyanate (PEITC) in a novel murine model of breast tumor metastasis. The MDA-MB-231-BR (BR-brain seeking) breast tumor cells stably transfected with luciferase were injected into the left ventricle of mouse heart and the migration of cells to brain was monitored using a non-invasive IVIS bio-luminescent imaging system. In order to study the efficacy of PEITC in preventing the number of tumor cells migrating to brain, mice were given 10 µmol PEITC by oral gavage for ten days prior to intra-cardiac injection of tumor cells labeled with quantum dots. To evaluate the tumor growth suppressive effects, 10 µmol PEITC was given to mice every day starting 14th day after intra-cardiac cell injection. Based on the presence of quantum dots in the brain section of control and treated mice, our results reveal that PEITC significantly prevented the metastasis of breast cancer cells to brain. Our results demonstrate that the growth of metastatic brain tumors in PEITC treated mice was about 50% less than that of control. According to Kaplan Meir’s curve, median survival of tumor bearing mice treated with PEITC was prolonged by 20.5%. Furthermore as compared to controls, we observed reduced HER2, EGFR and VEGF expression in the brain sections of PEITC treated mice. To the best of our knowledge, our study for the first time demonstrates the anti-metastatic effects of PEITC in vivo in a novel breast tumor metastasis model and provides the rationale for further clinical investigation.
Phenethyl isothiocyanate (PEITC) is a naturally occurring electrophile which depletes intracellular glutathione (GSH) levels and triggers accumulation of reactive oxygen species (ROS). PEITC is of considerable interest as a potential chemopreventive/chemotherapeutic agent, and in this work, we have investigated the effects of PEITC on human breast cancer cell lines. Whereas PEITC readily induced apoptosis in MDA-MB-231 cells (associated with rapid activation of caspases 9 and 3, and decreased expression of BAX), MCF7 cells were relatively resistant to the apoptosis promoting effects of PEITC. The relative resistance of MCF7 cells was associated with high basal expression of NRF2, a transcription factor that coordinates cellular protective responses to oxidants and electrophiles and raised intracellular levels of GSH. This raised basal expression of NRF2 appeared to be a response to on-going production of ROS, since treatment with the antioxidant and GSH precursor N-acetylcysteine (NAC) reduced NRF2 expression. Moreover, pre-treatment of MDA-MB-231 cells with NAC rendered these cells relatively resistant to PEITC-induced apoptosis. In summary, our data confirm that PEITC may be an effective chemopreventive/therapeutic agents for breast cancer. However, differences in the basal expression of NRF2 and resultant changes in GSH levels may be an important determinant of sensitivity to PEITC-induced apoptosis.
Phenethyl isothiocyante; Breast cancer; NRF2; Glutathione; Reactive oxygen species
Phenethyl isothiocyanate (PEITC) is a highly promising cancer chemopreventive constituent of cruciferous vegetables (e.g., watercress) with in vivo efficacy in experimental rodent cancer models. Research thus far implicates apoptosis induction in cancer chemopreventive response to PEITC, but the mechanism of proapoptotic effect is not fully understood. The present study demonstrates that p53 upregulated modulator of apoptosis (PUMA)-independent apoptosis by PEITC is mediated by B-cell lymphoma 2 interacting mediator of cell death (Bim). Exposure of a cell line (BRI-JM04) derived from spontaneously developing mammary tumor of a MMTV-neu transgenic mouse to pharmacological concentrations of PEITC resulted in decreased cell viability coupled with apoptosis induction, characterized by release of histone-associated DNA fragments into the cytosol and cleavage of poly-(ADP-ribose)-polymerase and procaspase-3. The PEITC-induced apoptosis in BRI-JM04 cells was associated with up-regulation of Bak, PUMA, and Bim (long and short forms of Bim), increased S65 phosphorylation of BimEL (extra-long form), and down-regulation of Bcl-xL and Bcl-2. On the other hand, a non-tumorigenic human mammary epithelial cell line (MCF-10A) was significantly more resistant to PEITC-induced apoptosis compared with BRI-JM04 despite induction of Bax and PUMA due to concomitant overexpression of anti-apoptotic proteins, including Bcl-xL, Bcl-2, and Mcl-1. Wild-type HCT-116 cells and its isogenic PUMA knockout variant exhibited comparable sensitivity to PEITC-induced apoptosis. On the other hand, siRNA knockdown of Bim protein imparted partial but statistically significant protection against PEITC-induced apoptosis in BRI-JM04, MCF-7, and MDA-MB-231 cells. In conclusion, the present study provides novel insight into the mechanism of PEITC-induced apoptosis involving Bim.
Phenethyl Isothiocyanate; Bim; Apoptosis; Chemoprevention
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.
This study was undertaken to determine the chemopreventative efficacy of phenethyl isothiocyanate (PEITC), a bioactive constituent of many edible cruciferous vegetables, in a mouse model of prostate cancer, and to identify potential biomarker(s) associated with PEITC response.
The chemopreventative activity of dietary PEITC was investigated in Transgenic Adenocarcinoma of Mouse Prostate mice that were fed a control diet or one containing 3 μmol PEITC/g (n = 21 mice per group) for 19 weeks. Dorsolateral prostate tissue sections were stained with hematoxylin and eosin for histopathologic evaluations and subjected to immunohistochemistry for analysis of cell proliferation (Ki-67 expression), autophagy (p62 and LC3 protein expression), and E-cadherin expression. Autophagosomes were visualized by transmission electron microscopy. Apoptotic bodies were detected by terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling. Plasma proteomics was performed by two-dimensional gel electrophoresis followed by mass spectrometry to identify potential biomarkers of PEITC activity. All statistical tests were two-sided.
Administration of PEITC (3 μmol/g diet) decreased incidence (PEITC diet vs control diet, mean = 21.65 vs 57.58%, difference = −35.93%, 95% confidence interval = −45.48% to −13.10%, P = .04) as well as burden (affected area) (PEITC diet vs control diet, mean = 18.53% vs 45.01%, difference = −26.48%, 95% confidence interval = −49.78% to −3.19%, P = .02) of poorly differentiated tumors in the dorsolateral prostate of transgenic mice compared with control mice, with no toxic effects. PEITC-mediated inhibition of prostate carcinogenesis was associated with induction of autophagy and overexpression of E-cadherin in the dorsolateral prostate. However, PEITC treatment was not associated with a decrease in cellular proliferation, apoptosis induction, or inhibition of neoangiogenesis. Plasma proteomics revealed distinct changes in the expression of several proteins (eg, suppression of clusterin protein) in the PEITC-treated mice compared with control mice.
In this transgenic model, dietary PEITC suppressed prostate cancer progression by induction of autophagic cell death. Potential biomarkers to assess the response to PEITC treatment in plasma were identified.
Ovarian cancer is the leading cause of cancer related deaths in women. Genetic alterations including overexpression of EGFR play a crucial role in ovarian carcinogenesis. Here we evaluated the effect of phenethyl isothiocyanate (PEITC) in ovarian tumor cells in vitro and in vivo. Oral administration of 12 µmol PEITC resulted in drastically suppressing ovarian tumor growth in a preclinical mouse model. Our in vitro studies demonstrated that PEITC suppress the growth of SKOV-3, OVCAR-3 and TOV-21G human ovarian cancer cells by inducing apoptosis in a concentration-dependent manner. Growth inhibitory effects of PEITC were mediated by inhibition of EGFR and AKT, which are known to be overexpressed in ovarian tumors. PEITC treatment caused significant down regulation of constitutive protein levels as well as phosphorylation of EGFR at Tyr1068 in various ovarian cancer cells. In addition, PEITC treatment drastically reduced the phosphorylation of AKT which is downstream to EGFR and disrupted mTOR signaling. PEITC treatment also inhibited the kinase activity of AKT as observed by the down regulation of p-GSK in OVCAR-3 and TOV-21G cells. AKT overexpression or TGF treatment blocked PEITC induced apoptosis in ovarian cancer cells. These results suggest that PEITC targets EGFR/AKT pathway in our model. In conclusion, our study suggests that PEITC could be used alone or in combination with other therapeutic agents to treat ovarian cancer.
Phenethyl isothiocyanate (PEITC) is a promising cancer chemopreventive component of edible cruciferous vegetables with in vivo efficacy against prostate cancer in experimental rodents. Cancer chemopreventive response to PEITC is characterized by its ability to inhibit multiple oncogenic signaling pathways, including nuclear factor-κB, Akt, and androgen receptor. The present study demonstrates, for the first time, that PEITC treatment activates Notch signaling in malignant as well as normal human prostate cells. Exposure of human prostate cancer cells (LNCaP, PC-3, and DU145) and a normal human prostate epithelial cell line (PrEC) to PEITC resulted in cleavage (active form) of Notch1 and Notch2, and increased transcriptional activity of Notch. In PC-3 and LNCaP cells, PEITC treatment caused induction of Notch ligands Jagged1 and Jagged2 (PC-3), overexpression of γ-secretase complex components Presenilin1 and Nicastrin (PC-3), nuclear enrichment of cleaved Notch2, and/or up-regulation of Notch1, Notch2, Jagged1, and/or Jagged2 mRNA. PEITC-induced apoptosis in LNCaP and PC-3 cells was significantly attenuated by RNA interference of Notch2, but not by pharmacological inhibition of Notch1. Inhibition of PC-3 and LNCaP cell migration resulting from PEITC exposure was significantly augmented by knockdown of Notch2 protein as well as pharmacological inhibition of Notch1 activation. Nuclear expression of cleaved Notch2 protein was significantly higher in PC-3 xenografts from PEITC-treated mice and dorsolateral prostates from PEITC-fed TRAMP mice compared with respective control. Because Notch signaling is implicated in epithelial-mesenchymal transition and metastasis, the present study suggests that anti-metastatic effect of PEITC may be augmented by a combination regimen involving a Notch inhibitor.
We have shown previously that cancer prevention by cruciferous vegetable constituent phenethyl isothiocyanate (PEITC) in a transgenic mouse model of prostate cancer is associated with induction of E-cadherin protein expression. Because suppression of E-cadherin protein concomitant with induction of mesenchymal markers (e.g., vimentin) is a biochemical hallmark of epithelial-mesenchymal transition, a process implicated in cancer metastasis, we hypothesized that PEITC treatment was likely to suppress vimentin protein expression. Contrary to this prediction, exposure of human breast (MDA-MB-231) and prostate cancer cells (PC-3 and DU145) to PEITC resulted in a dose-dependent increase in vimentin protein level, which was observed as early as 6 hours post-treatment and persisted for the duration of the experiment (24 hours). RNA interference of vimentin resulted in a modest augmentation of PEITC-mediated inhibition of MDA-MB-231 and PC-3 cell migration as well as cell viability. Furthermore, the PEITC-induced apoptosis was moderately increased upon siRNA knockdown of vimentin protein in MDA-MB-231 and PC-3 cells. To our surprise, PEITC treatment caused a marked decrease in vimentin protein expression in breast and prostate carcinoma in vivo in transgenic mouse models; although the difference was statistically significant only in the breast carcinomas. The present study highlights the importance of in vivo correlative studies for validation of the in vitro mechanistic observations.
Phenethyl isothiocyanate; Vimentin; Cancer chemoprevention
Phenethyl isothiocyanate (PEITC) is a cancer chemopreventive agent from cruciferous vegetables. Cholangiocarcinoma (CCA) is a chemo-resistant cancer with very poor prognosis. We evaluated the effects of PEITC on induction of apoptotic cell death in relation to cellular glutathione (GSH) and mitochondrial function of a CCA cell line, KKU-M214.
Cytotoxic effects of PEITC on a CCA cell line, KKU-M214, and a reference cell line, Chang cells were evaluated. To delineate mechanisms of cell death, the following parameters were measured; GSH and superoxide levels as the oxidative status parameters, apoptosis related proteins levels using Western blotting. Cellular free calcium level and mitochondrial transmembrane potential were also measured.
PEITC induced apoptotic cell death of both KKU-M214 and Chang cells. After PEITC treatment, both cells showed decrease of Bcl-xl and increase of Bax levels. While KKU-M214 cells released AIF, Chang cells released cytochrome c, with subsequent activation of caspase 3 and 9, upon PEITC treatment. PEITC induced superoxide formation in both cells, although it seemed not play a role in cell death. PEITC caused GSH redox stress in different ways in two cell types, because N-acetylcysteine (NAC) prevented redox stress in Chang but not in KKU-M214 cells. The loss of mitochondrial transmembrane potential was induced by PEITC concurrent with GSH stress, but was not a primary cause of cell death. The rapid increase of free calcium level in cytosol was associated with cell death in both cell lines. These events were prevented by NAC in Chang cells, but not in KKU-M214 cells.
PEITC induced cell death KKU-M214 cells and Chang cells via increase of cellular calcium mobilization and activation of mitochondrial cell death pathway. The effects of PEITC on the redox stress was mediated via different ways in CCA and Chang cells because NAC could prevent redox stress in Chang cells, but not in KKU-M214 cells. The multiple effects of PEITC may be useful for the development of novel chemotherapy for CCA.
Phenethyl isothiocyanate; Anticancer; Cholangiocarcinoma; Mitochondrial transmembrane potential; GSH redox; Intracellular calcium
The present study was undertaken to determine efficacy of phenethyl isothiocyanate (PEITC) for sensitization of androgen-independent human prostate cancer cells (AIPC) to Docetaxel-induced apoptosis using cellular and xenograft models.
Cell viability was determined by trypan blue dye exclusion assay. Microscopy and DNA fragmentation assay was performed to quantify apoptotic cell death in cultured cells. Protein levels were determined by immunoblotting. PC-3 prostate cancer xenograft model was utilized to determine in vivo efficacy of the PEITC and/or Docetaxel treatments.
Pharmacologic concentrations of PEITC augmented Docetaxel-induced apoptosis in PC-3 and DU145 cells in association with suppression of Bcl-2 and XIAP protein levels and induction of Bax and Bak. The PEITC-Docetaxel combination was markedly more efficacious against PC-3 xenograft in vivo compared with PEITC or Docetaxel alone. Significantly higher count of apoptotic bodies were also observed in tumor sections from mice treated with the PEITC-Docetaxel combination compared with PEITC or Docetaxel alone group. The PEITC and/or Docetaxel-mediated changes in the levels of apoptosis regulating proteins in the tumor were generally consistent with the molecular alterations observed in cultured cells.
These results offer obligatory impetus to test PEITC-Docetaxel combination for the treatment of AIPC in a clinical setting.
Prostate Cancer; Phenethyl Isothiocyanate; Docetaxel; Apoptosis
Naturally-occurring phenethyl isothiocyanate (PEITC) selectively inhibits growth of cancer cells by causing apoptosis but the mechanism of cell death induction is not fully understood. We now demonstrate, for the first time, that growth factor adapter protein p66shc is indispensable for PEITC-induced apoptosis. Mouse embryonic fibroblasts derived from p66shc knockout mice were significantly more resistant to PEITC-mediated growth inhibition, cytoplasmic histone-associated apoptotic DNA fragmentation, and caspase-3 activation compared with wild-type fibroblasts. The PEITC treatment resulted in induction as well as increased Ser36 phosphorylation of p66shc in PC-3 and LNCaP human prostate cancer cells. Knockdown of p66shc protein conferred significant protection against PEITC-mediated cytoplasmic histone-associated DNA fragmentation as well as production of reactive oxygen species in both PC-3 and LNCaP cells. The PEITC-treated PC-3 and LNCaP cells exhibited increased binding of p66shc with prolyl isomerase Pin1, a protein implicated in translocation of p66shc to mitochondria. Consistent with these results, treatment of PC-3 cells with PEITC resulted in translocation of p66shc to the mitochondria as judged by immunoblotting using cytosolic and mitochondrial fractions and immunofluorescence microscopy. Growth suppression and apoptosis induction in tumor xenografts in vivo by oral administration of PEITC to the PC-3 tumor bearing male athymic mice was accompanied by statistically significant increase in the level of Ser36 phosphorylated p66shc. Collectively, these results provide novel insight into the critical role of p66shc in regulation of PEITC-induced apoptotic cell death in human prostate cancer cells.
Phenethyl isothiocyanate; p66shc; Apoptosis
The cytokine TRAIL (tumor necrotic factor-related apoptosis-inducing ligand) selectively induces apoptosis in cancer cells, but cancer stem cells (CSCs) that contribute to cancer-recurrence are frequently TRAIL-resistant. Here we examined hitherto unknown effects of the dietary anti-carcinogenic compound phenethyl isothiocyanate (PEITC) on attenuation of proliferation and tumorigenicity and on up regulation of death receptors and apoptosis in human cervical CSC.
Cancer stem-like cells were enriched from human cervical HeLa cell line by sphere-culture method and were characterized by CSC-specific markers’ analyses (flow cytometry) and Hoechst staining. Cell proliferation assays, immunoblotting, and flow cytometry were used to assess anti-proliferative as well as pro-apoptotic effects of PEITC exposure in HeLa CSCs (hCSCs). Xenotransplantation study in a non-obese diabetic, severe combined immunodeficient (NOD/SCID) mouse model, histopathology, and ELISA techniques were further utilized to validate our results in vivo.
PEITC attenuated proliferation of CD44high/+/CD24low/–, stem-like, sphere-forming subpopulations of hCSCs in a concentration- and time-dependent manner that was comparable to the CSC antagonist salinomycin. PEITC exposure-associated up-regulation of cPARP (apoptosis-associated cleaved poly [ADP-ribose] polymerase) levels and induction of DR4 and DR5 (death receptor 4 and 5) of TRAIL signaling were observed. Xenotransplantation of hCSCs into mice resulted in greater tumorigenicity than HeLa cells, which was diminished along with serum hVEGF-A (human vascular endothelial growth factor A) levels in the PEITC-pretreated hCSC group. Lung metastasis was observed only in the hCSC-injected group that did not receive PEITC-pretreatment.
The anti-proliferative effects of PEITC in hCSCs may at least partially result from up regulation of DR4 and possibly DR5 of TRAIL-mediated apoptotic pathways. PEITC may offer a novel approach for improving therapeutic outcomes in cancer patients.
Apoptosis; TRAIL; Cancer stem cells; Death receptors; Phenethyl isothiocyanate
Cruciferous vegetable constituent phenethyl isothiocyanate (PEITC) causes apoptosis in prostate cancer cells through mechanisms not fully understood. The present study was designed to determine the role of inhibitor of apoptosis (IAP) family proteins in PEITC-induced apoptosis induction.
Effect of PEITC treatment on protein and mRNA expression of IAP in cells was determined by western blotting and reverse transcription PCR, respectively. Immunohistochemistry was performed to determine the in vivo effect of PEITC administration on X-linked inhibitor of apoptosis (XIAP) and Survivin protein expression. Overexpression of desired protein was achieved by transient transfection. Cell viability was determined by trypan blue dye exclusion assay, whereas apoptosis was quantified by measurement of histone-associated DNA fragment release into the cytosol. Transwell chamber assay was used to determine cell migration.
Exposure of PC-3 and LNCaP human prostate cancer cells to PEITC resulted in downregulation of XIAP and Survivin proteins and Survivin mRNA. PEITC administration to Transgenic Adenocarcinoma of Mouse Prostate mice caused modest but significant downregulation of XIAP and Survivin proteins in the dorsolateral prostate. Proapoptotic response to PEITC was significantly attenuated by ectopic expression of XIAP and Survivin proteins. Survivin overexpression also conferred modest but significant protection against PEITC-mediated inhibition of PC-3 cell migration.
The present study demonstrates that cellular responses to PEITC, including apoptosis induction and inhibition of cell migration, in prostate cancer cells are mediated by downregulation of XIAP and/or Survivin, which may serve as valid biomarkers of PEITC response in future clinical investigations.
Phenethyl Isothiocyanate; XIAP; Survivin; Chemoprevention
Phenethyl isothiocyanate (PEITC) and sulforaphane (SF) exhibit tumor preventive activity in lung, prostate, breast and colon cancers. Our objective was to examine the effect of these two isothiocyanates on estrogen receptor-related genes, and genes related to apoptosis and cell cycle in the estrogen-dependent breast cancer cell line MCF7 and in normal human epithelial breast (HME) cells. We treated cells with 0.3 μM or 3.0 μM concentrations of PEITC or SF. In HME cells, gene expression was significantly altered for 23 genes by PEITC at a concentration of 0.3 μM and 4 genes at 3.0 μM. SF altered the expression of 16 genes at a concentration of 0.3 μM and 2 genes at 3.0 μM. In HME cells, genes altered by both PEITC and SF exhibited changes in gene expression that were similar in extent as well as direction of change. In MCF-7 cells, PEITC did not produce any significant changes in the gene expression at both treatment levels. SF produced significant changes in 7 genes, but only at the higher treatment level of 3.0 μM. Normal mammary cells exhibited more changes in the expression of estrogen receptor related genes than did breast cancer cells, and significantly these changes occurred predominantly at the low concentration of 0.3 μM, a concentration achievable by dietary input of isothiocyanates. Novel findings were the upregulation of the pro-apoptotic gene BAD and estrogen receptor beta gene in normal human mammary cells. These gene alterations observed, along with upregulation of tumor suppressors p21 and p27, may provide a protective effect to mammary cells against breast cancer.
phenethyl isothiocyanate; sulforaphane; human mammary epithelial cells; breast cancer MCF-7 cells; breast cancer prevention; gene expression
Phenethyl isothiocyanate (PEITC), a component in cruciferous vegetables, can block chemical carcinogenesis in animal models. Our objective was to determine the effect of treatment with PEITC on gene expression changes in MCF-7 human breast cancer cells in order to evaluate potential mechanisms involved in its chemopreventive effects. MCF-7 cells were treated for 48 hours with either PEITC (3 μM) or the vehicle. Total RNA was extracted from cell membrane preparations, and labeled cDNA's representing the mRNA pool were reverse-transcribed directly from total RNA isolated for use in the microarray hybridizations. Two specific human GE Array Kits (Superarray Inc.) that both contain 23 marker genes, related to signal transduction pathways or cancer/tumor suppression, plus 2 housekeeping genes (β-actin and GAPDH), were utilized. Arrays from treated and control cells (n = 4 per group) were evaluated using a Student's t-test. Gene expression was significantly induced for tumor protein p53 (p53), cyclin-dependent kinase inhibitor 1C (p57 Kip2), breast cancer Type 2 early onset (BRCA2), cAMP responsive element binding protein 2 (ATF-2), interleukin 2 (IL-2), heat shock 27 KD protein (hsp27), and CYP19 (aromatase). Induction of p57 Kip2, p53, BRCA2, IL-2, and ATF-2 would be expected to decrease cellular proliferation and increase tumor suppression and/or apoptosis. PEITC treatment produced significant alterations in some genes involved in tumor suppression and cellular proliferation/apoptosis that may be important in explaining the chemopreventive effects of PEITC.
Phenethyl isothiocyanate (PEITC) is a promising cancer chemopreventive agent commonly found in edible cruciferous vegetables. It has been implicated also for therapy, and is in clinical trial for lung cancer. Here, we provide evidence that the tumor suppressive effect of PEITC is related to its ability to induce expression of damaged DNA binding protein 2 (DDB2), a DNA repair protein involved also in apoptosis and premature senescence. DDB2 expression is attenuated in a wide variety of cancers including the aggressive colon cancers. We show that, in colon cancer cells, reactive oxygen species, which are induced by PEITC, augment expression of DDB2 through the p38MAPK/JNK pathway, independently of p53. PEITC-induced expression of DDB2 is critical for inhibition of tumor progression by PEITC. Tumors derived from DDB2-deficient colon cancer cells are refractory to PEITC-treatments, resulting from deficiencies in apoptosis and senescence. The DDB2-proficient tumors, on the other hand, respond effectively to PEITC. The results show that PEITC can be used to induce expression of DDB2, and that expression of DDB2 is critical for effective response of tumors to PEITC.
DDB2; PEITC; ROS; apoptosis; colon cancer; drug resistance; senescence
Phenethyl isothiocyanate (PEITC) is a candidate anticancer compound found in certain cruciferous vegetables. In our tumor cell xenograft model, dietary administration of PEITC (100–150 mg/kg body weight/d) inhibited androgen-responsive LNCaP human prostate cancer cell tumor growth. We found that dietary treatment with PEITC significantly inhibited tumor platelet/endothelial cell adhesion molecule (PECAM-1/CD31) expression, a marker of angiogenesis. By contrast, we did not find the inhibitory effects of PEITC on tumor growth to be associated with alteration of specific markers for apoptosis, cell proliferation or androgen receptor-mediated pathways. Consistent with in vivo results, PEITC exerted little effects on cell proliferation, cell cycle and androgen-dependent pathways. Interestingly, PEITC significantly attenuated LNCaP cell plating efficiency that correlated with inhibition of integrin family proteins integrin β1, α2 and α6 mRNA expression. Thus, PEITC may be a dietary factor that inhibits androgen-responsive prostate tumor growth indirectly by selectively targeting factors involved in the tumor microenvironment.
angiogenesis; phenethyl isothiocyanate; prevention; prostate cancer; xenograft
Phenethyl isothiocyanate (PEITC) is a promising cancer chemopreventive agent but the mechanism of its anticancer effect is not fully understood. We now demonstrate, for the first time, that PEITC treatment triggers Atg5-dependent autophagic and apoptotic cell death in human prostate cancer cells. Exposure of PC-3 (androgen-independent, p53 null) and LNCaP (androgen-responsive, wild-type p53) human prostate cancer cells to PEITC resulted in several specific features characteristic of autophagy including appearance of membranous vacuoles, formation of acidic vesicular organelles, and cleavage and recruitment of microtubule-associated protein 1 light chain 3 (LC3) to autophagosomes. A normal human prostate epithelial cell line (PrEC) was markedly more resistant towards PEITC-mediated cleavage and recruitment of LC3 compared with prostate cancer cells. Even though PEITC treatment suppressed activating phosphorylations of Akt and mTOR, which are implicated in regulation of autophagy by different stimuli, processing and recruitment of LC3 was only partially/marginally reversed by ectopic expression of constitutively active Akt or overexpression of mTOR positive regulator Rheb. The PEITC-mediated apoptotic DNA fragmentation was significantly attenuated in the presence of a pharmacological inhibitor of autophagy (3-methyl adenine). Transient transfection of LNCaP and PC-3 cells with Atg5-specific siRNA conferred significant protection against PEITC-mediated autophagy as well as apoptotic DNA fragmentation. Xenograft model using PC-3 cells and C. elegans expressing lgg-1:GFP fusion protein provided evidence for occurrence of PEITC-induced autophagy in vivo. In conclusion, the present study indicates that Atg5 plays an important role in regulation of PEITC-induced autophagic and apoptotic cell death.
Phenethyl isothiocyanate; Autophagy; Chemoprevention
Phenethyl isothiocyanate (PEITC) is a natural plant compound with chemopreventative potential against some cancers and the ability to induce apoptosis in breast cancer cells.
Female mouse mammary tumor virus–neu mice were fed a control AIN-76A diet (n = 35) or the same diet supplemented with 3 µmol PEITC/g diet (n = 33) for 29 weeks, at which time they were killed. Breast tissue sections were stained with hematoxylin and eosin for histopathological assessments, and incidence and size of macroscopic mammary tumors were assessed. Cell proliferation (Ki-67 staining), apoptosis (terminal deoxynucleotidyl transferase–mediated dUTP nick-labeling), and neoangiogenesis (CD31 staining) were determined in tumor sections. Plasma levels of transthyretin were measured in treated and control mice. Expression of proteins in mammary tumor sections was determined by immunohistochemistry. Proteomic profiling was performed by two-dimensional gel electrophoresis followed by mass spectrometry. All statistical tests were two-sided.
Administration of PEITC for 29 weeks was associated with 53.13% decreased incidence of macroscopic mammary tumors (mean tumor incidence, PEITC-supplemented diet vs control diet, 18.75% vs 40.00%, difference = –21.25%, 95% confidence interval [CI] = –43.19% to 0.69%, P = .07) and with a 56.25% reduction in microscopic mammary carcinoma lesions greater than 2mm2 (mean incidence, PEITC-supplemented diet vs control diet, 18.75% vs 42.86%, difference = –24.11%, 95% CI = –46.35% to –1.86%, P = .04). PEITC-mediated mammary cancer growth inhibition was not because of suppression of human epidermal growth factor receptor-2 expression but was associated with reduced cellular proliferation and neoangiogenesis, increased apoptosis, and altered expression of several proteins, including decreased ATP synthase in the tumor and increased plasma levels of transthyretin.
PEITC inhibits the growth of mammary cancers in a mouse model with similarities to human breast cancer progression. ATP synthase and transthyretin appear to be novel biomarkers associated with PEITC exposure.
Previously, phenethyl isothiocyanate (PEITC) and dibenzoylmethane (DBM) had been shown to inhibit intestinal carcinogenesis in Apc(Min/+) mice. In this study, we investigated the chemopreventive efficacy of PEITC and DBM in the azoxymethane (AOM)-initiated and dextran sodium sulfate (DSS)-promoted colon cancer mouse model and to compare their potential in vivo mechanisms leading to chemoprevention. The mice were fed with diet supplemented with 0.05% PEITC or 1% DBM before or after AOM initiation. Our results showed that AOM/DSS mice fed with PEITC- or DBM-supplemented diet had lower tumor incidence, lower colon tumor multiplicities and smaller polyps as compared with mice fed with the standard AIN-76A diet. PEITC was effective even after AOM initiation, whereas DBM was not as effective when fed after AOM initiation. Hematoxylin and eosin staining showed that mice fed with PEITC or DBM had attenuated loss of crypt, a marker of inflammation. To examine potential in vivo mechanisms involved in chemoprevention, western blotting was performed and showed that inhibition of growth of adenomas by PEITC was associated with an increase of apoptosis (increased cleaved caspase-3 and-7) and cell cycle arrest (increased p21). In contrast DBM's effect on cell cycle arrest and apoptosis markers was not as substantial as PEITC. Instead, DBM showed increased induction of NF-E2-related factor-2 (Nrf2) transcription factor and phase II detoxifying enzymes, which appears to correlate with in vitro cell lines results that DBM is a more potent Nrf2 activator than PEITC. In summary, our present study shows that PEITC and DBM are potent natural dietary compounds for chemoprevention of colon cancer induced by AOM/DSS and appears to be associated with different in vivo mechanism of actions. PEITC's chemopreventive effect appears to be due to induction of apoptosis and cell cycle arrest, whereas DBM's effect is due to prevention of AOM initiation via induction of Nrf2 and phase II detoxifying enzymes.
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.
Effects of phenethyl isothiocyanate (PEITC) have been investigated in human leukemia cells (U937, Jurkat, and HL-60) as well as in primary human acute myeloid leukemia (AML) cells in relation to apoptosis and cell signaling events. Exposure of cells to PEITC resulted in pronounced increase in the activation of caspase-3, -8, -9, cleavage/degradation of PARP, and apoptosis in dose- and time-dependent manners. These events were accompanied by the caspase-independent downregulation of Mcl-1, inactivation of Akt, as well as activation of Jun N-terminal kinase (JNK). Inhibition of PI3K/Akt by LY294002 significantly enhanced PEITC-induced apoptosis. Conversely, enforced activation of Akt by a constitutively active Akt construct markedly abrogated PEITC-mediated JNK activation, Mcl-1 downregulation, caspase activation, and apoptosis, and also interruption of the JNK pathway by pharmacological or genetically (e.g., siRNA) attenuated PEITC-induced apoptosis. Finally, administration of PEITC markedly inhibited tumor growth and induced apoptosis in U937 xenograft model in association with inactivation of Akt, activation of JNK, as well as downregulation of Mcl-1. Taken together, these findings represent a novel mechanism by which agents targeting Akt/JNK/Mcl-1 pathway potentiate PEITC lethality in transformed and primary human leukemia cells and inhibitory activity of tumor growth of U937 xenograft model.
phenethyl isothiocyanate; Akt; JNK; apoptosis; leukemia; xenograft
Phenethyl isothiocyanate (PEITC) is a constituent of cruciferous vegetables that has demonstrated cancer preventive activity in a number of cancer models including lung, prostate, and breast cancer. Our objective was to examine the effects of the oral administration of PEITC for 7 days on the hepatic expression of genes important in drug metabolism and toxicity in Sprague Dawley rats. The liver is the major site for the metabolism of various xenobiotics and carcinogens, and determining the effects of PEITC on the gene expression of hepatic enzymes may provide insight into mechanisms underlying the cancer preventive activity of PEITC. Using a microarray containing 282 genes, we observed that PEITC significantly up-regulated UDP-glucuronosyltransferase UGT1A6 and strongly down-regulated nicotinamide N-methyltransferase (NNMT). We also confirmed the down-regulation of NNMT by real-time quantitative RT-PCR. NNMT was recently shown to be elevated in the serum of tumor bearing patients with pancreatic, lung, and colorectal cancer, and may be involved in cell migration. Other genes that were significantly up-regulated were the drug metabolizing enzyme cyp2b15, the anti-apoptotic gene bcl2l2, and the stress regulators Gadd45b, Dnajb9, Dnajb5 and Hspb1. Our results indicate new targets that may be important in the mechanisms of the anticancer effects of PEITC. Of particular significance was the down-regulation of NNMT which may represent a new target for the treatment of a variety of cancers.
Phenethyl isothiocyanate (PEITC), an isothiocyanate abundantly found in cruciferous vegetables have been shown to induce apoptosis through MAPK pathway in prostate and colon cancer cells. In the present study, we investigate the effect of PEITC on cell cycle regulation of HT-29 colon cancer cells. Using flow cytometry and Western blot analyses, we found that PEITC significantly induced G1 cell cycle arrest in HT-29 cells. We showed that the cell cycle arrest was not related to beta-catenin translocation into the nucleus. Interestingly, inhibition of p38 attenuated the cell cycle arrest, suggesting that cell cycle arrest by PEITC was caused by the activation of MAPK pathway. Treatments of PEITC resulted in a dose-dependent down-regulation of cyclins A, D, E and pRb protein expression. The down-regulation can be attributed to the activation of the p38 pathway, since inhibition of its activities by specific inhibitor blocked PEITC’s ability to decrease the expression level of cyclins A and D and attenuate cell cycle arrest effect of PEITC. In conclusion, this study shows for the first time that PEITC can arrest HT-29 cells in G1 phase by down-regulation of cyclins through the activation of p38 MAPK signaling pathway.
cell cycle arrest; colon cancer; cyclin; PEITC; p38
Phenethyl isothiocyanate (PEITC), an effective anticancer and chemopreventive agent, has been reported to inhibit cancer cell growth through cell-cycle arrest and induction of apoptotic events in various human cancer cells models. However, whether PEITC inhibits human oral squamous cell carcinoma HSC-3 cell growth and its underlying mechanisms is still not well elucidated. In the present study, we evaluated the inhibitory effects of PEITC in HSC-3 cells and examined PEITC-modulated cell-cycle arrest and apoptosis. The contrast-phase and flow cytometric assays were used for examining cell morphological changes and viability, respectively. The changes of cell-cycle and apoptosis-associated protein levels were determined utilizing Western blotting in HSC-3 cells after exposure to PEITC. Our results indicated that PEITC effectively inhibited the HSC-3 cells' growth and caused apoptosis. PEITC induced G0/G1 phase arrest through the effects of associated protein such as p53, p21, p17, CDK2 and cyclin E, and it triggered apoptosis through promotion of Bax and Bid expression and reduction of Bcl-2, leading to decrease the levels of mitochondrial membrane potential (ΔΨm), and followed the releases of cytochrome c, AIF and Endo G then for causing apoptosis in HSC-3 cells. These results suggest that PEITC could be an antitumor compound for oral cancer therapy.