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 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.
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
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.
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
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) 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) 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), 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 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 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), 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) 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.
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.
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.
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.
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.
Mitochondria may represent the organelle target of the isothiocyanates, indicating that the isothiocyanates may be mitochondria-interacting agents to inhibit carcinogenesis.
Phenethyl isothiocyanate; PEITC; Mitochondria; Prostate; Organelle target
Naturally-occurring chemopreventive agent phenethyl isothiocyanate (PEITC), derived primarily from watercress, has been shown to inhibit cell growth and induce apoptosis in cancer cells. In this study, we examined the potential of PEITC in enhancing cisplatin-induced apoptosis in cervical cancer cells. HeLa cells were exposed to PEITC, cisplatin or both. Pretreatment of cells with PEITC strongly enhanced cisplatin-induced cytotoxicity. PEITC activated the mitogen-activated protein kinases, including JNK, ERK, and p38. The synergistic induction of apoptosis was significantly attenuated by MEK1/2 inhibitor U0126, but not by JNK or p38 inhibitor, suggesting that ERK activation is responsible for the synergistic effect. We found that NF-κB signaling pathway is not involved in the synergistic effect. Sulforaphane and benzyl isothiocyanate, two other members of the isothiocyanate family, also sensitize HeLa cells to apoptosis induced by cisplatin. Furthermore, we found that the synergistic effect was not seen in normal cells. Finally, we demonstrated that Noxa induction was associated with apoptosis induced by PEITC plus cisplatin. Taken together, this study shows that PEITC can sensitize cancer cells to apoptosis induced by cisplatin and this effect is mediated through ERK activation, suggesting the potential of PEITC to be used as an adjuvant with cisplatin in combination therapeutic treatments.
Phenethyl isothiocyanate; cisplatin; apoptosis; ERK activation; sensitization
High mortality rates in ovarian cancer are largely a result of resistance to currently used chemotherapies. Expanding therapies with a variety of drugs has the potential to reduce this high mortality rate. Metformin and phenethyl isothiocyanate (PEITC) are both potentially useful in ovarian cancer, and they are particularly attractive because of their safety.
Cell proliferation of each drug and drug combination was evaluated by hemacytometry with Trypan blue exclusion or Sytox green staining for cell death. Levels of total and cleaved PARP were measured by Western blot. General cellular and mitochondrial reactive oxygen species were measured by flow cytometry and live cell confocal microscopy with the fluorescent dyes dihydroethidine and MitoSOX.
Individually, metformin and PEITC each show inhibition of cell growth in multiple ovarian cancer cell lines. Alone, PEITC was also able to induce apoptosis, whereas metformin was primarily growth inhibitory. Both total cellular and mitochondrial reactive oxygen species were increased when treated with either metformin or PEITC. The growth inhibitory effects of metformin were reversed by methyl succinate supplementation, suggesting complex I plays a role in metformin's anti-cancer mechanism. PEITC's anti-cancer effect was reversed by N-acetyl-cysteine supplementation, suggesting PEITC relies on reactive oxygen species generation to induce apoptosis. Metformin and PEITC together showed a synergistic effect on ovarian cancer cell lines, including the cisplatin resistant A2780cis.
Here we show that when used in combination, these drugs are effective in both slowing cancer cell growth and killing ovarian cancer cells in vitro. Furthermore, the combination of these drugs remains effective in cisplatin resistant cell lines. Novel combinations such as metformin and PEITC show promise in expanding ovarian cancer therapies and overcoming the high incidence of cisplatin resistant cancers.
Metformin; Phenethyl isothiocyanate; Ovarian cancer
Naturally occurring isothiocyanates (ITC) from cruciferous vegetables are widely studied for their cancer chemopreventive effects. Here we investigated the effects of ITC on Toll-like receptor (TLR) signaling, and found that two most promising ITCs, phenethyl isothiocyanate (PEITC) and D,L-sulforaphane (SFN), have differential effects on dsRNA mediated innate immune signaling through TLR3. PEITC preferentially inhibited TLR3 mediated IRF3 signaling and downstream gene expression in vivo and in vitro, whereas SFN caused inhibition of TLR3 mediated NF-κB signaling and downstream gene expression. Mechanistically, PEITC inhibited ligand (dsRNA) dependent dimerization of TLR3 resulting in inhibition of signaling through IRF3. On the other hand, SFN did not disrupt TLR3 dimerization indicating that it affects further downstream pathway resulting in NF-κB inhibition. In order to examine the biological significance of these findings in the context of anti-tumor activities of these compounds, we used two approaches: (a) first, we showed that dsRNA mediated apoptosis of tumor cells via TLR3 was inhibited in the presence of PEITC, whereas this response was augmented by SFN treatment; (b) second, in a separate assay measuring anchorage independent growth and colony formation by immortalized fibroblasts we made similar observations. Here again, PEITC antagonized dsRNA mediated inhibition of colony formation while SFN enhanced the inhibition. These results indicate biologically relevant functional differences between two structurally similar ITC and may provide important insights in therapeutic development of these compounds targeted to specific cancer.
The effect of phenethyl isothiocyanate (PEITC), a component of cruciferous vegetables, on the initiation and progression of cancer was investigated in a chemically induced estrogen-dependent breast cancer model. Breast cancer was induced in female Sprague Dawley rats (8 weeks old) by the administration of N-methyl nitrosourea (NMU). Animals were administered 50 or 150 µmol/kg oral PEITC and monitored for tumor appearance for 18 weeks. The PEITC treatment prolonged the tumor-free survival time and decreased the tumor incidence and multiplicity. The time to the first palpable tumor was prolonged from 69 days in the control, to 84 and 88 days in the 50 and 150 µmol/kg PEITC-treated groups. The tumor incidence in the control, 50 µmol/kg, and 150 µmol/kg PEITC-treated groups was 56.6%, 25.0% and 17.2%, while the tumor multiplicity was 1.03, 0.25 and 0.21, respectively. Differences were statistically significant (p < 0.05) from the control, but there were no significant differences between the two dose levels. The intratumoral capillary density decreased from 4.21 ± 0.30 vessels per field in the controls to 2.46 ± 0.25 in the 50 µmol/kg and 2.36 ± 0.23 in the 150 µmol/kg PEITC-treated animals. These studies indicate that supplementation with PEITC prolongs the tumor-free survival, reduces tumor incidence and burden, and is chemoprotective in NMU-induced estrogen-dependent breast cancer in rats. For the first time, it is reported that PEITC has anti-angiogenic effects in a chemically induced breast cancer animal model, representing a potentially significant mechanism contributing to its chemopreventive activity.
phenethyl isothiocyanate; estrogen-dependent breast cancer model; anti-angiogenic effects; N-methyl nitrosourea; PEITC; NMU
The development of effective chemopreventive agents against cigarette smoke-induced lung cancer could be greatly facilitated by suitable laboratory animal models, such as animals treated with the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). In the current study, we established a novel lung cancer model in Wistar rats treated with NNK. Using this model, we assessed the effects of two chemopreventive agents, aspirin and phenethyl isothiocyanate (PEITC), on tumor progression.
First, rats were treated with a single-dose of NNK by intratracheal instillation; control rats received iodized oil. The animals were then sacrificed on the indicated day after drug administration and examined for tumors in the target organs. PCNA, p63 and COX-2 expression were analyzed in the preneoplastic lung lesions. Second, rats were treated with a single-dose of NNK (25 mg/kg body weight) in the absence or presence of aspirin and/or PEITC in the daily diet. The control group received only the vehicle in the regular diet. The animals were sacrificed on day 91 after bronchial instillation of NNK. Lungs were collected and processed for histopathological and immunohistochemical assays.
NNK induced preneoplastic lesions in lungs, including 33.3% alveolar hyperplasia and 55.6% alveolar atypical dysplasia. COX-2 expression increased similarly in alveolar hyperplasia and alveolar atypical dysplasia, while PCNA expression increased more significantly in the latter than the former. No p63 expression was detected in the preneoplastic lesions. In the second study, the incidences of alveolar atypical dysplasia were reduced to 10%, 10% and 0%, respectively, in the aspirin, PEITC and aspirin and PEITC groups, compared with 62.5% in the carcinogen-treated control group. COX-2 expression decreased after dietary aspirin or aspirin and PEITC treatment. PCNA expression was significantly reduced in the aspirin and PEITC group.
(1) A single dose of 25 mg/kg body weight NNK by intratracheal instillation is sufficient to induce preneoplastic lesions in Wistar rat lungs. (2) COX-2 takes part in NNK-induced tumorigenesis but is not involved in proliferation. (3) Aspirin and PEITC have protective effects in the early stages of tumor progression initiated by NNK.
The isothiocyantes (ITCs) have long been known to possess chemopreventive activities for varieties of neoplasms including breast cancer, but the molecular mechanism by which ITCs prevent breast cancer development has not been established. In this study, we investigated the effects of benzyl and phenethyl isothiocyanate (BITC and PEITC) on the estrogen-stimulated growth of estrogen receptor alpha (ERα)-positive breast cancer MCF7 and T-47D cells. BITC and PEITC inhibited estrogen-stimulated cell growth and reduced the expression levels of ERα in MCF7 and T-47D cells in a dose and time -dependent and reversible manner. In addition, BITC and PEITC also abrogated the transcriptional activity of ERα and hence inhibited estrogen-stimulated expression of the estrogen responsive gene, pS2. These results demonstrated that BITC and PEITC function as potent ERα disruptors to abrogate mitogenic estrogen signaling in ER-positive breast cancer cells, which provides a molecular explanation for the growth inhibitory function of ITCs in breast cancer development, and a rational for further exploration of ITCs as chemopreventive agents for human mammary carcinogenesis.
isothiocyanate; breast cancer; estrogen receptor
This study was undertaken to investigate the mechanism by which phenethyl isothiocyanate (PEITC), a natural compound from cruciferous vegetables, exhibits antitumor effect on prostate cancer cells. Cell proliferation, cell cycle, western blot, gene transfer and reporter assays were used to test the effects of PEITC on the growth and IL6/JAK/STAT3 pathway in prostate cancer. The result showed that PEITC significantly inhibited DU145 cell proliferation in a dose-dependent manner and induced the cell arrest at G2-M phase. PEITC inhibited both constitutive and interleukin 6 (IL-6)-induced STAT3 activity in DU145 cells. IL-6-stimulated phosphorylation of JAK2, an STAT3 upstream kinase, was also attenuated by PEITC. Moreover, an antioxidant reagent, N-acetyl-l-cysteine (NAC) which suppresses reactive oxygen species (ROS) generation, reversed the early inhibitory effects of PEITC on cell proliferation, constitutive or IL-6-mediated JAK-STAT3 phosphorylation in PCa cells. Taken together, our data demonstrated that PEITC can inhibit the activation of the JAK-STAT3 signal-cascade in prostate cancer cells and the underlying mechanism may be partially involved with blocking cellular ROS production during the early stage of the signaling activation by IL-6.
Phenethyl isothiocyanate; IL-6; STAT3; Androgen independent growth
Isothiocyanates are natural compounds found in consumable cruciferous vegetables. They have been shown to inhibit chemical carcinogenesis by a wide variety of chemical carcinogens in animal models. Recent studies have also shown that isothiocyanates have antitumor activity, inhibiting the growth of several types of cultured human cancer cells. Our previous study showed that PEITC inhibited human leukemia cells growth by inducing apoptosis. However, the effect of isothiocyanates on lung cancer cell metastasis has not been studied. In the present study, we investigated the inhibitory effects of BITC and PEITC on metastatic potential of highly metastatic human lung cancer L9981 cells.
Cell migration and invasion were measured by wound healing assay and transwell chemotaxis assay. Expression of metastasis-related genes was assessed by quantitative RT-PCR and Western blotting. The mechanisms of action were evaluated by flow cytometry, reporter assay and Western blotting.
Our data showed that both BITC and PEITC inhibited L9981 cell growth in a dose-dependent manner, the IC50 values were 5.0 and 9.7 μM, respectively. Cell migrations were reduced to 8.1% and 16.5% of control, respectively; and cell invasions were reduced to 2.7% and 7.3% of control, respectively. Metastasis-related genes MMP-2, Twist and β-catenin were also modulated. BITC and PEITC inhibited cell survival signaling molecules Akt and NFκB activation. Moreover, BITC and PEITC increased ROS generation and caused GSH depletion. Pretreatment with NAC blocked BITC and PEITC induced ROS elevation and NFκB inhibition.
Our results indicated that BITC and PEITC suppress lung cancer cell metastasis potential by modulation of metastasis-related gene expression, inhibition of Akt/NFκB pathway. Induction of oxidative stress may play an important role.