tocotrienol--delta and Prostatic-Neoplasms

Prostate cancer (PCa) represents the fifth cause of cancer death in men. Currently, chemotherapeutic agents for the treatment of cancers, including PCa, mainly inhibit tumor growth by apoptosis induction. However, defects in apoptotic cellular responses frequently lead to drug resistance, which is the main cause of chemotherapy failure. For this reason, trigger non-apoptotic cell death might represent an alternative approach to prevent drug resistance in cancer. Several agents, including natural compounds, have been shown to induce necroptosis in human cancer cells. In this study we evaluated the involvement of necroptosis in anticancer activity of delta-tocotrienol (δ-TT) in PCa cells (DU145 and PC3). Combination therapy is one tool used to overcome therapeutic resistance and drug toxicity. Evaluating the combined effect of δ-TT and docetaxel (DTX), we found that δ-TT potentiates DTX cytotoxicity in DU145 cells. Moreover, δ-TT induces cell death in DU145 cells that have developed DTX resistance (DU-DXR) activating necroptosis. Taken together, obtained data indicate the ability of δ-TT to induce necroptosis in both DU145, PC3 and DU-DXR cell lines. Furthermore, the ability of δ-TT to induce necroptotic cell death may represent a promising therapeutical approach to overcome DTX chemoresistance in PCa.

Topics: Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Docetaxel; Drug Resistance, Neoplasm; Humans; Male; Necroptosis; Prostatic Neoplasms

Vitamin E compounds, consisting of α, β, γ, and δ forms of tocopherols and tocotrienols, display different cancer preventive activities in experimental models. Tocotrienols may have higher potential for clinical use due to their lower effective doses in laboratory studies. However, most studies on tocotrienols have been carried out using cancer cell lines. Strong data from animal studies may encourage the use of tocotrienols for human cancer prevention research. To examine the cancer inhibitory activity of different vitamin E forms, we first investigated their inhibitory activities of different vitamin E forms in prostate cancer cell lines. We found that δ-tocotrienol (δT3) was the most effective form in inhibiting cell growth at equivalent doses. Because of this in vitro potency, δT3 was further studied using prostate-specific Pten-/- (Ptenp-/-) mice. We found that 0.05% δT3 in diet reduced prostate adenocarcinoma multiplicity by 32.7%, featuring increased apoptosis and reduced cell proliferation. The inhibitory effect of 0.05% δT3 in diet was similar to that of 0.2% δ-tocopherol (δT) in diet reported previously. Our further study on the δT3-induced transcriptome changes indicated that δT3 inhibited genes in blood vessel development in the prostate of Ptenp-/- mice, which was confirmed by IHC. Together, our results demonstrate that δT3 effectively inhibits the development of prostate adenocarcinoma in Ptenp-/- mice, which involves inhibition of proliferation and angiogenesis and promotion of apoptosis.. We demonstrated that δ-tocotrienol is the most active vitamin E form in inhibiting the growth of several prostate cancer cell lines. In transgenic Ptenp-/- mice, δ-tocotrienol inhibited the formation of prostate cancer. This result would encourage and help design clinical studies for the application of δ-tocotrienol for prostate cancer prevention.

Topics: Animals; Cell Transformation, Neoplastic; Humans; Male; Mice; Prostate; Prostatic Neoplasms; Vitamin E

The Warburg effect is commonly recognized as a hallmark of nearly all tumors. In prostate cancer (PCa), it has been shown to be driven by PTEN loss- and Akt hyperactivation-associated upregulation of hexokinase 2 (HK2). δ-Tocotrienol (δ-TT) is an extensively studied antitumor compound; however, its role in affecting PCa glycolysis is still unclear. Herein, we demonstrated that δ-TT inhibits glucose uptake and lactate production in PTEN-deficient LNCaP and PC3 PCa cells, by specifically decreasing HK2 expression. Notably, this was accompanied by the inhibition of the Akt pathway. Moreover, the nutraceutical could synergize with the well-known hypoglycemic agent metformin in inducing PCa cell death, highlighting the crucial role of the above metabolic phenotype in δ-TT-mediated cytotoxicity. Collectively, these results unravel novel inhibitory effects of δ-TT on glycolytic reprogramming in PCa, thus providing new perspectives into the mechanisms of its antitumor activity and into its use in combination therapy.

Topics: Cell Line, Tumor; Glycolysis; Hexokinase; Humans; Male; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Vitamin E

The therapeutic options for castration-resistant prostate cancer (CRPC) are still limited. Natural bioactive compounds were shown to possess pro-death properties in different tumors. We previously reported that δ-tocotrienol (δ-TT) induces apoptosis, paraptosis and autophagy in CRPC cells. Here, we investigated whether δ-TT might exert its activity by impairing mitochondrial functions. We demonstrated that, in PC3 and DU145 cells, δ-TT impairs mitochondrial respiration and structural dynamics. In both cell lines, δ-TT triggers mitochondrial Ca

Topics: Apoptosis; Cell Line, Tumor; Humans; Male; Mitochondria; Prostatic Neoplasms; Reactive Oxygen Species; Vitamin E

A hallmark of the progression of prostate cancer to advanced disease is the acquisition of androgen-independent growth. This malignant phenotype is characterized by resistance to conventional treatments and predisposes to formation of hypoxic regions containing stem-like cancer cells. Unfortunately, an effective therapy to target prostate cancer stem cells under hypoxia has not yet been established. In this report, we studied whether δ-tocotrienol (T3), a vitamin E family member that has exhibited the most potent anti-cancer activity, could suppress the survival of prostate cancer stem-like cells.. PC3 stem-like cells were isolated from PC3 parental cells using a three-dimensional culture system. The stemness of the isolated PC3 stem-like cells was confirmed by evaluation of resistance to an anticancer agent (docetaxel) and tumor formation capacity in a xenograft model. The effects of δ-T3 on PC3 stem-like cells under a hypoxia condition were examined by WST-8 (cell viability), real-time reverse transcription-polymerase chain reaction (PCR) and western blotting.. δ-T3 demonstrated a cytotoxic effect on prostate cancer stem-like cells in a dose dependent manner and a reduction in the protein levels of hypoxia-inducible factor (HIF)-1α and HIF-2α. Additionally, a specific inhibitor toward HIF-1α induced cytotoxicity on PC3 cells, but selective inhibition of HIF-2α had no effect.. Overall, these results suggest that δ-T3 could inhibit the survival of prostate cancer stem-like cells under hypoxia, primarily through the inactivation of HIF-1α signaling.

Topics: Adaptation, Physiological; Animals; Cell Hypoxia; Cell Survival; Dose-Response Relationship, Drug; Gene Expression Regulation, Neoplastic; Humans; Hypoxia; Male; Mice, Inbred BALB C; Mice, Nude; Neoplastic Stem Cells; Prostatic Neoplasms; SOXB1 Transcription Factors; Tumor Cells, Cultured; Vitamin E; Vitamins; Xenograft Model Antitumor Assays

Tocotrienols (T3s) and tocopherols (Tocs) are both members of the vitamin E family. It is known that δ-tocotrienol (δ-T3) has displayed the most potent anti-cancer activity amongst the tocotrienols. On the other hand, γ-tocopherol (γ-Toc) is reported to have a protective effect against prostate cancer. Therefore, we investigated whether the combination of γ-Toc and δ-T3 could strengthen the inhibitory effect of δ-T3 on prostate cancer cell growth. In this study the effect of combined δ-T3 (annatto T3 oil) and γ-Toc (Tmix, γ-Toc-rich oil) therapy was assessed against human androgen-dependent prostate cancer cells (LNCaP). We found that combined treatment of δ-T3 (10 μM) and γ-Toc (5 μM) resulted in reinforced anti-prostate cancer activity. Specifically, cell cycle phase distribution analysis revealed that in addition to G1 arrest caused by the treatment with δ-T3, the combination of δ-T3 with γ-Toc induced G2/M arrest. Enhanced induction of apoptosis by the combined treatment was also observed. These findings indicate that combination of δ-T3 and γ-Toc significantly inhibits prostate cancer cell growth due to the simultaneous cell cycle arrest in the G1 phase and G2/M phase.

Topics: Anticarcinogenic Agents; Antineoplastic Agents, Phytogenic; Apoptosis; Bixaceae; Carotenoids; Cell Line, Tumor; Cell Proliferation; Cell Survival; Chromans; G1 Phase; G2 Phase; Humans; Male; Osmolar Concentration; Plant Extracts; Prostatic Neoplasms; Prostatic Neoplasms, Castration-Resistant; Vitamin E

Prostate cancer is one of the most frequently occurring cancers and often acquires the potential of androgen-independent growth as a malignant phenotype. Androgen-independent prostate cancer has severe chemoresistance towards conventional chemotherapeutic agents, so a new treatment approach is required for curing such prostate cancer. In this context, the present study was undertaken to check if annatto tocotrienol (main component δ-tocotrienol) could suppress cell growth in human prostate cancer (PC3, androgen-independent type) cells via the inhibition of Src and Stat3. The tocotrienol showed cytotoxic effects on PC3 cells in a dose-dependent manner, and the effect depended on G1 arrest in the cell cycle and subsequent induction of apoptosis. In a cytotoxic dose, the tocotrienol suppressed cellular growth via the simultaneous inhibition of Src and Stat3. Similarly, the treatment combination of both Src and Stat3 inhibitors induced cytotoxic effects in PC3 cells in an additive manner compared to each by itself. With respect to cell cycle regulation and the induction of apoptosis, the combination treatment showed a similar effect to that of the tocotrienol treatment. These results suggest that annatto tocotrienol effectively induces cytotoxicity in androgen-independent prostate cancer cells via the suppression of Src and Stat3.

Topics: Antineoplastic Agents; Apoptosis; Bixaceae; Carotenoids; Cell Cycle; Cell Line, Tumor; Genes, src; Humans; Male; Plant Extracts; Prostatic Neoplasms; STAT3 Transcription Factor; Tocotrienols; Vitamin E; Vitamins

Vitamin E comprises 8 functionally unique isoforms and may be a suitable candidate for the adjuvant treatment of prostate cancer. In this study, we examined the ability of 2 vitamin E isoforms [α-tocotrienol (γ-TT) and δ-tocotrienol (δ-TT)] and 4 synthetic derivatives [γ- and δ-tocotrienol succinate (γ-TS, δ-TS), α-tocopheryl polyethylene glycol succinate (TPGS), and α-tocopheryl polyethylene glycol ether (TPGS-e)] of vitamin E to induce cell death in AR- (DU145 and PC-3) and AR+ (LNCaP) prostate cancer cell lines. Our results show that δ-TT and TPGS-e are the most effective isoform and synthetic derivative, respectively, of all compounds examined. Overall, the results of our study suggest that isoforms and synthetic derivatives of vitamin E have the potency to trigger both caspase-dependent and -independent DNA damage and dominant caspase-independent programmed cell death. The capacity of vitamin E to trigger caspase-independent programmed cell death suggests that it may be useful in the chemotherapy of prostate cancer since it may prevent the tumor resistance commonly associated with the use of classical chemotherapeutic agents that trigger caspase-dependent programmed cell death.

Topics: Apoptosis; Caspase 3; Caspases; Cell Line, Tumor; DNA Damage; Drug Screening Assays, Antitumor; Etoposide; Humans; Isomerism; Male; Poly(ADP-ribose) Polymerases; Polyethylene Glycols; Prostatic Neoplasms; Tocotrienols; Vitamin E

There is growing evidence showing that prostate cancer cells have perturbed cholesterol homoeostasis, accumulating cholesterol to promote cell growth. Consequently, cholesterol-lowering drugs such as statins are being evaluated in prostate cancer treatment. Furthermore, natural products such as betulin (from birch tree bark) and tocotrienol (a minor form of vitamin E) have been shown to lower cholesterol levels. Using these drugs and oxysterols, we have determined which aspects of cholesterol homoeostasis should be targeted in prostate cancer, e.g. cellular cholesterol levels are increased by the transcription factor SREBP-2 (sterol-regulatory-element-binding protein isoform 2), whereas LXR (liver X receptor) promotes cholesterol efflux. Whereas betulin exerted non-specific effects on cell viability, tocotrienols produced a strong direct correlation between SREBP-2 activity and cell viability. Mechanistically, tocotrienols lowered SREBP-2 activity by degrading mature SREBP-2 independently of the proteasome. In contrast, no correlation was seen between LXR activity and cell viability, implying that SREBP-2 is a better target than LXR for prostate cancer treatment. Lastly, androgen-dependent and -independent LNCaP cells were both sensitive to tocotrienols. Overall, this suggests that tocotrienols and other drugs targeting the SREBP-2 pathway are a potential therapeutic option for prostate cancer.

Topics: Animals; Antineoplastic Agents, Phytogenic; Cell Line, Tumor; Cell Survival; CHO Cells; Cholesterol; Chromans; Cricetinae; Cricetulus; Humans; Intracellular Signaling Peptides and Proteins; Liver X Receptors; Male; Membrane Proteins; Mutant Proteins; Neoplasm Proteins; Orphan Nuclear Receptors; Prostatic Neoplasms; Recombinant Proteins; Sterol Regulatory Element Binding Protein 2; Tocotrienols; Triterpenes; Vitamin E

Current observations in the literature suggest that vitamin E may be a suitable candidate for cancer chemotherapy. To investigate this further, we examined the ability of the vitamin E natural homologs [alpha-, beta-, gamma-, delta-tocopherols (alpha-TOC, beta-TOC, gamma-TOC, delta-TOC) and alpha-, beta-, gamma-, delta-tocotrienols (alpha-TT, beta-TT, gamma-TT, delta-TT)] and their corresponding succinate synthetic derivatives [alpha-, beta-, gamma-, delta-tocopheryl succinates and alpha-, beta-, gamma-, delta-tocotrienyl succinates (alpha-TS, beta-TS, gamma-TS, delta-TS)] to induce cell death in AR- (DU145 and PC3) and AR+ (LNCaP) prostate cancer cell lines. The most effective of all the natural homologs of vitamin E was determined to be delta-TT, whereas delta-TS was the most potent of all the natural and synthetic compounds of vitamin E examined. Both gamma-TT and delta-TT induced caspase activity selectively in AR+ LNCaP cells, suggesting a possible role for AR for the activation of caspase-dependent programmed cell death (CD-PCD). More important, however, gamma-TT, delta-TT, gamma-TS, and delta-TS activated dominant caspase-independent programmed cell death (CI-PCD) in all prostate cancer cell lines examined. Thus, vitamin E homologs and synthetic derivatives may find applications in the treatment of prostate tumors that are resistant to caspase-activating therapeutic agents.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Bixaceae; Carotenoids; Caspase Inhibitors; Caspases; Cell Line, Tumor; Cell Proliferation; Chemotherapy, Adjuvant; Drug Screening Assays, Antitumor; Drug Synergism; Humans; Inhibitory Concentration 50; Isomerism; Male; Palm Oil; Plant Extracts; Plant Oils; Prostatic Neoplasms; Receptors, Androgen; Time Factors; Vitamin E