Enhancement of apoptotic activities on brain cancer cells via the combination of γ-tocotrienol and jerantinine A

Tocotrienol isoforms: The molecular mechanisms underlying their effects in cancer therapy and their implementation in clinical trials

Tocotrienols are found in a variety of natural sources, like rice bran, annatto seeds and palm oil, and have been shown to have several health-promoting properties, particularly against chronic diseases such as cancer. The incidence of cancer is rapidly increasing around the world, not only a result of continued aging and population growth, but also due to the adoption of aspects of the Western lifestyle, such as high-fat diets and low-physical activity. The literature provides strong evidence that tocotrienols are able to inhibit the growth of various cancers, including breast, lung, ovarian, prostate, liver, brain, colon, myeloma and pancreatic cancers. These findings, along with the reported safety profile of tocotrienols in healthy human volunteers, encourage further research into these compounds' potential use in cancer prevention and treatment. The current review provided detailed information about the molecular mechanisms of action of different tocotrienol isoforms in various cancer models and evaluated the potential therapeutic effects of different vitamin E analogues on important cancer hallmarks, such as cellular proliferation, apoptosis, angiogenesis and metastasis. MEDLINE/PubMed and Scopus databases were used to identify recently published articles that investigated the anticancer effects of vitamin E derivatives in various types of cancer in vitro and in vivo along with clinical evidence of adjuvant chemopreventive benefits. Following an overview of pre-clinical studies, we describe several completed and ongoing clinical trials that are paving the way for the successful implementation of tocotrienols in cancer chemotherapy.

Effect of pyridoxine or cobalamin supplementation on apoptosis and cell cycle progression in a human glioblastoma cell line

Glioblastoma is the most aggressive type of brain tumor, with current therapies failing to significantly improve patient survival. Vitamins have important effects on cellular processes that are relevant for tumor development and progression.

AIM

The present study explored the effect of pyridoxine or cobalamin supplementation on the viability and cell cycle progression of human glioblastoma cell line U-87 MG.

METHOD

Cell cultures were treated with increasing concentrations of pyridoxine or cobalamin for 24-72 h. After supplementation, cell viability and cell cycle progression were assessed by spectrophotometry and flow cytometry. Analysis of Bcl-2 and active caspase 3 expression in supplemented cells was performed by western blot.

RESULT

The results show that pyridoxine supplementation decreases cell viability in a dose and time dependent manner. Loss of viability in pyridoxin-supplemented cells is probably related to less cell cycle progression, higher active caspase 3 expression and apoptosis. In addition, Bcl-2 expression did not appear to be altered by vitamin supplementation, but active caspase 3 expression was significantly increased in pyridoxine-, but not cobalamin-supplemented cells, furthermore, cobalamin inhibited the pyridoxine cytotoxicity in the cell viability assay when combined.

CONCLUSION

The results suggest that pyridoxine supplementation promotes apoptosis in human glioblastoma-derived cells and may be useful to enhance the effect of cytotoxic therapies in vivo.

Naturally derived indole alkaloids targeting regulated cell death (RCD) for cancer therapy: from molecular mechanisms to potential therapeutic targets

Regulated cell death (RCD) is a critical and active process that is controlled by specific signal transduction pathways and can be regulated by genetic signals or drug interventions. Meanwhile, RCD is closely related to the occurrence and therapy of multiple human cancers. Generally, RCD subroutines are the key signals of tumorigenesis, which are contributed to our better understanding of cancer pathogenesis and therapeutics. Indole alkaloids derived from natural sources are well defined for their outstanding biological and pharmacological properties, like vincristine, vinblastine, staurosporine, indirubin, and 3,3′-diindolylmethane, which are currently used in the clinic or under clinical assessment. Moreover, such compounds play a significant role in discovering novel anticancer agents. Thus, here we systemically summarized recent advances in indole alkaloids as anticancer agents by targeting different RCD subroutines, including the classical apoptosis and autophagic cell death signaling pathways as well as the crucial signaling pathways of other RCD subroutines, such as ferroptosis, mitotic catastrophe, necroptosis, and anoikis, in cancer. Moreover, we further discussed the cross talk between different RCD subroutines mediated by indole alkaloids and the combined strategies of multiple agents (e.g., 3,10-dibromofascaplysin combined with olaparib) to exhibit therapeutic potential against various cancers by regulating RCD subroutines. In short, the information provided in this review on the regulation of cell death by indole alkaloids against different targets is expected to be beneficial for the design of novel molecules with greater targeting and biological properties, thereby facilitating the development of new strategies for cancer therapy.

Biomarkers Regulated by Lipid-Soluble Vitamins in Glioblastoma

Glioblastoma (GBM), a highly lethal form of adult malignant gliomas with little clinical advancement, raises the need for alternative therapeutic approaches. Lipid-soluble vitamins have gained attention in malignant brain tumors owing to their pleiotropic properties and their anti-cancer potential have been reported in a number of human GBM cell lines. The aim of this paper is to systematically review and describe the roles of various biomarkers regulated by lipid-soluble vitamins, such as vitamins A, D, E, and K, in the pathophysiology of GBM. Briefly, research articles published between 2005 and 2021 were systematically searched and selected from five databases (Scopus, PubMed, Ovid MEDLINE, EMBASE via Ovid, and Web of Science) based on the study’s inclusion and exclusion criteria. In addition, a number of hand-searched research articles identified from Google Scholar were also included for the analysis. A total of 40 differentially expressed biomarkers were identified from the 19 eligible studies. The results from the analysis suggest that retinoids activate cell differentiation and suppress the biomarkers responsible for stemness in human GBM cells. Vitamin D appears to preferentially modulate several cell cycle biomarkers, while vitamin E derivatives seem to predominantly modulate biomarkers related to apoptosis. However, vitamin K1 did not appear to induce any significant changes to the Raf/MEK/ERK signaling or apoptotic pathways in human GBM cell lines. From the systematic analysis, 12 biomarkers were identified that may be of interest for further studies, as these were modulated by one or two of these lipid-soluble vitamins.

Revisiting the therapeutic potential of tocotrienol

The therapeutic potential of the tocotrienol group stems from its nutraceutical properties as a dietary supplement. It is largely considered to be safe when consumed at low doses for attenuating pathophysiology as shown by animal models, in vitro assays, and ongoing human trials. Medical researchers and the allied sciences have experimented with tocotrienols for many decades, but its therapeutic potential was limited to adjuvant or concurrent treatment regimens. Recent studies have focused on targeted drug delivery by enhancing the bioavailability through carriers, self-sustained emulsions, nanoparticles, and ethosomes. Epigenetic modulation and computer remodeling are other means that will help increase chemosensitivity. This review will focus on the systemic intracellular anti-cancer, antioxidant, and anti-inflammatory mechanisms that are stimulated and/or regulated by tocotrienols while highlighting its potent therapeutic properties in a diverse group of clinical diseases.

Enjoy Carefully: The Multifaceted Role of Vitamin E in Neuro-Nutrition

Vitamin E is often associated with health benefits, such as antioxidant, anti-inflammatory and cholesterol-lowering effects. These properties make its supplementation a suitable therapeutic approach in neurodegenerative disorders, for example, Alzheimer’s or Parkinson’s disease. However, trials evaluating the effects of vitamin E supplementation are inconsistent. In randomized controlled trials, the observed associations often cannot be substantiated. This could be due to the wide variety of study designs regarding the dosage and duration of vitamin E supplementation. Furthermore, genetic variants can influence vitamin E uptake and/or metabolism, thereby distorting its overall effect. Recent studies also show adverse effects of vitamin E supplementation regarding Alzheimer’s disease due to the increased synthesis of amyloid β. These diverse effects may underline the inhomogeneous outcomes associated with its supplementation and argue for a more thoughtful usage of vitamin E. Specifically, the genetic and nutritional profile should be taken into consideration to identify suitable candidates who will benefit from supplementation. In this review, we will provide an overview of the current knowledge of vitamin E supplementation in neurodegenerative disease and give an outlook on individualized, sustainable neuro-nutrition, with a focus on vitamin E supplementation.

Potentiation of in vitro apoptotic effects of δ-Tocotrienol and Jerantinine A on human lung adenocarcinoma cells

Introduction: The apoptotic effects of single-compound and combined sub-effective concentrations of δ-tocotrienol and jerantinine A on human lung adenocarcinoma (A549) cells were investigated. Methods: Assays including cell viability, histochemical and immunofluorescence staining techniques, flow cytometry and enzyme activity were used. Results: The combination of δ-tocotrienol with jerantinine A at sub-effective concentrations induced a synergistic effect and improved selective toxicity towards cancerous A549 cells over normal lung fibroblast (MRC5) cells compared to the single-compound jerantinine. Morphological features of apoptosis were evident on treated A549 cells. Combined sub-effective concentrations of δ-tocotrienol with jerantinine A induced a predominantly G2/M cell cycle arrest and characterised by a disruption of microtubular networks mediated via caspase 8, 9 and 3 enzymatic activities. Conclusion: These findings demonstrated improved potency in vitro and reduced dose-related toxicity of jerantinine A to normal cells through prospective combined treatment between low-concentration δ-tocotrienol and jerantinine A for lung cancer.

Utilization of Vitamin E Analogs to Protect Normal Tissues While Enhancing Antitumor Effects

Despite advances in radiation delivery techniques, side effects of radiation therapy due to radiation exposure of normal tissues are common and can limit the deliverable dose to tumors. Significant interests lie in pharmacologic modifiers that may protect against normal tissue toxicity from cancer treatment while simultaneously enhancing the tumor response to therapy. While no such treatments are available in the clinic, this is an area of active preclinical and clinical research. This review summarizes research studies that provide evidence to indicate that tocotrienols, natural forms of vitamin E, are potent radiation protectors and may also have antitumor effects. Hence, several current clinical trials test tocotrienols as concomitant treatment in cancer therapies.

Molecular Mechanisms of Action of Tocotrienols in Cancer: Recent Trends and Advancements

Tocotrienols, found in several natural sources such as rice bran, annatto seeds, and palm oil have been reported to exert various beneficial health promoting properties especially against chronic diseases, including cancer. The incidence of cancer is rapidly increasing around the world not only because of continual aging and growth in global population, but also due to the adaptation of Western lifestyle behaviours, including intake of high fat diets and low physical activity. Tocotrienols can suppress the growth of different malignancies, including those of breast, lung, ovary, prostate, liver, brain, colon, myeloma, and pancreas. These findings, together with the reported safety profile of tocotrienols in healthy human volunteers, encourage further studies on the potential application of these compounds in cancer prevention and treatment. In the current article, detailed information about the potential molecular mechanisms of actions of tocotrienols in different cancer models has been presented and the possible effects of these vitamin E analogues on various important cancer hallmarks, i.e., cellular proliferation, apoptosis, angiogenesis, metastasis, and inflammation have been briefly analyzed.

Induction of apoptosis by chalepin through phosphatidylserine externalisations and DNA fragmentation in breast cancer cells (MCF7)

AIMS

Chalepin, a naturally occurring compound isolated from Ruta angustifolia have been shown to exert a promising anticancer activity through various mechanisms. Hence, the need to investigate the apoptotic inducing ability of chalepin in MCF7 cells by various detection assays.

MATERIALS AND METHODS

Cytotoxicity screening of chalepin against MCF7 cells was conducted using SRB assay. Apoptosis induction was examined by established morphological and biochemical assays including phase contrast and Hoechst/PI staining fluorescence microscope. Similarly, Annexin-V/FITC and TUNEL assays were conducted using flow cytometry whereas caspase-3 activity was evaluated using microplate reader.

KEY FINDINGS

The result indicates remarkable cytotoxic activity against MCF7 cells, whereas it shows moderate cytotoxic activity against MDA-MB231 cells. Interestingly, chalepin did not present any toxicity against MRC5 normal cell line. Morphological examination using both phase contrast and fluorescence microscope displays typical apoptotic features such as membrane blebbing, DNA fragmentation, chromatin condensation and apoptotic bodies' formation following chalepin treatment against MCF7 cells at different concentration for 48 h. Apoptosis induction is significantly associated with externalisation of phosphatidylserine, and DNA fragmentation in MCF7 cells chalepin treated cells when compared with control. The protein expressions of caspase-8, 9 and cleaved PARP1 were upregulated which correlated well with increased caspase-3 activity.

SIGNIFICANCE

From our recent findings, chalepin was able to induced apoptosis in MCF7 cells and therefore, could be evaluated further as a potential source of anticancer agent for cancer treatment such as breast cancer.

Tocotrienols Modulate a Life or Death Decision in Cancers

Malignancy often arises from sophisticated defects in the intricate molecular mechanisms of cells, rendering a complicated molecular ground to effectively target cancers. Resistance toward cell death and enhancement of cell survival are the common adaptations in cancer due to its infinite proliferative capacity. Existing cancer treatment strategies that target a single molecular pathway or cancer hallmark fail to fully resolve the problem. Hence, multitargeted anticancer agents that can concurrently target cell death and survival pathways are seen as a promising alternative to treat cancer. Tocotrienols, a minor constituent of the vitamin E family that have previously been reported to induce various cell death mechanisms and target several key survival pathways, could be an effective anticancer agent. This review puts forward the potential application of tocotrienols as an anticancer treatment from a perspective of influencing the life or death decision of cancer cells. The cell death mechanisms elicited by tocotrienols, particularly apoptosis and autophagy, are highlighted. The influences of several cell survival signaling pathways in shaping cancer cell death, particularly NF-κB, PI3K/Akt, MAPK, and Wnt, are also reviewed. This review may stimulate further mechanistic researches and foster clinical applications of tocotrienols via rational drug designs.

Vitamin E and its anticancer effects

Vitamin E is a lipid soluble vitamin comprising of eight natural isoforms, namely, α, β, δ, γ isoforms of tocopherol and α, β, δ, γ isoforms of tocotrienol. Many studies have been performed to elucidate its role in cancer. Until last decade, major focus was on alpha tocopherol and its anticancer effects. However, major clinical trials using alpha-tocopherol like SELECT trial and ATBC trial did not yield meaningful results. Hence there was a shift of focus to gamma-tocopherol, delta-tocopherol and tocotrienol. Unlike alpha-tocopherol, gamma-tocopherol and delta-tocopherol can scavenge reactive nitrogen species in addition to reactive oxygen species. Antiangiogenic effect, inhibition of HMG CoA reductase enzyme and inhibition of NF-κB pathway make the anti-cancer effects of tocotrienols unique compared to other vitamin E isoforms. Preclinical research on non-alpha tocopherol isoforms of vitamin E showed promising data on their anticancer effects. In this review, we deal with the current understanding on the potential mechanisms involved in the anticancer effects of vitamin E and the controversies in this field over last three decades. We also highlight the need to conduct further research on the anticancer effects of non-alpha-tocopherol isoforms in larger population and clinical setting.

In Vitro Antioxidant and Cytotoxic Activities of 18 Plants from the Erkowit Region, Eastern Sudan

We investigated the antioxidant potential and cytotoxicity towards human CCRF-CEM leukemia cells of 57 extracts obtained from 18 plants collected in the Erkowit region, eastern Sudan. The antioxidant activity was determined by measuring the radical scavenging effects against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and N,N-dimethyl-p-phenylendiamine (DMPD), metal-chelation capacity, ferric-reducing (FRAP) and phosphomolibdenum-reducing antioxidant power (PRAP) methods using ELISA microtiter assays. Total phenol and flavonoid amounts of the extracts were determined spectrophotometrically. Cytotoxicity towards CCRF-CEM cells was evaluated by the resazurin reduction assay. Geranium favosum followed by Kalanchoe glaucescens, Malva parviflora, Aizoon canariense, and Coleus barbatus, respectively, possessed the highest antioxidant activity among the studied plants. Chrozophora oblongifolia and K. glaucescens exerted considerable cytotoxicity against CCRF-CEM leukemia cells. These plants may serve as source for the further development of natural antioxidant and antitumor agents.