Effect of vitamin E succinate and a cAMP-stimulating agent on the expression of c-myc and N-myc and H-ras in murine neuroblastoma cells

Discovery of Alpha-Tocopheryl Succinate as a Cancer Treatment Agent Led to the Development of Methods to Potentially Improve the Efficacy of Cancer Therapy

The discovery of alpha-tocopheryl succinate (alpha-TS) as a cancer therapeutic agent markedly stimulated research with or without tumor therapeutic agents on cancer cells and normal cells. Results showed that alpha-TS treatment induced apoptosis in cancer cells and enhanced the apoptotic effects of tumor therapeutic agents on tumor cells in a synergistic manner without affecting the growth of normal cells. Liposomal alpha-TS was more effective than alpha-TS. Some tumors are difficult to treat with chemotherapeutic agents while some become resistant of such treatment. Using a nanotechnology technique, it was demonstrated that alpha-TS conjugated with a chemotherapeutic agent enhanced the levels of apoptosis and restored the sensitivity of tumor cells to that chemotherapeutic agent. The mechanisms of action of alpha-TS alone or in combination with therapeutic agents include the following: (a) inhibition of the expression of oncogenes C-myc and H-ras; (b) alterations in the levels of expression of numerous genes; (c) activation of caspases; (d) inhibition of angiogenesis; (e) destabilization of mitochondria and lysosomes; (f) inhibition of production of production of prostaglandin E2 (PGE2) and PGE2-mediated pro-inflammatory responses; (g) reduction of survivin signaling pathway; and (h) reduction of CD47 expression on the tumor cell surface causing enhancement of phagocytic activity of macrophages leading to engulfment of tumor cells. Despite impressive results in cell culture and in animal models, no studies with alpha-TS alone or in combination with cancer therapeutic agents in human cancer resistant to these therapies have been performed.

Nanocarrier-Based Delivery of SN22 as a Tocopheryl Oxamate Prodrug Achieves Rapid Tumor Regression and Extends Survival in High-Risk Neuroblastoma Models

Despite the use of intensive multimodality therapy, the majority of high-risk neuroblastoma (NB) patients do not survive. Without significant improvements in delivery strategies, anticancer agents used as a first-line treatment for high-risk tumors often fail to provide clinically meaningful results in the settings of disseminated, recurrent, or refractory disease. By enhancing pharmacological selectivity, favorably shifting biodistribution, strengthening tumor cell killing potency, and overcoming drug resistance, nanocarrier-mediated delivery of topoisomerase I inhibitors of the camptothecin family has the potential to dramatically improve treatment efficacy and minimize side effects. In this study, a structurally enhanced camptothecin analog, SN22, reversibly coupled with a redox-silent tocol derivative (tocopheryl oxamate) to allow its optimally stable encapsulation and controlled release from PEGylated sub-100 nm nanoparticles (NP), exhibited strong NB cell growth inhibitory activity, translating into rapid regression and durably suppressed regrowth of orthotopic, MYCN-amplified NB tumors. The robust antitumor effects and markedly extended survival achieved in preclinical models recapitulating different phases of high-risk disease (at diagnosis vs. at relapse with an acquired loss of p53 function after intensive multiagent chemotherapy) demonstrate remarkable potential of SN22 delivered in the form of a hydrolytically cleavable superhydrophobic prodrug encapsulated in biodegradable nanocarriers as an experimental strategy for treating refractory solid tumors in high-risk cancer patients.

α-Tocopheryl Succinate Affects Malignant Cell Viability, Proliferation, and Differentiation

The widespread occurrence of malignant tumors motivates great attention to finding and investigating effective new antitumor preparations. Such preparations include compounds of the vitamin E family. Among them, α-tocopheryl succinate (vitamin E succinate (VES)) has the most pronounced antitumor properties. In this review, various targets and mechanisms of the antitumor effect of vitamin E succinate are characterized. It has been shown that VES has multiple intracellular targets and effects, and as a result VES is able to induce apoptosis in tumor cells, inhibit their proliferation, induce differentiation, prevent metastasizing, and inhibit angiogenesis. However, VES has minimal effects on normal cells and tissues. Due to the variety of targets and selectivity of action, VES is a promising agent against malignant neoplasms. More detailed studies in this area can contribute to development of effective and safe chemotherapeutic preparations.

Multifunctional dendrimers modified with alpha-tocopheryl succinate for targeted cancer therapy

Multifunctional generation 5-poly(amidoamine) dendrimers can be used as a platform to conjugate covalently alpha-tocopheryl succinate for targeted cancer therapy.

Tocopherol succinate: modulation of antioxidant enzymes and oncogene expression, and hematopoietic recovery

PURPOSE

A class of naturally occurring isoforms of tocopherol (tocols) was shown to have varying degrees of protection when administered before radiation exposure. We recently demonstrated that α-tocopherol succinate (TS) is a potential radiation prophylactic agent. Our objective in this study was to further investigate the mechanism of action of TS in mice exposed to (60)Co γ-radiation.

METHODS AND MATERIALS

We evaluated the effects of TS on expression of antioxidant enzymes and oncogenes by quantitative RT-PCR in bone marrow cells of (60)Co γ-irradiated mice. Further, we tested the ability of TS to rescue and repopulate hematopoietic stem cells by analyzing bone marrow cellularity and spleen colony forming unit in spleen of TS-injected and irradiated mice.

RESULTS

Our results demonstrate that TS modulated the expression of antioxidant enzymes and inhibited expression of oncogenes in irradiated mice at different time points. TS also increased colony forming unit-spleen numbers and bone marrow cellularity in irradiated mice.

CONCLUSIONS

Results provide additional support for the observed radioprotective efficacy of TS and insight into mechanisms.

Mechanism of apoptosis with the involvement of calpain and caspase cascades in human malignant neuroblastoma SH-SY5Y cells exposed to flavonoids

Neuroblastoma is the most common extracranial solid tumor in children causing death at pre-school age, as no cure has yet been developed. We investigated the proteolytic mechanisms for apoptosis in human malignant (N-type) neuroblastoma SH-SY5Y cells following exposure to flavonoids such as apigenin (APG), (-)-epigallocatechin (EGC), (-)-epigallocatechin-3-gallate (EGCG) and genistein (GST). We found decrease in viability of SH-SY5Y cells with an increase in dose of APG, EGC, EGCG and GST. Predominantly apoptosis occurred following exposure of SH-SY5Y cells to 50 microM APG, 50 microM EGC, 50 microM EGCG and 100 microM GST for 24 hr. Apoptosis was associated with increases in intracellular free [Ca(2+)] and Bax:Bcl-2 ratio, mitochondrial release of cytochrome c and activation of caspase-9, calpain and caspase-3. Induction of apoptosis with APG and GST showed activation of caspase-12 as well. Activation of caspase-3 could cleave the inhibitor-of-caspase-activated DNase (ICAD) to release and translocate caspase-3-activated DNase (CAD) to the nucleus. Activation of caspase-8 cleaved Bid to truncated Bid (tBid) in cells treated with EGC and EGCG. EGC and EGCG induced apoptosis with caspase-8 activation and mitochondria-mediated pathway, whereas APG and GST caused apoptosis via an increase in intracellular free [Ca(2+)] with calpain activation and mitochondria-mediated pathway. Activation of different proteases for cell death was confirmed using caspase-8 inhibitor II, calpeptin (calpain inhibitor), caspase-9 inhibitor I and caspase-3 inhibitor IV. Thus, plant-derived flavonoids cause cell death with activation of proteolytic activities of calpain and caspases in SH-SY5Y cells, and therefore serve as potential therapeutic agents for controlling the growth of neuroblastoma.

RRR-α-Tocopherol succinate down-regulates oncogenic Ras signaling

alpha-Tocopherol succinate (TS), an analogue of vitamin E, has growth-inhibitory activity in a wide spectrum of in vitro and in vivo cancer models. Here, we report that modulation of oncogenic Ras is associated with TS activity. TS inhibits the proliferation and induces apoptosis of NIH3T3 cells stably transfected with oncogenic K-Ras and H-Ras, but not NIH3T3 cells expressing empty vector. TS treatment resulted in decreased Ras protein levels in oncogenic Ras expressing NIH3T3 cells but not in parental NIH3T3 cells. Treatment with TS suppressed the levels of phospho-Akt and phospho-Erk1/2 in oncogenic Ras expressing NIH3T3 cells. Overexpression of constitutively active phosphoinositide-3-kinase, Akt, and Mek1/2 significantly attenuated TS growth inhibition of oncogenic Ras-transformed NIH3T3 mouse fibroblast cell lines. In addition, transcriptional targets of oncogenic Ras such as c-Myc, cyclin D1, and E2F1 were down-regulated by TS in oncogenic Ras-expressing cells. The above TS effects on oncogenic Ras signaling were also observed in endogenous oncogenic K-Ras expressing HCT 116 (human colon cancer) and MDA-MB-231 (human breast cancer) cells. Taken together, these data show that TS down-regulation of the Ras signaling pathways that are mediated by Mek/Erk and phosphoinositide-3-kinase/Akt plays, at least in part, a critical role in TS inhibition of proliferation and survival of transformed cells. This data supports further investigation of the chemopreventive and therapeutic potential of TS in tumors that are dependent on activated Ras signaling and identifies phosphor-Erk and phosphor-Akt as potential biomarkers of TS activity.

Alpha-tocopheryl succinate, the most effective form of vitamin E for adjuvant cancer treatment: a review

In 1982, it was established that alpha-tocopheryl succinate (alpha-TS) was the most effective form of vitamin E in comparison to alpha-tocopherol, alpha-tocopheryl acetate and alpha-tocopheryl nicotinate in inducing differentiation, inhibition of proliferation and apoptosis in cancer cells, depending upon its concentration. During the last two decades, several studies have confirmed this observation in rodent and human cancer cells in culture and in vivo (animal model). The most exciting aspect of this alpha-TS effect is that it does not affect the proliferation of most normal cells. In spite of several studies published on the anti-cancer properties of alpha-TS, the value of this form of vitamin E has not drawn significant attention from researchers and clinicians. Therefore, a critical review on the potential role of alpha-TS in the management of cancer is needed. In addition, such a review can also provide in-depth analysis of existing literature on this subject. alpha-TS treatment causes extensive alterations in gene expression; however, only some can be attributed to differentiation, inhibition of proliferation and apoptosis. alpha-TS also enhances the growth-inhibitory effect of ionizing radiation, hyperthermia, some chemotherapeutic agents and biological response modifiers on tumor cells, while protecting normal cells against some of their adverse effects. Thus, alpha-TS alone or in combination with dietary micronutrients can be useful as an adjunct to standard cancer therapy by increasing tumor response and possibly decreasing some of the toxicities to normal cells.

Altered expression of genes regulating cell growth, proliferation, and apoptosis during adenosine 3',5'-cyclic monophosphate-induced differentiation of neuroblastoma cells in culture

An elevation of the intracellular levels of adenosine 3',5'-cyclic monophosphate (cAMP) induces terminal differentiation in neuroblastoma (NB) cells in culture; however, genetic alterations during differentiation have not been fully identified. To investigate this, we used Mouse Genome U74A microarray containing approximately 6000 functionally characterized genes to measure changes in gene expression in murine NB cells 30 min and 4, 24, and 72 h after treatment with cAMP-stimulating agents. Based on the time of increase in differentiated functions and their status (reversible versus irreversible) after treatment with cAMP-stimulating agents, the induction of differentiation in NB cells was divided into three distinct phases: initiation (about 4 h after treatment when no increase in differentiated functions is detectable), promotion (about 24 h after treatment when an increase in differentiated functions occurs, but they are reversible upon the removal of cAMP), and maintenance (about 72 h after treatment when differentiated functions are maximally expressed, but they are irreversible upon the removal of cAMP). Results showed that alterations in expression of genes regulating cell growth, proliferation, apoptosis, and necrosis occurred during cAMP-induced differentiation of NB cells. Genes that were upregulated during the initiation, promotion, or maintenance phase were called initiators, promoters, or maintainers of differentiation. Genes that were downregulated during the initiation, promotion, or maintenance phase were called suppressors of initiation, promotion, or maintenance phase. Genes regulating growth may act as initiators, promoters, maintainers, or suppressors of these phases. Genes regulating cell proliferation may primarily act as suppressors of promotion. Genes regulating cell cycle may behave as suppressors of initiation or promotion, whereas those regulating apoptosis and necrosis may act as initiators or suppressors of initiation or promotion. The fact that genetic signals for differentiation occurred 30 min after treatment with cAMP, whereas cell-cycle genes were downregulated at a later time, suggests that decision for NB cells to differentiate is made earlier and not at the cell-cycle stage, as commonly believed.

D-alpha-tocopheryl succinate (vitamin E) enhances radiation-induced chromosomal damage levels in human cancer cells, but reduces it in normal cells

OBJECTIVE

The purpose of this study was to measure and compare the effect of d-alpha-tocopheryl succinate (alpha-TS) in modifying radiation-induced chromosomal damage in human normal cells and cancer cells in culture.

METHODS

Three human normal fibroblast cell lines (GM2149, AG1522 and HF19) and three human cancer cell lines, cervical cancer (HeLa) and ovarian carcinoma cells (OVGI and SKOV3) were treated with alpha-TS (37.6 microM) 20 hours before 100 cGy gamma-irradiation. After 30 minutes of irradiation, colcemid was added and cells were fixed. One hundred randomly selected metaphase cells were scored for the presence of chromatid gaps and breaks. To study the cellular accumulation of alpha-TS. cells were incubated in the presence of alpha-TS (18.8 and 37.6 microM) for 24 hours, and alpha-TS was extracted with hexane using a-tocopheryl acetate as an internal standard. The levels of alpha-TS were determined by HPLC.

RESULTS

Results showed that alpha-TS induced chromosomal damage in both human cervical cancer cells and ovarian cancer cells, but not in human normal fibroblasts in culture. In addition, alpha-TS enhanced the level of radiation-induced chromosomal damage in cancer cells, but it protected normal cells against such damage. Both cancer cells and normal cells accumulated similar levels of alpha-TS, suggesting that increased sensitivity of cancer cells to alpha-TS is acquired during transformation.

CONCLUSION

The use of alpha-TS during radiation therapy may improve the efficacy of radiation therapy by enhancing tumor response and decreasing some of the toxicities on normal cells.

Pros and cons of antioxidant use during radiation therapy

Radiation therapy is one of the major treatment modalities in the management of human cancer. While impressive progress like more accurate dosimetry and more precise methods of radiation targeting to tumor tissue has been made, the value of radiation therapy in tumor control may have reached a plateau. At present, two opposing hypotheses regarding the use of antioxidants during radiation therapy have been proposed. One hypothesis states that supplementation with high doses of multiple micronutrients including high dose dietary antioxidants (vitamins C and E, and carotenoids) may improve the efficacy of radiation therapy by increasing tumor response and decreasing some of its toxicity on normal cells. The other hypothesis suggests that antioxidants (dietary or endogenously made) should not be used during radiation therapy, because they would protect cancer cells against radiation damage. Each of these hypotheses is based on different conceptual frameworks that are derived from results obtained from specific experimental designs, and thus, each may be correct within its parameters. The question arises whether any of these concepts and experimental designs can be used during radiation therapy to improve the management of human cancer by this modality. This review has analyzed published data that are used in support of each hypothesis, and has revealed that the current controversies can be resolved, if the results obtained from one experimental design are not extrapolated to the other. This review has also discussed the scientific rationale for a micronutrient protocol that includes high doses of dietary antioxidants (vitamin C, vitamin E succinate and natural beta-carotene) which can be used adjunctively with radiation therapy.

Role of extracellular signal-regulated kinase pathway in RRR-alpha-tocopheryl succinate-induced differentiation of human MDA-MB-435 breast cancer cells

RRR-alpha-tocopheryl succinate (vitamin E succinate, VES) induces differentiation of human breast cancer cells. Previous studies ruled out transforming growth factor-beta and c-jun N-terminal kinase involvement in VES-induced differentiation but implicated extracellular signal-regulated kinases (ERKs). Here we show that dominant-negative mutants of either mitogen-activated protein kinase kinase (MEK) 1 or ERK1 blocked VES-induced differentiation of MDA-MB-435 cells, as measured by induction of cytokeratin 18 and p21 (Waf1/Cip1) proteins. Blockage of c-jun protein expression using c-jun antisense oligonucleotides or expression of an inducible dominant-negative c-jun mutant protein inhibited VES-induced differentiation. Elevated expression of wild-type c-jun alone was sufficient to induce cellular differentiation. A role for p21 (Waf1/Cip1) is implicated, in that p21 antisense oligomers blocked VES-induced differentiation. In summary, MEK1, ERK1, the transcription factor c-jun, and the cyclin-dependent kinase inhibitor p21 (Waf1/Cip1) play a part in VES-induced differentiation of human MDA-MB-435 breast cancer cells.

In vitro and in vivo inhibition of SK-N-MC neuroblastoma growth using cyclic nucleotide phosphodiesterase inhibitors

The effect of cyclic nucleotide phosphodiesterase (PDE) inhibitors Zaprinast and DC-TA-46 has been tested on SK-N-MC neuroblastoma growth. Antiproliferative activity of the tested drugs was assayed both in vitro and in the xenograft model of nude mice. In clonal density experiments, the IC50 value was 3.3 microM for Zaprinast and 1.9 microM for DC-TA-46, while 7.5 microM BCNU alkylating agent was required to obtain the same effect. SK-N-MC cells xenografted in the nude mouse showed that the administration of Zaprinast and DC-TA-46 caused a significant 50% decrease of the tumour weight. These data demonstrate that PDE inhibitors may be useful for at least reducing tumour growth; they may be of interest for further evaluation as alternative molecules in the design of multiple agent protocols for neuroblastoma treatment.

Identifying genes involved in regulating differentiation of neuroblastoma cells

The genes regulating the induction of differentiation in neurons are not definitively known. Some neuronal tumors retain the ability to differentiate into mature, functional neurons in response to pharmacological agents, despite the presence of genetic anomalies. We hypothesized that some of the genes whose expression is altered between undifferentiated and differentiated states may be those responsible for inducing differentiation. To investigate this, we used a mouse neuroblastoma (NB) cell line, NBP(2), in which > or =90% of the cells in the culture terminally differentiate upon elevation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels. Gene expression was analyzed using cDNA array blots containing 588 known genes. mRNA from cultures of undifferentiated and differentiated NB cells was used to make cDNA probes for blot hybridization. We identified several genes that are predominantly expressed in either undifferentiated or differentiated NB cells. In addition, numerous genes are moderately up- or down-regulated during differentiation of NB cells. We identified the N-myc protooncogene, cyclin B1, and protease nexin 1 as genes that are expressed in undifferentiated NB cells and whose levels are significantly down-regulated upon differentiation. In contrast, the c-fes and c-fos protooncogenes and the RAG-1 gene activator are genes whose expression is significantly up-regulated during differentiation of NB cells. These findings were confirmed by RT-PCR analysis. The transcript size and expression level of N-myc, cyclin B1, protease nexin 1, c-fes, and c-fos were verified by Northern blotting. These genes may represent key mediators involved in the regulation of NB cell differentiation.

Evidence for role of transforming growth factor-beta in RRR-alpha-tocopheryl succinate-induced apoptosis of human MDA-MB-435 breast cancer cells

MDA-MB-435 human breast cancer cells treated with 10 micrograms/ml of RRR-alpha-tocopheryl succinate (vitamin E succinate, VES) for one, two, three, and four days exhibit 9%, 19%, 51%, and 73% apoptotic cells, respectively. Likewise, cells cultured for one, two, and three days with conditioned media (CM) obtained from MDA-MB-435 cells treated with VES exhibit 10%, 36%, and 74% apoptosis, respectively. A quantitative luciferase-based assay showed CM from VES-treated cells collected at 24 and 48 hours after treatment initiation to contain 75 and 32 pg of active transforming growth factor-beta (TGF-beta), respectively, per 10(6) cells. Although purified TGF-beta 1 is not an effective apoptotic agent for MDA-MD-435 cells, cotreatment of the cells for three days with suboptimal levels of VES (2.5 and 5 micrograms/ml) + 10 ng/ml of purified TGF-beta 1 enhanced apoptosis by 66% and 68%, respectively. Interference of the TGF-beta-signaling pathway by transient transfection of MDA-MB-435 cells with antisense oligomers to TGF-beta type II receptor (TGF-beta R-II) blocked VES-induced apoptosis. Likewise, addition of neutralizing antibodies to TGF-beta 1 or to all three mammalian isoforms of TGF-beta (TGF-beta 1, -beta 2, -beta 3) blocked VES- and CM-induced apoptosis. Furthermore, inhibitors of TGF-beta conversion from an inactive latent form to a biologically active form inhibited VES-induced apoptosis. In summary, the ability to reduce apoptosis by blocking TGF-beta or the TGF-beta receptor-signaling pathway with antisense oligomers or ligand-neutralizing antibodies or prevention of activation of TGF-beta indicates a role for TGF-beta signaling in VES-induced apoptosis.

RRR-alpha-tocopheryl succinate induces apoptosis in avian retrovirus-transformed lymphoid cells

The RRR-alpha-tocopheryl succinate form of vitamin E [vitamin E succinate (VES)] inhibits the proliferation of avian reticuloendotheliosis virus-transformed RECC-UTC4-1 (C4-1) lymphoblastoid cells in a dose-dependent manner, blocks the cells in the G2/M cell cycle phase, and induces the cells to undergo apoptosis. Apoptosis was documented by demonstrating changes that are characteristic of this type of cell death, including morphological analyses of chromatin condensation by 4',6-diamidine-2'-phenylindole dihydrochloride (DAPI) staining using scanning confocal and traditional fluorescent microscopy; flow cytometry analyses of propidium iodide-labeled DNA showing fragmented DNA as a pre-G1 peak; two-color flow cytometry analyses of intact cells labeled first by the TUNEL procedure (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end-labeled DNA stained with fluorescein isothiocyanate-labeled avidin) and then by propidium iodide demonstrating fragmented DNA; and electrophoresis of DNA showing a DNA ladder created by internucleosomal DNA fragmentation. The percentage of apoptotic cells was determined by DAPI staining and showed 11%, 27%, and 49% of cells to be apoptotic after treatment with 10 micrograms/ml VES for one, two, and three days, respectively. Analyses of mRNA levels of genes that have been implicated in the apoptotic process, namely, bcl-2, c-myc, and c-jun, revealed no change in bcl-2, decreases in c-myc mRNA levels after 36 hours of treatment, and increases in c-jun mRNA levels within four hours after treatment. Western immunoblotting analyses of protein levels for the transcription factors c-Myc and c-Jun showed normal levels of c-Myc at early time points and decreased levels at 24 and 48 hours after treatment. c-Jun increased as early as 6 hours after treatment and returned to lower (yet still elevated over control) levels by 48 hours. To determine possible functional consequences of increased c-Jun expression, gel electrophoretic mobility assays were conducted that showed increased AP-1 binding at 24 and 48 hours after treatment. These data show that VES induces apoptosis in reticuloendotheliosis virus-transformed lymphoid cells and suggest that decreases of c-Myc protein and increases of c-Jun protein and DNA binding capacity may be playing a role in VES-mediated events leading to apoptosis in this cell type.

RRR-alpha-tocopheryl succinate enhances TGF-beta 1, -beta 2, and -beta 3 and TGF-beta R-II expression by human MDA-MB-435 breast cancer cells

The proliferation of MDA-MB-435 human breast cancer cells was inhibited by RRR-alpha-tocopheryl succinate (vitamin E succinate, VES). Conditioned media (CM) from VES growth-inhibited cells contained potent antiproliferative activity, part of which is contributed by transforming growth factor-beta (TGF-beta) isoforms. Antibody neutralization analysis, employing TGF-beta isoform-specific antibody reagents, showed that TGF-beta 1, -beta 2, and -beta 3 were present in the CM from VES-treated cells. Culturing MDA-MB-435 cells with VES did not alter the levels of constitutively expressed 2.4-kb TGF-beta 1, 3.0- and 4.0-kb TGF-beta 2, or 1.2- and 3.5-kb TGF-beta 3 mRNA transcripts. Inhibition of DNA synthesis by MDA-MB-435 cells was increased by combinations of suboptimal levels of VES and purified TGF-beta 1. VES-treated MDA-MB-435 cells exhibited enhanced binding of radiolabeled TGF-beta 1, and Western immunoblotting analyses showed that VES treatment enhanced TGF-beta type II receptor protein expression. TGF-beta type I receptor protein levels were not modified by VES treatments. Although the mRNA transcript for the 5.5-kb TGF-beta type II receptor was upregulated after four hours of treatment with VES, this treatment did not modify the 6.5-kb TGF-beta type I or the 6.5-kb TGF-beta type II receptor mRNAs. Results demonstrate that biologically active TGF-beta 1, -beta 2, -beta 3 and levels of TGF-beta type II receptor expressed by human breast cancer cells are enhanced by VES treatment.

Increased number of sciatic sensory neurons in vitamin-E-deficient rats

The number and morphometric characteristics of sciatic sensory neurons were studied in Vitamin-E-deficient rats. Horseradish peroxidase (HRP) was injected into the sciatic nerves of normal and vitamin-E-deficient rats of the same age, and retrogradely labeled sensory neurons were counted and measured. The study was also carried out in rats that had previously undergone sciatic nerve crush, in order to observe the effects of axotomy on primary sensory neurons. In vitamin-E-deficient rats the number of sciatic sensory neurons was significantly higher than normal, with an increase of about 30%, in agreement with a previous finding concerning total population of primary sensory neurons in lumbar dorsal root ganglia (DRGs) of vitamin-E-deficient rats. The increase involved the small cell classes in particular. Axotomy induced similar percentages of neuron loss in normal and in vitamin-E-deficient rats (about 40%). In the latter, death affected small cell classes in particular--that is, the same classes that had increased in number in vitamin-E-deficient rats by comparison with controls. These results, together with previous findings, suggest that neurogenesis may occur in DRGs of vitamin-E-deficient rats.

p53 in the anticancer mechanism of vitamin E

Immunohistochemical techniques were used to study the expression of "wild type" p53 and "mutant" p53 in experimental cancer inhibition by vitamin E. The cancer model used was the squamous cell carcinoma of hamster buccal pouch induced by the carcinogen 7,12 dimethylbenz(a)anthracene (DMBA). Cancer development was studied sequentially for 8-14 weeks and specimens prepared for histological and immunohistochemical interpretation. Primary antibodies used were monoclonal antibodies for "wild type" and "mutant" p53. Specificity of antibodies was confirmed by flow cytometry. Peroxidase-antiperoxidase staining was used on the tissue specimens. In those animals receiving vitamin E the buccal pouch tumour development was significantly inhibited and there was a notable expression of "wild type" p53. There was also a relative absence of "mutant" p53 in the buccal pouch lesions of animals receiving vitamin E. These observations suggest that vitamin E may inhibit cancer formation by stimulating the expression of a cancer suppressor gene.

Posttranscriptional down-regulation of ras oncogene expression by inhibitors of cellular glutathione

Alterations in intracellular glutathione (GSH) content are known to affect intrinsic responses to ionizing radiation. More recently, it became apparent that radiation responses may depend also on the expression of specific oncogenes, including ras. These findings, suggesting a possible link between GSH and ras, led us to examine the effect of various GSH modulators on ras expression. Treatment of c-Ha-ras-transformed NIH 3T3 cells with L-buthionine S'R'-sulfoximine, dimethylfumarate, or N',N'-1,3-bis(trans-4-hydroxycyclohexyl)-N'-nitrosourea resulted in dose- and time-dependent reduction in ras mRNA steady-state levels followed by a decrease in ras-encoded p21 protein production. The effect on ras correlated with the extent of GSH decline, was common to different members of the ras family, and was independent of the mode of oncogene activation or cell phenotype. Indeed, similar drug effects were observed with murine cells in which overexpression of the c-Ha-ras proto-oncogene was due to transcriptional activation (PR4, nontumorigenic) or gene amplification (NIH 136, tumorigenic) and with malignant cells expressing a mutated Ha-ras (RS504). Moreover, N-ras, EJras, and Ki-ras in human tumor cells were similarly affected. Molecular analysis revealed a significant decrease in ras mRNA half-life in cells subjected to GSH inhibition, an effect that required de novo protein synthesis, but there was no change in the rate of gene transcription. These results indicate that pharmacological manipulation of cellular GSH content can down-regulate ras expression at the posttranscriptional level by destabilizing ras transcripts. The potential clinical implications are discussed.

Cyclic AMP inhibits c-Ha-ras protooncogene expression and DNA synthesis in rat aortic smooth muscle cells

Fetal bovine serum (10%) markedly increased ras transcript levels in growth-arrested (G0-synchronized) smooth muscle cells by 8 h. This elevation was maintained for up to 18 h and returned to pre-stimulation levels within 24 h. Challenge of quiescent cells with serum in the presence of dibutyryl cyclic AMP (1-100 microM, a growth inhibitor for smooth muscle cells, attenuated serum-induced elevation of c-Ha-ras in a dose dependent fashion and prevented progression of the cells into S phase. These results demonstrate that expression of c-Ha-ras in rat aortic smooth muscle cells is cell-cycle dependent and that cAMP prevents the induction of this protooncogene by serum.

Posttranscriptional down-regulation of ras oncogene expression by inhibitors of cellular glutathione

Alterations in intracellular glutathione (GSH) content are known to affect intrinsic responses to ionizing radiation. More recently, it became apparent that radiation responses may depend also on the expression of specific oncogenes, including ras. These findings, suggesting a possible link between GSH and ras, led us to examine the effect of various GSH modulators on ras expression. Treatment of c-Ha-ras-transformed NIH 3T3 cells with L-buthionine S'R'-sulfoximine, dimethylfumarate, or N',N'-1,3-bis(trans-4-hydroxycyclohexyl)-N'-nitrosourea resulted in dose- and time-dependent reduction in ras mRNA steady-state levels followed by a decrease in ras-encoded p21 protein production. The effect on ras correlated with the extent of GSH decline, was common to different members of the ras family, and was independent of the mode of oncogene activation or cell phenotype. Indeed, similar drug effects were observed with murine cells in which overexpression of the c-Ha-ras proto-oncogene was due to transcriptional activation (PR4, nontumorigenic) or gene amplification (NIH 136, tumorigenic) and with malignant cells expressing a mutated Ha-ras (RS504). Moreover, N-ras, EJras, and Ki-ras in human tumor cells were similarly affected. Molecular analysis revealed a significant decrease in ras mRNA half-life in cells subjected to GSH inhibition, an effect that required de novo protein synthesis, but there was no change in the rate of gene transcription. These results indicate that pharmacological manipulation of cellular GSH content can down-regulate ras expression at the posttranscriptional level by destabilizing ras transcripts. The potential clinical implications are discussed.

Micronutrients and their influence on mutagenicity and malignant transformation

Many studies have now indicated that micronutrients, such as the carotenoids, tocopherols, and ascorbic acid, can prevent mutagenesis, genotoxic effects, or malignant transformation in bacteria and mammalian tissue, either in cell culture or in organ culture. In addition, multiple papers report that some of these micronutrients act as anticarcinogenic agents in animals treated with either ultraviolet light, ultraviolet light with chemicals, or chemical carcinogens alone. With respect to the carotenoids, early experiments used pharmacological doses of carotenoids, but more recent reports indicate that relatively small doses can be effective. Inasmuch as these effects are seen with both provitamin A and nonprovitamin A carotenoids, it would appear that these effects are intrinsic to the carotenoid molecule, and not due to the metabolic conversion to retinoids. Partially on the basis of these observations, it has been suggested that the micronutrients may function as chemopreventive agents for reducing the risk of cancer in humans. Numerous human intervention studies are underway to test this hypothesis.

Vitamin E and cancer prevention: recent advances and future potentials

Many animal and in vitro experiments have shown that the supplementation of diet with vitamin E within a certain dose range reduced the risk of chemical- and radiation-induced cancers. In vitro studies revealed that alpha-tocopheryl succinate (TS) induced differentiation and growth-inhibition in certain animal and human tumor cells in culture, whereas alpha-tocopherol (alpha-T), alpha-tocopheryl acetate (alpha-TA) and alpha-tocopheryl nicotinate (alpha-TN) were ineffective, alpha-TS also reduced basal and ligand-stimulated adenylate cyclase activity, and expression of c-myc and H-ras oncogenes in certain tumor cells in culture. The relative efficacy of various forms of vitamin E in cancer prevention in animal or human models has not been evaluated. Human epidemiologic studies utilizing retrospective and prospective case-control experimental designs are not suitable for evaluating the role of vitamin E in cancer prevention due to several inherent problems associated with these methodologies. Intervention trials utilizing vitamin E with appropriate biological and statistical rationales are most suitable for testing the role of vitamin E in cancer prevention in humans. Some human trials utilizing vitamin E alone or in combination with other nutrients are in progress.