Gary Gabriels

Combination of tunicamycin with anticancer drugs synergistically enhances their toxicity in multidrug-resistant human ovarian cystadenocarcinoma cells

BackgroundThe pharmacologic modulatory effects of the antibiotic, tunicamycin (TM), on multidrug-resistant human UWOV2 ovarian cancer cells are reported. The UWOV2 cell line was derived from a cystadenocarcinoma in a patient refractory to combination chemotherapy with actinomycin D, vincristine (VCR), cis-diaminedichloroplatinum (II) (CDDP) and doxorubicin (DXR). In an attempt to explain drug resistance in this cell line, we examined the effects of TM on their sensitivity to various anticancer drugs, the uptake, efflux and retention of [3H]VCR, and their ability to bind [14C]DXR and [3H]azidopine (AZD), a photoaffinity label of the multidrug transporter, P-glycoprotein (Pgp).ResultsTM effectively decreased the EC50 for DXR, EXR, VCR and CDDP, thus enhancing their cytotoxicity. The antibiotic also prolonged the intracellular retention time of [3H]VCR and increased the binding of both [14C]DXR and [3H]AZD to the cells.ConclusionIt is concluded that the pharmacomodulatory effects of TM in these cells are mediated by global inhibition of protein and glycoprotein synthesis and synergistic interaction with antineoplastic drugs. The ability of TM to enhance the sensitivity of drug resistant tumour cells may have impact on the design and optimization of novel resistance modifiers to improve the efficacy of combination treatment of intractable neoplasms.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part I: targeting p53, Mdm2, GADD153/CHOP, GRP78/BiP and heat shock proteins

Background: In eukaryotes, endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are coordinately regulated to maintain steady-state levels and activities of various cellular proteins to ensure cell survival. Objective: This review (Part I of II) focuses on specific ERS and UPR signalling regulators, their expression in the cancer phenotype and apoptosis, and proposes how their implication in these processes can be rationalised into proteasome inhibition, apoptosis induction and the development of more efficacious targeted molecular cancer therapies. Method: In this review, we contextualise many ERS and UPR client proteins that are deregulated or mutated in cancers and show links between ERS and the UPR, their implication in oncogenic transformation, tumour progression and escape from immune surveillance, apoptosis inhibition, angiogenesis, metastasis, acquired drug resistance and poor cancer prognosis. Conclusion: Evasion of programmed cell death or apoptosis is a hallmark of cancer that enables tumour cells to proliferate uncontrollably. Successful eradication of cancer cells through targeting ERS- and UPR-associated proteins to induce apoptosis is currently being pursued as a central tenet of anticancer drug discovery.

Nutritional supplement products: does the label information influence purchasing decisions for the physically active?

BackgroundThe increase in sales of nutritional supplement globally can be attributed, in part, to aggressive marketing by manufacturers, rather than because the nutritional supplements have become more effective. Furthermore, the accuracy of the labelling often goes unchallenged. Therefore, any effects of the supplement, may be due to contaminants or adulterants in these products not reflected on the label.MethodsA self-administered questionnaire was used to determine how consumers of nutritional supplements acquired information to assist their decision-making processes, when purchasing a product. The study was approved by the University of Cape Town, Faculty of Health Sciences Human Research Ethics Committee. The questionnaire consisted of seven, closed and open-ended questions. The participants were asked to respond to the questions according to a defined list of statements. A total of 259 participants completed and returned questionnaires. The data and processing of the returned questionnaires was captured using Windows-based Microsoft® Office Excel 2003 SP 1 (Excel

Tunicamycin potentiates drug cytotoxicity and vincristine retention in multidrug resistant cell lines.

Tunicamycin (TM), an inhibitor of glycoprotein processing, was investigated for its potential to reverse the multiple drug resistance (MDR) phenotype. When TM was added in vitro to drug-resistant NIH-3T3-MDR and KB-8-5-11 cells, they developed an increased sensitivity to doxorubicin, epirubicin, vincristine and colchicine. Similarly, the sensitivity of NIH-3T3-MDR cells to cisplatin was also enhanced by TM. In the presence of TM, drug-sensitive NIH-3T3-parental cells exhibited greater susceptibility to the toxic effects of doxorubicin, epirubicin, vincristine (marginally significant), and colchicine, but not to cisplatin. Tunicamycin-treated drug-sensitive KB-3-1 cells showed an increased response to vincristine, but not to the other anticancer drugs. Pretreatment with TM inhibited glycoprotein synthesis in all the cell lines. Neither prior exposure to, nor co-incubation with TM, influenced the uptake of vincristine (VCR) in the various cell lines. However, NIH-3T3-MDR cells accumulated less VCR than their drug-sensitive controls and also exhibited reduced efflux of the drug when treated with TM. There were no significant differences in the levels of intracellular VCR uptake between drug-sensitive KB-3-1 and KB-8-5-11 cells. Tunicamycin increased intracellular VCR retention in KB-8-5-11 and NIH-3T3-MDR cells, but not in NIH-3T3-parental cells. However, drug-sensitive KB-3-1 cells expressed reduced VCR retention in response to TM exposure, indicating that correlations between VCR toxicity and its retention in the presence of TM should be made with caution. The results suggest that the enhancement of intracellular VCR retention in MDR cells lines caused by TM is likely to be the result of inhibition of VCR efflux. Inhibition of glycoprotein synthesis during TM exposure may account for the changes in VCR efflux and retention observed in the MDR cell lines. The enhancement of cisplatin cytotoxicity in NIH-3T3-MDR cells after exposure to TM is an interesting observation, since it is generally believed that agents which modify the MDR phenotype do not show a sensitising effect to cisplatin. These findings may have applications in the reversal of drug resistance.

Melamine contamination in nutritional supplements - Is it an alarm bell for the general consumer, athletes, and 'Weekend Warriors'?

BackgroundNutritional supplements are used or experimented with by consumers, notably these are; competitive and recreational athletes of all ages, and ‘weekend warriors’. As a consequence the supplement industry has grown to meet the increasing demand. A Global Industry Analysts Inc. report indicates that the herbal supplement market has not declined during the worldwide recession, but in fact exhibited steady growth over the period 2008 to 2009. It is anticipated that the market will reach US

Will the new Consumer Protection Act prevent harm to nutritional supplement users

93.15 billion by the year 2015. These supplements may contain adulterated substances that may potentially have harmful short - and long-term health consequences to the consumer. “Scrap Melamine” is such an example, which has been implicated in the kidney failure and death of several cats, dogs and pigs. In China in 2008, reports described very severe health effects in infants and young children. At the time over 294 000 infants were screened and diagnosed with urinary tract stones and sand-like calculi associated with melamine in milk products, of which 50 000 infants were hospitalised, and at least six associated deaths, recorded. The extent that melamine contamination occurs in nutritional supplements is not known. Therefore, the aim of this study was to determine whether commercially available nutritional and traditional supplement products contain melamine, even though they are not declared by the manufacturer on the product label.MethodsA total of 138 nutritional supplements products were obtained from (i) direct purchases from shops, pharmacies and outlets, (ii) directly from consumers, and (iii) from suppliers, manufacturers and distributors. The products were laboratory analysed for melamine, using Tandem Liquid Chromatography Mass Spectrometry.ResultsForty-seven % of all the products (n = 138) tested positive for melamine. Eight-two % of the South African produced products (n = 27) tested positive and 58 % of the products imported into South Africa (n = 50) tested positive. The median concentration estimate for melamine in the products tested were, 6.0 μg/g for the 138 supplements tested, 8.9 μg/g for South African produced products, and 6.9 μg/g for products imported into South Africa.ConclusionThe melamine (undeclared on product label) levels detected in the nutritional supplements products investigated were within the Tolerable Daily intake (TDI) limit guidelines of 200 μg/g as set by WHO and others. Melamine over exposure within the context of the nutritional supplements consumption in the products investigated should not be of concern to the consumer provided the recommended guidelines of daily product use are adhered to. Further investigation is warranted to determine, (i) the link of melamine as (part) substitute for the perceived total declared protein content on the product label, (ii) cyanuric and uric acid presence in the supplement products that could form chemical-complex formation with melamine and/or analogues that could cause adverse health effects.

Information on nutritional supplement labels: Time for legislation

BACKGROUND. There is no clear distinction between the regulation of food, supplements and medicines in South Africa. Consequently, grey areas exist in implementing the legislation, particularly in the supplement industry. The increase in supplement sales in South Africa can be attributed to aggressive marketing by manufacturers whose claims are not always supported by published peer-reviewed evidence. Such claims often go unchecked, resulting in consumers being mislead about the role of supplements. As a result of poor regulation, contaminants or adulterants in supplements may also cause insidious effects unrelated to the listed ingredients. AIM. To assess the regulations, legislation, and claims associated with nutritional supplement products in South Africa. METHOD. Peer-reviewed literature and the relevant South African statutes were consulted. RESULTS. The National Health Act incorporates the Medicine Control Council, which is charged with ensuring the safety, quality and effectiveness of medicines, and related matters, including complementary/alternative medicines. The South African Institute for Drug-Free Sport and Amendment Act provides for testing athletes for using banned substances, but currently does not concern itself with monitoring nutritional supplements for contaminants or adulterants that may cause a positive drug test, which has implications for sports participants and also the health of the general population. The implementation of the Consumer Protection Act 68 of 2008 (CPA) could protect consumer rights if it is administered and resourced appropriately. CONCLUSION. The CPA should promote greater levels of policy development, regulatory enforcement, and consumer education of South Africas supplement industry.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part II: targeting cell cycle events, caspases, NF-κB and the proteasome.

Abstract Background: Nutritional supplements have received attention both from food manufacturers, as a means of marketing the added value to health; and from consumers, in terms of awareness, education, and improved health. To assist this process, it is important to have specific knowledge and understanding of the claims made on labels of nutritional supplement products used for general, and more specifically, for sports consumers. The industry is not regulated, and therefore the claims that are made may not always be accurate. Method: The aim was to describe the labelling and claims information on the labels of a select group of nutritional supplements, either manufactured in, or imported into South Africa. Specific predetermined categories of labelling and claims made on the containers were assessed and summarised. Results: Forty products were selected for analysis, of which 21 (53%) were locally assembled or manufactured products, and 19 (48%), international imported products. Ninety-five per cent of products contained a warning statement on the label. Eighty-five per cent of the nutritional supplement products had a disclaimer on the label. Ninety-eight per cent of the nutritional supplement product labels included some claim on the label. Conclusion: The following information, in particular, needs to be regulated and enforced as part of the labelling process, to ensure that the consumer can make an informed choice. This includes highlighting the potential for adverse events, encouraging warning statements pertaining to “exclusion of use, and “not a cure for disease states”, and alerting consumers of the potential for the presence of banned substances, based on laboratory screen methods.

Pseudoephedrine is without ergogenic effects during prolonged exercise

Background: Endoplasmic reticulum stress (ERS), the unfolded protein response (UPR) and apoptosis signal transduction pathways are fundamental to normal cellular homeostasis and survival, but are exploited by cancer cells to promote the cancer phenotype. Objective: Collateral activation of ERS and UPR role players impact on cell growth, cell cycle arrest or apoptosis, genomic stability, tumour initiation and progression, tumour aggressiveness and drug resistance. An understanding of these processes affords promising prospects for specific cancer drug targeting of the ERS, UPR and apoptotic pathways. Method: This review (Part II of II) brings forward the latest developments relevant to the molecular connections among cell cycle regulators, caspases, NF-κB, and the proteasome with ERS and UPR signalling cascades, their functions in apoptosis induction, apoptosis resistance and oncogenesis, and how these relationships can be exploited for targeted cancer therapy. Conclusion: Overall, ERS, the UPR and apoptosis signalling cascades (the molecular therapeutic targets) and the development of drugs that attack these targets signify a success story in cancer drug discovery, but a more reductionist approach is necessary to determine the precise molecular switches that turn on antiapoptotic and pro-apoptotic programmes.