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Zinc supplements linked to prostate cancer
Newsdesk
Use of zinc supplements may increase the risk of prostate cancer, according to researchers at the National Institutes of Health, MD, USA (J Natl Cancer Inst 2003; 95: 1004–07); a finding which may have important implications for children in the developing world. In a study of 46 974 men, aged 40–75 years, researchers found that men who had consumed more than 100 mg/day of zinc had an increased risk of advanced prostate cancer (relative risk 2·29). Furthermore, those who took zinc supplements for more than 10 years had a relative risk of 2·37. Doses below 100 mg/day were not associated with increased cancer risk. “Zinc oversupply may potentially affect prostate cancer risk via systemic metabolic pathways”, comments leadauthor Michael Leitzmann. “For example, intake of excessive amounts of zinc impairs the immune system and may also interfere with cancer-protecting activity of selenium.” However, he cautions that the exact mechanisms are unclear and require further research. Zinc supplementation has been proved to be beneficial for children in developing countries and a recent study in the Lancet (2003; 362: 65–71) found that zinc reduces diarrhoea, pneumonia, and possibly malaria and could prevent about 5% of childhood deaths. There are three large trials of between 30 000 and 90 000 children currently underway in India, Nepal, and Tanzania examining the effect of zinc on child mortality.
Rights were not granted to include this image in electronic media. Please refer to the printed journal.
© Will & Deni McIntyre/Science Photo Library
Zinc supplements linked to prostate cancer
Zinc supplements are avaiable in tablet form.
Wafaie Fawzi from Harvard School of Public Health, Boston, MA, USA agrees that it is important to carefully assess the overall effect of zinc in people in developing countries. However, when asked about the Leitzmann study, he points out that “100 mg per day is a high dose and the trials in developing countries have tended to use 20 mg per day or 70 mg per week”. Leitzmann adds: “There is no evidence that zinc supplementation in children leads to prostate cancer in later life.” Cathel Kerr
Molecular imaging boosts effectiveness of gene therapy Molecular imaging can greatly improve the effectiveness of gene therapy and help assess the results of treatment because it enables clinicians to observe cell function, according to Jonathan Kruskal (Harvard Medical School, MA, USA). “Gene therapy has hit major stumbling blocks recently because of the ways in which genes are delivered”, Kruskal explains. “By using non-viral vectors such as liposomes and polymers, and molecular imaging to guide injections or catheter release, radiologists can help ensure safe, targeted delivery and, ultimately, monitor gene uptake and expression.” Currently, after genes are delivered to a tumour, the only indication of efficacy is whether the tumour shrinks. But although the tumour may not go away, says Kruskal, the therapy may still be working, for instance “it may start by putting the tumour to sleep”. THE LANCET Oncology Vol 4 August 2003
With molecular imaging and specific contrast agents, he notes, “we can actually see activated scavenger cells from outside the liver migrating into tumour cells. And, in animals, we’re using green fluorescent protein to show delivery—ie, the delivered genes glow red.” Other strategies are in various phases of development. Molecular imaging will soon be used to guide catheters coated with leukotrienes into tumours; the leukotrienes increase the permeability of the vessels around the tumour, enabling new genes to “leak” into the tumour more effectively. Suicide gene therapy is also being studied. With this technique, Kruskal explains, patients are given an inactive drug, and genes which express enzymes that activate the drug are injected into the tumour; when the drug passes through the tumour, the enzymes break it down, activating the toxin and releasing it locally.
Furthermore, conventional imaging methods are being used in new ways, he adds. Focused ultrasound, for example, is being used to shatter liposomes, causing them to release their genetic payload in a specific region. Ultrasound also improves the absorption of genes, and incorporation of DNA into tumour cells. These advances “are resulting in gene therapy being used with increasing frequency in the clinical setting”, Kruskal observes. However, there is a major obstacle to overcome. “We have to be able to take functional imaging of individual cells, which we’re doing now with molecular imaging, into whole body imaging, using positron emission tomography, for example. Then we will be able to image gene delivery in actual patients, and monitor its effectiveness”, he concludes. Marilynn Larkin
http://oncology.thelancet.com
For personal use. Only reproduce with permission from The Lancet.
455
Use of zinc supplements may increase the risk of prostate cancer, according to researchers at the National Institutes of Health, MD, USA (J Natl Cancer Inst 2003; 95: 1004–07); a finding which may have important implications for children in the developing world. In a study of 46 974 men, aged 40–75 years, researchers found that men who had consumed more than 100 mg/day of zinc had an increased risk of advanced prostate cancer (relative risk 2·29). Furthermore, those who took zinc supplements for more than 10 years had a relative risk of 2·37. Doses below 100 mg/day were not associated with increased cancer risk. “Zinc oversupply may potentially affect prostate cancer risk via systemic metabolic pathways”, comments leadauthor Michael Leitzmann. “For example, intake of excessive amounts of zinc impairs the immune system and may also interfere with cancer-protecting activity of selenium.” However, he cautions that the exact mechanisms are unclear and require further research. Zinc supplementation has been proved to be beneficial for children in developing countries and a recent study in the Lancet (2003; 362: 65–71) found that zinc reduces diarrhoea, pneumonia, and possibly malaria and could prevent about 5% of childhood deaths. There are three large trials of between 30 000 and 90 000 children currently underway in India, Nepal, and Tanzania examining the effect of zinc on child mortality.
Rights were not granted to include this image in electronic media. Please refer to the printed journal.
© Will & Deni McIntyre/Science Photo Library
Zinc supplements linked to prostate cancer
Zinc supplements are avaiable in tablet form.
Wafaie Fawzi from Harvard School of Public Health, Boston, MA, USA agrees that it is important to carefully assess the overall effect of zinc in people in developing countries. However, when asked about the Leitzmann study, he points out that “100 mg per day is a high dose and the trials in developing countries have tended to use 20 mg per day or 70 mg per week”. Leitzmann adds: “There is no evidence that zinc supplementation in children leads to prostate cancer in later life.” Cathel Kerr
Molecular imaging boosts effectiveness of gene therapy Molecular imaging can greatly improve the effectiveness of gene therapy and help assess the results of treatment because it enables clinicians to observe cell function, according to Jonathan Kruskal (Harvard Medical School, MA, USA). “Gene therapy has hit major stumbling blocks recently because of the ways in which genes are delivered”, Kruskal explains. “By using non-viral vectors such as liposomes and polymers, and molecular imaging to guide injections or catheter release, radiologists can help ensure safe, targeted delivery and, ultimately, monitor gene uptake and expression.” Currently, after genes are delivered to a tumour, the only indication of efficacy is whether the tumour shrinks. But although the tumour may not go away, says Kruskal, the therapy may still be working, for instance “it may start by putting the tumour to sleep”. THE LANCET Oncology Vol 4 August 2003
With molecular imaging and specific contrast agents, he notes, “we can actually see activated scavenger cells from outside the liver migrating into tumour cells. And, in animals, we’re using green fluorescent protein to show delivery—ie, the delivered genes glow red.” Other strategies are in various phases of development. Molecular imaging will soon be used to guide catheters coated with leukotrienes into tumours; the leukotrienes increase the permeability of the vessels around the tumour, enabling new genes to “leak” into the tumour more effectively. Suicide gene therapy is also being studied. With this technique, Kruskal explains, patients are given an inactive drug, and genes which express enzymes that activate the drug are injected into the tumour; when the drug passes through the tumour, the enzymes break it down, activating the toxin and releasing it locally.
Furthermore, conventional imaging methods are being used in new ways, he adds. Focused ultrasound, for example, is being used to shatter liposomes, causing them to release their genetic payload in a specific region. Ultrasound also improves the absorption of genes, and incorporation of DNA into tumour cells. These advances “are resulting in gene therapy being used with increasing frequency in the clinical setting”, Kruskal observes. However, there is a major obstacle to overcome. “We have to be able to take functional imaging of individual cells, which we’re doing now with molecular imaging, into whole body imaging, using positron emission tomography, for example. Then we will be able to image gene delivery in actual patients, and monitor its effectiveness”, he concludes. Marilynn Larkin
http://oncology.thelancet.com
For personal use. Only reproduce with permission from The Lancet.
455