Apoptosis: a matter of life and death. Without death there would be no life. One has only to imagine our planet if nothing died -- teeming with endlessly multiplying numbers of people, animals, plants, and insects taking over every inch of space, consuming every bit of food, oxygen, and water, producing ever-expanding waste. Cancer is the equivalent scenario within our bodies. It arises when there is a glitch in the normal process, known as apoptosis, by which cells die.
CAS Biology Professor Ulla Hansen and her colleagues study the basic factors that control the life and death cycles of cells, focusing on the role played by a human protein known as LSF (late simian virus 40 factor). LSF is a transcription factor -- a protein that activates or represses the expression of a particular gene -- in this case a gene that produces an enzyme called thymidylate synthase. Thymidylate synthase, in turn, is necessary to produce thymidine triphosphate, an essential building block for DNA replication and cell division. Because of the central role of thymidylate synthase in growing cells, it has been used as a target in cancer therapy for many years.
Hansen is developing methodologies to inhibit the action of LSF so as to also inhibit the production of thymidylate synthase and cause the death of cancer cells by apoptosis. Because LSF responds to changes in the cellular environment, such as hormones, she and her colleagues believe that it may play a central role, integrating many signaling pathways and helping the cell decide when to grow, stop growth, or die.
Take ten minutes of sunshine. A critical protein involved in vitamin D metabolism has recently been isolated in human colon cells by Michael D. Holick, a MED professor of medicine. The protein, known as 25-hydroxyvitamin D-1_-hydroxylase (or one alpha-hydroxylase for short), prevents colon cells from proliferating and promotes them to differentiate -- that is, change from immature forms to more mature cells less capable of becoming cancerous. According to Holick, the protein may play a key role in the regulation of cell growth and in cancer protection.
One alpha-hydroxylase, previously believed to be located exclusively in the kidney, is responsible for changing vitamin D into an active form that can be used by cells throughout the body. The discovery of the one alpha-hydroxylase protein in colon cells may indicate the existence of a local mechanism that helps regulate cell growth.
Vitamin D is fat-soluble, like vitamins A and E. It has long been recognized as major factor in controlling the balance of calcium in the body. Unlike other vitamins, it is not generally found in food. Vitamin D is made in the skin by a complex process that uses the ultraviolet B (UVB) portion of sunlight -- 90 to 95 percent of all our vitamin D comes from casual, everyday exposure to sunlight.
Previous studies by Holick have determined that regular, brief exposure to UVB light not only increases levels of vitamin D, but also reduces blood pressure. To ensure an adequate supply of vitamin D, Holick recommends that people living in the latitude of Boston, particularly the elderly, who have diminished ability to make the vitamin, expose their hands, arms, and face to sunlight for 5 or 10 minutes a day two or three times a week. This will not significantly increase the risk of skin cancer, he says, and will provide an adequate source of vitamin D.
Holick's research was reported in the May 26 issue of the British medical journal Lancet.
Briefs" is written by Joan Schwartz in the Office of the Provost. To read
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