Cell division studies hint at future cancer therapyJanuary 23, 2008When a cell's assets get divided between daughter cells, Dr. Quansheng Du wants to make sure both offspring do well. He's dissecting the complex, continuous and amazing process that enables one cell to become two. When all goes well, cell division, or mitosis, helps repopulate a damaged organ or replenish endogenous stem cells. When it goes badly, it can result in cancer or developmental defects. "What we are trying to understand is how cells divide," says Dr. Du, cell biologist at the Medical College of Georgia, who recently received $2 million in grants from the National Institutes of Health and the American Cancer Society to pursue his studies. He focuses on the mitotic spindle, a sort of demarcation line that helps a dividing cell divvy up its genetic information. Once a cell decides to divide, it duplicates its genetic material and the nuclear envelope containing the material dissolves. Microtubules, stick-like projections that look like spokes on a wheel, start moving, reorganizing into a spindle-shaped structure that attaches and aligns the genetic material at the center of the spindle. The cell, sensing the microtubule attachment, initiates a process that pulls the duplicated genetic material apart. The outcome of normal cell division is typically two cells that look just like the original. In a culture dish and in humans, the process takes about an hour. Not every cell can divide. Terminally differentiated cells, such as neurons and muscle cells, can't. However, stem cells, known for their flexibility, divide well and at least three ways. They can divide genetic material evenly, forming two identical stem cells. They can undergo asymmetric cell division, birthing one identical stem cell as well as a new daughter cell that differentiates into another cell type, such as a skin cell or neuron. They can even make two uniquely differentiated cells, thus depleting the stem cell. During mammalian development and tissue maintenance, stem cells are constantly balancing between self-renewal and differentiation by adapting different types of cell division. While a postdoctoral fellow at the University of Virginia, Dr. Du was studying cell polarity, essential to asymmetric cell division because it attracts so-called cell fate determinants to one side of the mother cell and directs spindle orientation. In work published in Nature Cell Biology, Current Biology and Cell, he detailed a group of proteins critical for spindle organization and positioning in mammalian cells. These proteins may help determine cell fate after asymmetric cell division as well, he says: for example, determining whether the daughter cells keep being stem cells or differentiate into another cell type. Now, he wants to know how these proteins get where they need to be and how they cooperate with other proteins to organize the spindle and direct its orientation. These details may eventually lead to better cancer treatment, such as disrupting mitotic spindle organization so cancer cells cannot divide, Dr. Du says. The relatively recent discoveries of cancer stem cells make the possibilities even more intriguing. "The current cancer stem cell theory is that it's actually just a small population of cells within the tumor that are the original cancer-initiating cells," says Dr. Du. Still if each cancer stem cell in that small population divides, the numbers add up quickly. "How normal stem cells become cancer stem cells is not clear," he says. "Abnormal asymmetric stem cell division, which will break the balance between stem cell self-renewal and differentiation, may be an early event that drives the development of cancer stem cells." Understanding the mechanisms of stem cell division will provide clues for targeted cancer therapy against these cancer stem cells. Manipulating the balance toward differentiation, for example, would probably lead to the depletion of cancer stem cells, Dr. Du says. Medical College of Georgia |
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| Related Stem Cells Current Events and Stem Cells News Articles Gene mismatch influences success of bone marrow transplants A commonly inherited gene deletion can increase the likelihood of immune complications following bone marrow transplantation, an international team of researchers reports in the November 22 advance online issue of Nature Genetics. New research shows versatility of amniotic fluid stem cells For the first time, scientists have demonstrated that stem cells found in amniotic fluid meet an important test of potential to become specialized cell types, which suggests they may be useful for treating a wider array of diseases and conditions than scientists originally thought. First reconstitution of an epidermis from human embryonic stem cells Stem cell research is making great strides. This is yet again illustrated by a study carried out by the I-STEM* Institute (I-STEM/ Inserm UEVE U861/AFM), published in the Lancet on 21 November 2009. The I-STEM team, directed by Marc Peschanski has just succeeded in recreating a whole epidermis from human embryonic stem cells. Bone Implant Offers Hope for Skull Deformities A synthetic bone matrix offers hope for babies born with craniosynostosis, a condition that causes the plates in the skull to fuse too soon. Your Own Stem Cells Can Treat Heart Disease The largest national stem cell study for heart disease showed the first evidence that transplanting a potent form of adult stem cells into the heart muscle of subjects with severe angina results in less pain and an improved ability to walk. The transplant subjects also experienced fewer deaths than those who didn't receive stem cells. Is hepatic differentiation of embryonic stem cells induced by valproic acid and cytokines? Embryonic stem (ES) cells, known for their capacity to proliferate indefinitely and differentiate into almost all types of cells including hepatocytes, have raised the hope of cellular replacement therapy for liver failure. Paradoxical protein might prevent cancer One difficulty with fighting cancer cells is that they are similar in many respects to the body's stem cells. By focusing on the differences, researchers at Karolinska Institutet have found a new way of tackling colon cancer. The study is presented in the prestigious journal Cell. U of M researchers find 2 units of umbilical cord blood reduce risk of leukemia recurrence A new study from the Masonic Cancer Center, University of Minnesota shows that patients who have acute leukemia and are transplanted with two units of umbilical cord blood (UCB) have significantly reduced risk of the disease returning. The use of stem cells in regenerative medicine may also be detrimental for health The use of stem cells in regenerative medicine is not always beneficial for human health, it may even be harmful according to a work done by the University of Granada and University of León. Scientists have demonstrated that transplantation of human mononuclear cells isolated from umbilical cord blood exerted a deleterious effect in rats with liver cirrhosis. Penn Study Provides First Clear Idea of How Rare Bone Disease Progresses An international team of scientists, led by researchers at the University of Pennsylvania School of Medicine, is taking the first step in developing a treatment for a rare genetic disorder called fibrodysplasia ossificans progressiva (FOP), in which the body's skeletal muscles and soft connective tissue turns to bone, immobilizing patients over a lifetime with a second skeleton. More Stem Cells Current Events and Stem Cells News Articles |
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