Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: The mechanisms by which polyamines accelerate tumor spread | Journal of Experimental Clinical Cancer Research Soda Journal of Experimental Clinical Cancer Research 2011 30 95 http content 30 1 95 REVIEW Open Access The mechanisms by which polyamines accelerate tumor spread Kuniyasu Soda Abstract Increased polyamine concentrations in the blood and urine of cancer patients reflect the enhanced levels of polyamine synthesis in cancer tissues arising from increased activity of enzymes responsible for polyamine synthesis. In addition to their de novo polyamine synthesis cells can take up polyamines from extracellular sources such as cancer tissues food and intestinal microbiota. Because polyamines are indispensable for cell growth increased polyamine availability enhances cell growth. However the malignant potential of cancer is determined by its capability to invade to surrounding tissues and metastasize to distant organs. The mechanisms by which increased polyamine levels enhance the malignant potential of cancer cells and decrease anti-tumor immunity are reviewed. Cancer cells with a greater capability to synthesize polyamines are associated with increased production of proteinases such as serine proteinase matrix metalloproteinases cathepsins and plasminogen activator which can degrade surrounding tissues. Although cancer tissues produce vascular growth factors their deregulated growth induces hypoxia which in turn enhances polyamine uptake by cancer cells to further augment cell migration and suppress CD44 expression. Increased polyamine uptake by immune cells also results in reduced cytokine production needed for anti-tumor activities and decreases expression of adhesion molecules involved in anti-tumor immunity such as CD11a and CD56. Immune cells in an environment with increased polyamine levels lose anti-tumor immune functions such as lymphokine activated killer activities. Recent investigations revealed that increased polyamine availability enhances the capability of cancer cells to invade and metastasize
