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Except for heart and coronary disease, cancer is now the principal cause of death in the Western world. Despite extensive cancer research to find improved drugs and treatments, the average chance of being cured of cancer is augmented every year by only 0.5 percent. Cancer comprises a broad group of diseases characterized by uncontrolled and independent proliferative growth of tumor cells (Alberts et al., 1994). In cancer, malignant tumors invade surrounding tissue and give rise to formation of secondary tumors (metastases). The ability to metastasize is largely responsible for the lethality of malignant tumors. Surgery and radiotherapy are mostly used for treatment when a tumor is localized to a certain tissue. When metastasis has occurred, chemotherapy becomes an important weapon against cancer. |
