1CancerChapter 4 SupplementCancer - important facts• Cancer is uncontrolled cell growth• It requires several steps to form• It is very different depending on which tissues are affected• It is a leading cause of death in the U.S. and other developed nations (Behind cardiovascular disease)Figure 3.30Cancer and Cell Division• Cancerdisrupts cellular controls on cell division• Remember Interphase (G1, S, G2) and Mitotic phase?Cancer and Cell Division• Normally, checkpoints keep cells from passing from one stage of the cell cycle to the next (e.g. S phase Æ G2)• Cancer causes cells to lose the ability to stop cell division at these checkpoints and so the cells divide continuously and beyond controlHow Mutations lead to cancer• Mutations disrupt normal controls over cell growth and division• Uncontrolled growth increases error rates• Thus cancers often begin where “stem cells” are dividing rapidly and are very rare in cells that do not divide.• Where would you expect more cancers to occur: in the heart or in the colon?Cancer Stages• Cancer develops in steps:– Abnormal cell – genetic mutations cause uncontrolled growth– Primary tumor – mass of cells develops, often in one area– Metastasis – cells from tumor enter blood stream– Secondary tumor(s) – these cells take up residence in other parts of the body, forming new tumors there2Development of Cancer -Metastasis• Invasion – abnormal cells grow into surrounding tissues• Penetration – cells enter the bloodstream• Escape – cells leave bloodstream to for secondary tumorCell Division and Tumors• Tumors (neoplasms):– enlarged mass of cells– abnormal cell growth and division1. Malignant tumor: – Spreads into surrounding tissues (invasion)– Can start new tumors (metastasis)2. Benign tumor: – Contained (no invasion)– not life threatening (but may become malignant)Cancer and Genes• Genes that when mutated tend to cause cancer come in two types• Oncogenes– Dominant (only one mutation needed to lose control of growth)• Tumor suppressor genes:– Recessive (need two mutated copies)– Examples: BRCA1, Rb1Cancer and Genes• The key to cancer: Whether the first mutation is inherited, like BRCA1, or spontaneous, cells need to accumulate more than one key mutation to become malignant. • However, each mutation makes the accumulation of further mutations more
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