Cancer Chapter 4 Supplement

Cancer - 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 3.30 Cancer and Cell Division Cancer disrupts cellular controls on cell division Remember Interphase (G 1, S, G 2 ) 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  G2) Cancer causes cells to lose the ability to stop cell division at these checkpoints and so the cells divide continuously and beyond control

How 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 there

Development of Cancer - Metastasis Invasion – abnormal cells grow into surrounding tissues Penetration – cells enter the bloodstream Escape – cells leave bloodstream to for secondary tumor

Cell Division and Tumors Tumors (neoplasms): –enlarged mass of cells –abnormal cell growth and division 1. 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, Rb1

Cancer 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 likely.