New Cases in 2000Deaths in 2000Table 1: People Living with AIDS (US, 2000)TotalUnit IV: Other Interesting TopicsIn this Unit, we will cover: I. CancerII. AIDSIII. Genetic EngineeringI. CancerWWW Reading: Cancer Statistics (20-year trends) One person in five in the developed world will die of some form of cancer. For 25 years, cancer research has been among the top priorities of the biomedical research community in the United States. We have learned much about this disease and, in the process, about the function of normal cells. Focused Reading: p 342-3 "Cancer Cells..." stop at “Some cancers…” Cancer is defined as the presence of a malignant tumor in the body. A neoplasm or tumor is a relentlessly growing mass of abnormal cells that are dividing in defiance of normal restraints on growth. However, most tumors are benign, that is, all of the cells of the tumor remain in the tumor mass and do not invade other tissues. Benign tumors are not cancerous, but they can be life-threatening if they occur in places in the body from which they cannot be removed without causing serious damage (e.g. some places in the brain. Such tumors are said to be "inoperable.") However, most benign tumors are not life threatening, and can be easily treated by surgical removal. A tumor becomes malignant or cancerous when its cells invade the other tissue(s). Invasivenessusually implies that the cells of the tumor can break loose, travel to a new site in the body through the blood or lymph, and establish secondary tumors. Such a tumor has metastasized. The process ofspreading is called metastasis and it is the hallmark of cancerous tumors. While benign and pre-metastatic cancerous tumors are relatively easy to cure by surgery or localized radiation or chemotherapy, metastasized tumors are very difficult to treat. Because cancer arises from a single cell that is growing out of control, in order to cure the metastasized cancer, every single cancerous cell in the body must be destroyed. This is virtually impossible in widely disseminated cancers. The type of cell that becomes cancerous defines the name of the cancer.Focused Reading: p 695 "Tissues…" stop at "Nervous tissue…"p 695 Fig 40.2152Animal tissues come in four varieties: 1) Epithelia lines the inside and outside surfaces of the body (e.g. skin, lungs, blood vessels, etc), and provides the bulk of functional cells in internal organs(e.g. endocrine glands, liver, pancreas, kidney). Cancers of epithelial cells are called carcinomas. 2) Connective tissue is a very broad category of tissue, which includes blood, bone, cartilage, fat, tendons, ligaments, and the strong protein fibers that hold all the organs together. Cancers of the connective tissue cells are called sarcomas. Cancer of the white blood cells (the leukocytes) is called leukemia. 3) Muscle forms the mass of the skeletal muscles, creates the walls of blood vesselsand internal organs (smooth muscle) and forms the wall of the heart (cardiac muscle). Cancers of muscle cells are also called sarcomas. 4) Nervous tissue forms the brain, spinal cord and nerves in the body. Cancers of the nervous system are called neuromas if they involve actual neurons, and gliomas if the involve the supporting cells of the nervous system. While these terms define broad categories of cancer, each type of cancer has its own distinguishing name. For instance, basal cell carcinoma is a kind of skin cancer caused by the cancerous growth of a basal cell in the skin (an epithelial cell). Melanoma is a different form of skin cancer caused by the cancerous growth of a melanocyte, the pigment producing cells of the skin. Both types of cancers are carcinomas, but they have very different characteristics, the former being very easily treated and almost never fatal while the latter is much more life threatening. Most cancers(85%) are carcinomas, and, in fact, an agent that causes any type of cancer is said to be a carcinogen or to be carcinogenic. Below you will find a list of some of the most prevalent cancers in the United States. Lung cancerhas the distinction of having the highest incidence of any single cancer at over 150,000 new cases per year and the highest death rate at 87%. (Actually, this method of calculating the death rate understates the threat of this disease. Over 90% of lung cancer victims will die within one year of diagnosis.) The other feature that distinguishes lung cancer is that, of all the cancers listed below it is by far the most preventable. The vast majority of lung cancer victims smoked cigarettes or lived with a heavy smoker. As in the case of AIDS, this sadly preventable disease continues to claim lives needlessly. Every year, lung cancer kills three times as many people as died in the Vietnam War. Cancer Statistics, USSite of CancerNew Casesin 2000Deaths in2000# MaleDeaths, 2000# FemaleDeaths, 2000Colon 93,800 47,700 23,100 24,600Lung and bronchus 164,100 156,900 89,300 67,600Pancreas 28,300 28,200 13,700 14,500Skin 56,900 9,600 6,000 3,600Breast 184,200 41,200 400 40,800Cervix 12,800 4,600 xxx 4,600Prostate 180,400 31,900 31,900 xxxBrain and othernervous system16,50013,000 7,100 5,900Lymphoma 62,300 27,500 14,400 13,100Leukemia 30,800 21,700 21,100 9,600153Adapted from: Greenlee, R.T., Murray, T., Bolden, S., Wingo, P.A. CA Cancer J Clin 2000;50:7-33To begin looking at what might cause cancer, here are a few things we know from simple observation:1) Cancers tend to run in families. However, very few cancers exhibit Mendelian inheritance ratios indicating that most are heavily influenced by non-genetic factors.2) Exposure to certain agents in the environment (certain chemicals and irradiation) is associated with the development of cancer. We call these agents carcinogens.3) If we perform the Ames test for mutagenicity, we find that all carcinogens are mutagens. (However, not all mutagens contribute to the development of cancer.)4) Malignant cancer cells have at least two things wrong with them: 1) They can't stop dividing; and 2) They leave their normal tissue beds and take up residence in areas of the body that are completely foreign to them. So, at a minimum, based on this information, we should be able to hypothesize that:1) Cancer is caused, or enhanced, by changes in the DNA which may be a. inherited mutations (since predisposition for cancer runs in families); and/orb. new mutations (since carcinogens cause mutations in the DNA)2) Cancerous cells have