Cancer: Uncontrolled Cell Division - PDF

Cancer: Uncontrolled Cell Division and Differentiation Cancer Disease of multicellular organisms Cancer is a disease of the cell cycle Cancer cells do not respond normally to the cell cycle control Over 1 million Americans are diagnosed with cancer each year In about 10% of cancers, a high...

Cancer: Uncontrolled Cell Division and Differentiation Cancer Disease of multicellular organisms Cancer is a disease of the cell cycle Cancer cells do not respond normally to the cell cycle control Over 1 million Americans are diagnosed with cancer each year In about 10% of cancers, a higher predisposition to develop the disease is an inherited trait Most cancers, about 90%, do not involve genetic changes that are passed from parent to offspring What causes cancer? Carcinogens Life style Smoking can cause cancers of the lungs, mouth, throat, bladder, kidneys as well as heart disease and stroke. Drinking a lot of alcohol increases a person’s risk of getting cancer of the mouth, throat, and some other organs. 50-70% of cancer deaths in U.S. caused by human behaviors such as smoking, physical inactivity and poor dietary choices. 30% from smoking only Radiation (X-rays) can cause cancerWhat causes cancer? Carcinogens Life style Smoking can cause cancers of the lungs, mouth, throat, bladder, kidneys as well as heart disease and stroke. Drinking a lot of alcohol increases a person’s risk of getting cancer of the mouth, throat, and some other organs. 50-70% of cancer deaths in U.S. caused by human behaviors such as smoking, physical inactivity and poor dietary choices. 30% from smoking only Radiation (X-rays) can cause cancer Carcinogens About 90% of all human cancers are related to exposure to carcinogens Most carcinogens, such as UV light and certain chemicals in cigarette smoke promote genetic changes in somatic cells DNA alterations can lead to effects on gene expression that ultimately affect cell division, and thereby lead to cancer DNA Mutations and Mechanisms of Repair Mutations: most frequent during DNA replication: – Causes: mistake in DNA replication, chemical and physical forces – Effects: none (neutral), nudge in evolution (beneficial), cell death or cancer (harmful) Mechanisms of repair: DNA repair enzyme. Cancer Cells: Growing Out of Control Normal plant and animal cells have a cell cycle control system. How Cancer Develops Mutated or damaged genes – Proto-oncogenes: normal regulatory genes – Oncogenes: mutated or damaged proto-oncogenes – Tumor suppressor genes: regulatory genes repress cell growth, division, differentiation, adhesion: * May be turned off, damaged, or mutated in cancers Cancer Stages Stage 0: in situ tumor. Cells in the tumor are abnormal, but they are only found in the tumor Stage I–III: Defined for each type of cancer, based on size, degree of spread, lymph node involvement Stage IV: Cancer has metastasized to distant sites and organs © 2017 Pearson Education, Inc. Cancer Development Two things must happen simultaneously for cancer to develop: 1. Cell must divide uncontrollably 2. Cell must undergo physical changes and break away from surrounding cells These changes usually correlate with specific mutations in the cell’s genes © 2017 Pearson Education, Inc. Characteristics of Benign Tumors and Cancers Tumors Benign: – Remain in one location – Single, well-defined mass – May be surrounded by connective tissue Cancerous: – Abnormal cell structure, may appear undifferentiated – May spread – Edge of tumor not clearly defined Benign Tumor Development Malignant Tumor Development Factors Contributing to Cancer Viruses and bacteria (> 15% of all cancers) Chemicals in the environment (e.g., asbestos) Radiation (sun - UV B- and radioactive materials) Dietary factors (red meat and saturated animal fat) Alcohol use Tobacco Carcinogens Ten Most Common Cancers Lung cancer Diagnosed in approximately 170,000 men and women each year in the U.S. Worldwide, more than 1.2 million cases are diagnosed Nearly 90% of these cases are caused by smoking Lung Cancer: Smoking Is Leading Risk Factor No simple screening test, so the cancer is often more advanced when detected Early symptoms are nonspecific – Persistent coughing – Recurrent pneumonia or bronchitis – Voice change Later symptoms – Chest pain – Blood in sputum Treatment – Surgery, often combined with radiation and chemotherapy © 2017 Pearson Education, Inc. Colon and Rectal Cancers: Tests Can Detect Them Early Symptoms – Blood in stool, rectal bleeding Risk factors – Sedentary lifestyle, obesity, smoking, family history, low-fiber diet, high-fat diet Start as polyps (benign tumors), which gradually become malignant Screening tests can detect cancer early – Detection of blood in stool specimens – Colonoscopy: examining interior of colon with flexible fiber-optic scope Treatment: polyp removal, tumor removal © 2017 Pearson Education, Inc.Colon and Rectal Cancers: Tests Can Detect Them Early Symptoms – Blood in stool, rectal bleeding Risk factors – Sedentary lifestyle, obesity, smoking, family history, low-fiber diet, high-fat diet Start as polyps (benign tumors), which gradually become malignant Screening tests can detect cancer early – Detection of blood in stool specimens – Colonoscopy: examining interior of colon with flexible fiber-optic scope Treatment: polyp removal, tumor removal © 2017 Pearson Education, Inc. Figure 18.11 Polyp Intestinal folds Colonoscope © 2017 Pearson Education, Inc. Breast Cancer: Early Detection Pays Off Early detection is crucial for survival – Mammogram: low dose X-ray used for early detection – Detection of a lump on breast exam Risk factors – Genetics: two different genes increase risk BRCA1 and BRCA2 – Age – Early onset of menstruation, late menopause – Obesity after menopause – Oral contraceptives – Hormone replacement after menopause Pancreatic Cancer: Rarely Detected Early Enough No obvious early signs Second highest death rate of all cancers, largely due to late detection Risk factors: smoking, genetics (BRCA1 or BRCA2) © 2017 Pearson Education, Inc. Prostate Cancer: Most Common After Age 50 Biggest risk factor: advancing age Symptoms – Urination difficulties, blood in urine, pain in pelvic area Diagnosis – Digital rectal exam – Blood test for PSA (prostate-specific antigen) – Biopsy Treatment – Surgery, radiation therapy, hormones © 2017 Pearson Education, Inc. Leukemia: Chemotherapy Is Often Effective Cancer of immature white blood cells in the bone marrow Risk factors: Down syndrome, exposure to ionizing radiation, benzene, infection with HTLV-1 virus  Childhood as well as adult forms of leukemia Symptoms: nonspecific Diagnosis: blood tests and bone marrow biopsies Treatment: chemotherapy, or chemotherapy plus bone marrow transplant © 2017 Pearson Education, Inc. Lymphoma: Cancers of Lymphoid Tissue Includes Hodgkin’s and non-Hodgkin’s lymphoma Symptoms – Enlarged lymph nodes, intermittent fever, itching, weight loss, night sweats Risk factors – Altered immune function Transplant recipients HIV infection Occupational exposure to herbicides Treatment: radiation, chemotherapy © 2017 Pearson Education, Inc. Esophageal Cancer: High Ratio of Deaths to Cases Ninety-two deaths for every 100 new cases Risk factors – Age, alcohol and/or tobacco use, obesity, chronic gastric reflux Rarely diagnosed at an early stage By the time symptoms appear, generally 60% of the circumference of the esophagus is cancerous Treatment © 2017 Pearson Education, Inc.Esophageal Cancer: High Ratio of Deaths to Cases Ninety-two deaths for every 100 new cases Risk factors – Age, alcohol and/or tobacco use, obesity, chronic gastric reflux Rarely diagnosed at an early stage By the time symptoms appear, generally 60% of the circumference of the esophagus is cancerous Treatment © 2017 Pearson Education, Inc. Other Cancers Urine bladder Cancer of the Uterus Kidney Cancer Skin Cancer Ovarian Cancer and Testicular Cancer © 2017 Pearson Education, Inc. The Immune System Plays an Important Role in Cancer Prevention Immune system normally defends the body against cancers Cancer cells may not be recognized as “self” and may be destroyed by the immune system Anything that suppresses the immune system may make an individual more susceptible to cancer © 2017 Pearson Education, Inc. Advances in Diagnosis: Early Detection Tumor imaging: X-rays, MRI. Genetic testing: identify mutated genes; issues. Enzyme tests for cancer markers: screening large numbers of people. X-ray of breast cancer MRI of brain cancer Cancer Treatments Conventional treatments: surgery, radiation, and chemotherapy. - Radiation therapy, which damages DNA and disrupts cell division. - Chemotherapy, which uses drugs that disrupt cell division. Immunotherapy: promotes the immune response Starving cancers: inhibits angiogenesis (growth of new blood vessels) Molecular treatments: target oncogenes Most Cancers Are Preventable Know family history Get regular medical screenings Learn self-examination techniques Avoid direct sunlight 10 a.m. to 4 p.m., avoid sunlamps and tanning salons.  Watch diet and weight Do not smoke Drink in moderation, if at all Be informed Exercise regularly