Prof. Arnaldo Ferreira

Impacts, Issues: Between You and
Eternity
 Cancer strikes one in three people in the United
States
• Kills one in four
 Overall more males than females get cancer
• Pattern varies depending upon the type of cancer
 Gene mutations and cancer
• BRCA1 and BRCA2: “breast cancer susceptibility genes”

The Characteristics of Cancer
 As genes switch on and off, they determine when and how fast the cell will grow and divide, when it will stop dividing, and even when it will die
 Cancer can result when controls over cell division are lost

Some Tumors Are Cancer, Others Are Not
Hyperplasmia
 Cells in a tissue overgrow
 Resulting defined mass: tumor (neoplasm)
• Benign , e.g., moles
• Slow growth
• Expands in the same tissue; does not spread
• Cells look nearly normal
• Malignant
• Rapid growth
• Invades surrounding tissue and metastasizes
• Cell differentiation usually poor

Some Tumors Are Cancer, Others Are Not
Dysplasia
 Abnormal change in the size, shape, and organization of cells in a tissue
 Often an early step toward cancer
• Microscopic characteristics of cancer cells
• Behave differently from normal cells

Cancer Cells Are Abnormal in Their
Growth and Appearance

Normal Moles Are Common Examples of
Benign Growths

Main Features of Benign and Malignant
Tumors

A Cancer Cell’s Structure Is Abnormal
 Cancer is a result of a series of mutations in the cell’s genes
• Larger cell nucleus and less cytoplasm
• Loss of structural specialization
• Cytoskeleton shrinks
• Plasma membrane proteins could be lost or altered
• New plasma membrane proteins may appear
• Changes passed on to cell’s descendants

Cancer Cells Also Do Not Divide Normally
 Cancer cells don’t necessarily divide faster than normal cells; more cancer cells are dividing than dying
 Cancer cells do not respond to crowding; loss of contact inhibition
• Leads to a disorganized mass; cells may have extensions
• May produce HCG and angiogenin
• Metastasis: makes a cancer malignant

Threadlike “False Feet” Are a Common
Feature of Cancerous Cells

Cancer Spreads Step-by-Step

Cancer is a Genetic Disease
 Cancer is a genetic disease that develops in a predictable sequence of steps
 Carcinogenesis
• Transformation of a normal cell into a cancerous cell
• Step-by-step transformation

Carcinogenesis Occurs in Predictable Steps

A Common Type of Colorectal Cancer
May Develop by These Steps

Colon cancer results from genetic alterations in multiple genes
Inherited mutations in the APC gene dramatically increase risk of colon cancer

Cancer Usually Involves Several Genes
 Proto-oncogenes
• In normal cells
• Code for proteins involved in the stimulus of cell division
• If altered, may form oncogenes
• Alone, do not cause malignant cancer
• Require other mutations, including one in a tumor suppressor gene

Cancer Usually Involves Several Genes
 Tumor suppressor genes
• Stop cell growth and division; prevent cancer formation
• May prevent expression of oncogenes

Types of cancer genes
Type of gene
Oncogene
Normal function
Promotes division
Mutated function
Promotes division
- abnormal time or cell type
Types of proteins
Growth factors
Tumor suppressor gene
Suppresses cell division
Fails to suppress division
Checkpoint molecules
DNA repair gene mutation
Repair DNA mutations
Fail to repair DNA mutations
Enzymes for mismatch or excision repair

Other Factors Also May Lead to Cancer
 Inherited susceptibility to cancer
• ~5% of cancers
 Viruses
• Viral DNA may be inserted into a host cell’s DNA
• May switch on a proto-oncogene
• May carry oncogenes

Other Factors Also May Lead to Cancer
 Chemical carcinogens
• Carcinogens: cancer-causing substances that can lead to a mutation in DNA
• Asbestos, vinyl chloride, and benzene
• Hydrocarbons in cigarette smoke
• Aflatoxin: fungal product
 Radiation
• UV from the sun and tanning lamps
• X-rays: medical and dental
• Radon, cosmic rays, and gamma radiation

Cruciferous vegetables can lower cancer risk

Other Factors Also May Lead to Cancer
 Breakdowns in immunity
• Healthy immune system can target and destroy cancer cells
• When cancer cells have altered proteins at its surface, cells are not destroyed
• Risk of cancer increases:
• With age
• When an immune system has been suppressed for a long time
• HIV infection
• Immunosuppressant drugs
• Anxiety and depression

Focus on Environment: Cancer Risk from
Environmental Chemicals
 Exposure to pesticides
• Agricultural chemicals in food and airborne chemicals due to spraying programs
• Reduce exposure; how?
 Industrial chemicals
 Ames test
• Assess chemical’s ability to cause mutations

Some Industrial Chemicals Linked to
Cancer

Some Major Types of Cancer
 In general, a cancer is named according to the type of tissue in which it first forms
 Sarcomas: cancer of connective tissue
 Carcinomas: cancer arising from epithelium
 Lymphomas: cancer of lymphoid tissue
 Leukemias: cancer of stem cells
 Gliomas: cancer of brain glial cells

Cancer Is Named for the Site in the Body
Where It First Develops

In the U.S., More than 1 Million People
Are Diagnosed with Cancer Each Year

Cancer Screening and Diagnosis
 Early and accurate diagnosis of cancer is important to maximize the chances that a cancer can be cured

Blood Tests Can Detect Chemical
Indications of Cancer
 Tumor markers
• Produced by particular types of cancer cells
• Produced by certain cells in response to cancer
• Detected by blood tests
• HCG
• PSA: prostate-specific antigen

Medical Imaging Can Reveal the Site and
Size of Tumors
 Medical imaging
• MRI (magnetic resonance imaging): reveals tumors obscured by bone
• X-rays
• Ultrasound
• CT (computerized tomography)

Medical Imaging Can Reveal the Site and
Size of Tumors
 Radioactive tracers
• Tracked using a PET scanner
• Diagnosis of thyroid cancer using radioactive iodine
 Radioactively labeled monoclonal antibodies
• Useful in the location and size of certain tumors in the colon, brain, and bone
 DNA probe: locates mutated genes, e.g., p53

Radioactive Tracers Also Can Reveal
Cancer Tumors

Biopsy Is the Only Sure Way to Diagnose
Cancer
 Biopsy
• Removal and microscopic examination of tissue
 Seven common cancer signs: CAUTION

Light Microscope Image Shows
Cancerous Cells in Breast Tissue

Cancer Treatment and Prevention
 When a person is diagnosed with cancer, a variety of weapons are available to combat it
 Chemotherapy drugs
 Radiation therapy
 Surgery

Chemotherapy and Radiation Kill Cancer
Cells
 Chemotherapy
• Drugs used to kill cancer cells; disrupt some aspect of cell division
• Toxic to healthy cells; hair, bone marrow, lymphocytes, and epithelial cells of intestinal lining
• Side effects include hair loss, nausea, vomiting, and reduced immune responses
• Genetic approach to chemo in the future

Chemotherapy and Radiation Kill Cancer
Cells
 Radiation therapy
• Used when cancer is small or has not spread
• Radioisotopes used, e.g., Ra-226 and Co-60
 Chemotherapy and radiation destroy healthy cells
 More precise treatments
• Monoclonal antibody treatment
• Interferon treatment; limited at present

Good Lifestyle Choices Can Limit
Cancer Risk
 Avoid tobacco completely
 Maintain a desirable weight; eat a low-fat diet with plenty of fruits and vegetables
 Drink alcohol in moderation
 Make sure your living and work environment is safe from carcinogens
 Protect your skin from the sun’s UV rays

This Cancer Cell Is Surrounded by White
Blood Cells

Cancer Causes and Contributing Factors

Types of Cancer
• Skin Cancer
• Colon Cancer
• Prostate Cancer
• Lung Cancer
• Liver Cancer
• Brest Cancer
• Bladder Cancer